Home Economics American Trypanosomiasis Chagas Disease, Second Edition: One Hundred Years of Research
Primates nonautochthonous from the Americas/American continent
Macacus rhesus is one of the species of primates not autochthonous from the Americas used as model for Chagas disease studies. This species is phylogenetically considered more similar to the human genome (98% of homology) in relation to the species present in the American Continent.
M. rhesus were infected by the conjunctival route with metacyclic trypomasti- gotes from triatomines naturally infected92 in parallel with other animals infected with another strain isolated from human. The infection with the wild strain was verified in all animals. Romana signal was observed in some monkeys as well as chronic myocarditis with tissue parasitism. One case of megaesophagus93 with the presence of parasites in the muscular fibers in monkeys of this species with 10 years of infection was reproduced. One of the animals that survived for 29 years revealed discrete electrocardiographic changes, discrete increase of the cardiac area, and several indicators of autoimmune response, such as antibody antiendothelium, vases, interstice, and antiperipherical nerves.94 Other authors95 also reproduced the infection in three exemplars of rhesus monkeys inoculated with the Peru strain by the conjunctival route. Several signs of the acute phase of the infection were observed, such as patent parasitemia, ocular edema, decrease of red cells and hemoglobin, presence of IgM and IgG antibodies, tissue parasitism in several organs and tissues, and presence of parasites in ocular secretion.
An ultrastructural and cytochemical study of peroxidase and acid phosphatase in skin, lymph node, and heart muscle of rhesus monkeys was performed,96 providing evidence that these animals could be used as a reliable model to develop histopath- ological alterations of the human disease.
The evaluation over 3 years of the acute and chronic infection in rhesus monkeys 4- and 10-years-old, inoculated by subcutaneous route with low inoculum of Colombian strain was carried out.97 Several clinical symptoms typical of acute phase were observed. IgM and IgG anti-T. cruzi were observed from the third and fourth weeks of infection, respectively. Antibodies IgM disappeared in the ninth
month of infection and IgG increased during all period of study. Myocarditis and myositis were observed only in the acute and subacute phases. However all animals that were autopsied in the later phase presented characteristics of the indeterminate clinical form of the disease without any signal of evolutionary chronic chagasic cardiopathy.
Although primates have been the animals model that develop the acute phase of the infection most similar to that observed in human disease, the difficulty of obtaining, maintaining, and handling of these animals model in experimental conditions associated with the scarcity/rarity of data about the cardiac lesions of the chronic phase discourages the use of this animal model for the experimental study of Chagas disease.
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