Leishmaniasis Overview and Species

Leishmaniasis Overview

• Leishmaniasis is a disease caused by parasites of the Leishmania genus, found in the Kinetoplastida order.
• Over 20 pathogenic species are known.
• The parasites affect humans and mammals, especially dogs and rodents.
• Transmission occurs through bites from infected Phlebotomus and Lutzomyia insects.

Leishmania Species and Distribution

• Old World Leishmania: Divided into various complexes and species with specific diseases and geographic distributions.
  • L. major is associated with "wet" cutaneous leishmaniasis, prevalent in rural Asia and Africa.
  • L. tropica causes "dry" cutaneous leishmaniasis, found in urban areas of Europe, Asia, and parts of North Africa.
  • L. aethiopica also causes cutaneous leishmaniasis in Ethiopia and Kenya.
  • L. donovani and its subspecies are linked to visceral leishmaniasis (kala azar) in Africa and Asia.
    • L. donovani archibaldi and L. donovani sinensis are also associated with visceral leishmaniasis, found in Kenya, China, and the Mediterranean region/East Africa, respectively.
    • L. donovani infantum specifically causes infantile visceral leishmaniasis in the Mediterranean/ East Africa regions.
• New World Leishmania: Also has specific species with diverse diseases and distributions.
  • L. donovani chagasi and other species like L. braziliensis, L. guyanensis, and L. mexicana are associated with mainly mucocutaneous, cutaneous, and other forms. Their distribution is concentrated in South America including Andean regions

Morphology

• Parasites in insect vectors or culture have a promastigote form.
• Their morphology in the host mammals has an amastigote form.
• Leishman-Donovan bodies, which are small, oval, or round intracellular structures, measure 2-5 µm in diameter.
• They are found in macrophages and certain other white blood cells, such as those found in organs like spleen, liver, bone marrow, etc.

Leishmaniasis Clinical Presentations

• Leishmaniasis has three main clinical presentations:
  • Cutaneous Leishmaniasis: This involves the skin.
    • Distinguished by L. tropica (dry sores), L. major (wet sores), and L. aethiopica.
  • Mucocutaneous Leishmaniasis: This affects the mucous membranes of the nose, throat, mouth, and other tissues. L. Braziliensis being the species most involved.
  • Visceral Leishmaniasis (Kala Azar): This occurs within lymphoid and reticuloendothelial tissues.
    • It is the most serious form, characterized by high fever, malaise, weight loss, anemia, and enlargement of the spleen and liver.
    • This form is prevalent in non-endemic areas but can dramatically impact affected people.

Epidemiological Types of Visceral Leishmaniasis

• Endemic Visceral Leishmaniasis: Primarily affects children between 1 to 4 years of age, commonly found in the Mediterranean area, South-West Asia, China, and Latin America.
• Sporadic Visceral Leishmaniasis: Occurs in non-indigenous people entering areas with high endemic cases, usually has a more acute course in individuals.

Epidemic Visceral Leishmaniasis

• This form affects people of all ages, but typically with a higher incidence in the age bracket of 5 to 9 years or older.
• It is normally found in East Africa and India
• This form is often misdiagnosed due to its similarity with malaria.

Post-Kala-Azar Dermal Leishmaniasis (PKDL)

• This occurs as a sequel to visceral leishmaniasis.
• Patients develop resistance or immunity to the disease itself, which results in PKDL.
• It is often linked to previous infection with Leishmania tropica.

Factors Affecting Outcome of Infection

• Parasite strain characteristics.
• The size of the infection.
• Site of infection/entry point.
• Host genetics or immune system responses.
• HIV status and existing immunity are critical.
• Nutritional impact.

Diagnosis

• Diagnosis typically involves analyzing skin lesions, blood, spleen, or bone marrow samples.
• Stains such as May-Grunwald-Giemsa can detect Leishmania in the tissues.
• Culture methods/tests are used to identify presence of the parasite.

Treatment

• Antimony based medicines are commonly used initially.
• More modern approaches include drugs like liposomal amphotericin B, fluconazole, miltefosine.
• Topical therapies like paromomycin or methylbenzethonium and heat therapy may also be used.

Control Measures

• Prevention strategies focus on avoiding sandfly bites.
• Controlling the sandfly population and any animal reservoirs.
• Treating infected individuals is key in containment strategies.

This quiz covers the essentials of leishmaniasis, including its causative parasites from the Leishmania genus and their distribution across the globe. Learn about the various species and their associated diseases, as well as the geographic areas most affected by this serious health concern.