Tick Rhipicephalus Sanguineus Research Articles

Fipronil-induced cell death in salivary glands of Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) semi-engorged females

The tick Rhipicephalus sanguineus is currently considered an urban plague. For this reason many studies are intended to find methods to control these ectoparasites. Thus, the present study analyzed the ultrastructural modifications of the salivary glands cells of semi-engorged females of R. sanguineus resulting from their exposition to Fipronil (active ingredient of Frontline®). The studied individuals were divided into four groups. Group 1 was exposed to distilled water (control) and groups 2, 3 and 4 were exposed to 1, 5 and 10ppm of Fipronil, respectively. The salivary gland of ticks subjected to the acaricide showed accelerated process of cell death by atypical apoptosis, as well as augmented cell damages as the concentration of the chemical compound was increased. The acaricide toxicity at cellular level was demonstrated by remarkable changes of elements of the cytoskeleton and spherocrystals (extremely hard inorganic structures). However, tick defense mechanisms, such as the observed autofagic vacuoles proved the cells attempt to preserve their integrity and minimize the devastating action of this chemical compound on the salivary glands.

Rickettsial infections of dogs, horses and ticks in Juiz de Fora, southeastern Brazil, and isolation of Rickettsia rickettsii from Rhipicephalus sanguineus ticks

The present study was performed in an area endemic for Brazilian spotted fever (BSF) in Juiz de Fora, state of Minas Gerais, Brazil, during the years 2007 and 2008, when fatal cases of BSF (caused by Rickettsia rickettsii) were reported. Adult ticks (Acari: Ixodidae) identified as Rhipicephalus sanguineus (Latreille) and Amblyomma cajennense (Fabricius) were collected from dogs and horses, respectively, and tested by polymerase chain reaction (PCR). Overall, 13.1% of the Rh. sanguineus ticks and none of the A. cajennense were found to be infected with R. rickettsii. Two isolates of R. rickettsii were successfully established in Vero cell culture from two Rh. sanguineus ticks. An indirect immunofluorescence assay (IFA) using R. rickettsii antigens detected blood serological reaction to R. rickettsii in 67.9% (53/78) of dogs and 41.0% (16/39) of horses living in the study area. Larval offspring from two Rh. sanguineus engorged females, naturally infected by R. rickettsii, were reared to adult stage in the laboratory. All active stages (larvae, nymphs, adults) remained 100% infected by R. rickettsii, which was efficiently transmitted to naïve rabbits. Overall, the results of the present study indicate a potential risk for transmission of R. rickettsii to humans by Rh. sanguineus, an occurrence yet to be documented in Brazil.

Toxicity effect of the acaricide fipronil in semi-engorged females of the tick Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae): Preliminary determination of the minimum lethal concentration and LC50

Chemical acaricides, especially fipronil (active ingredient of Frontline®), are still the most effective method to control tick populations. In this study, the effectiveness of fipronil was assessed in semi-engorged females of the tick Rhipicephalus sanguineus. A protocol for an in vitro bioassay (AIT) was developed, and the LC50 (lethal concentration 50%) and 95% confidence interval were determined. Ticks were immersed in Petri dishes with different concentrations of fipronil or distilled water for 2min, dried, and placed in an incubator for 7days. Dead R. sanguineus females treated with the 14 concentrations of fipronil were counted daily. Mortality results were compared with the Probit analysis, and the LC50 and 95% confidence interval were calculated, g (95): LC50=9.647 (4.711 to 13.470). This study was aimed at developing a more appropriate and updated protocol for an in vitro bioassay (AIT – adult immersion test), and providing information on the toxic potential of fipronil (elimination of ectoparasites with lower concentrations) and sensitivity of ticks, especially R. sanguineus, a pest of great interest, due to its occurrence in urban environments.

Co-feeding as a route for transmission of Rickettsia conorii israelensis between Rhipicephalus sanguineus ticks

Rickettsia conorii is widely distributed in Europe, Asia, and Africa. The brown dog tick, Rhipicephalus sanguineus, is the recognized vector of R. conorii. In this study, we assessed the efficiency of R. conorii israelensis transmission between co-feeding Rh. sanguineus ticks. Infected Rh. sanguineus adults and uninfected nymphs were fed simultaneously upon either naïve dogs or a dog previously exposed to this agent. When ticks were placed upon naïve dogs, 92-100% of nymphs acquired the infection and 80-88% of infected engorged nymphs transmitted it transstadially. When ticks were placed upon a seropositive dog, only 8-28.5% of recipient nymphs became infected. Our results establish the first evidence for efficient natural transmission of R. conorii israelensis between co-feeding ticks upon both naïve and seropositive dogs. This route of transmission can ensure continuous circulation of R. conorii israelensis in tick vectors even in the absence of naïve reservoir hosts.

Experimental Infection ofRhipicephalus sanguineusTicks with the BacteriumRickettsia rickettsii, Using Experimentally Infected Dogs

We evaluated if Rickettsia rickettsii-experimentally infected dogs could serve as amplifier hosts for hipicephalus sanguineus ticks. In addition, we checked if Rh. sanguineus ticks that acquired Ri. rickettsii from dogs could transmit the bacterium to susceptible hosts (vector competence), and if these ticks could maintain the bacterium by transstadial and transovarial transmissions. Uninfected larvae, nymphs, and adults of Rh. sanguineus were allowed to feed upon three groups of dogs: groups 1 (G1) and 2 (G2) composed of Ri. rickettsii-infected dogs, infected intraperitoneally and via tick bites, respectively, and group 3 composed of uninfected dogs. After larval and nymphal feeding on rickettsemic dogs, 7.1-15.2% and 35.8-37.9% of the molted nymphs and adults, respectively, were shown by polymerase chain reaction (PCR) to be infected by Ri. rickettsii, confirming that both G1 and G2 dogs were efficient sources of rickettsial infection (amplifier host), resulting in transstadial transmission of the agent. These infected nymphs and adults successfully transmitted Ri. rickettsii to guinea pigs, confirming vector competence after acquisition of the infection from rickettsemic dogs. Transovarial transmission of Ri. rickettsii was observed in engorged females that had been infected as nymphs by feeding on both G1 and G2 dogs, but not in engorged females that acquired the infection during adult feeding on these same dogs. In the first case, filial infection rates were generally <50%. No tick exposed to G3 dogs was infected by rickettsiae in this study. No substantial mortality difference was observed between Ri. rickettsii-infected tick groups (G1 and G2) and uninfected tick group (G3). Our results indicate that dogs can be amplifier hosts of Ri. rickettsii for Rh. sanguineus, although only a minority of immature ticks (<45%) should become infected. It appears that Rh. sanguineus, in the absence of horizontal transmission, would not maintain Ri. rickettsii through successive generations, possibly because of low filial infection rates.

The dynamics of RNA participation in the vitellogenesis of Rhipicephalus sanguineus ticks Latreille 1806 (Acari:Ixodidae). I. Nucleoli or Cajal bodies?

To understand the morphological and histological aspects of internal systems of ticks has become important matter since these arthropods have an impact in the areas of the economy and public health. In this context, this study has provided morphological data on female germinative cells of Rhipicephalus sanguineus ticks, ectoparasites of dogs that maintain a close relationship with human on a daily basis. Oocytes of engorged females were analyzed, through the PAS reaction (detection of polysaccharides) counterstained by methyl green (detection of RNA) revealing information that allowed to infer for the first time the presence of Cajal bodies, in the germinal vesicles (nuclei) of developing oocytes, as well as showing how the RNA and the polysaccharides are involved in the dynamics of the vitellogenesis in this species.

Ticks (Acari: Ixodidae) on Dogs from Uberlândia, Minas Gerais, Brazil

Uberlândia in Minas Gerais State, southeastern Brazil, has 622 000 inhabitants and is located in the Cerrado biome, the South American savannah. The city dog population is estimated at 82 000 and identification of tick species and infestation prevalence on this host has not been determined. A major infectious disease of dogs in the city, canine ehrlichiosis, is transmitted by Rhipicephalus sanguineus ticks. At the same time, autochthonous leishmaniosis has been recently described in the city and a role for dog ticks in the disease transmission has been supposed in Brazil. In this work, we present general information on dog ticks in Uberlândia municipality and region. Dogs from 33 farms and 31 districts were examined for ticks from July 2007 to February 2009. On the whole, 413 dogs were examined, 311 (75.3%) from the city and 102 (24.6%) from rural area. Overall infestation rate of dogs from Uberlândia was 37.3% and the mean infestation intensity was 3.25 parasites per dog. In the urban area, 100 dogs (32.2%) had ticks whereas 54 dogs (52.9%) from rural areas were infested. Four tick species were found: Rhipicephalus sanguineus, Amblyomma cajennense, Amblyomma ovale and Boophilus microplus. In the city, only R. sanguineus and one A. cajennense was found on dogs and R. sanguineus and A. ovale were the main dog ticks in rural areas.

Effects of prolonged exposure to low temperature on eggs of the brown dog tick, Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae)

The widespread geographical distribution of the brown dog tick Rhipicephalus sanguineus (Acari: Ixodidae) is related to the cosmopolitan distribution of its primary host and to its adaptability to different environments, under variable climate conditions. Field studies have suggested that temperature is the most important factor driving the population dynamics of this tick species. In order to investigate the effects of prolonged exposure to low temperature on eggs of R. sanguineus, nine groups (II-X) of five egg batches each were maintained at 8+/-2 degrees C (70+/-10% RH, and scotophase) for 15, 30, 45, 60, 75, 90, 105, 120, and 135 days. One group (group I) was maintained in the incubator (26+/-1 degrees C, 70+/-10% RH, and scotophase) and used as control. The mean egg incubation period from group I was 11.6+/-0.5 days, with an egg hatch rate of 99.5+/-0.5%. Conversely, no egg hatched at 8 degrees C. Exposure to cold showed a strong positive correlation with egg incubation period (r=0.99) as well as a strong negative correlation with egg hatch rate (r=-0.95) and larval longevity (r=-0.99). Overall, the present results points out that R. sanguineus eggs are sensible to prolonged exposure to low temperature, which is definitely a major limiting factor for the establishment of populations of this tick in cold temperate regions.

Transovarial passage of Leishmania infantum kDNA in artificially infected Rhipicephalus sanguineus

Phlebotomine sand flies are the only proven biological vectors of Leishmania parasites. However, Rhipicephalus sanguineus ticks have long been suspected to transmit Leishmania infantum in studies carried out in laboratory and natural conditions. In the present study, 5 μl of L. infantum promastigotes (1 × 10 6 cells per ml) was injected into the hemocel through the coxa I of four engorged females (F1, F2, F3 and F4). Control ticks (F5 and F6) were injected with sterile phosphate-buffered saline (PBS) using the same procedure. Then, these females, their eggs, and the originated larvae were tested by real time polymerase chain reaction (real-time PCR) for the presence of L. infantum kinetoplast DNA (kDNA). Females and eggs were tested after the end of the oviposition period (about 5 weeks post-inoculation) whereas larvae were tested about 4 months after the inoculation of females. All artificially infected females were positive for L. infantum kDNA. In addition, two pools of eggs (one from F2 and other from F4) and four pools of larvae (one from each F1 and F4 and two from F2) were positive for L. infantum kDNA. These results showed, for the first time, the transovarial passage of L. infantum kDNA in R. sanguineus ticks, thus suggesting that the transovarial transmission of L. infantum protozoa in ticks is worth to be investigated.

Seroprevalence of equine piroplasms and host-related factors associated with infection in Greece

Serum samples were collected from a total of 544 equids that included 524 horses, 13 mules, and 7 ponies from various regions of mainland Greece and were examined by competitive-inhibition ELISA (cELISA) to evaluate the level of exposure of Greek equids to Theileria ( Babesia) equi and/or Babesia caballi, the causative agents of piroplasmosis. Association between seropositivity and host-related factors of species, gender, age, origin, activity and location were investigated. The overall seroprevalence was 11.6% (9.1–14.6%) with 95% confidence limit. The seroprevalence for T. equi and B. caballi was found to be 11% (8.6–14%) and 2.2% (1.2–3.9%), respectively. The animal-related factors significantly linked with seropositivity were the species, activities of farming, racing, recreation, and geographic location in Attica, Macedonia, Peloponnese and Thessaly region ( p < 0.05). The relative risks for the presence of T. equi, B. caballi and mixed infection in mules compared to horses was 8.39, 33.58 and 40.31, respectively. The infection level for T. equi, B. caballi and mixed infection were significantly higher in farm equids than in racing equids ( p < 0.05). Also, the rate of infection of T. equi was higher in farm equids than recreational equids ( p < 0.05). The relative risk of T. equi infection between farming equids and equids used only for recreation activity was 3.25–1, while the relative risk of B. caballi infection was 0.14–1 for racing animals relative to recreation animals. The region with the highest level of infection to both parasites was Thessaly (38.8% T. equi and 6.1% B. caballi), followed by Peloponnese (10.4% T. equi and 3.9% B. caballi), Attica region (8.3% T. equi and 0.6% B. caballi) and finally Macedonia the region with the lowest prevalence (6.6% T. equi and 4.4% B. caballi). A higher seroprevalence rate was found among local animals compared to imported equids, indicating that equine piroplasm infection is enzootic in Greece. T. equi seroprevalence was significantly different and higher among increasing age groups of equids, suggesting persistent infections or lower transmission levels whereby animals may need to be exposed longer before acquiring the infection. Competent tick vectors Rhipicephalus bursa and Rhipicephalus sanguineus for the transmission of equine piroplasmosis were recovered from horses and dogs, respectively.

Soroprevalência de anticorpos anti-Ehrlichia canis em cães de Cuiabá, Mato Grosso

Canine ehrlichiosis is a disease transmitted by ticks Rhipicephalus sanguineus and caused by Ehrlichia canis, obligatory intracellular bacteria. The present study examined the prevalence of anti-E. canis in 254 dogs from four administrative regions of Cuiabá, Mato Grosso, by indirect immunofluorescence assay. There was a prevalence of 42.5% (108/254) without significant difference between the studied regions. The variables age, breed, sex, habitat, access to rural and ticks were analyzed. The antibody titers ranged from 1:40 to 1:2,560. Only 32 (29.63%) seropositive dogs were infested with ticks, all R. sanguineus. The results confirm that do not have breed, sex or age predisposition to ehrlichiosis due E. canis, while the lowest occurrence of reactive dogs indoors probably related to low tick infestation, although no significant difference between dogs with or without infestation with the tick vector.

First report about canine infections with Candidatus Mycoplasma haematoparvum in Serbia

There are two species of haemotropic mycoplasmas that infect dogs which are known so far. These are Mycoplasma haemocanis and "Candidatus Mycoplasma haematoparvum". In the case of dogs, the clinical picture of these infections manifests itself in immunocompromised dogs, although the organisms are also present in immunocompetent dogs which do not show any signs of infection. The vector for these microorganisms is the tick Rhipicephalus sanguineus. The goal of this research was to confirm the presence of canine infections with haemotropic mycoplasmas in our geographic area, regarding the facts that the vector of canine haemotropic mycoplasmas, the Rhipicephalus sanguineus is widely spread in nature, and that the epidemic indications and the clinical signs of canine infections are also present. By means of light microscopic examination of stained peripheral canine blood smears, scanning electron microscopic examination of canine erythrocytes, as well as PCR and sequence analysis of the genome, the presence of canine infections with "Candidatus Mycoplasma haematoparvum" in our geographic area has been identified for the first time.

Biology and ecology of the brown dog tick, Rhipicephalus sanguineus

The brown dog tick (Rhipicephalus sanguineus) is the most widespread tick in the world and a well-recognized vector of many pathogens affecting dogs and occasionally humans. This tick can be found on dogs living in both urban and rural areas, being highly adapted to live within human dwellings and being active throughout the year not only in tropical and subtropical regions, but also in some temperate areas. Depending on factors such as climate and host availability, Rh. sanguineus can complete up to four generations per year. Recent studies have demonstrated that ticks exposed to high temperatures attach and feed on humans and rabbits more rapidly. This observation suggests that the risk of human parasitism by Rh. sanguineus could increase in areas experiencing warmer and/or longer summers, consequently increasing the risk of transmission of zoonotic agents (e.g., Rickettsia conorii and Rickettsia rickettsii). In the present article, some aspects of the biology and ecology of Rh. sanguineus ticks are discussed including the possible impact of current climate changes on populations of this tick around the world.

An acute severe ehrlichiosis in a dog experimentally infected with a new virulent strain of Ehrlichia canis

Canine monocytic ehrlichiosis (CME) is caused by Ehrlichia canis, an obligate intracellular bacterium with tropism for monocytes and macrophages. It is transmitted by the ticks Rhipicephalus sanguineus and Dermacentor variabilis. CME has been reported throughout the world, with a higher frequency in tropical and subtropical regions. The disease may be manifested by fever, depression, dyspnoea, anorexia, haemorrhages, oedema and weight loss accompanied with laboratory findings of thrombocytopenia, leukopenia, anaemia, and hypergammaglobulinaemia [1–5]. It has been reported that experimental infection of dogs with a cell culture-passaged type strain of E. canis Oklahoma induces mild clinical signs and mild pathological alterations in dogs [4]. Therefore, an acute severe experimental canine infection model is needed to study the pathological and immunological pathways induced by virulent E. canis. The purpose of the present study was to describe the experimental infection of a dog with a virulent strain of E. canis (New Mexico) by analysing haematological and pathological findings.

Prospective evaluation of rickettsioses in the Trakya (European) Region of Turkey in 2005

Several rickettsial diseases have been reported in the Mediterranean basin, including Mediterranean spotted fever, caused by Rickettsia conorii and transmitted by Rhipicephalus sanguineus ticks, tick-borne lymphadenopathy, caused by Rickettsia slovaca and transmitted by Dermacentor marginatus ticks, Rickettsia mongolitimonae infection, transmitted by Hyalomma spp. ticks, Rickettsia helvetica infection, transmitted by Ixodes ricinus ticks, and flea-borne spotted fever, caused by Rickettsia felis and transmitted by cat fleas (Ctenocephalides felis) [1]. Since 2003, prospective surveillance and serological and molecular diagnosis of rickettsioses in the Trakya Region of Turkey has been conducted by the Trakya University in Edirne and the Universite de la Mediterranee in Marseille [1,2]. In 2003 and 2004, 22 patients were diagnosed as spotted fever group (SFG) rickettsioses, using molecular diagnostic methods [1,2]. R. conorii was previously isolated from the skin biopsy specimens of three of ten patients, and was also demonstrated by PCR in skin biopsy specimens of nine of ten patients [1]. From May to September 2005, 24 patients with SFG rickettsioses were admitted into the Trakya University Hospital, a tertiary-care hospital in Edirne. In this prospective study, our aim was to isolate and identify the rickettsial strains from skin biopsy specimens and blood samples of these 24 patients diagnosed with spotted fever in the Trakya Region of Turkey in 2005. M A T E R I A L S A N D M E T H O D S

Rickettsial infection in hospitalised patients in central Tunisia: report of 119 cases

N. Kaabia, F. Bellazreg, W. Hachfi, M. Khalifa, N. Ghanouchi, F. Bahri and A. LetaiefInfectious Diseases Unit, Farhat Hached Hospital, Sousse, TunisiaINTRODUCTIONRickettsial infections are widely distributedthroughout the world [1]. In Tunisia, Mediterra-nean spotted fever (MSF) is the most commonrickettsiosis and is a frequent cause of hospitali-sation [2]. However, other rickettsial infectionshave been reported [3]. The aim of this study wasto determine the different aetiologic agents andtheir epidemiological, clinical, laboratory andtherapeutic characteristics in patients with rick-ettsial infections.METHODS

Molecular and clinical evidence ofEhrlichiachaffeensisinfection in Cameroonian patients with undifferentiated febrile illness

In the U.S.A., human monocytotropic ehrlichiosis (HME) caused by Ehrlichia chaffeensis is an emerging tick-transmitted zoonosis. In Cameroon, where E. canis, E. chaffeensis and E. ewingii have recently been detected in dogs and/or ticks (Rhipicephalus sanguineus), the potential exists for human infections. Patients from the coastal region of Cameroon who had acute fevers of unknown aetiology were therefore checked for ehrlichial infection, using a real-time PCR that amplifies part of a genus-specific gene (dsb) that codes for a disulphide-bond formation protein. Ehrlichial blood was detected in the peripheral blood from 12 (10%) of the 118 patients investigated by PCR. When the 12 amplicons from the positive cases were sequenced, they were found to be identical to each other and to the corresponding dsb sequence of an Arkansas strain of E. chaffeensis. The 12 patients who were PCR-positive for E. chaffeensis suffered from fever (100%), headache (67%), myalgia (42%), arthralgia (58%), pulmonary involvement (17%) and/or a diffuse rash (17%).

Experimental infection of Rhipicephalus sanguineus with Rickettsia conorii conorii

Little is known about the relationships between Rickettsia conorii conorii, the agent of Mediterranean spotted fever (MSF), and its main vector, the brown dog tick Rhipicephalus sanguineus [1]. Matsumoto et al. recently reported a high mortality of Rh. sanguineus group ticks infected with R. conorii conorii by several methods including the use of a bacteraemic rabbit [2]. It had been speculated that reasons for this reduction in fitness might include the geographic origin of the ticks, which came from Thailand where R. conorii conorii has not been reported, or was associated with the pathogen load acquired during laboratory experiments. Here we present complementary experiments to test these hypotheses.

Mediterranean spotted fever in Algerian children

Mediterranean spotted fever (MSF) is a potentially life-threatening zoonosis caused by Rickettsia conorii and transmitted by the brown dog tick Rhipicephalus sanguineus [1]. Although MSF is one of the oldest recognised rickettsioses, there have been few reports about this rickettsiosis in North Africa [1,2]. The present work on MSF cases occurring in children is a subset of a larger study conducted within all age categories.

Spotted fever group rickettsioses documented in Morocco

Mediterranean spotted fever (MSF) is caused by Rickettsia conorii conorii transmitted by the brown dog tick Rhipicephalus sanguineus. It is endemic in the Mediterranean area, where most of the cases are encountered during the summer, when the tick vectors are highly active [1]. In Morocco, MSF has been the sole human tick-borne rickettsiosis known by clinicians, and cases that are clinically recognized are rarely documented [2]. Our aim is to describe the clinical and epidemiological characteristics of confirmed cases of MSF in Casablanca and in the surrounding regions of Morocco.