Mandefro Mesafint, Ibrahim Saddam Mohammed, Sibhatu Demeke, Kassa Nebiyou, Emiyu Kemal, Debebe Kebede, Dessalegn Bereket, Birhan Mastewal, Bitew Molalegne
Metema District Livestock and Fishery Resource Development Office, Metema, Ethiopia.
College of Veterinary Medicine and Animal Sciences, University of Gondar, Gondar, Ethiopia.
Front Vet Sci. 2024 Dec 13;11:1392893. doi: 10.3389/fvets.2024.1392893. eCollection 2024.
Peste des petits ruminants (PPR) is an acute or subacute, highly contagious, and economically important, transboundary disease of small ruminants caused by Peste des petits ruminants virus (PPRV).
The objective of this study was to determine the seroconversion rate in PPR vaccinated flock of sheep (Sekela district) and the seroprevalence of PPRV in unvaccinated flocks of sheep and goats (Yilmanadensa district).
A cross-sectional study was conducted from January to March 2022 in two selected districts of West Gojjam zone, Ethiopia. Multistage cluster sampling was used to select sampling units by successively selecting districts, kebeles, and villages purposively based on their accessibility and vaccination status. Individual animals were selected haphazardly mimicking simple random sampling. Accordingly, a total of 660 blood samples were collected. Out of this, 300 sheep were vaccinated 4 months prior to sampling using the Nigerian 75/1 strain-based freeze-dried live attenuated PPR vaccine and 360 small ruminants (288 sheep and 72 goats) were unvaccinated and assayed for anti-PPRV antibodies using commercial c-ELISA.
The post-vaccination herd immunity was 76.66% (95% CI: 71.46-81.34), which is slightly lower than the threshold herd immunity recommended by the PPR global control and eradication strategy, which is set to be 80%, to efficiently break the epidemiological cycle of the virus. Seroprevalence of PPRV in unvaccinated sheep and goats was 3.61% (95% CI: 1.94-6.1), indicating the possible circulation of PPRV in the area. Although small ruminants develop solid immunity following natural infection in endemic countries, the infection of naïve animals allows continuous circulation of the virus.
In light of the accumulating evidence of low post-vaccination herd immunity in small ruminants in Ethiopia, the undergoing PPR vaccination strategy needs to be reevaluated to achieve the desired herd immunity at any time ultimately aiding the eradication goal by 2030.
小反刍兽疫（PPR）是由小反刍兽疫病毒（PPRV）引起的一种急性或亚急性、高度传染性且具有重要经济意义的小反刍兽跨边境疾病。
本研究的目的是确定接种小反刍兽疫疫苗的绵羊群（塞凯拉区）的血清转化率以及未接种疫苗的绵羊和山羊群（伊尔马纳登萨区）中小反刍兽疫病毒的血清流行率。
2022年1月至3月在埃塞俄比亚西戈贾姆州的两个选定地区进行了一项横断面研究。采用多阶段整群抽样方法，根据可达性和疫苗接种状况，依次有目的地选择地区、凯贝勒和村庄作为抽样单位。随机选择个体动物，模拟简单随机抽样。据此，共采集了660份血样。其中，300只绵羊在采样前4个月使用基于尼日利亚75/1株的冻干减毒活小反刍兽疫疫苗进行了接种，360只小反刍兽（288只绵羊和72只山羊）未接种疫苗，并使用商业c-ELISA检测抗小反刍兽疫病毒抗体。
接种疫苗后的群体免疫力为76.66%（95%置信区间：71.46 - 81.34），略低于小反刍兽疫全球控制和根除战略建议的群体免疫阈值80%，该阈值设定为有效打破病毒的流行病学循环。未接种疫苗的绵羊和山羊中小反刍兽疫病毒的血清流行率为3.61%（95%置信区间：1.94 - 6.1），表明该地区可能存在小反刍兽疫病毒的传播。尽管在流行国家，小反刍兽在自然感染后会产生稳固的免疫力，但未感染过的动物被感染会使病毒持续传播。
鉴于埃塞俄比亚小反刍兽接种疫苗后群体免疫力较低的证据不断积累，需要重新评估现行的小反刍兽疫疫苗接种策略，以便随时实现理想的群体免疫力，最终有助于实现2030年的根除目标。
