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PubMed1993

Reduced abundance of immature Ixodes dammini (Acari: Ixodidae) following incremental removal of deer.

The abundance of immature Ixodes dammini Spielman, Clifford, Piesman & Corwin was monitored for 9 yr (1983-1991) before and during the controlled, limited hunting of white-tailed deer, Odocoileus virginianus (Zimmerman), at a coastal Massachusetts site. Deer abundance was reduced from an estimated 350 during 1985 to approximately 60 during 1991. Although annual fluctuations were large, mean larval I. dammini abundance declined from 20.8 per white-footed mouse, Peromyscus leucopus (Rafinesque), during 1983-1986 before deer reduction to 10.3 per mouse following deer reduction (1987-1991). Similarly, mean nymphal I. dammini abundance declined from 2.7 per mouse before intervention to 1.6 per mouse after intervention. Immature I. dammini population fluctuations were not associated with those of P. leucopus. The total population of larvae infesting P. leucopus declined from 3,596 ticks before intervention to 1,535 ticks after intervention. Concurrently, the total nymphal population declined from 417 ticks before intervention to 187 ticks after intervention. The number of feeding adult female I. dammini on deer increased as deer density decreased.

Animals↗
PubMed1993

Reservoir competence of white-footed mice for Babesia microti.

Although the white-footed mouse, Peromyscus leucopus Rafinesque, has been incriminated as the main reservoir of the agent of human babesiosis, Babesia microti Franca, a quantitative demonstration of reservoir competence has not been presented. Mice captured within an intensely zoonotic site served as host for laboratory-reared larval Ixodes dammini Spielman, Clifford, Piesman, and Corwin, and the resulting nymphal ticks were assayed for evidence of salivary gland infection by the piroplasm. Solely 25% of the mice were patently parasitemic on thin blood smears, but virtually all mice infected ticks with B. microti. Thus, smear positivity correlates poorly with infectivity. Infection in smear-negative mice, however, was demonstrated by the use of the polymerase chain reaction. White-footed mice may be chronically infected by the piroplasm with parasitemias detectable only by the most sensitive methods, yet efficiently serve as a source of infection. We conclude that P. leucopus serves to maintain B. microti in the northeastern United States, as it does the spirochetal agent of Lyme disease.

Animals↗
PubMed1993

Reduced abundance of Ixodes scapularis (Acari: Ixodidae) with exclusion of deer by electric fencing.

To assess the effect of deer exclusion on populations of Ixodes scapularis Say (formerly I. dammini Spielman, Clifford, Piesman & Corwin) in the northeastern United States, host-seeking ticks and ticks on white-footed mice, Peromyscus leucopus (Rafinesque), were monitored inside and outside a wooded, residential deer exclosure (approximately 3.5 ha) in Lyme, CT, in 1991 and 1992. Another deer exclosure was added in Lyme (approximately 7.4 ha) during 1992. Additional sample sites at other residences served as secondary controls. A seven-wire, slanted, high-tensile electric deer fence was used at both areas. Larvae of I. scapularis were 81.5% (1991) and 97.8% (1992) less abundant within the exclosure than immediately outside the deer exclosures. Nymphs of I. scapularis were 47.4% (1991) and 55.8% (1992) less abundant within the deer fence. The effect on adult ticks was mixed. No difference in tick abundance was seen at the 3.5-ha site. However, larvae, nymphs, and adults were 100, 83.8, and 74.1% less abundant, respectively, in plots at the 7.4-ha exclosure > or = 70 m from the deer fence and isolated from woodlands outside the fence by lawns, driveways, and buildings. The recovery of larvae and nymphs of I. scapularis from mice captured within the deer exclosures indicates that infestations of nymphs and adults are probably, at least in part, a result of the movement of these rodents. Based upon the number of nymphs per 100 m2 infected with Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner, the causal agent of Lyme disease, there were 73 and 82% fewer infected nymphs within the deer exclosures in 1992 in comparison with the number of infected ticks outside the fence and at the secondary control sites, respectively. The exclusion of deer in conjunction with other tick control strategies in large areas could substantially reduce populations of I. scapularis and the risk of acquiring Lyme disease.

Animals↗
PubMed1994

Vector competence of Ixodes pacificus and Dermacentor occidentalis (Acari: Ixodidae) for various isolates of Lyme disease spirochetes.

The vector competence of the western black-legged tick, Ixodes pacificus Cooley & Kohls, and the Pacific Coast tick, Dermacentor occidentalis Marx, for the Lyme disease spirochete (Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner) was compared. Rabbits, hamsters, and the deer mouse, Peromyscus maniculatus (Wagner), were injected with cultured spirochetes or infected tick-suspensions, or were fed upon by spirochete-infected ticks. Five of seven isolates used as inocula were reisolated from vertebrates with the ear-punch biopsy technique. Three isolates (CA4, 5, 7) that were infectious for both vertebrates and ticks possessed prominent low-molecular-weight protein bands that had relative mobilities of approximately 24-26 kd. The ability of ticks to acquire and maintain various inocula of B. burgdorferi was evaluated by feeding uninfected larvae xenodiagnostically on all three hosts 0-63 d postinjection. Low percentages (0-10.6%) of the I. pacificus and none of the D. occidentalis became infected. By contrast, 33% of I. pacificus and 40% of Ixodes scapularis Say (= I. dammini Spielman, Clifford, Piesman & Corwin) that fed on hamsters infected by tick-bite acquired and transstadially passed spirochetes; 10% of D. occidentalis fed on infected hamsters similarly acquired but did not maintain spirochetes. Ixodes pacificus nymphs efficiently transmitted B. burgdorferi to deer mice and a hamster. Feeding by one spirochete-infected nymph was sufficient to produce patent infections in each of five mice.

Animals↗
PubMed1995

Ticks (Acari: Ixodidae) infesting wild birds (Aves) and white-footed mice in Lyme, CT.

Birds were captured and recaptured (20.8% of 5,297) with Japanese mist nets, and white-footed mice, Peromyscus leucopus (Rafinesque), were caught and recaught (69.1% of 355) with Sherman box traps during the late spring, summer, and early fall from July 1989 through October 1991 to study tick-host relationships in Lyme, CT. Ixodes scapularis Say, a vector of Lyme disease spirochetes, Borrelia burgdorferi sensu stricto Johnson, Schmid, Hye, Steigerwalt & Brenner, infested 803 birds (15.2%) in 36 species and 148 (40.3%) of the mice. This tick dominated both birds (94.4% of 4,065 ticks) and mice (82.6% of 529 ticks). Other ticks that were recovered from birds were Haemaphysalis leporispaustris (Packard) (23 birds in seven species), I. dentatus Marx (34 birds in 14 species), and Dermacentor variabilis (Say) (two birds in two species). The latter was also collected from 12.7% of the 355 mice (n = 92 ticks). Infestations of I. scapularis were high for worm-eating warblers (30.6% of 111), ovenbirds (44.4% of 286), common yellowthroats (27.1% of 188), hooded warblers (35% of 80), Carolina wrens (50.9% of 110), house wrens (21.6% of 102), wood thrushes (23.0% of 867), veeries (32.5% of 246), and American robins (36.2% of 69). Coinfestation by larvae and nymphs of I. scapularis was significantly high for Carolina wrens (35.7% of 56 infested individuals), veeries (27.2% of 80), American robins (29.4% of 25), and common grackle (19.0% of 5), possibly enhancing transmission of B. burgdorferi. Mean crowding on larvae by nymphs, measured by Lloyd's index (1967), was highest for these four species (range 1.19-5.76). Seasonal patterns of infestation for each species of bird can account for much of the differences in degree of coinfestation. High infection rates by B. burgdorferi in larvae removed from some of these birds (14.9-20.0%) were found on those birds with both high numbers of larvae and nymphs. Spirochetemia in most avian hosts may be short and only certain species with concurrent infestations of nymphs and larvae may function effectively as reservoirs.

Animals↗
PubMed1996

Spread of Ixodes scapularis (Acari:Ixodidae) in Indiana: collections of adults in 1991-1994 and description of a Borrelia burgdorferi-infected population.

Collection records for the adult black legged tick, Ixodes scapularis Say, in Indiana for the period 1991-1994 are presented and a new, established population of Borrelia burgdorferi-infected I. scapularis is described. The number of I. scapularis adults collected in Indiana increased progressively from 19 in 1991 to > 200 in 1994, and the number of Indiana counties reporting at least 1 adult increased from 13 to 29. Also, during this period, 4 countries in northwestern Indiana yielded > 10 specimens each, and B. burgdorferi-infected ticks were collected in 2 of these counties. An established population of I. scapularis, as evidenced by the presence of questing larvae, nymphs, and adults, was discovered in Jasper County in 1993. Twelve of 39 adults (31%) and 4 of 44 nymphs (9%) collected with cloth drags were infected with B. burgdorferi. Three of 49 (6%) white-footed mice, Peromyscus leucopus, collected from the site were also infected with B. burgdorferi. We believe that this focus was established at least 8 yr ago, and that a tick originating from this focus was responsible for a case of Lyme disease reported from this county in 1985.

Animals↗
PubMed1996

Entomological correlates of Babesia microti prevalence in an area where Ixodes scapularis (Acari:Ixodidae) is endemic.

Zoonotic prevalence of Babesia microti Franca piroplasms infecting white-footed mice, Peromyscus leucopus Rafinesque, was determined at 34 sites in Rhode Island where nymphal blacklegged tick, Ixodes scapularis Say, densities ranged from low to hyperabundant (1.7-525.3 nymphs per hour of flagging). Babesia was only detected at sites where tick abundance was moderate to high (> 20 nymphs per hour of flagging) and appeared to exhibit a clumped distribution. Where B. microti was detected, the mean number of nymphal ticks collected per hour of flagging was 229.2 compared with a mean of 40.1 at sites where Babesia was not detected. By combining the spatial occurrence of Babesia with a tick density database in a geographic information system, it may be possible to predict the pattern of zoonotic and human infection with B. microti.

Animals↗
PubMed1997

Simulation of blacklegged tick (Acari:Ixodidae) population dynamics and transmission of Borrelia burgdorferi.

A model (LYMESIM) was developed for computer simulation of blacklegged tick, Ixodes scapularis Say, population dynamics and transmission of the Lyme disease agent. Borrelia burgdorferi Johnson. Schmid, Hyde, Steigerwalt & Brenner, LYMESIM simulates the effects of ambient temperature, saturation deficit, precipitation, habitat type, and host type and density on tick populations. Epidemiological parameters including host infectivity, tick infectivity, transovarial transmission, and transstadial transmission are included in the model to simulate transmission of the Lyme disease spirochete between vector ticks and vertebrate hosts. Validity of LYMESIM was established by comparing simulated and observed populations of immature I. scapularis on white-footed mice. Peromyscus leucopus, (Rafinesque), at 2 locations in Massachusetts. Validity also was indicated by comparisons of simulated and observed seasonality of blacklegged ticks in New York, Massachusetts, Florida, and Oklahoma-Arkansas. Further model validity was shown by correlation between simulated and observed numbers of immature ticks engorging on white-footed mice at 3 sites in Massachusetts. The model produced acceptable values for initial population growth rate, generation time, and 20-yr population density when historical meteorological data for 16 locations in eastern North America were used. Realistic rates of infection in ticks were produced for locations in the northeastern and northcentral United States. LYMESIM was used to study the effect of white-footed mouse and white-tailed deer, Odocoileus virginianus (Zimmerman), densities on tick density and infection rates. The model was also used to estimate tick density thresholds for maintenance of B. burgdorferi.

Animals↗
PubMed1998

Focal epidemic of sarcoptid (Acarina: Sarcoptidae) mite infestation in an insular population of white-footed mice.

The abrupt and focal emergence of an infestation of sarcoptid mites was documented during long-term studies of populations of the white-footed mouse, Peromyscus leucopus (Rafinesque), on Nantucket Island, MA. From 1985 to 1996, > 1,000 trap nights were recorded each year in 2 permanently situated sampling grids that were sampled monthly from April through November. In April 1995, prominent excrescences were first noted on the pinnae of mice trapped solely from 1 of the 2 sites. Histopathology of the lesions suggested infestation with Notoedres spp. Of 140 unique captures of mice during 1995-1997, 77% were infested as determined by the presence or absence of macroscopic ear lesions. Both sexes were likely to be infested, but juvenile mice were twice as likely to be noninfested. No lesions were noted in 103 mice concurrently sampled from a grid situated 15 km away, nor in mice from other sites in coastal New England. The origin of this epidemic remains obscure. This unusual infestation exemplifies the emergence of zoonotic infections, but at the level of an enzootic cycle.

Animals↗
PubMed1998

Reservoir competence of the meadow vole (Rodentia: Cricetidae) for the Lyme disease spirochete Borrelia burgdorferi.

The reservoir competence of the meadow vole, Microtus pennsylvanicus Ord, for the Lyme disease spirochete Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner was established on Patience Island, RI. Meadow voles were collected from 5 locations throughout Rhode Island. At 4 of the field sites, M. pennsylvanicus represented only 4.0% (n = 141) of the animals captured. However, on Patience Island, M. pennsylvanicus was the sole small mammal collected (n = 48). Of the larval Ixodes scapularis Say obtained from the meadow voles on Patience Island, 62% (n = 78) was infected with B. burgdorferi. Meadow voles from all 5 locations were successfully infected with B. burgdorferi in the laboratory and were capable of passing the infection to xenodiagnostic I. scapularis larvae for 9 wk. We concluded that M. pennsylvanicus was physiologically capable of maintaining B. burgdorferi infection. However, in locations where Peromyscus leucopus (Rafinesque) is abundant, the role of M. pennsylvanicus as a primary reservoir for B. burgdorferi was reduced.

Animals↗
PubMed1998

Dermacentor hunteri (Acari: Ixodidae): seasonal variation in questing adults and on-host juvenile stages, and host associations and feeding behavior of larvae and nymphs.

Dermacentor hunteri Bishopp is the only completely desert adapted tick in the Nearctic realm, and chiefly parasitizes desert bighorn sheep (Ovis canadensis Shaw) as an adult. The remainder of its life history has been unknown. We conducted field investigations in the Sonoran desert of the temporal and spatial variation of adult host-seeking ticks and of the host associations of juvenile ticks. Additionally, the feeding success of juvenile ticks was assessed in the laboratory. Adult ticks were found in significant numbers only in plateau and rocky slopes habitats, chiefly during the period from January to June. Questing adults were not found in July and August, and they were present in small numbers from September through December. Juvenile stages were found only on desert woodrats, Neotoma lepida Thomas (larvae and nymphs), and cactus mice, Peromyscus eremicus Baird (larvae only), in March, May, and early June. In the laboratory; both larvae and nymphs fed on N. lepida, but only larvae fed on P. maniculatus bairdii (Wagner). We concluded that the life history of D. hunteri may be constrained by the co-distribution of desert bighorn, desert woodrats, and perhaps cactus mice; and that adults oversummer either on desert bighorn or sequestered in favorable microclimates off the host.

Animals↗
PubMed1999

Comparative vector competence of Dermacentor variabilis and Ixodes scapularis (Acari: Ixodidae) for the agent of human granulocytic ehrlichiosis.

Vector competence of Ixodes scapularis Say and Dermacentor variabilis Say for the agent of human granulocytic ehrlichiosis (HGE) was compared. Five white-footed mice, Peromyscus leucopus Rafinesque, were inoculated intra-peritoneally with blood from a mouse infected with the agent of HGE. Approximately 100 I. scapularis and D. variabilis larvae were placed on each mouse and allowed to feed to repletion. Fed larvae were collected, separated according to species and allowed to molt to nymphs. Twenty-six per cent of I. scapularis (34/131) and 11% of D. variabilis (11/96) tested positive for the agent of HGE by polymerase chain reaction (PCR) after molting to nymphs. Positive I. scapularis nymphs transmitted the agent of HGE to P. leucopus mice in 5 of 5 trials. In contrast, the positive D. variabilis nymphs did not transmit the agent of agent of HGE in any of 6 trials. In a 2nd experiment, 3 P. leucopus mice were infested with I. scapularis nymphs that were infected with the agent of HGE. All 3 mice became infected with the agent of HGE and approximately 300 D. variabilis larvae were placed on each mouse and allowed to feed to repletion. Larvae were collected and allowed to molt to nymphs as before. Approximately 8% (5/60) of the nymphs became positive for the agent of HGE as determined by PCR. Twenty-five of these nymphs were then placed on each of 9 P. leucopus mice and allowed to feed to repletion. Evidence of transmission was not observed in any of 9 mice exposed to D. variabilis nymphs. These results demonstrate that although I. scapularis is a competent vector of the agent of the HGF, D. variabilis is not.

Anaplasmataceae↗
PubMed1999

Notes on responses of blacklegged ticks (Acari: Ixodidae) to host urine.

In laboratory bioassays under conditions of high humidity, host-seeking female black-legged ticks, Ixodes scapularis Say, avoided urine of reproductively active male and nonestrous female white-tailed deer, Odocoileus virginianus (Zimmermann), the principal host species of the adult stage. At 50% RH, female I. scapularis did not avoid urine from male and female deer. Larval and nymphal I. scapularis did not exhibit an arrestment response to urine from male and female white-footed mice, Peromyscus leucopus (Rafinesque), a major host for immature blacklegged ticks. These results suggest that under some conditions, urine from 2 principal host species in certain physiological states does not provide kairomonal cues that aid I. scapularis in contacting these host species.

Animals↗
PubMed1999

Abundance of Ixodes scapularis (Acari: Ixodidae) larvae and nymphs in relation to host density and habitat on Long Point, Ontario.

Ixodes scapularis Say populations were evaluated within 4 habitats on Long Point, Ontario, from 1990 to 1992 to ascertain whether differences in density of mouse populations within and among habitats were correlated with that of immature I. scapularis populations. I. scapularis immatures were rarely collected by dragging within the cottonwood dune habitat. Significantly more larvae (P < or = 0.05) were collected by drag sampling within the maple forest habitat than in the oak savannah or white pine habitats for the 1989, 1990, and 1991 cohorts, whereas the size of the 1992 larval cohort did not differ significantly among these habitats. Significantly more nymphs were collected by dragging within the maple forest than in the other 2 habitats for all 4 cohorts. Nymphs from the 1989 and 1990 cohort were more abundant within the oak savannah than the white pine habitat, whereas the 1991 and 1992 cohorts were similar. With few exceptions, I. scapularis immatures were most prevalent on white-footed mice, Peromyscus leucopus (Rafinesque), captured within the maple forest > oak savannah > white pine > cottonwood dune, although differences were not significant in all years and in all habitats. The number of mice captured within the 4 habitats was not correlated with the number of I. scapularis larvae or nymphs infesting them. Likewise, the minimum number of mice alive was not significantly correlated with conversion indices of larvae to nymphs or nymphs to adults. Lack of association between mouse availability and relative size of subsequent cohorts of host-seeking ticks suggests that factors other than the size of the mouse populations were responsible for the observed differences in tick abundance among habitats.

Animals↗
PubMed2005

Host associations of Ixodes scapularis (Acari: Ixodidae) in residential and natural settings in a Lyme disease-endemic area in New Jersey.

We live-trapped small mammals and flagged vegetation within wooded natural and residential landscapes to examine how any observed differences in small mammal species composition may influence Ixodes scapularis Say burdens and the abundance of host-seeking ticks. Two years of live trapping showed that Eastern chipmunks, Tamias striatus, were captured with significantly greater frequency in some residential areas than white-footed mice, Peromyscus leucopus, whereas the proportion of white-footed mouse captures was higher or similar to chipmunk captures in the undeveloped natural areas. Both mice and chipmunks seemed to adapt well to managed residential landscapes, with residential sites yielding similar or significantly greater numbers of captures compared with undeveloped sites. In areas where chipmunk captures outnumbered mice, larval tick burdens on mice were either higher or no different than in areas where few or no chipmunks were captured, in contrast to previous studies suggesting that alternate hosts should reduce larval burdens on mice. Chipmunks apparently play an important role in the Lyme disease transmission cycle in these residential settings.

Animals↗
PubMed1978

Erythema chronicum migrans and lyme arthritis: field study of ticks.

Ticks were collected during 1977 in communities east of the Connecticut River where there was a high incidence of erythema chronicum migrans and Lyme arthritis and were compared with collections from a similar area 20 km west of the river where cases of the disease were rare. Ixodes scapularis was much more abundant on the east side than on the west. Immature I. scapularis were 13 times more abundant on white-footed mice (Peromyscus leucopus), and adult I. scapularis 16 times more abundant on white-tailed deer (Odocoileus virginianus) in the east than in the west communities. In addition, all active stages in the life cycle of this tick--larvae, nymphs, and adults--both males and females, were found on humans (mostly patients) in the east communities. Both nymphs and adults were abundant on dogs and cats in this area. Attempts to recover an etiologic agent from ticks were unsuccessful.

Animals↗
PubMedDate not supplied

Genetic variation of amylases in deer mice.

The inheritance of salivary amylase variants in the deer mouse, Peromyscus maniculatus, is controlled by codominant alleles, Amy-1a, Amy-1b, and Amy-1c, at a single autosomal locus. Pancreatic amylases were invariant and unaffected by salivary amylase genotypes. Salivary amylase zymograms of five myomorphic rodents are compared and evolutionary implications are discussed.

Amylases↗
PubMedDate not supplied

Juvenile ataxia--a new behavioral mutation in the deermouse.

An autosomal recessive behavioral mutation designated juvenile ataxia (ja) was first isolated from F2 progeny of four blonde (bl) Peromyscus maniculatus bairdi siblings. Juvenile ataxic homozygotes exhibit an ataxic gait without an associated tremor from 15 days postpartum. This ataxia continues but does not increase noticeably in severity until between 35 and 43 days of age. Thereafter, a rapid and dramatic improvement in the behavior pattern is seen, so that juvenile ataxic deermice over 45 days of age are phenotypically indistinguishable from wild type or heterozygotes of the same age. Female juvenile ataxic homozygotes rarely breed, while male homozygotes are fully fertile. Linkage tests between juvenile ataxia and blonde suggest that these two mutations are not allelic and are not tightly linked. Testing between juvenile ataxia and a previously described neurological mutant, boggler (bg), indicates that complementation between these two mutations is incomplete, and suggests that boggler and juvenile ataxic may represent allelic mutations.

Animals↗