What is Leishmaniasis and Leishmania? | Leishmania donovani | Life Cycle, Treatment | MEDZUKHRUF

Summary

This video covers Leishmania donovani, a protozoan parasite responsible for visceral leishmaniasis, also known as kala azar or black sickness. The script explains its classification, morphology, habitat, transmission via sandflies, life cycle, pathogenesis, and clinical findings. It discusses symptoms such as fever, weakness, splenomegaly, anemia, and hyperpigmentation. The video also includes diagnostic methods, treatment options like pentavalent antimonials, and prevention strategies. The importance of early diagnosis and proper therapy in reducing mortality rates is emphasized, and the host species involved in the epidemiology of the disease are mentioned.

Takeaways

• 🦠 Leishmania donovani is an intracellular protozoan parasite belonging to the genus Trypanosomatidae and causes visceral leishmaniasis (kala-azar).
• 🔬 The parasite exists in two morphological forms: amastigote (round/oval, intracellular, no flagellum) and promastigote (elongated, flagellated, found in sandfly gut).
• 🪰 Transmission occurs through the bite of infected female sandflies, which ingest amastigote-infected macrophages and later inject promastigotes into humans.
• 👤 In humans, promastigotes transform into amastigotes inside macrophages and multiply, spreading throughout the reticuloendothelial system.
• 🧬 Visceral leishmaniasis primarily affects the spleen, liver, and bone marrow, leading to anemia, leukopenia, and thrombocytopenia due to decreased bone marrow activity.
• 📍 Hyperpigmentation of the skin occurs, leading to the term 'black sickness' or kala-azar.
• 🌍 The disease exhibits distinct epidemiological patterns: dog/fox reservoirs in the Mediterranean and Middle East, small carnivores in sub-Saharan Africa, and humans as the reservoir in India and surrounding regions.
• ⚕️ Clinical features include chronic fever, massive splenomegaly, weakness, weight loss, hepatomegaly, lymphadenopathy, and progressive emaciation.
• 🧪 Diagnosis involves microscopy of tissue aspirates, Giemsa-stained smears, culture for promastigotes, serological tests such as IFA, ELISA, and the leishmanin skin test.
• 💊 Treatment options include pentavalent antimonials (e.g., sodium stibogluconate) and liposomal amphotericin B, with pentamidine as an option for Old World cutaneous forms.
• 🛡️ Prevention includes protection from sandfly bites through nets, repellents, protective clothing, insecticide spraying, and vaccination programs.

Q & A

What is Leishmaniasis and which parasite causes it?

Leishmaniasis is a disease caused by the parasite *Leishmania*, which is a genus of trypanosomes. The disease manifests in different forms, depending on the species of *Leishmania*, with *Leishmania donovani* causing visceral Leishmaniasis (Kala-azar).

What are the different species of *Leishmania* and the diseases they cause?

There are several species of *Leishmania*. *Leishmania donovani* causes visceral Leishmaniasis (Kala-azar), *Leishmania tropica* causes cutaneous Leishmaniasis in the Old World, *Leishmania mexicana* causes cutaneous Leishmaniasis in the Americas, and *Leishmania braziliensis* causes mucocutaneous Leishmaniasis in Central and South America.

What is the difference between the two forms of *Leishmania*?

The two forms of *Leishmania* are amastigotes and promastigotes. Amastigotes are round or oval, 2-6 x 1-3 micrometers, and have a delicate membrane without a flagellum. Promastigotes are long, slender, spindle-shaped, 15-20 x 1-2 micrometers, and have a flagellum and a thicker cell membrane.

What role do sandflies play in the transmission of *Leishmania*?

Sandflies, specifically female sandflies, are the vectors for *Leishmania* transmission. They bite infected hosts to take a blood meal, which contains *Leishmania* amastigotes. The parasites transform into promastigotes in the sandfly’s gut, and when the fly bites another host, it injects the promastigotes, completing the transmission cycle.

What is the life cycle of *Leishmania*?

The life cycle of *Leishmania* has two stages: the sandfly cycle and the human cycle. In the sandfly, the parasite transforms into promastigotes and is transmitted during a bite. In humans, promastigotes are engulfed by macrophages, transforming into amastigotes that multiply and spread to other cells, continuing the cycle when another sandfly bites an infected person.

What are the key clinical symptoms of Visceral Leishmaniasis (Kala-azar)?

Clinical symptoms of Visceral Leishmaniasis (Kala-azar) include fever, weakness, weight loss, splenomegaly (enlarged spleen), slight hepatomegaly (enlarged liver), lymphadenopathy, and hyperpigmentation of the skin. It is often referred to as 'black sickness' due to the skin pigmentation caused by increased melanin.

How is *Leishmaniasis* diagnosed in the laboratory?

Diagnosis of *Leishmaniasis* involves examining samples from blood, bone marrow, liver, spleen, or lymph node aspirates under a microscope to identify amastigotes. Other tests include indirect immunofluorescence tests, ELISA for detecting antibodies, and a skin test (LST) to check for past infection.

What are the treatment options for *Leishmaniasis*?

Treatment for *Leishmaniasis* includes medications such as pentavalent antimonials (e.g., sodium stibogluconate), liposomal amphotericin B, and pentamidine isonitate for Old World Leishmaniasis. Treatment varies based on the geographical area and the type of Leishmaniasis.

What are the preventive measures to avoid *Leishmaniasis*?

Prevention of *Leishmaniasis* focuses on avoiding sandfly bites by using protective clothing, nets, insect repellents, and insecticide spraying. Additionally, there is a vaccine for Oriental sore (cutaneous Leishmaniasis), which has helped reduce the incidence of the disease in certain regions.

Why is *Leishmania donovani* known as the causative agent of 'black sickness'?

The term 'black sickness' refers to the hyperpigmentation of the skin caused by increased melanin production in individuals infected with *Leishmania donovani*, which causes Visceral Leishmaniasis (Kala-azar). This pigmentation often appears as dark spots on the skin, giving rise to the name 'black sickness'.