What is leishmaniasis?
Leishmaniasis is a serious parasitic disease of dogs caused by a flagellated protozoan.
These parasites are transmitted to our dogs by female sandflies, small winged and biting insects that feed on the blood of vertebrates. Sandflies, which can easily be confused with mosquitoes, are very active at nightfall and at minimum temperatures between 18°C and 22°C. Thus, leishmaniasis is most prevalent in regions with a Mediterranean climate, in southern Europe (Greece, Spain, Portugal, Italy) and in southern France.
In France, Phlebotomus perniciosus is the main vector of the parasites responsible for leishmaniasis.
How can a dog get leishmaniasis?
Leishmania infantum, the protozoan in question
If there are different species of leishmania in the world, it is Leishmania infantum which is responsible for leishmaniasis in Europe. This parasite is a protozoan (one-celled organism) that lives and multiplies within certain cells of its host.
The parasite can infect dogs, foxes, humans and exceptionally cats.
Contamination by the bite of a sandfly
Leishmania infantum exists in 2 forms:
- the promastigote form that multiplies in sandflies.
- the amastigote form that develops in vertebrates.
When a female sandfly bites the animal (or the human), she injects the parasite - then present in her salivary glands in promastigote form - to her new host.The latter is then phagocytosed by the macrophages present in the skin. The promastigotes then become amastigotes and multiply within these cells from which they then escape by rupture of these cells. Promastigotes are phagocytosed by other macrophages and thus invade hematolymphopoietic organs including the bone marrow. Once these different organs are affected, the parasites reach the skin, kidneys, pancreas, digestive tract, eyes, bones, joints, etc.
It is when a new sandfly bites the infested animal or man that it ingests the blood of its victim contaminated by the parasite. Once in the digestive system of the sandfly, the amastigote forms then transform into promastigote forms to multiply there before migrating to the salivary glands of the insect. Thus parasitized, the sandfly can then infect a new host.
Leishmaniasis, a disease transmissible to humans
Leishmaniasis is a zoonosis. Understand by this that it is a disease that affects both animals and human beings. A dog carrying leishmania in his dermis, whether he is sick or not, can indirectly transmit the disease to his masters. But, only the sandfly can transmit the disease. It must then become infected on contact with the dog and then bite the human being so that the latter can be contaminated. On the other hand, a dog suffering from leishmaniasis cannot contaminate a human being by its only contact, without the intervention of the insect.
The regions most at risk in Europe and France
You will have understood that the presence of leishmaniasis in a given territory is dependent on the presence of sandflies in the environment.
As the sandflies vectoring the parasite like heat, they are mainly present in the south-eastern regions of France and in Corsica. With global warming, they also tend to spread towards the South-West and the Rhône Alpes region.
In Europe, leishmaniasis more generally affects the entire Mediterranean region: Greece, Spain, Portugal, Italy.
In temperate regions, sandflies are particularly active from April to October.
What are the symptoms of leishmaniasis?
It can take a long time between the bite of the sandfly (which can also go unnoticed) and the onset of the first symptoms of the disease so that the link between the two can be complicated to establish . The incubation time for leishmaniasis varies from 3 months to 8 years after the bite of the sandfly!
In addition, the multiplicity of organs affected and the great heterogeneity of its symptoms makes it a disease that is quite difficult to recognize without the use of specific examinations.
Sandflies usually choose a hairless area such as the inside of the ears or the top of the nose to sting their victims.The sting can go completely unnoticed or give rise to an “inoculation chancre” which appears 1 to 3 weeks later. At the site of the bite, the dog's skin then becomes red, scaly and swollen before ulcerating and covering with a scab to heal completely in 3 to 5 weeks. The inoculation chancre corresponds to the multiplication site of Leishmania at the very site of the bite.
Leishmaniasis can then manifest as:
- various skin lesions such as the appearance of hairless areas of varying shapes and extents (alopecia), the formation of large scales (piece of dead skin that detaches from the epidermis), ulcerations , pustules and nodules,
- discoloration and ulcerations of the nose which can cause epistaxis (nose bleeding),
- weight loss linked to a decrease in the dog's appetite and muscle wasting, especially of the muscles of the face,
- eye damage,
- abnormal claw growth that elongates, deforms and cracks,
- an enlarged lymph nodes,
- chronic diarrhea with the presence of digested blood in the stool,
- signs of kidney and liver failure,
- signs of anemia,
- lameness,
Some dogs may be infected with the parasite but never develop any symptoms or only develop them after several months or years due to a decrease in the effectiveness of their immune system. These infected but not sick dogs constitute a parasite reservoir for humans and other animals.
Predisposed breeds?
If all dogs can be parasitized by Leishmania, some breeds of dog would have a natural immunity against the disease when others are more vulnerable.The Ibizan hound would thus have an effective immunity against leishmaniasis while the Boxer has an ineffective immune system against this disease.
What treatment for leishmaniasis?
Treatment does not cure a dog with leishmaniasis but only slows the progression of the disease and controls its symptoms.
This is a long and expensive treatment that mainly relies on daily injection of meglumine antimoniate for 3-4 weeks followed by lifelong daily treatment with oral allopurinol .
This specific treatment can be supplemented by symptomatic treatments and may be accompanied by side effects (impaired kidney function).
It must be accompanied by regular monitoring of the animal by the veterinarian.
How to protect your dog?
Vaccination
There is a vaccine against leishmaniasis in dogs. It requires 1 to 3 initial injections then an annual reminder. Puppies can be vaccinated from their 6 months but not at the same time as for the other diseases against which they are commonly vaccinated: distemper, leptospirosis etc.
If this vaccine is not 100% effective, it nevertheless reduces the risk of infection by 4.
On the other hand, the vaccine should not be performed on dogs already infected with the parasite. It is therefore necessary to have your dog tested before having it vaccinated.
Preventing sandfly bites
For animals (vaccinated or not) as for humans, avoiding sandfly bites remains the best option for preventing leishmaniasis.
To do this, it is recommended:
- not to take the dogs out at dusk during high-risk periods, from April to October, if you live in a geographical area where the sandfly is present,
- not to mow your dog because the coat has a relative protective effect against insect bites,
- connect fans in the room where your dog sleeps during high-risk periods (sandflies are afraid of the wind),
- to avoid opening the windows at night in periods and areas at risk. Mosquito nets are not very effective against the entry of sandflies into houses due to their very small size,
- to hunt for “sandfly niches”: eliminate stagnant water reservoirs in the garden and the house, fill the crevices in the walls, etc.
- to use a repellent product against sandflies in areas at risk. They are now available in necklaces or spot-on pipettes. Ask your veterinarian for advice to make sure that the chosen product is effective against the insect and that it is not contraindicated in your animal.Please note that these products are not 100% effective and do not exempt you from taking the aforementioned precautions.
Warning!
All repellent products against sandflies that can be used in dogs are very toxic to CATs.
Note carefully!
Repellent collars against sandflies are only effective one week after their placement on the dog. If you go to a high-risk area with your dog, during your summer holidays for example, you will have to plan ahead!
How to recognize a sandfly?
The sandfly is a small midge (between 2 and 3 mm), barely visible to the naked eye, with 2 wings and 6 legs and with a hairy appearance. The flight of the sandfly makes no noise and is done in small leaps of one meter interspersed with rest and at low height. Its bite is painful, unlike that of a mosquito.
Photo credit: CDC/ Frank Collins [Public domain]