Disease risks for the travelling pet: Leishmaniasis

Diagnosing and treating leishmaniasis in cats and dogs

source: Lise Trotz-Williams and Luigi Gradoni
In Practice vol 25 no 4, April 2003
starts p190, 6 pages long

Several thousand pets have travelled between mainland Europe and Britain since the Pet Travel Scheme (PETS) was introduced in 2000. Pets are treated for ticks, tapeworms, and rabies, but can still contract other diseases, including leishmaniasis, which can be fatal, and can also affect humans.

Leishmaniasis refers to syndromes in animals affected by Leishmania protozoan parasites. Leishmania infantum is more common in the Mediterranean, and has also been found in North America. Leishmania chagasi is more common in Latin America. Dogs are the main reservoir for both types of Leishmania, since it is rarer for cats to be affected. Animals become infected through being bitten by sandfly carrying the parasite. The infection can spread to several organs in cats and dogs that do not have a strong enough immune system to protect them. Around half of dogs that become infected will go on to develop clinical leishmaniasis. The disease has a reported incubation period of between a month and seven years. Symptoms vary according to which organs and tissues have been invaded, and some animals may simply show dermatitis. Pets may develop 'spectacles' as the skin round the eye is affected, and their muzzles may also show signs of the disease. Cats and dogs that are seriously affected can lose their appetites, lose weight, and become depressed. The variety of possible clinical signs is wide, and includes osteomyelitis, colitis, and pericarditis, so diagnosis is not easy, but leishmaniasis should be considered when pets have travelled to areas where it is endemic.

Diagnosis can be carried out in a number of ways, including smears from skin lesions. Parasites may not be easily detectable in some cases, and diagnosis may also be carried out through testing for antibodies to leishmania. Such tests may not be accurate until a while has elapsed after the pet has become infected.

There is some risk to humans, especially children and people with HIV. However, humans in southern Europe generally appear to be at low risk of acquiring clinical leishmaniasis, despite high risks of infection.

Treatment tends to suppress clinical signs, and pets may suffer relapses, since parasitological cures are difficult to achieve. Euthaniasia may be recommended in areas where leishmaniasis is endemic, due to the risk of the disease being passed on, and of drug resistance developing. However, since sand flies and other vectors are unknown in the UK, treatment is more of an option there. Megaglumine antimoniate and allopurinal are usually given, with allopurinol continuing over the longer term, though there are other treatments, such as allopurinol given alone. Long-term intermittment treatment appears to be the best option to prolong survival rates.

Cats appear to be more resistant to leishmaniasis than dogs, and they tend to be less severely affected when they are infected. Most affected cats simply suffer from skin conditions. Treatment is the same for cats and dogs.

Leishmaniasis is especially common in Mediterranean countries, such as France, Spain and Portugal. The highest rates have been found in the Balearic Islands, Crete, Malta and Corsica. The risk varies from one locality to another, and from one season to the next. The risk is highest when there are most sand flies about, especially between May and September. Sandflies tend to be especially active from dusk to dawn, so an important precaution is to keep pets indoors at this time. Collars impregnated with deltamethrin (Scalibar collars from Intervet) can also help to protect dogs from sandfly bites and infection.