Decrease in milk yield associated with exposure to bluetongue virus serotype 8 in cattle herds

Area of Science:

• Veterinary Virology
• Animal Production
• Epidemiology

Background:

• Bluetongue virus serotype 8 (BTV-8) infection in cattle leads to decreased milk yield and fertility.
• Quantifying these economic impacts is crucial for evaluating vaccination efficacy.
• Previous studies have not fully assessed the milk yield losses associated with BTV-8 natural outbreaks.

Purpose of the Study:

• To quantify the mean milk yield reduction in naïve herds following natural BTV-8 challenge.
• To determine the duration and cumulative milk loss before and after disease detection.
• To evaluate the impact of neighboring infected herds on milk yield reduction.

Main Methods:

• Utilized mixed linear models to analyze milk yield data from French cattle herds during the 2007 BTV-8 outbreak.
• Adjusted for known factors influencing milk production.
• Assessed effects of BTV-8 exposure over a six-month period relative to disease detection dates.

Main Results:

• BTV-8 exposure caused a significant milk yield decrease for six months (2 months pre- to 4 months post-detection).
• Cumulative milk yield loss exceeded 3% of annual production.
• Herds detected later showed earlier milk yield reductions, suggesting delayed clinical sign recognition.

Conclusions:

• BTV-8 infection imposes substantial economic losses through reduced milk yield in cattle.
• The extent of milk loss is influenced by the timing of herd detection and regional disease incidence.
• Findings underscore the importance of early BTV-8 detection and control measures for mitigating economic damage.