Inheritance of weight in Rhipicephalus appendiculatus ticks (Acari: Ixodidae) in the laboratory

A selection of the 10% lightest and 10% heaviest males and females of a population of individually weighed Rhipicephalus appendiculatus Neumann adults was made in two experiments. The offspring of homologous pairs were followed until the next adult stage (light x light, control x control and heavy x heavy). The engorged nymphal weights, unfed adult weights, engorged female weights of the parents, egg mass weights, egg weights, larval scutal lengths, engorged larval weights, unfed nymphal weights, engorged nymphal weights and adult weights of the progeny were determined. No significant differences could be demonstrated between the two lines for egg weight, larval scutal length, engorged larval weight and unfed nymphal weight. Significant differences were found between the egg masses, engorged nymphal weights and adult weights of the two lines. The heritability coefficients of body weight determined from adult to adult were 0.14 and 0.10, respectively, during the first and second experiments. Considering females and males separately, the coefficients were 0.10 and 0.18 during the frist experiment and 0.12 and 0.09 during the repeat experiment respectively.     

Underwater survival of Rhipicephalus sanguineus (Acari: Ixodidae)

Rhipicephalus sanguineus (Acari: Ixodidae) is a worldwide distributed tick, also due to its adaptability to different environmental conditions. In order to assess its ability to survive and to lay eggs after water immersion, 150 engorged females from southern Italy were water immersed for 1-15 days whereas eggs were flooded for 1-5 days. All females survived water immersion for 48 h, some of them up to 72 h, but egg hatch rate was negatively correlated with female submersion period. All eggs flooded for up to 120 h hatched successfully. These findings suggest that R. sanguineus is able to survive underwater for some days without loosing any biological activity. This feature should be considered in relation to its potential to spread to new areas and to its role as a vector of pathogens also in consideration of changes in climate the Earth is currently experiencing.     

Ecdysteroid levels changed by permethrin action in female Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) ticks

As recent studies have shown that ecdysteroids may play a major role in the regulation of vitellogenesis in Ixodidae, the present study quantified, by means of a radioimmunoassay, the levels of ecdysteroids present in the hemolymph of semi-engorged females of Rhipicephalus sanguineus ticks obtained from control females (exposed to distilled water) and those exposed to increasing concentrations of permethrin. The levels of ecdysteroids decreased significantly as the concentration of permethrin increased, suggesting that this compound could be an inhibitor of ecdysteroids secretion, and consequently interfering with the reproductive ability of these ticks, since this hormone is responsible for the synthesis and incorporation of vitellogenin by oocytes. This study complements the previous results with R. sanguineus semi-engorged females, showing that permethrin is a potent agent causing major morphological changes in tick oocytes, such as the appearance of large vacuoles in the cytoplasm, reduction in the amount of yolk granules and a decrease in oocyte size, thus culminating in cell death and consequently reducing or preventing reproduction in treated females. The findings that permethrin leads to a decrease in ecdysteroid titers could represent an entry step into this scenario.     

Hard ticks (Acari,Ixodidae) of Croatia

The present paper is based on original and literature data. In Croatia the first studies on the occurrence of ixodid species were made about 80 years ago. The number of tick species recorded in Croatia considerably increased during the 1950s, 60s, 70s and 80s of the past century. A total of 21 species of hard tick belonging to 5 genera have been recorded in Croatia. Ixodes is the best represented genus, with seven species recorded. Haemaphysalis is represented by six species, followed by Rhipicephalus with four species. Dermacentor and Hyalomma are represented by two species each. The ticks were collected on 47 different host species. Eleven tick species were collected on Bos taurus and Ovis aries, followed by Capra hircus and Equus caballus with 8 species and Canis lupus familiaris with 6 species. On the remaining 42 host species one, two or three tick species were collected. The most widespread tick is Ixodes ricinus which was found on 25 different host species.     

Questing behaviour of Ixodes ricinus ticks (Acari: Ixodidae)

The vertical distribution in the vegetation of questing Ixodes ricinus ticks was investigated in two different vegetation types (high and low vegetation) at two localities in south-central Sweden during 1992-1993 (Toro) and 1995 (Bogesund). Significant correlations were found between the vertical distribution of immature ticks and the height of the vegetation. The greatest mean availabilities of the larvae and nymphs in low vegetation were in the intervals 0-9 and 30-39 cm, respectively. The larval numbers were greatest close to the ground (0-29 cm) in both high and low vegetation. The larval : nymphal ratio, at ground level at localities free of ground vegetation, varied between 8 : 1 and 32 : 1. In high vegetation, the greatest mean numbers of nymphal and adult ticks were at height intervals of 50-59 and 60-79 cm, respectively. These ranges are within the estimated height interval (40-100 cm) of the main part of the body surface of their preferred host, the roe deer (Capreolus capreolus). The presence of most questing I. ricinus larvae at ground level would favour the transmission of Borrelia burgdorferi s.l., since this is where the highly reservoir-competent rodents and shrews usually occur.     

Gynandromorphism in Amblyomma cajennense and Rhipicephalus sanguineus (Acari: Ixodidae)

During a survey of ticks on horses in November 2000, at the University of S?o Paulo farm in Pirassununga county, S?o Paulo, Brazil, 1 gynandromorph of Amblyomma cajennense was collected from a naturally infested horse. In another survey on dogs in March 2001, in the urban area of Monte Negro, Rond?nia, Brazil, a gynandromorph of Rhipicephalus sanguineus was collected from a naturally infested dog. Both specimens are described and classified as perfect bipartite protogynanders.     

Rhipicephalus appendiculatus (Acari: Ixodidae): dynamics of Thogoto virus infection in female ticks during feeding on guinea pigs

Engorged nymphs (Rhipicephalus appendiculatus) were inoculated parenterally with Thogoto (THO) virus (approximately 1 microl per nymph; 10(6)-10(7) PFU/ml). The adult females which resulted were used as the source of infected ticks for this study. Hemolymph, salivary glands, synganglion, gut, ovary, and Malpighian tubules were collected on each day of the blood meal and titrated for THO virus by plaque assay. The percent of tissues infected with virus was 16% or less on the day of attachment. Percent infection rose for all tissues throughout 6-7 days of feeding, reaching 40-100% infection during the rapid phase of engorgement. For the first 4 days of feeding, virus titer in the synganglion was higher than in salivary glands (means of 6.4-34.7 PFU/synganglion and 1.6-8.8 PFU/salivary gland pair). From days 5-7, virus titer was generally higher in the salivary gland than the synganglion (means of 422, 408, and 817 PFU/gland pair and means of 62, 811, and 9 PFU/synganglion). However, because a salivary gland pair is much heavier than a synganglion, the virus concentration in the synganglion was much higher than in the salivary gland during the slow phase of feeding. During the rapid phase of feeding, the difference in virus titer between the synganglion and salivary gland reduced. This difference between the early and late stages of feeding may explain why a previous study [J. Gen. Virol. 70 (1989) 1093], using immunofluorescence and immuno-gold labelling, failed to detect virus in the salivary gland early in feeding. These data provide evidence to explain that R. appendiculatus can transmit THO virus within 24h of attachment, an important epidemiological finding.     

Host-seeking behaviour by Australian ticks (Acari: Ixodidae) with differing host specificities

Ticks generally detach from their hosts into sites where they are later exposed to host species which may or may not be suitable for infestation. The question of how four species of ixodid ticks, with differing specificities, behave towards such potential host species was examined. Observations of the generalists,Aponomma hydrosauri andAmblyomma limbatum and the specialists,Aponomma fimbriatum andAponomma concolor, showed that the generalists were attracted to a wider range of potential host species than the specialists and that the larval stages of all tick species, regardless of specificity, contacted more potential host species than the adults. The interspecific differences may be attributed to reliance on different sets of host cues, while the intraspecific differences may reflect the developmental state of the sensory system.     

First detection and genetic identification of Rickettsia infection in Rhipicephalus sanguineus (Acari: Ixodidae) ticks collected from Southern Taiwan

Experimental and Applied Acarology - The prevalence and genetic identity of Rickettsia infection in Rhipicephalus sanguineus sensu lato (s.l.) ticks were determined in Taiwan. In total 1153 ticks...     

Displacement of Rhipicephalus decoloratus by Rhipicephalus microplus (Acari: Ixodidae) in the Eastern Cape Province, South Africa

The objective of the study was to establish to what extent the native tick species Rhipicephalus decoloratus has been displaced by the invasive introduced tick, Rhipicephalus microplus at two communally grazed areas in the Eastern Cape Province, South Africa. To this end ticks were collected monthly from five cattle over a period of 2 years and from 10 drag-samples of the vegetation over a period of 1 year at each locality. Whereas 10 years previously only R. decoloratus and no R. microplus had been recorded in the vicinity of the two sites, R. microplus now comprised the bulk of collections at both. Furthermore, significantly more R. microplus were collected from cattle at both localities during the 2nd year of the survey than during the 1st. In addition to 83 instances of intraspecific coupling, there were 17 instances of R. microplus males coupled with R. decoloratus females. Collections made from cattle and goats on two farms close to the study sites revealed that R. microplus was present on both host species and that it significantly outnumbered R. decoloratus on one of the farms. Rhipicephalus decoloratus and R. microplus larvae as well as larvae exhibiting characteristics of both species were collected from the vegetation.     

Coitinuous cell lines from embryonic tissues of ticks (Acari: Ixodidae)

Summary Six new cell lines were established in continous culture from embryonic tissues of ixodid ticks. Four were fromDermacentor variabilis and two fromD. parumapertus. The cells are mostly fibroblastic and diploid. Mosquito-borne viruses (Chikungunya, O'nyong, yellow fever, and St. Louis encephalitis) as well as tick-borne ones (Langat, Powassan, Colorado tick fever, Kemerovo, and Sawgrass) replicated in certain of these cell lines, but a nonvector-borne flavivirus, Modoc, did not. An undescribed virus fromD. occidentalis ticks, which could not be isolated in Vero cells or newborn mice, was readily isolated in theD. variabilis cell line.     

Virulence,proteolytic and lipolytic activities of Brazilian Beauveria bassiana s.l. isolates (Hypocreales: Clavicipitaceae) to Rhipicephalus microplus ticks (Acari: Ixodidae)

Beauveria bassiana s.l. is a cosmopolitan fungus used in the control of different species of arthropods. The current study explored the virulence for ticks, proteolytic and lipolytic activities of 10 Brazilian B. bassiana s.l. isolates. For this purpose, Rhipicephalus microplus biological parameters was evaluated after immersion of the engorged females in fungal suspension (10⁸ conidia mL^?1) and the enzymatic activities were performed posteriorly the fungal growth in minimal medium. After the biological assays, five isolates changed all parameters analysed with highest efficacy of approximately 61% (CG 206) and 66% (CG 481). However, we observed that the most virulent isolates did not show the highest enzymatic activities. Interestingly, CG 500, considered an isolate of intermediate efficacy, demonstrated higher enzymatic activities than the other isolates in four of five analyses (total protease, Pr1, Pr2 and lipase; p?相似文献   

Short Communication Seasonal distribution of Rhipicephalus sanguineus ticks (Acari: Ixodidae) on dogs in an urban area of Morelos, Mexico

Between 1993 and 1995, we examined 1742 dogs at two veterinary clinics in Cuernavaca City in Mexico for the presence of Rhipicephalus sanguineus ticks. The overall tick infestation prevalence was 20% and there were no significant differences (p > 0.05) between different years. The prevalence was somewhat higher in spring, summer and autumn (20% or more) than in winter (13.7%). A positive correlation (p < 0.01) was found between prevalence of ticks and rainfall in spring, summer and autumn, whereas in winter there was only a correlation with temperature. Different stages of the tick were found and it was calculated that 2.5 generations could be completed each year. It is concluded that the enviromental conditions of Cuernavaca City favour development and maintenance of R. sanguineus ticks throughout the year and that its role as a vector of diseases poses a threat to dogs and may have potential zoonotic risks. © Rapid Science Ltd. 1998     

The distribution of ticks (Acari: Ixodidae) of domestic livestock in Portugal

This paper introduces the first countrywide faunistic study of the tick parasites on ruminants in Portugal. The aim of this study was to map accurately the distribution of the ticks Dermacentor marginatus, Rhipicephalus (Boophilus) annulatus, R. bursa, Hyalomma m. marginatum, H. lusitanicum and Ixodes ricinus in Portugal. Additional information about the abiotic preferences of these species has been obtained through the use of abiotic (temperature- and vegetation-derived) variables have been recorded from remotely sensed information at a nominal resolution of 1.1 km². A further aim was the development of predictive models of distribution using Classification and Regression Trees (CART) methodologies. Four species (R. annulatus, R. bursa, D. marginatus and H. m. marginatum) are mostly restricted to south-eastern parts of the country, under hot and dry climate conditions of Mediterranean type. H. lusitanicum has been collected almost only in the southern half of Portugal. I. ricinus has a very patchy distribution and is mainly associated with vegetation of Quercus spp., found in southern zones of the country, but it is present also in the more humid western part. A variable number of abiotic variables, mainly temperature derived, are able to describe the preferences of the tick species. It is remarkable that variables derived from maximum values of the Normalized Derived Vegetation Index (yearly or summer-derived) only apply to discriminate areas where I. ricinus has been collected. CART models are able to map the distribution of these ticks with accuracy ranging within 75.3 and 96.4% of actual positive sites.     

Cuticular fatty acid profile analysis of three Rhipicephalus tick species (Acari: Ixodidae)

Cuticular fatty acids (CFA) are important constituents of the arthropod exoskeleton, serving as structural and defense components, and participating in intra-species communication. Here we describe for the first time a comparative analysis of the CFA profiles of three tick species of the genus Rhipicephalus: R. annulatus, R. bursa and R. sanguineus. CFA profiles were determined for R. bursa and R. sanguineus grown both on rabbit or calf, and for R. annulatus grown on calf. CFA composition was compared for each species before and after ethanol treatment, for different hosts of each species, and between the different species. Our data suggest that adsorption of the host’s fatty acids changes the apparent CFA composition. Ethanol treatment efficiently removed the unbound fatty acids from the ticks and revealed the actual composition. Comparison between ticks grown on rabbit versus calf showed significant difference in the relative abundance of fatty acids C14 and 9,12-C18:2 for R. bursa, and a difference in the relative abundance of C14 for R. sanguineus. Comparison of the CFA between the three species revealed significant differences in the abundance of fatty acids C16, 9,12-C18:2, 9-C18:1, C18 and C20. Our results show that while the host had a minor effect on CFA composition within each species, significant differences were observed in the CFA profiles of different species. We suggest that CFA profiles may be used to distinguish between related species. CFA analysis can also be used in studies of communication and defense mechanisms in ticks and other arthropods.     

Habitat use by cattle affects host contact with lone star ticks (Acari: Ixodidae)

The location of Zebu, British, and Zebu x British cattle in tick-infested plots from March through September 1986 was compared with the location of Amblyomma americanum L. in the same plots. In April, May, and June, Zebu cattle spent less time (9.3-19.4%) in tick-infested quadrats than British (44.4-63.9%) or Zebu-British (49.0-69.3%) cattle. In the same months, the probability that A. americanum would contact Zebu cattle (1.5-19.6%) was significantly lower than for British (34.7-41.7%) or Zebu-British (30.2-56.9%) cattle. In April, May, June, and September, the probability that A. americanum detaching from cattle would drop into a quadrat presumed to be habitable for ticks was significantly lower for Zebu cattle (4.0-29.9%) than for British (64.9-72.6%) or Zebu-British (48.1-78.7%) cattle.     

Molecular detection of pathogen DNA in ticks (Acari: Ixodidae): A review

Ticks play an important role in human and veterinary medicine, in particular due to their ability to transmit a wide spectrum of pathogenic micro-organisms of protozoal, rickettsial, bacterial and viral origin. Pathogens in ticks can be identified by conventional methods such as indirect immuno-fluorescence, isolation in cell culture or by using histological staining techniques. However, the advent of the polymerase chain reaction (PCR) has resulted in tremendous improvements in the specific and sensitive detection of pathogen DNA in ticks. In this paper, literature on DNA extraction methods, PCR protocols, primers and probes, which are in use for the successful detection and identification of pathogens in ticks, are critically reviewed. Some recommendations are also given towards the end of tht review.