Culture.—The trypanosome can be cultivated on Novy-MacNeal’s blood agar, and the cultural forms resemble those described in the bug.
Possible Reservoir.—Chagas thinks that probably the armadillo or “tatu” (Dasypus novemcinctus) may be the reservoir of T. cruzi. He also thinks that Triatoma geniculata is a transmitter; it lives in the burrows of the armadillo. Other carriers may be Triatoma infestans and T. sordida.
Clinical Features.—The trypanosomiasis of Brazil, produced by T. cruzi and spread by Triatoma spp. has received various names, such as oppilação, canguary, parasitic thyroiditis, and coreotrypanosis. It is also known as the human trypanosomiasis of Brazil, South American trypanosomiasis, and Chagas’ disease.
Chagas[88] reports two principal forms—acute and chronic. The acute infection is rare, and is characterized by increase in the volume of the thyroid gland, pyrexia, a sensation of crackling in the skin, enlarged lymphatic glands in the neck, axilla, etc., while the liver and spleen are increased in volume. Sclerosis of the thyroid gland is found at autopsy and fatty degeneration of the liver. During an attack of fever, trypanosomes are found in the blood. The acute form was only observed in children.
In the chronic form Chagas reports several varieties: (a) A pseudo-myxœdematous form, occurring in most cases, especially up to the age of 15. There is hypertrophy of the thyroid gland or at least signs of hypothyroidism, general hypertrophy of glands, disturbance of heart rhythm, and nervous symptoms. (b) The myxœdematous form is characterized by similar symptoms, especially by considerable swelling of the thyroid body, and myxœdema of the subcutaneous cellular tissue; sometimes there is a true pachydermic cachexia. (c) In the nervous form there are motor disturbances, aphasia, disturbances of intelligence or signs of infantilism, athetosis of the extremities and idiocy. There are also paralytic symptoms of bulbar origin, disturbances of mastication, phonation and deglutition, and in some cases convulsive attacks. (d) The cardiac form, characterized by disturbance of the heart rhythm. In all these forms the parasite is found at autopsy in the nervous substance, brain, bulb and heart.
Vianna (1911)[89] has studied the histopathology of the disease. Some of the chief points are: in the heart muscle destruction of the sarcoplasm, followed by interstitial myocarditis; in the central nervous system invasion of the neuroglia cells and inflammatory reaction; in the suprarenal capsule invasion of medulla or cortex; inflammatory reaction can also be seen in the kidneys, the hypophysis and thyroid gland.
Recently Chagas states[90] that “schizotrypanosomiasis” has been found in a child 15 to 20 days old, and that Trypanosoma cruzi has also been found in a fœtus—the mother being infected with the trypanosome. The trypanosomiasis can, then, be transmitted hereditarily.
Trypanosoma lewisi, Kent, 1881.
The trypanosome has a nucleus somewhat displaced anteriorly, about one-third of the way from the anterior (flagellar) end of the body, a relatively straight edge to the undulating membrane, and a rod-shaped blepharoplast (fig. 37, A). It averages about 25 µ long and 1·5 µ broad.
Much attention has been devoted in recent years to the elucidation of the life history of the rat parasite, Trypanosoma lewisi. It is usually non-pathogenic to its host. It has been shown that the trypanosome can be transmitted from rat to rat by the rat-flea, Ceratophyllus fasciatus, and by Ctenocephalus canis (the so-called dog-flea). (See also p. [92]). The flagellate may also persist, but doubtfully develop, in the rat-louse, Hæmatopinus spinulosus. These researches may now be summarized.