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An intensive enzootic cycle of Borrelia burgdorferi was seen in populations of the Mexican wood rat, Neotoma mexicana, and Ixodes spinipalpis ticks in northern Colorado. Cultures of rodent ear tissue and ticks yielded 63 spirochetal isolates: 38 N. mexicana, 2 Peromyscus difficilis, and 23 I. spinipalpis. All 63 isolates were identified as B. burgdorferi sensu lato by polymerase chain reaction; a representative subset was characterized as B. burgdorferi by SDS-PAGE and immunoblotting. A tick-derived spirochete isolate was infectious to laboratory mice and I. scapularis, the principal vector of Lyme disease in endemic areas of the United States. The risk of human contact with infected I. spinipalpis appears to be minimal from this epidemiologically silent focus in northern Colorado, since this tick is restricted to wood rat nests in this semiarid environment.

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The landscape ecology of Lyme disease was studied in 1989 on 67 residences in an endemic area of Armonk, Westchester County, a northern suburb of New York City. Four main habitat types were defined, and each property was surveyed for immature and adult lxodes dammini ticks; 98.6% of 1,790 ticks collected were I. dammini. Overall, 67.3% were collected from woods, 21.6% from ecotone (unmaintained edge), 9.1% from ornamental vegetation, and 2% from lawns. Larval ticks were concentrated in woods, but nymphs and adults were widely dispersed in all habitats. Tick abundance was positively correlated with property size. Larger properties (greater than or equal to 0.5 acre) were more likely to have woodlots and, hence, more ticks. Dark-field and direct fluorescent microscopic examination of tick midgut tissues revealed that 29.6% of nymphs and 49.7% of adults were infected with Borrelia burgdorferi. Infected nymphs and adults were found on 36% and 60% of properties, respectively. These data indicate that the abundance of ticks capable of transmitting Lyme disease spirochetes is related to landscape features of the suburban residential environment.

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We studied the association between human incidence of Trypanosoma cruzi infection and household infestation density of Panstrongylus megistus in Castro Alves, Bahia, Brazil. During a 9-year period, 19 persons seroconverted; 17 were children, 17 lived in nonplastered houses, and 13 lived in houses infested with triatomines. Although 6 seroconverting persons lived in houses where triatomines could not be found, the risk of seroconversion was significantly greater in infested houses and 16 times greater in densely infested houses (greater than 15 bugs/person-hour of search). The highest rate of seroconversion (6/100 person-years exposure) occurred in houses containing the greatest number of bugs infected with T. cruzi (greater than 6 infected bugs/person-hour). These observations suggest that vector control measures could have a dramatic impact on transmission of T. cruzi by P. megistus.

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Foram comparados quatro metodos para detectar a infestacao dos domicilios por triatomineos: 1)coleta manual; 2) coleta manual apos a aplicacao de piretro; 3)procura de ovos viaveis; 4)caixas de GomezNunez. A coleta manual foi o metodo mais sensivel (23% de infestacao), seguido da aplicacao de piretro (21%), das caixas de Gomez-Nunez(15%) e finalmente dos ovos via veis (12%). Cerca de 10% das casas infestadas foram exclusivamente positivas no teste das caixas de Gomez-Nunez.Ainda mais 6 das 7 casas positivas exclusivamente pelo metodo de Gomez-Nunez estavam localizadas numa area recentemente borrifada, onde a densidade de Panstrongylus megistus era muito baixa. A inspecao das caixas de Gomez-Nunez 12 semanas apos a aplicacao de inseticida foi duas vezes mais efetiva do que a inspecao 6 semanas apos a aplicacao de inseticida. As manchas de fezes eram as evidencias mais comuns para indicar a presenca de P. Megistus dentro da caixa de Gomez-Nunez. A caixa de Gomez-Nunez e um complemento util da coleta manual para detectar a infestacao domiciliar pelo P. megistus, especialmente nas areas onde a den sidade de triatomineos e baixa. Contudo, a utilidade das caixas de Gomez-Nunez deve ser levada em consideracao com referencia ao tempo e trabalho que requerem

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Experimentamos o novo inseticida bendiocarb para o combate ao Panstrongylus megitus, principal vetor da doenca de Chagas, em uma area endemica do Estado da Bahia, Brasil. Uma das partes da experiencia constou da aplicacao de 0,4 g/m2 de bendiocarb a 80% pelas equipes de guardas borrifadores oficiais. A taxa de infestacao das casas foi reduzida de 18% para 7%, seis meses apos a aplicacao do inseticida, e a densidade de P. megistus caiu de 7 para 1,5 exemplares por hora. A outra parte constou da utilizacao da mao-de-obra dos habitantes na inspecao de suas casas para triatomineos, da aplicacao por meio de uma pequena bomba manual, de bendiocarb a 20% sempre que observassem triatomineos. A taxa de infestacao das casas foi reduzida de 48% para 14% e a densidade de P. megistus caiu de 12 para menos de 1 exemplar por hora. Apesar da concentracao mais fraca, o bendiocarb aplicado com a colaboracao da populacao, apresentou resultados mais eficientes, provavelmente devido a constante vigilancia com que ficou a area, havendo consequentemente, maior frequencia na aplicacao do inseticida. O metodo de combate aos vetores com a participacao da populacao mostrou-se mais eficiente e menos dipendioso. Dessa forma, se adotado pelos servicos de combate as endemias no Brasil, talvez venha a ser a solucao para o descontinuidade das campanhas contra a doenca de Chagas

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In order to determine whether host availability limits triatomine population growth, 5th-stage Panstrongylus megistus were maintained in feeding chambers containing 0, 1, 2, or 3 mice. During the 5-day feeding period, triatomines exposed to two or three mice gained significantly more weight than did bugs exposed to one mouse. In addition, half of the bugs exposed to two or three mice molted, as compared to one-fifth of the P. megistus exposed to one mouse. Thus, weight gain and molting were related to host density. In contrast, bug mortality was related to the triatomine-mouse ratio, being greatest among bugs exposed to one mouse. Twenty-nine nonplastered mud-stick houses in a Chagas' disease endemic area were censused and examined for triatomines. About 70% of houses with greater than or equal to 4 persons contained dense bug populations, while only 20% of houses with 1-3 persons were densely infested. Moreover, blood-meal identifications demonstrated that two-thirds of the P. megistus collected from these houses fed on man. The density of triatomines present in infested houses is related to the number of persons available as hosts.

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