Infected Adult Ticks Research Articles

The spatial distribution of Borrelia burgdorferi-infected Ixodes ricinus in the Connemara region of County Galway, Ireland.

Studies were carried out in the Connemara area of County Galway in the west of Ireland in order to determine the abundance and distribution of the tick, Ixodes ricinus and the prevalence of its infection with Borrelia burgdorferi. The tick was very abundant locally, in particular when associated with cattle, sheep and enclosed red deer. Large numbers of ticks not only occurred on the pastures, but also on adjacent roadside verges. No infections with B. burgdorferi could be demonstrated when nymphal ticks were sampled from central areas of the pastures, suggesting that livestock and red deer are probably not significant reservoirs of the spirochaete. Small numbers of infected nymphal and adult ticks were associated with hedges, dry stone walls, the margins of woodland adjoining infested pastures and in woodland from which livestock were excluded. Woodmice (Apodemus sylvaticus) were most numerous in such habitats and the majority were infected with B. burgdorferi.

Competence of dogs as reservoirs for Lyme disease spirochetes (Borrelia burgdorferi)

Summary Dogs become infected with Borrelia burgdorferi after being bitten by infected adult ticks. However, it is not known whether dogs are competent reservoirs of the organism, that is, it is not known whether infected dogs can subsequently transmit the bacterium to feeding immature ticks. To determine reservoir competence of dogs, 11 Beagles were experimentally infected by means of challenge exposure to infected adult deer ticks (Ixodes scapularis). Three weeks later, larval ticks were allowed to feed on the dogs. Engorged larvae were collected, allowed to molt to the nymph stage, and tested, by means of a direct fluorescent antibody assay, to detect the presence of B burgdorferi organisms. Overall, 78% of immature ticks tested were found to have become infected. We concluded that dogs might serve to increase human risk of exposure to B burgdorferi-infected ticks and, therefore, should be protected from exposure to infected ticks as well as immature ticks seeking a blood meal.

Experimental Lyme Disease in Dogs Produces Arthritis and Persistent Infection

Lyme disease was reproduced in specific pathogen-free beagle dogs by exposure to Borrelia burgdorferi-infected ticks (Ixodes dammini). Seroconversion and disease frequency were higher after exposure to infected adult ticks than to infected nymphs. Young pups developed clinical disease more readily than older dogs. The incubation period lasted 2-5 months. Acute recurrent lameness with fibrinopurulent arthritis was the dominant clinical sign. Dogs recovered but developed persistent mild polyarthritis. B. burgdorferi persisted in recovered dogs for at least 1 year. Isolation of B. burgdorferi and detection by polymerase chain reaction was most successful from skin biopsies at the site of the tick bite. Antibody to B. burgdorferi antigens was first detected by ELISA and Western blots by 4-6 weeks after exposure. High serum levels persisted during 17 months of observation. In contrast to infection from ticks, inoculation of dogs with cultured B. burgdorferi resulted in seroconversion with a shorter duration of antibody persistence and no clinical disease.

Lyme disease: a proposed ecological index to assess areas of risk in the northeastern United States.

Recent public awareness has resulted in a demand for information about ways to reduce the risk of acquiring Lyme disease. Twenty-two school properties and recreational areas within a Lyme disease endemic area of central Monmouth County, New Jersey were evaluated for risk of transmission using an ecological index on the suitability, amount, and access to Ixodes dammini habitat by target human populations and the abundance of infected adult ticks. The characterization of tick habitat accurately predicted the elimination of 11 sites from concern. Of the remaining 11 sites, six were classified high risk and five as moderate risk. On-site tick surveys identified infected I. dammini adults at only four sites (three risk; one moderate risk). These results indicate that the use of selected ecological parameters provides a cost-effective method to rapidly identify areas at risk for Lyme disease transmission.

The distribution of African swine fever virus isolated from Ornithodoros moubata in Zambia.

African swine fever (ASF) has been reported in the Eastern Province of Zambia since 1912 and is now considered to be enzootic there. A survey of the distribution of ASF virus in Zambia was carried out by virus isolation from Ornithodoros moubata ticks collected from animal burrows in National Parks and Game Management Areas in northern, eastern, central and southern Zambia. ASF virus was isolated from ticks in all areas examined. The prevalence of infection in O. moubata was between 0.4% in South Luangwa National Park and 5.1% in Livingstone Game Park and mean infectious virus titres ranged from 10(3.4) HAD50/tick in Kakumbe Game Management Area to 10(5.9) HAD50/tick in Chunga and Nalusanga Game Management Areas. The prevalence of infection in adult ticks was between 4.7% and 5.3% in all areas examined except Sumbu National Park and Livingstone Game Park, where the prevalence was 15.1% and 13.2% respectively in adult ticks. The ratio of infected females to males for all the infected adult ticks in all areas of Zambia was 3.2:1.

Borrelia coriaceae in its tick vector, Ornithodoros coriaceus (Acari: Argasidae), with emphasis on transstadial and transovarial infection.

Field and laboratory studies demonstrated that transovarial passage of the recently described spirochete Borrelia coriaceae occurs occasionally in the soft tick Ornithodoros coriaceus Koch, but this process appeared to be inefficient for maintaining and distributing the spirochete. Borreliae were detected in only 5 (0.6%) of 883 wild-caught O. coriaceus larvae and in a low percentage of the F1 (larval) progeny from only one of nine spirochete-infected females. Infected and uninfected females did not differ statistically in fecundity or fertility. Transstadial survival of spirochetes also occurred in O. coriaceus , but experimental evidence suggests that some ticks may lose their infections during or after ecdysis. The distribution of spirochetes in tissues of infected nymphs and adult ticks that fed to repletion and later molted or oviposited was generalized or semigeneralized. Neither the coxal fluid nor the hemolymph test was found to be reliable for detecting spirochetes in ticks. Borreliae in tissue smears prepared from 1 of 18 spirochete-infected O. coriaceus nymphs and adults reacted with a monoclonal antibody (H5332) that is reportedly specific for Borrelia burgdorferi . The potential significance of this finding is discussed briefly.

The establishment of infection in the salivary glands of Rhipicephalus appendiculatus ticks by transplantation of kinetes of Theileria parva and the potential use of the method for parasite cloning

Fujisaki K., Irvin A. D., Voigt W. P., Leitch B. L. and Morzaria S. P. 1988. The establishment of infection in the salivary glands of Rhipicephalus appendiculatus ticks by transplantation of kinetes of Theileria parva and the potential use of the method for parasite cloning. International Journal for Parasitology 18: 75–78. A simple method was developed to establish infection of a single salivary gland acinus of the tick Rhipicephalus appendiculatus with kinetes of Theileria parva. Kinetes were obtained from haemolymph of newly-moulted infected adult ticks and injected into the haemolymph of unfed adult ticks. The latter ticks were subsequently fed on rabbits; salivary glands were dissected out and acinar infection rates established. Transplantation of 16–138 kinetes into unfed female ticks resulted in infection of one or more salivary gland acini. Infection could not be reliably established in male ticks, nor in female ticks with fewer than 16 kinetes. The potential use of this method to obtain cloned populations of T. parva sporozoites is discussed.

Identification ofTheileriainfections in living salivary glands of ticks

SUMMARYIt was found that interference contrast microscopy gave good morphological differentiation of the living and intact salivary glands from adult ixodid ticks,Rhipicephalus appendiculatusandAmblyomrna variegatum, removed by dissection. In many cases the individual cell types of the acini could be recognized. When the salivary glands of infected adult ticks were examinedTheileriaparasites were detected.Theileria parva, T. taurotragiandT. mutanscould be detected in the salivary glands after they reached the mature secondary sporoblast stage achieved even in unfed ticks. Parasites were detected only in type III acini. The morphology of tertiary sporoblasts and sporozoites of theseTheileriaspp. was clearly recognized in feeding ticks. Sporozoites ofT. parvaproved to be infective to cattle and to peripheral blood leucocytes of cattlein vitroafter interference contrast examination. Interference contrast examination of living salivary glands was used for selection of salivary glands with high infections ofT. parvasporozoites and the sporozoites could be separated in large numbers from these salivary glands. Using this technique it appeared possible to cloneTheileriaparasites from salivary glands with 1 infected acinus.

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.