Tick Infestation in Sheep: Welfare and Control

Tick Infestation in Sheep: A Growing Welfare Concern

The sheep tick (Ixodes ricinus) is the most important ectoparasite affecting sheep in upland Britain, with expanding populations linked to climate change, increasing deer populations, and changes in land management. Ticks cause direct welfare harm through blood feeding and secondary skin reactions, and transmit multiple serious diseases that represent major welfare and production threats.

Biology of Sheep Ticks

Ixodes ricinus has a three-host lifecycle spanning 3-4 years. Larvae, nymphs, and adults each take a single blood meal before moulting or egg-laying. Ticks quest for hosts from vegetation, using CO₂, heat, and humidity as cues. Peak activity occurs in spring (March-June) and autumn (August-October). Mild, wet conditions favour tick populations; climate change is expanding both the geographic range and active season.

Direct Effects

Heavy tick burdens cause anaemia, irritation, and hypersensitivity reactions in heavily infested lambs. Tick worry — persistent behavioural irritation from tick attachment — reduces grazing time and growth rates. Tick attachment sites can become infected, causing tick pyaemia (Staphylococcus aureus, spread by tick feeding), which causes arthritis, liver abscesses, paralysis, and death in lambs.

Tick-Transmitted Diseases

Louping ill: A flavivirus causing neurological signs — incoordination, convulsions, and death in up to 60% of untreated sheep. Vaccination is available and highly effective.

Tick-borne fever (Anaplasma phagocytophilum): Causes fever, depression, and immunosuppression lasting 1-2 weeks, increasing susceptibility to secondary infections including pasteurellosis and tick pyaemia.

Babesiosis (Babesia divergens): Primarily affects cattle but can infect sheep; causes haemolytic anaemia.

Control Strategies

• Acaricide treatment: Dip, pour-on, and injection formulations using permethrin, organophosphates, or amitraz. Treatment timing before peak tick activity reduces burden
• Pasture management: Swaling (burning), bracken control, and grazing management reduce tick habitat. Deer management reduces tick reservoir populations
• Vaccination: Louping ill vaccine protects against the most serious tick-transmitted neurological disease
• Parasite monitoring: Regular flock monitoring allows timely intervention when tick levels rise

Integrated Tick Management

No single approach controls ticks effectively. Integrated tick management combining acaricide use, habitat management, vaccination, and monitoring achieves best welfare outcomes. Farmer knowledge of tick activity patterns on their farm guides treatment timing and reduces unnecessary acaricide use, supporting responsible use principles.

Zoonotic Risk

Ixodes ricinus transmits Borrelia burgdorferi (Lyme disease), tick-borne encephalitis virus, and Anaplasma phagocytophilum to humans. Farm workers and rural communities face significant tick exposure. Personal protective measures and tick checking after fieldwork reduce human infection risk.

This page is part of the Animal Welfare Hub — providing evidence-based information to improve the lives of animals. Return to home.