Leishmaniosis in dogs
The prevalence of canine leishmaniosis in the Autonomous Community of Madrid and in most of the Spanish Autonomous Communities is around 7-8% (COLVEMA), although there are some Spanish cities where this figure is far exceeded (Córdoba 25%, Málaga 35%, Barcelona 18%). Dogs are at permanent risk of contracting the disease. The proliferation of Phlebotomus due to the climate change increases the number of infected dogs. In the Autonomous Community of Madrid, a Surveillance and Prevention Program for canine Leishmaniosis was stablished in 1983.
Leishmaniosis transmission in dogs
Traditionally, the main transmission form is directly from sandfly to dog, although there are recent evidences describing vertical transmission (from bitches to puppies) in dogs and horizontal transmission through sexual contact.
In this context, special care must be taken when traveling with a dog, either from an endemic area to a free zone, or vice versa, since if prevention measures are not taken, animal movements can help to spread the parasite.
Symptoms of leishmaniosis in dogs
The incubation period of canine leishmaniosis can vary between 3 and 18 months. Exceptionally, the disease can remain silent for several years. Some dogs are resistant and, even if they are bitten by parasitized sandflies, they will never show symptoms of the disease as long as they are properly fed and not subjected to stress. This resistance is probably genetically determined and can cause the development of asymptomatic parasite carriers (apparently healthy dogs infecting sandflies when bitten and spreading the disease). It is therefore desirable to carry out annual veterinary controls to determine if the animal is a carrier of the parasite.
Although leishmaniosis can affect virtually any kind of dog, there are differences in breed, sex or age, being German shepherds and boxers, male, and younger than 3 or older than 8 years old more susceptible to the disease.
Canine leishmaniosis is a multisystemic disease with a highly variable range of clinical manifestations (ranging from mild self-limiting local skin lesions to systemic fatal diseases) and host immune responses. There are two types of leishmaniosis in dogs: visceral and cutaneous. Each type affects different areas of the dog's body. The first most common clinical symptom is the loss of hair, especially around the eyes, ears and nose. As the disease progresses, the dog loses weight.
Lymphadenomegaly and excessive nail growth (onychogryphosis), as well as non-healing skin wounds, especially on the head and legs in areas where the dog is in contact with the ground when lying or sitting, are common. Muscular atrophy, lethargy, lameness or joint inflammation, epistaxis, nose-digital hyperkeratosis, palpebral or conjunctival lesions may also be observed. When the disease becomes chronic, in many cases the illness can lead to complications related to renal failure.
Leihsmaniosis prevention in dogs
Since the primary vector is the sand fly, control and avoidance of these insects is important. If the dog does not receive any kind of protection, it has a risk of up to 20% of get infected. This risk increases if the animal lives in rural and peri-urban areas, in warm regions and when it remains out of the house at nightfall.
- It is advisable to do annual veterinary checks on the dog. It is very important to know if the dog lives or has lived in an endemic area, if it has been exposed to the vector, or if it has received treatments with collateral immunosuppressant effects. The anamnesis is completed with the description of the clinical signs that the owner has observed in his dog and may be compatible with canine leishmaniosis. It is advisable to perform a specific serological test after the vector activity season (mid-late October).
- It is advisable to periodically apply repellents to the dog (always following the instructions from a veterinarian), in order to protect them from mosquito bites, such as the use of necklaces and anti-parasitic pipettes. The latest technological breakthrough is a necklace with a proven effectiveness of 95% against the bites of sandflies. Similarly, long-acting insecticides, insecticidal contact paints, or mosquito nets can be used in the resting areas of the dogs (i.e. kennels).
- It is advisable to prevent the dog from sleeping outside the house during the night, or in places where they are more likely to be bitten by the vector.
- Due to the possibility of vertical transmission of the disease, sterilization may be considered as a prophylactic measure.
- It is very important to follow the recommended preventive measures at all times (necklaces, pipettes, insecticides) regardless of whether the animal is ill and symptomatic or not, to avoid the transmission of the parasite from the dog to a new sand flies, which could infect people or animals.
- There is a vaccine available against canine leishmaniosis. It is indicated for the active immunization of dogs from 6 months of age which have given a negative result in the diagnostic tests against Leishmania. It reduces the risk of infection in the dog and the severity of the symptoms in case of subsequent contact with the parasite. Check with your veterinarian for the availability and grade of protection this vaccine provides.
Leishmaniosis diagnosis in dogs
Serological tests are one of the most commonly used diagnostic methods. It should be noted that this kind of approach is not a reliable method to detect the disease in early stages, since the level of antibodies may be very low or the disease may be in the process of incubation. There are a few "on site tests" that give a result in just 10 minutes. The veterinarian will take a small blood sample and the kit will detect if anti-Leishmania antibodies are present. They usually have a good efficacy, but they are not a 100% reliable methods, since they also do not report the infection status nor the number of protozoa present.
Parasitological examination consists of taking a sample of the bone marrow or tissue from the lymph nodes and examining them under the microscope. This would be the most reliable sample, but its extraction is more complicated and requires a more complete laboratory equipment.
Molecular techniques (PCR) are reliable, although they are more expensive
Leihsmaniosis treatment in dogs
Leishmaniosis is a disease that causes death to most affected dogs if they do not receive treatment and subsequent health monitoring. Treatments against Leishmania only minimize the symptoms and lengthen the life of the animal, but they rarely eliminate the parasite. However, treatment limits the risk of transmission, improving the quality of life of the animal. Treatment should be constant throughout the life of the animal, requiring periodic controls. In certain circumstances the euthanasia of the animal may be recommended.
Treatment strategies vary by the geographic area, the strain of Leishmania and the symptoms shown by the dog. The drugs used in leishmaniosis treatment are:
- Meglumine antimoniate (prevents the multiplication of the parasite).
- Other drugs are Amphotericin B, Pentamidine, Aminosidine, Miltefosine and Allopurinol (alters the RNA of the parasite).
To date the most commonly used drugs in Europe are meglumine antimoniate, with or without allopurinol. After the resolution of the clinical symptoms, allopurinol is often used as a maintenance therapy, often for life, as it has been shown to prevent relapses.
Such relapses are common after treatment, and many drugs have important side effects. In recent years the treatment lenght has been increased; this may be due to the resistance developed by the parasite against commonly used drugs. Therefore and in order to avoid the progression of such resistance, different drugs should be used in dogs as in humans.
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