Leishmania and Trypansoma Flashcards
Leishmania
- Leishmania donovani - visceral disease (Kala Azar)
- Leishmania major, Leishmania Mexicana, L major - cutaneous disease
- Leishmania brasiliensis - mucocutaneous disease
Leishmania Life Cycle
- Protozoan with a dimorphic life cycle.
- Promastigote (elongate, motile form-1.5-3.5 µm by 15-200 µm) found in the sandfly digestive tract and proboscis, is transmitted into the skin of a mammalian host by female sand flies when they take a blood meal.
- After inoculation, promastigotes are phagocytosed by macrophages, they transform into intracellular Amastigotes (3-5 µm in length) that lack a flagellum.
Leishmania Reservoirs and Vectors
- Human
- Dog
- Gerbils
- Hyrax
- Expansion of vector areas (Italy)
- Urban/sylvatic interface in the SA
Leishmania Life Cycles Cont.
- They multiply by simple binary division inside phagolysosomes, rupturing the cell and invading other reticuloendothelial cells.
- Amastigotes disseminate through regional lymphatics and the vascular system to infect mononuclear phagocytes.
- Cycle is completed when female sand flies ingest parasitized cells.
- In the digestive tract of the sand flies, Leishmania parasites develop through a series of flagellated intermediate stages to become infectious metacyclic promastigotes.
Leishmania Pathogenesis
- Organism injected by bite of sandfly (painful bite)
- Phagocytosis by macrophage
- Organism replicates in parasitophorous vacuole
- Control with TH1 response
Leishmania Clinical Disease: Visceral disease (Kala Azar) - L. donovani
•occurs in many tropical and subtropical regions of the east and west hemispheres, common in southern Sudan, disease typically develops after a several month of incubation period, most are immunocompetent but may have AIDS or impaired cell-mediated immunity, parasite burden is high and patients present with fevers and weight loss and typically have hepatosplenomegaly, Death usually occurs in the absence of treatment.
Leishmania Clinical Disease: Cutaneous disease - L. major, L. mexicana
•characterized by ulcerative lesions, which can be single or multiple., typically last from months to a year but subsequently heal even without treatment.
Leishmania Clinical Disease: Mucocutaneous disease - L. brasiliensis
•is characterized first by a primary nodule at the site of infection. This subsequently heals and months, or years, later destruction of nasal and mucosal tissue occurs with severe deformities.
Leishmania Diagnosis
• Identify microorganism
– Culture
– Histology
- Serology (visceral disease)
- Skin test
Leishmania Treatment
- Amphotericin B
- Azoles
- Mifepristone
- Sodium stibogluconate
- Heat
Canine Leishmania in the US
- 2009 Vet Clin North Am Small Anim Pract
- Outbreak of leishmania in Foxhounds in NY kennel 1999
- Competent vector, Lutzomyia shannoni, endemic to Southeast
- Breeds of dogs from southern Mediteranean region harbor this parasite
Trypanosomes
- Motile, fusiform protozoans of the blood (in tissue - different)
- 15-30 µ in length
- Trypomastigotes are found in humans
- In leishmaniasis, amastigotes are found in humans
- African Trypanosoma
– T. brucei gambiense, T. brucei rhodesiense, T. brucei brucei
• American Trypanosoma
– T. cruzi
African Trypanosomisis
- 10-20,000 cases/year (since 1967 only several dozen in Americans)
- T. brucei gambiense, T. brucei rhodesiense, T. brucei brucei
- Epimastigotes in salivary glands mature for several weeks to trypomastigotes and passed in saliva
- Highly Variable Glycoprotein (12-100s changes)
- As parasitemia progresses, some lose flagella and present as short and stumpy forms.
How do East and West African trypanosomiasis differ?
• Epidemiology
– Savannah vs. riverine
– Reservoirs: antelopes vs. humans
• Clinical illness
– West more prolonged: small vessels of heart and CNS with immune complex disease, IgM, lymphadenopathy, rash, myocarditis and seizures
How is African trypanosomiasis diagnosed?
- Agglutinin test
- Aspirate of lymph node
- Smear of blood
- Check the CSF first—if abnormal will need other agents; otherwise surimi or gentamicin
T. cruzi Chagas Disease Epidemiology
- Mexico to Middle Chile and Argentina
- The reduviid bug (triatomine or kissing bug) is the insect host for T. cruzi.
- Many different vectors: T. infestans, R. prolixus and emergent forms
- The vector and the parasite have been found in Arizona
- Foodborne, congenital
- Maybe 300,000 thousand infected individuals in the US
The 3 stages of American trypanosomiasis
- Acute: may be asymptomatic or may develop acute disease lasting weeks to months, chagoma and local inflammation at the site of entry, illness is characterized by a high level of parasitemia, symptoms include lymphocytosis, lymphadenopathy, and fever, some develop meningoencephalitis or myocarditis, treatable
- Indeterminate: some with acute infection (symptomatic or asymptomatic) enter the indeterminant phase, asymptomatic and with low-grade parasitemia, lasts many years and may resolve spontaneously or progress to chronic disease.
- Chronic (organomegaly): affects two major organ systems: the cardiac and gastrointestinal systems, the latter is uncommon and may be strain-dependent. It occurs not uncommonly in northern Brazil.
– Cardiac involvement is manifested by ventricular arrhythmias and by dilated cardiomyopathy with congestive heart failure.
– GI tract - Any part of the GI tract from the esophagus to the colon may be involved, although colonic and esophageal involvement is the most common.
