Tick Prevention Week: What you need to know for companion animals

What are ticks?

Ticks are very commonly found on companion animals, but do you as an owner know how to prevent this? What are the consequences of a tick bite and what do you do if man’s best friend has a tick on him?

Ticks are well known vectors of disease, and can transmit disease from animal to animal, and from animals to humans. It is not ticks themselves that are the main issue, but the infectious pathogens that they can carry. In addition to this, by taking blood meals ticks can cause anaemia, local skin reactions and toxicosis via production of toxins in saliva.

The most common tick affecting companion animals in the UK is the sheep tick or Ixodes ricinus, with the hedgehog tick following behind (Ixodes hexagonus). Other ticks in the UK are the marsh tick (Dermacentor reticulatus) and the brown dog tick (Rhipicephalus sanguineus). For an introduction to ticks, see our article from last week. Here we cover the main tick-transmitted diseases in companion animals.

What diseases do ticks help to spread in cats and dogs?

Lyme Disease

Ticks can transmit Borrelia burgdorferi which causes Lyme disease (Lyme Borreliosis). This disease is zoonotic and dogs, cats, horses and humans can all catch it. Cats appear to have some natural resistance to developing Lyme disease but do sometimes show clinical signs. In the UK, sheep ticks and hedgehog ticks can spread Lyme disease.

Animals can have Lyme disease and display no outward signs, as symptoms vary greatly. In dogs, the most common signs are fever, loss of appetite, painful and swollen joints, inflamed lymph nodes, lameness, and lethargy. Lyme disease can lead to damage of the kidneys, nervous system and the heart and so can be a disease with serious consequences. Facial paralysis and seizures can also occur due to nervous system damage. Diagnosis of Lyme disease is based on exposure to ticks and signs observed. Once diagnosed, antibiotics can then be used to treat Lyme disease. There are also vaccines available.

Ehrlichiosis and Anaplasmosis

Some tick-borne diseases in companion animals can only be diagnosed through blood testing.
Some tick-borne diseases in companion animals can only be diagnosed through blood testing.

Ehrlichiosis is often used to describe infections and disease caused by the Ehrlichia, Anaplasma and Neorickettsia genera of bacteria.

In dogs, ehrlichiosis is caused by the bacteria Ehrlichia canis, and has also been observed in cats. Rarely, this pathogen can be zoonotic and also infect humans, however human ehrlichiosis is usually caused by E. chaffeensis. This disease affects the immune cells of the host, and signs vary based on bacterial strain, immune status of the dog, and any other contraindications such as other tick-borne pathogens. In general, E. canis tends to cause more severe signs than anaplasmosis. Fever, weakness, lethargy, no appetite, enlarged lymph nodes, liver and spleen and weight loss are common as well as many other non-specific symptoms. There are a huge list of signs which can make the disease hard to diagnose without testing.

The bacterium Anaplasma phagocytophilum, formerly known as E. equi, causes anaplasmosis in dogs. This bacterium can also cause anaplasmosis in cats and can infect humans too. The disease cannot spread directly from cats or dogs but by the transfer of infected ticks from pets. Anaplasma platys can also infect dogs. This genus causes fever, lethargy, lack of appetite, weight loss, pale mucous membranes, petechiae (very small burst blood vessels), and enlarged lymph nodes among many other signs. An enlarged spleen, low levels of platelets and anaemia are also common.

The sheep tick and hedgehog tick typically transmit anaplasmosis in the UK and the brown dog tick transmits ehrlichiosis.

Babesiosis (redwater fever)

Babesiosis is caused by the Babesia parasite and can be transmitted by the marsh tick and brown dog tick. The tick carries the parasite, which can then infect the host animal when the tick bites it. Babesiosis can affect livestock, companion animals, and also humans. Pathogenicity varies with strain and luckily the most common strain in Europe B. canis has relatively low pathogenicity. Canine babesia does not cause disease in humans, but B. microti and the bovine pathogen, B. divergens, can.

Initial clinical signs are similar to other tick-borne diseases and include fever, reduced appetite, weight loss, anaemia, low platelet count, enlarged spleen and brown urine. In dogs, this can then progress to hyperthermia, lethargy and lung or kidney disease. Conversely, in cats, the B. felis tends to present with no fever and low-grade signs. There are drugs specific for each Babesia species to treat the disease, as well as anti-protozoal drugs and supportive therapy. Some animals might never get rid of the parasite but will live with a chronic infection.

Babesiosis is not very common in the UK, but can be brought from Europe via ticks on pets. Luckily, outbreaks seem to be limited to small areas and this disease is not currently endemic in the UK.

Spotting, removing and treating ticks on pets

Ticks can be difficult to spot and can range from 1mm to 1 cm in size, but can be easier to detect by running your hands over the body of your pet to notice any bumps that were not there before. You should make sure to groom your dog regularly, as well as after visits to areas of woodland or long grass. You can ensure your companion is on an anti-tick treatment, such as a tablet, spot on, shampoo or special collar during risk periods of year.

For A. phagocytophilum, the transmission of pathogen from the tick takes at least 36 hours. As such, if ticks are removed as soon as they are spotted and animals are checked regularly, you can greatly reduce the risk of disease. This is why it is essential to check your animal very regularly. Sheep ticks are more likely to be picked up in highly vegetated areas, whereas hedgehog ticks can be found in more urban areas. Consequently, it is still important to check your cat or dog even if they do not venture into woodland areas.

If you do find a tick, it must then be removed properly. You can risk the head getting left behind in the skin and causing infection and transmission of disease otherwise. If you are unsure how to remove a tick, visit your vet. You must use special tick removal tweezers. Don’t squeeze the body and use a twisting motion. You can also use the same method to remove a tick from a human. Once removed, check that the entire tick has been removed and discard it properly. You should wash the affected area and monitor for development of a rash. If one does then develop, you should visit your vet or a doctor. Here is a video by the Blue Cross which shows you how best to remove a tick.

Another really useful reference is here from MSD on how to remove ticks and what to do with them once you have. 

References

https://www.msdvetmanual.com/dog-owners/skin-disorders-of-dogs/ticks-of-dogs?query=ticks%20in%20dogs

https://www.langfordvets.co.uk/media/2391/anaplasma-phagocytophilum.pdf

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4324656/

https://www.msdvetmanual.com/dog-owners/disorders-affecting-multiple-body-systems-of-dogs/lyme-disease-lyme-borreliosis-in-dogs

https://cvbd.elanco.com/diseases/tick-borne-diseases/babesiosis

https://www.lymediseaseaction.org.uk/about-ticks/tick-borne-diseases/