A survey of contagious ecthyma and molecular characterization of Orf virus in sheep and goats in Nigeria (2014-2016)

Abstract

Background: Outbreaks of contagious ecthyma (CE) are frequently reported in sheep and goats flocks in Nigeria with severe clinical outcomes. CE is a debilitating and economically important disease primarily affecting sheep and goats caused by the Orf virus (ORFV). Despite field reports of CE in the country, there is no concise country-wide epidemiological data on the disease and limited genetic data of circulating Nigerian ORFV are available in the public domain. Aim: An epidemiological survey of CE and molecular characterization of ORFV circulating in Nigeria from 2014-2016 Method: Data were collected using questionnaires designed and administered to veterinarians and farmers in selected States of Nigeria. Samples collected during passive surveillance for CE from 2014 to 2016 were analyzed by polymerase chain reaction (PCR). The A32L and B2L genes of circulating ORFV were characterized. Results: Analysis of the questionnaire showed that 69.54% (n=82/118) of the farmers claimed to have experienced CE in their flocks with average morbidity and mortality rates of 25% and 15%, respectively. A total of 113 veterinarians participated in the study, with 69.9% (n=79) familiar with CE and claimed CE causes morbidity rates of 25%-37% and mortality rates of 10%-15% in sheep and goats. Laboratory results revealed that ORFV was detected in 72% (18/25) of outbreak samples analyzed by Real-time PCR. Phylogenetic analysis of A32L and B2L genes revealed that Nigerian ORFV sequences belong to cluster I and II and are similar to viruses from India, Ethiopia and China. Conclusions: This study is the first nationwide epidemiological data on the status of CE in sheep and goats in Nigeria. It is also the first report of molecular characterization of two genes of ORFV circulating and causing outbreaks in small ruminants in the country. This study showed that CE is under-reported, widespread and of economic importance to sheep and goat farmers in Nigeria.