National Centre of Zoosanitary Vigilance, Ministère de L'agriculture et des Ressources Hydrauliques, Tunis, Tunisia.
Institut de la Recherche Vétérinaire de Tunisie, Tunis, Tunisia.
Vet Med Sci. 2022 Jul;8(4):1671-1682. doi: 10.1002/vms3.818. Epub 2022 May 5.
Bluetongue (BT), a vector-borne disease of wild and domestic ruminants, is responsible for severe economic losses in flocks. To reduce this impact, a surveillance and control plan was implemented in Tunisia. However, the epidemiological situation of BT remains incompletely understood, especially for the circulating serotypes.
The aim of this survey was to determine the seroprevalence, to identify the circulating serotypes and to identify the associated risk factors for bluetongue virus (BTV) circulation in Tunisia using risk-based sampling (RBS).
A total of 3314 blood samples were randomly collected from 67 sectors using risk-based sampling and screened by competitive enzyme-linked immunosorbent assays (c-ELISAs). Out of the 1330 positive samples, 200 samples were analysed by serum neutralization test (SNT) to identify circulating BTV serotypes.
Of 3314 sera, 1330 were c-ELISA-positive (40.1%) for antibodies against the BTV structural protein VP7. The result of SNT showed the presence of BTV-1, BTV-2, BTV-3, BTV-4 and, for the first time in Tunisia, BTV-26. The logistic regression model revealed that older animals had nearly two times the odds of being infected with BTV compared to younger animals. Flocks with a history of BT were almost 1.5 times more likely to be at risk for contracting BTV infection. The flock size, housing indoors and intensive production system were significant protective factors.
High seroprevalence of BTV among sheep was highlighted in Tunisia. The neutralization test showed the presence of the following BTV serotypes: BTV-1, BTV-2, BTV-3, BTV-4 and, for the first time in Tunisia, BTV-26. Age, production system and flock size were important variables associated with BTV infection in sheep. This finding is crucial, as it will allow the adjustment of the BT control programme in Tunisia.
蓝舌病（BT）是一种野生和家养反刍动物的虫媒传染病，对畜群造成严重的经济损失。为了降低这种影响，突尼斯实施了一项监测和控制计划。然而，BT 的流行病学情况仍不完全清楚，特别是对于循环的血清型。
本调查旨在通过基于风险的抽样（RBS）确定突尼斯蓝舌病病毒（BTV）的血清流行率、鉴定循环的血清型，并确定与 BTV 循环相关的风险因素。
使用基于风险的抽样从 67 个区共采集了 3314 份血液样本，并通过竞争性酶联免疫吸附试验（c-ELISA）进行筛查。在 1330 份阳性样本中，有 200 份样本通过血清中和试验（SNT）进行分析，以鉴定循环的 BTV 血清型。
在 3314 份血清中，有 1330 份 c-ELISA 阳性（40.1%），针对 BTV 结构蛋白 VP7 的抗体。SNT 的结果显示存在 BTV-1、BTV-2、BTV-3、BTV-4，以及突尼斯首次发现的 BTV-26。逻辑回归模型显示，与年幼动物相比，年龄较大的动物感染 BTV 的几率几乎高出两倍。有 BT 病史的畜群感染 BTV 的风险几乎高出 1.5 倍。畜群规模、室内饲养和集约化生产系统是重要的保护因素。
突尼斯的绵羊中发现了高血清流行率的 BTV。中和试验显示存在以下 BTV 血清型：BTV-1、BTV-2、BTV-3、BTV-4，以及突尼斯首次发现的 BTV-26。年龄、生产系统和畜群规模是绵羊感染 BTV 的重要变量。这一发现至关重要，因为它将使突尼斯的 BT 控制计划得以调整。
