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Performance deficits in SRLV-infected sheep quantify progressive disease severity.
Andrew W Illius1, Andrzej Junkuszew2, Paulina Nazar2
1Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, UK.
Preventive Veterinary Medicine
|April 7, 2026
Summary
Small Ruminant Lentivirus (SRLV) infection in sheep causes progressive production losses, impacting lamb growth and ewe lifespan. Older infected sheep pose the greatest transmission risk, suggesting selective culling as a management strategy.
Area of Science:
- Veterinary Virology
- Sheep Production Medicine
- Lentiviral Disease Research
Background:
- Small Ruminant Lentivirus (SRLV) causes Maedi-Visna disease in sheep.
- Disease management strategies often focus on eradication, which can be costly.
- Understanding the progressive impact of SRLV is crucial for effective flock management.
Purpose of the Study:
- To quantify the physiological and production costs associated with SRLV infection over time.
- To assess the relationship between infection duration and disease severity.
- To evaluate selective culling of under-performing ewes as a disease management strategy.
Main Methods:
- A five-year longitudinal study of a Polish sheep flock.
- Bi-annual serological testing to determine SRLV status.
- Analysis of performance measures including mortality, growth rates, and ewe productive lifespan.
Main Results:
- SRLV infection did not affect ewe prenatal reproductive traits.
- Infected lambs experienced increased mortality and reduced growth rates.
- Ewes showed reduced productive lifespan and output, with deficits increasing with infection duration.
- Older ewes with longer infection durations exhibited substantial performance deficits.
Conclusions:
- SRLV infection imposes significant, progressive production losses in sheep flocks.
- Infectiousness likely increases with disease severity and infection duration.
- Selective culling of under-performing older ewes may reduce production losses and disease transmission.
