Laboratory evaluation of the effects of triflumuron on the development of Rhodnius prolixus nymph

Studies were carried out to evaluate the efficacy of the growth regulator, triflumuron (TFM) (Starycide® sc 480 Bayer), for disrupting the development of Rhodnius prolixus fifth-instar nymph by oral, topical or continuous treatment. All treatments were able to induce high levels of mortality, delay development and molt inhibition. Oral treatment induced molt inhibition in all insects that survived at doses of 0.25, 0.50 and 5.0 mg/mL of a blood meal. The highest levels of both mortality in 24 h and molt inhibition were always observed after topical treatment. The lowest doses needed to obtain considerable biological effects were always observed after continuous treatment. In this way, the highest levels of mortality within 30 days were detected after continuous treatment, which also induced an extended inter-molting period, a lower number of over-aged nymphs and the highest level of molting in nymphs that survived. Moreover, the effects of TFM on insects were often displayed in a dose response manner. These results indicate that TFM acts as a potent growth inhibitor of R. prolixus nymphs and has the potential to be used in integrated vector control programs against hematophagous triatomine species.

Insecticidal activity of cerrado plant extracts on Rhodnius milesi Carcavallo, Rocha, Galvão & Jurberg ( Hemiptera: Reduviidae ), under laboratory conditions

A transmissão da doença de Chagas ocorre, principalmente, por meio de fezes de hemípteros hematófagos (Triatominae), os quais ingerem Trypanosoma cruzi ao se alimentarem do sangue de pessoas ou animais infectados. Para o controle dos triatomíneos, os piretróides são os principais inseticidas utilizados. Entretanto, algumas populações de insetos demonstraram resistência a determinados piretróides, indicando a necessidade do desenvolvimento de novos inseticidas eficazes no controle desses vetores. Assim, foi avaliada a atividade inseticida de 24 extratos vegetais em ninfas do quarto estádio de Rhodnius milesi Carcavallo, Rocha, Galvão & Jurberg, em condições de laboratório. Para o teste tópico, foram aplicados 50 µg de cada extrato nos tergitos abdominais de dez ninfas, em duplicata. Como controles, foram utilizados insetos tratados com etanol, acetona ou sem nenhum tipo de tratamento. Os triatomíneos foram observados durante 28 dias. Extratos hexânicos e etanólicos de Simarouba versicolor, Guarea kunthiana, Guarea guidonia e Talauma ovata causaram mortalidade entre 20% e 95% de R. milesi em comparação com os controles, onde não houve mortalidade dos insetos. Estes dados preliminares sugerem que o extrato etanólico da casca da raiz de S. versicolor e o extrato hexânico da raiz de G. guidonia, os quais foram responsáveis pela mortalidade de 95% e 75%, respectivamente, devem ser quimicamente investigados e monitorados por ensaios biológicos a fim de determinar seus componentes inseticidas, a serem utilisados como modelos moleculares ou como compostos biorracionais nos programas de controle de insetos.

Ticks, ivermectin, and experimental Chagas disease

Following an infestation of dogticks in kennels housing dogs used for long-term studies of the pathogenesis of Chagas disease, we examined the effect of ivermectin treatment on the dogs, ticks, trypanosome parasites, and also on triatomine vectors of Chagas disease. Ivermectin treatment was highly effective in eliminating the ticks, but showed no apparent effect on the dogs nor on their trypanosome infection. Triatominae fed on the dogs soon after ivermectin treatment showed high mortality, but this effect quickly declined for bugs fed at successive intervals after treatment. In conclusion, although ivermectin treatment may have a transient effect on peridomestic populations of Triatominae, it is not the treatment of choice for this situation. The study also showed that although the dogticks could become infected with Trypanosoma cruzi, this only occurred when feeding on dogs in the acute phase of infection, and there was no evidence of subsequent parasite development in the ticks.

Biological effect of 1-dodecanol in teneral and post-teneral Rhodnius prolixus and Triatoma infestans (Hemiptera: Reduviidae)

Topical application of 1-dodecanol was significantly more toxic against teneral first nymphs (1-3 h old) than post-teneral first nymphs (24 h old). The lethal dose ratios were 711,500 for Rhodnius prolixus and 3613 for Triatoma infestans. No significative difference between LD50 was found when 1-dodecanol was injected in recently hatched adult R. prolixus (1-4 h old) nor in older adults (24 h old). These values were similar to those calculated for deltamethrin (an effective triatomicide), showing that 1-dodecanol had no insecticidal properties when it was applied by injection. Topical application of high dose of 1-dodecanol (1 æg/i) on teneral first nymphs of R. prolixus, produced an interruption of the darkening process of the cuticle, and probably in the development of its physiological properties.

Susceptibility and resistance to insecticides of Chagas disease vector

Chemical control of Chagas disease vectors appears to be the best pratical way to reduce the incidence of the disease. DDT was intially tested in the 1950s for the campaigns of control of Chagas disease vectors. Its low level of effectiveness against triatomine caused the failure of these control actions. HCH was then introduced in the southem cone and Dieldrin in the north of Latinoamerica. Starting in the late 1960s anticholinesterasic organophosphorus and carbamate compounds were introduced in the control of Chagas vectors. The use of pyrethoriod compounds began in 1980. This family of insecticides is now the most important tool in triatomines control because of its favorable toxicological properties. Other types of insecticides also studied for Chagas vector control were the insect growth regulators and the antifeeding compounds. Because of the mode of action of these insecticides they are now considered just a potential complement of neurotoxic insecticides for integrated programmes of Triatomines control. Innovative formulations such as fumigant canister and insecticidal paints have been successfully developed in Latinoamerica with the World Health Organization support. Resistance to insecticides of triatomines is not a great problem in Chagas vectors. However, some resistant strains to pyrethroids have been found in Rhodnius prolixus from Venezuela and in Triatoma infestans from Brazil. Some cases of T. infestans incipient resistance to deltamethrin have been detected in Argentina. According to the control tools now available it is possible to expect the interruption of vector transmission of Chagas disease in the near future.

Efeito residual da deltametrina (k-othrine flow sc 50) no controle de Triatomíneos em Pirenópolis, Goiás / Residual effect of Deltamenthrin (k-Othrine flow sc 50) in the control of Triatominae bugs in the district of \"Pirenópolis,Goiás\",Brazil

Estudou-se o efeito da deltametrina (K-Othrine Flow SC 50) em 34 unidades habitacionais, domicílio e anexos, em Goianópolis, localizada no município de Pirenópolis, Goiás, Brasil. Estas habitaçÆes estavam infestadas por triatomíneos. As espécies encontradas foram Panstrongylus geniculatos, Rhodnius neglectus, Triatoma pseudomaculata e T. sordida infestando domicílio e/ou anexos. A deltrametrina foi rociada na dose de 25mg/m2, no ambiente domiciliar, nas 34 unidades e locais infestados por triatomíneos mantendo-as livres destes insetos por um período de um ano. Os levantamentos e as buscas de triatomíneos nas unidades habitacionas foram feitos nos 3§, 6§, 9§ e 12§ meses após o tratamento. Deste trabalho pode-se concluir que o efeito residual da deltrametrina persistiu durante um ano e foi letal para as espécies consideradas de pequeno porte, e que R. neglectus e T. sordida foram as espécies que evidenciaram o maior poder de invasåo domiciliar pela dispersåo ativa

Metodo alternativo para el control de vectores de la enfermedad de Chagas. efecto de la ivermectina / Alternative method for the control of Chagas disease vectors. Ivermectine efect.

Ninfas de Rhodnius prolixus fueron alimentadas sobre ratones inoculados con diferentes concentraciones de Ivermectina(1,000; 100; 10; 5 microgramos) y se comparó con grupo tetigo sin Ivermectina. La droga produjo una letalidad de 100 por ciento, 100 por ciento, 62.5 por ciento y 50 por ciento respectivamente. Se comenta su uso como método alternativo en el control de los vectores de la Enfermedad de Chasgas

Short-and long-term effects of proallatotoxin (ethoxyprecocene II) on Rhodnius prolixus females

A ovogênese e a postura de ovos pode ser inibida, durante o primeiro ciclo reprodutivo de Rhodnius prolixus, por um único tratamento com etoxiprecoceno II. Esta inibiçäo, se medida pelo crescimento dos ovócitos, maturaçäo de ovos e ovipostura, depende da dose do composto utilizado. A produçäo de ovos, no entanto, pode ser parcial ou totalmente restabelecida após dois subseqüentes repastos de sangue sem a droga. Estes dados sugerem que a açäo do etoxiprecoceno II sobre o corpus allatum näo é irreversível em fêmeas de Rhodnius prolixus

Efecto teratogénico y toxico de ácidos grasos de cadena corta insaturados, en Rhodnius prolixus / Teratogenic and toxic effect of unsaturated fatty acids of short chain, in Rhodnius prolixus

Se estudia el papel teratogénico de dos ácidos grasos insaturados de cadena corta, ácido octinoico y ácido undecilénico, sobre insectos de metamorfosis hemimetábola, Rhodnius prolixus (Hemiptera). La penetración de los ácidos, se realiza a través de la cutícula del abdomen y de los tarsos, se presenta como una acción independiente del grado de distensión de la misma, ya que sus efectos se registran tanto en los insectos repletos, como en los hambrientos; tanto en los tratados tópicamente como en aquellos donde la droga se aplicó al papel de soporte. Los ácidos estudiados aparentemente no afectan la formación de la cutícula, ni la melanización, como tampoco afecta el proceso de la muda. Los daños inducidos por estos ácidos se presentam al azar tanto en los apéndices locomotores como en los cefálicos, observándose un desplazamiento a la proboscide a medida que se incrementa la dosis. De las malformaciones en la proboscide, es el labio el mas dramáticamente dañado, aunque también se presentan daños en los otros apéndices bucales, aisladamente o junto con el daño del labio. El daño en los apéndices locomotores está frecuentemente desplazado al segundo y tercer par de patas, mientras que el par, fue el menos afectado. El ácido octinoico se comportó como teratogénico en las dosis que fueron letales para el insecto con el ácido undecilénico