In vitro activity of 3ß-O-tigloylmelianol from Guarea kunthiana A. Juss (Meliaceae) on oogenesis and ecdysis of the cattle tick Rhipicephalus (Boophilus) microplus (Canestrini) (Acari: Ixodidae).

We evaluated the effects of 3ß-O-tigloylmelianol from Guarea kunthiana A. Juss (Meliaceae) on oogenesis, as a larvicide and on ecdysis of the larvae and the nymphs of the cattle tick Rhipicephalus (Boophilus) microplus (Canestrini) (Acari: Ixodidae). On the oogenesis' test, 48 engorged females were divided into three groups, evaluated at 24, 48 and 72 h post-treatment. Half of the females were treated with 0.01% 3ß-O-tigloylmelianol diluted in distilled water and 5% dimethyl sulfoxide (DMSO), while the other half (controls) were exposed to distilled water and 5% DMSO. After treatment, the ovaries were weighed in order to measure the gonadosomatic index (GSI) and were also subjected to standard histological technical tests. On the larvicide and ecdysis' tests, 3ß-O-tigloylmelianol was tested at concentrations of 0.01, 0.005, 0.0025 and 0.00125%. Compared with the controls, there was a reduction of GSI of approximately 50% on the treated group, which started at 48 h post treatment. Overall, the protolimonoid 3ß-O-tigloylmelianol has caused a significant reduction in the number of oocytes. It has also caused alteration of the cytoplasmic and germinal vesicle diameters. Morphological changes, such as vacuolization, chorion irregularity which has modified the oocytes' morphology as well as alterations on the yolk's granules were also observed. The compound was not larvicide, however, interfered in the ecdysis of the larvae and the nymphs. This study shows that the protolimonoid 3ß-O-tigloylmelianol from G. kunthiana acts on oogenesis and ecdysis of R. (B.) microplus, but not as larvicide, indicating that it acts on the endocrine system of the tick.

Differences in the behavior of Rhipicephalus sanguineus tested against resistant and susceptible dogs.

To ascertain whether brown dog tick Rhipicephalus sp. infests resistant (beagle) and susceptible (English cocker spaniel) dogs differently, five animals of each breed were maintained in a kennel whose walls were infested with 7,000 larvae, 320 nymphs, 80 males and 80 females, in 3 infestations, at 10-day intervals. Five times more ticks were found on cocker spaniels (498) than on beagles (96). Substances were collected by rubbing pieces of clean flannel on the dogs for 15 min and these were tested for arrestment and attractiveness of ticks. Three choices were offered: cocker extract vs. control; beagle extract vs. control, and cocker extract vs. beagle extract. When allowed to choose between substances rubbed from dogs and a control, more ticks were arrested by extracts from the cockers than from beagles. In the arrestment tests with only a choice between substances from dogs of each breed, more ticks were arrested by cocker substances. To test for attraction, capsules containing adsorbent were used and the tests were carried out in a Y-olfactometer. Fifteen males and 15 females were tested, for each treatment. In the olfactometer, the ticks were not attracted to the odor of either breed, however the odor of the Beagle was apparently repellent. These results indicate that R. sanguineus can use substances from the dogs to differentiate susceptible English Cocker Spaniels from resistant Beagles.

Identification of non-host semiochemicals for the brown dog tick, Rhipicephalus sanguineus sensu lato (Acari: Ixodidae), from tick-resistant beagles, Canis lupus familiaris.

Studies have shown that the brown dog tick, Rhipicephalus sanguineus sensu lato, when fed on the beagle breed of dog, Canis lupus familiaris, development negatively affected in comparison with tick development after feeding on the English cocker spaniel breed. Thus leading to the suggestion that beagle dogs are be tick-resistant dogs. Behavioural studies have demonstrated that more ticks are attracted by extracts from cocker spaniels than from beagles and that the odour of beagles is a repellent. To test the hypothesis that resistant hosts produce repellent compounds, we undertook comparative chemical analysis on beagle odour and cocker spaniel extracts using coupled high-resolution gas chromatography-mass spectrometry (GC-MS) and also used Petri-dish and olfactometer behavioural assays to assess the response of ticks to identified non-host compounds. The beagle odour extracts contained almost three times as many chemical compounds as cocker spaniel samples. Several non-host compounds were identified, i.e. 2-hexanone, benzaldehyde, nonane, decane and undecane. In Petri-dish assays, 2-hexanone was repellent at 30 min at concentrations of 0.200 and 0.050 mg cm(-2), whilst at 10 min, the 0.100 mg cm(-2) concentration was repellent. Benzaldehyde repelled ticks at 30 min (0.200 mg cm(-2)) and at 5 min (0.050 mg cm(-2)). Undecane was repellent for R. sanguineus s.l. ticks for the first 5 min at the highest concentration tested. Nonane and decane did not show any significant repellency at any concentration or time evaluated. When 2-hexanone and benzaldehyde were combined, an increase in the repellency rate was observed, with activity comparable or better than N,N-diethyl-3-methylbenzamide (DEET). In olfactometer bioassays, a 1:1 mixture of 2-hexanone:benzaldehyde and DEET were repellent for R. sanguineus s.l. adults at the concentration of 0.200 mg cm(-2). This study identified non-host semiochemicals that mediate avoidance of the beagle dog breed by R. sanguineus s.l. This finding may enable development of new approaches to control this tick.

Study on cheliceral sensilla of the brown dog tick Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) involved in taste perception of phagostimulants.

Phagostimulants are chemical compounds that stimulate feeding. Some tick species are known to have pores in their inner cheliceral digits, called pit sensillum (ps), which are involved in taste perception. This study investigated the existence of ps in chelicerae of Rhipicephalus sanguineus ticks by scanning electron microscopy (SEM) and their involvement in the perception of phagostimulatory substances, such as the salts potassium chloride and sodium chloride (KCl and NaCl), sugars (glucose, sucrose and fructose), purines (guanine and hypoxanthine), the nucleotide adenosine triphosphate (ATP) and the tripeptide reduced glutathione (GSH), as well as their combinations at different concentrations. By means of scanning electron microscopy, a ps was observed at the expected location. Using a single-sensillum recording technique, strong activity by R. sanguineus cheliceral sensilla in response to glucose, ATP, GSH and high concentrations of salts was recorded. The responses to ATP and to KCl at 1M were multicellular, while the responses to the other stimulant compounds were monocellular. Glucose and GSH stimulated different neurons. The taste response of R. sanguineus chelicerae seemed to be selective, given that substances that were not expected to participate in this tick's biology were not perceived.

Acaricidal activity of ethanolic extracts of Stryphnodendron adstringens and Lafoensia pacari and oil resins from Copaifera sp. and Pterodon emarginatus against Sarcoptes scabiei var. suis / Atividade acaricida dos extratos etanólicos de Stryphnodendron adstringens Mart. e Lafoensia pacari A. St Hil., bem como das óleo-resinas de Copaifera sp. e Pterodon emarginatus Vogel, 1837 contra Sarcoptes scabiei var. suis

In vitro bioassay using Sarcoptes scabiei as a test microorganism is a viable method of study for diverse drugs with acaricidal properties. A great amount of assays proves the diverse and efficient biological activity of extracts and compounds from Brazilian savanna plants. This study had as main object, test and compare the acaricidal activity of four Brazilian Cerrado bioproducts: Stryphnodendron adstringens Mart., Copaifera sp., Lafoensia pacari A. St Hil. and Pterodon emarginatus Vogel, 1837. To perform this test S. scabiei mites were collected from crusts removed on ears of highly infected sows. The mites were selected and separated in Petri dishes with three different concentrations (25, 50 and 75%) of each bioproduct, to evaluate their potential acaricidal activity. The mortality of the mites was counted in each Petri dish every hour, during five hours. The statistical analyses demonstrated differences between the bioproducts tested. The oleoresin of Copaifera sp. and P. emarginatus presented the best results with 100% of mites mortality after treatment. The ethanolic extracts of S. adstringens and L. pacari demonstrated lower acaricidal activity when compared to the oleoresins, with little or no difference among the control groups tested. This bioassay demonstrated to be efficient, reliable, low cost and easy accomplishment. Oil resins from Copaifera sp. and P. emarginatus have in vitro acaricidal activity against adult females of S. scabiei var. suis.(AU)

O uso de Sarcoptes scabiei como microrganismo teste para bioensaio in vitro é um método de estudo viável para diversas drogas acaricidas. Muitos ensaios comprovam a diversidade e eficiência de atividade biocida de extratos e componentes presentes em plantas do cerrado brasileiro. Este trabalho objetivou testar e comparar a atividade acaricida de quatro bioprodutos do cerrado brasileiro: Stryphnodendron adstringens Mart., Lafoensia pacari A. St Hil., Copaifera sp. e Pterodon emarginatus Vogel, 1837. Para este estudo, ácaros S. scabiei foram colhidos em crostas removidas de orelhas de fêmeas suínas altamente infestadas. Os ácaros foram selecionados, separados e colocados em placas de Petri com três diferentes concentrações (25, 50 e 75%) de bioprodutos, para avaliar o potencial de atividade acaricida de cada um. Foi realizada a contagem da mortalidade dos ácaros em cada placa de Petri a cada hora, durante cinco horas. As análises estatísticas demonstraram diferenças entre os bioprodutos testados. As óleo-resinas de Copaifera sp. e P. emarginatus apresentaram os melhores resultados, com 100% de mortalidade dos ácaros após tratamento. Os extratos etanólicos de S. adstringens Mart. e L. pacari demonstraram menor atividade acaricida quando comparados as óleo-resinas, com pequena ou nenhuma diferença entre os resultados dos grupos controle. Este ensaio demonstrou ser uma ferramenta eficiente, confiável, de baixo custo e de fácil realização. As óleo-resinas Copaifera sp. e P. emarginatus possuem atividade acaricida in vitro sobre fêmeas adultas de S. scabiei var. suis.(AU)

Induction of complete courtship ritual in Amblyomma cajennense using 2,6-dichlorophenol at female-equivalent quantities.

In order to clarify the role of 2,6-dichlorophenol (2,6-DCP) in the courtship of Amblyomma cajennense, sexually mature males that had previously fed on rabbits were tested in bioassays. The males were released onto dummies treated with whole female extract or synthetic 2,6-DCP at a concentration of two female equivalents, or with hexane (control), and their responses were observed. In the presence of both the extract and 2,6-DCP, excitation was observed among the males, expressed in the form of touching and probing the dummy, and mounting occurred readily. The percentages of mounting (73%) and tipping over (60%) were equal in the two treatments and higher than in the control group (27 and 20%, respectively). Relatively short durations of mounting were recorded, and these were statistically similar in all treatments. Almost all instances of mounting resulted in tipping-over behavior. A few isolated cases of males that went directly to ventral positioning without mounting were observed. It was confirmed that 2,6-DCP alone is capable of mediation of mounting behavior in A. cajennense.

Cattle tick differentiates between the odors of Holstein Friesian and Nelore cattle / Carrapato de bovinos diferencia o odor de bovinos da raça Holandesa e Nelore

Although Rhipicephalus microplusmainly parasitizes bovines, different breeds can have variable parasite burdens, with indian breeds being less susceptible to tick infestation than european breeds. These ticks use pasture questing to seek out their hosts in the open spaces of their grassland habitats. Using an olfactometer bioassay, where the larva could express questing, the authors aimed to answer whether R. microplusexhibit different behaviors depending on the bovine breed. Sixteen larvae were individually exposed to the odors of five holstein friesian cattle, five nelore cattle, hexane (negative control) and 2-nitrophenol (positive control). The highest questing responses were observed to 2-nitrophenol and holstein odors. The lowest response was observed to the solvent and was statistically similar to nelore odors. It is possible to conclude that R. microplusexpress different questing behaviors depending on the odor of the breed perceived. This behavior can help R. microplusto avoid parasitizing nelore bovines and is biologically advantageous for the tick because it is known that ticks that feed on this host have impaired development.

Embora Rhipicephalus microplusparasite principalmente bovinos, diferentes raças podem ter cargas parasitárias variáveis, sendo os bovinos indianos menos suscetíveis a esse carrapato que os bovinos europeus. Este carrapato usa um comportamento de procura conhecido como questing para encontrar seu hospedeiro nas pastagens. Utilizando um teste em olfatômetro, onde a larva podia expressar o questing, objetivou-se responder se a larva podia expressar diferentes comportamentos dependendo da raça de bovino envolvida. Dezesseis larvas foram expostas para os odores de cinco bovinos holandeses, cinco nelores, hexano (controle negativo) e 2-nitrofenol (controle positivo). As mais altas respostas foram observadas para o 2-nitrofenol e odor de holandês. A mais baixa resposta foi observada para o solvente e foi estatisticamente similar ao odor de nelore. É possível concluir que R. microplusexpressa de forma diferente o comportamento de questing dependendo do odor da raça de bovinos percebido. Esse comportamento pode ajudar R. microplusa evitar parasitar bovinos nelore, o que é biologicamente vantajoso para o carrapato, uma vez que se sabe que carrapatos alimentados neste hospedeiro têm seu desenvolvimento comprometido.

Repellent activity of plant-derived compounds against Amblyomma cajennense (Acari: Ixodidae) nymphs.

Repellence responses of Amblyomma cajennense nymphs to callicarpenal, intermedeol, Hyptis suaveolens essential oil, extract of Melia azedarach, Cymbopogon nardus, Spiranthera odoratissima, Chenopodium ambrosioides, Ageratum conyzoides, Mentha pulegium, Ruta graveolens, and Memora nodosa were studied. Among these the extract of C. nardus stood out because of the long-lasting repellence, maintaining, in the highest concentration, 35h of protection against 90% of the nymphs. The essential oil of H. suaveolens and the extracts of C. ambrosioides and A. conyzoides showed good repellence index (66%) when applied in high concentrations. However, greater protection could be obtained at higher concentrations but with a shorter repellence time. Callicarpenal, intermedeol, extract of M. Pulegium, and M. nodosa leaves showed moderate repellence in high concentrations. Extracts from M. azedarach, R. graveolens, S. odoratissima, and M. nodosa roots showed little or no repellent effect. These results show that some plant extracts may represent a promising alternative in the control of infestations by A. cajennense.

Repellent activity of DEET against Amblyomma cajennense (Acari: Ixodidae) nymphs submitted to different laboratory bioassays.

This study was developed to evaluate the repellent activity of N,N-diethyl-3-methylbenzamide (DEET) against Amblyomma cajennense nymphs. Two repellent bioassays were compared and the effective concentration and repellent time were calculated. The fingertip test was accomplished to evaluate in vivo four concentrations of the compound (0.200; 0.100; 0.050 and 0.025 mg.cm⁻²) and the filter-paper bioassay to evaluate in vitro the two highest concentrations.The compound provided repellence higher than 90% in all concentrations and at least 95% repellency in the highest concentration over 5 hours. The effective concentration against 50% of tested nymphs (EC50) was 0.006 mg.cm⁻² and the EC99 was 0.036 mg.cm⁻². Those concentrations were lower than the ones obtained against other tick species, denoting the effectiveness of DEET against A. cajennense. The repellency time against 50% of the ticks (RT50) was 4.8 hours and the RT90 was 2.7 hours. Both bioassays were adequate to evaluate A. cajennense repellency and provided similar results; however the in vivo test is more appropriate to estimate the effective concentration and repellency time.

More about the role of 2,6-dichlorophenol in tick courtship: identification and olfactometer bioassay in Amblyomma cajennense and Rhipicephalus sanguineus.

This study aimed to identify 2,6-dichlorophenol (2,6-DCP) in Amblyomma cajennense and to evaluate its role in A. cajennense and Rhipicephalus sanguineus courtship. Hexanic extract from attractive females was purified by solid phase extraction and the phenol was identified by the single ion monitoring method using GC/MS. In an olfactometer, the responses of A. cajennense and R. sanguineus males to females, control rubber septa or rubber septa impregnated with 2,6-DCP at 50, 500, and 5000 ng, respectively, were studied. 2,6-DCP was identified in A. cajennense extract and the males oriented themselves toward the concentration of 500 ng. These septa and the females were recognized as copula partners. The septa treated with 2,6-DCP did not attract and were not even recognized by the R. sanguineus males, whereas the females were recognized. Due to the presence of 2,6-DCP in A. cajennense and the results of biological bioassays, it was concluded that this compound acts as an attractant and mounting sex pheromone in this tick, but it does not play any role in R. sanguineus courtship.

Induction of complete courtship ritual in Amblyomma cajennense using 2,6-dichlorophenol at female-equivalent quantities / Indução dos comportamentos de cortejo em Amblyomma cajennense pelo 2,6-diclorofenol em quantidades equivalentes às das fêmeas

In order to clarify the role of 2,6-dichlorophenol (2,6-DCP) in the courtship of Amblyomma cajennense, sexually mature males that had previously fed on rabbits were tested in bioassays. The males were released onto dummies treated with whole female extract or synthetic 2,6-DCP at a concentration of two female equivalents, or with hexane (control), and their responses were observed. In the presence of both the extract and 2,6-DCP, excitation was observed among the males, expressed in the form of touching and probing the dummy, and mounting occurred readily. The percentages of mounting (73 percent) and tipping over (60 percent) were equal in the two treatments and higher than in the control group (27 and 20 percent, respectively). Relatively short durations of mounting were recorded, and these were statistically similar in all treatments. Almost all instances of mounting resulted in tipping-over behavior. A few isolated cases of males that went directly to ventral positioning without mounting were observed. It was confirmed that 2,6-DCP alone is capable of mediation of mounting behavior in A. cajennense.

Visando elucidar o papel do 2,6-diclorofenol (2,6-DCF) no cortejo de Amblyomma cajennense, machos sexualmente maduros, previamente alimentados em coelhos, foram avaliados em testes biológicos. Os machos foram liberados sobre manequins tratados com um extrato de fêmeas, ou com 2,6-DCF sintético na concentração equivalente a duas fêmeas, ou com hexano (controle), e suas respostas foram observadas. Na presença do extrato e do 2,6-DCF, a excitação dos machos foi expressa na forma de toques e sondagens, e a monta ocorreu rapidamente. As porcentagens de respostas observadas nos dois tratamentos foram iguais, sendo a monta (73 por cento) e retorno na superfície ventral (60 por cento) mais altos que no controle (27 e 20 por cento, respectivamente). Foram observados períodos de monta relativamente curtos, sendo esses estatisticamente iguais em todos os tratamentos, e quase todos resultando em posicionamento ventral. Alguns casos isolados de posicionamento ventral sem monta foram observados. Foi confirmado que o 2,6-DCP sozinho é capaz de mediar o comportamento de monta de A. cajennense.

Repellent activity of DEET against Amblyomma cajennense (Acari: Ixodidae) nymphs submitted to different laboratory bioassays / Atividade repelente do DEET contra ninfas de Amblyomma cajennense (Acari: Ixodidae) em bioensaio laboratorial

This study was developed to evaluate the repellent activity of N,N-diethyl-3-methylbenzamide (DEET) against Amblyomma cajennense nymphs. Two repellent bioassays were compared and the effective concentration and repellent time were calculated. The fingertip test was accomplished to evaluate in vivo four concentrations of the compound (0.200; 0.100; 0.050 and 0.025 mg.cm-2) and the filter-paper bioassay to evaluate in vitro the two highest concentrations. The compound provided repellence higher than 90 percent in all concentrations and at least 95 percent repellency in the highest concentration over 5 hours. The effective concentration against 50 percent of tested nymphs (EC50) was 0.006 mg.cm-2 and the EC99 was 0.036 mg.cm-2. Those concentrations were lower than the ones obtained against other tick species, denoting the effectiveness of DEET against A. cajennense. The repellency time against 50 percent of the ticks (RT50) was 4.8 hours and the RT90 was 2.7 hours. Both bioassays were adequate to evaluate A. cajennense repellency and provided similar results; however the in vivo test is more appropriate to estimate the effective concentration and repellency time.

Este estudo foi conduzido com o objetivo de avaliar a atividade repelente do N,N-diethyl-3-methylbenzamide (DEET) sobre ninfas de Amblyomma cajennense. Dois bioensaios para a avaliação de repelência foram comparados e cálculos da concentração eficaz e do tempo de repelência foram realizados. Foram empregados o bioensaio da ponta do dedo, para avaliação in vivo de quatro concentações do químico (0,200; 0,100; 0,050 e 0,025 mg.cm-2) e o bioensaio do papel filtro, para a avaliação in vitro das duas concentrações mais altas. O composto conferiu mais de 90 por cento de repelência em todas as concentrações utilizadas e 95 por cento de repelência por mais de cinco horas na maior concentração. A concentração do composto efetiva contra 50 por cento das ninfas testadas (CE50) foi de 0,006 mg.cm-2 e a CE99 foi de 0,036 mg.cm-2. Estas concentrações são mais baixas do que as observadas em outras espécies de carrapatos, denotando a efetividade do princípio contra A. cajennense. O tempo de repelência de 50 por cento dos carrapatos (TR50) foi de 4,8 horas e o TR90 de 2,7 horas. Os dois bioensaios avaliados permitiram a observação de percentuais de repelência igualmente altos e se mostraram adequados para tal avaliação, sendo que o teste in vivo é mais indicado para cálculo da concentração eficaz e da duração da repelência.

More about the role of 2,6-dichlorophenol in tick courtship: identification and olfactometer bioassay in Amblyomma cajennense and Rhipicephalus sanguineus

This study aimed to identify 2,6-dichlorophenol (2,6-DCP) in Amblyomma cajennense and to evaluate its role in A. cajennense and Rhipicephalus sanguineus courtship. Hexanic extract from attractive females was purified by solid phase extraction and the phenol was identified by the single ion monitoring method using GC/MS. In an olfactometer, the responses of A. cajennense and R. sanguineus males to females, control rubber septa or rubber septa impregnated with 2,6-DCP at 50, 500, and 5000 ng, respectively, were studied. 2,6-DCP was identified in A. cajennense extract and the males oriented themselves toward the concentration of 500 ng. These septa and the females were recognized as copula partners. The septa treated with 2,6-DCP did not attract and were not even recognized by the R. sanguineus males, whereas the females were recognized. Due to the presence of 2,6-DCP in A. cajennense and the results of biological bioassays, it was concluded that this compound acts as an attractant and mounting sex pheromone in this tick, but it does not play any role in R. sanguineus courtship.

Diagnóstico parasitológico e molecular da babesiose canina na cidade de Goiânia-GO / Parasitologic and molecular diagnosis of canine babesiosis in Goiânia, Brazil

A babesiose canina é uma enfermidade causada por hematozoários intraeritrocitários obrigatórios do gênero Babesia. As espécies Babesia canis e Babesia gibsoni apresentam ampla distribuição geográfica. Mundialmente são reconhecidas três subespécies de B. canis: B. canis canis, B. canis vogeli e B. canis rossi. A caracterização morfológica observada no exame direto de esfregaços sanguíneos permite a diferenciação entre B. canis e B. gibsoni, mas não entre as subespécies de B. canis B. gibsoni é um parasito pequeno, normalmente encontrado em formas isoladas no interior das hemácias. B. canis é um parasito do grupo das grandes babesias, que geralmente se apresenta aos pares. O Objetivo deste trabalho foi identificar, por meio de estudos morfológicos e moleculares, as espécies e subespécies de Babesia envolvidas nos casos clínicos de babesiose canina na cidade de Goiânia. Amostras de sangue foram colhidas para a preparação de esfregaços sanguíneos e apenas as amostras positivas foram encaminhadas para a extração de DNA, totalizando 30 amostras. A avaliação microscópica dos esfregaços revelou formas intra-eritrocitárias variadas de trofozoítos e merozoítos e, em algumas amostras, prevaleceram formas com valores próximos a B. gibsoni; em outras, formas equivalentes a B. canis. O diagnóstico subespécie-específico por PCR confirmou a identidade molecular de B. c. vogeli nas 30 amostras avaliadas. Dessa forma foi possível concluir que, apesar das diferenças morfométricas verificadas entre as amostras procedentes da cidade de Goiânia, todas foram identificadas como subespécie B. c. vogeli.

Seasonal dynamics of Rhipicephalus sanguineus (Acari: Ixodidae) in dogs from a police unit in Goiânia, Goiás, Brazil

The seasonal dynamics of Rhipicephalus sanguineus ticks was developed in dogs from a Police Unit in Goiânia, Goiás, Brazil, from July 2001 to July 2002. The study was carried out on seven naturally infested dogs (two English Cocker Spaniels and five mongrel dogs), with ages between six months and 10 years. Every two weeks, the numbers of feeding larvae, nymphs, and adults were determined. Dogs showing infestation levels above 500 adult ticks received three acaricide treatments. Considering that the treatments had affected the development of some peaking populations of ticks, it was inferred the occurrence of the following peaks: - larvae (four peaks): from August to November, from November to February, from March to May, and from May to July; - nymphs (five peaks): from July to September, from October to December, from December to February, from March to May, and from June to July; - adults (four peaks): from July to October, from October to January, from January to March, and from April to July. The occurrence of these consecutive peaks of activity of each stage of R. sanguineus may indicate that this tick can develop up to four generations per year in Goiânia. On the other hand, if the acaricide treatment did not interfere with the development of R. sanguineus peaks, more than four peaks of each stage have occurred on the dogs. In this case, it is acceptable to infer that more than one population of R. sanguineus was developing within the kennel concomitantly. The mean numbers of each tick stage was similar in the different seasons. The main attachment sites were located on the neck, chest, forelegs, armpits, ears, between toes and on the head. The number of adult ticks feeding on English Cocker Spaniel dogs was 1.4 to 11.5 times higher than that feeding on mongrel dogs.

O estudo de dinâmica sazonal de Rhipicephalus sanguineus foi desenvolvido em cães de uma Unidade da Polícia de Goiânia, Goiás, Brasil, de julho de 2001 a julho de 2002. Sete cães naturalmente infestados com R. sanguineus (dois da raça Cocker Spaniel Inglês, e cinco cães sem raça definida), com idades variando de 6 meses a 10 anos, foram utilizados no monitoramento da infestação. A cada duas semanas, o número de larvas, ninfas e adultos parasitando os animais era contado. Três tratamentos acaricidas foram feitos nos cães que tiveram níveis de infestação de 500 adultos. Considerando que os tratamentos interferiram no desenvolvimento de alguns picos do carrapato, pôde-se inferir que ocorreram nos quatro picos de larvas: de agosto a novembro, de novembro a fevereiro, de março a maio e de maio a julho; cinco picos de ninfas: de julho a setembro, de outubro a dezembro, de dezembro a fevereiro, de março a maio e de junho a julho, e quatro picos de adultos: de julho a outubro, de outubro a janeiro, de janeiro a março e de abril a julho. A ocorrência destes picos consecutivos de cada estágio pode indicar que o R. sanguineus realiza quatro gerações anuais em Goiânia. Por outro lado, se os tratamentos não interferiram no desenvolvimento dos picos de atividade, mais de quatro picos de cada estágio ocorreram nos cães. Então, é aceitável supor que mais de uma população de R. sanguineus estava se desenvolvendo no canil, ao mesmo tempo. O número médio de carrapatos de cada estádio foi similar nas estações do ano. Os sítios preferenciais de fixação foram o pescoço, o peito, as patas, as axilas, as orelhas, os espaços interdigitais e a cabeça. O número de carrapatos contados nos cães da raça Cocker Spainel Inglês foi de 1,4 a 11,5 vezes maior que o número observado nos cães sem raça definida.

Resistência acaricida em larvas de Rhipicephalus sanguineus (Acari: Ixodidae) de Goiânia-GO, Brasil / Acaricide resistence in Rhipicephalus sanguineus (Acari: ixodidae) larvae from Goiânia-GO, Brazil

Fêmeas ingurgitadas de Rhipicephalus sanguineus foram colhidas em cães provenientes de diferentes regiões de Goiânia e incubadas para a produção de larvas. Usando-se um teste de imersão, larvas de 7 a 21 dias de idade foram testadas ante os seguintes acaricidas e concentrações (em ppm): amitraz (250, 125, 62,5 e 31,2), coumafós (500, 250, 125 e 62,5), cipermetrina (150, 75, 37,5 e 18,7), deltametrina (25, 12,5, 6,2 e 3,1) e fipronil (312, 156, 78, 39 e 19,5). Cálculos das DL50 e DL99 foram feitos por meio do programa de análise do probito. Cepas com DL99 acima daquelas recomendadas pelo fabricante ou pela literatura foram consideradas como resistentes. Nenhuma das 15 amostras testadas ante o amitraz teve a DL99 superior à concentração recomendada. Ante a deltametrina, a cipermetrina e o coumafós, nove (75por cento), sete (78por cento) e sete (78por cento) amostras, respectivamente, tiveram DL99 superior à recomendada. As DL50 variaram de 4 a 16 ppm, 0,3 a 3,2 ppm, 1 a 20 ppm e 17 a 75 ppm em relação a amitraz, deltametrina, cipermetrina e coumafós, respectivamente. Houve mortalidade de 100por cento das larvas testadas em todas as concentrações do fipronil. Estes resultados demonstram que a maioria das cepas de R. sanguineus de Goiânia apresentaram resistência à cipermetrina, à deltametrina e ao coumafós. Não se verificou resistência ao amitraz na população de R. sanguineus estudada.