Clarification of the Rhipicephalus sanguineus group (Acari,Ixodoidea, Ixodidae). I. R. sulcatus Neumann, 1908 and R. turanicus Pomerantsev, 1936

For many years the biosystematic status of several species in the Rhipicephalus sanguineus group has been confused, with the result that they have often been misidentified. Over the years some 18 of these species have been synonymised with R. sanguineus (Latreille, 1806) itself. More recently four new species in the group have been described: R. guilhoni Morel & Vassiliades, 1963; R. moucheti Morel, 1964; R. bergeoni Morel & Balis, 1976; and R. camicasi Morel, Mouchet & Rodhain, 1976.The literature on this group is critically reviewed and the main systematic problems analysed. R. sulcatus Neumann, 1908 and R. turanicus Pomerantsev, 1936 are two species that were confused both morphologically and ecologically. This has resulted in erroneous conclusions regarding their host relationships and distributions. Integrated biological, morphological and ecological studies on these two species have been conducted. Cross-breeding experiments have proved that both are distinct taxonomic entities. Interbreedings between African and Cypriot strains of R. turanicus demonstrated marked heterosis.A scanning electron microscope was used to determine the main diagnostic morphological differences between the larvae, nymphae and adults of R. sulcatus and R. turanicus, and the morphological similarities between African and Cypriot strains of R. turanicus. Rhipicephalus sulcatus occurs widely in the Afrotropical region in wetter ecological habitats and most frequently parasitises hares, dogs and jackals. R. turanicus occurs more-or-less throughout the Afrotropical region in a wide range of climatic biotopes, as well as in parts of southern Europe, Arabia and Asia, and is most abundant in the late rainy/early dry seasons. It occurs on a wide range of domesticated and wildlife hosts, including ground-feeding birds.     

Experimental evaluation of birds as disseminators of the cosmopolitan tick Rhipicephalus sanguineus (Acari: Ixodidae)

Rhipicephalus sanguineus is believed to be the most widespread tick species of the world and its dissemination seems to rely on the diffusion of its main host, the dog. Empirical observations indicate that several bird species in urban areas regularly steal dog food. Such circumstances create a chance for R. sanguineus ticks to climb on birds and carry ticks to another site. In this work we evaluated experimentally the likelihood of birds (chicks) to either feed and/or carry R. sanguineus ticks from an infested site to another and to infest a host (rabbit) in the new location. Chicks were not suitable hosts for R. sanguineus ticks. Not a single adult tick engorged on chicks, yield as well as weight of engorged larvae and nymphs were very low and feeding period of these ticks was very long. However, a few larvae and, chiefly, nymphs were delivered to a new location either mechanically or after attachment and engorging total or partially on chicks. A few of these ticks fed successfully on rabbits. Further evidence on the capacity of birds to introduce R. sanguineus into non-infested dog settings should be provided by systematic examination of birds from urban areas, close to tick infested households.     

Clarification of the Rhipicephalus sanguineus group (Acari,Ixodoidea, Ixodidae). II. R. sanguineus (Latreille, 1806) and related species

In this, our second study on the biosystematics of the Rhipicephalus sanguineus group, we consider an additional five species found in the Afrotropical region, namely R. sanguineus, R. camicasi, R. guilhoni, R. moucheti and R. bergeoni.Cross-breeding experiments have shown that R. sanguineus (Latreille, 1806) sensu stricto is genetically distinct from R. camicasi Morel, Mouchet & Rodhain, 1976. Further cross-breeding trials confirmed that R. camicasi also occurs in Saudi Arabia: a field strain from this country was more productive than a laboratory-reared strain from Egypt. R. sanguineus, which parasitises mainly dogs, probably occurs throughout the Afrotropical region. R. camicasi parasitises both large and small domestic ruminants and is restricted to the arid and semi-arid lowlands of northeastern Africa and the Arabian peninsula. The larva, nymph, male and female of these two last named species are described with the aid of scanning electron micrographs (SEMs).The two western African species, R. guilhoni Morel & Vassiliades, 1963 and R. moucheti Morel, 1964, are accepted as valid members of the R. sanguineus group, but we have little material available for critical study. The male and female of R. guilhoni are briefly redescribed with the aid of SEMs. R. bergeoni Morel & Balis, 1976 occurs predominantly on cattle in the wetter highlands and subhighlands of Ethiopia and Sudan. The male and female are briefly described. Current morphological and ecological data suggest that the inclusion of this species in the R. sanguineus group is questionable.     

Off‐host aggregation in the non‐fed,female brown dog tick,Rhipicephalus sanguineus (Latreille), is induced by tick excreta and enhanced by low relative humidity

We report that Rhipicephalus sanguineus (Ixodida: Ixodidae) faeces and its main component, guanine, act as assembly pheromones in short‐range Petri plate bioassays. Arrestment activity in response to guanine was lower than that in response to natural excreta, indicating the presence of other active ingredients in natural excreta. The selective removal of appendages was used to establish the important roles played by the palps and the front pair of legs in the detection of the pheromone. Reaction to chemically pure guanine at varying concentrations occurred without a dose response; thus only the presence of guanine, not a critical amount, is required to induce assembly. Higher speed and intensity of clustering occurred at 33% relative humidity (RH). We conclude that female adults of R. sanguineus are more prone to assemble under dry conditions that match the arid microhabitats preferred by this species and that this tendency allows this tick to reside in human dwellings and dog kennels that maintain standards of comfort at 30–50% RH. Cleaning or removing tick excreta‐covered surfaces on which ticks aggregate from within and around human dwellings may prove useful as a means of interfering with the establishment of off‐host clusters of R. sanguineus.     

Synergism of thymol,carvacrol and eugenol in larvae of the cattle tick,Rhipicephalus microplus,and brown dog tick,Rhipicephalus sanguineus

The effects of combinations of the monoterpenes thymol and carvacrol and the phenylpropanoid eugenol in larvae of Rhipicephalus microplus (Canestrini, 1888) (Acari: Ixodidae) and Rhipicephalus sanguineus sensu lato (s.l.) (Acari: Ixodidae) were assessed by the larval packet test. The CompuSyn program was used to make qualitative assessments of the effects (synergistic, additive and antagonistic) of the associations. The effects of all combinations tested against R. microplus larvae were synergistic, with combination indices (CIs) <0.70. When tested against R. sanguineus, eight of the mixtures showed a synergistic effect (CI < 0.70); only the carvacrol + thymol mixture at LC₅₀ presented a moderate synergistic effect, with CIs between 0.70–0.90. This study is the first to determine the effects of the interactions of these substances in the control of these two tick species. The combinations of carvacrol + thymol, carvacrol + eugenol and thymol + eugenol have synergistic effects in R. microplus and R. sanguineus s.l. larvae.     

Hyalomma aegyptium as dominant tick in tortoises of the genus Testudo in Balkan countries, with notes on its host preferences

Collection of 1327 ticks sampled throughout Greece, Bulgaria, Romania and Croatia, from 211 tortoises belonging to three species, Testudo marginata Schoepff, T. graeca Linnaeus, and T. hermanni Gmelin, revealed the presence of four species of ixodid ticks, namely Hyalomma aegyptium (Linnaeus), Haemaphysalis sulcata Canestrini and Fanzago, H. inermis Birula and Rhipicephalus sanguineus (Latreille). Study confirmed the strong dominance of all life stages of H. aegyptium among ticks parasitizing west Palaearctic tortoises of genus Testudo Linnaeus. Furthermore, a considerable portion of ticks collected from tortoises in southwestern Bulgaria represent larvae and nymphs of H. sulcata. At the same area we collected as exception one larva and one nymph of H. inermis from a single specimen of T. hermanni. Our findings of four adults of R. sanguineus is the first record of this species from reptilian host. According to our results achieved on localities with syntopic occurrence of two tortoise species, T. marginata and T. graeca represent in the Balkans the principal hosts of H. aegyptium, whereas T. hermanni serves only as an alternative host in the areas close to range of either T. marginata or T. graeca.     

Ticks Infesting Livestock on Farms in Western Sicily, Italy

The results of a 2-year survey on ticks infesting livestock on farms in Western Sicily, Italy, are reported. Several dogs living in the same area were also examined for ticks. Moreover, free-living ticks from one cattle farm were caught by CO₂ traps and flagging. A total of 6208 specimens was collected belonging to 9 species: Rhipicephalus bursa (32.4%), Rhipicephalus turanicus (22.7%), Rhipicephalus sanguineus (19.3%), Hyalomma lusitanicum (12.0%), Haemaphysalis punctata (7.8%), Hyalomma marginatum (3.5%), Dermacentor marginatus (1.4%), Ixodes ricinus (0.8%) and Ixodes hexagonus (0.1%). The species belonging to the genus Rhipicephalus were present on all hosts and habitats monitored, R. bursa was found to be abundant on cattle (46.3%) and sheep (62.0%), R. sanguineus was prevalent on dogs (50.4%), and R. turanicus on donkeys (41.0%) and as free-living species (48.5%).     

Incongruent effects of two isolates of <Emphasis Type="Italic">Rickettsia conorii</Emphasis> on the survival of <Emphasis Type="Italic">Rhipicephalus sanguineus</Emphasis> ticks

Rickettsia conorii, the etiologic agent of Mediterranean spotted fever is widely distributed in Southern Europe, the Middle East, Africa, India and the Caspian region. In the Mediterranean region, the brown dog tick, Rhipicephalus sanguineus, is the recognized vector of R. conorii. To study tick-pathogen relationships and pathogenesis of infection caused in model animals by the bite of an infected tick, we attempted to establish a laboratory colony of Rh. sanguineus persistently infected with R. conorii. Rhipicephalus sanguineus ticks of North American and Mediterranean origin were exposed to R. conorii isolates of African (R. conorii conorii strain Malish) and Mediterranean (R. conorii israelensis strain ISTT) origin. Feeding of ticks upon infected mice and dogs, intra-hemocoel inoculation, and submersion in suspensions of purified rickettsiae were used to introduce the pathogen into uninfected ticks. Feeding success, molting success and the longevity of molted ticks were measured to assess the effects of R. conorii on the survival of Rh. sanguineus. In concordance with previously published results, Rh. sanguineus larvae and nymphs from both North American and Mediterranean colonies exposed to R. conorii conorii Malish experienced high mortality during feeding and molting or immediately after. The prevalence of infection in surviving ticks did not exceed 5%. On the other hand, exposure to ISTT strain had lesser effect on tick survival and resulted in 35–66% prevalence of infection. Rh. sanguineus of Mediterranean origin were more susceptible to infection with either strain of R. conorii than those from North America. Previous experimental studies had demonstrated transovarial and transstadial transmission of R. conorii in Rh. sanguineus; however, our data suggest that different strains of R. conorii may employ different means of maintenance in nature. The vertebrate host may be a more important reservoir than previously thought, or co-feeding transmission between different generations of ticks may obviate or lessen the requirement for transovarial maintenance of R. conorii.     

Seasonal dynamics of the brown dog tick,Rhipicephalus sanguineus,on a confined dog population in Italy

This study evaluated the seasonal dynamics of Rhipicephalus sanguineus (Latreille) (Acari: Ixodidae) on naturally infested dogs in a private shelter in southern Italy. From March to May 2008, 39 autochthonous mixed‐breed young dogs and 10 beagles were enrolled in the study. From March 2008 until March 2009, every 21 ± 2 days, 11 body sites of each dog were checked for ticks. At each follow‐up, the number of ticks, their developmental stage, sex and location on the dog's body were recorded. Adult ticks were found throughout the year, but immatures were absent in January and February. The adult tick population increased from July to August, whereas the load of immatures increased in early July and peaked in September, which suggests that R. sanguineus develops one generation per year in this area. The mean number of immature ticks per infested dog was higher than that of adults from March to October 2008. Ears, interdigital areas and armpits were the most frequent attachment sites of adult ticks. At the last follow‐up, a total of 2266 ticks were collected and identified as R. sanguineus. The results suggest that R. sanguineus develops one generation per year in the study area, but that it infests dogs in all seasons. This information should be taken into account when planning control programmes against this tick species and the pathogens it transmits.     

First genetic characterization of the brown dog tick <Emphasis Type="Italic">Rhipicephalus sanguineus</Emphasis> sensu lato in Peninsular Malaysia

The brown dog tick Rhipicephalus sanguineus sensu lato (s.l.) is a species complex comprising three main mitochondrial lineages, namely tropical, temperate and southeast European lineages. Despite its medical and veterinary importance, little attention has been paid to the genetic lineage of this species in Southeast Asia. Rhipicephalus sanguineus s.l. from Malaysia was investigated genetically, for the first time, using the mitochondria-encoded cytochrome c oxidase subunit I (COI) and 16S ribosomal RNA (16S) genes. Specifically, a pair of primers was developed to amplify the COI sequences in the present study. Both genes unambiguously assigned Malaysian material into the tropical lineage of R. sanguineus s.l. The 16S sequences were highly conserved; no variation site was observed. The COI sequences revealed slightly higher variation by recovering four haplotypes, one of which is restricted to the northernmost of Peninsular Malaysia. This finding will be a stepping stone in promoting more biological studies of this species complex in this region.     

The Effect of Male Ticks on the Feeding Performance of Immature Stages of Rhipicephalus Sanguineus and Amblyomma Americanum (Acari: Ixodidae)

A unique group of immunoglobulin-binding proteins (IGBPs), produced by ixodid male ticks during the latter half of their prolonged feeding period, improves the feeding performance of co-feeding females. As a follow-up to this observation, we investigated whether male tick feeding also affects the feeding of other developmental stages. Immature stages of Rhipicephalus sanguineus (Latreeille) and Amblyomma americanum (L.) were fed on rabbits in the presence or absence of conspecific males. The mean weight of larvae and nymphs of both species that fed around males and detached from the host on the first day of dropping was significantly higher than when the immature ticks fed on rabbits in the absence of males. However, larvae of both species and nymphs of R. sanguineus that fed slower and detached on the second day of dropping did not show significant differences in weight. A similar pattern was observed for A. americanum nymphs although, unlike R. sanguineus, the presence of males also influenced the feeding performance of the nymphs that fed slowly and detached on the second day of drop-off. The improved feeding performance demonstrated by immature ticks in the presence of males may be due to immunomodulatory saliva proteins, such as immunoglobulin-binding proteins (IGBPs) that are introduced into the co-feeding site. The results are considered in relation to the distribution of ixodid tick species on their natural hosts.     

Morphophysiological analysis of the salivary glands of Rhipicephalus sanguineus sensu lato (Acari: Ixodidae) exposed to ozonated water: A control strategy

The tick Rhipicephalus sanguineus sensu lato has great medical and veterinary importance, mainly because the ability to transmit many diseases, causing harm to pets but also risks to public health. The blood spoliation and transmission of pathogens occur because of the immunosuppressive action of these ticks' saliva, a potent mixture of bioactive substances that is secreted by the salivary glands, one of the organs responsible for their biological success, and hence the target of studies for their control. Ozone has promise for use as an alternative acaricide, due to its proven efficiency in controlling agricultural and food pests, besides posing no risk of environmental contamination or to animal and human health. Therefore, this study evaluated the acaricidal potential of exposure of females of R. sanguineus s.l. to ozonated water at many concentrations and analysed the morphophysiological alterations of the salivary glands, employing histological and light microscopic techniques. The results demonstrated that the ozonated water at the concentrations investigated caused severe alterations in the salivary glands, bringing a new perspective for control of R. sanguineus s.l., through an ecologically correct method due to the absence of harm to non‐target organisms and the environment.     

Molecular dissimilarities of <Emphasis Type="Italic">Rhipicephalus sanguineus</Emphasis> (Acari: Ixodidae) in Brazil and its relation with samples throughout the world: is there a geographical pattern?

In this study the genetic variability of Rhipicephalus sanguineus within Brazil and its relation with ticks of the same group from different continents was evaluated. Mitochondrial 12S and 16S rDNA fragments of R. sanguineus from seven Brazilian States were sequenced and compared to GenBank sequences of R. sanguineus and R. turanicus ticks from Africa, Asia, Europe, South America and USA. Results indicate a relatively high intra-specific variability between Brazilian samples but also a global latitude linked distribution pattern of at least two major R. sanguineus groups; one group distributed from latitude 25°N to 22°S including R. sanguineus from Brazil, Taiwan and Thailand and R. turanicus from Zambia and Zimbabwe, and the other group found closer to the poles, roughly above 29°N and below 30°S with ticks from Argentina, Uruguay, France, Oklahoma (USA), Israel and Egypt.     

The Susceptibility of Different Species and Stages of Ticks to Entomopathogenic Fungi

Boophilus annulatus, Hyalomma excavatum and Rhipicephalus sanguineus ticks were shown to be susceptible to different entomopathogenic fungi under laboratory conditions. Comparative results of bioassays using five different fungal species showed that some strains of Metarhizium anisopliae are highly pathogenic against various tick stages tested. In contrast to their activity against insects, fungi also affected tick eggs. All tested tick stages including those feeding on a host were found to be susceptible to these fungi, except for adult H. excavatum ticks, which were relatively resistant. This revised version was published online in July 2006 with corrections to the Cover Date.     

<Emphasis Type="Italic">Rhipicephalus sanguineus</Emphasis> on dogs: relationships between attachment sites and tick developmental stages

The brown dog tick, Rhipicephalus sanguineus, is the most widespread tick in the world and infests primarily domestic dogs. Studies on the bio-ecology of R. sanguineus have been carried out worldwide, but little is known of the on-dog relationships of tick developmental stages and their possible role on tick feeding performance, reproduction and pathogen transmission. We studied the relationships between different developmental stages of R. sanguineus on particular body areas of naturally infested dogs. In addition, we assessed whether these relationships could vary according to sex and breed of the dogs. Over 2,200 tick records were analyzed and the results showed that attachment sites of males and females are strongly positively correlated whereas attachment sites of nymphs and adults tend to be negatively correlated. Our findings indicate that adult ticks generally feed on sites (e.g., ears) that make it difficult for dogs to remove them, whereas immatures feed on lower areas of the dog’s body (e.g., belly, rump, and hind legs), probably because of their more limited mobility. Further research on the possible on-dog interactions of adult and immature ticks is needed to better understand why their attachment sites tend to be negatively correlated and to assess their possible implications for pathogen transmission.     

Ticks (Acari:Ixodidae) of the Blue and White Nile ecosystems in the Sudan with particular reference to theRhipicephalus sanguineus group

Twenty-four adult ixodid tick species, infesting livestock and some wildlife hosts along the Blue and White Nile in the Sudan, were identified. Three species,Boophilus geigyi, Rhipicephalus camicasi andR. bergeoni, were recorded for the first time from the Sudan. Tick numbers on indigenous breeds of cattle (Bos indicus) were relatively low, ranging between 17.1 and 40.5 per animal. Young cattle grazing with the herd carried significantly fewer ticks than older animals. With the exception ofB. annulatus andR. simus, which have extended their distribution further north into Blue Nile, Gezira and Khartoum Provinces, the distribution patterns of the most important cattle ticks have been relatively unchanged over the past 30 years.TheRhicicephalus sanguineus group was represented by six species.R. camicasi was the only species present on cattle, sheep and goats in the north in Kassala and Khartoum Provinces, whereas this species occurred sympatrically withR. guilhoni andR. turanicus further south in Gezira and Blue Nile Provinces. In the Southern Region of the Sudan onlyR. turanicus andR. guilhoni were present, the latter being by far the predominant species, with peak activity towards the end of the rains in the Jonglei Canal Area.R. bergeoni was collected once, from cattle near the Ethiopian border in Blue Nile Province, whereasR. sanguineus sensu stricto was collected throughout the study area, from domestic dogs only. Finally,R. sulcatus was found once on a hare.The distributions of the common tick species are correlated with the occurrence of tick-borne diseases of domestic animals and recommendations for the control of tick-borne diseases and their vectors in the Sudan are given.     

Mitochondrial DNA analysis of Rhipicephalus sanguineus s.l. from the western Iberian peninsula

Rhipicephalus sanguineus Latreille (1806) (Ixodida: Ixodidae) is considered to be the most widely distributed tick and to have a vast range of habitats and hosts, including livestock, pets and wildlife. In addition to morphological differences, recent investigations using approaches based on molecular genetic markers have revealed the existence of different R. sanguineus lineages in different geographic regions. In this study, 475 ticks collected from dogs in the western Iberian peninsula were studied both morphologically and genetically, using 12S and 16S rDNA and COI gene markers in order to clarify the controversy over the systematic status of R. sanguineus sensu lato in Western Europe, and to compare the present data with those sourced from studies conducted in other regions of the world. Despite the high morphometric variability, particularly on spiracles in both genders and in female genitalia, data obtained with different genetic molecular markers show very low variability, suggesting the existence of a unique species. In addition, the phylogenetic analysis showed genetic uniformity, supporting the existence of a well‐defined clade consisting of R. sanguineus s.l. specimens from Western Europe that are distinct from R. sanguineus s.l. from Africa. Furthermore, these data corroborate the existence of a polymorphic species in Western Europe, which requires to be consensually redescribed in view of its medical and veterinary importance in pathogen transmission.     

Ticks (Acari: Ixodidae) associated with domestic dogs in Franca region,São Paulo,Brazil

Ticks on 140 domestic dogs from both urban and rural areas of Franca region in São Paulo state were identified with 102 dogs from urban areas and 38 from rural areas. Of urban dogs, 27.5% were infested exclusively by Rhipicephalus sanguineus ticks. Of the rural dogs, 36.8% were infested with the following tick species: R. sanguineus, Boophilus microplus, Amblyomma ovale and A. cajennense. Mixed infestations included a dog hosting A. cajennense and A. ovale and another with B. microplus and R. sanguineus. The most intense infestations were detected on urban dogs. Hemolymph tests of these ticks performed to detect rickettsial or Borrelia bacteria yielded negative results.     

Potential of the insect growth regulator, fluazuron, in the control of Rhipicephalus sanguineus nymphs (Latreille, 1806) (Acari: Ixodidae): determination of the LD95 and LD50

Conventional pesticides have suffered two main drawbacks: (a) broad spectrum of action and (b) selection of target species resistant to the different active ingredients. Thus compounds that are less harmful to the environment and to human health, more specific and that do not induce resistance need to be developed. One alternative are insect growth regulators, such as fluazuron. The present study examined the efficacy of fluazuron (active ingredient of the acaricide Acatak®) and the sensitivity of Rhipicephalus sanguineus nymphs exposed to different doses of this chemical, and determined the lethal doses of fluazuron: 95% – LD₉₅ and 50% – LD₅₀. Different doses of fluazuron were applied in duplicates on the dorsal region of hosts (“pour on”). Distilled water was used in the control group. On the first day after the treatment with fluazuron, hosts were artificially infested with R. sanguineus nymphs. After engorgement, nymphs were removed, placed on Petri dishes, identified, and maintained in BOD incubator for 15 days. Dead R. sanguineus nymphs after the treatment with 13 different doses of fluazuron were quantified and the LD₉₅ was estimated to be 100 mg/kg and LD₅₀, 19.544 mg/kg (12.478–22.636), with a confidence interval of 95%. Nymphs of R. sanguineus were sensitive to fluazuron at various levels, indicating that this insect growth regulator (IGR) may be used to control this parasite in this stage of its biological cycle, reducing the significant damage it causes.     

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.