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Aim: Recent trends in comparative animal and human research inform us that collaborative research plays a key role in deciphering and solving cancer challenges. Globally, cancer is a devastating diagnosis with an increasing burden in both humans and dogs and ranks as the number three killer among humans in Kenya. This study aimed to provide comparative information on cancers affecting humans and dogs in Nairobi, Kenya. Materials and Methods: Dog data collection was by cancer case finding from five veterinary clinics and two diagnostic laboratories, whereas the human dataset was from the Nairobi Cancer Registry covering the period 2002-2012. The analysis was achieved using IBM SPSS Statistics® from the Kenya National Census, whereas the dog population was estimated from the human using a human:dog ratio of 4.1:1. Results: A total of 15,558 human and 367 dog cancer cases were identified. In humans, females had higher cancer cases 8993 (an age-standardized rate of 179.3 per 100,000) compared to 6565 in males (122.1 per 100,000). This order was reversed in dogs where males had higher cases 198 (14.9 per 100,000) compared to 169 (17.5 per 100,000) in females. The incident cancer cases increased over the 11-year study period in both species. Common cancers affecting both humans and dogs were: Prostate (30.4, 0.8), the respiratory tract (8.3, 1.3), lymphoma (5.6, 1.4), and liver and biliary tract (6.3, 0.5), whereas, in females, they were: Breast (44.5, 3.6), lip, oral cavity, and pharynx (8.8, 0.6), liver and biliary tract (6.5, 1.2), and lymphoma (6.0, 0.6), respectively, per 100,000. Conclusion: The commonality of some of the cancers in both humans and dogs fortifies that it may be possible to use dogs as models and sentinels in studying human cancers in Kenya and Africa. We further infer that developing joint animal-human cancer registries and integrated cancer surveillance systems may lead to accelerated detection of the risks of cancer in Africa.
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International Journal of One Health
Available at www.onehealthjournal.org/Vol.2/8.pdf
International Journal of One Health, EISSN: 2455-8931 42
RESEARCH ARTICLE
Open Access
One Health and cancer: A comparative study of human and canine
cancers in Nairobi
Nyariaro Kelvin Momanyi1,3, Rugutt Anne Korir2 and Riungu Erastus Mutiga1
1. Department of Clinical Studies, Faculty of Veterinary Medicine, University of Nairobi, Kenya; 2. Cancer Registry Unit,
Centre for Clinical Research, Kenya Medical Research Institute, Kenya; 3. Royal (Dick) School of Veterinary Studies and
The Roslin Institute, University of Edinburgh, Roslin, UK.
Corresponding author: Nyariaro Kelvin Momanyi, e-mail: momanyink@gmail.com,
RAK: annkorir@yahoo.com, REM: mutigar@yahoo.com
Received: 06-07-2016, Accepted: 21-10-2016, Published online: 19-11-2016
doi: 10.14202/IJOH.2016.42-57 How to cite this article: Momanyi NK, Korir RA, Mutiga RE. One Health and cancer:
A comparative study of human and canine cancers in Nairobi. Int J One Health 2016;2:42-57.
Abstract
Aim: Recent trends in comparative animal and human research inform us that collaborative research plays a key role in
deciphering and solving cancer challenges. Globally, cancer is a devastating diagnosis with an increasing burden in both
humans and dogs and ranks as the number three killer among humans in Kenya. This study aimed to provide comparative
information on cancers affecting humans and dogs in Nairobi, Kenya.
Materials and Methods: Dog data collection was by cancer case finding from five veterinary clinics and two diagnostic
laboratories, whereas the human dataset was from the Nairobi Cancer Registry covering the period 2002-2012. The analysis
was achieved using IBM SPSS Statistics® v.20 (Dog data) and CanReg5 (human data). The human population was estimated
from the Kenya National Census, whereas the dog population was estimated from the human using a human:dog ratio of
4.1:1.
Results: A total of 15,558 human and 367 dog cancer cases were identified. In humans, females had higher cancer cases
8993 (an age-standardized rate of 179.3 per 100,000) compared to 6565 in males (122.1 per 100,000). This order was
reversed in dogs where males had higher cases 198 (14.9 per 100,000) compared to 169 (17.5 per 100,000) in females. The
incident cancer cases increased over the 11-year study period in both species. Common cancers affecting both humans and
dogs were: Prostate (30.4, 0.8), the respiratory tract (8.3, 1.3), lymphoma (5.6, 1.4), and liver and biliary tract (6.3, 0.5),
whereas, in females, they were: Breast (44.5, 3.6), lip, oral cavity, and pharynx (8.8, 0.6), liver and biliary tract (6.5, 1.2),
and lymphoma (6.0, 0.6), respectively, per 100,000.
Conclusion: The commonality of some of the cancers in both humans and dogs fortifies that it may be possible to use dogs
as models and sentinels in studying human cancers in Kenya and Africa. We further infer that developing joint animal-
human cancer registries and integrated cancer surveillance systems may lead to accelerated detection of the risks of cancer
in Africa.
Keywords: Africa, cancer, cancer registry, comparative oncology, Kenya, Nairobi, One Health.
Introduction
One Health and cancer
The study of cancer through comparative oncol-
ogy, in recent times, has provided invaluable insights
on how the pet-dog is not only man’s companion but
also plays an integral role in improving human health
and well-being [1,2]. More importantly, reiterating the
added value of One Health [3] by acting or having the
potential to act as sentinels (early warning systems)
and models for studying, early diagnosis and treatment
of human cancer and possibly other animals as well.
Cancer registries
Cancer registries play an important role of facil-
itating early detection, prevention, treatment, and care
of cancer patients. In Kenya, there are two human
population-based cancer registries: Geographical
positioned in Nairobi and Eldoret counties, three hos-
pital-based registries, and three other registries are in
their early stages of development. On 10th February
2016, the Kenya National Cancer Registry Programme
was launched [4]. However, there is no animal cancer
registry in the country.
The burden of cancer
Worldwide, cancer continues to torment man [5]
and dog [6-8] alike, with the global burden increasing
in both species. Cancer is among the four noncommu-
nicable diseases (NCDs) responsible for 82% deaths
attributable to NCDs, with three quarters of these
occurring in low- and middle-income countries [9].
In Kenya, cancer ranks as the number three cause
of mortality among humans, after infectious diseases
and cardiovascular diseases, with the number of can-
cer cases projected to nearly double by 2030 [10].
This has and will continue to escalate the “double bur-
den” of disease, with an accompanying dual effect of
not only straining existing health-care systems [5,10]
Copyright: Momanyi, et al. This article is an open access article
distributed under the terms of the Creative Commons Attribution
4.0 International License (http://creativecommons.org/licenses/
by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit
to the original author(s) and the source, provide a link to the
Creative Commons license, and indicate if changes were made.
The Creative Commons Public Domain Dedication waiver (http://
creativecommons.org/ publicdomain/zero/1.0/) applies to the data
made available in this article, unless otherwise stated.
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International Journal of One Health, EISSN: 2455-8931 43
but also causing loss of income to already poor fam-
ilies and posing cumulative economic losses. The
challenge of addressing cancer in Kenya has been
attributed to several technical, economic, infrastruc-
tural, and social factors [11]. The burden of cancer
among animals, in this case pet-dogs, is unknown in
this study setting; but, there is a general observation
from the practicing clinicians that cancer cases among
pet-dogs are on the rise.
Are dogs’ better models and sentinels for human
cancers?
The dog is of special interest compared to other
laboratory [12] and domestic animals in studying
human cancer because: It naturally and increasingly
develops spontaneous cancer similar to humans [7],
which could be as a result of the increasing “human-
dog bond” which increases their exposure to simi-
lar risk factors and environmental carcinogens [13].
Moreover, the dog is phylogenetically closely related
to man [14]; this is supported by the fact that approxi-
mately all the 19,000 genes identified in the dog match
to a similar gene in the human genome [15].
Several studies have documented that pet-dogs
respond to a number of environmental carcinogens,
similar to the way humans do [16-20]. For instance,
the association between industrial activity and conse-
quent bladder cancer has been established [17], with
the dog having a shorter latent period of bladder cancer
(10 years), as compared to man (20 years) [14]. Thus,
humans and dogs do develop similar cancers when
exposed to similar risk factors or carcinogens, and
by inference, monitoring the health of pet-dogs (and
potentially other animals as well) will aid early identi-
fication and correlation between exposure to environ-
mental contaminants and cancer in humans [21].
The aim of the study
In Kenya, the comparative aspect of studying can-
cers in humans and animals at the same time has not
been explored. There also lacks a system for collecting
population data on animal cancers similar to the human
cancer registries. The objective of the study was, there-
fore, to determine the most common cancers affecting
humans and dogs by age and gender in Nairobi area
so as to determine the potential of using dogs as mod-
els and sentinels for human cancers. We presume the
results to catalyze future research ventures for compar-
ison with other populations within and elsewhere and
to complement the current national and global efforts
geared toward cancer prevention and control.
Materials and Methods
Ethical clearance and approval
Approval and an introductory letter seeking per-
mission to access data from the human cancer registry,
veterinary clinics, and laboratories was issued by the
Faculty of Veterinary Medicine, University of Nairobi
dated 24th January 2013. For the human data, being
secondary data, the corresponding scientific and ethi-
cal approvals are described [22, 23].
Study area
Nairobi County is the primary capital city of
Kenya with a population of 3,138,369 (1,605,230
males and 1,533,139 females) based on the 2009
census [24]. It has a fairly good representation of the
population and ethnic groups in Kenya. Pet animal
population and structure are not available for Nairobi
County, but it is home to a large number of veterinary
practices and with the highest population of dogs kept
as pet-dogs.
Human data methodology
The human data methodologies detailing on data
collection, data variables, sources of information,
data management, computer applications, coding, and
classification have been described in an earlier report
of 2006 by the Kenya Medical Research Institute [22]
and a recent publication by Korir et al. [23]. The fol-
lowing sections will dwell on the dog methodologies.
Tumor data sources
Dog datasets were actively extracted from seven
institutions within Nairobi County, of which five were
veterinary clinics and two were reference veterinary
diagnostic laboratories. The dataset comprised five
sets of diagnostic records from necropsy/postmortem,
laboratory (cytology and histology), clinical inves-
tigation (radiography), medical records, and index
cards mentioning cancer as the contributory cause of
morbidity or mortality, spanning from the year 2002
to 2012. However, only one veterinary clinic had a
computer-based disease index system. In all cases, the
clinic and laboratory personnel were involved to pro-
vide the required information.
Data variables
Dog data were keyed into a preconfigured
Microsoft Access 2013® database with the number
of assessment variables used based on the standards
provided by the International Agency for Research
on Cancer as outlined by MacLennan [25] but with
modifications to fit the veterinary case records and
for comparison with the human records. The variables
included were: The patient details (Unique ID, breed,
sex, and age), the tumor details (date of diagnosis,
entered as year only), the basis of diagnosis, topog-
raphy (first occurrence only), morphology (based
on histology/cytology), the source of information
(entered as name of clinic), mode of treatment, and
patient status (entered as alive or dead, as at date of
data extraction).
Data preparation
Dog datasets were exported from the Microsoft
Access 2013® database into IBM SPSS v20. Before
exporting each data, variable was coded separately
(Table-1).
Data collection
Human and dog data collection was by desk
review through scheduled visits to veterinary clinics,
laboratories, and the human cancer registry between
Available at www.onehealthjournal.org/Vol.2/8.pdf
International Journal of One Health, EISSN: 2455-8931 44
August 2013 and April 2014. The dog data were
entered directly into the preconfigured Microsoft
Access 2013® database, whereas the human data were
retrieved and downloaded from the Canreg5 database
as a tab-separated values file format.
Population data
Human annual intercensal estimates were pro-
jected using annual growth rates for the 5-year age
group and for each gender based on 1999 [26] and
2009 [24] census data for Nairobi County (Table-2).
Since the Nairobi County dog population and struc-
ture is not known, the corresponding total dog popu-
lation at each 5-year age group was calculated using
the ratio of humans to dogs as 4.1:1 [27]. The corre-
sponding dog numbers for each gender were calcu-
lated using the dog male:female ratio of 1.4:1 [27].
Based on the 11-year (2002-2012) population esti-
mates, the calculated Nairobi County annual average
human population was 2,991,704 (1,506,182 males
and 1,406,159 females) and the dogs as
729,605 (425,603 males, 304,002 females) are
shown in Figure-1 for the human and dog population
pyramids.
Data analysis
Results are presented as the number of cancer
cases registered, crude, and age-standardized inci-
dence rates, for the study period (2002-2012). The
crude, all ages rate per 100,000 was calculated by
dividing the total number of cases per site by the total
number of person/dog-years of observation and multi-
plying the result by 100,000. The age-specific rate for
each age group was calculated as a rate per 100,000 by
dividing the number of cases in the age group by the
corresponding person/dog-years of observation and
multiplying the result by 100,000.
Age-standardized rates (ASRs) per 100,000
were calculated by the direct method using the World
Standard Population (for human) and using a known
and published age structure for the dog [28] as an
external standard but with modifications to fit study
age groupings (Table-3). The cancer cases of unknown
age were further included in the determination of ASR
by multiplying with a correction factor. 95% confi-
dence intervals for the ASR were also calculated. All
calculations described above were done as per guide-
lines by Boyle and Parkin [29].
Results
Dog and human datasets
During the 11-year period (2002-2012) under
review, a total of 15,558 human cancer cases (age-stan-
dardized incidence rate of 137.4 per 100,000) were
retrieved from the human cancer CanReg5 database,
consisting of 6565 (42.2%) male (ASR of 122.1 per
100,000) and 8993 (57.8%) female cancer cases (ASR
of 179.3 per 100,000). In dogs, 367 cancer cases
(ASR of 16.0 per 100,000) were retrieved, of which
198 (54.0%) were males (ASR of 14.9 per 100,000)
and 169 (46.0%) female cancer cases (ASR of 17.5
per 100,000) shown in Table-4 for a detailed record of
the ASRs for each topographical site and species and
their corresponding 95% confidence intervals.
Trend of cancer cases
The number of cancer cases increased progres-
sively over the study period in both humans and dogs
as shown in Figure-2. Whereas this was generally
true, the spontaneous decrease in the number of inci-
dent cases was observed in the years 2007 and 2009 in
both humans and dogs.
Incidence of the top 10 cancers by topography affect-
ing both humans and dogs
The common cancers affecting both male humans
and dogs (among the top 10 cancers) were: Prostate
(ASR of 30.4, 0.8 per 100,000), respiratory tract (ASR
of 8.3, 1.3 per 100,000), lymphoma (ASR of 5.6, 1.4
per 100,000), and liver and biliary tract (ASR of 6.3,
Table-1: Dog dataset as coded in IBM SPSS v. 20.
Variable name Type Measure Label Values
Unique ID Numeric Scale Unique patient identifier Incremental by 1 from 1000
Breed String Nominal Breed of dog Based on the 22 breeds of dogs
identified (coded 00-21, 99)
Sex Numeric Scale Sex of dog 0=Male, 1=Female
Age Numeric Scale Age of dog Value entered as recorded
Status Numeric Nominal Status of dog on data abstraction 0=Dead, 1=Alive, 9=Unknown
Incidence Date Scale Date of first registration of case Value entered as recorded
Topography String Nominal 3-digit code of the tumor site Values coded based on the online
ICD-0-3 [57] and data available
Morphology Numeric Nominal 4-digit code of the tumor morphology Values coded based on the online
ICD-0-3 [57] and data available
Behavior Numeric Nominal Behavior of tumor 0=Benign, 1=Uncertain, 2=In situ,
3=Malignant
Diagnosis Numeric Nominal Basis of diagnosis of tumor 0=Necropsy, 1=Clinical only, 2=Clinical
investigation, 3=Surgery/Autopsy,
4=Laboratory tests, 5=Cytology,
6=Histology primary
Treatment Numeric Nominal Mode of treatment 0=Medical only, 1=Surgery, 2=None,
3=Unknown, 4=Euthanasia
Facility Numeric Nominal The source name of data Each facility coded individually 0-6
Available at www.onehealthjournal.org/Vol.2/8.pdf
International Journal of One Health, EISSN: 2455-8931 45
1.2 per 100,000), and lymphoma (ASR of 6.0, 0.6 per
100,000), respectively (Figure-3).
Cancer cases and age-specific incidence per age
group in humans and dogs
The number of cancer cases and age-specific
rates per 100,000 in both humans and dogs generally
increased with advancing age. The highest number of
cancer cases affected humans of 40-44 age-group (but
the highest age-specific rate was at 70-74 age group),
whereas, in dogs, the highest cancer cases affected
the 11-12 age-group (but the highest age-specific rate
was at 15+ age group). By gender, most cancer cases
in female humans and dogs were recorded in (40-44;
11-12) and (75+; 11-12) age groups, respectively,
whereas, in male, humans and dogs they were recorded
in (75+; 15+) age-groups, respectively (Table-5).
Breed and cancer distribution
The dataset included 23 different dog breeds
(Supplementary Material-1). Of the 23.7% cross-
breeds, 6.9% were between a German Shepherd Dog
(GSD) and another known breed, 10.3% were crosses
of other known breeds, and 82.8% were crosses
of other unknown/unrecorded breeds, simply indi-
cated as “cross” in the records. It was evident that
Table-2: Annual growth rates for the 5-year age group
and for each gender.
Age group Annual growth rates
Male (%) Females (%)
0-4 4.1 4.0
5-9 4.8 4.7
10-14 4.1 3.4
15-19 2.3 2.1
20-24 2.1 4.4
25-29 2.9 5.2
30-34 3.7 5.8
35-39 4.0 5.6
40-44 3.9 5.7
45-49 4.2 6.2
50-54 2.8 5.3
55-59 5.4 7.0
60-64 5.3 6.2
65-69 4.2 5.4
70-74 2.9 3.4
75+ 2.5 4.7
Table-3: Deriving the dog standard population using a known standard population published by Thrusfield [28].
Age
interval
(years)a
MalebFemalecTotald%
Malee
%
Femalef
%
Totalg
MalehFemaleiTotaljAge
classk
Dog
standard
populationl
<1 378,000 365,000 743,000 12 12 11.6 11,732 11,521 11,628 0-2 mo 2907
<1-2 433,000 365,000 798,000 13 12 12.5 13,439 11,521 12,488 3-5 mo 2907
<2-3 378,000 365,000 743,000 12 12 11.6 11,732 11,521 11,628 6-8 mo 2907
<3-4 287,000 320,000 607,000 9 10 9.5 8908 10,101 9499 9-11 mo 2907
<4-5 287,000 279,000 566,000 9 9 8.9 8908 8807 8858 1-2 12,488
<5-6 239,000 238,000 477,000 7 8 7.5 7418 7513 7465 3 11,628
<6-8 416,000 447,000 863,000 13 14 13.5 12,911 14,110 13,505 4 9499
<8-10 323,000 323,000 646,000 10 10 10.1 10,025 10,196 10,110 5 8858
<10-12 220,000 244,000 464,000 7 8 7.3 6828 7702 7261 6-7 7465
<12-14 174,000 152,000 326,000 5 5 5.1 5400 4798 5102 8 13,505
>14 87,000 70,000 157,000 3 2 2.5 2700 2210 2457 9 5055
3,222,000 3,168,000 6,390,000 100 100 100.0 100,000 100,000 100,000 10 5055
11-12 7261
13 5102
14 1228
15+ 1228
Total 100,000
aAge intervals as described by Thrusfield [28], bNumber of males per age intervals as described by Thrusfield [28],
cNumber of females per age intervals as described by Thrusfield [28], dTotal number of dogs per age intervals as
described by Thrusfield [28], eCalculated % = Number of males in class interval divided by total number of males
multiplied by 100, fCalculated % = Number of females in class interval divided by total number of females multiplied
by 100, gCalculated % = Total number of dogs in class interval divided by summed total number of dogs multiplied by
100, hWeighted number for male dogs = Value in column (b) multiplied value in column (e) for each class, iWeighted
number for male dogs = Value in column (c) multiplied value in column (i) for each class, jWeighted number for male
dogs = Value in column (d) multiplied value in column (g) for each class, kThe 16 age groupings as per the current study
to be comparable to the human 16 age groupings, lEqually distributed from the values in column (j) and in reference to
the age intervals in column (a)
0.5 per 100,000), respectively. The common cancers
affecting both female humans and dogs (among the
top 10 cancers) were: Breast (ASR of 44.5, 3.6 per
100,000), lip, oral cavity, and pharynx (ASR of 8.8,
0.6 per 100,000), liver and biliary tract (ASR of 6.5,
Available at www.onehealthjournal.org/Vol.2/8.pdf
International Journal of One Health, EISSN: 2455-8931 46
common cancers affecting the top breeds in Nairobi
were breast and skin cancers, of which they affected
at a higher proportion, the German shepherd breed
(breast - 3.0%), and the crossbreeds (skin - 2.2%).
The distribution of the most common morphological
diagnoses and staging
The common individual morphological
diagnoses in humans and dogs were neoplasm,
malignant-8000 (14.3%, 44.4%), squamous cell car-
cinoma, NOS-8070 (19.5%, 6.5%), adenocarcinoma,
NOS-8140 (13.8%, 4.6%), and malignant lymphoma,
NOS-9591 (1.3%, 8.4%), respectively (Figure-4).
The staging distribution of human cancers
was as follows: Unknown stage (88.7%), Stage III
(2.5%), Stage IV (2.3%), Stage II (2.1%), and Stage I
(0.9%), excluding the invalid codes (3.6%), whereas,
Figure-1: Composition by sex and 5-year age group of the average population for humans and dogs in Nairobi, (2002-2012).
Available at www.onehealthjournal.org/Vol.2/8.pdf
International Journal of One Health, EISSN: 2455-8931 47
Table-4: ASRs (at 95% CI) for humans and dogs by gender and topography/site in Nairobi, 2002-2012.
Name ICD
(10th)
Male humans Female humans Male dogs Female dogs
No.
cases (%)
Crude ASR
(95% CI)
No.
cases (%)
Crude ASR (95% CI) No. cases
(%)
Crude ASR (95% CI) No. cases
(%)
Crude ASR
(95% CI)
Lip, oral
cavity and
pharynx
C00-14 742 (11.3) 4.8 11.6 (6.7-16.6) 416 (4.6) 2.7 8.8 (7.9-9.7) 3 (1.5) 0.1 0.0 6 (3.6) 0.2 0.6 (0.4-0.9)
Esophagus C15 592 (9.0) 3.8 12.2 (6.3-18.2) 415 (4.6) 2.7 11.5 (10.3-12.6) 1 (0.5) 0.0 0.1 (0.2-0.4) 1 (0.6) 0.0 0.0
Stomach C16 406 (6.2) 2.6 8.2 (3.5-12.9) 305 (3.4) 2.0 8.0 (7.1-8.9) 0 (0.0) 0.0 0.0 0 (0.0) 0.0 0.0
Small
intestine
C17 12 (0.2) 0.1 0.3 (0.4-0.9) 6 (0.1) 0.0 0.1 (0.0-0.1) 0 (0.0) 0.0 0.0 0 (0.0) 0.0 0.0
Colon C18 303 (4.6) 2.0 5.6 (1.9-9.3) 253 (2.8) 1.6 5.9 (5.2-6.7) 0 (0.0) 0.0 0.0 0 (0.0) 0.0 0.0
Rectum C19-20 207 (3.2) 1.3 4.0 (0.6-7.5) 163 (1.8) 1.1 3.4 (2.8-3.9) 1 (0.5) 0.0 0.0 0 (0.0) 0.0 0.0
Anus C21 11 (0.2) 0.1 0.2 (0.6-1.0) 19 (0.2) 0.1 0.5 (0.3-0.7) 9 (4.5) 0.2 1.7 (1.2-2.2) 4 (2.4) 0.1 0.3 (0.1-0.7)
Liver and
biliary tract
C22-24 351 (5.3) 2.3 6.3 (2.2-10.4) 273 (3.0) 1.8 6.5 (5.7-7.3) 12 (6.1) 0.3 0.5 (0.4-0.7) 12 (7.1) 0.4 1.2 (0.5-2.0)
Pancreas C25 126 (1.9) 0.8 3.0 (0.1-5.9) 110 (1.2) 0.7 2.9 (2.3-3.4) 1 (0.5) 0.0 0.0 1 (0.6) 0.0 0.0
Intestinal
tract, part
unspecified
C26.0 0 (0.0) 0.0 0.0 0 (0.0) 0.0 0.0 2 (1.0) 0.0 0.0 (0.0-0.1) 1 (0.6) 0.0 0.6 (0.1-1.0)
Spleen C26.1 0 (0.0) 0.0 0.0 (0.0-0.0) 0 (0.0) 0.0 0.0 12 (6.1) 0.3 0.7 (0.5-0.9) 9 (5.3) 0.3 0.4 (0.0-08)
Respiratory
tract
C30-34 366 (5.6) 2.4 8.3 (3.5-13.1) 162 (1.8) 1.0 3.8 (3.2-4.4) 13 (6.6) 0.3 1.3 (1.0-1.6) 9 (5.3) 0.3 0.9 (0.3-1.5)
Others and
unspecified
thoracic
organs
C37-38 7 (0.1) 0.0 0.1 (0.4-0.6) 17 (0.2) 0.1 0.4 (0.2-0.6) 3 (1.5) 0.1 0.1 (0.0-0.2) 0 (0.0) 0.0 0.0
Bone C40-41 193 (2.9) 1.2 2.1 (0.3-3.9) 154 (1.7) 1.0 2.2 (1.7-2.6) 9 (4.5) 0.2 1.1 (0.7-1.6) 10 (5.9) 0.3 1.5 (0.9-2.2)
Skin C43-44 138 (2.1) 0.9 2.5 (0.1-5.1) 145 (1.6) 0.9 3.3 (2.8-3.9) 37 (18.7) 0.8 3.5 (2.8-4.2) 36 (21.3) 1.1 4.7 (3.4-6.0)
Mesothelioma C45 2 (0.0) 0.0 0.1 (0.3-0.4) 1 (0.0) 0.0 0.0 (0.0-0.1) 0 (0.0) 0.0 0.0 0 (0.0) 0.0 0.0
Kaposi
sarcoma
C46 319 (4.9) 2.1 2.6 (0.9-4.4) 163 (1.8) 1.1 1.4 (1.101.6) 0 (0.0) 0.0 0.0 0 (0.0) 0.0 0.0
Connective
and soft
tissue
C47, 49 113 (1.7) 0.7 1.0 (0.0-2.1) 106 (1.2) 0.7 1.5 (1.1-1.8) 19 (9.6) 0.4 0.3 (0.2-0.3) 9 (5.3) 0.3 0.1 (0.0-0.1)
Breast C50 97 (1.5) 0.6 1.9 (0.3-4.1) 2278 (25.3) 14.7 44.5 (42.7-46.4) 0 (0.0) 0.0 0.0 40 (23.7) 1.2 3.6 (2.9-4.3)
Vulva and
vagina
C51-52 0 (0.0) 0.0 0.0 (0.0-0.0) 70 (0.8) 0.5 1.4 (1.1-1.8) 0 (0.0) 0.0 0.0 13 (7.7) 0.4 0.6 (0.3-0.9)
Cervix uteri C53 0 (0.0) 0.0 0.0 (0.0-0.0) 1890 (21.0) 12.2 35.8 (34.1-37.5) 0 (0.0) 0.0 0.0 0 (0.0) 0.0 0.0
Others and
unspecified
part of uterus
C54-55 0 (0.0) 0.0 0.0 (0.0-0.0) 273 (3.0) 1.8 7.3 (6.508.2) 0 (0.0) 0.0 0.0 1 (0.6) 0.0 0.2 (0.0-0.3)
Ovary C56 0 (0.0) 0.0 0.0 (0.0-0.0) 298 (3.3) 1.9 6.5 (5.7-7.2) 0 (0.0) 0.0 0.0 0 (0.0) 0.0 0.0
Others and
unspecified
parts of
female
organs
C57-58 0 (0.0) 0.0 0.0 (0.0-0.0) 15 (0.2) 0.1 0.1 (0.0-0.2) 0 (0.0) 0.0 0.0 0 (0.0) 0.0 0.0
(Contd...)
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International Journal of One Health, EISSN: 2455-8931 48
Table-4: Continued...
Name ICD
(10th)
Male humans Female humans Male dogs Female dogs
No.
cases (%)
Crude ASR
(95% CI)
No.
cases (%)
Crude ASR (95% CI) No. cases
(%)
Crude ASR (95% CI) No. cases
(%)
Crude ASR
(95% CI)
Penis C60 19 (0.3) 0.1 0.3 (0.5-1.1) 0 (0.0) 0.0 0.0 17 (8.6) 0.4 1.0 (0.5-1.4) 0 (0.0) 0.0 0.0
Prostate C61 1006 (15.3) 6.5 30.4 (19.9-41.0) 0 (0.0) 0.0 0.0 19 (9.6) 0.4 0.8 (0.3-1.3) 0 (0.0) 0.0 0.0
Testis C62 21 (0.3) 0.1 0.3 (0.7-1.2) 0 (0.0) 0.0 0.0 7 (3.5) 0.1 0.5 (0.3-0.6) 0 (0.0) 0.0 0.0
Others and
unspecified
parts of male
organs
C63 6 (0.1) 0.0 0.1 (0.5-0.7) 0 (0.0) 0.0 0.0 2 (1.0) 0.0 0.4 (0.0-0.9) 0 (0.0) 0.0 0.0
Kidney, etc. C64-66 69 (1.1) 0.4 1.1 (0.6-2.8) 92 (1.0) 0.6 1.2 (0.9-1.4) 0 (0.0) 0.0 0.0 1 (0.6) 0.0 0.6 (0.1-1.0)
Bladder C67 113 (1.7) 0.7 2.9 (0.2-6.0) 52 (0.6) 0.3 1.3 (1.0-1.7) 2 (1.0) 0.0 0.4 (0.3-0.6) 1 (0.6) 0.0 0.1 (0.0-0.2)
Others and
unspecified
parts of
urinary
system
C65-66,
68
0 (0.0) 0.0 0.0 (0.0-0.0) 2 (0.0) 0.0 0.1 (0.0-0.1) 0 (0.0) 0.0 0.0 1 (0.6) 0.0 0.4 (0.2-0.6)
Eye C69 254 (3.9) 1.6 2.6 (0.6-4.6) 285 (3.2) 1.8 3.0 (2.6-3.4) 6 (3.0) 0.1 0.4 (0.1-0.7) 3 (1.8) 0.1 0.3 (0.4-1.1)
Brain,
nervous
system
C70-72 155 (2.4) 1.0 2.1 (0.2-4.0) 147 (1.6) 1.0 2.1 (1.7-2.6) 3 (1.5) 0.1 0.1 (0.1-0.2) 1 (0.6) 0.0 0.0
Endocrine
system
C73-75 37 (0.6) 0.2 0.5 (0.7-1.8) 135 (1.5) 0.9 2.6 (2.1-3.0) 0 (0.0) 0.0 0.0 0 (0.0) 0.0 0.0
Lymphoma C81-88,
C90
461 (7.0) 3.0 5.6 (2.6-8.7) 355 (3.9) 2.3 6.0 (5.3-6.7) 10 (5.1) 0.2 1.4 (1.0-1.9) 2 (1.2) 0.1 0.6 (0.2-1.0)
Leukemia C90-95 181 (2.8) 1.2 1.9 (0.1-3.8) 146 (1.6) 0.9 2.1 (1.7-2.5) 0 (0.0) 0.0 0.0 0 (0.0) 0.0 0.0
Other and
unspecified
O&U 258 (3.9) 1.7 4.1 (0.7-7.5) 247 (2.7) 1.6 5.3 (4.6-6.0) 10 (5.1) 0.2 0.4 (0.2-1.1) 8 (4.7) 0.2 0.8 (0.5-1.0)
All sites 6565 (100.0) 42.4 122.1 (103.8-140.4) 8993 (100.0) 58.1 179.3 (175.4-183.2) 198 (100.0) 4.2 14.9 (13.3-16.6) 169 (100.0) 5.1 17.5 (15.2-19.8)
ICD-O-[10th]=International Classification of Diseases for Oncology, 10th edition, No. cases=Total number of incident cases per site/topography, Crude=Crude rate per 100,000,
ASR=Age-standardized rate per 100,000, 95% CI=95% confidence interval given in brackets
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International Journal of One Health, EISSN: 2455-8931 49
in dogs, no staging was done on any of the morpho-
logical diagnoses. The proportional distribution of
diagnostic methods for the dog cancers were nec-
ropsy/post-mortem (41.7%), followed by clinical
only (25.3%), histology primary (14.7%), labora-
tory tests (9.0%), surgery/autopsy (8.4%), cytology
Figure-2: Trend of incident cancer cases in human and dogs in Nairobi (2002-2012).
Table-5: Number of cancer cases and age-specific rates per age group in humans and dogs.
Human
years
Dog years* Human (n=15,542)*** Dog (n=181)*** Event**
Male Female Total Male Female Total
0-4 0-2 months 129 (5.9) 115 (5.5) 244 (5.7) 0 (0.0) 0 (0.0) 0 (0.0)
5-9 3-5 months 135 (8.7) 73 (4.6) 208 (6.7) 0 (0.0) 0 (0.0) 0 (0.0)
10-14 6-9 months 139 (11.3) 99 (7.5) 238 (9.5) 0 (0.0) 0 (0.0) 0 (0.0) Puberty range in
most women and
bitches
15-19 10-11 months 166 (13.7) 135 (8.3) 301 (10.7) 0 (0.0) 0 (0.0) 0 (0.0)
20-24 1-2 204 (9.2) 238 (8.9) 442 (8.6) 3 (0.4) 6 (1.2) 9 (0.7)
25-29 3-4 241 (10.1) 422 (19.0) 663 (13.6) 3 (0.4) 1 (0.2) 4 (0.3)
30-34 4-5 347 (18.7) 685 (49.5) 1032 (30.3) 6 (1.2) 4 (1.2) 10 (1.2)
35-39 5-6 410 (30.2) 924 (98.9) 1334 (55.9) 5 (1.5) 5 (2.1) 10 (1.7)
40-44 6-7 560 (62.2) 1124 (199.6) 1684 (109.9) 12 (5.5) 5 (3.2) 17 (4.5) The start of
increased cancer
of all types in
both species
45-49 8-9 587 (88.2) 1082 (270.3) 1669 (148.6) 8 (5.0) 5 (4.4) 13 (4.7)
50-54 9-10 613 (142.6) 981 (399.6) 1594 (220.3) 4 (3.9) 8 (10.9) 12 (6.8)
55-59 10-11 546 (227.2) 851 (589.6) 1397 (349.2) 16 (28.1) 12 (29.5) 28 (28.7)
60-64 11-12 662 (441.8) 742 (753.3) 1404 (552.4) 23 (63.6) 15 (58.1) 38 (61.3)
65-69 13-14 571 (775.2) 542 (972.1) 1113 (837.2) 5 (26.4) 7 (51.8) 12 (37.0)
70-74 14-15 547 (1196.8) 448 (1038.0) 995 (1107.7) 4 (31.3) 2 (21.9) 6 (27.4)
75+ 15+ 702 (1178.6) 522 (680.8) 1224 (863.1) 8 (39.6) 14 (97.1) 22 (63.6) A reasonable
equivalent of
an upper age
extreme for both
species
*Age conversion using Lebeau [58] and the online access tool Available from: http://www.pedigree.com/all-things-dog/
dog-age-calculator/. **Events common to both species as described by Lebeau [58]. ***Only cases of known age are
included (values in brackets are the age-specific rates per 100,000)
(0.5%), and clinical investigation (0.3%). The data
quality indicators for the human records from the
Nairobi Cancer Registry showed that 98.5% of the
records were valid for analysis (excluding those with
unknown age), 83.6% were confirmed through lab-
oratory analysis, 15.6% diagnosed through clinical
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International Journal of One Health, EISSN: 2455-8931 50
Figure-3: Top 10 most common cancers in male and female humans and dogs in Nairobi (2002-2012).
Available at www.onehealthjournal.org/Vol.2/8.pdf
International Journal of One Health, EISSN: 2455-8931 51
investigation, and only 0.8% were diagnosed through
the certificate of death.
Discussion
Dataset and methods
The difference between the number of cancer
cases retrieved for the human dataset (n=15,558)
compared to dogs (n=367) could be explained by a
wider institutional coverage of the human dataset (27
facilities) [22] as compared to the canine data (7 facil-
ities). However, the dog and human data do provide
a comparative basis of certain cancer sites since they
take into account the size and characteristics of the
population at risk. Further, the human and dog data
collection did not only rely on pathology departments
but also traced clinically diagnosed cases.
Due to lack of dog population numbers for
Nairobi County, estimates were calculated using the
published human:dog ratio of 4.1:1 [27]. This ratio
4.1:1 was preferred since it represents an urban pop-
ulation setting that is comparable to the study popu-
lation, i.e., Kisumu and Nairobi are both urban cities
in Kenya. The lack of pet animal demographic data
is a common phenomenon across the entire country.
There is, therefore, need for the government of Kenya
to integrate small animals (dogs and cats) into the
National Census, which will also support other inter-
vention strategies such as rabies control that require
knowledge of the dog population. We further suggest
that developing a World Standard Population for dogs
could complement future comparative oncology stud-
ies, especially when it comes to comparing ASRs; this
is based on the fact that most studies that are published
and which we have referenced [13,30-32] (excluding
Dobson et al. [33]) that investigated cancer in dogs
and cats reported the percentage of cases rather than
ASRs. This, therefore, makes it difficult to compare
accurately the cancer incidence between different
populations [29].
Trend of cancer
The increasing number of cancer cases, with
advancing in age, in both humans and dogs in Nairobi
is consistent with reports on the occurrence of various
cancers from other parts of the world [34] and as also
reported by other studies in California-Davis [13], Italy-
Genoa [31], and in the UK [33]. The increasing number
of cancer cases could be attributed to: An actual increase
in cancer cases in both humans and dogs; an increase in
the population at risk of developing cancers; an increas-
ing proportion of facilities offering veterinary and
human medical [35] services, or an increased awareness
level and interest to undertake diagnostic and therapeu-
tic options for cancer [1]. Further, this increase can be
as a result of the changes taking place in Kenya such as
socioeconomic development, accessibility to regional
and international markets, demographic changes, and
rapid urbanization and modernization [35]. These fac-
tors result to an accelerated exposure to cancer risk fac-
tors such as lifestyle change, access to unhealthy foods
(high fat and high salt) and consumer products for both
human and dog populations.
It was not possible to explain why there was a
depressed number of cases in the year 2007 while, for
the year 2009, it could be attributable to the postelec-
tion chaos that could have resulted in a low attendance
to health facilities.
Cancer incidence by gender
The number of cancer cases in humans and dogs
was almost equally distributed in both genders, which
Figure-4: Common morphological diagnoses of cancer in humans and dogs in Nairobi (2002-2012).
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International Journal of One Health, EISSN: 2455-8931 52
contrast findings by Merlo et al. [31], who found a
3-fold higher incidence in females than male dogs.
The slightly higher cancer cases in human females
could be attributed to the higher mammary and cer-
vical cancers, at the same time the publicity for can-
cer screening among females in Nairobi may have
contributed to the higher frequency in the number of
cases, rather than the occurrence of cancer. Another
plausible reason could be that females have a higher
tendency of health-seeking behavior as compared to
males. The occurrence of a higher age-standardized
cancer rate among female dogs although their popula-
tion and cancer cases were lower as compared to male
dogs, could infer that female dogs could be having a
higher predisposition to cancer or the frequency of
cancer occurrence in females is higher as compared to
males. Future studies are needed to explain the causal
mechanisms for this phenomenon.
Age and cancer
The number of cancer cases in both humans
and dogs was clearly associated with age and also
as observed by Dobson et al. [33] in the UK, Merlo
et al. [31] in Italy, and the 2014 World Cancer
Report [34]. In humans, cancer cases peaked at the
40-44 age group in women and at 75+ age group in
men, which was a similar finding from the World
Cancer Report [34] in sub-Saharan Africa. In female
dogs, cancer cases peaked at the 11-12 age group and
the +15 age group in males, similar to findings by
Dobson et al., 2002 (>9 years) [33], Merlo et al., 2008
(>9-11 years) [31], and slightly with Grüntzig et al.,
2015 (between 5 and 10 years) [32].
It is significant to note that cancer peaks later
in both human and dog males as compared to the
females, this can possibly be explained by the earlier
age onset of breast and cervical cancers in females
and later age onset of prostate cancers in males [34].
It is also evident that dogs are frequently affected by
cancers between the age of >9 years similar to find-
ings by Dorn et al. [13], which is much earlier than in
man [14]. This may potentially facilitate the detection
of hazards and risk factors for cancer earlier in dogs
than in humans.
Breed predisposition to cancer
The overrepresentation of the GSD breed and
crossbreed is similar to findings by Grüntzig et al.,
2015 [32]; this finding could be because they are
common utility breeds and commonly used for secu-
rity purposes in most developing nations, Kenya
inclusive. The distribution of most of the cancers by
both topography and morphology was more related to
the number of cases reported than the dog breed, and
therefore, the effect of breed on the cancer cases in
this study was generally not clear, but the GSD was
differentially predisposed to the hemangiosarcoma
while the Labrador to the mast cell tumor, but this
could not conclusively be established as compared to
the study by Dobson et al. [36].
The most common cancers by topography in both
humans and in dogs
Despite the short period of study (2002-2012),
the data collected so far does show consistency and
specific contrasts with reports on the occurrence of
various cancers from other parts of the world [34],
Africa (Supplementary Material-2), and other dog
and comparative research studies (Supplementary
Material-3).
In this study, we have observed that there are
common cancers that affect both humans and dogs and
some disproportionately affecting a certain gender.
This does infer a possibility of common environmen-
tal carcinogens or risk factors. For example, liver can-
cers (probably as a result of aflatoxins [37], hepatitis B
and C infection [38,39] or indiscriminate alcohol con-
sumption [22,40]; respiratory cancers (probably due to
chronic smoking in humans [41], passive smoking and
other environmental exposures, e.g. diesel exhaust,
arsenic in water, etc., for both), lymphoma (as a result
of viral carcinogen [42], lifestyle charges and chem-
icals), and age/hormonal/lifestyle change/urbaniza-
tion [43] in case of prostate [44] and breast/mammary
gland cancers [45-47]. This does show a potential for
future studies (in Kenya or Africa) to use dogs as mod-
els to study prostate, breast/mammary gland, and lym-
phoma cancers and as sentinels for liver and respira-
tory cancers. Several studies have already shown this
possibility of using dogs as sentinels [16-20] and mod-
els [7,15] for studying human cancers.
Tumor diagnostic approaches
At the tumor level, the most common individ-
ual morphological tumor diagnosis in humans and
dogs were approximately as one would expect based
on estimates from previous studies in dogs [48] and
humans [34]. A commonality in both humans and dogs
in regard to morphological diagnosis and staging in
this study was the high number of ICD-O code 8000,
and the unknown staging (88.7%) in humans and with
no staging in dogs. In dogs, this could possibly be
explained by findings on diagnostic approaches, where
the detection and diagnosis of tumors vary according
to objective difficulties and methodologic difference
among veterinary clinics as also noted by Brønden
et al. [7]. Contrary, in humans, most of the diagnoses
are confirmed through laboratory techniques, which
is commendable. Irrespective of this, it is crucial to
remember that very few people in developing coun-
tries (including Kenya) can manage the cost of cancer
diagnosis (not mentioning treatment), and therefore,
this informs us that there are still many cancer cases
that are not captured or reported in this study. Future
studies should focus on bridging this gap to identify
the unreported cases through community-based cancer
studies, so as to determine the true burden of cancer.
In this study, most tumors in dogs were diag-
nosed at postmortem (41.7% of all cases) and clinical
only (25.3% of all cases), with laboratory methods
contributing (32.9% of all cases). The fact that most
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International Journal of One Health, EISSN: 2455-8931 53
cases were diagnosed as deceased shows that there is
a high mortality rate of canine patients diagnosed with
cancer although the causes of death may not be as a
result of these cancers. Cancer diagnosis involving a
combination of careful clinical assessment and diag-
nostic investigations is the first step to cancer manage-
ment, but in a developing country like Kenya most of
the cancer diagnostic methods are rare or limited and
also the cost involved is high, partly explaining the
diagnostic outcome.
Conclusion and Recommendations
An 11-year comparative study is relatively a short
period for comments on general trends for disease,
including cancer. However, despite the short period,
data collected so far does show a consistency and spe-
cific contrasts with reports on the occurrence of vari-
ous cancers from other parts of the world, region, and
other comparative research studies in both humans
and dogs. We would also like to highlight that cancer
registration is a difficult enterprise in Africa, faced by
a number of shortcomings making the distribution of
most cancer registries in Africa confined to the urban
populations, Mali [49], Guinea [38], Zimbabwe [50],
Ivory coast [51], Uganda [52], Malawi [53], except the
Gambia [54] that has a cancer registry with a national
coverage [54].
Perhaps the most important contribution that
this study makes is providing for the first time from
a developing nation, Kenya, comparative aspects of
cancers in dogs and humans in the same geographical
area. From the results, it is clear that more compara-
tive research adopting integrative and SMART One
Health approaches are required. Since many dogs in
Kenya and many parts of Africa share with humans
common environments and lifestyle and since can-
cer in both has a clinical and histological similarity,
the potential for using dogs as models and sentinels
is present. At the same time, dog breeding over time
has resulted in clear breed-predisposition to certain
cancer types. This implies both an excellent model
for genetic risk factors in cancer development and
also possibility to investigate protective genotypes as
well which, in fact, could explain higher and lesser
predisposition to respond to a certain environmental
carcinogen.
As we have noted in this study, dogs are fre-
quently affected by cancers at a much earlier time
than man similar to findings by Dorn et al. [13];
this may potentially facilitate detection of risks and
hazards earlier in dogs than humans. Future sentinel
studies should, therefore, be planned to assess this
possibility. This can only be achieved with well-es-
tablished “comparative” cancer registries that provide
accurate data to allow spatial identification of differ-
ences in low and high human and/or dog risk popu-
lations and thus providing clues into the etiology of
cancer. More importantly, there is need to strengthen
the existing human cancer registries since as of now
cancer is one of the primary objectives for African
governments [55]. There is need for the veterinary
surgeons and pathologists in Kenya to start thinking of
developing a cancer surveillance system which may
be integrated to the human cancer registry. We also
recommend and encourage that all cancer diagnoses,
especially staging of cancer in dogs, to be reported
using internationally standardized formats, which will
provide a strong basis for future comparative research.
However, there are still challenges that have to be
overcome, such as the stigma driven by traditional
beliefs which prevent people from seeking screening
and diagnosis and limited resources, especially the
crucial resource of knowledge.
In conclusion, we reiterate that Africa can win
the battle against cancer through collaborative public
health action through the One Health movement [56],
and through innovations and training in comparative
oncology research through complementary intra-Af-
rica and North-South collaborations.
Authors’ Contributions
NKM conducted the research and actively pre-
pared the manuscript. NKM and REM designed the
work. REM and RAK participated in the manuscript
preparation and advice during the research work. All
the authors read and approved the final manuscript.
Acknowledgments
The authors are most grateful to the institutions
which participated in this study by providing access to
data and for considerable assistance received from the
staff of the veterinary clinics and the Nairobi Cancer
Registry during the study. We also extend our sincere
appreciation to Dr. Neil Anderson from the Royal
(Dick) School of Veterinary Studies for his valuable
input and technical editing of the first draft of the
manuscript.
Competing Interests
The authors declare that they have no competing
interests.
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********
Supplementary Materials
Supplementary Material 1: Dog breed distribution in Nairobi (2002-2012).
Available at www.onehealthjournal.org/Vol.2/8.pdf
International Journal of One Health, EISSN: 2455-8931 56
Supplementary Material-2: Top five most common cancers in 10 human registries in Africa in terms of their incidence.
Rank CR*1 [1] CR*2 [1] CR*3 [1] CR* [1] CR*5 [1] CR*6 [2] CR*7 [3]
1 M: Liver
F: Cervix
M: Lung
F: Cervix
M: Liver
F: Cervix
M: Liver
F: Liver
M: Liver
F: Cervix
M: Liver
F: Cervix
M: Liver
F: Cervix
2 M: NHL
F: Breast
M: Liver
F: Liver
M: Prostate
F: Breast
M: Stomach
F: Cervix
M: Stomach
F: Liver
M: Prostate
F: Liver
M: Esophagus
F: Breast
3 M: Prostate
F: NHL
M: Prostate
F: Breast
M: Stomach
F: Liver
M: NHL
F: Breast
M: Bladder
F: Stomach
M: Stomach
F: Breast
M: Prostate
F: Liver
4 M: Stomach
F: Stomach
M: Bladder
F: Stomach
M: Bladder
F: Bladder and
colorectum
M: Prostate
F: Stomach
M: Lung
F: Breast
M: Lung
F: Stomach
M: Kaposi’s
sarcoma
F: Stomach
5 M: Leukemia
F: Liver AND
leukemia
M: Stomach
F: Bladder
M: Colorectum
F: NHL
M: Lung
F: NHL
M: Prostate
F: Bladder
M: Bladder
F: Ovary
M: Lung
F: Bladder
Rank CR*8 [3] CR*9 [4] CR*10 [5] CR*11 [6] CR*12 [7] CR*13 [8] CR*14 [9]
1 M: Kaposi’s
sarcoma
F: Cervix
M: Prostate
F: Cervix
M: Kaposi’s
sarcoma
F: Cervix
M: Liver
F: Cervix
M: Kaposi’s
sarcoma
F: Cervix
M: Prostate
F: Breast
M: Prostate
F: Breast
2 M: Liver
F: Breast
M: Liver
F: Breast
M: Prostate
F: Breast and
Kaposi’s
sarcoma
M: Lung
F: Liver
M: Esophagus
F: Kaposi’s
sarcoma
M: Esophagus
F: Cervix
M: Mouth
F: Cervix uteri
3 M: Prostate
F: Kaposi’s
sarcoma
M: Lung
F: Liver
M: Esophagus
F: Colorectum
M: Prostate
F: Breast
M: Prostate
F: Breast
M: Colorectal
F:Esophagus
M: Esophagus
F: Esophagus
4 M: Esophagus
F: Liver
M: Stomach
F: Stomach
M: Stomach
F: Liver
M: NHL
F: Corpus Uteri
M: Liver
F: NHL
M: Stomach
F: Colorectal
M: Stomach
F: Mouth
5 M: Lung
F: Stomach
M: NHL
F: Ovary
M: NHL
F: NHL
M: Stomach
F: Stomach
M: Bladder and
NHL
F: Thyroid
M: Oral cavity
F: Stomach
M: Respiratory
F: Stomach
CR*1=Ibadan, Nigeria 1960-69, CR*2=Bulawayo, Zimbabwe 1968-72, CR*3=Dakar, Senegal, 1969-74, CR*4=Gambia
1986-88, CR*5=Bamako, Mali 1987-88, CR*6=Guinea, Conakry 1992-95, CR*7=Harare, Zimbabwe 1990-92,
CR*8=Harare, Zimbabwe 1993-95, CR*9=Abidjan, Ivory Coast 1995-1997, CR*10=Kampala, Uganda 1995-1997,
CR*11=Gambia, 1988-97, CR*12=Blantyre, Malawi 1994-1998, CR*13=Nairobi, Kenya, 2004-2008. CR=Cancer registry,
NHL=Non-Hodgkin lymphoma, M=Male, F=Female
References
1. Bayo S, Parkin DM, Koumaré AK, Diallo AN, Ba T, Soumaré S, et al. Cancer in Mali, 1987-1988. Int J Cancer 1990;45:679-84.
2. Koulibaly M, Kabba IS, Cissé A, Diallo SB, Diallo MB, Keita N, et al. Cancer incidence in Conakry, Guinea: First results from the
cancer registry 1992-1995. Int J Cancer 1997;70:9-45.
3. Chokunonga E, Levy LM, Bassett MT, Mauchaza BG, Thomas DB, Parkin DM. Cancer incidence in the African population of
Harare, Zimbabwe: Second results from the cancer registry 1993-1995. Int J Cancer 2000;85:54-9.
4. Echimane AK, Ahnoux AA, Adoubi I, Hien S, M'Bra K, D'Horpock A, et al. Cancer incidence in Abidjan, ivory coast: First results
from the cancer registry, 1995-1997. Cancer 2000;89:653-63.
5. Wabinga HR, Parkin DM, Wabwire-Mangen F, Nambooze S. Trends in cancer incidence in Kyadondo County, Uganda, 1960-1997.
Br J Cancer 2000;82:1585-92.
6. Bah E, Parkin DM, Hall AJ, Jack AD, Whittle H. Cancer in the Gambia: 1988-1997. Br J Cancer 2001;84:1707-24.
7. Banda LT, Parkin DM, Dzamalala CP, Liomba NG. Cancer incidence in Blantyre, Malawi 1994-1998. Trop Med Int Health
2001;6:296-304.
8. Korir A, Okerosi N, Ronoh V, Mutuma G, Parkin M. Incidence of cancer in Nairobi, Kenya (2004-2008). Int J Cancer
2015;137:2053-9.
9. Forman D, Bray F, Brewster DH, Gombe C, Kohler B, Piñeros M, et al. Cancer Incidence in Five Continents. Vol. X. (Electronic
Version). Lyon: International Agency for Research on Cancer; 2013.
Available at www.onehealthjournal.org/Vol.2/8.pdf
International Journal of One Health, EISSN: 2455-8931 57
Supplementary Material-3: The top five most common cancers in six dog cancer registries in terms of percent of total
cases.
Rank CR*1 [1] CR*2 [2] CR*3 [3] CR*4 [4] CR*5 [5] CR*6
1 M: Skin
F: Mammary gland
M: Skin
F: Mammary
gland
Skin and soft
tissue
M: NHL
F: Mammary gland
Skin M: Skin
F: Skin
2 M: Connective
tissue
F: Skin
M: Testis
F: Oral cavity
Alimentary M: Skin
F: NHL
Mammary gland M: Anus
F: Breast
3 M: Testis
F: Connective
tissue
M: Oral cavity
F: Vagina/vulva
Mammary M: Male genital
organs
F: Connective and soft
tissue
Soft tissue M: Lymphoma
F: Bone
4 M: Mouth and
pharynx
F: Lymphosarcoma
M: Eye
F: Ovary
Urogenital M: Connective and
soft tissue
F: Skin
Gastrointestinal M: Respiratory
tract
F: Liver and biliary
tract
5 M: Lymphosarcoma
F: Mouth and
pharynx
M: Spleen
F: Eye
Lymphoid M: Lip, oral cavity,
and pharynx
F: Digestive organs
and peritoneum
Male sexual
organs
M: Bone
F: Respiratory
tract
CR*1=Alamada and Contra Costa, California 1963-1966, CR*2=Norwegian Canine Cancer Project, 1990-1998, CR*3=UK,
1997-1998, CR*4=Genoa, Italy, 1985-2002, CR*5: Switzerland, 1955-2008, CR*6: Nairobi, 2002-2012. CR=Cancer
registry, NHL=Non-Hodgkin lymphoma, M=Male, F=Female
References
1. Dorn CR, Taylor DO, Frye FL, Hibbard HH. Survey of animal neoplasms in Alameda and Contra Costa Counties, California. I.
Methodology and description of cases. J Natl Cancer Inst 1968;40:295-305.
2. Gamlem H, Nordstoga K, Glattre E. Canine neoplasia – Introductory paper. APMIS Suppl 2008;5-18.
3. Dobson JM, Samuel S, Milstein H, Rogers K, Wood JL. Canine neoplasia in the UK: Estimates of incidence rates from a population
of insured dogs. J Small Anim Pract 2002;43:240-6.
4. Merlo DF, Rossi L, Pellegrino C, Ceppi M, Cardellino U, Capurro C, et al. Cancer incidence in pet dogs: Findings of the Animal
Tumor Registry of Genoa, Italy. J Vet Intern Med 2008;22:976-84.
5. Gruntzig K, Graf R, Hässig M, Welle M, Meier D, Lott G, et al. The Swiss Canine cancer registry: A retrospective study on the
occurrence of tumours in dogs in Switzerland from 1955 to 2008. J Comp Pathol 2015;152(2-3):161-71.
... As dogs share indoor and outdoor environments with humans, they may be considered sentinels for environmental human hazards (Burrell and Seibert, 1914;Reif, 2011;Shan Neo and Tan, 2017). Furthermore, canine NHL occurs spontaneously in animals with biologically compressed lifespans allowing them to develop cancer more rapidly than humans (Shan Neo and Tan, 2017), thus providing an "early warning" for public health intervention (Reif, 2011), a crucial advantage of its surveillance (Gavazza et al., 2001;Takashima-Uebelhoer et al., 2012;Marconato et al., 2013;Zanini et al., 2013;Ito et al., 2014;Momanyi et al., 2016). For this reason, it is important to investigate possible geographical similarities and their relationship with human and canine lymphoma cases. ...
... Our study strengthens the value of comparative epidemiology to better understand human and animal cancer risks (Richards and Suter, 2015;Schiffman and Breen, 2015;Momanyi et al., 2016). There are many similarities between human and canine NHL (Teske, 1994;Marconato et al., 2013;Ito et al., 2014), two species that increasingly share common environments. ...
... In November 2019, The University of Queensland established the ACARCinom network, the first Australia-wide registry of animal cancers that will generate accessible datasets for identifying patterns and trends of cancers in animal using retrospective data from the Veterinary Laboratory Services (17). In Kenya, a collaborative work is ongoing with the human Kenya National Cancer Registry investigating cancers affecting humans and dogs in Nairobi (19). ...
... El que estas especies tengan similitudes en esta enfermedad, debiera hacer pensar a muchos que estudios integrados en cuanto causalidad o tratamientos debieran ser más abundantes a fin de lograr mayor eficiencia en la lucha contra el cáncer. Una estrategia para enfrentar este tema la da el estudio realizado en Nairobi, en donde luego de comparar y relacionar registros médicos de cáncer en humanos y animales sugieren que los perros podrían servir de centinelas por lo que tener sistemas integrados de vigilancia parece ser una buena opción (23). ...
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... El que estas especies tengan similitudes en esta enfermedad, debiera hacer pensar a muchos que estudios integrados en cuanto causalidad o tratamientos debieran ser más abundantes a fin de lograr mayor eficiencia en la lucha contra el cáncer. Una estrategia para enfrentar este tema la da el estudio realizado en Nairobi, en donde luego de comparar y relacionar registros médicos de cáncer en humanos y animales sugieren que los perros podrían servir de centinelas por lo que tener sistemas integrados de vigilancia parece ser una buena opción (23). ...
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RESUMEN/ABSTRAC "Una salud" es un concepto que lleva ya algún tiempo entre la comunidad científica, sin embargo, creo, aún no se logra su total comprensión y estamos lejos de su real aplicación, los temas sanitarios involucrados son muchos, pero la temática sobre zoonosis predomina casi totalmente, dejando de lado otras varias aplicaciones del concepto, como animales centinelas, violencia doméstica, obesidad y cáncer, entre otras, es importante entender que el concepto no es solo trabajar interdisciplinarmente, sino que lograr resultados sinérgicos más allá de la suma de cada disciplina en particular. "One Health" is a concept that has been around for some time among the scientific community, however, I think, it has not yet been fully understood and we are far from its real application, the health issues involved are many, but the topic of zoonosis predominates almost completely , leaving aside various other applications of the concept, such as sentinel animals, domestic violence, obesity and cancer, among others, it is important to understand that the concept is not only to work interdisciplinary, but to achieve synergistic results beyond the sum of each discipline in particular. INTRODUCCIÓN Desde que el concepto "ONE HEALTH" (OH) "UNA SALUD" fue enunciado ha ido evolucionando a la par con los avances científico tecnológicos, sin embargo sus fundamentos holísticos han ido perdiendo fuerza o se han ido difuminando, una de las consecuencias (o causa) de ello ha sido el excesivo protagonismo de las temáticas relacionadas con zoonosis, que, por lo llamativas y obvias, han opacado a todos las otras relaciones entre salud animal y salud humana, al realizar búsquedas en internet o en los eventos "One Health" predominan las temáticas relacionadas con las enfermedades transmisibles entre animales y humanos, e incluso en ellas, el vínculo Inter especie, a mi parecer, sigue siendo abordado de manera uni-disciplinar
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Chapter
Investigations of disease in one species of animal can provide valuable insights into the cause, pathogenesis and treatment of disease in another, and are an important part of comparative medicine. The value of comparative epidemiological studies may be either the coincidental product of investigations directed mainly at improving the health of animals, or may stem directly from the use of animals as surrogates for humans. A major field of comparative epidemiology has been the study of cancer. Cancers in dogs and cats are more akin to human cancers than laboratoryâanimal tumours, in which tumour development and responses may not predict the progress of human tumours with the same histology. Comparative studies involve reasoning by analogy, and the inferences can be wrong, exemplified by Snow's conclusion that cholera and yellow fever are transmitted by contaminated water, because they both occur in insanitary conditions.
Thesis
Lymphoma is a malignant neoplasm with high incidence both in human and veterinary medicine. As the dog is a domestic animal that lives closer and closer to its owners, studying the effects that the environment can have on their health is also studying the same effects on humans and the environment itself. The main objectives of this study were to characterize human and canine non-Hodgkin's lymphomas in Greater Porto, to identify the main sources of potential environmental risks and their association with the geographical distribution of animal and human cases of non-Hodgkin's lymphoma; comparing these data with those previously obtained in the region of São Paulo, Brazil. The individual and environmental characterization of canine lymphoma cases was studied through an exhaustive survey of their owners. Statistical analysis of the results showed that the risk of developing lymphoma may be associated with the animal's characteristics such as age, weight, size and race, as well as environmental and lifestyle factors such as feeding and tobacco smoking. The detailed characterization of lymphomas in the species was obtained through a complete analysis of samples obtained in the diagnostic process, both cytological (animals diagnosed during the thesis) and histological (archived samples from the Veterinary Pathology Service of ICBAS, between 2005 and 2016). In addition to the histological type, grade and proliferative index, we also carried out the immunophenotypic characterization of cytological samples. B-cell lymphomas accounted for the majority of cases (65% of cytological diagnoses and 57% of histopathological cases). It was also observed that 40% of cytological samples presented a high cell proliferation index (CPI), not always coincident with its histological grade. By individual analysis of the corresponding epidemiological survey, it was also observed that this CPI was related to cohabitation with smokers or not. The age and breed distribution of the affected animals coincided with the results of previous studies. On the "One Health" perspective, a comparative longitudinal study was carried out between human and canine non-Hodgkin lymphomas in the Greater Porto area. We included 1242 cases of human NHL diagnosed between 2005 and 2010 and 504 cases of canine lymphoma diagnosed between 2005 and 2016, characterized by descriptive epidemiological analysis, mapping and age standardized risks (ASR) of incidence. The results showed a greater risk for men and male dogs as well as a correlation of the corresponding geographical distributions. The highest values of ASR were found in large urban centers (Porto, Matosinhos and Maia) in both species. The international comparative study between human and canine lymphomas of Greater Porto and the city of São Paulo showed similarities of global prevalence between the two regions, with a proportion of T-lymphomas higher than that reported in the international bibliography in both regions. The identification of the main environmental pollutants resulted, however, in the disclosure of different phenomena. While São Paulo presents chronic high values of the atmospheric ozone, in the Greater Porto area the suspicions rests on the potentiating effects of high concentrations of radon in the atmospheric pollutants and tobacco smoke. During this thesis we also carried out the study of the implementation of an animal cancer registry, through the adaptation of the system already implemented in São Paulo. After the stages of adaptation, internal and external validation, and routine use in two veterinary centers, it was concluded that the registry represents a potential added value as an epidemiological tool. It was also possible to perceive the difficulties of its implementation in the field, mainly related to the collection of information and some complexity of the system. Online available at: https://repositorio-aberto.up.pt/handle/10216/111212
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Cancer is a common problem in dogs and although all breeds of dog and crossbred dogs may be affected, it is notable that some breeds of pedigree dogs appear to be at increased risk of certain types of cancer suggesting underlying genetic predisposition to cancer susceptibility. Although the aetiology of most cancers is likely to be multifactorial, the limited genetic diversity seen in purebred dogs facilitates genetic linkage or association studies on relatively small populations as compared to humans, and by using newly developed resources, genome-wide association studies in dog breeds are proving to be a powerful tool for unravelling complex disorders. This paper will review the literature on canine breed susceptibility to histiocytic sarcoma, osteosarcoma, haemangiosarcoma, mast cell tumours, lymphoma, melanoma, and mammary tumours including the recent advances in knowledge through molecular genetic, cytogenetic, and genome wide association studies.
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