Canine leishmaniasis or leishmaniosis is a zoonotic disease (one which can be spread from animals to humans) carried by phlebotomine sand flies. It is endemic or common in some parts of Europe but has also been identified in the USA and Canada.
There are different strains of Leishmania and transmission can vary depending on the strain, although this is typically from sandfly to dog and occurs when the sand fly feeds on the dog. The most common strain is Leishmania infantum.
Although transmission is generally from female sandfly to dog, the disease can also be passed via the placenta from an infected mother to her puppies, this is thought to be the case in many cases of leishmania in dogs in North America. It can also be spread via blood and other bodily secretions.
Leishmaniasis in dogs is caused by intracellular protozoan parasites which infect macrophages and then reproduce.
Dogs may carry the disease for months or years before showing any clinical signs. Some dogs therefore act as carriers without exhibiting any symptoms.
Signs of leishmania in dogs can be very varied as they depend on the type of immune response the parasite causes. This can vary between breeds, with some breeds such as
- German Shepherds
- Cocker Spaniels
- Foxhound (especially common in this breed in the USA)
may have a greater likelihood of developing the clinical disease.
The disease is multisystemic and can therefore affect most body systems. The most commonly reported symptoms are:
- Skin lesions, including abnormal nail growth
- Gradual weight loss
- Reduced appetite
- Lethargy and exercise intolerance
- Eye abnormalities
- Epistaxis (bleeding from the nose)
- Swollen lymph nodes
Other less common signs include:
- Polyurea (increased urination) and polydipsia (increased drinking)
- Gastrointestinal signs such as vomiting and colitis
Diagnosis of Leishmania in Dogs
To diagnose the disease in dogs with leishmania there are several tests which can be used. The most common of these include:
- Blood tests (complete blood count (CBC), biochemistry)
- Specific tests using serology such as ELISA (Enzyme Linked Immunosorbent Assays), indirect immunofluorescence assays and direct agglutination assays
- Cytology (examination of cells) from lymph nodes, joint fluids, skin scrapings or spleen
- PCR (Polymerase Chain Reaction) tests on DNA is the most reliable technique for diagnosis.
To date there is no consistently curative treatment for canine leishmaniasis. Some treatments can lead to clinical improvement, but relapses are common. Some of the drugs used to treat leishmania in dogs are not approved for dogs in the USA, these include:
- N-methylglucamine antimoniate (a pentavalent antimonite) administered by injection (75-100 mg/kg daily under the skin for 4-8 weeks)
- Miltefosine (2 mg/kg/day orally for 4 weeks)
It is recommended that both of these be combined with allopurinol (10 mg/kg orally twice daily) to achieve the best results. By using the drugs in combination the length of treatment can be reduced.
Generally allopurinol is tolerated well over long treatments. Allopurinol can also be used alone at the same dose, but longer treatment periods may be necessary.
In areas where leishmania is endemic it is wise to routinely test your dog at your local veterinary clinic for the disease. If it is found to be infected the chances of controlling the condition are much better if it is treated in the early stages of the illness.
Due to the lack of proven treatments for leishmania the mainstay of stopping disease lies in preventative methods and avoiding exposure to sand flies. These can include:
- Use of insecticides to repel sand flies from dogs
- Testing of female dogs before breeding
- Euthanasia of infected dogs in areas where the disease is not endemic
- Vaccination (available in Europe and Brazil but do not entirely eliminate the risk of dogs contracting the disease).
Examples of insecticides which have a repellent effect on sand flies are permethrin, deltamethrin and imidacloprid and these can be found either in the form of a “spot-on” drops such as K9 Advantix or a collar such as the Scalibor collar. Care should be taken to use the correct dose or size appropriate for your dog.