The ticks themselves can cause allergic reactions, or can cause infections at the site of the bite if they are removed improperly. Lots of ticks can also lead to anaemia.
The major risk of ticks, however, is in the transmission of infectious disease. These include:
Lyme disease (Borreliosis)
This is the main risk from the tick bites in the UK, for dogs as well as for humans – in a study 2.4% of ticks found on UK dogs were carrying Lyme disease. The clinical signs include recurrent lameness, lethargy and fever, but not the classic ‘bullseye’ skin lesion seen in people. If left untreated Lyme disease can also lead to more serious conditions such as kidney disease and heart failure. Rapid removal of attached ticks will help limit the spread – most ticks have to attach for more than 24 hours to transmit Lyme disease.
Babesia Canis (Babesiosis)
Usually seen in dogs returning from Europe, Babesia has now been diagnosed in some UK dogs that have not travelled. Babesiosis is caused by a tiny parasite (known as a protozoa) which lives inside red blood cells. Lethargy and anaemia are common signs, and affected dogs may die. These clinical signs are also associated with many other conditions, so as babesiosis is rare it may be difficult to diagnose quickly. Rapid removal of attached ticks will help limit the risk of babesiosis – most ticks have to attach for more than 24 hours to transmit the disease.
Anaplasmosis is caused by a bacterium called Anaplasma phagocyophilum. The disease also affects cattle, sheep and horses, but in dogs, anaplasmosis leads to fever, anorexia, joint pain and swelling. Occasionally, neurological signs may be seen. Signs can last for about a week, and the prognosis is very good with treatment.
Ehrlichiosis is a bacterial infection that affects the white blood cells. It is rare in the UK, but is common in Europe, the USA and Africa, so travelling dogs are especially at risk.
In dogs, the signs of ehrlichiosis can include fever, anorexia, weight loss, stiffness and prolonged bleeding. Dogs can appear to improve, but may harbour a chronic form of the infection without treatment. Prognosis with treatment is very good.