Leishmaniasis: Description
Leishmaniasis is particularly widespread in tropical-subtropical regions. In this country, leishmaniasis is rare; cases that do occur usually affect travelers returning from tropical countries.
As a result of climate change, the heat-loving vectors of the parasites – sand flies – are increasingly spreading from the Mediterranean region to more northerly regions. For example, the species Phlebotomus mascitii is already found in some regions of Germany, Austria and Switzerland.
Leishmaniasis in humans can affect different parts of the body, such as the skin or internal organs, depending on the form of the disease. Accordingly, three main forms of the disease are distinguished:
- visceral leishmaniasis: also called kala-azar (“black disease”). Here, skin and internal organs may be infested by the parasites, such as L. donovani (“Old World” species) or L. amazonensis (“New World” species).
Especially visceral leishmaniasis is often a concomitant infection of HIV infection.
Leishmaniasis: Occurrence
The main areas of distribution of cutaneous leishmaniasis include the Middle East, Central Asia and Africa (cutaneous leishmaniasis of the “Old World”) and Central and South America such as Brazil (cutaneous leishmaniasis of the “New World”).
Most cases of visceral leishmaniasis are observed in Brazil, East Africa (e.g., Kenya), and India.
Leishmaniasis: Symptoms
Leishmaniasis symptoms in humans can vary widely – first in terms of whether it is cutaneous, mucocutaneous, or visceral.
Cutaneous leishmaniasis
In cutaneous leishmaniasis, skin lesions develop. What these look like in detail depends primarily on which Leishmania species is responsible and how strong the patient’s immune defense is.
The ulcer has a slightly raised, reddish rim enclosing a “crater” – often covered by crusty coatings. Sometimes such ulcers tend to be dry, as in infection with Leishmania tropica. In contrast, L. major can cause moist (exudative) skin lesions – those that leak fluid.
Infection with certain leishmania (such as L. mexicana and L. amazonensis) takes the form of diffuse cutaneous leishmaniasis in some patients: because the immune system does not “respond” to the pathogens (anergy), they can spread easily. As a result, nodular but not ulcerated skin lesions form almost all over the body (except on the palms of the hands, soles of the feet and the scalp). In addition, the patients are in a poor general condition.
Visceral Leishmaniasis (Kala-Azar)
Visceral leishmaniasis is the most dangerous form of the disease and affects the liver, spleen, bone marrow and lymph nodes in addition to the skin. The disease can be subacute (less severe) to chronic.
If left untreated, visceral leishmaniasis is usually fatal.
Surviving patients may develop post-Kala Azar dermal leishmaniasis (PKDL) after one to three years. This involves the appearance of pale or reddish patches on the face or body that turn into papules and nodules. The appearance is often reminiscent of leprosy.
Mucocutaneous leishmaniasis
The affected tissue (mucosa, later also cartilage and bone) can be destroyed: This often starts with the nasal septum and can continue with other structures. The tissue destruction can, for example, lead to affected persons no longer being able to swallow. This makes it difficult to eat, which can cause the patient to lose a lot of weight (cachexia).
Leishmaniasis: Causes and risk factors
The infectious disease leishmaniasis is caused by parasites of the genus Leishmania:
- visceral leishmaniasis: e.g. by L. donovani, L. infantum
- mucocutaneous leishmaniasis: e.g. by L. braziliensis, L. guyanensis, L. panamensis, L. peruviana
These unicellular animal organisms (protozoa) can live not only in humans but also in animals. Thus, small rodents and domestic animals such as dogs also serve as hosts for the parasites. The pathogens are easily introduced in this country, for example, when dogs are imported from the Mediterranean region.
Leishmaniasis: Infection
The disease can also be transmitted via blood transfusions, bone marrow and organ transplants. During pregnancy, leishmania can pass from mother to child.
Incubation period
Leishmaniasis: examinations and diagnosis
If you have any suspicious symptoms of the disease, you should consult a specialist in dermatology, infectiology or tropical medicine. Diagnosis is based on symptoms, medical history (anamnesis) and microbiological evidence of the parasites.
During the anamnesis interview, the doctor may ask you the following questions, for example:
- Have you had a fever? If so, how did the fever manifest itself?
- Do you suffer from other comorbidities with weakened immune defenses, such as HIV infection?
Even if your travels to tropical-subtropical regions took place a long time ago, you should inform your doctor.
Leishmania detection
Skin/mucous membrane samples from altered areas (cutaneous or mucocutaneous leishmaniasis) can be tested for leishmania in the laboratory:
If visceral leishmaniasis is suspected, blood samples can be searched for the genetic material of Leishmania using PCR. Another option is to obtain a bone marrow sample and examine it microscopically for the parasites. Sometimes tissue samples are taken from other organs such as the spleen.
In addition, one can look for antibodies against Leishmania in the blood.
Leishmaniasis: Further examinations
In individual cases, further examinations may be useful.
For example, blood analyses can provide additional information. For example, in visceral leishmaniasis, the number of all blood cells is reduced as a result of bone marrow damage (pantcytopenia).
By means of ultrasound examination (of spleen, liver, etc.), the physician can assess the extent of organ infestation in visceral leishmaniasis.
Leishmaniasis: Treatment
Leishmaniasis treatment depends on several factors. These include the form and severity of the disease, the causative Leishmania species, any concomitant diseases and any existing pregnancy.
Another systemic therapy option in certain cases of cutaneous leishmaniasis is the combination of antimony and another agent such as allopurinol or pentoxifylline.
Mucocutaneous leishmaniasis is always treated systemically. Agents such as those used for some cutaneous leishmaniases (e.g. antimony plus pentoxifylline) can be considered.
Leishmaniasis: disease course and prognosis.
Cutaneous leishmaniasis of the “Old World” has a good prognosis. In most cases, the skin lesions heal within two to 15 months, or after two years at the latest – but always with scarring.
The most dangerous is visceral leishmaniasis. Untreated, it almost always leads to death within six months to two years. However, if therapy is initiated in time, the prognosis is good. However, up to 20 percent of patients develop post-kala azar skin leishmaniasis as a late complication.
In the case of certain Leishmania species, the following applies: those who have overcome the infection then have lifelong immunity to the species in question – but not to other Leishmaniasis pathogens.
A leishmaniasis vaccination does not exist yet.
