Johnson et al, 2023

Abstract

Citation: Johnson, S.A.M.; Asmah, R.; Awuni, J.A.; Tasiame, W.; Mensah, G.I.; Paweska, J.T.; Weyer, J.; Hellferscee, O.; Thompson, P.N.

Full text

Citation: Johnson, S.A.M.; Asmah, R.;
Awuni, J.A.; Tasiame, W.; Mensah,
G.I.; Paweska, J.T.; Weyer, J.;
Hellferscee, O.; Thompson, P.N.
Evidence of Rift Valley Fever Virus
Circulation in Livestock and Herders
in Southern Ghana. Viruses 2023,15,
1346. https://doi.org/10.3390/
v15061346
Academic Editor: Yannick Simonin
Received: 27 May 2023
Revised: 5 June 2023
Accepted: 7 June 2023
Published: 10 June 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
viruses
Article
Evidence of Rift Valley Fever Virus Circulation in Livestock and
Herders in Southern Ghana
Sherry Ama Mawuko Johnson 1, 2, * , Richard Asmah 3, Joseph Adongo Awuni 4, William Tasiame 5,
Gloria Ivy Mensah 6, Janusz T. Paweska 7,8 , Jacqueline Weyer 7,8 , Orienka Hellferscee 7,9
and Peter N. Thompson 1, *
1Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria,
Onderstepoort 0110, South Africa
2School of Veterinary Medicine, University of Ghana, Legon, Accra 00233, Ghana
3
School of Biomedical & Allied Health Sciences, University of Ghana, Accra 00233, Ghana; rhasmah@ug.edu.gh
4Accra Veterinary Laboratory, Ministry of Food and Agriculture, Accra P.O. Box M161, Ghana;
josephawuni@hotmail.com
5School of Veterinary Medicine, Kwame Nkrumah University of Science and Technology,
Kumasi 00233, Ghana; drwilly2002@gmail.com
6Noguchi Memorial Institute for Medical Research, University of Ghana, Accra 00233, Ghana;
gmensah@noguchi.ug.edu.gh
7Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the
National Health Laboratory Service, Sandringham, Johannesburg 2192, South Africa;
januszp@nicd.ac.za (J.T.P.); jacquelinew@nicd.ac.za (J.W.); orienkah@nicd.ac.za (O.H.)
8
Department of Medical Virology, Faculty of Health Sciences, University of Pretoria, Pretoria 0002, South Africa
9Department of Medical Virology, Faculty of Health Sciences, University of Witwatersrand,
Johannesburg 2050, South Africa
*Correspondence: sajohnson@ug.edu.gh (S.A.M.J.); peter.thompson@up.ac.za (P.N.T.);
Tel.: +233-246-612145 (S.A.M.J.); +27-82-2970222 (P.N.T.)
Abstract:
Rift Valley fever (RVF) is a re-emerging zoonotic disease of domestic ruminants and humans.
While neighbouring countries have reported outbreaks of RVF, Ghana has not yet identified any cases.
The aim of this study was to determine whether RVF virus (RVFV) was circulating in livestock and
herders in the southern part of Ghana, to estimate its seroprevalence, and to identify associated risk
factors. The study surveyed 165 livestock farms randomly selected from two districts in southern
Ghana. Serum samples of 253 goats, 246 sheep, 220 cattle, and 157 herdsmen were tested to detect
IgG and IgM antibodies against RVFV. The overall seroprevalence of anti-RVF antibodies in livestock
was 13.1% and 30.9% of farms had RVFV seropositive animals. The species-specific prevalence was
24.1% in cattle, 8.5% in sheep, and 7.9% in goats. A RVFV IgG seroprevalence of 17.8% was found
among the ruminant herders, with 8.3% of all herders being IgM positive. RVFV was shown, for
the first time, to have been circulating in southern Ghana, with evidence of a recent outbreak in
Kwahu East; however, it was clinically undetected despite significant recent human exposure. A
One Health approach is recommended to better understand RVF epidemiology and socio-economic
impact in Ghana.
Keywords: zoonosis; Rift Valley fever; Ghana; One Health; vector-borne disease
1. Introduction
Rift Valley fever (RVF) is a mosquito-borne viral zoonotic disease caused by the Rift
Valley fever virus (RVFV), a phlebovirus of the family Phenuiviridae [
1
]. It is considered
a re-emerging disease of significant risk to public health, socio-economics, and trade [
2
].
It causes non-specific and mild febrile illness in humans and can result in complications
such as retinitis, hepatitis, and haemorrhagic and neurological syndromes [
3
–
6
]. Rumi-
nant herders, abattoir workers, and veterinarians are among those at the greatest risk of
exposure and infection [
7
]. In countries where the disease occurs, RVFV infections are
Viruses 2023,15, 1346. https://doi.org/10.3390/v15061346 https://www.mdpi.com/journal/viruses

Viruses 2023,15, 1346 2 of 13
considered underdiagnosed and widespread among people in close occupational contact
with livestock [8].
Rift Valley fever causes high mortality among young animals and/or abortion in adult
livestock, irrespective of the stage of gestation [
9
]. In pregnant sheep, mortality could be
up to 100% and 60% in adult ruminants [10].
Rift Valley fever has been reported in many West African countries, including Nige-
ria [
11
], Niger [
12
], Cameroon [
13
], and two countries bordering Ghana, namely, Cote
d’Ivoire [
14
] and Burkina Faso [
15
,
16
]. Ghana has a warm and humid climate and experi-
ences perennial flooding in the south, particularly in Accra and its environs, due to rapid
urbanization, climate variability, and flaws in physical planning [
17
–
19
]. These conditions
favour vector activity, a key factor for transmission and dissemination of RVFV.
At present, RVF is not one of the priority scheduled diseases for active surveillance
in Ghana by the Veterinary Services of the Ministry of Food and Agriculture [
20
] or the
Ghana Health service [
21
]. Consequently, RVF will not be considered among the list of
diseases causing abortions in livestock and febrile and haemorrhagic cases in humans since
the disease was not known to be found in Ghana. In 2016, the European Centre for Disease
Prevention and Control (ECDC) reported a case of RVF in an adult male in France that
“originated probably in Ghana” [
22
]. Given the zoonotic nature of the disease and the
clinical presentation in humans, RVF could be mistaken for malaria or any other febrile
illness. Therefore, a survey to determine its presence and level of occurrence in livestock
and humans in Ghana is key to protecting human and animal health.
A serological result of a small number of stored sheep and goat serum samples
at the Accra Veterinary Laboratory in 2010 [
23
] suggested that RVFV may have been
circulating among livestock in Ghana. We sought to confirm the occurrence and determine
the seroprevalence of RVFV in domestic livestock and livestock farmers in the southern
zone of Ghana and to assess associated risk factors for its occurrence to facilitate the
detection, control, and prevention of both livestock and human infection.
2. Materials and Methods
2.1. Study Area
The study was conducted between July 2019 and February 2020 in two southern
regions of Ghana, which is bordered on the west by Cote d’Ivoire, the north by Burkina
Faso, the east by Togo, and the south by the Atlantic Ocean and Gulf of Guinea. Ghana has
16 administrative regions and an estimated population of 30.8 million as of 2021 [
24
]. The
country has different ecological zones with tropical forests and coastal savannahs in the
south, humid savannahs in the centre, and dry savannahs in the northern belts [
18
]. The
climate is warm and humid with a bi-modal rainfall cycle in the south and central belts and
is uni-modal in the northern belt. The southern and central belts experience major rainfall
in March to July and a minor rainy season in September to November [18].
The study locations were Ga South and Kwahu East in the Greater Accra and Eastern
regions, respectively. Ga South municipality is one of the 26 municipal, metropolitan, dis-
trict assemblies (MMDAs) in the Greater Accra region, a coastal savannah agro-ecological
zone, and one of the flood-prone areas during heavy rainfall [
17
]. It includes three veg-
etation covers: moist semi-deciduous forest, mangrove swamp, and coastal scrub and
grassland [
25
]. The municipality is in the southwestern part of Accra, occupies a land area
of 517.2 square kilometres [
26
], and has a population of 350,121 [
24
] with 362 communities,
mainly engaged in agriculture and fishing.
The Kwahu East district is situated in the northern part of the Eastern region, and
it is known for its undulating landscape with steep slopes, several rock outcrops, and
scarps. The height of mountain peaks ranges between 220 and 640 m above sea level [
27
].
Kwahu East is considered to have a wet semi-equatorial climatic zone and a population of
79,726 inhabitants [
26
]. The district was selected for being in a semi-equatorial zone with
forest cover.

Viruses 2023,15, 1346 3 of 13
2.2. Target Population and Sample Size
The target livestock were domestic sheep, goats, and cattle. In the absence of a
published data on the prevalence of RVF in Ghana, a prevalence of 20% reported in Burkina
Faso [
17
] was used as an estimate for sample size calculation. Burkina Faso neighbours
Ghana on the north and has similar ecological zones. With an estimated prevalence of 20%,
a 95% confidence interval, and a maximum allowable error of 5%, the sample size was
computed to be 246 ruminants. The obtained sample size was multiplied by a design effect
(D) of 3 using an intracluster correlation coefficient (rho) of 0.25 and an average cluster
size of 9 based on the formula D = 1 + p (m
−
1) [
28
]. This gave a total sample size of
738 ruminants for the study (246 of each species).
2.3. Sampling-Farms and Livestock
A two-stage sampling method was employed. In stage one, the list of livestock farms
in the selected districts was obtained from the local district veterinary offices. The farm
lists constituted the sampling frame from which farms were randomly selected. On multi-
species farms, up to 9 sheep, goats, and cattle were sampled using systematic random
sampling. On single-species farms, the available ruminant type was sampled, and another
farm within the sampling frame was selected for the other two species to make up for the
sample size of the other species.
2.4. Variables Measured
A structured questionnaire was administered to the livestock farmers to assess demo-
graphic data of livestock (age, sex, breed), farm characteristics (farm size, type of housing,
proximity to water bodies), and flock health history (history of abortion, disposal of birthing
and aborted materials, clinical signs at the time of sampling).
2.5. Blood Sampling and Laboratory Analyses
Five mL of blood was drawn from the jugular vein directly into an 8.5 mL Vacutainer
®
tube with clot-activator and gel for serum separation. Sera were transported on ice to
a biosafety level 2 laboratory at the Noguchi Memorial Institute for Medical Research
of the University of Ghana, where they were centrifuged at 2500 rpm for 2–3 min and
aliquoted. The aliquot in cryogenic vials were stored at
−
20
◦
C until ready for testing. The
sera were tested for anti-RVFV antibodies using a commercial competitive enzyme-linked
immunosorbent assay (ELISA, ID Screen
®
Rift Competition Multi-Species ELISA, IDVet,
rue Louis Pasteur, France). The sensitivity and specificity of the test were documented to
be 91–100% and 100%, respectively [
29
]. All samples that tested positive were then also
tested using the RVF IgM Capture ELISA (IDVet, France) in order to determine recent viral
infection. The ELISA tests were performed according to the manufacturer’s instruction.
2.6. Human Serosurvey
The human serosurvey targeted livestock farmers or herders who worked directly
with ruminants in the study areas. On each livestock farm included in the study, the herder
or any close relatives who tendered livestock and consented were purposively selected and,
after giving informed consent, were sampled. A maximum of 5 mL of blood was collected
from each consenting farmer or herder. A structured questionnaire was administered to
participants to obtain socio-demographic information (age, gender, level of education,
occupation), as well as potential risk factors such as exposure to mosquitoes, contact with
livestock, use of protective clothing when handling sick animals, type of housing, and
consumption of raw milk.
Field assistants were drawn from the study region due to their familiarity with the
research area. They were trained on the correct administration of the questionnaire to
ensure consistency of responses and to reduce interview-related errors. The questionnaire
was pre-tested in a district other than the selected one for the study and administered by
trained field assistants.

Viruses 2023,15, 1346 4 of 13
Human sera were shipped to the Centre for Emerging Zoonotic and Parasitic Diseases,
National Institute for Communicable Diseases, Johannesburg, South Africa. The samples
were triple packed and shipped in accordance with CDC’s prescribed guidelines for pack-
aging and transporting infectious substances [
30
]. The samples were tested using inhibition
ELISA for the detection of RVFV antibodies; this assay did not distinguish between IgG
and IgM [
31
] ]. All positive samples by the inhibition ELISA were re-tested using IgG-
sandwich ELISA to detect anti-RVFV IgG and IgM-capture ELISA to detect anti-RVFV IgM,
as described previously [32,33].
2.7. Data Analysis
Seroprevalence of RVFV was estimated overall and for each species, with correspond-
ing 95% confidence interval (CI) using the logit transformation with farm-specific cluster
robust standard error. We assessed the bivariate relationship between each categorical
exposure variable and outcome (RVFV seropositivity) using the Chi-square test of inde-
pendence (and Fisher’s exact test where cell counts were low), followed by a multivariable
modified Poisson regression model with robust standard error that reported prevalence
ratios and corresponding CI. Separate models were conducted for livestock (with species
as an explanatory variable) and for humans. In the latter, in order to assess the association
between livestock and human seropositivity, the presence of at least one seropositive animal
on the farm was included as an explanatory variable. For initial variable selection, we
used a significance level of 20% followed by stepwise backward selection until all variables
were significant at p
≤
0.05. All statistical analyses were conducted in Stata SE version 16
(StataCorp, College Station, TX, USA).
2.8. Ethics Clearance
Ethics clearance was obtained from the Institutional Committee of Animal Use and
Care, University of Ghana (UG-IACUC 010/18-19), Faculty of Veterinary Science, University
of Pretoria Research Ethics Committee (REC065-19) and University of Pretoria Animal
Ethics Committee (REC065-19). Livestock Farmers’ Associations in the selected regions
and districts were consulted. Permission was granted by the field veterinarians in the
study districts. Individual written informed consent was sought and obtained from the
selected livestock farmers and herders after verbal explanation of the aims of the study,
and participation was voluntary.
For human sampling, ethics clearance was obtained from Research Ethics Committee,
Faculty of Health Sciences, University of Pretoria (554/019). Additionally, clearance was
obtained from the Ethics and Protocol Review Committee of the School of Biomedical and
Allied Health Sciences, University of Ghana (SBAS-MLS. /SA/2018-2019).
3. Results
3.1. Farm Characteristics
A total of 251 sheep, 252 goats, and 216 cattle was sampled from 165 farms, 32 in the
Ga South and 133 in the Kwahu East districts. Most of the farms (131; 79.3%) practiced
semi-intensive farming system, where animals were grazed during the day and penned
during the night. The rest of the farms practiced extensive (29; 17.6%) and intensive (5; 3.0%)
systems of farming. The farms were mixed species (67; 40.6%) of sheep, goats, and cattle.
Others were single-species, 24 (14.6%) with cattle, 38 (23.0%) with goats, and 36 (21.8%)
with sheep. Most farms (139; 84.2%) were situated near water bodies and in flood-prone
areas in both districts, as shown in Figures 1and 2.

Viruses 2023,15, 1346 5 of 13
Viruses 2023, 15, x FOR PEER REVIEW 5 of 13
Figure 1. A cale kraal situated less than 200 m from the Afram River in Kwahu East of the Eastern
region of Ghana. Picture by S. Johnson.
Figure 2. A flooded cale kraal at Hyewohoden in the Kwahu East District, Eastern Region of
Ghana. Picture by S. Johnson.
3.2. Breeds and Flock Sizes
Livestock kept at the time of sampling were mostly females (73.8%). Their ages
ranged from 5 to 144 months with a median of 30. About half of the farms (51.7%) had
reported abortions in recent months (median period = 6 months; range 1–36 months) prior
Figure 1. A cattle kraal situated less than 200 m from the Afram River in Kwahu East of the Eastern
region of Ghana. Picture by S. Johnson.
Viruses 2023, 15, x FOR PEER REVIEW 5 of 13
Figure 1. A cale kraal situated less than 200 m from the Afram River in Kwahu East of the Eastern
region of Ghana. Picture by S. Johnson.
Figure 2. A flooded cale kraal at Hyewohoden in the Kwahu East District, Eastern Region of
Ghana. Picture by S. Johnson.
3.2. Breeds and Flock Sizes
Livestock kept at the time of sampling were mostly females (73.8%). Their ages
ranged from 5 to 144 months with a median of 30. About half of the farms (51.7%) had
reported abortions in recent months (median period = 6 months; range 1–36 months) prior
Figure 2.
A flooded cattle kraal at Hyewohoden in the Kwahu East District, Eastern Region of Ghana.
Picture by S. Johnson.
3.2. Breeds and Flock Sizes
Livestock kept at the time of sampling were mostly females (73.8%). Their ages
ranged from 5 to 144 months with a median of 30. About half of the farms (51.7%) had

Viruses 2023,15, 1346 6 of 13
reported abortions in recent months (median period = 6 months; range 1–36 months) prior
to sampling. However, abortion rates could not be calculated, as farm records of health
were poorly kept.
Cattle breeds sampled were N’damas (36.1%), Gudali (23.6%), West Africa short horn
(20.4%), Zebu cross (18.1%), and Sangas (1.8%). The sheep were mainly Djallonkes (61.8%)
and Sahelian (38.2%). Most of the goats were West Africa dwarfs (75.8%) and Sahelian
(24.2%).
3.3. Seroprevalence in Ruminants
The distribution of RVFV seropositivity is presented in Table 1. The overall sero-
prevalence of RVF in the ruminants was 13.1% [95% CI: 10.5–16.2]. The species-specific
prevalence was 24.5% [95% CI:18.9–30.8] in cattle, 8.4% [95% CI: 5.3–12.5] in sheep, and
7.9% [95% CI: 4.9 11.9] in goats. Evidence of recent RVFV infection (positive for RVFV IgM)
was found in four (0.6%) of the livestock, three from Ga South and one from Kwahu East.
Table 1.
Prevalence and bivariate analysis of factors associated with Rift Valley fever seropositivity in
domestic ruminants in Kwahu East and Ga South districts, Ghana.
Factor N Overall
Prevalence (%) p-Value
District-Specific Prevalence
Ga South Kwahu East
nPrevalence
(%) p-Value nPrevalence
(%) p-Value
All species 719 13.1 187 6.4 532 15.4
Species 0.001 0.003 <0.001
Cattle 216 24.5 87 12.6 129 32.6
Goat 252 7.9 45 2.2 207 9.2
Sheep 251 8.4 55 196 10.7
Farm type
0.314 0.054 0.323
Mixed 304 11.5 100 8.0 204 13.2
Single-
species 415 14.2 87 4.6 328 16.8
Feeding
practice <0.001 0.054 <0.001
Cut and
carry 52 17.3 15 6.7 37 21.6
Grazing 333 18.0 100 10.0 233 21.5
Mixed 334 7.5 72 1.4 262 9.1
Sleeping
place at
night
0.453 0.005 0.489
Enclosed 528 12.5 130 3.1 398 15.6
Open
field 191 14.7 57 14.0 134 14.3
Sex 0.032 0.541 0.150
Female 531 14.7 119 7.6 412 16.8
Male 188 8.5 68 4.4 120 10.8
Age
(months) 0.022 0.019 0.378
≤18 213 9.4 88 3.4 125 13.6
19–29 107 8.4 21 0.0 86 10.5
30–39 177 14.1 44 6.8 133 16.5
≥40 222 18.0 34 17.7 188 18.1
Husbandry
practice 0.463 1.000 0.954
Extensive 106 16.0 0 - 106 16.0
Semi
intensive 597 12.7 179 6.7 418 15.3
Intensive 16 6.3 8 0.0 8 12.5
3.4. District and Farm-Specific Prevalence of RVFV
A total of 47 farms (28.5% [95% CI 22.3–36.6]) had RVFV seropositive animals. At
the district level, the proportion of farms with positive animals was 28.1% for Ga South
and 31.7% for Kwahu East districts. Farm level prevalence ranged from 0 to 85.5% with a

Viruses 2023,15, 1346 7 of 13
median of 10.0%. The district specific prevalence was 6.4% and 15.4% for Ga South and
Kwahu East, respectively (Table 1).
Table 1also shows the bivariate analysis of factors associated with RVF infection in the
animals. District, species, age, sex, and feeding practice were selected for the multivariate
model. Multivariate analysis of factors associated with RVFV seropositivity in livestock
is presented in Table 2. The results from the modified Poisson regression model showed
that the prevalence of RVF infection in livestock was higher in Kwahu East than Ga South
after adjusting for confounding, lower in sheep and goats than in cattle, and lower in farms
where grazing and mixed feeding were practiced compared to cut and carry only.
Table 2.
Multivariable analysis of factors associated with Rift Valley fever seropositivity in ruminants
in Kwahu East and Ga South districts, Ghana.
Factor Prevalence Ratio
[95% CI] p-Value
District
Ga South 1 *
Kwahu East 3.2 [1.8–5.5] <0.001
Species
Cattle 1 *
Goat 0.3 [0.1–0.4] <0.001
Sheep 0.3 [0.2–0.5] <0.001
Feeding
Cut and carry 1 *
Grazing 0.5 [0.2–0.9] 0.024
Mixed 0.3 [0.1–0.6] 0.002
* Reference level.
3.5. Seroprevalence in Ruminant Herders
A total of 157 herders were tested from 117 farms (Table 3). The median age of the
respondents was 44 years (range 18–66 years). A total of 25 farms (21.3%) had RVFV
seropositive herders. None of the herders tested exhibited signs suggestive of ill health at
the time of sampling. The overall seroprevalence of anti RVFV antibodies in the herders
was 17.8% [95% CI 12.2–24.7] using both inhibition ELISA and IgG sandwich ELISA, and
the two results agreed completely. The overall IgM seroprevalence was 8.3% (13/157) and,
of the 28 seropositive herders, 46% (13/28) were IgM positive, evidence of recent infection.
All 13 of the IgM seropositive herders were from the Kwahu East district.
Table 3.
Bivariate analysis of factors of Rift Valley fever virus seropositivity among herders in the
Kwahu and Ga South districts, Ghana.
Factor nRVFV Seroprevalence (%) p-Value
District 0.015
Ga South 32 3.1
Kwahu East 125 21.6
Gender 0.050
Female 53 9.4
Male 104 22.1
Age 0.860
≤30 18 22.2
31–40 45 17.8
41–50 53 15.1
≥50 41 19.5

Viruses 2023,15, 1346 8 of 13
Table 3. Cont.
Factor nRVFV Seroprevalence (%) p-Value
Assist in delivery 0.869
No 80 16.3
Yes 77 19.5
Abortion on farm 0.828
No 56 16.1
Yes 101 18.8
Live near livestock 0.839
No 70 17.1
Yes 87 18.4
Presence of flies on
farm 0.363
No 7 28.6
Yes 150 17.3
Farm RVFV status 0.837
Negative 82 17.1
Positive 75 18.7
The only factors significant in the multivariable model (Table 4) were district (preva-
lence was seven times higher in Kwahu East than Ga South) and gender (higher in males
than females).
Table 4.
Multivariable analysis of factors associated with Rift Valley fever virus seropositivity among
herders in Kwahu and Ga districts, Ghana.
Factor Prevalence Ratio [95% CI] p-Value
District
Ga South 1 *
Kwahu East 7.5 [1.1–52.8] 0.043
Gender
Female 1 *
Male 2.5 [1.0–6.3] 0.041
* Reference level.
Figure 3shows the distribution of farms with RVFV-positive livestock and herders
in the study sites. The seropositive farms appear clustered around the Lake Volta and
Weija dam in the Kwahu East and Ga South districts, respectively. Several areas (red
and black balls) are shown to farms where both herders and livestock were exposed to
RVFV. Sempoa, a rural and less-privileged community in the Kwahu East had the highest
proportion of farms (24.2%) with infected ruminants and herders. Livestock health history
in Sempoa showed that many cattle had died suddenly in 2018; however, these deaths were
not investigated. The community was without an animal health post and relied on animal
health staff from other distant communities.

Viruses 2023,15, 1346 9 of 13
Viruses 2023, 15, x FOR PEER REVIEW 9 of 13
Figure 3. Distribution of RVFV seropositive farms and herders Ga South and Kwahu East, Ghana.
4. Discussion
This study provides the first conclusive evidence of RVFV circulation in Ghana, both
in domestic ruminant species and in humans. Serological evidence of infection was found
in both Ga South in the Greater Accra region and Kwahu East in the Eastern region of
Ghana. The detection of IgM in both livestock and herders, notably in Kwahu East, indi-
cates that a recent, undetected RVF outbreak has occurred, likely causing undiagnosed
human and livestock illness. As IgM is a known marker of recent infection and generally
declines 2–3 months post-infection in viral infections [34], exposure of herders in Kwahu
East to RVFV within the previous few months was demonstrated.
An overall RVFV prevalence of 18% in livestock and 13% in humans likely has sig-
nificant public health implications. Rift Valley fever presents generally as a febrile and
influenza-like illness and could easily be mistaken for malaria and treated as such. Among
the herders tested, most presented apparently healthy, consistent with the fact that RVFV
could be missed or mistaken for another illness [35]. This was consistent with a study in
Mozambique where RVFV-seroconverting patients were misdiagnosed and assumed to
be malaria cases [36]. This situation may also be the case in Ghana, as malaria is endemic
and remains amongst the top five differential diagnoses for febrile illness in humans.
Our findings in both ruminants and herders were consistent with those reported
from areas in which RVFV was known to circulate endemically with or without periodic
outbreaks in East Africa [37], West Africa [38], and South Africa [35]. Several studies have
indicated circulation of RVFV in West Africa [14,38], some with subclinical circulation and
others with outbreaks in livestock.
The fact that almost half of the herders in Kwahu East who tested positive for anti
RVFV IgG were also positive for anti RVF IgM indicates a recent undetected outbreak in
Figure 3. Distribution of RVFV seropositive farms and herders Ga South and Kwahu East, Ghana.
4. Discussion
This study provides the first conclusive evidence of RVFV circulation in Ghana, both in
domestic ruminant species and in humans. Serological evidence of infection was found in
both Ga South in the Greater Accra region and Kwahu East in the Eastern region of Ghana.
The detection of IgM in both livestock and herders, notably in Kwahu East, indicates that
a recent, undetected RVF outbreak has occurred, likely causing undiagnosed human and
livestock illness. As IgM is a known marker of recent infection and generally declines
2–3 months
post-infection in viral infections [
34
], exposure of herders in Kwahu East to
RVFV within the previous few months was demonstrated.
An overall RVFV prevalence of 18% in livestock and 13% in humans likely has sig-
nificant public health implications. Rift Valley fever presents generally as a febrile and
influenza-like illness and could easily be mistaken for malaria and treated as such. Among
the herders tested, most presented apparently healthy, consistent with the fact that RVFV
could be missed or mistaken for another illness [
35
]. This was consistent with a study in
Mozambique where RVFV-seroconverting patients were misdiagnosed and assumed to be
malaria cases [
36
]. This situation may also be the case in Ghana, as malaria is endemic and
remains amongst the top five differential diagnoses for febrile illness in humans.
Our findings in both ruminants and herders were consistent with those reported
from areas in which RVFV was known to circulate endemically with or without periodic
outbreaks in East Africa [
37
], West Africa [
38
], and South Africa [
35
]. Several studies have
indicated circulation of RVFV in West Africa [
14
,
38
], some with subclinical circulation and
others with outbreaks in livestock.
The fact that almost half of the herders in Kwahu East who tested positive for anti
RVFV IgG were also positive for anti RVF IgM indicates a recent undetected outbreak in

Viruses 2023,15, 1346 10 of 13
Kwahu East. This is supported by the fact that RVFV seroprevalence is high in all age
groups of livestock in Kwahu East. In contrast, seroprevalence in livestock in Ga South
showed seroprevalence gradually increasing with age, being highest in the oldest animals.
This suggests low-level endemic circulation in that area, in which seasonally flooded
wetlands provide suitable conditions for maintenance of RVFV circulation in mosquito
vectors.
The highest RVFV seroprevalence in livestock (15%) was recorded in Kwahu East,
more than twice the prevalence recorded in Ga South (6%). This was to be expected
following an outbreak, with high seroprevalence in all age groups. Livestock farmers
lived in close proximity with livestock in Kwahu East and were likely to be exposed to
infected animals (including birthing materials) in addition to the vector activity. However,
no association was found between human RVFV seropositivity and livestock seropositivity
on the same farm. Although human exposure was thought to occur mainly via exposure to
infected animals, our results could indicate significant human exposure due to mosquito
bites. This requires further investigation.
As many as 29% of the farms sampled had seropositive livestock, showing widespread
occurrence of RVFV in the study area. Less than 1% of the seropositive livestock showed
evidence of recent infection, and this agrees with similar findings where very recent animal
outbreaks have not occurred [
39
]. The farm-level prevalence could not be ascribed to
vaccination, as Ghana has never vaccinated livestock against RVFV, particularly because it
was not thought to be present in the country.
In Kwahu East, RVFV seropositivity was clustered around Sempoa and Hywohoden
(Figure 3). These two communities were noted for Fulani-herder and nomadic activities
resulting in conflicts, as reported in recent occurrence in southern Ghana [
40
]. The nomadic
Fulani herdsmen were reported to be from Mali, Niger, Nigeria, and other undetermined
places who moved in and out of these communities with their livestock for greener pastures.
According to FAO [
41
], animal movements, trade, and weather conditions were the main
risk factors for the occurrence and reoccurrence of RVF in West Africa and spread to
unaffected areas.
It was not possible to ascertain abortion rates in this study due to poor record keeping
of health history on the farms. The source of replacement stock was found to be from
within Ghana. However, the original source of the livestock sold in the open market was
difficult to ascertain, as livestock mobility through transhumant activities was difficult
to record. Livestock movements are considered an important driver of infectious disease
transmission and spread, and the many unapproved routes of transporting livestock to and
from Ghana could be a risk factor for the spread of diseases. Further study is required to
establish the role of transhumance in the spread of transboundary animal diseases such as
RVF in Ghana.
In a study to map seasonally varying environmental suitability of RVF in Africa,
Ghana was found to be suitable for RVFV outbreaks [
42
]. Given that livestock farming is
the second income-generating activity in the Kwahu East district [
43
], a large outbreak of
RVF could be devastating to the livelihoods of the population, and preventative measures
are required. Our finding, therefore, calls for RVFV to be kept on the radar of the animal
and human health sectors in Ghana.
5. Conclusions
This study indicated that RVFV has been circulating in livestock and humans in
the southern part of Ghana. Kwahu East showed a higher level of RVFV exposure in
livestock and humans compared to Ga South, with evidence of recent infection, indicating
an undetected outbreak in livestock and humans. Further studies are recommended to
understand the burden of RVF in Ghana. A One Health approach is required to further
investigate the epidemiology and socioeconomic impact of RVF and for risk mapping to
predict and prevent outbreaks.

Viruses 2023,15, 1346 11 of 13
Author Contributions:
Conceptualization, S.A.M.J. and P.N.T.; methodology, S.A.M.J., P.N.T., G.I.M.,
and R.A.; laboratory testing and formal analysis, S.A.M.J., P.N.T., J.T.P., J.W., O.H., and G.I.M.;
investigation, S.A.M.J., J.A.A., P.N.T., and R.A.; resources, S.A.M.J., P.N.T., J.A.A., and R.A.; data cura-
tion, S.A.M.J. and W.T.; writing—original draft preparation, S.A.M.J.; writing—review and editing,
S.A.M.J., P.N.T., J.T.P., and W.T.; visualization, S.A.M.J.; supervision, P.N.T.; project administration,
S.A.M.J. and P.N.T.; funding acquisition, S.A.M.J. and P.N.T. All authors have read and agreed to the
published version of the manuscript.
Funding:
This research was funded by Future Africa Institute, University of Pretoria with funding
from Carnegie Corporation of New York and BANGA Africa Project of University of Ghana. The
APC was funded by Future Africa, University of Pretoria.
Institutional Review Board Statement:
The study was conducted according to the guidelines of the
Declaration of Helsinki and approved by the Institutional Review Board (or Ethics Committee) of
University of Pretoria and University of Ghana (protocol code 554/2019 [08.01.2020], REC065-19
[15.10.2019], and UG-IACUC 010/18-19 [07.05.2019]; SBAHS-MLS/SA/2018-2019 [31.05.2019]).
Informed Consent Statement:
Informed consent was obtained from all subjects involved in the
study.
Data Availability Statement:
The data presented in this study are available on request from the
corresponding authors. The data are not publicly available due to ethical reasons.
Acknowledgments:
This study was supported by research fund from the University of Pretoria’s
Future Africa through its Early Career Research Leader Fellowship with funding from Carnegie
Corporation of New York. A great appreciation goes to Richard Bochtwey, the Veterinary staff in
charge of Kwahu East. He led and organized the livestock farmers and assisted in restraints of the
livestock for sampling. A huge thanks goes to Eric Yeboah, the Agriculture Extension Agent in
Kwahu East. He led us into the communities in his operational areas and facilitated community entry.
Bright Bamfo, a Veterinary Nurse of the University of Ghana School of Veterinary Medicine supported
in sampling and restraint of the livestock. Ekua Thompson (DVM) supported in blood sampling
and administration of questionnaire to farmers/herders. Sally Gidiglo and all the Veterinary Staff
in Ga South for their immense support in leading the team to the various farms and facilitating
sampling in Ga South. Joseph Armachie, Francis Nuvey, and Andrew Breman supported with data
analysis and interpretation. We acknowledge the laboratory team at NICD who tested all the human
samples Phumza Ohaebosim and Venessa Patharoo. A big thank you to the University of Ghana
BANGA-AFRICA project for the grant writing workshops that enabled me to write and win grants.
Thank you to the Department of Research and Innovation (DRI) of the University of Pretoria for the
writing retreat which enabled the completion of the write-up of this paper. Additionally, to the many
farmers who consented to sampling of their animals and answered our questions, thank you!
Conflicts of Interest:
The authors declare no conflict of interest. The funders had no role in the design
of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or
in the decision to publish the results.
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