Definition

Leishmaniasis and trypanosomiasis are a group of neglected tropical diseases (NTDs) caused by protozoan parasite infections of Leishmania spp and Trypanosoma spp. These diseases affect humans and animals in tropical and subtropical regions.

Historically, these diseases were limited to certain areas but have spread worldwide due to human migration, climate change, and anthropogenic changes.

Causes

Trypanosomiasis presents in two forms:

• Sleeping sickness is a life-threatening disease in Africa caused by two subspecies of Trypanosoma brucei: T. brucei gambiense (gHAT) and T. brucei rhodesiense (rHAT). These trypanosomes are transmitted through the bite of tsetse flies. Apart from vector transmission, other modes of disease spread include sexual contact, laboratory incidents, congenital transmission, and blood transfusion.
• Chagas disease in South America is caused by Trypanosoma cruzi, which is transmitted through Reduviidae bugs. Presently, this disease is endemic in 21 Latin American countries. In addition to bugs, infection transmission occurs orally (through ingesting food contaminated with insect feces containing the parasite), through the placenta, breastfeeding, organ transplantation, and blood transfusion.

Leishmaniasis, caused by the protozoan parasite Leishmania spp., is found in nearly 100 countries worldwide. This parasite is transmitted through the bite of female sandflies. The disease is endemic in Asia, Africa, the Americas, and the Mediterranean.

Risk factor

Leishmaniasis and trypanosomiasis diseases are closely linked to environmental and socioeconomic factors and are clearly associated with poverty.

Symptoms

The acute phase of Chagas disease, characterized by rapid onset of symptoms, typically begins within 2 weeks after the parasite enters the body. The symptoms that manifest are similar to those of other common diseases, including:

• Mild fever
• Decreased appetite
• Headaches
• Diarrhea
• Non-painful swelling of the eyelids

The chronic (long-term) phase of Chagas disease may not exhibit symptoms and thus can go undetected. However, symptoms may arise if there is impairment of the heart muscles and digestive system, with a mortality rate ranging from 0.2 to 20%. If abnormalities occur in the heart, symptoms such as rapid or irregular heartbeat, shortness of breath, dizziness, or fainting may manifest.

Sleeping sickness occurs in 2 phases: the early and advanced phases. Initial symptoms of this infection are nonspecific, including joint pain, headaches, and fatigue. However, as the disease progresses, more severe symptoms may emerge, such as:

• Enlargement of the liver
• Enlargement of lymph nodes
• Enlargement of the spleen
• Chest pain
• Shortness of breath

When the parasite has breached the blood-brain barrier, the patient will encounter neurological symptoms such as:

• Daytime sleepiness
• Insomnia at night
• Slurred speech
• Muscle pain and weakness
• Loss of balance
• Visual disturbances

Ultimately, the disease will advance to a diminished level of consciousness, coma, seizures, and ultimately death.

The symptoms of leishmaniasis are classified into three types:

• Cutaneous leishmaniasis (CL): This type affects the skin, typically manifesting as a small red spot at the site of the sandfly bite. This spot develops into a lump that forms a sore. Treatment or spontaneous healing may result in lifelong skin scars. If symptoms spread to other parts of the entire body, treating it becomes challenging and may not heal spontaneously.
• Mucocutaneous leishmaniasis (MCL): MCL affects the mucous membranes and skin. The parasite can spread to mucous membrane tissues through the lymphatic system or blood. Symptoms of MCL include sores on the mucous membranes of the nose and the formation of holes in the nasal septum (the middle part of the nose), which cannot heal spontaneously and are difficult to treat. These sores are prone to bacterial infection.
• Visceral leishmaniasis (VL) or kala-azar: This type affects internal organs. Symptoms include irregular fever, weight loss, enlargement of the spleen, enlargement of the liver, swelling of the lymph nodes, and anemia, characterized by paleness, weakness, dizziness, and difficulty concentrating.

Diagnosis

The diagnosis of leishmaniasis and trypanosomiasis can be established based on the signs and symptoms present, along with several tests, including:

• Microscopic examination: This involves searching for parasites in patient tissue samples.
• Culture: Parasites can be grown on laboratory media.
• Real-time PCR (polymerase chain reaction): This method detects parasite DNA.
• Serology: This test is employed to detect antibodies against the parasite.
• Detection of parasite antigens.

Due to the low number of parasites in the sample, doctors may utilize multiple diagnostic methods to detect infections accurately.

Management

Currently, the drugs used to treat these diseases face challenges such as limited efficacy, high toxicity, relatively high cost, limited availability, and increasing drug resistance.

Therapy for Chagas disease primarily relies on two orally administered drugs: benznidazole and nifurtimox. These medications can cure or significantly reduce the parasite's effects in 60-85% of acute cases, but they are relatively ineffective in the chronic stage. Nonetheless, they are still administered in acute and chronic phases to inhibit disease progression. In end-stage Chagas disease, heart transplantation may be considered.

Treatment for sleeping sickness varies depending on the disease stage. Drug options include pentamidine, suramin, eflornithine, nifurtimox, and melarsoprol.

In contrast to American trypanosomiasis, treatment for leishmaniasis involves a wider range of drug options, with efficacy and drug choices depending greatly on the infecting species. Available therapy options include pentavalent antimonials, amphotericin B, liposomal amphotericin B, paromomycin, pentamidine isethionate, and miltefosine.

Complications

There is no direct connection between leishmaniasis and trypanosomiasis with kidney disorders, although experimental models have shown some kidney damage. However, kidney damage can occur, particularly as a result of multiple organ failure in African trypanosomiasis.

In very rare cases, some individuals may experience aggressive acute Chagas disease infection, typically characterized by inflammation of the heart muscles, inflammation of the brain and its membranes, or both, which can lead to death. Cardiac muscle abnormalities due to Chagas disease are the leading cause of death among Chagas patients, resulting from heart failure, blood vessel blockage, and cardiac arrest.

Prevention

Currently, no human vaccines or drugs are available to prevent diseases caused by these organisms.

The most effective method of prevention is to protect oneself from insect bites. This can be achieved by minimizing outdoor activities during the night, wearing long clothing that covers the body, and applying insect-repellent cream to the skin.

When to see a doctor?

Suppose you have recently travelled to an endemic country or are living in such a country and experiencing new symptoms. In that case, it is advisable to consult a doctor for proper evaluation and management.

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