Human parasitism by the brown dog tick Rhipicephalus sanguineus sensu lato (s. l.), an important parasite in medical and veterinary sciences, is only rarely reported in the American continent. The present investigation reports a R. sanguineus s. l. male tick parasitizing a human in the city of Campo Grande, State of Mato Grosso do Sul, west-central Brazil. This observation is of public health relevance, since R. sanguineus s. l. ticks are known as vectors of spotted fever group rickettsiae to dogs and humans.

Infestations of brown dog ticks (Rhipicephalus sanguineus) are difficult to control. This study aimed to evaluate the efficacy of phoxim and deltamethrin against R. sanguineus in vitro and in vivo. In vitro studies, the evaluation involved the exposure of R. sanguineus adults, nymphs, and larvae to phoxim (1 ml/1000 ml) and deltamethrin (1 ml/1000 ml) observations were recorded for 24 hours, and the eggs were assessed and compared with a negative control tick group that had been exposed to water for 14 days,  In vivo studies, twenty local dogs have been divided into four groups of five each: The 1st group was non-infested dogs; the 2nd group is infested untreated dogs; the 3rd group was infested dogs and treated with a therapeutic dose of phoxim; and 4th  group  was infested dogs and treated with a therapeutic dose of deltamethrin. Results revealed that phoxim was more effective than deltamethrin on adult of R. sanguineus, while deltamethrin appeared to be more effective than phoxim on nymphs and larvae of R. sanguineus. Both acaricides significantly inhibited egg hatchability of R. sanguineus with the same potency.

A total of 103 blood samples from pet dogs around Ipoh were screenedfor common blood protozoa. A total of 14 samples were found positive for Erhlichia canis and one sample was found positive for microfilaria of Dirofilaria immitis. Both these diseases are transmitted by vectors; ticks (Rhipicephalus sangiuneus) and mosquitoes respectively. In the hot and wet tropical environment where vectors are abundant, pet care, hygiene and regular screening will help veterinarians detect these infections early to facilitatetreatment.

Rhipicephalus sanguineus and Ctenocephalides spp. on kennelled dogs, seasonal prevalence and mean numbers and percentages of immature and adult ticks and of fleas recovered from various sites on dogs

A two-year-old female Dobermann dog was presented to the Veterinary Clinical Complex, Veterinary College and Research Institute, Orathanadu, Tamil Nadu Veterinary and Animal Sciences University, with a history of unilateral epistaxis, dullness, and inappetence. Clinical examination revealed the presence of ticks all over the body surface and they were morphologically identified as Rhipicephalus sanguineus. Blood samples were analyzed for haemato-biochemical parameters and blood parasites. Giemsa stained blood smear revealed the presence of morulae inclusion over monocytes. The dog was treated with a triple therapy protocol, and supportive care was provided. The dog exhibited signs of recovery from the third day of treatment. Follow-up examination on the seventh day revealedthe absence of morulae stage of Ehrlichia spp. and a gradual increase in blood cells. 

<p>Dogs', guinea pigs' and hamsters’ local skin reaction to the attachment and feeding of the tick <em>Rhipicephalus sanguineus </em>were analysed under light microscopy. The hosts were either tick-bite naive, previously infested or vaccinated with crude unfed adult tick extract. Biopsies were taken at the end of each infestation. Changes common to every host, regardless of experimental group, included presence of tick or its mouthparts embedded in a cone of cementum at the surface of the skin, epidermal hyperplasia, hyperkeratosis and acanthosis, edema and copious inflammatory cell infiltration in the dermis, underneath the tick attachment site. Dogs in all experimental groups reacted with an almost exclusive PMN neutrophil accumulation, while guinea pigs showed a predominantly mononuclear cell infiltration in every experimental group. Hamsters suffering first infestations had a mainly neutrophilic infiltration, showed a predominantly mononuclear cell infiltration in response to multiple infestations, and when previously vaccinated this host had a predominantly eosinophilic infiltration. The persistence of PMN neutrophils in dogs suggest a control of the local immune inflammatory response by the tick. The predominantly eosinophilic infiltration in previously vaccinated hamsters might indicate that different immune mechanisms were triggered by infestation and vaccination.</p> | Analisou-se, sob microscopia óptica, reação cutânea de cães, hamsters e cobaia à fixação e alimentação do carrapato <em>Rhipicephalus sanguineus. </em>Os hospedeiros empregados foram previamente infestados ou vacinados com extrato total de carrapato adulto não alimentado ou eram livres de contato anterior com o carrapato. Biópsias foram obtidas ao final de cada infestação. As alterações comuns a todos os hospedeiros, independente do grupo experimental, incluíram a presença de carrapato ou de suas peças bucais embutidos em um cone de cemento na superfície da pele, hiperplasia da epiderme, hiperqueratose e acantose, edema e infiltração celular inflamatória intensa na derme abaixo do ponto de fixação do carrapato. Os cães, em todos os grupos experimentais, reagiram com um acúmulo praticamente exclusivo de neutrófilos polimorfonucleares enquanto cobaias exibiram uma infiltração celular predominantemente mononuclear nas diversas condições experimentais. Hamsters sofrendo primeira infestação apresentaram uma infiltração predominantemente neutrofílica, infiltração predominantemente mononuclear em resposta a múltiplas infestações e, quando vacinados, uma infiltração preponderantemente eosinofílica. A persistência de neutrófilos nos cães sugere um controle local da resposta inflamatória imune pelo carrapato. A infiltração predominantemente eosinofílica em hamsters vacinados poderia indicar que mecanismos imunes diferentes foram desencadeados pela infestação e vacinação.

<p>Tick-bite naive experimental groups of dogs, hamsters and guinea pigs were infested three times with adult ticks <em>Rhipicephalus sanguineus </em>and the acquired resistance, based on the variation of some biological parameters of the female tick was compared. The results showed that hamsters and mainly guinea pigs develop a very efficient immunity to this tick species as demonstrated by a very significant drop in the efficiency rate of female ticks in converting their food reservoir to eggs and larvae from the first to the second and third infestations. At the same time, dogs were unable to display such a resistance. Female tick performance was similar throughout the infestations in this host; there was even a tendency of improvement of the performance with the succession of infestations. These results underline the need of comparative studies on the acquired resistance to ticks involving natural and unnatural hosts as a way of putting in evidence defence mechanisms which might be altered or hidden in natural host - parasite relationships.</p> | <p>Grupos experimentais de cães, hamsters e cobaias sem contato anterior com carrapatos, sofreram três infestações consecutivas por carrapatos <em>Rhipicephalus sanguineus </em>adultos e a resistência adquirida comparada com base na variação de alguns dos parâmetros biológicos da fêmea do carrapato. Os resultados mostraram que hamsters e cobaias principalmente, desenvolvem uma reação imune muito eficiente a esta espécie de carrapato como demonstrado por uma queda altamente significativa na taxa de eficiência da fêmea em converter sua reserva alimentar em ovos e larvas da primeira para as segunda e terceira infestações. Já cães foram incapazes de desenvolver tal resistência. Neste hospedeiro a performance das fêmeas dos carrapatos foi similar durante todas as infestações, havendo até uma tendência de melhora com a sucessão das infestações. Estes resultados reforçam a necessidade de estudos comparativos sobre a resistência adquirida a carrapatos, envolvendo hospedeiros naturais e não naturais, como forma de colocar em evidência mecanismos de defesa que possam estar alterados ou ocultos em relações parasita-hospedeiro naturais.</p>