Calves have lice: how should they be treated? - briefly
Apply a licensed topical insecticide such as pyrethrin or ivermectin according to label dosage and repeat the treatment after 7–10 days to interrupt the lice life cycle. Ensure thorough cleaning of bedding and implement regular herd monitoring to prevent reinfestation.
Calves have lice: how should they be treated? - in detail
Lice infestations in young cattle require rapid identification and a comprehensive control plan. The first step is to confirm the presence of ectoparasites by examining the hide, especially the neck, shoulders, and ventral areas. Adult lice appear as small, grayish insects; nymphs and eggs (nits) are attached to hair shafts. Heavy infestations cause itching, restlessness, hair loss, and can predispose the animal to secondary infections.
Effective treatment combines pharmacological intervention with environmental management. Recommended drugs include:
- Topical pour‑on formulations (e.g., pyrethrin‑based products) applied along the backline from the withers to the tailhead, ensuring full coverage of the skin. Repeat the application after 7–10 days to disrupt the life cycle.
- Injectable macrocyclic lactones (ivermectin, doramectin) administered at the label dose of 0.2 mg kg⁻¹ body weight. These agents act systemically, killing mobile stages that have migrated beneath the coat.
- Oral insecticides (e.g., milbemycin oxime) given at 0.2 mg kg⁻¹, suitable for group treatment when pour‑on application is impractical.
Dosage calculations must be based on the calf’s live weight; under‑dosing promotes resistance. Observe withdrawal periods for meat and milk, adhering to regulatory guidelines.
Environmental control reduces re‑infestation risk:
- Manure removal – clean pens daily and compost or discard waste to eliminate lice pupae that may survive off the host.
- Bedding replacement – use clean, dry bedding; discard any material that has been in contact with infested animals.
- Quarantine – isolate newly acquired calves for at least 14 days, treating any detected lice before integration with the herd.
- Regular grooming – routine brushing dislodges adult insects and nits, facilitating early detection.
Monitoring should continue for at least three weeks after treatment. Re‑examine all animals weekly, focusing on previously affected sites. If lice persist, rotate to a different class of insecticide to avoid cross‑resistance, and consider veterinary consultation for alternative options such as organophosphate dips or newer ectoparasiticides.
Preventive strategies include maintaining optimal nutrition and hygiene, which strengthen the immune response and reduce skin irritation that attracts lice. Implementing a scheduled prophylactic treatment program—typically every 6–8 weeks during high‑risk seasons—maintains herd health and minimizes economic losses associated with reduced weight gain and skin damage.