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PubMed2003

Inability of a variant strain of Anaplasma phagocytophilum to infect mice.

Nymphal Ixodes scapularis ticks were collected from several sites in Rhode Island. Polymerase chain reaction and DNA sequencing were used to determine the presence and prevalence of Anaplasma phagocytophilum human agent (AP-ha) and a genetic variant not associated with human disease (AP-variant 1). The remaining ticks from each cohort were allowed to feed to repletion on either white-footed (Peromyscus leucopus) or DBA/2 (Mus musculus) mice. The engorged ticks and murine blood samples were evaluated for the presence of AP-ha and AP-variant 1. Although a high percentage of the infecting ticks harbored AP-variant 1, only AP-ha was amplified from the murine blood samples. Additional ticks were fed on immunocompromised SCID mice, and, again, only AP-ha was capable of establishing an infection, and only AP-ha could be detected by xenodiagnosis. These data suggest that AP-variant 1 cannot establish an infection in mice, and we propose that AP-variant 1 has an alternative natural reservoir, possibly white-tailed deer.

Anaplasma phagocytophilum↗
PubMed1998

Tissue distribution of hantavirus antigen in naturally infected humans and deer mice.

The Sin Nombre virus (SNV) is the etiologic agent of hantavirus pulmonary syndrome in humans but does not cause disease in chronically infected deer mice (Peromyscus maniculatus), the natural host. In this study, murine antiserum raised against recombinant SNV nucleocapsid protein was utilized to localize viral antigen immunohistochemically in tissues from both humans (n = 20; 11 positive, 9 negative) and deer mice (n = 6; 4 positive, 2 negative). Viral infection status was confirmed by Western blot or reverse transcriptase-polymerase chain reaction. SNV antigen was detected in pulmonary and cardiac endothelium in both species, but positive cells in deer mice were rare. Other deer mouse tissues, including kidney, were negative; in contrast, vascular elements of several tissues from infected humans were positive, with strong staining of renal endothelium. The paucity of positive cells in chronically infected mice suggests a low virus burden compared with that of acutely infected humans.

Animals↗
PubMed2001

Spatiotemporal variation in a Lyme disease host and vector: black-legged ticks on white-footed mice.

We monitored population density of white-footed mice (Peromyscus leucopus), burdens of immature black-legged ticks (Ixodes scapularis) on mice, and infection prevalence of host-seeking ticks on six forest plots in southeastern New York State from 1995 through 1999. Despite densities of mice that fluctuated two orders of magnitude, average larval and nymphal tick burdens per mouse remained remarkably constant. Spatial variability in mouse density and tick burdens was modest. The total number of larval and nymphal ticks that fed on the mouse population each year depended strongly on population density of mice; a steady increase was observed in both mouse density and total tick meals on mice from 1996 through 1999. The result was a steady increase in the infection prevalence of nymphal and adult ticks with the etiological agent of Lyme disease, Borrelia burgdorferi, over this time. We suggest that fluctuations in population density of mice, combined with possible regulation of tick burdens on mice, may influence risk of human exposure to Lyme disease.

Animals↗
PubMed2001

Interference between the agents of Lyme disease and human granulocytic ehrlichiosis in a natural reservoir host.

Agents of Lyme disease (Borrelia burgdorferi) and human granulocytic ehrlichiosis (Ehrlichia phagocytophila) are perpetuated in a natural cycle involving the black-legged tick (Ixodes scapularis) and its vertebrate hosts. Using I. scapularis nymphs as the mode of infectious challenge, we studied how infection with one pathogen in white-footed mice (Peromyscus leucopus) affects their ability to acquire the other agent and subsequently to infect larvae, which these agents would do in nature. Two groups of mice were infected with either B. burgdorferi or E. phagocytophila. One week later, B. burgdorferi-infected mice were challenged with E. phagocytophila, and E. phagocytophila-infected mice were challenged with B. burgdorferi. Simultaneously, two control groups of uninfected mice were infected with each agent from the same tick cohorts used on the first groups of mice. Uninfected I. scapularis larvae were fed on all mice for xenodiagnosis at weekly intervals lasting 2 months. For the B. burgdorferi challenge, all control and E. phagocytophila-infected mice acquired B. burgdorferi. However, fewer xenodiagnostic larvae acquired B. burgdorferi from mice with mixed infections compared with mice infected with B. burgdorferi only. For the E. phagocytophila challenge, all five control mice acquired E. phagocytophila, but only two of five mice infected with B. burgdorferi subsequently acquired E. phagocytophila. Consequently, mice with both infections produced fewer xenodiagnostic ticks infected with E. phagocytophila than mice infected with E. phagocytophila only. Thus, a primary infection with either B. burgdorferi or E. phagocytophila in mice inhibited transmission of a second agent, suggesting interference between these two agents.

Anaplasma phagocytophilum↗
PubMed2001

A relapsing fever group spirochete transmitted by Ixodes scapularis ticks.

A species of Borrelia spirochetes previously unknown from North America has been found to be transmitted by Ixodes scapularis ticks. Infected ticks are positive for Borrelia spp. by DFA test but negative for Borrelia burgdorferi by polymerase chain reaction (PCR) using species-specific primers for 16S rDNA, outer surface protein A, outer surface protein C, and flagellin genes. A 1,347-bp portion of 16S rDNA was amplified from a pool of infected nymphs, sequenced, and compared with the homologous fragment from 26 other species of Borrelia. The analysis showed 4.6% pairwise difference from B. burgdorferi, with the closest relative being Borrelia miyamotoi (99.3% similarity) reported from Ixodes persulcatus in Japan. Phylogenetic analysis showed the unknown Borrelia to cluster with relapsing fever group spirochetes rather than with Lyme disease spirochetes. A 764-bp fragment of the flagellin gene was also compared with the homologous fragment from 24 other Borrelia species. The flagellin sequence of B. burgdorferi was 19.5% different from the unknown Borrelia and showed 98.6% similarity with B. miyamotoi. A pair of PCR primers specifically designed to amplify a 219-bp fragment of the flagellin gene from this spirochete was used to survey field-collected I. scapularis nymphs from five northeastern states (Connecticut, Rhode Island, New York, New Jersey, and Maryland). Positive results were obtained in 1.9-2.5% of 712 nymphs sampled from four states but in none of 162 ticks collected from Maryland. Transovarial transmission was demonstrated by PCR of larval progeny from infected females with filial infection rates ranging from 6% to 73%. Transstadial passage occurred from larvae through adults. Vertebrate infection was demonstrated by feeding infected nymphs on Peromyscus leucopus mice and recovering the organism from uninfected xenodiagnostic larvae fed 7-21 days later. Considering the frequency of contact between I. scapularis and humans, further work is needed to determine the potential public health significance of yet another zoonotic agent transmitted by this tick species.

Animals↗
PubMed2006

A reverse transcriptase-polymerase chain reaction assay of Borrelia burgdorferi 16S rRNA for highly sensitive quantification of pathogen load in a vector.

We developed a real-time quantitative detection assay for the pathogen Borrelia burgdorferi, a Lyme borreliosis (LB) agent, using reverse transcription-polymerase chain reaction (RT-PCR) with primers and probe for a Borrelia genus-specific region of 16S ribosomal RNA. The standard curve of the assay was linear by semi-log plot over more than five orders of magnitude, and the detection limit of the assay was one thousandth of a single cell of B. burgdorferi. The minimum target level for detection using the RT-PCR assay for 16S RNA was 40-fold lower than the RT-PCR assay for messenger RNA of ospA, a highly expressed, plasmid-borne gene, and 1600-fold lower than the RT-PCR assay for messenger RNA of p66, a chromosome-borne gene of B. burgdorferi. The 16S rRNA assay was then applied in an experimental setting for monitoring the spirochetal load in B. burgdorferi-infected Ixodes scapularis ticks before and after they fed on Peromyscus leucopus mice immunized with recombinant OspA. Unfed infected ticks had a mean of 2,240 spirochetes per tick, and after feeding on non-immunized mice and engorgement, the mean number of spirochetes increased to 223,900 per tick. In contrast, there were either no or <or=7 spirochetes in ticks that had fed on OspA-immunized mice.

Animals↗
PubMed1982

An assessment of "hidden" heterogeneity within electromorphs at three enzyme loci in deer mice.

Allelic heterogeneity within protein electromorphs at three loci was examined in populations of deer mice (Peromyscus maniculatus) collected from five localities across North America. We used a variety of electrophoretic techniques (including several starch and acrylamide conditions, gel-sieving, and isoelectric focusing) plus heat denaturation. Of particular interest was the supernatant glutamate oxalate transaminase system (GOT-1; aspartate aminotransferase-1 of some authors), which under standard electrophoretic conditions had been shown to exhibit basically a two-allele polymorphism throughout the range of maniculatus. The use of all of the above techniques failed to uncover any additional variation for GOT-1 in these populations. Similarly, no new scorable variation was resolved at the essentially monomorphic malate dehydrogenase-1 locus by additional conditions of electrophoresis. In marked contrast to the results for the above two enzymes, the use of multiple conditions of electrophoresis resolved the 8 standard-condition electromorphs of esterase-1 into a total of 23 variants showing strong geographic differentiation in frequency. These 23 electromorphs were further divided into a total of 35 variants by thermal stability studies. However, the allelic nature of all of the thermal stability esterase variants remains to be documented. The results of this study, taken together with the remarkable geographic heterogeneity for this species in ecology, morphology, karyotype and mitochondrial DNA sequence, suggest that some form of balancing selection may be acting to maintain the GOT-1 polymorphism.

Animals↗
PubMed2001

An ancient retrovirus-like element contains hot spots for SINE insertion.

Vertebrate retrotransposons have been used extensively for phylogenetic analyses and studies of molecular evolution. Information can be obtained from specific inserts either by comparing sequence differences that have accumulated over time in orthologous copies of that insert or by determining the presence or absence of that specific element at a particular site. The presence of specific copies has been deemed to be an essentially homoplasy-free phylogenetic character because the probability of multiple independent insertions into any one site has been believed to be nil. Mys elements are a type of LTR-containing retrotransposon present in Sigmodontine rodents. In this study we have shown that one particular insert, mys-9, is an extremely old insert present in multiple species of the genus Peromyscus. We have found that different copies of this insert show a surprising range of sizes, due primarily to a continuing series of SINE (short interspersed element) insertions into this locus. We have identified two hot spots for SINE insertion within mys-9 and at each hot spot have found that two independent SINE insertions have occurred at identical sites. These results have major repercussions for phylogenetic analyses based on SINE insertions, indicating the need for caution when one concludes that the existence of a SINE at a specific locus in multiple individuals is indicative of common ancestry. Although independent insertions at the same locus may be rare, SINE insertions are not homoplasy-free phylogenetic markers.

Alleles↗
PubMed1993

Comparison of the lateral diffusion constant of hepatocyte membrane proteins in two wild mouse strains of considerably different longevity: FRAP studies on liver smears.

The liver cells of male and female wild mice (Peromyscus leucopus and Mus musculus) have been studied in young, adult, and old age groups. Because P. leucopus displays a life expectancy of 7-8 years, the age groups of this strain were from 5.5 to 68 months. M. musculus survives only to about 2.5 years; therefore, the age groups of this strain ranged from 6 to 27 months. Protein lateral diffusion in hepatocyte membranes was measured by means of fluorescence recovery after photobleaching (FRAP) in liver smears. The peroxide-induced autofluorescence was utilized as a fluorescent label, which in H2O2 treated liver smears is caused by the oxidation of riboflavin bound uniformly to all proteins of the cell membrane. This way the average lateral diffusion constant (D) and the fractional recovery of those proteins can be measured. In both males and females of both strains D displayed a negative linear age correlation. Intraspecies sex differences were small and statistically insignificant. However, interspecies comparisons of males or females resulted in a strongly significant difference: although the intercept points of the regression lines describing D were identical in both strains (3.1 x 10(-10) cm2/sec), the decay of D with aging was about 2.5 times faster in the short-living M. musculus than in the long-living P. leucopus. By the end of life expectancy, both strains reached practically identical values (about 1.9 x 10(-10) cm2/sec). The results lend further support to the membrane hypothesis of aging.

Aging↗
PubMed1994

Discovery of an enzootic cycle of Borrelia burgdorferi in Neotoma mexicana and Ixodes spinipalpis from northern Colorado, an area where Lyme disease is nonendemic.

An intensive enzootic cycle of Borrelia burgdorferi was seen in populations of the Mexican wood rat, Neotoma mexicana, and Ixodes spinipalpis ticks in northern Colorado. Cultures of rodent ear tissue and ticks yielded 63 spirochetal isolates: 38 N. mexicana, 2 Peromyscus difficilis, and 23 I. spinipalpis. All 63 isolates were identified as B. burgdorferi sensu lato by polymerase chain reaction; a representative subset was characterized as B. burgdorferi by SDS-PAGE and immunoblotting. A tick-derived spirochete isolate was infectious to laboratory mice and I. scapularis, the principal vector of Lyme disease in endemic areas of the United States. The risk of human contact with infected I. spinipalpis appears to be minimal from this epidemiologically silent focus in northern Colorado, since this tick is restricted to wood rat nests in this semiarid environment.

Animals↗
PubMed1990

Consumption and mortality of the white-footed mouse (Rodentia: Muridae) and Ord's kangaroo rat (Rodentia: Heteromyidae) when fed carbaryl-bran grasshopper (Orthoptera) bait.

Two species of wild rodents (Ord's kangaroo rat, Dipodomys ordii Woodhouse, and the white-footed mouse, Peromyscus leucopus Rafinesque) were fed 0, 2, and 20% (AI) by weight concentrations of carbaryl-bran grasshopper bait in the laboratory to determine whether the bait would be consumed, the total quantity of bait consumed within a specified period, whether mortality would occur, and whether bait would be consumed if other foods were readily available. Consumption tests showed that bait ingestion was inversely proportional to concentration. No mortalities occurred at the 0% level, whereas the 2 and 20% concentration treatments resulted in 18.8 and 97.0% mortality, respectively. The apparent repellency of 20% bait indicated that starvation may have caused the deaths. Food preference tests disclosed that D. ordii and P. leucopus preferred natural forage rather than treated and untreated wheat bran in the laboratory.

Animals↗
PubMed1990

Intrinsic competence of three ixodid ticks (Acari) as vectors of the Lyme disease spirochete.

We compared the intrinsic vector competence of Ixodes dammini Spielman et al., Dermacentor variabilis (Say), and Amblyomma americanum (L.) for the Lyme disease spirochete (Borrelia burgdorferi Johnson et al.) on Prudence Island, Rhode Island, a Lyme disease-endemic site where all three ticks occur together. Natural and experimental spirochete infection rates were determined in those ticks and their degree of contact with white-footed mice (Peromyscus leucopus), the principal reservoir host, was compared. Host-seeking nymphal and adult I. dammini and A. americanum, collected by flagging, were nearly equally abundant, as were adult D. variabilis, but only I. dammini were infected with B. burgdorferi. Larvae and nymphs of both I. dammini and D. variabilis were found infesting mice, but A. americanum never were found on this host. Furthermore, although larvae of all three tick species became infected by ingesting spirochetes while feeding on experimentally infected mice, only I. dammini remained infected following the transstadial molt. These findings suggest that of these three tick species, only I. dammini is competent as a vector of the Lyme disease spirochete.

Animals↗
PubMed1991

Evaluation of host-targeted acaricide for reducing risk of Lyme disease in southern New York state.

A 2-yr evaluation of a commercial product designed to reduce the risk of Lyme disease by delivering permethrin-treated cotton to white-footed mice (Peromyscus leucopus) was conducted at three sites in Westchester County, N.Y., an area where Lyme disease is endemic. We examined the numbers of host-seeking nymphal Ixodes dammini Spielman, Clifford, Piesman & Corwin, the numbers of larval I. dammini infesting mice, and the proportion of nymphs infected with Borrelia burgdorferi, the causative agent of Lyme disease. The density of nymphs collected by drag sampling did not differ between treatment and control areas in the first year for either a woodland or recreational site. In the second year, no significant decrease in the density of nymphs was observed in the treatment areas compared with the control areas. Numbers of larvae on 67 mice captured on treatment and control grids did not differ for woodland and recreational sites, but significantly fewer larvae were found on mice captured at the residential treatment site. The percentage of host-seeking ticks infected with spirochetes did not differ between treatment and control sites in any habitat for either year. The use of permethrin-treated cotton did not measurably reduce the numbers of I. dammini or the proportion of ticks infected with spirochetes at our study sites.

Animals↗
PubMed1991

Effectiveness of host-targeted permethrin in the control of Ixodes dammini (Acari: Ixodidae)

Tubes of commercially available permethrin-treated cotton balls were distributed twice each year in 1989 and 1990 at five sites in a Lyme disease endemic area in Connecticut. Five additional sites were not treated. At each application, 48 tubes, sufficient to treat 0.4 ha, were dispersed at 10-m intervals through woodlands, around ornamental plantings, and along rockwalls. The cotton was collected by white-footed mice (Peromyscus leucopus) from the majority of the tubes, which resulted in a decrease (37.2% in 1989 and 91.5% in 1990) in the number of subadult Ixodes dammini Spielman, Clifford, Piesman, and Corwin on the mice in the treated areas. There were no significant decreases in the number of host-seeking nymphs or adults of I. dammini in 1989 or 1990 between the treated and untreated sites. The rates of infection in the host-seeking nymphs with Borrelia burgdorferi, the etiological agent of Lyme disease, at the treated sites (13.0 and 14.6% for 1989 and 1990, respectively) were comparable to those at the untreated sites (16.9 and 13.2% for 1989 and 1990, respectively). The distribution of permethrin-treated cotton around individual residences significantly reduced the number of ticks on P. leucopus but was not sufficient to reduce the risk of exposure to infected host-seeking nymphs and adults of I. dammini after two seasons of treatment.

Animals↗
PubMed1991

Effectiveness of selected granular acaricide formulations in suppressing populations of Ixodes dammini (Acari: Ixodidae): short-term control of nymphs and larvae.

Applications of selected granular acaricide formulations to the shrub layer of forested habitats during the peak activity periods of Ixodes dammini Spielman, Clifford, Piesman & Corwin nymphs and larvae significantly reduced the abundance of these stages on Peromyscus leucopus. The granules effectively penetrated growing vegetation and suppressed populations of subadult ticks questing in the leaf litter. The use of granular acaricide formulations provides the only documented method of control of free-living I. dammini nymphs and larvae in dense vegetation. As such, this technique will serve as a major component of any integrated control program against this vector tick species.

Animals↗
PubMed1991

Efficacy of a permethrin-based acaricide to reduce the abundance of Ixodes dammini (Acari: Ixodidae).

Permethrin-impregnated cotton was distributed to reduce abundance of immature Ixodes dammini Spielman, Clifford, Piesman & Corwin feeding upon white-footed mice (Peromyscus leucopus) and questing on vegetation at a private resort site (The Crane Reservation of The Trustees of Reservations in Ipswich, Mass.) located in coastal New England. This test constituted the first independent evaluation of the efficacy of this commercial product (Damminix). Over a 3-yr period, 2,000 applicator tubes containing treated cotton were distributed over the 7.3-ha site in 5 regularly scheduled applications. Mice removed treated fiber from the tubes and transported it to their nests. Within 3 wk of the first application, virtually all mice in the treated site were rendered free of ectoparasites. After the first season of application, no nymphal host-seeking I. dammini could be found on vegetation. Visitor and employee complaints about deer tick bites or ticks found on skin and clothing had been attributed to the site before treatment, but not thereafter. We confirmed the efficacy of Damminix for reduction of the abundance of vector ticks and thereby contributed to the protection of humans against Lyme disease at this site.

Animals↗
PubMed1992

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.

Animals↗
PubMed1992

Third-year evaluation of host-targeted permethrin for the control of Ixodes dammini (Acari: Ixodidae) in southeastern Connecticut.

The impact of commercially available permethrin-treated cotton balls targeted at Ixodes dammini Spielman, Clifford, Piesman & Corwin on white-footed mice, Peromyscus leucopus, was evaluated for a third year at five residential sites in south-central Connecticut. Each site had been treated twice each year from 1989 through 1991 with sufficient product to treat 0.4 ha of mouse habitat, and results were compared with five untreated sites. There were no significant differences in the number of host-seeking nymphs or adults of I. dammini, the vector of the Lyme disease spirochete, Borrelia burgdorferi, in 1991 between the treated and untreated sites. The rate of infection in host-seeking nymphs by B. burgdorferi at the treated sites (15.3% of 600) was comparable with that at the untreated sites (16.5% of 454). Only 16.3% of 86 P. leucopus captured at the treated sites were infested with I. dammini subadults compared with 66.9% of 118 from the mice at the untreated sites. The impact of permethrin-treated cotton during the third year of treatment was similar to that observed for the first 2 yr and did not reduce the risk of exposure to spirochete-infected, host-seeking nymphs and adults of I. dammini.

Animals↗