January 30 is the “World Day of Neglected Tropical Diseases”, a day in which it is intended to make visible a health threat that affects billions of people and animals, a threat that can, and should, be prevented and treated.
There are 20 groups of diseases caused by various pathogens (viruses, bacteria, parasites, fungi…), highlighting two zoonoses in the possible affectation of domestic canids in our country: leishmaniasis, and rabies.
Of these two pathologies, we will focus on Leishmaniosis, an endemic pathology in Spain whose main reservoir is the dog, and other species, such as lagomorphs, can also act as reservoirs.
Leishmaniasis is an active disease that affects healthy animals daily and whose full control is complex.
In the case of rabies, a deadly disease, fortunately the vaccination campaigns in our country, still improvable (some Autonomous Communities do not require their annual vaccination), keep our colleagues, and therefore humans, free from a disease that ends up with the life of the one who suffers it.
Leishmaniosis
The presence of Leishmaniasis in our country experienced a slight decrease in its presentation in the 1940s, mainly due to the decrease in the density of mosquitoes due to the massive use of insecticides and the malaria eradication campaigns, all accompanied by due to a significant decrease in the number of dogs in homes due to the economic recession.
In subsequent decades, unfortunately, the presence of the disease experienced exponential growth.
The cause
The first case of Leishmaniasis detected in companion animals was described by Nicole in 1808; In our country, the first researcher who made a complete description of the disease was Dionisio Álvarez, in the year 1810.
This pathology is due to a flagellate protozoan (unicellular organism with a flagellum or tail) of the genus Leishmania, which can affect vertebrates with the genuine, unique and essential help of a mosquito bite: the Phlebotomus .
To be more exact, we will say that the females of this insect are the only ones responsible for the transmission of the disease, since they are hematophagous (they feed on blood); this feeding characteristic facilitates the transmission of the parasite from a sick animal to a healthy animal.
The female of Phlebotomus is nocturnal, usually acts in humid areas with warm environments and has a certain predilection for rural areas and the outskirts of cities.
Transmission
This disease, also known as “mosquito” manifests itself mainly in Latin America and in Mediterranean countries such as Spain, Portugal, Italy, France, Malta, Greece… and it does so in the seasons in which mosquitoes make their appearance: with rising temperatures.
For leishmaniasis to be transmitted from one animal to another, we need the presence of the following protagonists:
- A sick dog : an animal that, even without showing symptoms of illness, harbors parasitic forms of Leishmania inside it.
- A healthy dog : any dog, breed or non-breed, long or short haired, small or large, can be affected by the bite of a mosquito carrying parasitic forms of Leishmania.
- A mosquito : a single mosquito, a single female of Phlebotom or loaded with infective forms of Leishmania is more than enough for a healthy animal to stop being healthy.
- Parasites : the parasite, during its journey inside the mosquito, transforms to reach its final form before disembarking in the healthy animal.
Clinical aspects
When the parasite penetrates, and subsequently spreads through the animal’s body, it does not usually do so at random, since it has its preferences:
- Through the skin ( Cutaneous Leishmaniasis )
An animal with cutaneous leishmaniasis may present the following signs and symptoms:- Exfoliative dermatitis with alopecia, ulcerations, onychogryphosis (exaggerated nail growth), formation of nodules and pustules, hyperkeratosis, nasodigital depigmentation, scaling and auricular and periocular alopecia, erythematous plaques, dull and brittle hair…
- Due to certain viscera ( visceral leishmaniasis )
Increased abdominal size due to increased liver size (splenomegaly), weight loss, decreased activity… and the kidneys can also be affected, one of the most dangerous conditions for the integrity of the animal.
Apart from the dermatological and visceral symptoms, others may appear such as:
- Localized or generalized lymph node enlargement (symptom present in more than 90% of cases)
- Locomotor disorders (polyarthritis, polymyositis…)
- Cracks in the pads
- Ulcers between the fingers
- Rhinitis, epistaxis (nosebleeds), pneumonia, colitis, conjunctivitis, keratitis…
Diagnosis
The diagnosis of the disease has reached a point of high efficiency thanks to the existence of rapid tests that confirm or rule out the pathology in the animal tested.
More specific tests can and should also be carried out to determine the degree of infection, as well as the possible and diverse organic involvement.
Early diagnosis (at least one specific analysis per year) of the disease is essential to apply a rapid, adequate and effective treatment; If we detect the problem in its early stages, when there is usually no serious visceral alteration, we can ensure that the treatments will manage to keep the problem at bay, even make the disease negative.
Leishmaniasis has gone in recent decades from being a disease that was not compatible with life, and suggested the application of euthanasia, to a process that can be treated and that allows the animal to die due to age and not from the illness.
Treatment
International research on this disease combines its three key elements: the causative agent (the parasite), the transmitter (the sandfly) and the victim (the dog). Scientists devote their efforts to discovering the different types of sandfly females that transmit the disease, the different combinations of components that make up the most effective vaccine, the drugs that control the disease with the least impact of side effects, those that prevent bites of the mosquitoes…
Fortunately, and as we mentioned before, the pharmacological battery for the treatment of leishmaniasis achieves control of the disease in most cases, as long as we follow the treatment guidelines and check-ups prescribed by veterinary health professionals.
Prevention
Currently we have drugs with a proven and repellent action against sandfly females and their undesirable bites, products in the form of necklaces, pipettes, sprays… and also several vaccines.
Despite so many good options, preventive effectiveness NEVER reaches 100%, so it is essential to propose, with a trusted professional, and taking into account the individual characteristics of each animal, the best preventive regimen.
It is fair to comment that the best results are usually obtained by the combination suggested by the veterinarian by combining several of the existing products and means, mainly in those canids in areas of high exposure.
