Livestock Welfare
Bovine Nasal Bot Fly Welfare in Cattle
Managing Oestrus ovis and related nasal bot flies that affect cattle and sheep welfare.
Key Facts
- Nasal bot flies (Oestrus ovis primarily) deposit larvae in the nostrils of sheep and occasionally cattle
- Larvae migrate through nasal passages causing severe irritation and inflammation
- Affected animals show head-shaking, nasal discharge, sneezing, and respiratory distress
- Heavy infestations can cause secondary bacterial infections and meningitis
- Seasonal treatment with macrocyclic lactones significantly reduces larval burdens
Welfare Considerations
Nasal bot infestation represents a welfare challenge that is often underestimated because behavioural signs — head-tossing, stamping, bunching together — are attributed to other causes. The presence of larvae in nasal passages causes significant pain and distress. Animals cannot access forage normally, lose body condition, and suffer chronic discomfort throughout the fly season.
Neurological complications occur when larvae migrate beyond the nasal sinuses. Secondary bacterial infections compound suffering. Treatment with appropriate macrocyclic lactones at strategic times (early autumn and spring) kills larvae and provides significant welfare relief. Farmers should monitor affected animals closely and implement prompt treatment protocols.
What You Can Do
- Work with your vet to establish a strategic parasite control programme
- Treat cattle and sheep with appropriate macrocyclic lactones at recommended times
- Monitor for signs of nasal bot infestation during summer and autumn
- Ensure animals have access to shade and shelter to reduce fly exposure
- Report unusual neurological signs promptly — they may indicate larval migration