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PubMed1977

The transmission of Theileria annulata to a rabbit by the larvae of the tick Hyalomma rufipes.

A New Zealand White rabbit on which larvae of Hyalomma rufipes were fed died of theileriosis due to Theileria annulata 22 days after the larvae had fed. The larvae were direct progeny of an enorged female collected from trade cattle in the veterinary control post at Ibadan. The danger attending the feeding on rabbits of first progeny of ticks collected from cattle in countries where some tick-borne diseases are endemic is highlighted. The possibility of transovarial transmission of Theileria is discussed.

Animals↗
PubMed1985

An in vivo comparison of the efficacy of the heartwater blood and ground-up tick suspension vaccines in calves.

Two groups of calves were respectively immunized with heartwater blood (BV) and ground-up tick suspension (GUTS) vaccine. A third group was left unimmunized as controls. No difference in the immune status conferred could be demonstrated between the 2 vaccines at 6 months and 12 months challenge after vaccination. An index, based on the rectal temperature before and during the reaction, was calculated as an aid in evaluating the data. In practice, the evaluation of heartwater vaccination by challenge is more effective at 12 months than at 6 months after vaccination. No effective difference was demonstrated between the 2 vaccines in their immunizing efficacy.

Animals↗
PubMed2004

Effects of Anaplasma phagocytophilum infection on the molting success of Ixodes scapularis (Acari: Ixodidae) larvae.

We assessed the effects of sympatric (occupying the same or overlapping geographic areas) and allopatric (occurring in separate geographic areas) isolates of Anaplasma phagocytophilum on the survival of Ixodes scapularis Say larvae that were derived from ticks collected in Bridgeport, CT. Seven isolates of A. phagocytophilum, originating from different geographic regions of the United States, were tested: four isolates from the northeast (Bridgeport, Dawson, Gaillard, and NY-8), two from the Midwest (Webster and Sp-Is), and one from California (MRK). BALB/c mice were infected with each of the seven isolates via exposure to infected I. scapularis nymphs, whereas uninfected nymphs fed upon control mice. Both infected and control mice were infested with uninfected larvae at 1, 2, 3, 4, 6, and 9 wk after nymphal infestation. The molting success in cohorts of infected and uninfected ticks was calculated as the percentage of larvae successfully molting into nymphal stage, and the prevalence of infection in molted nymphs was determined by polymerase chain reaction. In ticks that became infected with the Bridgeport or Sp-Is isolates, the molting success decreased with an increase in the prevalence of infection. Ticks that fed upon mice infected with six allopatric isolates (Dawson, Gaillard, NY-8, Sp-Is, Webster, and MRK) showed significantly lower levels of survival than those fed upon control mice, regardless of the prevalence of infection, whereas in ticks fed upon mice infected with a sympatric isolate (Bridgeport), the overall molting success was similar to the control. Thus, some but not all of the A. phagocytophilum isolates have adverse effects on ticks. Ticks exposed to harmful isolates may experience higher levels of bacterial metabolism, and/or reduced quality of their blood meal, thereby reducing their survival. Noted differences between isolates may be due to the origin of a particular isolate and/or the degree of coadaptation between the pathogen and its vector on the population level.

Anaplasma↗
PubMed2003

Antigens from Rhipicephalus sanguineus ticks elicit potent cell-mediated immune responses in resistant but not in susceptible animals.

In the present study we compared the immunological reactions between Rhipicephalus sanguineus tick-infested susceptible (dogs and mice) and tick-resistant hosts (guinea pigs), elucidating some of the components of efficient protective responses against ticks. We found that T-cells from guinea pigs infested with adult ticks proliferate vigorously in the presence of concanavalin A (ConA), whereas ConA-induced cell proliferation of tick-infested mice and dogs was significantly decreased at 43.1 and 94.0%, respectively, compared to non-infested controls. Moreover, cells from mice and dogs submitted to one or three successive infestations did not exhibit a T-cell proliferative response to tick antigens, whilst cells from thrice tick-infested guinea pigs, when cultured with either a tick extract or tick saliva, displayed a significant increase in cell proliferation. Also, we evaluated the response of tick-infested mice to a cutaneous hypersensitivity test induced by a tick extract. Tick-infested mice developed a significant immediate reaction, whereby a 29.9% increase in the footpad thickness was observed. No delayed-type hypersensitivity (DTH) reaction was detected. Finally, the differential cell count at the tick attachment site in repeatedly infested mice exhibited a 6.6- and 4.1-fold increase in the percentage of eosinophils and neutrophils, respectively, compared to non-infested animals, while a decrease of 77.0-40.9 in the percentage of mononuclear cells was observed. The results of the cutaneous hypersensitivity test and the cellular counts at the tick feeding site for mice support the view that tick-infested mice develop an immune response to R. sanguineus ticks very similar to dogs, the natural host of this species of tick, but very different from guinea pigs (resistant host), which develop a DTH reaction in addition to a basophil and mononuclear cell infiltration at the tick-attachment site. In conclusion, saliva introduced during tick infestations reduces the ability of a susceptible animal host to respond to tick antigens that could stimulate a protective immune response. As a consequence, the animals present a lack of DTH response and disturbed cellular migration to tick feeding site, which can represent a deficient response against ticks.

Animals↗
PubMed1995

The Lyme disease vaccine candidate outer surface protein A (OspA) in a formulation compatible with human use protects mice against natural tick transmission of B. burgdorferi.

Development of a vaccine for the Lyme disease spirochete, Borrelia burgdorferi, has focused on the bacterial lipoprotein, major outer surface protein A (OspA). With few exceptions, testing of OspA vaccines in animal models has involved challenge with needle inoculation of cultured spirochetes. Recombinant OspA proteins from two OspA divergent strains of B. burgdorferi were tested for their vaccine potential in three different strains of mice challenged with laboratory reared ticks with a high rate of B. burgdorferi infection. All formulations of the B. burgdorferi sensu stricto derived OspA vaccine protected all strains of mice when challenged by ticks infected with an OspA homologous strain of the spirochete, whereas heterologous OspA from B. afzelii did not protect. Furthermore, ticks feeding on protected mice had reduced OspA levels compared to unvaccinated controls.

Animals↗
PubMed1995

Tick salivary gland physiology.

The multifunctional, morphologically complex salivary glands are essential to the biological success of ticks and are intricately involved in the transmission of pathogens. They are innervated, and there is convincing evidence that dopamine is a neurotransmitter at the neuroeffector junction controlling fluid secretion. As feeding progresses, the rate of salivary fluid secretion increases greatly, enabling the ixodid tick to concentrate the bloodmeal by returning excess water and ions to the host. Saliva in feeding ticks is rich in bioactive components and exhibits a range of pharmacological properties. Factors identified in saliva or salivary glands include cement to help anchor the mouthparts to the host, various enzymes and inhibitors, histamine agonists and antagonists, prostaglandins, antihemostatic factors, and immuno-modulating factors. A secretion from the salivary glands allows ticks to absorb water from the air during the lengthy periods off their hosts. The physiology of this remarkable organ provides a striking example of strategies that have evolved to meet the challenge of a unique parasitic life style.

Animals↗
PubMed1998

Detection of Borrelia burgdorferi sensu lato in ticks: immunofluorescence assay versus polymerase chain reaction.

Immunofluorescence (IFA) and polymerase chain reaction (PCR) were examined as methods for detecting Borrelia burgdorferi sensu lato spirochaetes in unfed Ixodes ricinus nymphs. Although similar results were produced in some cases, a great deal of variation occurred. Furthermore, in both the highly controlled initial laboratory study, involving 252 shared samples, and the study on field-collected ticks (n = 460), the IFA tended to detect more infected ticks than the PCR. The basis for these findings are as yet undetermined. The development of a quality assurance scheme is recommended so that laboratories can validate their methods and a preliminary feasibility study suggested that such a scheme is practical.

Animals↗
PubMed1989

Immunoprophylactic control of bovine babesiosis: role of exoantigens of Babesia.

A major breakthrough in babesiosis vaccine research was achieved with the development of methods for continuous propagation in vitro of Babesia parasites. The development of a soluble, exoantigen-containing immunogen, free of erythrocytic antigens, has been proposed as a practical and realistic means of immunoprophylactic control of babesiosis. Such immunogens have been tested for immunogenicity of different strains, minimal protective dose, and protective efficacy of a combined B. bovis-B. bigemina immunogen. During the last 7 years, most of these aspects have been studied in a co-operative research programme between the University of Illinois and the Veterinary Research Institute of Venezuela. The Babesia exoantigen vaccine prevents clinical disease, is effective against different parasite strains, induces protective immunity for at least 13 months, does not immunize against host blood groups, is antigenically stable for at least 3 years at 4 degrees C, and is available in large quantities. Continued improvement of currently available culture-derived immunogens will best guarantee the successful production of food-producing animals in the tropics. Since July 1984, 16 field vaccination trials have been conducted in 7 states of Venezuela in areas where large-scale dairy and beef production is crucial for the livestock industry. These ranches encompassed a cattle production of 14,000, of which 3000 have been vaccinated with a combined B. bovis-B. bigemina immunogen in 2 subcutaneous inoculations with a 4-week interval. In the first 5 trials, a 1-year monitoring period following vaccination and natural tick exposure indicated that the culture-derived vaccine has effectively controlled the clinical manifestation of infection. Studies on antigen characterization are shifting the emphasis from crude antigenic preparations to purified polypeptides, isolated and identified using new biochemical techniques. Current research efforts are directed toward isolation of protective antigens and the production of synthetic vaccines. Until optimal molecular vaccines are developed, a polyvalent inactivated B. bovis-B. bigemina immunogen may offer the best combination of potency, efficacy and safety available for effective immunoprophylaxis against bovine babesiosis.

Animals↗
PubMed1999

Experimental studies of interactions between wild turkeys and black-legged ticks.

Wild turkeys are increasing in abundance and distribution in eastern North America, but their potential role as hosts for ticks, or as predators on ticks, is unknown. We performed two experiments, one to determine whether juvenile black-legged ticks (Ixodes scapularis) feed successfully on turkeys, and the other to determine if turkeys depredate adult black-legged ticks in forest habitats. Of 550 larval ticks placed directly on 5 captive wild turkeys, none engorged and only 7 (1.3%) were recovered; the remainder apparently were consumed during preening. Of 165 nymphal ticks placed on the turkeys, 5 engorged and 8 unengorged ticks were collected; 152 (93.3%) were apparently consumed. Of 250 adult ticks introduced into forest enclosures exposed to turkey foraging, 89.5% were recaptured, which was not significantly different from the 92.2% recaptured in control enclosures from which turkeys were excluded. We conclude that wild turkeys are unlikely to host juvenile black-legged ticks in nature, and that turkey foraging is unlikely to reduce local density of adult ticks.

Animals↗
PubMed1989

Disease and mortality in small ruminants in the North West Province of Cameroon.

Mortality rates and the prevalence of disease were assessed in 115 flocks of traditionally managed sheep and goats in two Divisions of the North West Province of Cameroon by means of a questionnaire to the owners. The mortality rate was significantly higher in sheep than in goats and also higher in young stock than in adults. Tethering the animals during the day resulted in significantly lower mortality in both adult and young sheep and also in kids. Disease problems of small ruminants, identified on the basis of signs reported by their owners, included intestinal parasitism, especially helminthiasis, tick infestation and associated diseases, pneumonia, goat plague (peste des petits ruminants) and Oestrus ovis infestation. Treatment of sick animals was only practised on a very small scale, often by possibly ineffective traditional methods. The owners identified tick infestation and diarrhoea as common causes of death. Recommendations are made on control measures suitable for application in this area.

Animal Husbandry↗
PubMed2006

Cross-sectional survey of ixodid tick species on grazing cattle in Japan.

Ixodid tick species were collected from cattle in 60 grazing fields throughout Japan. Haemaphysalis longicornis was mainly recovered in the western and southern regions, while Ixodes species were collected mainly in the central to northern regions. Other tick species such as Amblyomma testudinarium, Boophilus microplus, H. flava and H. kitaokai were identified from a few fields in the central and southern regions. Haemaphysalis longicornis were recovered in the fields with higher temperatures and annual rainfall, whereas I. ovatus and I. persulcatus were collected in fields with lower temperatures and annual rainfall. Some of these tick species are capable of transmitting pathogens harmful to cattle and humans, so proper control strategies are required.

Animals↗
PubMed1986

Attempted transmission of Ehrlichia risticii by field-captured Dermacentor variabilis (Acari: Ixodidae).

The capability of field-collected American dog ticks, Dermacentor variabilis, to infect horses with Ehrlichia risticii, causative agent of Potomac horse fever (PHF), was examined by allowing adult ticks collected from horse farms with a history of PHF to feed on susceptible horses. More than 500 male and female ticks attached and fed on 3 test horses; however, no clinical or serologic evidence of PHF was observed in treated or control horses. All horses were challenge exposed with E risticii-infective blood by inoculation at 60 to 65 days after ticks fed, and all developed clinical PHF with subsequent seroconversion. The data, therefore, indicated that adult D variabilis, a common parasite of horses on Maryland premises where PHF is enzootic, may not serve as a vector of E risticii.

Animals↗
PubMed2000

Larval survival of Anocentor nitens under simulated natural conditions.

Basic knowledge about the survival of free living stages of ticks is of great importance as a practical tool to improve control methods. For Anocentor nitens there is little information on this subject. Eighty-four engorged females were incubated at 30 degrees C and 100% relative humidity. After 17 days, groups of 5,500 eggs each were collected and isolated in vials. Age zero was defined as 10 days after eclosion had begun. At this time vials with larvae were attached to 40 Sorghum halepense plants sowed in clay pots, under outdoor conditions, and separated from one another by 30 cm in order to prevent the larvae from mixing. Four hours later vials were retired and the larvae remaining in the vials were counted. The next day four plants were sampled and this survival considered as 100%. Each week for eight weeks the same sampling procedure was performed. The remaining four plants were used to determine the maximum larval survival (MLS). Four repetitions of the procedure were performed, two in March 1989 and two in September 1989.

Animals↗
PubMed1990

Immunization of cattle against Theileria parva bovis and their exposure to natural challenge.

Theileria parva bovis isolates were tested for their immunizing capacity under natural field challenge on Willsbridge Farm in the highveld of Zimbabwe. Fifteen susceptible Sussex yearlings were immunized with the Boleni stock and 15 with a mixture of three isolates from the farm, using tick-derived sporozoite stabilates. No chemoprophylaxis was used. A dose of 0.1 ml of stabilate appeared to be safe in preliminary laboratory experiments, but the reactions were severe in the Sussex cattle and one died despite treatment. Twenty-nine immunized animals and 10 controls first experienced a mild infection, starting about 15 days after their arrival at the farm. Ten of the immunized animals and four controls had schizonts in peripheral lymph nodes for variable periods; one third of those had pyrexia. Nymphal Rhipicephalus appendiculatus ticks applied to three of the reacting immunized calves transmitted Theileria taurotragi to two animals and T. parva to a third. A second Theileria infection, due to T. parva bovis, was detected shortly after the first one. Schizonts were detected in seven out of 10 controls. Pyrexia was more severe and prolonged. Two of the controls died of theileriosis. At the same time schizonts were seen in three immune animals and eight of them had short periods of pyrexia. Intercurrent infections with Babesia bigemina, Borrelia theileri and Eperythrozoon were detected and may have contributed to the fever. Tick infestations were low during the exposure. In the second year of exposure, four out of eight new control animals had severe reactions, and one died. None of the immunized animals became ill, but one animal from the first year control group, which had not reacted previously, had clinical theileriosis. It is concluded that immunization provided an effective protection against field challenge.

Animals↗
PubMed2002

Resistance of the tick dermacentor variabilis (Acari: Ixodidae) following challenge with the bacterium Escherichia coli (Enterobacteriales: Enterobacteriaceae).

In addition to a soluble response, many invertebrates control bacterial infections by means of phagocytosis or melanotic encapsulation. In some insects, Escherichia coli growth is reported to be inhibited by aggregation/encapsulation. Soluble and phagocytic responses to bacterial challenge have been reported in ticks, but evidence of an aggregation / encapsulation response was reported only for inanimate (araldite) implants. Ticks were challenged by direct inoculation of bacteria into the hemocoel cavity. By plating, no viable E. coli were detected 6 h postinoculation. A direct fluorescence assay (DFA) revealed aggregated bacteria 1 h postinoculation. Furthermore, DFA showed aggregated bacteria at 6,24, and 48 h postinoculation associated with masses of tissue, presumably of cellular origin, suggesting events similar to those described as nodulation. These findings suggest that encapsulation/ nodulation may be an important component of the immune response in ticks.

Animals↗
PubMed2004

Immune-responsive lysozymes from hemocytes of the American dog tick, Dermacentor variabilis and an embryonic cell line of the Rocky Mountain wood tick, D. andersoni.

Immune-responsive lysozyme encoding cDNAs were identified from two medically important tick species by an expressed sequence tag approach of D. variabilis hemocytes (Dv Lys) and a D. andersoni embryonic derived cell line, DAE100. Comparative sequence analyses indicated the Dermacentor molecules to be products of orthologous genes and to be most similar to arthropod c-type lysozymes. Northern blotting analyses demonstrated that Dv Lys expression levels were most abundant in tick hemocytes and to a much lesser degree in the midgut while barely detectable in ovary, salivary gland, and Malpighian tubule tissues. Involvement of the Dermacentor c-type lysozymes in innate immunity was demonstrated by Escherichia coli challenges of D. variabilis ticks by injection resulting in a temporal profile of significantly elevated transcript abundances above those of naive controls that was similarly observed of the D. andersoni cells co-cultured with E. coli. In contrast to that reported of the digestive gut lysozyme of the soft tick Ornithodoros moubata, Dv Lys levels were not statistically differentially regulated by blood meal digestion. Additionally, given the differences in tissue distribution, sequence characteristics and phylogenetic placements between the Dermacentor and Ornithodoros lysozymes demonstrates that ticks possess differently adapted c-type lysozymes that are spatially and temporally differentially expressed.

Amino Acid Sequence↗