Leishmaniasis - Symptoms, Transmission and Treatment

We used the term leishmaniasis to define a set of diseases caused by parasites of the genus Leishmania. These parasites are present in almost all the continents, with the exception of Australia and Antarctica, having been identified more than 20 species.

Leishmaniasis
Leishmaniasis
 

Leishmaniasis is characterized by the WHO (World Health Organization) as one of the six most important infectious diseases in the world. It is estimated that around 2 million people are affected each year.

Despite the large number of infected patients, Leishmaniasis is considered a disease neglected by the pharmaceutical industry, because it affects mainly the less favored populations, that is, with less purchasing power and less potential to generate profits for these companies. In Brazil, leishmaniasis is present in all states.

Transmission

Although they primarily infect animals, humans can be contaminated if present in an endemic area, either as tourists or as residents.

The transmission of the disease occurs through the bite of an insect, the sandfly of the genus Lutzomyia, which is small enough to cross mosquito nets and screens. It receives several names according to the region where it is found, like mosquito straw, tatuquira, cangalhinha, white wing, hard wing and straw.

There is no direct transmission from person to person. Leishmaniasis is a zoonosis. The mosquito only transmits leishmania if it has stung an infected animal.

The sources of infection are mainly infected wild animals, but the domestic dog can also serve as a host (we use this term to denote the infected being). When a man is bitten by the insect that carries leishmania, he can develop two types of disease: tegumentary leishmaniasis (which affects the skin and mucous membranes) or visceral leishmaniasis or kalazar (which affects the internal organs). What defines whether the patient will have the cutaneous form or the visceral form is the type of leishmania that contaminates it.

Classification and symptoms of leishmaniasis

After the mosquito bite, the protozoan is inoculated into our body and can reproduce locally or spread throughout the body.

1. Cutaneous leishmaniasis or skin shape


More than 90% of the world's cases occur in Saudi Arabia, Iran, Afghanistan, Peru and Brazil. It is characterized by the presence of a painless ulcer on the exposed parts of the body, with a rounded or oval shape, of variable size (from millimeters to a few centimeters) and raised edges. The incubation period (elapsed time between the insect bite and the onset of symptoms) is around 2 to 3 months, but can range from 2 weeks to 2 years.

1.1. Localized cutaneous leishmaniasis: There is usually spontaneous resolution within a time span that varies according to the host's immunity and the type of leishmania involved. There may be more than one lesion at a time (up to 20 lesions) and there is usually good response to treatment.

1.2. Leishmaniasis is a rare form of skin that occurs in only 2% of cases, characterized by the appearance of multiple papular and acneiform lesions (similar to acne), involving various parts of the body, including the face and trunk. hundreds. Initially there are lesions similar to those of the localized form, and thereafter dissemination of the parasite through the blood, leading to the appearance of lesions distant from the bite in a few days. There may be fever, muscle aches, general malaise, and weight loss. It is a form that although more extensive also presents good response to the treatment.

1.3. Leishmaniasis diffuse cutaneous form: rare and severe form, in which the individual fails to generate an adequate immune response to eliminate the parasite. In Brazil it is caused by the species leishmania amazonensis.

There is no ulcer but nodular or plaque lesions covering large extensions of the body, often associated with deformities and that respond poorly to treatment. There are usually large amounts of leishmania in the lesions.

1.4. Mucosal or muco-cutaneous leishmaniasis: corresponds to approximately 3 to 5% of cases of cutaneous leishmaniasis. It is characterized by exacerbated and ineffective immune response, with destruction of the tissues where infection is located and poor response to treatment. It attacks the mucous membranes of the upper airways (nose, mouth) and is painless. It usually arises after healing of a cutaneous lesion, (both spontaneously and by inadequate therapy), through the dissemination of the parasite by blood or lymphatic vessels. However, it can occur without evidence of skin lesion prior to or concurrently with a cutaneous lesion at a distance.

2. Leishmaniosis visceral form


Chronic form characterized by systemic (internal organ) involvement by leishmania, as opposed to the cases described above, in which the disease is restricted to the skin or mucous membranes. In Brazil, leishmania chagasi is the parasite that causes visceral leishmaniasis.

The incubation period varies from 2 to 6 months. The infection can be oligosymptomatic (almost or no symptoms) or moderate to severe, leading the patient to death.

In the initial symptomatic cases, there is anemia, splenomegaly (enlargement of the spleen), hepatomegaly (enlargement of the liver) and fever.

If not properly diagnosed and treated, the disease progresses and significant weight loss, impaired hepatic and renal function, continuous fever, and reduction in the number of platelets and leukocytes can lead to bleeding, bacterial infections, and death.

In the photo to the side, we see a boy with visceral leishmaniasis, where the area where the spleen and liver can be palpated was marked on the pen. Notice how both meet with greatly increased sizes.

Diagnosis

In the case of cutaneous leishmaniasis, the clinical appearance of the skin lesion associated with a compatible epidemiological history can lead to the diagnosis, but it is ideal to use parasitological methods (in which the parasite is investigated in a piece of tissue) for confirmation.

In the case of Visceral Leishmaniasis, the parasitological diagnosis can be made in samples of bone marrow, liver, spleen and lymph nodes.
  • Intradermal Montenegro: test performed with intradermal injection of leishmania antigens (proteins). If the patient has already come in contact with the parasite (is infected or has been), an inflammatory reaction occurs at the injection site. It may, therefore, be positive after successful and negative treatment in the diffuse cutaneous form, since it depends on the individual's immune response. In cases of calazar, the test is negative, becoming positive only after clinical cure.
  • Immunological diagnosis: indirect immunofluorescence (IFN) and ELISA are used. These tests detect anti-Leishmania antibodies circulating in the blood of people who have already come in contact with the parasite. Therefore, they should not be used as an isolated diagnostic criterion in the absence of other clinical and laboratory data.

Treatment

The drugs of first choice for the treatment of Leishmaniasis are Pentavalent Antimony. They should be administered parenterally (ie, intramuscularly or intravenously) for a minimum of 20 days. The dose and timing of therapy vary with disease forms and severity of symptoms.

Its main side effect is the induction of cardiac arrhythmias and is contraindicated in pregnant women in the first 2 trimesters, patients with renal and hepatic impairment, and those taking antiarrhythmic drugs.

Other drugs used in the treatment of leishmaniasis include amphotericin B, paromomycin and pentamidine.

There are vaccines under development in Brazil, already in advanced stages.

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