Clustering of host-seeking nymphal deer ticks (Ixodes dammini) infected by Lyme disease spirochetes (Borrelia burgdorferi).

In areas where the agent of Lyme disease is intensely enzootic, the mouse reservoirs may be universally infected. Because a large proportion of the vector tick population appears to feed upon these hosts, the prevalence of infection in the vectors should approach 100%. However, infection in host-seeking nymphal ticks in nature rarely exceeds 40%. To help reconcile this apparent paradox, we examined whether estimates of prevalence might differ if we did not assume that infected ticks are randomly or uniformly distributed within a site. Nymphal Ixodes dammini were collected by dragging a series of 10-meter replicates within an intensely enzootic site. Estimates of the prevalence of spirochetal infection, based upon the monthly means of individual 10-meter collections, were then compared with estimates derived by pooling all samples. Host-seeking ticks tended to cluster. The Lyme disease spirochete was present in 15.6% of 469 pooled ticks. When the prevalence estimate was based solely on ticks in clusters that contained one or more infected ticks, however, at least 50% of the ticks were infected. We conclude that nymphal deer ticks infected by Lyme disease spirochetes tend to aggregate spatially in nature, and that prevalence estimates based upon a mean value for pools may be misleading.

Enzootic transmission of the agent of Lyme disease in rabbits.

To determine whether cottontail rabbits (Sylvilagus floridanus) maintain an enzootic cycle of transmission of the Lyme disease spirochete (Borrelia burgdorferi), we examined the prevalence of infection in ticks and rabbits in a location in which rabbits were abundant. Of 72 unfed nymphal Ixodes dentatus swept from vegetation, 32% were infected by this spirochete, as determined by darkfield microscopy and indirect immunofluorescence using monoclonal antibody H5332. Infected ticks were reared from larvae feeding on each of 11 rabbits taken from the same site. Of 50 rabbits sampled there over a period of 2 years, sera of greater than 90% reacted with B. burgdorferi antigen by ELISA and by immunoblotting. Deer ticks (I. dammini) comprised less than 10% of ticks found on rabbits. We conclude that rabbits perpetuate the agent of Lyme disease in an enzootic cycle where rabbit-feeding Ixodes are abundant, that intensity of transmission is independent of the zoonotic cycle in mice, but that infection may occasionally be exchanged between these cycles.

The ecology of Colorado tick fever in Rocky Mountain National Park in 1974. II. Infection in small mammals.

Field studies of Colorado tick fever (CTF) in small mammals in Rocky Mountain National Park (RMNP) in 1974 established that Eutamias minimus and Spermophilus lateralis were the most important hosts for CTF virus and were the source of virus for immature stages of the tick vector, Dermacentor andersoni. Other species (Peromyscus maniculatus, Spermophilus richardsonii, Eutamias umbrinus) are secondary hosts. The intensity of viral activity in rodents varied greatly from locality to locality. Highest rodent infection rates were found to occur in the Moraine Park area of RMNP. Lowest infection rates occurred above 3,290 meters in altitude at Rainbow Curve and on the tundra. The prevalence of infection in rodents was constant from April--July (5--6% of animals captured were viremic) and then declined to 1.7--2.5% in August and September coincident with a decline in nymphal tick ectoparasitism. Many animals were captured which were simultaneously viremic and antibody-positive. Under field conditions, neutralizing antibody seroconversion does not always occur.

Erythema chronicum migrans of Lyme disease.

Erythema chronicum migrans (ECM) is the distinctive cutaneous lesion of the multisystem tick-borne spirochetosis, Lyme disease. Its clinical and histologic pictures are variable. Of the 51 patients with ECM of Lyme disease, 38 patients (75%) had single lesions, 13 patients (25%) had multiple lesions, and 32 patients (62%) had extracutaneous signs and symptoms. Only 15 patients (29%) had symptoms referable to ECM. Extracutaneous signs and symptoms were absent in 12 (80%) of the 15 patients. These patients had uneventful recoveries following treatment with systemic antibiotics. Thirty-four skin biopsy specimens were obtained from the ECM lesions of 30 patients. With Warthin-Starry silver stain, the Ixodes dammini spirochete was found in 14 specimens (41%) taken from 12 (40%) of the 30 patients. Two of the Ixodes dammini spirochete-positive specimens were obtained from secondary ECM lesions. Careful clinical and histologic examination of skin lesions suggestive of ECM of Lyme disease will expedite its early diagnosis and treatment.

Quantitative evaluation of sampling methods for Ixodes dammini and Amblyomma americanum (Acari: Ixodidae).

Three tick-sampling methods (dry ice-baited tick traps, cloth drags, and ambulatory human host) were evaluated to determine which technique yielded the greatest capture of host-seeking stages of Ixodes dammini Spielman, Clifford, Piesman & Corwin and Amblyomma americanum (L.). The most reliable method, catching more stages and significantly more numbers of I. dammini and A. americanum; was dry ice-baited tick traps. There were no significant differences between the drag and human-host methods for any stage of ticks (I. dammini and A. americanum) collected. The numbers of ticks caught during the study were 5,052 by dry ice-baited tick traps, 199 by cloth drags, and 89 by ambulatory human host.

Tick sweep: modification of the tick drag-flag method for sampling nymphs of the deer tick (Acari: Ixodidae).

We describe a version of the standard tick drag-flag modified for use in close-growing and tangled vegetation, as well as under ornamental shrubbery and fallen branches. Two major features of the sweep are: (1) it allows the user to remain upright with the flag parallel to the ground, thus sampling effectively beneath low and fallen branches and around shrubs, as well as capturing host-seeking ticks in advance of the operator; and (2) the use of a flannel rubberized-laminate fabric (crib sheet) for the flag that is snag-proof and highly durable in dense and thorny vegetation. In simultaneous 100-m samples, the sweep was as effective as the 1-m standard tick drag for capturing nymphs of the deer tick, Ixodes dammini Spielman, Clifford, Piesman & Corwin, where understory vegetation was sparse, but was twice as effective in dense vegetation, capturing significantly more I. dammini nymphs. The sweep also captured nymphs of the American dog tick, Dermacentor variabilis (Say); rabbit tick, Haemaphysalis leporispalustris (Packard); and lone star tick, Amblyomma americanum (L.).

Ornithodoros (Alectorobius) capensis Neumann (Acari: Ixodoidea: Argasidae), a parasite of seabirds, established along the southeastern seacoast of the United States.

Ornithodoros (Alectorobius) capensis Neumann, an ectoparasite of seabirds found circumglobally in the tropics and subtropics, has become established along the southeastern seacoast of the United States. The tick has been found feeding primarily on brown pelicans, Pelecanus occidentalis, but also has been found on the laughing gull, Larus atricilla, and the American oystercatcher, Haematopus palliatus. We report here the presence of O. (A.) capensis from New Hanover and Brunswick counties (near the mouth of the Cape Fear River) in North Carolina, to the Charleston Harbor area of South Carolina and thence south to Cumberland Island (a barrier island) in Camden County, Georgia, just north of the Florida state line.

New host of Ixodes dentatus (Acari: Ixodidae), and first record in Tennessee.

Two specimens of Ixodes dentatus Marx were found in southwestern Tennessee in Shelby County during a 14-mo tick survey. This was the first record for this tick in Tennessee. An adult female was found on a dry ice trap and one larva was found on a live-trapped Peromyscus leucopus, the first time this tick has been reported from P. leucopus. This may be another combination of vector and host in the ecology and transmission of B. burgdorferi in the wild.

First report of Ixodes (Ixodes) minor Neumann (Acari: Ixodidae) from South Carolina.

Previous reports from the literature have indicated the northernmost range of extension of Ixodes minor Neumann to be southern Georgia with the greatest number of collections having been made in the coastal regions of that state. An unpublished record in the U.S. National Tick Collection indicated that I. minor had been collected as far north as South Island, Georgetown County, S.C., as early as 1933. I. minor was collected on three separate occasions in Charleston County, S.C., between October 1990 and February 1991, thus verifying the northern extension of this tick's range and the probable existence of a stable population on the coast of South Carolina. The roof rat (Rattus rattus) is reported for the first time serving as a host for I. minor.

Subadult Ixodes ricinus (Acari: Ixodidae) on rodents in Berlin, West Germany.

To identify hosts that may serve as reservoirs for the agent of Lyme disease in Central Europe, we determined whether Ixodes ricinus L. feed most frequently on certain rodents and whether the abundance of these hosts corresponds to the season of feeding activity of the tick in four sites in Berlin, Federal Republic of Germany. In addition, we correlated abundance of I. ricinus with that of particular rodent hosts. Two small rodents were more abundant than any others; a mouse, Apodemus flavicollis, predominated in a wooded site and a vole, Clethrionomys glareolus, in three brush- or grass-covered sites. The tick was most abundant in the mouse-infested site. Although A. flavicollis comprised only about a third of rodents collected, nearly 60% of all such rodent parasitizing I. ricinus fed on this mouse. These ticks were more abundant on mice than voles in each of the study sites and throughout the year, and more larvae fed on these rodents than did nymphs. Although larval as well as nymphal I. ricinus are most abundant during midsummer, they feed on rodents from April through October. Taken together, these observations suggest A. flavicollis as a potentially important reservoir host for I. ricinus-borne infections.

Parasitization of humans in West Virginia by Ixodes cookei (Acari: Ixodidae), a potential vector of Lyme borreliosis.

In 32 collections, two larvae, 33 nymphs, and one adult female Ixodes cookei Packard were collected from humans in West Virginia from August 1987 to May 1990. Most were attached. The ticks were found in 14 counties and were the most abundant Ixodes found biting humans. One nymphal I. cookei was removed from the left axilla of a 39-yr-old woman who lives and works in Monongalia and Marion counties, W. Va. The bite was the center of an expanding erythematous lesion reaching 4 cm in diameter, clearing centrally, and typical of erythema migrans. This association and the near absence of Ixodes dammini Spielman, Clifford, Piesman & Corwin from the state suggests the possibility that I. cookei may be an important vector of Lyme borreliosis in West Virginia. In five separate collections, five nymphal Ixodes dentatus Marx were removed from humans in four counties, implicating this species as a potential minor vector of Lyme borreliosis in West Virginia.

Efficacy of ivermectin delivered from an intraruminal sustained-release bolus against natural infestations of five African tick species on cattle.

The efficacy of ivermectin delivered by an orally administered prototype sustained-release bolus over approximately 90 days was evaluated against natural infestations of five African tick species. Twenty cattle, allocated by restricted randomization based on counts of standard Boophilus decoloratus, were allocated to two groups and were either given an ivermectin bolus or designated as non-medicated controls. All cattle grazed a single pasture of native grasses for 20-40 days before treatment and until trial termination. Starting on Days 27, 40, 68 and 82 after bolus administration, four replicates were confined to individual tick-collection stanchions for 4 to 5-day periods. Ticks recovered from these cattle were counted by species, sex, and stage and degree of repletion; engorged females were weighed and incubated to determine the number which oviposited. For the other replicates, half-body counts of adult ticks (classified by species, sex and degree of repletion by females) were made at 1- and 2-week intervals through Day 90. Among replicates confined to stanchions periodically, fewer (P less than 0.05) engorged adult female B. decoloratus, Hyalomma spp., Rhipicephalus appendiculatus and Rhipicephalus evertsi evertsi were collected from bolus-treated cattle than from controls. Numbers of engorged adult female Amblyomma hebraeum were reduced, but differences were not statistically significant (P greater than 0.10). Among cattle maintained continuously on pasture, tick numbers were reduced on the ivermectin-treated groups. A significant (P less than 0.05) treatment by linear time effect was seen for all adult ticks counted except R. appendiculatus. A significant (P less than 0.05) treatment by quadratic time effect was seen for A. hebraeum, B. decoloratus and R. evertsi evertsi, and overall treatment differences were significantly different (P less than 0.05) for these species. The differences tended to increase with time. Except for Boophilus, reductions in tick numbers on treated animals relative to controls were not readily apparent. There were no adverse reactions attributable to ivermectin treatment or the presence of the bolus. Each treated animal retained its bolus throughout the trial, based on metal detection.

Some ecological observations on two east-Mediterranean species of Haemaphysalis ticks parasitizing domestic stock.

Haemaphysalis cretica and H. otophila thrive in the Mediterranean phytogeographic zone of the eastern Mediterranean area. Haemaphysalis otophila has a wide geographical distribution, H. cretica is more restricted. The adults of both species parasitize sheep and goats, and transmit diseases. The pre-imaginal stages feed on reptiles and small mammals. Adults attach to their hosts only during winter. The pre-oviposition period is long and the embryonic development is slow. Larvae hatch in spring and attach to their hosts in early summer; nymphs follow somewhat later and descend off their hosts in late summer. There is only one generation per year for each of the species.

Efficacy of topically applied ivermectin against Boophilus microplus (Canestrini, 1887) in cattle.

Systemic efficacy of ivermectin applied topically was evaluated against the cattle tick, Boophilus microplus. Twenty cattle with induced infestations were randomly allocated to five groups of equal size based on the numbers of engorged female ticks which fell through the slatted floor of individual pens during the 3 days prior to treatments. Control cattle were non-medicated. Cattle in three groups were given ivermectin at 200, 500 or 1000 mcg kg-1 in a topical formulation applied along the backline from the withers to the rump; cattle in the fifth group were given ivermectin in an injectable formulation subcutaneously at 200 mcg kg-1. Individual 24-h tick collections were made three times weekly for 5 weeks after treatment. Engorged female B. microplus were incubated to determine effects on reproduction. Based on the numbers of engorged female B. microplus collected following treatments, overall efficacy of ivermectin applied topically at 200, 500 and 1000 mcg kg-1 was 50, 85 and 91%, respectively, whereas ivermectin given at 200 mcg kg-1 subcutaneously was 80% effective. The index of reproduction for ivermectin given topically was reduced by 84, 94 and 95%, respectively, and that for ivermectin subcutaneously was 94%. No significant differences (P greater than 0.05) were found for these variables between ivermectin given topically at 500 or 1000 mcg kg-1 versus 200 mcg kg-1 given subcutaneously.

Parasite burdens and host susceptibility of Zebu and N'Dama cattle in village herds in Gambia.

Helminth and tick burdens of N'Dama cattle kept in village herds were compared with parasite burdens in Zebu cattle introduced into the same herds. The animals were monitored regularly for tick and helminth burdens, and blood samples were examined for differential white cell counts. The Zebu were found to have significantly higher numbers of endo- and ectoparasites. The N'Dama had significantly higher levels of circulating eosinophils than the Zebu during peak parasite burdens. No difference in antibody levels to Amblyomma variegatum infestation could be detected between the two breeds. It is suggested that observed differences in susceptibility to endo- and ectoparasites between the two breeds cannot be totally attributed to environmental naivety of the Zebu, but must be partially owing to enhanced innate resistance factors in the N'Dama.

The subgenus Persicargas (Ixodoidea: Argasidae: Argas): A. (P.) arboreus central nervous system anatomy and histology.

The anatomy and histology of the adult Argas (Persicargas) arboreus central nervous system are described and compared with these properties in other ticks. The single, integrated, central nerve mass (CNM) is formed by a fused supra-esophageal part (protocerebrum, cheliceral ganglia, palpal ganglia, and stomodeal pons) and a subesophageal part (4 pairs of pedal ganglia and the complex opisthosomatic ganglion). Single peripheral nerves (pharyngeal and recurrent) and paired peripheral nerves (compound protocerebral, cheliceral, palpal, pedal and opisthosomatic) extend from the CNM to body organs and appendages. Optic nerves, described in other Argas species, are not found in A. (P.) arboreus. Histologically, the CNM is enclosed by a thin-walled periganglionic blood sinus and invested by a collagenous neural lamella followed by a perineurial layer composed of glial cells and containing fine reticular spaces, a cortical layer of association, motor and neurosecretory cell bodies and glial cells, and inner neuropile regions of fiber tracts forming 5 horizontal levels of connectives and commissures.

Ectoparasites of sympatric cottontails (Sylvilagus audubonii Nelson) and jack rabbits (Lepus californicus Mearns) from the high plains of eastern New Mexico.

Eight species of ectoparasites were recovered from 35 Sylvilagus audubonii and 35 Lepus californicus occurring sympatrically near the Clovis-Portales area of eastern New Mexico. Recovered were Anoplura (Haemodipsus setoni), Diptera (Cuterebra lepusculi and Cuterebra ruficrus), Siphonaptera (Echidnophaga gallinacea and Euhoplopsyllus glacialis), and Acari (Ornithodoros parkeri, Dermacentor parumapertus, and Haemaphysalis leporispalustris). Jaccard's index showed a 50% ectoparasitic overlap with H. setoni, E. glacialis, D. parumapertus, and H. leporispalustris present on both host species. Cuterebra lepusculi, E. gallinacea, and Ornithodoros parkeri were taken only from S. audubonii, whereas C. ruficrus occurred only on jack rabbits. Euhoplopsyllus glacialis was the only species to demonstrate a preference for sex of host, occurring more abundantly on females.

Raccoon babesiosis in Connecticut, USA: Babesia lotori sp. n.

A species of Babesia which infects raccoons, Procyon lotor, is described and named Babesia lotori. Twelve of 14 raccoons captured from five counties in Connecticut developed parasitemia after splenectomy. Preoperative levels were subpatent or less than 1%. Parasitemia peaked anywhere from less than 5% to 36.6% in splenectomized raccoons, and all but one survived and possessed low infection rates (less than or equal to 3%) at the end of the experiment. An indirect fluorescent antibody test is described and shown to be useful in detecting antibodies to B. lotori. Seropositive raccoons were obtained from six counties. Two, Babesia-free, splenectomized raccoons developed parasitemia with corresponding increases in antibody titers after they were inoculated with infected blood. Antibody titers of naturally infected raccoons following splenectomy either remained stable or increased fourfold. Babesia was observed in three of four young raccoons which had been naturally confined to chimneys. Two of these four young raccoons were infested with a nest-dwelling tick, Ixodes texanus.

[Haemaphysalis concinna Koch, 1844 in Italy]. / Haemaphysalis concinna Koch, 1844 in Italia.

The authors provide here the data concerning the first italian finding of tick Hemaphysalis concinna (Ixodidae). Two males of this species--which has a large geographic diffusion--were actually caught for the first time in Italy, in July 1977. They were found on the ground of the Castel Porziano estate (Rome) at sealevel, in two different grassy places. The authors describe their morphological characters and provide some essential data on the environment of Castel Porziano.

Borrelia burgdorferi in ticks of the Canton Tessin (Switzerland).

In the northern Alps it is hard to find an Ixodes ricinus population which does not harbour Borrelia burgdorferi. The infection rates range from 5 to 34% for adults and nymphs to 3.1% for larvae. This study shows that the infection rates on the southern side of the Alps are similar, at 25% for adults, 36.2% for nymphs and 3.2% for larvae. With respect to tick species other than I. ricinus, we did not succeed in finding any spirochetes in Dermacentor marginatus, Haemaphysalis punctata, Ixodes hexagonus, Rhipicephalus sanguineus.