Sheep ticks are widespread external parasites found in rural and wild environments. These tiny creatures pose a concern for various animals, especially livestock, and can also affect humans and pets.
What Are Sheep Ticks?
Sheep ticks, scientifically known as Ixodes ricinus, are arachnids. Adult males are approximately 2.4 to 2.8 mm long, with females slightly larger at 3.0 to 3.6 mm. An engorged female can reach up to 11 mm. These ticks are typically reddish-brown, but engorged females turn light gray. They lack eyes and possess a hard dorsal shield, or scutum, which covers the entire body in males but only partially covers females and nymphs.
Sheep ticks thrive in habitats with high humidity, such as woodlands, grasslands, heathlands, and rough pastures, especially where hosts graze. They are widely distributed across Europe. These blood-feeding parasites require a blood meal at each active stage of their life cycle to develop.
The Life Cycle of Sheep Ticks
The life cycle of Ixodes ricinus involves four stages: egg, larva, nymph, and adult. Each active stage (larva, nymph, and adult) requires a blood meal to progress or, for adult females, to produce eggs. The entire life cycle typically spans about three years, though it can be shorter if conditions are optimal.
Ticks employ a strategy called “questing” to find hosts; they climb onto vegetation and wait for an animal to pass by, detecting hosts through changes in temperature, carbon dioxide, humidity, and vibrations. After feeding for several days, the engorged tick detaches from its host and drops to the ground to molt or lay eggs. An engorged female can lay a batch of 1,000 to 2,000 eggs in vegetation, with larvae hatching approximately eight weeks later.
Health Risks to Animals and Humans
Sheep ticks can transmit pathogens, posing health risks to both animals and humans. In sheep, common tick-borne diseases include tick-borne fever, louping ill, and tick pyaemia. Tick-borne fever, caused by Anaplasma phagocytophilum, leads to high fever, listlessness, and a suppressed immune system, making affected animals more susceptible to other infections. Louping ill is a viral disease of the central nervous system that can cause fever, muscle tremors, an unsteady gait, and death in sheep. Tick pyaemia primarily affects lambs, causing abscesses in joints, tendons, muscles, and sometimes the brain, leading to severe lameness and weight loss.
For humans, sheep ticks are vectors for Lyme disease, caused by Borrelia burgdorferi, with symptoms that can include a “bull’s-eye” rash, fever, headache, fatigue, and muscle or joint aches. If left untreated, the infection can spread to the joints, heart, and nervous system, leading to severe complications. Other infections transmitted by Ixodes ricinus include anaplasmosis and babesiosis. Anaplasmosis symptoms often resemble flu-like illness, including fever, headache, malaise, and muscle pain. Babesiosis, caused by Babesia parasites, infects red blood cells and can lead to fever, chills, sweats, and anemia, with severe cases able to result in jaundice or dark urine.
Controlling and Preventing Infestations
Managing sheep tick infestations involves strategies for both livestock and individuals. For sheep, regular inspections help detect and remove ticks promptly. The application of acaricides, chemical agents that kill ticks, is a control method administered through dips, pour-ons, or sprays. Pasture management techniques, such as rotational grazing, can reduce tick populations. Breeding tick-resistant livestock may also offer a long-term solution.
For humans and pets, preventing tick bites is important. When outdoors in tick-prone areas, wearing light-colored, long-sleeved clothing and tucking trousers into socks helps spot ticks and prevents them from reaching the skin. Using insect repellents containing DEET or picaridin on exposed skin and clothing can provide effective protection. After spending time outdoors, perform thorough tick checks on clothing, skin, and pets. If a tick is found attached, remove it carefully using fine-tipped tweezers or a specialized tick removal tool, grasping the tick as close to the skin as possible and pulling upwards slowly without twisting or crushing it.