Vector-borne diseases in cats

Vector-borne diseases (VBDs) are diseases that are carried by vectors such as ticks, fleas, mosquitoes and sandflies. A vector does not cause disease itself but can spread infection by passing on pathogens from one host to another. Due to climate change, increased pet travel and rescue of dogs and cats from other countries, these diseases are becoming more common.

Vector-borne diseases (VBDs) are diseases that are carried by a variety of vectors such as ticks, fleas, mosquitoes and sandflies. Ticks are common parasites that need blood to complete their development and do this by seeking a host and biting. This process can pass on pathogens which are infectious agents, eg bacteria, viruses, and other micro-organisms such as protozoa which can pass on disease.

Lyme disease (also known as Borreliosis) is perhaps the most well-known vector-borne disease that affects humans. Caused by a bacterium (Borrelia burgdorferi) which is transmitted by ticks, it can also affect dogs and cats. Fortunately, cats are usually only affected mildly by VBDs.

Ticks are blood-feeding parasites that spend variable times on their hosts. In the UK ticks are most active in spring, summer and autumn when they are searching and feeding on a suitable host, but can be encountered at any time of year.

• Ixodes ticks are the most important and common ticks in the UK. They can spread diseases such as borreliosis and anaplasmosis. Members of the Ixodes tick family include the sheep or deer tick (Ixodes ricinus), the hedgehog tick (Ixodes hexagonus) and the British dog or fox tick (Ixodes canisuga).
• Less common is Rhipicephalus sanguineus (brown dog or kennel tick). This tick has been carried into the UK from dogs imported from southern Europe. This tick transmits Hepatazoon spp which can infect cats. R.sanguineus cannot live outside in the UK because temperatures are currently not warm enough but can live in centrally heated homes if introduced by pets that have been imported or have traveled abroad.
• Dermacentor species include the ornate dog tick, ornate cow tick or marsh tick. These ticks are seen worldwide. Dermacentor reticulatus is found a few parts of the UK including The Welsh coast, South West and South East England. Dermacentor variabilis (American dog tick) and Dermacentor andersonii (Rocky Mountain wood tick) are seen in southern Europe, North and South America, Africa, Thailand and Australia.
• Amblyomma americanum (Lone Star tick) is mainly seen in North America.

Ticks can pass on bacteria or protozoa. Cats can be infected by the following vector-borne diseases:

• Anaplasmosis (Ixodes ticks)
• Babesiosis (variety of tick species, Ixodes spp in the UK)
• Borreliosis (Ixodes ticks)
• Cytauxzoonosis (Dermacentor ticks, Amblyomma americanum)
• Hepatozoonosis (Rhipicephalus sanguineus)
• Rickettsiosis (Rocky Mountain Spotted Fever) (Dermacentor ticks)
• Tularemia (Dermacentor ticks, Amblyomma americanum)

Fleas can pass on Bartonellosis, flea borne spotted fever, tapeworm and the plague (Asia, Africa, North and South America). Mosquitoes can transmit a wide range of vector-borne diseases including heartworm disease, cutaneous dirofilariosis, and West Nile Fever. Sandflies can spread Leishmaniosis.

Cats can also be affected by cytauxzoonosis – a tick-borne protozoal disease that occurs in the US with sporadic cases in Europe and Africa.

Many cats will not show any signs of infection, but some will be lethargic and have a fever. This can happen sometime after the tick or flea bite so you may not connect the infection with an insect bite. Cats may develop anemia, but this depends on the type of tick involved.

If you notice a tick on your cat, you should safely remove it with a tick removal device and take it to your veterinarian for identification. Your veterinarian may take blood samples to confirm infection.

Prevention is the best way to avoid vector-borne diseases. Your veterinarian will advise you on the best way to control fleas and ticks using long-lasting, spot-on treatments. They will advise examining your cat for ticks after they have been outside, especially during the spring and autumn months when ticks are most active. It is also important to know how to remove a tick correctly so that the whole tick is removed, and mouth parts or other parts of the tick aren’t left inside the cat.

Treatment of any vector-borne disease will depend on the pathogen identified. If a bacterial disease has been found, your veterinarian may recommend antibiotics.

Some diseases are zoonotic – that is they can be passed on from cat to owner. This normally occurs when people are bitten by the relevant vector, but people who have problems with their immune system should be aware of the risk of any infections that their cat can share. This is especially important when importing dogs from overseas.