Mange: Epidemiology and ivermectin efficacy in goats and application of zero-inflated negative binomial regression in Uba Debre Tsehay, southern Ethiopia

Abstract

Mites are one of the most common and widely distributed ectoparasites of goats in Ethiopia, contributing to major burdens in livestock productivity in the country. Between February 2021 and July 2021, this study was conducted to estimate the prevalence of mange mites, assess the potential risk factors, identify the species infesting goats, and evaluate the efficacy of ivermectin in naturally infested goats in the Uba Debere Tsehay district of Gofa Zone, Southern Ethiopia. A cross-sectional study, longitudinal field efficacy, and questionnaire survey were conducted. A total of 384 goats suspected of having mange were scraped for mite prevalence and count. The mite count data were analyzed using zero-inflated negative binomial (ZINB) models with explanatory variables. The ZINB models indicated that a substantial proportion of the observed zero mite count reflected a failure to detect mites in suspected goats, meaning that the estimated true prevalence was much higher than the apparent prevalence as calculated using a simple proportion of nonzero mite counts. Overall prevalence of mange was 21.87% (84/384) in the study areas. Sarcoptes species (21.09%) and Demodex species (0.78%) were the mite genera identified in this study. Among goats with poor, medium, and good body conditions, mite prevalence was 36.3%, 12.3%, and 10.9%, respectively. Both the prevalence and intensity of infestation were significantly associated with body condition scores, but other risk factors were not. The questionnaire survey indicated that 85.94% of the participants preferred to use modern treatment options (ivermectin 1%, injection) and 76.56% (98/128) respondents replied that ivermectin treatment is effective. Wilcoxon rank-sum test analysis shows that there was significantly (P<0.05) fewer mites counted on goats treated with ivermectin than on untreated goats at each count up to day 56 after treatment. No live mites were found on any treated animal on days 28 and 56. Mixed ANOVA indicated that there was a significant difference within treatment groups. This study showed that mites are one of the constraints to goat production in the study area and ivermectin was highly effective against Demodex and Sarcoptes mites in goats. Hence, there is a need to create awareness about the impact of mange on goat production, and appropriate ivermectin treatment against mites should be implemented.