Leishmaniasis (cutaneous, visceral): what is it and what is the cause?

What is leishmaniasis?

Leishmaniasis is a disease caused by a protozoan. It is classified as an anthropozoonosis. This means that this disease is characteristic of animals, but can be transmitted accidentally to humans .

In the case of leishmaniasis, the parasitic protozoan is transmitted between animals (dogs, rodents) through the bite of certain types of mosquito. When the infected mosquito bites a human being, the disease is transmitted to man.

Leishmaniasis can manifest in 3 different ways and be caused by up to 30 types of protozoa of the genus leishmania.

In urban environments the animal most affected by the disease is the dog, which also serves as the main host of the parasite.

The disease is considered to be extremely neglected.

According to DNDi ( Drugs for neglected diseases) – or the Drugs for Neglected Diseases Initiative, in Portuguese – this is because leishmaniasis is prevalent in poor regions and there is no interest from the pharmaceutical industry in investing in new medicines.

What are the types of leishmaniasis?

There are 2 different types of leishmaniasis. Cutaneous leishmaniasis, also called cutaneous leishmaniasis, mainly affects the skin and, in certain cases, mucous membranes. Visceral leishmaniasis, also called kala-azar, affects the internal organs. This variation is dangerous and can have serious consequences for the patient.

Understand each type:

Cutaneous or cutaneous leishmaniasis (LT)

This type of disease affects the skin. It forms wounds and ulcers and is the most common version of leishmaniasis, being caused by almost 20 of the protozoa of the genus leishmania. The wounds can be large and painful.

Like other types, it is transmitted by the infected straw mosquito, which can contract the parasite by biting other infected animals.

The most dangerous variation of cutaneous leishmaniasis is mucocutaneous leishmaniasis . While the first affects only the surface of the skin, this type affects the mucous membranes and cartilage, generating ulcers.

Next to the skin, the inside of the mouth and nose are affected, as well as the cartilage that makes up the nose and ears.

This type of disease can cause serious facial deformities, practically devouring the lips, ears or nose entirely.

Usually the protozoan that causes this type of leishmaniasis is Leishmania braziliensis , but in some rarer cases it can be caused by other types of leishmania protozoa.

Facial deformities can be extremely serious, and wounds are an opening for contamination with bacteria that can cause infections.

Leishmaniose visceral (LV)

The visceral version of leishmaniasis is also known as kala azar . This type is the rarest and the most dangerous.

It is caused by three different protozoa: Leishmania donovani , Leishmania chagasi and Leishmania infantum .

Visceral leishmaniasis causes ulcers in the patient’s internal organs, especially those that have high concentrations of immune cells.

This is because these protozoa infect phagocytic cells (immune cells responsible for the process of involving and eliminating infectious microbes).

When protozoa are “swallowed” by immune cells, they begin to reproduce and eventually break the cell, returning to the bloodstream and spreading throughout the patient’s body.

The spleen, liver and bone marrow are some of Organs most affected organs. If left untreated, this condition leads to death.

In some animals, such as the dog, the protozoan may not cause any symptoms. In these cases, it is not a danger to the animal itself, but a mosquito that bites can become contaminated with the parasite, restarting the cycle.

Canine Leishmaniasis

Leishmaniasis is a more common disease in animals than in humans. In cities, it is especially common in dogs, while in wild areas, the disease mainly affects foxes and marsupials.

Most of the time when talking about canine leishmaniasis, it is visceral leishmaniasis . The main host of the parasite is the dog, so it is important to keep an eye on the animal.

The symptoms are the same as those found in humans, ranging from ulcers on the skin and mucosa as well as nodules in various regions such as the head and neck.

The animal may die after some time with the parasite due to the complications of the disease without treatment.

Although the disease can be cured in humans, unfortunately, there is no guaranteed cure for leishmaniasis for dogs. The treatment of the disease makes it numb, but not always cured.

Due to the difficulty in curing and protecting animals against mosquitoes, which facilitates the spread of the disease, until a few years ago, euthanasia of infected dogs was an option.

However, with the development of new treatments and research, the cure of leishmaniasis for dogs becomes more possible.

Leishmaniasis medication in dogs

In animals the cure is more complicated than in humans, but there are options. In 2016, the drug miltefosine ( Milteforan ) for dogs was released in Brazil . Although expensive, it has shown results with complete cures of the animals.

Miltefosine is an antiparasitic that attacks leishmania parasites and, if the treatment is carried out correctly, can save the dog from the disease. It is important that treatment with miltefosine be carried out with the assistance of a veterinarian.

In addition, the drug must be administered during all prescribed days – often 28 – without fail , as failing to administer miltefosine can cause the parasite to recover and not be cured by the drug.

After treatment, the dog is expected to have a normal life expectancy, however it is important to have veterinary monitoring to ensure that the puppy is safe.

Causes

Through the bite of the infected straw mosquito, the parasite that causes leishmaniasis is transmitted to humans or animals and the disease sets in.

The parasite is of the genus leishmania and 30 different types of it can cause the disease in humans. Some of the main ones are as follows:

Leishmania amazonensis

This protozoan that causes leishmaniasis is found throughout Brazil, but mainly in the Amazon rainforest region. It usually causes cutaneous or cutaneous leishmaniasis.

Leishmania guyanensis

This species is present in the northern region of Brazil, mainly in the forest regions where there are no floods. Like amazonensis, it usually causes the cutaneous version of the disease.

Leishmania braziliensis

This species was the first to be classified as the cause of leishmaniasis. Despite its name, it is spread over much of Latin America. It is the main cause of visceral leishmaniasis.

How do parasites reach the organism?

Leishmaniasis parasites can survive the phagocytosis process . It is through phagocytosis that the immune system’s phagocytic cells destroy infectious agents. These cells surround the agent of the infection and use acids to eliminate it.

Leishmania is able to survive the acid. Its main victims are macrophages , large phagocytic cells of the immune system.

By surviving phagocytosis, the parasite contaminates the macrophage and uses its energy to reproduce, finally killing the cell and releasing more parasites that will contaminate other cells.

In most cases, the immune system is able to destroy contaminated macrophages through a cytotoxic immune response . This response is called Th1 and releases compounds capable of killing cells. In such cases, the symptoms are just cutaneous.

However, in some cases, the immune response is the production of antibodies (called Th2). In these cases, although the free leishmanias in the blood are eliminated, the infection continues since the parasites inside the macrophages are protected.

When this happens, leishmaniasis evolves to the mucocutaneous type (in most cases) or to visceral leishmaniasis (when the contamination is by L. donovani, L. chagasi or L. infantum ).

How does the transmission happen?

The most common means of transmission of leishmaniasis is the bite of sandflies, notably the straw mosquito . These mosquitoes are small, capable of passing through the mesh of many mosquito nets and screens.

Straw mosquitoes are found in damp, dark places with nearby plants. If one of these mosquitoes bites an infected mammal and consumes blood with the parasite, leishmania starts to reproduce in the insect’s intestines.

After a few days, it passes into the mosquito’s saliva, where it infects new mammalian hosts, closing the cycle.

The disease mainly affects dogs, but it can affect cats, cattle, rodents and other mammals, including humans.

It is recommended to monitor the health status of dogs to prevent the disease from spreading.

Leishmaniasis cycle

The parasite has two different forms that define what state of life they are in: amastigotes and promastigotes .

The amastigote shape is oval and it is this shape that is able to infect the mosquito.

When the straw mosquito consumes the blood of an infected animal, the amastigote protozoa go to the insect’s stomach and begin to develop.

Inside the insect, the parasite starts to reproduce and the cells take on the promastigote shape, which is elongated and has a flagellum. Flagellum is the small tail that the protozoan uses to move.

The promastigote shape begins to appear in the saliva of the straw mosquito and, when it bites another animal, the parasites enter the bloodstream again.

When inside the host’s body, the protozoan is phagocyted by an immune cell. This puts it inside the cell, where it starts to reproduce in amastigote form again.

Finally, the cell ruptures, releasing thousands of other parasites in the patient’s blood.

Thus, the cycle begins again and if another straw mosquito bites this host – be it a dog, cat or human – there will be the transmission of the parasite to the insect.

Groups and risk factors

Some groups are more likely to develop serious versions of the disease. Are they:

HIV Positive

Due to the immunological problems caused by the HIV virus , the parasite is able to freely infect people suffering from AIDS . The immune system unable to cope with the disease allows its evolution to be rapid and dangerous.

Malnutrition

Malnutrition weakens the immune system, which may find it more difficult to eliminate parasites, making malnourished people a group that can easily develop the disease.

Immune system impairment

Any disease that compromises the immune system opens the way for a cutaneous leishmaniasis to evolve into mucocutaneous or kala azar.

Deforested regions

People who live in recently deforested regions are at risk of contamination, as mosquitoes that lived in the forest area can live in the region.

Forests

Visits to regions of tropical forests, such as the Amazon, can expose people to the leishmania parasite, increasing the chances of contraction and evolution of the disease.

Poor regions

Poorer regions have a higher number of leishmaniasis cases due to less control of the mosquito population and difficulty in accessing the treatment of parasitic infection, which facilitates the continuation of the protozoan cycle.

Symptoms

The symptoms of leishmaniasis vary slightly according to the type of disease, but in the presence of these signs you should seek medical help to make a diagnosis and treatment, since leishmaniasis is a dangerous disease.

The symptoms are:

Skin ulcers

The most classic and well-known symptom of leishmaniasis is skin ulcers, which can also affect mucous membranes, such as the inside of the mouth and nose.

Ulcers can be large and, in more serious cases such as mucocutaneous, nose, ears and lips can be destroyed by the disease. It is essential to seek medical help.

Skin peeling

The disease initially manifests itself through peeling of the skin, especially in the nose, chin, mouth, ears and scalp. There is often confusion with dandruff in the latter case.

Swelling of the scalp

The bumps caused by leishmaniasis usually appear on the scalp. Due to the patient’s itching, they can become sore, but it does not always happen.

Fever

Infection by the parasite can cause fever . It is intermittent (can come and go at indefinite intervals) and can last for weeks.

Immunity reduction

Due to the action of the parasite on the cells of the immune system and the organs that work with it, the patient’s immunity is reduced. Infections become more dangerous and easier to contract, especially in cases of tuberculosis and malaria .

Weakness

In more advanced stages of the disease, the infection can cause weakness in the patient’s body.

Diarrhea

Due to the effect that the disease has on the internal organs, diarrhea can appear in the patient affected by kala azar (visceral leishmaniasis).

Bleeding in the mouth and intestines

Bleeding can occur in the mouth and intestines. Bleeding in the mouth is easy to identify, but the intestine is noticeable when there is blood in the stool .

Caquexia

Cachexia is a condition in which the body faces extreme weakness and weight loss. It is a major cause of death for cancer patients , in addition to affecting malnourished people.

Advanced visceral leishmaniasis can cause cachexia.

Pallor

If left untreated, the disease can reach the stage of causing pallor in the skin and mucous membranes such as nose and mouth.

Splenomegaly (enlarged spleen)

The organs that have a large amount of macrophages are especially affected. This applies to the spleen, which is an especially important organ for the immune system. The enlarged spleen may be the result of leishmaniasis.

Hepatomegaly (enlarged liver)

Like the spleen, the liver is also an organ full of macrophages and extremely important in the immune system. When infected with leishmaniasis, it can swell and take up more space within the body.

How is the diagnosis made?

The suspicion of leishmaniasis usually arises due to peeling and ulcers on the skin. The disease, especially in the visceral version, can go unnoticed for months, and it is common for its symptoms to be confused with other diseases such as malaria, typhoid and chagas disease.

For accurate diagnosis it is necessary to carry out some tests.

Cutaneous leishmaniasis

Cutaneous leishmaniasis is easier to diagnose. The ulcers are very visible and it is possible to collect the material directly from them, through a scraping, which can then be analyzed under the microscope to identify the parasite.

Visceral leishmaniasis

When dealing with kala azar, the diagnosis can be more difficult. Many of its symptoms are similar to other diseases, so the suspicion may take time to appear.

For these tests, materials extracted from bone marrow, spleen or blood serum may be used, depending on the test.

Blood serum is extracted from the blood by centrifugation. It is the part of the blood without the red blood cells. It is there that we find the antibodies created by the immune system.

Indirect immunofluorescence reaction

This test uses the patient’s blood serum and seeks to find specific antigens. Antigens are substances that, when introduced into the body, cause antibodies to be produced against them. The protozoa of the genus leishmania are antigens.

To perform the exam, the culture of the antigen that is sought is done in the laboratory. Then, the patient’s blood serum is added to the antigen. If there are antibodies to that specific antigen in the patient’s serum, they will bind. The mixture is washed so that antibodies that have not bound to any antigen are removed.

Then, antibodies labeled with fluorochrome, a fluorescent substance, are added. These labeled antibodies are called conjugates. The conjugates seek to bind with the antibodies that are bound to the antigen. The mixture is then washed again to remove antibodies that have not bound to anything.

Finally, the sample is observed under a fluorescence microscope, which has filters that allow the fluorochrome fluorescence to be seen.

If there is fluorescence in the microscope image, it means that the patient’s serum has antibodies to that studied antigen, in this case, leishmania, so it can be assumed that the protozoan is present in the patient’s body, since the body only produces antibodies when there is infection of the antigen.

Enzyme-linked immunosorbent assay (ELISA)

The ELISA test (from English Enzyme Linked ImmunoSorbent Assay) is an immunoenzymatic test. This means that it detects reactions between antigen and antibody through enzymes.

There are several ways to take this exam, but the most common works like this:

In a polystyrene plate, the pure antigen (in this case leishmania) is deposited. The patient’s serum is placed on the plate. As with immunofluorescence, if the patient is infected, the blood serum will have antibodies specific to leishmania and they will bind.

Conjugates are added, antibodies that react to immunoglobulins and that are linked to a catalyst. Catalysts are substances that accelerate chemical reactions. The antibodies initially added to the test are immunoglobulins and bind to the conjugate when they are connected to the antigen.

Then, a chemical substance is added that gives color next to one that reacts with the catalyst. If there are antibodies to that antigen in the patient’s serum, the reaction happens and the color can be seen under a microscope.

Blood count

The blood count is not used for the direct diagnosis of the disease, but to discover its severity by counting white blood cells and platelets.

Montenegro reaction

Montenegro’s reaction is an immunological test that seeks to identify some types of infections, including leishmaniasis. It also serves to identify whether the patient has been infected with leishmania in the past.

For the test, through an injection under the skin, inactive antigens (the protozoan) are inserted or pieces of them mixed in a saline solution. If the patient has had that infection before, the body will have antibodies prepared and the reaction will be violent. At the application site, there will be swelling and hardening of the skin. Small ulcerations may appear.

When the patient has never had the infection, the reaction is small and weak. Inactive antigens are not harmful and do not create an infection.

The test is not definitive. If the reaction appears strong, it is a sign that the protozoan has already infected the patient, but it does not necessarily mean that the infection is ongoing. This happens because, after an infection is overcome, the body keeps some antibodies that can fight that antigen, being prepared for the possibility of a new infection.

It is also possible that there will be no strong reaction even if the infection is ongoing, since, if it is in the beginning or the patient is immunosuppressed, the reaction will be weak.

Is leishmaniasis curable?

In most cases, human leishmaniasis is curable. However, it is not always possible to get rid of the disease completely and it can only be inactive.

With animals the opposite is true: in some types of treatment healing is possible, but it is quite difficult.

In cases where the patient’s immune system reacts correctly to the parasite, eliminating the phagocytic cells, the person becomes immune to leishmaniasis.

What is the treatment?

Treatment, both in humans and animals, is done through pentavalent antimonial medication .

This treatment is aggressive and can cause several side effects, such as headaches, liver changes and facial edema, among others, but when the patient heals, which takes around 30 days of daily injections of the drug, he is usually immune.

Medicines

The drugs commonly used to cure leishmaniasis in humans, also available through SUS, are:

  • Antimônio (Glucantime);
  • Amphotericin B ( Ambisome );
  • Pentamidina;
  • Marbofloxacino;
  • Miltefosina.

These drugs are used together depending on which version of the disease is present.

Attention!

NEVER  self-medicate or stop using a medication without first consulting a doctor. Only he will be able to tell which medication, dosage and duration of treatment is the most suitable for his specific case. The information contained in this website is only intended to inform, not in any way intended to replace the guidance of a specialist or serve as a recommendation for any type of treatment. Always follow the instructions on the package insert and, if symptoms persist, seek medical or pharmaceutical advice.

Prognosis

The most serious cases of the disease can lead to death, but with adequate treatment, in humans, the chances of cure are high.

In cases of kala azar there is a chance that the disease will progress to post-kala azal dermal leishmaniasis . This condition can appear up to twenty years after the infection, and although no organism that causes kala azar leads to the disease, it is often linked to L. donovani.  It is common in countries like Sudan and India and appears as facial erythema, nodules or papules.

Complications

Some complications can arise as a result of the disease, both in humans and animals.

Infections

Due to the action of the parasite on the macrophages, the patient’s immune system is compromised, which can make him more susceptible to infections such as malaria, tuberculosis, among others.

Streaming

Any person or animal infected by any version of leishmaniasis becomes a vector of the disease. This means that if a mosquito that is not infected bites that patient, the parasite will spread to that mosquito, which can then infect more people or animals with this serious condition.

Leishmaniose mucocutânea

Facial deformation is the main concern in these cases. Mucocutaneous leishmaniasis affects and destroys the skin and cartilage and can cause severe  deformations, eliminating entire parts of the patient’s face. This leaves openings that facilitate infections that can lead to death.

Visceral leishmaniasis

Kala azar, if left untreated, evolves and can cause severe pain, internal bleeding, severe weight loss and death. Treating leishmaniasis is of paramount importance.

How to prevent

The prevention of leishmaniasis is done through some means to avoid contamination. Are they:

Repellent collars

Collars that release repellents on the animal can keep mosquitoes away. They can be purchased at pet stores and veterinary clinics and, while not particularly cheap, keep your pet and the humans around you safe from disease.

Use of insecticides

Killing the insect that transmits the disease prevents the parasite’s cycle from continuing.

Mosquito nets

Blocking windows with mosquito nets prevents them from entering the homes where people live, making it difficult for the disease to spread. Nets may contain insecticides to eliminate the insect.

Treatment of infected

Treating the infected – both humans and animals – reduces the spread of the disease through the insects that transmit it.

Leishmaniasis vaccine

There is no vaccine for leishmaniasis for humans. However, there are for dogs.

Vaccination is one of the most important parts of having a pet. It protects them from serious illnesses that can range from rabies to worms. This includes leishmaniasis.

The vaccine for leishmaniasis should be applied at the puppy’s four months of age, divided into 3 doses separated by 21 days each. It is important that the vaccine is renewed every year to ensure the protection of your pet.

The vaccinated dog has an immune system prepared to deal with the disease, which greatly increases its protection against leishmaniasis, which can be fatal, in addition to considerably reducing the chances of it transmitting the parasite to a straw mosquito.

Protecting your puppy is also protecting everyone around him, as a mosquito could become contaminated and bite others, spreading the disease.


Leishmaniasis is a serious disease, which kills up to 90% of patients who do not treat it if symptoms appear. However, a cure is possible. Dogs, the main victims of the disease, have a lesser chance of cure and need to be protected from insect bites.

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