Trypanosomiasis [2] American Trypanosomiasis [Chagas’ disease]:

[2] Trypanosoma cruzi [Chagas Disease] Epidemiology Geographical Distribution: Central & South America. Chagas’ diseases occurs in Central & South America with a prevalence of ~15-20 million and a mortality rate of ~30%.

Epidemiology Disease: American trypanosomiasis or Chagas’ disease. Habitat: Blood, Reticulo-endothelial cells & Muscle fibers (e.g. heart). D.H.: Man. R.H.: Armadillos, opossum, dogs, cats & rodents. Vector : Triatomine (kissing bug) Triatomine (kissing bug)

Opossums and Raccoons naturally infected with Trypanosoma cruzi are reservoir hosts in southwestern United States and Central and South America.

Triatoma

(Cone nose Bug, Assassin bug, Winged bug or Kissing bug). Vector: Triatoma & Rhodnius (Cone nose Bug, Assassin bug, Winged bug or Kissing bug). Transmission: Cyclopropagative transmission. Infective stage: Metacyclic trypomastigotes. Mode of transmission Contamination of bite wound, skin abrasion or mucous membrane by faeces of infected vector; (Posterior station transmission,) & may be transmitted by - blood transfusion, - organ transplantation & - congenitally.

Morphology & Habitat In Man Amastigote T. cruzi exists in two forms in vertebrate hosts: Amastigote (dividing forms): in cardiac muscle & other tissues [glial cells of brain & macrophage] as small groups or cyst collections. Trypomastigote (non-multiplying form): in blood (few). ~20µm long, C-shaped with short undulating membrane & prominent kinetoplast [monomorphic].

Morphology [Cont.] 2. Two forms in the vector a- Epimastigote in the midgut. b- Metacyclic or short stumpy trypanosomes (infective stage) in hindgut and stool.

Life cycle of T. cruzi During a bite on Man or a RH (armadillos, dogs, cats, rodents, …), infected Triatoma release metacyclic trypomastigotes in feces ( stercorarian form). Parasites gain subcutaneous skin through wounds or mucosal membranes and pass into blood stream. They invade a variety of host tissues (especially striated muscles) and convert into dividing amastigotes. Liberated amastigotes will transform into monomorphic trypanomastigotes in the interstitial spaces & regain the blood stream These, if ingested by the vector, transform into epimastigotes first, then to infective trypomastigotes.

Pathogenesis & clinical picture Chagas’ disease has an acute and a chronic phase: Acute Chagas’ disease It is more common in infants & children. 1- Primary lesion At the site of bite, parasites multiply inside macrophage cells >>> erythematous, cutaneous indurated areas (Chagoma) occurs more on the face.

Acute Chagas’ disease (Cont.) 2- Romana's sign: When chagoma occurs round the eye >>> unilateral conjunctivitis, edema of eye lids & cheek.

The conjunctiva is the classical inoculation site for T The conjunctiva is the classical inoculation site for T. cruzi, a sleeping child scratching the site of bug bite, contaminates his fingers with bug faeces then rub his eyes. Within few days, the Trypanosomes proliferate locally causing unilateral face oedema of cheek, upper & lower eyelids, usually with conjunctivitis & enlargement of ipsilateral preauricular lymph nodes (Romana's sign) Death may occur or the patient may recover or pass to a chronic stage.