Seroprevalence and Associated Risk Factors of Rift Valley Fever in Domestic Small Ruminants in the North Region of Cameroon

Abstract

Rift Valley fever (RVF) is a zoonotic vector borne infectious disease of major medical and veterinary importance particularly in sub-Saharan Africa. However, there is dearth of epidemiological knowledge of the disease in Cameroon. We conducted a cross-sectional study (January 2016–January 2017) to investigate the seroprevalence and potential risk factors of Rift Valley fever virus (RVFV) in sheep and goats in the North region of Cameroon. Stratified sampling approach was used to select herds where sera were collected from 680 randomly selected small ruminants (355 goats and 325 sheep) in eight localities (Kismatari, Lagdo, Pitoa, Garoua, Bocklé, Dembo, Poli and Touboro) within three administrative divisions (Bénoué, Mayo-Rey and Faro) in the North region. Anti-RVFV antibodies were detected using a competitive Enzyme-Linked Immunosorbent Assay (ELISA), while a capture ELISA was used for the detection of specific RVFV-Immunoglobulin M (Ig-M) antibodies. We evaluated the associated potential risk factors of RVF in small ruminants based on observations of animal-related intrinsic and extrinsic factors in combination with serological results. The results revealed that 3.4% (95% confidence interval (CI): 2.2–5.1%) of sampled animals and 24.6% (95% CI: 15.1–37.1%) of 65 sampled herds were seropositive for anti-RVFV antibodies and no difference in seropositivity between sheep and goats at individual animal as well as at herd levels was observed. Localities along hydrographic or large water banks such as Kismatari (OR: 14.333, (95% CI: 1.436–145.088)) and Pitoa (OR = 11.467 (95% CI: 1.249–50.306)) were significantly associated to RVFV antibody seroprevalence in a simple logistic regression. In addition, the multiple regression analysis showed that age and access to water points significantly influenced RVFV antibody seroprevalence in small ruminants. This study revealed that anti-RVFV antibodies are present in sheep and goats in the North region of Cameroon. It highlights the likely endemic circulation of RVFV in the considered localities despite the absence of clinical cases reported in animals or humans. Under these conditions, it is necessary to set up an early warning, surveillance and control strategy based on epizootic risk.

Diversity and Abundance of Potential Vectors of Rift Valley Fever Virus in the North Region of Cameroon

“…Poueme et al [ 23 ] reported the presence of RVFV-specific antibodies in Cameroonian livestock and higher seroprevalence rates in Pitoa and Lagdo due to the present risk factors in these areas. The previous study of Rissmann et al [ 24 ] also confirmed the circulation of RVFV in Cameroon.…”

“…Despite reports of RVFV-specific antibodies in livestock from the North Region of Cameroon [ 23 , 24 ], no entomological study on the potential vectors that play an important role in the transmission and spread of the virus [ 5 , 25 ] has been carried out before. In-depth knowledge of the bioecological parameters of vectors is essential to delineate risk areas and predict outbreaks.…”

An update on the mosquito fauna and mosquito-borne diseases distribution in Cameroon

“…aegypti Humans, animal (migrant birds, francolin, calao, rapace, Passeriformes, pigeons, mammals) Garoua, Maroua, Ngaoundere, Buea, Bertoua, Yaoundé, Douala [ 96 ] Rift Valley fever Rift Valley fever virus Aedes spp., Culex spp. Humans, goats, sheep, cattle, gazelles, buffalo Countrywide (in all regions of the country) [ 19 , 21 , 30 , 92 ] Other viruses Tiko virus , Kumba virus , Semlinki virus , Okola virus , Tahina virus , Onyong nyong virus , Ilesha virus , MIDV , NTAV , WESV , B unyamwera virus , Eret virus , Silbu virus , Tatanguine virus , Osuntu virus , Uganda virus , Sindbis virus , Nkolbisson virus , SPOV Culex spp., Mansonia spp., Coquillettidia spp., Eretmapodites spp. Humans, animals (mammals, birds) Kumba, Obout, Buea, Ebogo, Ototomo, Mbalmayo, Akonolinga, Nkolbisson, Okola, Ofoumselek, Yaoundé [ 28 , 84 , 86 – 90 ] …”

“…The most prevalent include dengue, chikungunya, yellow fever, zika, and Rift Valley fever viruses [ 19 , 21 , 30 , 83 – 91 ]. To date, at least 26 different arbovirus diseases belonging to five families have been reported in Cameroon (see Table 1 ) [ 8 , 21 , 30 , 31 , 81 , 84 , 92 , 93 ]. Among them, 18 arboviruses have been detected in humans [ 86 , 87 , 94 , 95 ], and 14 are transmitted by mosquitoes ( Aedes , Culex , Eretmapodites , Mansonia , and Anopheles ) (Fig.…”

“…Dengue and chikungunya viruses have been reported in major cities such as Yaoundé, Douala, and Garoua, and in some rural settings [ 94 , 98 , 99 ]. Rift Valley fever is less common in humans despite evidence of infections in animals [ 21 , 30 , 92 ] with prevalence of IgG in blood samples varying from 3.4–12.3% in goats and sheep [ 30 , 56 ], 9.3–13.5% in cattle [ 30 , 56 ], and 12.4% in humans [ 21 ]. In general though, arboviral human and animal screenings have just been limited to a few ecological settings in Cameroon.…”