Parasitic Infections: Leishmania donovani Notes

Leishmania donovani

• Leishmania has a dimorphic life cycle spent between mammalian hosts (humans, rodents, cats, dogs) and insect vectors (adult female sandflies, Phlebotomus)
• Transmission occurs mainly through insect bites
• Leishmaniasis is classified according to the body site where the lymphoid tissue is infected: cutaneous, mucocutaneous, and visceral
• Visceral leishmaniasis (Kala-azar) is caused by L. donovani and is endemic in South Asia, Brazil, and Sudan
• Symptoms of visceral leishmaniasis include fever, diarrhea, anemia, massive hepatosplenomegaly, weight loss, and possible skin and kidney involvement
• Diagnosis is made through detecting amastigotes in clinical specimens, promastigotes in culture, genome detection through PCR, and serological tests
• Treatment involves using Amphotericin B (antifungal) and prevention through sandfly control and prompt treatment of human cases

Trypanosoma brucei

• Trypanosoma brucei is a complex of three subspecies, two of which cause human disease: T. b. gambiense and T. b. rhodesiense
• Transmitted by the bite of the tsetse fly (Glossina), causing African trypanosomiasis (sleeping sickness)
• T. b. gambiense is limited to tropical West and Central Africa and has a longer incubation period
• T. b. rhodesiense is found in East Africa, has a shorter incubation period, and progresses rapidly to a fulminant fatal disease
• Symptoms of African trypanosomiasis include ulcer at the bite site, flu-like illness, lymphadenopathy, lethargy, tremors, meningoencephalitis, mental retardation, and general deterioration
• Diagnosis is made through microscopy, antibody detection, and nucleic acid detection
• Treatment involves using Suramin (ATP synthesis inhibitor) and pentamidine for the hemolymphatic stage and Melarsoprol (arsenical heavy metal compound) for the CNS stage
• Prevention measures include prompt treatment of infected people, eradication of tsetse fly breeding sites, protective netting and clothing, and use of insect repellents

Trypanosoma cruzi

• Trypanosoma cruzi causes American trypanosomiasis (Chagas disease), which is endemic in South and Central America
• Found in many mammalian host reservoirs besides humans, transmitted by bugs (triatomine and reduviid), which usually bite facial sites
• Clinical manifestations of Chagas disease include:
  • Acute: erythematous and induration at bug bite (chagoma), facial rash and periorbital edema (Romaña sign), and possible fatal CNS involvement
  • Latent (Indeterminate): asymptomatic and progresses to chronic
  • Chronic: affects the liver and spleen (hepatosplenomegaly), heart (myocarditis and dilated cardiomyopathy), Auerbach's plexus in GIT (megaesophagus and megacolon), and CNS (granulomas, cysts, and meningoencephalitis)
• Diagnosis is made through microscopy and parasitemia