Study of the circulation of Crimean hemorrhagic fever virus in Turkmenistan]

Final results of the virological and serological investigations of the circulation of the Crimean hemorrhagic fever virus in the Turkmenian SSR carried out in 1968-1976 are presented in this report. In the examination of 2294 blood serum samples of human beings complement binding antibodies against the Crimean hemorrhagic fever were revealed in 0.4% of cases. It was revealed that five species of ixodes ticks could he infected with this virus; for the first time its strains were also isolated from the Hyalomma dromedarii ticks. Isolation of the Crimean hemorrhagic fever virus from ticks and determination of the precipitating antibodies against this virus in agricultural animals--from 6.2 to 11.1%--in all the regions of the republic pointed out that the natural nidi zones were widespread at the territory of the Turkmenian SSR, and that it was necessary to carry out further study of the given focus.     

Crimean hemorrhagic fever in the Rostov region: epidemiological zoning and the activity of natural foci

The epidemiological zoning of the territory of the Rostov region has been made with the use of the epidemic process patterns and the data indicating the links between the landscape and the natural focus of infection. The spread of infected ticks has been established. The participation of several carrier species in the circulation of Crimean-Congo haemorrhagic fever virus has been confirmed. The mosaic character of their distribution and different levels of their contamination is of great prognostic importance. These data will be used for the improvement of epidemiological surveillance in working out the tactics of epizootological surveys and organization of prophylactic measures.     

The effect of various host species on the feeding performance of immature stages of the tick Hyalomma truncatum (Acari: Ixodidae)

In order to determine the effect of various hosts on the feeding performance of the tick Hyalomma truncatum, we used three mammalian species as hosts. Larvae and nymphs of H. truncatum were fed, under controlled laboratory conditions, on gerbils, guinea-pigs and rabbits. The larvae fed for 4.3±1.4 days on gerbils, 5.6±1.3 days on guinea-pigs and 4.7±1.2 days on rabbits. The mean weights of the larvae which fed on the rabbits, guinea-pigs and gerbils were 0.58± 0.09, 0.46±0.04 and 0.45±0.04 mg. respectively. The feeding periods of the nymphs on gerbils, guinea-pigs and rabbits were 7.9±1.3, 8.6±1.3 and 9.6±2.2 days respectively. The mean weights of the nymphs which fed on the gerbils, guinea-pigs and rabbits were 22.5±2.8, 19.7±1.3 and 15.8±1.4 mg, respectively. Hyalomma truncatum demonstrated a life cycle of a three-host tick on gerbils and guinea-pigs and of a two-host tick on rabbits. The evolutionary advantage of a two-host cycle over a three-host cycle in metastriate ticks is discussed.     

Range expansion of the tick Amblyomma triguttatum triguttatum, an australian vector of Q fever

The tick Amblyomma triguttatum triguttatum has previously been reported from Western Australia, Queensland and New South Wales. A viable population of this species, including all developmental stages, has now been discovered on the southern end of Yorke Peninsula, South Australia. Species determination was carried out morphologically and using 18S and 16S rRNA. The data for 16S rRNA are the first published for this species. Amblyomma t. triguttatum is significant through its involvement in the natural, Australian cycle of Coxiella burnetti, the pathogen causing Q fever. The environment of Yorke Peninsula contains all of the components required for a natural Q fever cycle and three cases of this disease have been reported from this area since 1995. These findings reinforce the need to put in place effective mechanisms to monitor parasite distributions at a time of large scale global change.     

A tick B-cell inhibitory protein from salivary glands of the hard tick, Hyalomma asiaticum asiaticum

Some studies done to date suggest that B-cell inhibitory factor occurred in tick saliva. In this study, a novel protein having B-cell inhibitory activity was purified and characterized from the salivary glands of the hard tick, Hyalomma asiaticum asiaticum. This protein was named B-cell inhibitory factor (BIF). The cDNA encoding BIF was cloned by cDNA library screening. The predicted protein from the cDNA sequence is composed of 138 amino acids including the mature BIF. No similarity was found by Blast search. The lipopolysaccharide-induced B-cell proliferation was inhibited by BIF. This is the first report of the identification and characterization of B-cell inhibitory protein from tick. The current study facilitates the study of identifying the interaction among tick, Borrelia burgdorferi, the causative agent of Lyme disease, and host.     

East coast fever: 60Co-irradiation of Theileria parva in its tick vector, Rhipicephalus appendiculatus

Three experiments were carried out in which Theileria parva was irradiated in its tick vector, Rhipicephalus appendiculatus. In the first experiment, infected unfed adult ticks were irradiated at doubling doses from 4 to 32 krad. Some of the ticks were then fed for 4, 5, 6, 7 and 8 days on rabbits, and the parasites in their salivary glands examined. Five male and 5 female ticks from each irradiation dose were put onto each of a pair of susceptible cattle, whose reactions were recorded. Increasing doses of irradiation resulted in progressive destruction of the parasites. All cattle receiving ticks irradiated at doses up to and including 16 krad died of East Coast fever (ECF), and one of the cattle receiving ticks irradiated at 32 krad died.In the second experiment, recently engorged nymphs were irradiated at 1, 2 or 4 krad, and moulting nymphs at doses of 2, 4, 8, 12, 16 or 32 krad. The salivary glands of the resultant adult ticks were examined after the ticks had fed for 4, 5, 6, 7 or 8 days on rabbits. Engorged nymphs irradiated at 4 krad failed to moult, whilst moulting nymphs irradiated at 32 krad moulted but failed to attach to rabbits. Doses of irradiation survived by the ticks had no apparent morphological effect on the parasites they contained.In the third experiment, infected unfed adult ticks were irradiated at 0, 5, 10, 15, 20 25 30, 35, 40, 45, 50 or 60 krad. The ticks were fed on rabbits for 5, 6 or 7 days. Some of them were then examined morphologically, whilst others were ground in MEM/BPA and aliquots of the supernatant used to inoculate groups of 5 cattle. The reaction of these cattle, together with the morphological examination of the parasites, suggested that increasing doses of irradiation destroyed increasing numbers of parasites.     

Prevalence of Theileria in the tick Hyalomma detritum detritum in the Doukkala region,Morocco

Abstract. The overall prevalence of Theileria species, mainly, if not exclusively, T.annulata, in 901 Hyalomma detritum detritum collected from cattle in the Doukkala region of Morocco over a period of 2 years was 21.5%. The quantity of infection (number of sporoblasts per infected tick) followed the negative binomial distribution with between one and 250 sporoblasts per infected tick. Infected ticks were found in eight of fourteen areas examined whilst T.annulata was present in all fourteen. There were significant differences in both the prevalence and the quantity of infection between ticks collected from different farms, and between nymphs collected in the autumn from these farms, and moulted in the laboratory, and adults collected in the following summer. The prevalence, but not the quantity, of infection was higher in female than in male ticks. No correlations were established between infection of engorged nymphs and the breed, sex and Theileria piroplasm parasitaemia of the host animal. However, calves infected a greater proportion of nymphs than adult cattle and the heavier the infestation of nymphs on an animal, up to a plateau, the higher the prevalence of infection in those nymphs. There were no differences in infection between ticks moulted at 24^oC and 37^oC, after the engorged nymphs had been stored at 18^oC to simulate over-wintering.     

The effect of chemotherapy on Babesia bigemina in the tick vector Boophilus microplus

Percentages of feeding ticks in which Babesia bigemina could be detected (infection rates) were determined following treatment of bovine hosts with each of four babesicides. Infection rates were suppressed by imidocarb dipropionate, quinuronium sulphate and amicarbalide, reaching minimum levels 3–4 days after treatment, but imidocarb dihydrochloride had comparatively little effect. Total elimination of the parasite from ticks was not achieved. Treatment of tick infested hosts with imidocarb dipropionate or quinuronium sulphate failed to prevent transmission of B. bigemina by transovarian passage or by transfer of adult male ticks. These findings indicate that the use of babesicides for chemotherapy is unlikely to have a significant effect on the rate of transmission of B. bigemina.     

Effects of immunization of rabbits on establishment, survival, and reproductive biology of the tick Hyalomma anatolicum anatolicum.

Four antigenic preparations, viz. salivary gland antigen (SG Ag), whole tick extract antigen (WTE Ag) and 30,000-g supernatant fraction, and pellet of WTE Ag (TES Ag and TEP Ag, respectively), were made from partially fed adult female Hyalomma anatolicum anatolicum. Four groups of 5 rabbits each were immunized with the antigens, and a fifth group was kept as control. Following challenge with adult H. a. anatolicum, a significant decrease in engorgement weight and egg mass weight and an increase in engorgement period and preoviposition period were observed in WTE Ag-immunized rabbits. Similar results were observed with TES Ag and SG Ag, except that change in the engorgement period was insignificant. However, none of the tick parameter measurements showed significant changes with TEP Ag. None of the antigens produced significant changes in the percentage of engorgement or oviposition period of the challenged ticks. Thus, WTE Ag was the most effective in altering tick performances.     

Developmental profiles in tick water balance with a focus on the new Rocky Mountain spotted fever vector, Rhipicephalus sanguineus

Recent reports indicate that the common brown dog tick, or kennel tick, Rhipicephalus sanguineus (Latreille) (Acari: Ixodidae) is a competent vector of Rocky Mountain spotted fever in the U.S.A. This tick is of concern to public health because of its high frequency of contact, as it has a unique ability to thrive within human homes. To assess the moisture requirements necessary for survival, water balance characteristics were determined for each developmental stage, from egg to adult. This is the first time that water relations in ticks have been assessed throughout the complete lifecycle. Notably, R. sanguineus is differentially adapted for life in a dry environment, as characterized by a suppressed water loss rate distinctive for each stage that distinguishes it from other ticks. Analysis of its dehydration tolerance limit and percentage body water content provides no evidence to suggest that the various stages of this tick can function more effectively containing less water, indicating that this species is modified for water conservation, not desiccation hardiness. All stages, eggs excepted, absorb water vapour from the air and can drink free water to replenish water stores. Developmentally, a shift in water balance strategies occurs in the transition from the larva, where the emphasis is on water gain (water vapour absorption from drier air), to the adult, where the emphasis is on water retention (low water loss rate). These results on the xerophilic-nature of R. sanguineus identify overhydration as the primary water stress, indicating that this tick is less dependent upon a moisture-rich habitat for survival, which matches its preference for a dry environment. We suggest that the controlled, host-confined conditions of homes and kennels have played a key role in promoting the ubiquitous distribution of R. sanguineus by creating isolated arid environments that enable this tick to establish within regions that are unfavourable for maintaining water balance.     

Cholesteryl esters on the body surfaces of the camel tick,Hyalomma dromedarii (Koch, 1844) and the brown dog tick,Rhipicephalus sanguineus (Latreille, 1806)

Cholesteryl esters were found to constitute a major component of the lipids coating the body cuticle of females of the camel tick, Hyalomma dromedarii and the brown dog tick, Rhipicephalus sanguineus. One or more cholesteryl esters, alone or in combination, have been shown to serve as the mounting sex pheromone of several species of ixodid ticks. Consequently, knowledge of these compounds is important for an understanding of the mating behavior of these ticks. Based on thin layer chromatography, cholesterol and cholesteryl esters were the most abundant neutral lipids found on the body surfaces of fed females of these two species. Analysis using HPLC demonstrated significant quantities of the following compounds, tentatively identified as cholesteryl esters (expressed in micrograms per female equivalent), in H. dromedarii: Cholesteryl acetate 18.2; cholesteryl laurate, 6.8; cholesteryl linoleate, 24.8; cholesteryl oleate, 12.9; cholesteryl palmitate, 0.3; and cholesteryl stearate 1.7.In contrast, the same method revealed only 3 cholesteryl esters in extracts of females of R. sanguineus: Cholesteryl acetate, 2.0; cholesteryl linoleate, 8.5; and cholesteryl oleate, 3.0. In both species, two unidentified peaks, with the spectral characteristics of cholesteryl esters, were also observed. Identification of the cholesteryl esters was confirmed: by (1) positive bioassay results with conspecific (H. dromedarii) males and heterospecific (Dermacentor variabilis) males; (2) similarity of ultraviolet spectra between identified sample peaks and authentic standards; and (3) demonstration of cholesterol and the corresponding free fatty acid following enzymatic digestion of each of the HPLC-separated fractions containing the different cholesteryl esters. Comparisons with the cholesteryl ester composition of the mounting sex pheromone of other metastriate Ixodidae are discussed. These findings, along with studies reported previously, suggest that differences in the mounting sex pheromones of ixodid ticks are an important factor in minimizing heterospecific matings in nature.Supported by Cooperative Agreement No. 263-0152-A-00-2207 with the U. S. Agency for International Development to the Department of Infectious Diseases. College of Veterinary Medicine, University of Florida, Gainesville, FL and a subcontract, ODURF No. 536521, to the Department of Biological Sciences, Old Dominion University, Norfolk, VA     

Molecular divergences of the Ornithodoros sonrai soft tick species, a vector of human relapsing fever in West Africa

The soft tick Ornithodoros sonrai is recognized as the only vector of Borrelia crocidurae causing human relapsing fever in West Africa. Its determination has been exclusively based on morphological features, geographical distribution and vector competence. Some ambiguities persist in its systematics and may cause misunderstanding about West African human relapsing fevers epidemiology. By amplifying and aligning 16S and 18S rDNA genes in O. sonrai specimens collected from 14 distinct sites in Senegal and Mauritania, we showed the existence of four genetically different subgroups that were morphologically and ecologically identified as belonging to the same species. Within O. sonrai, intraspecific polymorphism was high (pairwise divergence from 0.2% to 16.4%). In all cases, these four subgroups formed a monophyletic clade sharing a common ancestor with East African soft ticks that transmit Borrelia duttoni human relapsing fever. From amplification of the flagellin gene of B. crocidurae we verified that all subgroups of O. sonrai were infected by B. crocidurae and may constitute vectors for this pathogen. All flagellin sequences were identical, refuting the hypothesis suggesting parallel evolution between O. sonrai and B. crocidurae. However, differences in infection rates were significant, suggesting different vector competences between subgroups of O. sonrai.     

Isolation and characterization of an anticoagulant present in the salivary glands of the bont-legged tick,Hyalomma truncatum

A low molecular mass anticoagulant (17 kDa) was isolated from the salivary glands of prefed female Hyalomma truncatum ticks by means of reverse phase and anion-exchange HPLC. Trypsin digestion and amino acid analysis confirmed the protein nature of the anticoagulant. The inhibitor appears to be uncompetitive with a K_i of 6.9×10^–10M. The target of the anticoagulant is factor Xa at the junction of the extrinsic and intrinsic pathways. This may be crucial for the survival of the tick, making it feasible to investigate the possibility of vaccination with this antihaemostatic against tick feeding. In addition, tick anticoagulants may possibly have therapeutic application in controlling thrombosis.