Epidemiology of Rift Valley Fever Virus and West Nile Virus in Livestock Populations and Their Public Health Implications in the Afar Region, Northeastern Ethiopia
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Date
2025
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Addis Abeba University
Abstract
Ethiopia faces heightened risk of Rift Valley fever (RVF) and West Nile virus (WNV) outbreaks due to proximity to endemic countries (Kenya, Somalia, Djibouti), climatesensitive conditions (heavy rainfall, flooding), climate change, unrestricted livestock movement, and widespread mosquito vectors. Regions like Afar, with tropical ecosystems, are particularly vulnerable, mirroring trends across the Horn of Africa. Despite significant public health and economic threats, the epidemiology of these arboviruses in Ethiopia remains understudied. Therefore, the general objective of the study was to investigate the epidemiological status of Rift Valley Fever and West Nile viruses, along with their associated risk factors, in livestock populations and to assess the public health importance of these diseases in the Afar pastoral region of northeastern Ethiopia. A total of 736 serum samples were collected from 224 cattle, 155 camels, 144 sheep, 121 goats, and 92 donkeys in the Amibara and Haruka districts. The detection of anti-RVF nucleoprotein antibodies of Rift Valley Fever virus and anti- West Nile virus antibodies were performed using the ID Screen® Rift Valley Fever and West Nile competition multispecies ELISA kits. A total of 150 human participants (60 livestock owners, 40 animal health workers and paraveterinarians, and 50 public health professionals) were involved in the KAP study. The overall eroprevalence of RVF was 22.0% (162/736; 95% CI: 19.41–24.79%). The seroprevalence was significantly higher in goats (42.2%, 95% CI: 39.61–44.99%)
compared to that of cattle (14.3%, 95% CI: 11.74–17.09%), sheep (21.5%, 95% CI: 18.91– 24.29%), or camels (30.97%, 95% CI: 28.38–33.76%) (P < 0.001). The study showed that seropositivity for IgG antibody to RVF infection was associated with locality and species of animal. Goats were two times more likely to be seropositive for RVF infection than cattle (OR: 2.3, 95% CI: 1.462–3.574, P = 0.001). Livestock in the Kealatburi sub-district were five times more likely to be seropositive for RVF infection than those in the Halidegei sub-district (OR: 5.074, 95% CI: 3.066–8.396, P = 0.001). Among 736 tested livestock
serum samples, 50.7% (373/736) showed anti-WNV IgG antibodies evaluated using the ID screen® WNV competition multispecies ELISA kits (95% CI: 47%–54.4%; P < 0.01). The seroprevalence was higher (p<0.01) in donkeys (76.1%), followed by camels (69.1%), cattle (52.2%), goats (34.7%) and sheep (25.7%), respectively. The study showed a statistically significant difference of WNV seropositivity between species of animals (OR:1.5, 95%CI =1.038-2.212). Donkeys were (OR: 6.447, 95% CI = 3.888-10.688) seven times more likely to be seropositive for WNV infection than sheep (p < 0.01). The study also revealed 9.1%, 95%CI= 8.86-9.29) seroprevalence of co-circulation of RVF and WNV. High 32/155 (20.7%) seroprevalence of co-circulation was seen in camels followed
by goat 14/121(11.6%), cattle16/224(7.14%) and sheep 5/144(3.5%) respectively and higher 41/421(9.7%) seroprevalence of co-circulation was observed in Amibara district than Haruka district. Camels were seven times (OR: 7.016, 95% CI = 2.639-18.653) more likely to be seropositive for the co-circulation than sheep (p =0.000). Of the participants, 29.3% (44/150) believed zoonotic diseases spread through animal-based food or mosquito bites, while 63.3% (95/150) expressed insecurity about infections like Rift Valley fever, West Nile fever, or other zoonoses. This study found substantial knowledge gaps, a low level of risk concern, and high behavioral practices regarding zoonotic disease. Animal health workers had higher mean scores of knowledges of Rift Valley fever, West Nile fever and other zoonotic disease 27.3 ± 10.9 than public health professionals and livestock farmers/owners at p< 0.05. Mean score statistical difference was also observed among Illiterate, primary education, and secondary and above educational status groups. In conclusion, the present study showed that eropositivity of different species of livestock to RVF and WNV is an indication of its widespread occurrence of RVF and WNV in the study area, domestic livestock, especially in large herds, can serve as useful sentinels for the infections and warrants the need for further investigation on molecular epidemiology
of RVF and WNV in livestock, their potential zoonotic significance to the pastoral communities and understanding of the vectors in transmission of the viruses in the study area in order to design a feasible control strategy.
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Keywords
Afar Region, MEDICINE::Social medicine::Public health medicine research areas::Epidemiology, KAP, Livestock, Rift Valley, fever, Seroprevalence, West Nile Virus, Zoonoses