Canine leishmaniasis treatment: pharmacological and nutritional update

Generally, canine leishmaniasis is transmitted by a vector, the insect genus Phlebotomus, which injects the parasite Leishmania infantum when it bites a dog.

Leishmania infantum is an obligate intracellular protozoan that lives and reproduces in different organs, resulting in systemic involvement and the animal’s progressive deterioration.

• Leishmaniasis is considered endemic throughout the Mediterranean region and dogs are the main reservoir of the disease.
• Generally, canine leishmaniasis is transmitted by a vector, the insect genus Phlebotomus, which injects the parasite Leishmania infantum when it bites a dog.
• Leishmania infantum is an obligate intracellular protozoan that lives and reproduces in different organs, resulting in systemic involvement and the animal’s progressive deterioration.

Canine leishmaniasis: drug treatment and nutritional needs

The treatment for canine leishmaniasis currently consists of:

- Meglumine antimoniate (Glucantime) 75–100 mg/kg once a day or 40–75 mg/kg twice a day. It is administered for 4 weeks, but this can be extended by 2–3 weeks if complete improvement is not achieved in the first 4 weeks.

- Allopurinol 10 mg/kg orally twice a day for 6–12 months (can be extended for longer).

It has been noted that the patient’s progress can be improved by complementing the drug treatment for leishmaniasis with a diet adapted to the dog’s needs. Specifically, researchers studied the effects of a diet with the following characteristics:

• High antioxidant content to stimulate the immune system.
• Appropriate protein levels for adult animals, with a high biological value, to help recover muscle mass and minimise negative effects on the kidney.
• Excellent digestibility and palatability to help with weight gain.
• Reduced content of purine bases to prevent the formation of xanthine calculi, a side effect associated with administering allopurinol for canine leishmaniasis.

Clinical signs of canine leishmaniasis: skin lesions

Leishmaniasis has a systemic or visceral involvement affecting several organs and systems, so it should be included in most differential diagnoses. The majority of dogs (80%) develop dermatological signs, which correspond to the most frequently diagnosed clinical manifestation. In addition, most dogs with leishmaniasis also develop general, nonspecific symptoms such as apathy, fever and muscle atrophy, among others. Later, the level of involvement may evolve and generate problems associated with the general compromise of various organs such as epistaxis, renal problems, hepatomegaly, and so on.

We can summarise that there are two types of clinical picture:

• In locations where the parasite multiplies: localised nonsuppurative granulomatous inflammation.
• Different anatomical locations: through immune complex deposition.

Why do some dogs infected with leishmaniasis remain asymptomatic?

Dogs display different manifestations of Leishmania infection, some develop very obvious clinical signs, while others do not present any. It has been observed that these phenotypes are a reflection of the animal’s immune response, and that this response influences the progression of the infection and the response to the canine leishmaniasis treatment:

• Infected dogs with clinical signs: nonprotective, humoral immune response that is unable to control the infection (Th2).
• Infected dogs with no clinical signs: protective, cellular immune response (Th1).

So, testing each dog’s immune system may be important when assessing the response to the canine leishmaniasis treatment. Various tests are available to characterise the immune profile of dogs with Leishmania. A publication by Dr. Lluís Ferrer et al. concluded that the best test panels are a combination of serology (detection of antileishmania IgG1 and IgG2 antibodies and total IgG), delayed hypersensitivity skin testing (DHT) and cytokine analysis (gamma-interferon, tumour necrosis factor) after Leishmania antigen stimulation.

We can use this information to classify dogs living in endemic areas into four groups:

• Healthy, uninfected dogs
• Infected but resistant dogs (Th1 response)
• Dogs with patent leishmaniasis (Th2 response)
• Infected dogs with a Th2 response that will go on to develop the disease