# Epidemiological Insights into Maedi-Visna Virus in Algeria: First National Seroprevalence Survey and Risk Factor Profiling in Sheep Herds

## TL;DR

This study is the first to assess maedi-visna virus in Algerian sheep, finding higher infection rates in females and certain regions, and suggesting genetic resistance in some animals.

## Contribution

The first national seroprevalence survey of maedi-visna virus in Algeria reveals novel insights into sex-based disparities and potential genetic resistance.

## Key findings

- Overall seroprevalence of maedi-visna virus in Algerian sheep is 9.07% with significant variation by sex, age, and region.
- Females show much higher seropositivity (20.44%) compared to males (3.68%), likely due to prolonged herd retention and vertical transmission.
- Seronegative animals in high-prevalence herds suggest potential genetic resistance, a novel finding requiring further investigation.

## Abstract

This first national seroprevalence study of maedi-visna virus (MVV) in Algerian sheep herds demonstrates critical insights into a pathogen that causes chronic disease and economic losses globally. Through the analysis of 1400 sheep across four regions via indirect ELISA, we observed an overall seroprevalence of 9.07% (95% CI: 7.57–10.57), with significant disparities by sex (females: 20.44% vs. males: 3.68%; p < 0.05), age (peak in 1–5-year-olds: 10.43%; p = 0.019), and geography (Central region: 3.36% vs. East: 0.86%; p < 0.05). The females’ prolonged herd retention and vertical transmission risks, coupled with industrialized farming in high-prevalence regions, drive these trends. Notably, breed and farming systems showed no association (p ≥ 0.08), challenging existing paradigms and suggesting region-specific transmission dynamics. Strikingly, seronegative animals in high-prevalence herds hint at genetic resistance, a novel finding warranting exploration. This study fills a critical gap in North African SRLV epidemiology, emphasizing the need for ewe-centric control measures, targeted surveillance, and genetic research to curb transmission. The absence of prior national data elevates its significance, offering actionable strategies for resource-limited settings and advancing the global understanding of MVV heterogeneity. These findings underscore the urgency of context-specific interventions and provide a foundation for future studies on host–pathogen interactions and resistance mechanisms in endemic regions.

Maedi-visna virus (MVV), a small ruminant lentivirus causing chronic multisystemic disease in sheep, poses significant economic burdens due to reduced productivity and a lack of effective treatments. Despite its worldwide prevalence, epidemiological data from Algeria remain absent. This first national seroprevalence study aimed to elucidate MVV distribution, risk factors, and transmission dynamics in Algerian sheep herds. A cross-sectional survey of 1400 sheep across four regions (East, Center, West, South) was conducted, with sera analyzed via indirect ELISA (IDvet). Risk factors (geography, age, sex, breed, farming system) were evaluated using chi-square tests and Cramer’s V. Overall seroprevalence was 9.07% (95% CI: 7.57–10.57), with significant variation by sex (females: 20.44% vs. males: 3.68%; p < 0.05), age (1–5 years: 6.86% vs. <1 year: 0.29%; p = 0.01), and region (Central: 3.36% vs. Eastern: 0.86%; p < 0.05). Notably, no association was found with breed or farming system (p ≥ 0.08), contrasting prior studies and suggesting region-specific transmission dynamics. Females exhibited heightened seropositivity, implicating prolonged herd retention and vertical transmission risks. Geographic disparities highlighted industrialized farming in central Algeria as a potential transmission amplifier. Strikingly, seronegative animals in high-prevalence herds hinted at genetic resistance, warranting further investigation. This study provides foundational insights into MVV epidemiology in North Africa, underscoring the need for targeted surveillance, ewe-focused control measures, and genetic research to mitigate transmission. The absence of prior national data elevates its significance, offering actionable frameworks for resource-limited settings and enriching the global understanding of SRLV heterogeneity.