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PubMed2004

Transmission route efficacy and kinetics of Anaplasma phagocytophilum infection in white-footed mouse, Peromyscus leucopus.

Anaplasma phagocytophilum was used to infect Peromyscus leucopus mice by three routes of inoculation: infected tick infestation and intraperitoneal (IP) and subcutaneous (SQ) injection of infected tissue culture cells. A set of 12 mice were infected (four tick, four IP, and four SQ), and blood was drawn at 1, 3, 6, 9, 12, 15, 21, 28, 35, and 60 days post-infection and analyzed by use of a quantitative PCR assay to assess the level of infection. An additional set of 108 mice were infected (36 tick, 36 IP, 36 SQ) and euthanized at 1, 3, 6, 9, 12, 15, 21, 28, and 35 days post-infection (four mice/time point), and blood, spleen, bone marrow, and bladder tissue samples were analyzed. Tick infection generally produced the highest average levels of infection and peaked at 9 days post-infestation in blood, spleen, and bone marrow and at 6 days after infestation in the bladder. IP injection resulted in levels of infection that peaked on day 6 (spleen) or 12 (bladder, bone marrow, and blood). A. phagocytophilum injected SQ showed low levels of infection, and the day of peak infection varied. The average level of infection in the blood drawstressed mice was consistently higher and peaked earlier than infection in the non-stressed, euthanized mice. Xenodiagnosis was used to assay a third set of 12 mice (four tick, four IP, and four SQ) on days 7 and 14 post-infection and ticks fed on tick-infected mice showed the highest rate of PCR-positive test results at both time points (day 7, 22.2%; day 14, 17.3%). These data indicate that P. leucopus mice can be infected by tick infestation, IP injection, or SQ injection but that the kinetics and level of infection are quite variable among individual mice, may be influenced by the route of inoculation, and may be further altered by common laboratory procedures such as repeated collection of blood samples.

Anaplasma phagocytophilum↗
PubMed2005

A preliminary study of the patterns of Sin Nombre viral infection and shedding in naturally infected deer mice (Peromyscus maniculatus).

Deer mice (Peromyscus maniculatus) were trapped in southern Manitoba, Canada and tested for evidence of Sin Nombre virus infection. Viral genome was amplified from tissues as well as saliva/oropharyngeal fluid, and urine samples were collected from seropositive animals. Detection of viral RNA in tissue samples and excreta/secreta from mice suggest that differences may exist between naturally infected rodents with respect to viral shedding.

Animals↗
PubMed1978

Genetics of hemoglobin in the deer mouse, Peromyscus maniculatus. I. Multiple alpha- and beta-globin structural loci.

Genetic data, together with molecular structure studies, have demonstrated that the complex hemoglobin phenotypes in four subspecies of P. maniculatus are generated by at least four, and probably five, globin structural loci. The Hba and Hbc loci apparently arose by duplication of an ancestral alpha-type locus, while Hbb, Hbd, and Hbe apparently were derived from a beta-type locus. The Hba and Hbb structural loci are electrophoretically monomorphic, while Hbc, Hbd, and Hbe are each polymorphic for at least two electrophoretic alleles. Alleles at Hbc and Hbd segregate independently. The globin products of Hbc and Hbd are electrophoretically indistinguishable; therefore, it is impossible to enumerate true gene frequencies in population surveys. Combined evidence from Peromyscus, Mus and Rattus indicates a remarkable similarity in the numbers of duplicated globin structural loci and in their linkage relationships to coat color loci.

Animals↗
PubMed1978

Genetics of hemoglobin in the deer mouse, Peromyscus maniculatus. II. Multiple alleles at regulatory loci.

Deer mice are polymorphic for electrophoretic hemoglobin phenotypes showing one, two, or three bands. Within the multibanded phenotypes, there is considerable variation in the hemoglobin partitioning, defined as the fraction of total hemoglobin made up by the secondary and tertiary bands. In subspecies sonoriensis, for example, hemoglobin partitionings range from 0.03 to 0.38. The inheritance of partitioning values is under remarkably strict genetic control. The genetic variation is additive and the narrow heritability is close to 1.0. The inheritance data can be modeled in precise detail by postulating multiple-allele polymorphisms at globin regulatory loci. Comparison of simulated versus actual inheritance data demonstrates that the so-called null structural alleles actually produce functional globins.--The genetic controls in Peromyscus may be analogous to those in primates. Unfortunately, the molecular mechanisms effecting the regulation are unknown. Different subspecies of P. maniculatus show strikingly different arrays of partitioning values, but the role of natural selection in maintaining the quantitative polymorphisms remains obscure.

Alleles↗
PubMed1979

The use of restriction endonucleases to measure mitochondrial DNA sequence relatedness in natural populations. I. Population structure and evolution in the genus Peromyscus.

In this study we introduce to natural population analysis a molecular technique that involves the use of restriction endonucleases to compare mitochondrial DNA (mtDNA) sequences. We have examined the fragment patterns produced by six restriction endonucleases acting upon mtDNA isolated from 23 samples of three species of the rodent Peromyscus. Our observations confirm the following conclusions derived from previous experiments with laboratory animals: (1) mtDNA within an individual homogeneous; (2) at least the majority of mtDNA present in an individual is inherited from the female parent. Our experiments demonstrate for the first time that there is detectable heterogeneity in mtDNA sequences within and among natural geographic populations of a species and that this heterogeneity can readily be used to estimate relatedness between individuals and populations. Individuals collected within a single locale show less than 0.5% sequence divergence, while those collected from conspecific populations separated by 50 ti 500 miles differ by approximately 1.5%. The mtDNAs of the closely related sibling species P. polionotus and P. maniculatus differ from each other by 13 to 17%; nonsibling species differ by more than 20%. Qualitative and quantitative approaches to analysis of digestion patterns are suggested. The results indicate that restriction analysis of mtNDA may become the most sensitive and powerful technique yet available for reconstructing evolutionary relationships among conspecific organisms.

Animals↗
PubMed1980

Differential rates of aging in natural populations of old-field mice (Peromyscus polionotus).

Lipofuscin accumulation in cerebellar Purkinje cells was studied in two natural populations of old-field mice (Peromyscus polionotus). Chronological age was estimated by assaying water-insoluble proteins in the eye lens. The number of fluorescent lipofuscin granules per cell was used as an index of physiological age. In both populations, lipofuscin accumulation began at an age of about two months and increased linearly thereafter until the maximum age included in the study (322 days). Sex did not significantly affect the rate of accumulation in either population. The populations did differ in their rates of aging, however. The population with faster rate of lipofuscin accumulation had higher reproductive effort and/or greater adult mortality, and lived in poorer quality habitat. Although genetic influences cannot be discounted, environmental factors were probably responsible for differences in rates of lipofuscin accumulation.

Aging↗
PubMed2004

Top-down approaches to the study of natural variation in complex physiological pathways using the white-footed mouse (Peromyscus leucopus) as a model.

Variation in complex physiological pathways has important effects on human function and medical treatment. Complex pathways involve cells at multiple locations, which serve different functions regulated by many genes and include complex neuroendocrine pathways that regulate physiological function. One of two competing hypotheses regarding the effects of selection on complex pathways predicts that variability should be common within complex pathways. If this hypothesis is correct, then we should expect wide variation in neuroendocrine function to be typical within natural populations. To test this hypothesis, a complex neuroendocrine pathway that regulates photoperiod-dependent changes in fertility in a natural population of white-footed mice (Peromyscus leucopus) was used to test for natural genetic variability in multiple components of the pathway. After testing only six elements in the photoperiod pathway in P. leucopus, genetic variation in the following four of these elements was evident: the circadian clock, melatonin receptor abundance or affinity, sensitivity of the reproductive axis to steroid negative feedback, and gonadotropin-releasing hormone neuronal activity. If this result can be extended to humans, the prediction would be that significant variation at multiple loci in complex neuroendocrine pathways is common among humans, and that variation would exist even in human populations from a common genetic background. This finding could only be drawn from an "exotic" animal model derived from a natural source population, confirming the continuing importance of nontraditional models alongside the standard laboratory species.

Animal Husbandry↗
PubMed1991

Absence of transplacental transmission of Lyme disease spirochetes from reservoir mice (Peromyscus leucopus) to their offspring.

Lyme disease spirochetes (Borrelia burgdorferi) are naturally maintained in an enzootic cycle mainly by vector ticks (Ixodes dammini) infesting white-footed mice (Peromyscus leucopus). Suggestions that mice may become infected without exposure to ticks prompted a study to evaluate whether mice could transmit spirochetes transplacentally to their offspring. Mice were live-captured in two Massachusetts sites where Lyme disease spirochetes are intensely enzootic. Pregnant females were housed separately in the laboratory through delivery, and mothers and their offspring were caged together until weaning. Each female and two offspring were then examined for evidence of infection serologically and by tick xenodiagnosis. All 14 mother mice examined produced infected ticks and exhibited serum antibodies to B. burgdorferi. However, none of 28 offspring tested produced infected ticks and only a few had evidence of circulating antibody. In a separate experiment, no young CD-1 mice, born of infected mothers, had IgM antibody to B. burgdorferi. It would appear that immature mice are not transplacentally infected with spirochetes and must be exposed to infected ticks before becoming infected and infective themselves.

Animals↗
PubMed1994

Serologic and genetic identification of Peromyscus maniculatus as the primary rodent reservoir for a new hantavirus in the southwestern United States.

An outbreak of hantavirus pulmonary syndrome (HPS) in the southwestern United States was etiologically linked to a newly recognized hantavirus. Knowledge that hantaviruses are maintained in rodent reservoirs stimulated a field and laboratory investigation of 1696 small mammals of 31 species. The most commonly captured rodent, the deer mouse (Peromyscus maniculatus), had the highest antibody prevalence (30%) to four hantavirus antigens. Antibody also was detected in 10 other species of rodent and in 1 species of rabbit. Reverse transcriptase-polymerase chain reaction (RT-PCR) products of hantavirus from rodent tissues were indistinguishable from those from human HPS patients. More than 96% of the seropositive P. maniculatus were positive by RT-PCR, suggesting chronic infection. Antibody prevalences were similar among P. maniculatus trapped from Arizona (33%), New Mexico (29%), and Colorado (29%). The numeric dominance of P. maniculatus, the high prevalence of antibody, and the RT-PCR findings implicate this species as the primary rodent reservoir for a new hantavirus in the southwestern United States.

Animals↗
PubMed1994

Detection of Borrelia burgdorferi DNA in museum specimens of Peromyscus leucopus.

To determine whether Borrelia burgdorferi was enzootic within the United States at the beginning of the 20th century, ear skin samples taken from museum specimens of the white-footed mouse (Peromyscus leucopus) were examined for evidence of spirochetal DNA. In total, 280 samples from mice collected between 1870 and 1919 were analyzed by a nested polymerase chain reaction protocol. Of these, 2 specimens from the vicinity of Dennis, Massachusetts, during 1894 were reproducibly positive for B. burgdorferi OspA sequences. The remaining 278, representing both currently endemic and nonendemic sites, were negative for spirochetal DNA. These studies suggest that the agent of Lyme disease was present in a suitable reservoir host in the United States before the turn of the century and provide evidence against a hypothesis of recent introduction of this zoonotic agent to North America.

Animals↗
PubMed1995

Analysis of Borrelia burgdorferi sequentially isolated from Peromyscus leucopus captured at a Lyme disease enzootic site.

Thirty isolates of Borrelia burgdorferi sequentially cultured from 15 naturally infected white-footed mice (Peromyscus leucopus) were examined for variability in protein and plasmid profiles. Heterogeneity was detected in OspB and OspC and in proteins between 18.0 and 28.0 kDa by PAGE. Plasmid profiles were heterogeneous in the first isolate from 11 mice (73%) and between the first and last sequential isolate from 13 mice (87%). Comparison of the first and last isolates showed increased expression of OspC in 6 mice (40%) and was associated in each case with a shift in mobility of a 16.0-kb plasmid, suggesting that regulatory elements of ospC may reside on this plasmid. Hybridization studies suggested that individual mice may have been infected by a heterogeneous population of spirochetes and that changes in the protein and plasmid profiles between the first and last sequential isolates from some mice may have been the result of clonal selection.

Animals↗
PubMed1993

Competence of Peromyscus maniculatus (Rodentia: Cricetidae) as a reservoir host for Borrelia burgdorferi (Spirochaetares: Spirochaetaceae) in the wild.

Although capable of maintaining and transmitting Borrelia burgdorferi Johnson, Schmidt, Hyde, Steigerwalt & Brenner, the causative spirochete of Lyme disease, in the laboratory, the specific ability of deer mice, Peromyscus maniculatus Le Conte, to support this zoonosis has not been established. Demonstration that P. maniculatus is a competent reservoir host in the wild would indicate that the spread of Lyme disease is not limited to the range of the primary reservoir host, P. leucopus Rafinesque. Isle au Haut, an offshore Maine island upon which the vector tick Ixodes dammini Spielman, Clifford, Piesman & Corwin has become established, supports an isolated population of mice that are exclusively P. maniculatus. We examined the reservoir competence of this species by comparing infection rates of B. burgdorferi among juvenile ticks removed from livetrapped mice on this island with those removed from P. leucopus obtained at a mainland site endemic for Lyme disease. Equivalent rates of infection among engorged larval ticks, survival of infection through the larval-nymphal molt, and the isolation of B. burgdorferi from mice at both sites attest to the reservoir competence of P. maniculatus.

Animals↗
PubMed1996

Borrelia burgdorferi-infected Ixodes scapularis (Acari: Ixodidae) and Peromyscus leucopus in northeastern Wisconsin.

Populations of the blacklegged tick, Ixodes scapularis Say, are established in western and central Wisconsin in the upper midwestern United States, but appear to be expanding geographically there. Here, we report a previously unknown population in northeastern Wisconsin. Questing I. scapularis nymphs and adults were collected by flagging vegetation from a riverine site in Marinette County, Wisconsin, in spring of 1993 and 1994. Dissection and culture of tick guts in modified Barbour-Stoenner-Kelley II medium showed that some of the ticks were infected with Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwald & Brenner, causative agent of Lyme disease. Fifteen of 30 white-footed mice, Peromyscus leucopus (Rafinesque), live-trapped at the site on 23-24 August 1994 were infested with immature I. scapularis, and ear-punch biopsies yielded B. burgdorferi cultures from 2 of the mice. However, none of 50 white-tailed deer, Odocoileus virginianus (Zimmermann), shot by hunters in Marinette County in November 1994 had I. scapularis on them, probably because no deer were shot at the same site where the tick population is located. These findings document existence of an established population of I. scapularis and a focus of Lyme disease in northeastern Wisconsin.

Animals↗
PubMed1996

Field estimates of numbers of Ixodes scapularis (Acari:Ixodidae) larvae and nymphs per hectare successfully feeding on Peromyscus leucopus in Massachusetts.

The numbers of blacklegged tick, Ixodes scapularis Say, per hectare that engorged as larvae and nymphs on white-footed mice, Peromyscus leucopus (Rafinesque), were estimated at 3 sites in coastal Massachusetts. Estimates of numbers of engorged ticks dropping per day from trapped mice were multiplied by mark-recapture estimates of the density (numbers per hectare) of white-footed mice to estimate numbers of ticks engorging on mice per hectare. In 1991, estimates of seasonal totals per hectare of I. scapularis nymphs completing blood meals on P.leucopus ranged from 825 +/- 68 at Nonamesset to 6,654 +/- 770 at Menemsha. This absolute sampling method (the drop-off method) was compared with drag sampling for nymphal ticks. Per hectare estimation of engorgement rates overcomes a shortcoming associated with drag sampling because site-to-site comparisons can be made even where vegetation structure differs markedly among sites. The drop-off method may be used to quantify the contribution of any host to the engorged tick population, provided sufficient such hosts can be collected on a weekly basis.

Animals↗
PubMed1997

Parasites of mammals on the Sevilleta National Wildlife Refuge, Socorro, New Mexico: Cuterebra austeni and C. neomexicana (Diptera:Oestridae) from Neotoma and Peromyscus (Rodentia:Muridae), 1991-1994.

In total, 6,486 rodents representing 3 families (Muridae, Heteromyidae, and Sciuridae) and 24 species were trapped May through August of 1991 through 1994. Of these, only the white-throated woodrat. Neotoma albigula Hartley; piñon mouse, Peromyscus truei Shufeldt; and white-footed mouse, P. leucopus Rafinesque, were infested with Cuterebra Clark larvae. Of the 594 N. albigula that were captured 103 (17.3%) were infested with 139 Cuterebra larvae with all infestations occurring in the throat region. N. albigula infestations were observed in 4 of 5 habitats sampled. The highest prevalence of infestation occurred during May-June (27.2%) versus July-August (9.1%) and in males (25.2%) versus females (18.3%). Prevalence of infestation was not significantly different between animals from the mark-release webs versus removal webs or adults versus juveniles. Also, there was no correlation between relative density of N. albigula and prevalence of infestation. Fifteen adults were reared from puparia and identified as C. austeni Sabrosky. Of 716 P. truei captured, 22 (3.1%) were infested with a total of 25 Cuterebra larvae with all infestations occurring in the scapular region. Although P. truei were captured in all 5 habitats, they were only infested in the piñon-juniper habitat: the highest prevalence of infestation occurred during July-August (10.9%) versus May-June (3.3%). Prevalence of infestation was not significantly different between animals from mark-release webs versus removal webs, males versus females, or adults versus juveniles. As in the N. albigula, there was no correlation between relative density of P. truei and prevalence of infestation. The adult reared from a puparium was identified as C. neomexicana Sabrosky. Of the 310 P. leucopus captured, only 3 (1%) were infested with Cuterebra larvae.

Animals↗
PubMed2006

Adaptive evolution of fertilization proteins within a genus: variation in ZP2 and ZP3 in deer mice (Peromyscus).

Rapid evolution of reproductive proteins has been documented in a wide variety of taxa. In internally fertilized species, knowledge about the evolutionary dynamics of these proteins between closely related taxa is primarily limited to accessory gland proteins in the semen of Drosophila. Investigation of additional taxa and functional classes of proteins is necessary in order to determine if there is a general pattern of adaptive evolution of reproductive proteins between recently diverged species. We performed an evolutionary analysis of 2 egg coat proteins, ZP2 and ZP3, in 15 species of deer mice (genus Peromyscus). Both of these proteins are involved in egg-sperm binding, a critical step in maintaining species-specific fertilization. Here, we show that Zp2 and Zp3 gene trees are not consistent with trees based on nonreproductive genes, Mc1r and Lcat, where species formed monophyletic clades. In fact, for both of the reproductive genes, intraspecific amino acid variation was extensive and alleles were sometimes shared across species. We document positive selection acting on ZP2 and ZP3 and identify specific amino acid sites that are likely targets of selection using both maximum likelihood approaches and patterns of parallel amino acid change. In ZP3, positively selected sites are clustered in and around the region implicated in sperm binding in Mus, suggesting changes may impact egg-sperm binding and fertilization potential. Finally, we identify lineages with significantly elevated rates of amino acid substitution using a Bayesian mapping approach. These findings demonstrate that the pattern of adaptive reproductive protein evolution found at higher taxonomic levels can be documented between closely related mammalian species, where reproductive isolation has evolved recently.

Adaptation, Biological↗
PubMedDate not supplied

Coat color genetics of Peromyscus: V. California blonde, a new recessive mutation in the deer mouse.

California blonde is a coat color mutation in the deer mouse (Peromyscus maniculatus) discovered among descendants of wild-type animals collected on Santa Cruz Island, California. The phenotype is produced by the presence of brown, rather than black, eumelanin in the pelage and skin. Retinal pigmentation is also reduced. The condition is inherited as an autosomal recessive trait. The California blonde gene is nonallelic with the brown (b), blonde (bln), and platinum (plt) mutant genes in this species. California blonde represents a newly detected genetic locus in the deer mouse. The symbol cfb is provisionally assigned for this genetic locus.

Animals↗
PubMedDate not supplied

Cataract--webbed Peromyscus. I. Genetics of cataract in P. maniculatus.

Cataract--webbed (cw) in the deer mouse (Peromyscus maniculatus) is a recessive mutant that is manifested by syndactyly (involving soft tissues) and eye defects including cataract. Within cw/cw mice, the age at which cataract first appears is genetically controlled. Evidence for the activity of genetic modifiers is the early appearance of cataracts in the offspring of parents that developed cataracts at early ages.

Animals↗