(Figures 5-36 to 5-37)
The reduviidae contains a subfamily Triatominae which contains the genera of blood-sucking insects responsible for the transmission of Trypanosomacruzi; there are some 111 species in this subfamily. Most of the other members of the Reduviidae are predatory bugs that are called assassin bugs. The triatomin bugs have a bite that is relatively painless while that of the assassin bugs is painful. The triatomins, like bedbugs, hide in various locations in nests and houses and feed on their hosts typically at night. Triatomins are mainly found in the American tropics but some species are found in the areas of the Nearctic. One species, Triatomarubrofasciata, has been carried by humans to various port cities areound the world, including Asia and Africa. There are rare representatives that are indigenous to parts of the Orient and northeastern Australia.
The triatomins are large insects that as adults are often over an inch in length (Fig. 5-36). They have a large antreriorly protruding head that bears two large fowarding projecting antenae and large eyes. The long piercing mouthparts are folded back under the head of the bug (Fig. 5-37). The adults have well developed wings. Often the bugs have brightly colored red , yellow, orange, and black borders on the lateral edges of the abdomen and on the anterior portion of the wing covers.
The triatomins undergo simple metamorphosis and the nymphs resemble the adults, except that they lack wings and sexual structures. All stages require a blood meal and the adults will feed repeatedly. The bugs are capable of long periods of starvation. The blood meal is required for egg production, and the eggs are laid often in the cracks but without any glutinious material being secreted as in the Cimicidae. Some bugs, e.g., Rhodniusprolixus, has a tendency to defecate sooner than other bugs examined, this defecation is important to remove excess water from the blood meal to reduce its weight. This rapid defecation which often occurs on the host is a one reaons why some bugs may be better vectors of a posterior station parasite such as Trypanosomacruzi which is passed in the feces of the bug. Another aspect that determines how well certain bugs serve as vectors is how easily they enter human habitations. Some bugs, especeially those in Mexico, Central and South America are primarily domestic.
Triatomin bugs will feed on cats, and cats have been implicated as reservoirs of Trypanosomacruzi. There has been very little work done on the presentation of the disease in cats. Gurtler et al. (1993) examined the role of cats and dogs in the transmission of Trypanosomacruzi in Argentina. Of cats in 31 households, 39.3% were infected with this trypanosome and bug infection rates in the vector Triatomainfestans were significantly associated witht he present of infectected cats. A study in Oaxaca, Mexico, revealed that 13% of Triatomabarberi collected from village houses had fed on cats, 70% had fed on rodents, 36% had fed on humans, and multiple feedings were found in 48% of the bugs; 72% of the bugs were infected with Trypanosomacruzi (Zarate et al., 1980). Panstrongylusmegistus has been shown in the Santa Catarina Island of Brazil to feed on the feline hosts by the examination of blood meals by precipitin tests (Steindel et al., 1994).
Gurtler RE, Cecere MC, Ptersen RM, Rubel DN, Schweigmann NJ. 1993. Chagas disease in north-west Argentina: association between Trypanosomacruzi parasitaemia in dogs and cats and infection rates in domestic Triatomainfestans. Trans Roy Soc Trop Med Hyg 87:12-15.
Stendel M, Toma HK, Carvalho-Pinto CJ, Grisard EC, Schlemper BR. 1994. Colonizacao de ecotopos artificiais pelo Panstrongylus megistus na Ilha de Santa Catarina, Florianopolis, Santa Catarina, Brasil. Rev Inst Med Trop Sao Paulo 36:43-50.
Zarate LG, Zarate RJ, Tempelis CH, Goldsmith RS. 1980. The biology and behavior of Triatomabarberi (Hemiptera: Reduviidae) in Mexico. I. Blood meal sources and infection with Trypanosomacruzi. J Med Ent 17:103-116.
Figure 5-36. Triatomaprotractor adult shown next to a US penny for scale.
Figure 5-37. Mouthparts of a triamin bug folded back under the head.