What is Leishmaniasis?
Leishmaniasis is a disease caused by a parasite called Leishmania infantum, which is transmitted by sand flies. The disease is not endemic in the UK, thus affected animals seen at NDSR have almost always travelled overseas. Leishmaniasis is very common in other parts of the world – for example in the South of France around 80-90% of dogs can be infected.
Dogs in the UK can only readily transmit disease to other dogs, or humans, by transfer of blood. In the UK we do not have the sand fly which transmits the disease in natural situations, making risk of natural transmission from an infected dog very low.
Infection with Leishmaniasis involves initial infection from a sand fly, followed by an immune response from the dog. The dog’s immune response can contain the infection, preventing active disease, for months-to-years; it can take up to 7 years from the point of infection before signs of disease develop.
What are the signs of Leishmaniasis?
The signs of Leishmaniasis reflect the distribution of the parasite. They commonly include skin problems (especially around the head and pressure points), enlarged lymph nodes and spleen, eye problems, weight loss, lethargy, reduced appetite, nose bleeds and vomiting and diarrhoea.
There are many common blood test abnormalities seen in Leishmania infection – although none of these are specific for the infection.
How is Leishmaniasis diagnosed?
When dogs are infected, they develop antibodies to the infection. When the disease escapes the relative control of the immune system, the antibody levels typically become very high, and demonstration of the Leishmania parasites across the body becomes possible (either by direct observation under the microscope, or detection of the DNA of the parasite).
Often a combination of tests is required to diagnose the infection: including antibody tests (titres/serology) and tests to demonstrate the parasite (PCR, microscopy).
It is also important to understand which parts of the body are affected, and what other treatments might be necessary for an individual patient. Further blood tests to check blood cells and chemicals (haematology and biochemistry), urine tests and blood pressure assessment might all be required.
How is Leishmaniasis treated?
Treatment is indicated when a dog has active infection which is making it unwell. Treatment usually causes prompt improvement, but the infection does not go away entirely. Following treatment for a month, long term tablets are required to help keep the infection at bay. The treatment should make the dog feel better, and normalise all the symptoms, but it is very likely that the disease will recur again within a few years, when it can again be treated with a month’s medication.
What is the outlook (prognosis)?
Leishmania is considered a lifelong infection. Repeated treatments are likely to be required to control the problem most fully. It is important to monitor affected dogs regularly for evidence of recurrence of active disease, as more rapid intervention should ensure a better long term outcome. One of the most serious consequences of Leishmaniasis is kidney failure, which is often associated with a poor outlook. Prompt treatment should reduce the likelihood of kidney failure developing.
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