Leishmaniasis – one disease, many faces

This disease is caused by Leishmania, single-celled parasites that are transmitted to dogs by a vector (carrier). In this case, the vector is a tropical mosquito known as the sand fly or butterfly mosquito. Leishmaniasis is a zoonosis, which means that the disease can also be transmitted to humans. Leishmaniasis is particularly prevalent in southern Europe, South America, and the Middle East. However, due to global warming, mosquito populations infected with Leishmania have now been found in Austria and Germany. The frequent occurrence of the disease in the Mediterranean region has earned it the name "Mediterranean disease."

Sand flies are mainly active at dusk and are found in large numbers near water. They pick up the pathogen from infected mammals or rodents. The pathogen multiplies in the mosquito before being transmitted to dogs through another bite. The pathogen can also be passed on through mating, from the mother to her offspring, and through blood transfusions. The incubation period (the time from infection to the onset of the disease) can range from several months to several years.

A distinction is made between latent (existing but not apparent) and manifest (clearly recognizable) forms of leishmaniasis. Latent forms of the disease usually remain undetected for years, as the animal shows no symptoms of illness. More than half of all infected dogs, including many imported rescue dogs from southern Europe, show this form of leishmaniasis. Although a positive antibody titer can be detected in these dogs, their immune system usually controls the infection well. Due to the large number of asymptomatic carriers, the spread of the pathogen cannot be monitored.

Animals with manifest disease show a variety of symptoms. The formation of ineffective antibodies, which attach themselves to the pathogens but are unable to act, leads to the formation of so-called immune complexes, which can cause damage to various organs of the body. Skin changes occur very frequently and are usually the first signs observed by owners and are considered highly suspicious of leishmaniasis. Severe hair loss and non-itchy skin inflammation on the edges of the ears, eyes ("spectacle formation") or nose may occur. Other symptoms include lethargy (= sleepiness), fever, vomiting, diarrhea, emaciation, kidney failure, swollen lymph nodes, and lameness due to joint or bone inflammation. However, the symptoms are generally not very specific and can also be caused by a variety of other diseases.

If you notice one or more of the symptoms described above in your dog, you should take it to a veterinarian immediately. If, after a thorough clinical examination and review of the dog's medical history, the veterinarian suspects that your dog may have leishmaniasis, this can only be confirmed by further blood tests or tissue samples. The blood test also serves to rule out other diseases.

There is still no treatment that completely eliminates the pathogen from the infected animal's body. This means that even after successful treatment and control of the symptoms, an animal remains infected for life and must be regularly checked by a veterinarian, as relapses are not uncommon. As a pet owner, you should be aware of the sometimes very high costs associated with medication and the duration of treatment.

The various treatment options depend largely on the severity of the disease and the condition of the animal. Discuss the individual treatment plan for your dog with your veterinarian.

There is no prospect of a complete cure, which is why the prognosis must be cautious. However, modern treatment options can relieve symptoms, allowing even clinically ill dogs to live with the infection for years.

To prevent this disease, the most important thing is to protect your dog from sand fly bites. Where possible, dogs should not be taken to areas where leishmaniasis is present, even when travelling on holiday.

Dog owners travelling south with their dog or living in an area where the insects are prevalent should use spot-on treatments or collars to keep the sandflies away. Furthermore, despite preventive measures, you should avoid riverbanks and stagnant water with your dog, particularly at dusk and dawn.

There is also a preventive vaccination against leishmaniasis, though this is only recommended for dogs living in or being taken to areas where leishmaniasis is present. Whilst the vaccination does not offer protection against infection, it does reduce the risk of the dog developing clinical symptoms. Dogs can receive their initial vaccination from the age of six months. An annual booster vaccination is recommended.

In some countries, such as Spain, the drug domperidone is approved for the prevention of leishmaniasis. It is available in Germany via international pharmacies. Alternatively, your vet’s practice may also be able to repurpose a corresponding drug approved for human use. Seek advice from your vet’s practice regarding your trip.