Epidemiological Studies on African Horse SicknessDisease in Sudan

Abstract

African horse thickness disease is one of the most prevalent viral diseases that threaten the equine breading in Sudan.A cross-sectional study was conducted in four states (Northern, River Nile, Khartoum and Southern Darfur) fromSeptember 2016 to October 2017 to determine thesero-prevalence and to investigate the risk factors for Africanhorse sickness (AHS) in Sudan. A total of 920equines (590horses and 330 donkeys) were randomly selected andsampled. Competitive Enzyme Linked Immuno-Sorbent Assay(c-ELISA) was employed to detect antibodies to AHS virus.The overall sero-prevalence was 72.2 %, while it was 80% inhorses and 58.2% in donkeys. The univariate analysis ofassociations of potential risk factors with sero-prevalence ofAHS showed statistically significant (p≤ 0.05) results withstate (χ2 = 47.434, p<0.001), species (χ2 = 50.163,p<0.001), sex (χ2 = 26.206, p<0.001), housing (χ2 = 26.477,p<0.001), vaccination (χ2 = 44.466, p<0.001), breed (χ2 =57.256, p<0.001), water bodies (χ2 = 26.271, p<0.001),Cullicoides (χ2 = 42.658, p<0.001), ticks (χ2 = 23.608,p<0.001), activity of animal (χ2 = 41.435, p<0.001),awareness of owner (χ2 = 25.639, p<0.001),age (χ2 =20.186,p<0.001), health score(χ2 = 12.038, p<0.001),pregnancy (χ2 = 3.249,p = 0.0355),and infection with otherdisease(χ2 = 14.637,p<0.001). However, the risk factors ofpresence of other animals and pervious infection with AHS didnot show statistically significant (p>0.05) associations.Furthermore, in the multivariate analysis onlystate (OR =4.909, p = 0.017), breed (OR = 2.532, p = 0.004), species(OR = 3.776, p = 0.017), water bodies (OR = 2.172, p =0.033),and vaccination(OR =17.298, p< 0.001)were found tobe statistically significantly≤ (p0.05) associated withsero-prevalence of AHS.The other study was carried out during fall 2018 and 2019 to estimate the prevalence of the disease in horses, to detect the virus in Cullicoides(Diptera: Ceratopogonidae) pools and assess the contribution of major risk factors for the occurrence of the disease in horses. Whole blood samples (184) were collected randomly from horses from two governorates in Khartoum state and three provinces in Southern Darfur state. In addition, 1916 insects in 18 pools, the pool range 70- 150 non-engorged female different species of Cullicoides biting midges were collected from Khartoum governorate and tested for the presence of ribonucleic acid of African horse sickness virus (AHSV) using one-step reverse transcriptase polymerase chain reaction technique. The results revealed that the overall prevalence of AHSV in horses was 38.6% and from the 18 pools of Cullicoides the virus was detected in 6 pools (33.3%). Furthermore, in the univariate analysis, risk factors such as locality (p = 0.00), age (p = 0.01) and sex (p = 0.01) were significantly associated with the prevalence of AHSV in horses. However, the breed of horses did not show statistically significant associations (p>0.05). In the multivariate analysis,locality (OR = 28.2, p = 0.00) was found to be the most statistically significant risk factor for the occurrence of AHSV. The results of this study highlight that the overall prevalence of AHSV was high in the areas surveyed. There were statistical significant differences of the prevalence of AHSV between the various sites in Khartoum state and South Darfur state (p ≤ 0.05).