Cross-sectional serosurvey and associated factors of bluetongue virus antibodies presence in small ruminants of Nepal

Abstract

BackgroundBluetongue (BT) is an infectious, insect-borne viral disease primarily affecting sheep and occasionally cattle and goats. In Nepal, BT is an emerging disease of economic importance. The objective of this study was to estimate the seroprevalence of BT virus (BTV) in small ruminants of two eco-zones of Nepal, Hills and Terai, and to identify the factors associated with virus exposure. We conducted a cross-sectional serosurvey from March 2012 through February 2013 by sampling 318 small ruminants (184 sheep and 134 goats) from seven clusters (villages) of selected vulnerable communities of Chitwan (Terai) and Lamjung (Hills) Districts of Nepal.ResultsOf the 318 serum sample tested, 27.9% [95% confidence interval (CI): 23.1- 33.2] were positive for BTV antibodies (25.0% sheep and 31.3% goats). Bivariate analysis indicated a positive association between seroconversion to BTV and flock size, eco-zone, breed, and contact history with cattle. Additionally, in female sheep and goats, a history of abortion was positively associated with seropositivity to BTV. However, the final multivariable model, after controlling for clustering of animals within the villages, identified only history of abortion and breed as the factors significantly associated with BT seropositivity in female sheep and goats. Based on this model, female small ruminants having a history of abortion were more likely to be seropositive compared to those without such history [Odds Ratio (OR) = 46.14 (95% CI: 11.66- 182.5)]. Exotic breeds were more likely to be seropositive compared to indigenous breeds [OR = 9.04 (95% CI: 3.08- 24.46)] while the risk for BTV seropositivity was not significantly different between indigenous and cross breeds.ConclusionsOur results showed that nearly a quarter of small ruminants in two regions of Nepal were seropositive for BTV, indicating wide exposure of small ruminants to this pathogen. We identified history of abortion and breed as factors significantly associated with the seropositivity of BTV. We recommend that surveillance for BTV infection in Nepal be strengthened and that it would be valuable to enhance the education of farmers about the possible impacts of this disease.

Risk‐based serological survey of bluetongue and the first evidence of bluetongue virus serotype 26 circulation in Tunisia

“…This result can be explained by the fact that in intensive systems, farms have better management of disease prevention and control and biosecurity measures (Gong et al., 2021). Similar results were found in studies conducted in Spain assessing risk for BTV‐1 (Pascual‐Linaza et al., 2014) and in Nepal (Gaire et al., 2014). Furthermore, economic losses due to BT are higher in semi‐intensive farms than in other production systems (Kumar & Pandian, 2020).…”

Seroprevalence and Risk Factors of Bluetongue Virus Infection in Tibetan Sheep and Yaks in Tibetan Plateau, China

“…This rate is higher than the 3.53% reported in yaks in Qinghai Province, China [ 7 ], and 9.3% among the domestic ruminants in Northern Kerala, India [ 3 ]. However, it is lower than the 27.9% prevalence reported in small ruminants in Nepal [ 2 ], 33.13% in sheep and goat in South Bengal [ 9 ], 43.68% in ruminants in Jharkhand, India [ 10 ], 45.20% among domestic ruminants in the highlands of Nepal [ 11 ], and 96.7% in buffaloes and cattle in selected provinces in Lao People's Democratic Republic [ 12 ]. Many factors, including the diagnostic methods, climatic conditions, geographical conditions, species/breeds, sample sizes, and sanitation, may contribute to such differences.…”

“…The first case of BT in sheep in India was reported in 1964 [1]. This pathogen was firstly recorded in sheep in China in 1979 [2]. Because BTV can cause a severe hemorrhagic disease with high morbidity, it is listed as a notifiable disease by Office International des Epizootics (OIE) [1].…”

Livestock host composition rather than land use or climate explains spatial patterns in bluetongue disease in South India

“…Densities of exotic and cross-bred sheep also had a positive effect on outbreak numbers. Such breeds are known to be more susceptible to clinical signs of BT in India 57 and Nepal 17 than indigenous local breeds and so infection is more likely to result in a recorded outbreak. Indigenous local sheep breeds in Asia also show antibody prevalence against BT with few disease effects 58 , 59 , although sporadic clinical cases have been observed in these breeds since the 1980’s 20 , 60 .…”

“…Prior studies of Culicoides -borne disease patterns in tropical endemic areas focussed largely on climatic factors, primarily temperature and rainfall 14 . More recent studies have incorporated land use 15 , vegetation 16 and hosts 17 as potential explanatory factors, although the relative contribution of these factors to BT impacts are rarely quantified together.…”