Seroprevalence and Risk Factors of African Horse Sickness in Three Agroecological Zones of Cameroon

Abstract

African horse sickness (AHS), a highly fatal arbovirosis of equines is endemic in sub-Saharan Africa. However, its epidemiology is poorly known in Cameroon. This study aimed to investigate the prevalence profile and risk factors of African horse sickness in Cameroon. Horse sera were subjected to the ELISA blocking test for the determination of antibodies against African horse sickness virus, and positive samples were submitted to capture ELISA to determine the presence of antigens. Potential risk factors associated with AHS were assessed based on the information collected in the field. The chi-square test and the odd ratio (OR) were used to test the association between serology and the different variables. Of the 336 sera obtained, 198 were positive for antibodies with a prevalence of 58.93% (CI: 53.67–64.19). From the 198 positive sera to antibodies, only one revealed positivity to antigens with a prevalence of 0.51% (CI: 0–1.5). Agroecological zone I (94.31%, CI: 91.83–96.79, OR: 34.92) was significantly ( p < 0.05 ) associated with the higher risk of disease dissemination than agroecological zone II (66.67%, CI: 61.63–71.71, OR: 4.21) and agroecological zone III (32.18%, CI: 27.18–37.18; OR: 1). Males (63.59%, CI: 58.44–68.74, OR: 1) were significantly ( p < 0.05 ) affected than females (50.42%, CI: 45.07–55.77; OR: 0.58). Horses of more than 8 years (76.00%, CI: 71.43–80.57) were significantly ( p < 0.05 ) at risk than young animals of less than 3 years old (32.14%, CI: 27.15–37.13, OR: 0.15). This study highlights a high seroprevalence of antibodies of African horse sickness in Cameroon. Agroecological zone, age, and the importation of horses were highly associated with the distribution of disease at the national level.

Prevalence of African Horse Sickness in Donkeys in Three Northern Regions of Cameroon

“…Despite the possible loss of maternal immunity, some young colt could have had no contact with the virus while older donkeys had more opportunities to be exposed to the virus. Similar observations were reported by [5] in Senegal and [23] in Cameroon where old animals were more likely come into contact with the virus.…”

“…Also, animals recovering from natural AHSV infection usually develop strong immunity against infection of the same serotypes [4] and partial immunity against infection of heterologous serotypes [33] within 8 to 12 days post infection and vaccination can protect for up to 4 years [3]. High AHS sero-prevalence have been reported in horses (>80%) in parts of Cameroon including the Northern regions [23] and the high detection rate of anti-AHS antibodies recorded in the present study has revealed that AHS is endemic in the country and particularly among domestic equine species. Therefore, the absence of AHS antigens reactions among the positive anti-AHS antibody reactors in this study suggests that the donkeys had developed an active humoral immunity following exposure to the natural disease a long time ago and were no longer actively infected.…”

“…This is well supported by previous findings [22]- [24], [26], [42] that observed no significant variation in sero-positivity in the two sex groups. However, horses kept in modern systems and male horses which are preferentially used by shepherds to accompany cattle herds in search of pastures and during transhumance were at increasing risk of contact with AHS virus than the horses in the traditional systems and female horses, respectively [23]. Unlike horses, there is no preferential use of donkeys based on sex and AHS virus vectors do not have blood meal preference with respect of sex and age.…”

“…A sample size of 199 donkeys was estimated [29] based on previous reports on the prevalence of AHS in horse of 84.76% in Cameroon [23] with a confidence interval of 95% and precision set at 5%. The study used a stratified random technique.…”

“…AHS is endemic in sub-Saharan Africa and the estimated sero-prevalence of antibodies in horses of 86.6% [20], 81.0% [21], 46.% [22] and 58.93% [23] was reported in Nigeria, Gambia, Ethiopia and Cameroon, respectively. Also, estimated anti-AHS antibodies prevalence in donkeys of 24.6% in Ethiopia [24], 73% in Uganda [25] and 72.6% in Burkina-faso [26] has been reported.…”