When temperatures start to rise, the sandfly threat is triggered for our dogs — a small flying insect whose bite transmits a protozoan — Leishmania infantum — that causes a parasitic disease: leishmaniasis.

Dr Cristiana Maghenzani, a veterinary surgeon from Milan, explains that "the infestation mainly affects canids and can, under certain conditions, also be transmitted to humans (zoonosis). Transmission occurs via an intermediate host — the sandfly, or phlebotomus — a very small flying insect, different from the mosquito, that is known to bite from dusk to dawn, that is, during the night-time hours. A sandfly bite is necessary for contagion to occur. There are also other, more remote but plausible, routes of transmission of the disease, such as blood transfusions and the transplacental route."

The highest-risk areas for leishmaniasis

In Italy there are regions considered "at risk from sandflies," but unfortunately the disease is now spreading. Until a few years ago it was essentially confined to coastal areas. Now, however, endemic foci have also been identified in Piedmont (Casale, Turin and Ivrea), Valle d'Aosta, Veneto (especially around Lake Garda), Lombardy (Pavia, Lodi, Cremona) and Trentino.

In general, the entire Mediterranean basin is affected by Leishmania. "The disease manifests itself," Maghenzani continues, "after a long incubation period that can last up to seven years, and presents with a very wide range of symptoms. The reason lies in the dog's immune response: if it responds correctly, it manages to block the spread of the parasite; if it responds by producing antibodies, this instead leads to the formation of immune complexes that are deposited in various parts of the body, giving rise to the symptoms of the disease."

Symptoms of leishmaniasis

The most common symptoms are: enlarged lymph nodes; skin lesions; weight loss; fever; lethargy; enlarged liver and spleen; kidney failure (increased thirst and urination); eye lesions (uveitis); nosebleeds; joint lesions (lameness); alopecia, especially around the eyes, the bridge of the nose, neck, ears and tail. Following the alopecia, a scaly eczema develops that can ulcerate and allow bacteria to take hold (pyoderma).

What can be done to prevent infection?

First and foremost, a combination of strategies should be employed to reduce the risk of sandfly bites. Specific repellents against the insect can be applied, bearing in mind that many of the antiparasitic products used must not come into contact with cats due to their toxicity. It is also important to keep the dog in an insect-protected environment during the night-time hours: indoors, using fine-mesh mosquito nets, environmental repellents and every strategy capable of reducing dog-insect contact.

"Since spring 2012, a vaccine has also been available that is capable of modifying the immune response, shifting it in the direction of effective immunity against leishmania," explains Cristiana Maghenzani. "Before administering this vaccine, it is necessary to make sure the dog is not positive for the infestation by means of a blood test. In the event of a positive result, the manufacturer indicates that vaccination is of no use. Treatment is aimed at halting the action of the parasite, but to this day no drug has been found that is capable of definitively eliminating its presence from the affected animal."

The dog must be kept under monitoring — prophylaxis

In summary, treatment works by eliminating the symptoms but is unable to eradicate the parasite entirely, which is why a positive dog will need to be monitored frequently with specific tests in order to understand how the disease is progressing and to initiate a new course of treatment at the appropriate time.

Compared with the past, drugs are now available for treating leishmaniasis that also allow oral administration, not just injection. The side effects of the drugs are nonetheless present and significant enough to require monitoring of the animal's general condition throughout treatment as well. Regarding transmission to humans, Maghenzani warns: "There is no high incidence of canine leishmaniasis transmitted to humans, but — as a veterinary surgeon — I always recommend careful repellent prophylaxis for positive dogs, precisely to prevent other sandflies from feeding on infected blood and perpetuating transmission through their bites." It is also important to know that leishmaniasis is a notifiable disease on the part of the veterinarian.