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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.

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This study aimed to identify 2,

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.

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 subéspecies de B. canis: B. canis canis, B. canis vogeli e B. canis rossi. A caracterização morfológica observada no exame direto de esfregaços sangüíneos 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 sangüíneos 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.

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.