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PubMed1997

A small-scale survey of hantavirus in mammals from Indiana.

In order to determine if hantaviruses were present in mice and other small mammals in Indiana (USA), small mammals were trapped in Brown, LaPorte, Tippecanoe and Whitley counties. Sixty-seven small mammals were trapped during August and September 1994. Sixty-three Peromyscus leucopus, one Microtus pennsylvanicus, one Zapus hudsonius and two Blarina brevicauda were captured and tested for hantaviruses. Six P. leucopus were found to have antibody to Sin Nombre virus (SN) by IgG ELISA, and a 139 bp fragment of SN-like hantavirus was amplified from five of them. All six of the positive P. leucopus were from LaPorte County. No other small mammals had evidence of infection with SN virus. This study presents the first report of Sin Nombre-like hantavirus in P. leucopus from Indiana.

Animals↗
PubMed1998

Retrospective serosurvey for human granulocytic ehrlichiosis agent in urban white-footed mice from Maryland.

Archived serum samples from 111 Peromyscus leucopus, collected 1984-88 in Baltimore City (Maryland, USA), were analyzed by indirect immunofluorescence assay. Sera from two (2%) individuals contained antibodies reactive to Ehrlichia equi and the human granulocytic ehrlichiosis (HGE) agent. This suggests that the HGE agent or an antigenically related organism has been present in rodent populations in this locality for more than a decade, and was present in the region at least 12 yr before a case of human disease was recognized.

Animals↗
PubMed1998

Isolation of Bartonella spp. from embryos and neonates of naturally infected rodents.

Embryos and neonatal offspring of wild-captured cotton rats (Sigmodon hispidus) and white-footed mice (Peromyscus leucopus) were tested for the presence of Bartonella spp. Isolates of Bartonella spp. were obtained from 18 of 31 embryos and 7 of 19 neonates from bacteremic dams of the two species; no isolates were obtained from material from non-bacteremic dams. Sequence analysis demonstrated that the isolates from embryos and neonates matched the phylogenetic group of Bartonella spp. isolates obtained from the mother. No antibodies to homologous Bartonella spp. antigens were detected in maternal and neonatal blood or embryonic tissue. These findings suggest the possibility of vertical transmission of Bartonella spp. among natural rodent hosts.

Animals↗
PubMed1998

Evaluation of two oral baiting systems for wild rodents.

Tetracycline hydrochloride (TC)-treated peanut butter or rodent chow baits were distributed during March 1990, on separate 0.53 ha sites in Oglethorpe County, Georgia (USA). Rodents were trapped on a control site prior to bait distribution and on two baited sites 6 days post-distribution. Cleaned skulls from euthanized mammals were grossly examined for TC fluorescence using an ultraviolet (UV) light. Mandibles were sectioned and examined for TC fluorescence using an ultraviolet light microscope. All 21 cotton rats (Sigmodon hispidus), four eastern harvest mice (Rithrodontomys humulis), and two golden mice (Ochrotomys nuttalli) captured on the control site were negative for TC fluorescence. On the peanut butter bait site, mandible sections from 29 of 32 (91%) cotton rats, three of three (100%) eastern harvest mice, two of three (66%) golden mice, zero of five (0%) white-footed mice (Peromyscus leucopus), one of three (33%) short-tailed shrews (Blarina brevicauda), and zero of two (0%) least shrews (Cryptotis parva) were positive for TC. Results from the rodent chow bait site indicated that 18 of 25 (72%) cotton rats, zero of three (0%) eastern harvest mice, two of seven (29%) golden mice, zero of four (0%) white-footed mice, and zero of four (0%) least shrews were positive for TC fluorescence in mandible sections. These results suggest that a large portion of a free-ranging small rodent population can be administered biological markers or vaccines using baits.

Animal Feed↗
PubMed1999

Relationships of deer mouse movement, vegetative structure, and prevalence of infection with Sin Nombre virus.

The effects of vegetative structure on movement of deer mice (Peromyscus maniculatus) were examined in two distinct vegetation associations, one near Hesperus and the other near Molina in western Colorado (USA) from June-October 1994 to October 1998. We monitored movement by live-trapping small mammals within Gambel's oak/mixed-grass (Hesperus) and sage brush/juniper (Molina) vegetation types. Vegetative structure differed between the sites with Molina having more cover provided by shrubs and Hesperus having more cover provided by forbs. Adult male deer mice moved greater distances at Hesperus than at Molina. Sub-adult males tended to move greater distances than did adult females. Relative abundances of deer mice tended to differ by season, but the average relative abundance of deer mice was greater at Molina. Long-term prevalence of infection with SNV was greater at Hesperus and was greatest in adult males at Hesperus (36.1%). Adult males at Molina exhibited a prevalence of infection with SNV of 25.0%. Infection with SNV was highly associated with scars or wounds for adult male, adult female, and juvenile male deer mice at Hesperus, but only for adult female deer mice at Molina. The presence of scars or wounds tended to be associated with greater age, but male deer mice at Hesperus were more likely to have wounds than female deer mice of the same age class. A similar pattern, excluding juveniles, was observed at Molina. Intraspecific interactions and environmentally elicited long-distance movements of deer mice may play a role in prevalence of infection with SNV in these animals.

Age Distribution↗
PubMed1999

Implications of raccoon latrines in the epizootiology of baylisascariasis.

Raccoons (Procyon lotor) frequently establish defecation sites, termed latrines, on large logs, stumps, rocks, and other horizontally oriented structures/surfaces. These latrines are important foci of infective eggs of Baylisascaris procyonis, a nematode parasite of raccoons which is pathogenic to numerous species of mammals and birds. To examine the role of raccoon latrines in this animal-parasite interaction, we documented animal visitations to raccoon latrines in two large forested tracts and two woodlots in Indiana (USA) during 1994 and 1995. Species richness of vertebrate visitors did not differ between sites or years, but species composition differed by site and year. Fourteen mammal and 15 bird species were documented visiting raccoon latrines. Small granivorous mammals, including white-footed mice (Peromyscus leucopus), eastern chipmunks (Tamias striatus), and tree squirrels (Sciurus carolinensis, S. niger, Tamiasciurus hudsonicus) were the most common visitors to latrine sites. White-footed mice, chipmunks, white-breasted nuthatches (Sitta carolinensis), and opossums (Didelphis virginiana) were photographed foraging on undigested seeds in raccoon feces. Active foraging at latrines also was shown experimentally; seeds embedded in raccoon feces were removed at a greater rate at latrine sites than at nonlatrines. We conclude that raccoon latrines are visited routinely by a variety of vertebrates, especially small granivorous rodents and birds which forage for seeds in raccoon feces, and that raccoon latrines are probable sites of transmission of B. procyonis to susceptible mammals and birds.

Animals↗
PubMed2001

Do unusual site-specific population dynamics of rodent reservoirs provide clues to the natural history of hantaviruses?

Between January 1995 and November 1997, longitudinal mark-recapture studies of rodent hosts of hantaviruses in a disturbed microhabitat within a shortgrass prairie ecosystem in southeastern Colorado (USA) were conducted. The site was distinguished by edaphic and floristic characteristics unique to this area and associated with historical land use patterns, as well as the year-around availability of water from a functioning windmill. Populations of two common rodent species that are hosts for hantaviruses, Peromyscus maniculatus and Reithrodontomys megalotis, had unusually rapid turnover, a younger age structure, and a much lower prevalence of antibody to Sin Nombre virus than did populations at nearby sites in more typical shortgrass prairie and canyon habitats. Based on these findings, we suggest that a stable resident population of the reservoir is critical to the maintenance of hantaviruses at a given site, and we hypothesize that long-lived, persistently infected rodents are the principal transseasonal reservoir of hantaviruses.

Animals↗
PubMed2001

Experimental infection of nontarget species of rodents and birds with Brucella abortus strain RB51 vaccine.

The Brucella abortus vaccine strain RB51 (SRB51) is being considered for use in the management of bnucellosis in wild bison (Bison bison) and elk (Cervus elaphus) populations in the Greater Yellowstone Area (USA). Evaluation of the vaccines safety in non-target species was considered necessary prior to field use. Between June 1998 and December 1999, ground squirrels (Spermophilus richardsonii, n = 21), deer mice (Peromyscus maniculatus, n = 14), prairie voles (Microtus ochrogaster, n = 21), and ravens (Corvus corax, n = 13) were orally inoculated with SRB51 or physiologic saline. Oral and rectal swabs and blood samples were collected for bacteriologic evaluation. Rodents were necropsied at 8 to 10 wk and 12 to 21 wk post inoculation (PI), and ravens at 7 and 11 wk PI. Spleen, liver and reproductive tissues were collected for bacteriologic and histopathologic evaluation. No differences in clinical signs, appetite, weight loss or gain, or activity were observed between saline- and SRB51-inoculated animals in all four species. Oral and rectal swabs from all species were negative throughout the study. In tissues obtained from SRB51-inoculated animals, the organism was isolated from six of seven (86%) ground squirrels, one of six (17%) deer mice, none of seven voles, and one of five (20%) ravens necropsied at 8, 8, 10, and 7 wk PI, respectively. Tissues from four of seven (57%) SRB51-inoculated ground squirrels were culture positive for the organism 12 wk PI; SRB51 was not recovered from deer mice, voles. or ravens necropsied 12, 21, or 11 wk, respectively, PI. SRB51 was not recovered from saline-inoculated ground squirrels, deer mice, or voles at any time but was recovered from one saline-inoculated raven at necropsy, 7 wk PI, likely attributable to contact with SRB51-inoculated ravens in an adjacent aviary room. Spleen was time primary tissue site of colonization in ground squirrels, followed by the liver and reproductive organs. The results indicate oral exposure to SRB51 does not produce morbidity or mortality in ravens, ground squirrels, deer mice, or prairie voles.

Animals↗
PubMed2001

Safety of Brucella abortus strain RB51 in deer mice.

Brucella abortus strain RB51 is an approved brucellosis vaccine for use in cattle that may have potential as an oral vaccine for use in elk (Cervus elaphus) and/or bison (Bison bison). This study was designed to determine effects of strain RB51 on deer mice (Peromyscus maniculatus), a nontarget species that could have access to treated baits in a field situation. In February 1994, 90 mice were orally dosed or intraperitoneally injected with 1 x 10(8) colony forming units strain RB51 and 77 controls were similarly dosed with sterile saline. At weekly intervals through early April 1994, 4 to 6 mice from each group were euthanized, gross necropsies performed, spleens and uteruses cultured, and tissues examined histologically. All orally inoculated mice cleared the infection by 6 wk post-inoculation (PI). While most of the injected mice cleared the infection by 7 wk PI, a few required 9 wk. There were minimal adverse effects attributable to strain RB51. Apparently, strain RB51 would not negatively impact P. maniculatus populations if it were used in a field situation. Also, deer mice appear to be able to clear the vaccine in 6 to 9 wk, thus the probability of these mice transmitting the vaccine to other animals is low.

Administration, Oral↗
PubMed2002

Novel potential reservoirs for Borrelia sp. and the agent of human granulocytic ehrlichiosis in Colorado.

Previous work demonstrated that Ixodes spinipalpis ticks maintained an enzootic cycle of Borrelia bissettii and the agent of human granulocytic ehrlichiosis (aoHGE) within woodrats (Neotoma mexicana) and deer mice (Peromyscus maniculatus) in northern Colorado (USA). Because I. spinipalpis is the only known vector of B. bissettii and aoHGE in Colorado, this study was designed to determine the reservoir status of other hosts of I. spinipalpis in five distinct ecological zones along the front range and foothills of Colorado. One hundred and twelve rodents of nine species were examined and 11 (10%) were polymerase chain reaction (PCR) positive for aoHGE; 37 (33%) were culture positive for B. bissettii, and five (4%) were coinfected with both organisms based on PCR and culture. Of these, three chipmunk species (Tamias minimus, T. quadrivittatus, and T. umbrinus) were culture positive for B. bissettii, with a single T. minimus coinfected with B. bissettii and aoHGE. In addition, one golden-mantled ground squirrel (Spermophilus lateralis) was positive for both B. bissettii and aoHGE. This is the first report of a golden-mantled ground squirrel harboring either B. bissettii or aoHGE and the initial observation that chipmunks may be a reservoir for B. bissettii in Colorado.

Animals↗
PubMed2003

Spontaneous gallstone formation in deer mice: interaction of cholesterol, bile acids, and dietary fiber.

A study of the physiologic and ecologic factors involved in a spontaneous seasonal gallstone cycle of deer mice (Peromyscus maniculatus gambelii) was conducted at the Tulelake National Wildlife Refuge (California, USA) from March 1991 to June 1992. The specific hypothesis examined was whether or not seasonal increases in dietary fiber intake provides the necessary conditions for a solubility defect, or supersaturation mechanism, resulting in precipitation of cholesterol gallstones. Results indicated that in addition to the seasonal gallstone prevalence cycle, these deer mice exhibit significant seasonal cycling in serum cholesterol, serum bile acids, fecal bile acids, and diet composition. These physiologic and dietary cycles were phase-advanced 3 mo over the gallstone prevalence cycle, indicating an approximate 3 mo time period for gallstone formation under field conditions. Further, seasonal dietary fiber (plant material and seeds) was positively correlated with both serum cholesterol and the fecal bile acids. This suggests that in wild deer mice, variations in dietary fiber may significantly affect the resorption of bile acids, thereby providing a potential physiologic and nutritional mechanism for spontaneous cholesterol gallstone formation.

Analysis of Variance↗
PubMed2003

Rapid and simple method for screening wild rodents for antibodies to Sin Nombre hantavirus.

Sin Nombre hantavirus (SNV) is the primary etiologic agent of hantavirus cardiopulmonary syndrome (HCPS) in the United States and Canada. Hantavirus cardiopulmonary syndrome is a zoonotic disease. The most common reservoir is the deer mouse (Peromyscus maniculatus), although numerous other species of wild rodent can carry the viruses that cause HCPS throughout the Americas. Infected rodents show no signs of clinical disease but they develop persistent infection. Sin Nombre virus can be contracted by exposure to feces, urine, or saliva of its rodent reservoirs. Detection of infection in rodents is most often based upon detection of specific antibodies; many laboratories use enzyme linked immunosorbent assays (ELISAs), which require a specialized electrical ELISA reader. Enzyme linked immunosorbent assay readers are not readily amenable to field usage. We describe a portable test, the strip immunoblot assay (SIA), which we have utilized in field diagnosis. The test can be conducted in approximately 6 hr during the day or can be conducted overnight. The test can be used to detect rodents positive for SNV antibody while they are in traps. We show that results with the SIA have excellent concordance with western blot and reverse transcriptase polymerase chain reaction tests.

Animals↗
PubMed2005

Epizootiology of Sin Nombre and El Moro Canyon hantaviruses, southeastern Colorado, 1995-2000.

Sin Nombre virus (SNV) is an etiologic agent of hantavirus pulmonary syndrome. To better understand the natural history of this virus we studied population dynamics and temporal pattern of infection of its rodent hosts in southeastern Colorado (USA) from 1995 to 2000. We present evidence for the presence of two hantaviruses, SNV in deer mice (Peromyscus maniculatus) and El Moro Canyon virus in western harvest mice (Reithrodontomys megalotis), at our study sites. Sin Nombre virus appeared only sporadically in deer mouse populations; overall prevalence of antibody to SNV was 2.6%. El Moro Canyon virus was enzootic: seroconversions occurred throughout the year; antibody prevalence (11.9% overall) showed a delayed-density-dependent pattern, peaking as relative abundance of mice was declining. Males of both host species were more frequently infected than were females. An apparently lower mean survivorship (persistence at the trapping site) for SNV antibody-positive deer mice could indicate a detrimental effect of SNV on its host, but might also be explained by the fact that antibody-positive mice were older when first captured.

Age Factors↗
PubMed2005

Long-term dynamics of Sin Nombre viral RNA and antibody in deer mice in Montana.

Infections with hantaviruses in the natural host rodent may result in persistent, asymptomatic infections involving shedding of virus into the environment. Laboratory studies have partially characterized the acute and persistent infection by Sin Nombre virus (SNV) in its natural host, the deer mouse (Peromyscus maniculatus). However, these studies have posed questions that may best be addressed using longitudinal studies involving sequential sampling of individual wild-caught, naturally infected mice. Using enzyme immunoassay and polymerase chain reaction (PCR) analysis of monthly blood samples, we followed the infection status of deer mice in a mark-recapture study in Montana for 2 yr. Only six of 907 samples without IgG antibody to SNV contained detectable SNV RNA, suggesting that there is a very brief period of viremia before the host develops detectable antibody. The simultaneous presence of both antibody and viral RNA in blood was detected in consecutive monthly samples for as long as 3 mo. However, chronic infection was typified by alternating characteristics of PCR positivity and PCR negativity. Two possible interpretations of these results are that 1) viral RNA may be consistently present in the blood of chronically infected deer mouse, but that viral RNA is near the limits of PCR detectability or 2) SNV RNA sporadically appears in blood as a consequence of unknown physiological events. The occurrence of seasonal patterns in the proportion of samples that contains antibody and that also contained SNV RNA demonstrated a temporal association between recent infection (antibody acquisition) and presence of viral RNA in blood.

Animals↗
PubMed1999

A mathematical model of the ecology of Lyme disease.

A mathematical model of enzootic Lyme-disease transmission in a natural focus is presented. This model is based on the life history of the vector tick Ixodes scapularis Say and the primary reservoir host Peromyscus leucopus. Using this model, the threshold condition for the disease to be able to invade a nonenzootic region is determined as a function of the various possible transmission chains operating throughout the year. These expressions show that the transmission chain in which ticks acquire the disease from mice in the fall and transmit it back to mice as nymphs in the spring is the most important chain (contributing approximately 87% of the elasticity of the threshold for the parameter choices examined). Equilibrium disease levels were examined under the assumption of a constant tick population; these levels were determined as a function of tick and mouse density, the vertical transmission rate, the infectivity of mice, and the survivorship parameters of the ticks and of the tick-host contact rates. Vertical transmission has a disproportionately large effect, since unfed infected larval ticks have two opportunities to feed on mice, rather than only one opportunity (as for a newly infected unfed nymph). Finally, a global sensitivity analysis based on Latin hypercube sampling is performed, in which is shown the importance of quantifying the natural history of infection in mice, and of elucidating the contribution of other hosts for I. scapularis than mice.

Animals↗
PubMed2001

Microevolution in island rodents.

We perform a meta-analysis on morphological data from four island rodent populations exhibiting microevolution (< approximately/= 100 years). Data consisting of incidences of skeletal variants, cranial, and external measurements are from house mice (Mus musculus) on one Welsh and one Scottish island, black rats (Rattus rattus) on two Galapagos islands, and deer mice (Peromyscus maniculatus) on three California Channel islands. We report extremely high rates of microevolution for many traits; 60% of all mensural traits measured changed at a rate of 600 d or greater (max. 2682 d). The proportion of all mensural traits evolving at 600-800 d (23%) was idiosyncratic and departed from an expected negative exponential distribution. We argue that selection, rather than founder events, is largely responsible for the substantial shifts in morphology seen among insular rodents. Examining individual traits, there is a trend towards the nose becoming longer and wider, while the skull becomes shallower, shown by both rats and mice on five different islands. We found a significant correlation between island size and degree of skeletal variant evolution and between island distance from the mainland (or nearest island) and degree of cranial and external character evolution. Thus, microevolution of rodents is greater on smaller and more remote islands.

Animals↗
PubMed2003

Hantavirus.

Sin Nombre virus (SNV), an emerging pathogen in the United States, was identified in 1993. This hantavirus, a member of the Bunyaviridae family of RNA viruses, is transmitted by its reservoir host Peromyscus maniculatus, the deer mouse. Transmission is by inhalation of aerosolized feces, urine, or saliva from the infected mice. The illness that pursues, hantavirus pulmonary syndrome (HPS), is characterized initially by mild flu-like symptoms, followed by rapid progression to respiratory distress. There is no established therapeutic regimen and treatment is only supportive. Preventive methods include attempts to minimize contact with the rodents since elimination of the virus is not realistic.

Animals↗
PubMed1992

Cystitis induced by infection with the Lyme disease spirochete, Borrelia burgdorferi, in mice.

Previous studies have demonstrated that the urinary bladder is a consistent source for isolating the Lyme disease spirochete, Borrelia burgdorferi, from both experimentally infected and naturally exposed rodents. We examined histopathologic changes in the urinary bladder of different types of rodents experimentally infected with Lyme spirochetes, including BALB/c mice (Mus musculus), nude mice (M. musculus), white-footed mice (Peromyscus leucopus), and grasshopper mice (Onychomys leucogaster). Animals were inoculated intraperitoneally, subcutaneously, or intranasally with low-passaged spirochetes, high-passaged spirochetes, or phosphate-buffered saline. At various times after inoculation, animals were killed and approximately one-half of each urinary bladder and kidney were cultured separately in BSK-II medium while the other half of each organ was prepared for histologic examination. Spirochetes were cultured from the urinary bladder of all 35 mice inoculated with low-passaged spirochetes while we were unable to isolate spirochetes from any kidneys of the same mice. The pathologic changes observed most frequently in the urinary bladder of the infected mice were the presence of lymphoid aggregates, vascular changes, including an increase in the number of vessels and thickening of the vessel walls, and perivascular infiltrates. Our results demonstrate that nearly all individuals (93%) of the four types of mice examined had a cystitis associated with spirochetal infection.

Animals↗