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Hindawi Publishing Corporation
International Journal of Zoology
Volume , Article ID , pages
http://dx.doi.org/.//
Research Article
Cockroach Infestation and Factors Affecting the Estimation of
Cockroach Population in Urban Communities
Gholam Hossein Shahraki, Saadat Parhizkar, and Alireza Raygan Shirazi Nejad
Faculty of Health Science, Yasuj University of Medical Sciences, Yasuj, Iran
Correspondence should be addressed to Gholam Hossein Shahraki; vahabsh@yahoo.com
Received February ; Revised April ; Accepted April
Academic Editor: Randy J. Nelson
Copyright © Gholam Hossein Shahraki et al. is is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.
Cockroach is one of the most important pests in urban communities. is study was conducted to determine the situation of
cockroach infestation and eective factors on cockroach trap count in urban communities of Yasuj City in southwestern Iran. In
this study cockroach population in sampling units (residential units, ocial places, and hospitals) was monitored using sticky
traps over a ve-week trapping period. Occupants of residential units were also questioned (by means of questionnaire) for
cockroach infestation in their respective residence. e study shows almost % of sampling units were infested by cockroach. Five
species from two families had been identied: Blattidae (comprising Blatta orientalis,B. lateralis,andPeriplaneta americana)and
Blattellidae (comprising Blattella germanica and Supella longipalpa). German cockroach, B. germanica, with widespread distribution
(% of infested sampling units) showed the highest frequency (.%) of trap counts. e expression of the distribution of German
cockroach populations and some factors could aect trapping, and population monitoring in an urban community was surveyed.
Additionally, aecting some exclusion factors on cockroach infestation was pointed. Rates and source of cockroach infestation were
discussed from the viewpoints of the residents.
1. Introduction
Cockroaches have been in existence for about million
years [], and they are one of the important groups of insect
pests in urban environments. Cockroaches not only spoil
food but also transfer pathogens and cause allergic reactions
and psychological distress []. As a potential mechanical
vector of human diseases, many pathogenic organisms have
been associated with cockroaches. ese include poliomyeli-
tis viruses, bacteria, fungi, protozoa, and helminthes [–
]. Pai et al. [] reported cockroaches as potential vectors
of nosocomial infections. Moreover, bacteria with antibiotic
resistance have been isolated from household cockroaches
[,]. e most common important species is associated to
surveyed locations. In the southeastern United States, smoky-
brown cockroach [], in New Zealand, German cockroach
[],andinSoutheastAsia,Americancockroach[–]were
found to be the most dominant species, respectively. While
the German cockroaches, Blattella germanica (L.), are not
present in households in Southeast Asia, they are prevalent
insect pests in hotels and food outlets [,]. ere are over
, species of cockroaches worldwide. Of these only several
species are commonly associated with humans. ree domi-
ciliary species of importance are the German cockroach, the
American cockroach (Periplaneta americana), and the Orien-
tal cockroach (Blatta orientalis)[]. German cockroach has
a worldwide distribution, although it originated in north or
tropical Africa despite the misleading common name [].
However, German cockroach has created substantial pest
problems in many developing countries [–]. is species
reported a common indoor pest in low-income housing [].
According to the report by Hana-Bojd and Sadaghiani
[], there are species of cockroaches from families:
Polyphagidae ( species), Blattidae ( species), Blattellidae (
species), and Ectobiidae ( species), that have been identied
throughout the cities of Iran so far. ree species, the Ger-
man cockroach, the American cockroach, and the Oriental
cockroach, are the most common species that have caused
health problems in urban communities (e.g., residential
buildings, hotels, hospitals, restaurants, and shopping) of
International Journal of Zoology
T : Surveyed locations and results of trap monitoring throughout the programme.
Type of location Number of
locations
Sampling
units
Size of units
(limitation)
Infested
sampling units
Number of infested
units with
B. germanica
Number of identied
cockroaches (%)
Dormitories from
four universities∗ dormitories – m×. m (%)
B. germanica (.%)
B. lateralis (.%)
P. americana (.%)
S. longipalpa (.%)
B. orientalis (.%)
Hospital hospitals – m× m (%)
B. germanica (.%)
B. lateralis (.%)
P. americana (.%)
Housing complex buildings m×. m (%)
B. germanica (.%)
P. americana (.%)
Supella longipalpa (.%)
Ocial place building – m× m (%) B. lateralis (%)
Hotel building – m×. m (%) B. lateralis (%)
∗YUMS, YU, AU, and TU.
Iran. Additionally, Polyphaga indica,P. a e g y p t i a c a ,Periplan-
eta australasiae,andBlatta lateralis are the other important
cockroaches in Iran.
Yasuj,whichissituatedinsouthwesternIranandthe
capital of Kohgiluyeh va Boyer Ahmad, was chosen for this
study. e province covers an area of , square kilometers
and in had a population of , []. e weather
varies with seasons: cold and snowy in the winter, cold or
moderate and rainy in the spring and fall, and hot (not more
than ∘C)anddryinthesummer[]. Mean annual tem-
perature, rainfall, and humidity are ∘C, mm, and %
RH, respectively. Although ancient structures of housings are
predominant throughout the city, new structures of buildings
have sprung up in the last few years [].
2. Materials and Methods
Aer a preliminary survey on private and public places in
the southwestern of Iran, Yasuj City, sampling units were
selectedforthestudy(usingstickytrap),andasamplingunit
comprised an “apartment unit” for residential building and a
“room” for hospital, dormitory, hotel, and government oce
(Table ). At the inspection stage, monitoring was performed
weekly using sticky traps for sampling units. Moreover
private houses had been surveyed by questionnaire. e
sticky traps were manufactured by Ridsect (produced by Sara
LeeSch.Bhd.Malaysia)inbaitedtentform,andthesize
of the sticky surface of the trap was ×cm
2. Depending
on the surveyed locations, traps were placed in cabinets,
under the sink, beside the refrigerator, beside the stove, in
closets, and on shelves, with one side of the trap resting
against a vertical surface. Average one trap per eight square
meters was installed in sampling units. Totally the number of
cockroaches per trap for each sampling unit was estimated.
Infestation rate is dened as cockroach trap count per trap
during seven-day trapping period. Numbers of cockroaches
trapped were recorded weekly aer each -day trapping
period. e trapping process continued for a -week period.
A set of questionnaires were distributed for occupants
of the residential units (from dormitories, private
houses, and house building complexes) to obtain infor-
mation about cockroach infestation in their houses (e.g.,
size of cockroach, time, and entrance-source of cockroach
infestation). Some details of the structural design (conjugated
to survival of cockroach) for units of hospital were
collected by the other set of questionnaire.
Data was analyzed by Kruskal-Wallis Test and Spearman
correlation coecient besides descriptive statistics using the
SPSS soware.
3. Results and Discussion
From a total of sampling units inspected using trapping
(i.e., apartments, units, or housings), .% ( units) were
infested with cockroaches. e results show that , , , ,
and % of the sampling units in the surveyed dormitories,
hospitals, housing building complexes, ocial places, and
hotel, respectively, were infested with cockroaches (Table ).
erefore, the hospitals showed the highest frequency of
infested units via trap monitoring. Plumbing facilities (i.e.,
wash basin), heating source, and openings in the roof for
, ., and % of units (𝑁=69units) at the hospi-
tals, respectively, obtained from the questionnaire, could be
detected as eective factors for survival of cockroach []
which explained the high rate of infestation for the hospitals.
A survey on private houses throughout the city by means
of questionnaires showed that % of residences complained
of cockroach infestation. erefore, survey by cockroach trap
monitoring showed that all surveyed locations ( areas) in
this city were infested with cockroaches, although infestation
rates varied throughout the urban communities.
From a total of cockroaches collected from
dierentlocationsofthecity,vespeciesofcockroaches
had been identied. e German cockroach was the most
abundant comprising .% of all cockroaches trapped.
e other identied species in order of abundance were the
International Journal of Zoology
Turke s t a n c oc k ro a c h ( Blatta lateralis)(.%),theAmerican
cockroach (.%), the Brown-banded cockroach (Supella
longipalpa) (.%), and the Oriental cockroach (.%). e
recognized species are from two families: Blattidae (compris-
ing B. orientalis,B. lateralis,andP. americana)andBlattel-
lidae (comprising B. germanica and S. longipalpa). Hana-
Bojd and Sadaghiani [] previously reported four families
from indoor and outdoor survey (Polyphagidae, Blattidae,
Blattellidae, and Ectobiidae). However three species, the
German, American, and Oriental cockroaches were reported
as the most common species in Iran []. ese species were
detected in this study, although the Turkestan cockroach
instead of the Oriental cockroach showed the third common
species (for frequency of distribution and dispersion). Per-
centage frequency of the German cockroach in the ve types
of study locations (Table )showstheGermancockroach
was the most abundant in the dormitories (%), housing
(%), and hospital (%), respectively, compared to the
other species. However, it was not seen in ocial places and
hotels. Moreover, more than % of infested units ( from
units; Tabl e ) were infested by the German cockroach
(i.e., the highest frequency of dispersion among infested
units). erefore, surveyed dormitories showed the most
diverse composition with all ve species present and the most
abundant for the German cockroach compared to the other
study locations. Ocial places and hotels with the lowest
infested units ( and %, resp.) revealed the least varied
for cockroach species and least abundant for the German
cockroaches. However, more ocial buildings and hotel units
need to be surveyed to substantiate the ndings.
Sizeable German cockroach trap count was detected
for four study locations (Table ). e expression of the
distribution of German cockroach populations in space at
four locations based on the formula of the variance to mean
ratio ([𝜎2/𝜉 < 1] for uniform [𝜎2/𝜉 = 1] for random, and
[𝜎2/𝜉 > 1]forclumped)[]wasclumped,althoughforthe
hospitalsthisratiowasneartorandom(Tab l e ). is index is
important because it is consistent from year to year for each
species []. e German cockroach is known as domestic
cockroach and lives in groups (semisocial insect), and they
are rarely dispersed throughout a building [,]. us
clumped distribution for these species is expected. Cockroach
infestation rates for hospital and residential building show
lowermeanthangirls’andboys’dormitories,althoughthere
was no signicant dierence (𝑃 > 0.05) between mean
of cockroach infestation rates for four surveyed locations
(Kruskal-Wallis Test; chi-square = ., d.f = , and 𝑃=
0.509).
Some factors aecting the estimating of cockroach pop-
ulation in an urban community were surveyed. Survey on
infestation rates (German cockroach infestation) for the units
( units at four locations) which were located on dierent
oors showed the number of oors (i.e., distance of apart-
ment from ground) did not signicantly aect cockroach trap
counts (𝑟𝑠= 0.118,𝑃 = 0.324). Moreover, there was no signif-
icant dierence in cockroach infestation rates between oors
of these buildings (Kruskal-Wallis Test; chi-square = ., d.f
=,and𝑃 = 0.106)(Table ). Additionally the variance of
the population was positively correlated with elevation of the
T:Meanofcockroachtrapcountsforfourstudylocations.
Study
locations
Number of
surveyed
units
Frequency
of infested
units
Mean of
infestation rate
(per trap/unit)∗
Varianc e
/mean ratio
Girls’
dormitory % . .
Boys’
dormitory % . .
Residential
building % . .
Hospital % . .
∗Forinfestedunits.
T : Mean and variance of cockroach tap counts for surveyed
oors of four surveyed buildings ( units).
Floor Mean NStd. deviation Variance
G . . .
. . .
. . .
. . .
. . .
Total . . .
oors (the highest oor with the biggest variance; Table ),
and this correlation was signicant (𝑟𝑠=7,𝑃(1-tailed)=
0.045). Paige [] reported strong population uctuation of
German cockroach was negatively correlated with barometric
pressure. It can be deduced that the higher the oors of a
building, the greater the cockroach population uctuations.
ese observations will be useful when conducting survey of
cockroach infestations in buildings with more than ve oors
high or in skyline structures.
Eighty one percent of residents for three dormitories
(comprising units) said that their units were infested
by cockroaches, although % of those units were detected
as infested via cockroach trap monitoring. Actually resi-
dents reported % higher infestations of units than that
determined from trap monitoring. is is probably due
to the low tolerance of a considerable number of respon-
dents towards cockroach, prompting to a questionably high
incidence of infestation. Moreover, sensitivity of trapping
method for clean level of infestation could be inuenced by
frequency of infestation, and those units with less than one
cockroach per trap (nominated as clean level unit) reported
as infested instead. Brenner et al. [] reported dierent
rates of cockroach prevalence for residential apartments
from questionnaire and trapping. Agrawal and Tilak []
reported more cockroach counts based on visual counts
method compared to sticky trap method. However, the traps
(baited with mouse pellets) were reported as a best way to
determine cockroach infestation [–]. Only % of the
occupants at the infested units did not notice any infestation.
is could be attributed to these occupants being away
from home. Moreover, survey on study units of private
houses, dormitories, and housing complex via questionnaires
showed that residents for % of surveyed residential units
International Journal of Zoology
T : Frequency of resident’s responses to four items of questionnaire.
Type of location Sampling units∗Frequency of
old ancient
Pointed out to
infestation of their
units
Encountered German
cockroach size
(≤. cm)
Pointed out to infestation
initiated from more than
months ago
Dormitories (/) % (/) % (/) %
Private houses (%) (/) % (/) % (/) %
Housing
complex (/) % (/) % (/) %
Total (%) (/) % (/) % (/) %
∗Unit or houses.
admitted to cockroach infestation in their houses (Tab l e ).
Comparison of this rate and total infestation report via
trapping (%) shows % reduction for clean level units (in
agreement with previous report: % for the dormitories).
erefore, the determination of cockroach infested units is
highly associated to the type of cockroach monitoring. Survey
on house kitchens of the dormitories via two approaches
(visual and trap counts) showed that cockroach had been seen
immediately once upon entry for % of infested kitchens.
From % remaining kitchens, the cockroach had been seen
visually in % of these places when the trash container
was moved. Survey via sticky trap resulted in % high
levels of infestation (≥ cockroach per trap per kitchen)
for the kitchens. is is close to the rate of visual survey
(%) even aer moving the trash container (%) in the
kitchens. However, the greatest dierence between methods
is observed for the determination of very low levels of
infestation. It shows a limitation for exact determination of
infested sampling units.
e other factor pointed as an eective factor on infes-
tation is age of building. Only % of surveyed places were
considered old (≥ years old). All of these places were in the
categories of private houses (Tabl e ). Surveys on the houses
showed % of old houses versus % of new houses (
versus houses) were infested by cockroaches. erefore,
age of building could have an impact on infestation, although
the correlation between the two factors was not signicant
based on % CI (𝑟𝑠= 0.149,𝑃 = 0.150). Survey also showed
% of infested units were infested more than six months
prior to the survey (Table ), suggesting infestation did not
occur spontaneously and transient in nature.
e other factors that could aect trapping (and/or pop-
ulation monitoring) are attacks by other pests and damage
to traps. Out of the inspection of cockroach traps in
the surveyed dormitories throughout the programme, .% of
traps were found damaged. e most frequent cause of these
damages(.%)wasthatthetrapshadbeenthrownoutby
residents. Although a brieng for occupants to accept and
contribute to this programme led to reduction in trap dispo-
sition, a number of respondents were not comfortable with
the image that their living or working place is infested with
cockroaches. e incidences of damage by lizard (.%), ant
(.%),andmice(.%)werelowinthisstudy,althoughfor
other countries, such as Malaysia, lizard (and also ant) could
be the greatest cause of trap damages. erefore incidence
T : Frequency of screened fans at the surveyed kitchens.
Cockroach infestation No. of units (%) Tot al
Fan without screen Screened fan
Clean level of infestation (.%) (.%)
Infested with cockroach (.%) (.%)
Total (.%) (.%)
oftrapdamagecanbeassociatedwithexistingfactorsinthe
surveyed location.
e other eective factors on cockroach infestations are
exclusion factors related to urban buildings. In this survey
% of units (from units) had opening in the wall or roof
without screen. e frequency of this factor for infested units
in three surveyed dormitories was % versus % for clean
level units. However, there was no signicant (𝑃 = 0.05)
correlation between infestation and opening in the wall or
roof.
Crack and crevices had been detected for % of units
(from units). Frequency of crack and crevices for infested
units of three dormitories was % versus .% for clean
level units. However, there was no signicant (𝑃 = 0.05)
correlation between infestation levels and crack and crevices.
Survey on kitchens of dormitories showed electric
air fans (air conditioner fans) had been screened for %
infested kitchens versus % clean level kitchens. ere was
a signicant correlation (𝑃 < 0.05,Spearman)between
screened fans and infestation (𝑟 = −0.396,𝑃 = 0.047)
(Table ).
Kitchen drains were not screened in % of infested
kitchens versus % clean level kitchens in these dormitories.
However, there was no signicant correlation (𝑃 = 0.05)
between infestation and unscreened drains.
Based on the residence opinions (survey on residen-
tial units), the sources of cockroach infestation are the toilet
(.%), kitchen (.%), rubbish containers (.%), and
neighbors’ residence (.%) (Table ). German cockroaches
prefer dry habitats with a nearby water source such as
kitchen and bathroom []. Stephan []reported%
of the emigrants German cockroach came from adjoining
kitchen areas. However, the American cockroach (with .%
frequency in the surveyed dormitories) prefers wet and moist
locations such as sewers and toilet. Toilet and kitchen with
high frequency of choice by respondents could be the main
entrance-source of these species. However, the local name of
International Journal of Zoology
T : e entrance-source of cockroaches according to standpoint of occupants for surveyed units of dormitories.
e entrance-
source of
cockroaches
Toilet House
kitchen Neighbours Rubbish
containers
N
and
T
N
and
R
T
and
R
T
and
K
N, T,
and
R
N, T,
and
K
T, K,
and
R
N
and
K
N, T,
K,
and R
Others
(yard or
drainage)
Did
not
know
Total
Frequency ∗
Percentage . . . . . . . . . . . . . . .
∗ residents were questioned, although %of them had answer. T: toilet, K: kitchen, R: rubbish container, and N: neighbours.
cockroach in the research country is bath beetle which came
rstfromtheAmericancockroachandtheirharborage.is
name may have misled some people to choose toilet as the
highest incidence rate for the entrance-source. erefore, the
study shows that the viewpoints of the residents about the
entrance-source and predominant species concur with the
result from the cockroach trap counts. Seventy percent of
occupants in the surveyed dormitories and housing complex
(from units; Tab l e ) encountered cockroaches with sizes
less than .cm (the German cockroach size) close to the
rate of the German cockroach-infested units of the same
buildings detected via trapping (% from infested units;
Table ). However, incidence of infested units encountered
by residents was % higher than that estimated from the
cockroach traps counts exercise.
In conclusion, more attention needs to be given to view-
points of residents and factors aecting population (moni-
toring methods, damages, and exclusion) when conducting
a survey on cockroach in urban communities.
Acknowledgments
e authors are grateful to Professor Dr. Dzolkhii B. Omar,
Prof.Dr.YusofB.Ibrahim,Dr.MohdKhadriShahar,and
Dr. Faizah Abood for technical help and their guidance for
the duration of this project. ey thank the Vice-Chancellor
of Yasuj University of Medical Sciences, Yasuj University,
Azad University, and Tarbiat Moallem University for their
invaluable assistance for access to the study sampling units.
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