592 The Blood Flagellates 



quently, infections have been reported in T. uhleri (37), T. longipes 

 (74, 76), T. protracta (76) and Paratriatoma hirsuta (76) from Arizona, 

 and in T. gerstaeckeri (51), T. protracta (74) and T. heidemanni (53) 

 from Texas. The incidence of infection has approximated 33 per cent 

 in representative triatomids of Texas (68a). The strain of T. criizi from 

 T. heidemanni is infective for man under experimental conditions (53). 



The vectors of practical importance are the bugs which have become 

 adapted to life in association with man. Such bugs infest the primitive 

 huts and cabins common in rural South and Central America. During the 

 day the triatomids normally hide in cracks in walls, in bedding and 

 in furniture, as well as outdoors in piles of rubbish. Feeding on man or 

 other accessible mammals is usually a nocturnal activity. 



The ecological distribution of most infected triatomids indicates that 

 T. cruzi is a natural parasite of various wild mammals which constitute 

 a permanent and extensive reservoir. The cat was the first reservoir host 

 to be recognized (12). Natural infections have since been reported in 

 anteaters, armadillos, bats, dogs, ferrets, foxes, opossums, porcupines, and 

 squirrels in various parts of Central and South America. In the United 

 States, the San Diego wood rat of California was the first recognized 

 reservoir (73). More recently, armadillos, house mice, opossums, and 

 wood rats have been found infected in Texas (52); wood rats and white- 

 footed mice, in Arizona (76). 



Symptoms and pathology. Chagas' disease^ may occur in either an acute 

 or a chronic form. The acute type is most common in children under 

 10 years of age. The chronic form is the predominant type in adults, and 

 perhaps 70 per cent of these cases occur in the age group, 20-50. 



Following an incubation period, which has lasted 10-12 days in experi- 

 mental human infections (13), characteristic symptoms appear. The acute 

 case usually begins with a fever which is often moderate and may be 

 irregular or remittent. Another common early symptom is facial oedema, 

 sometimes accompanied by a conjunctivitis so severe that one eye cannot 

 be opened. This effect has been attributed to invasion of T. cruzi by 

 way of the conjunctiva. In severe cases, the oedema may become extensive, 

 involving the extremities and sometimes most of the body. Adenitis is 

 characteristic and often includes the submaxillary, preauricular, cervical, 

 inguinal, and axillary glands. There is usually a detectable swelling of 

 the liver and spleen, especially the former. A progressive anemia and a 

 rapid pulse are commonly noted. Physical weakness, loss of appetite, 

 diarrhea and headaches are frequently noted in children. Occasional 

 cases, usually fatal, show symptoms of acute meningoencephalitis. The 

 cardiac signs are usually not well defined and do not show the marked 

 changes in rhythm reported for many chronic cases. However, there is 



*A comprehensive discussion of symptoms and treatment has been published by 

 Laranja, Dias, and Nobrega (38a). 



