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PubMed1963

Age of weaning in two subspecies of deer mice.

Weaning age in deer mice is defined as the age at which the young mice maintain or gain weight during a 24-hour period of isolation; mice younger than weaning age lose weight. Two subspecies of deer mice differed in weaning age; the age for Peromyscus maniculatus bairdii was 18 days; for P. m. gracilis, 24 days. Age and food consumption were better predictors of the weaning condition, as defined in terms of weight change with isolation, than body weight.

Aging↗

PubMed1964

VENEZUELAN EQUINE ENCEPHALITIS VIRUS FROM SOUTH FLORIDA.

Venezuelan equine encephalitis virus was isolated three times from the Culex (Melanoconion) species of mosquitoes collected in south Florida in June, July, and October, 1963. Specific antibody was present in 16 of 28 Peromyscus gossypinus (cotton mice) and 3 of 16 Sigmodon hispidus (cotton rats) sampled from one of the infected sites in January 1964.

Animals↗

PubMed1994

An experimental study of inbreeding depression in a natural habitat.

Inbreeding is known to lead to decreased survival and reproduction in captive populations of animals. It is also important to know whether inbreeding has deleterious effects in natural habitats. An estimate was made of the effects of inbreeding in white-footed mice, Peromyscus leucopus noveboracensis, derived from a wild population. This study demonstrates that inbreeding had a significant detrimental effect on the survivorship of mice reintroduced into a natural habitat. This effect was more severe than the effect observed in laboratory studies of the population.

Analysis of Variance↗

PubMed1993

Genetic identification of a hantavirus associated with an outbreak of acute respiratory illness.

A mysterious respiratory illness with high mortality was recently reported in the southwestern United States. Serologic studies implicated the hantaviruses, rodent-borne RNA viruses usually associated elsewhere in the world with hemorrhagic fever with renal syndrome. A genetic detection assay amplified hantavirus-specific DNA fragments from RNA extracted from the tissues of patients and deer mice (Peromyscus maniculatus) caught at or near patient residences. Nucleotide sequence analysis revealed the associated virus to be a new hantavirus and provided a direct genetic link between infection in patients and rodents.

Animals↗

PubMed1987

Prevalence of Borrelia burgdorferi and Babesia microti in mice on islands inhabited by white-tailed deer.

Borrelia burgdorferi and Babesia microti were isolated from 35 of 51 white-footed mice (Peromyscus leucopus) and meadow voles (Microtus pennsylvanicus) captured on two Narragansett Bay, R.I., islands inhabited by deer, the principal host for the adult stages of the vector tick, Ixodes dammini. Immature ticks parasitized mice from both islands. From 105 mice captured on four other islands not inhabited by deer neither pathogen was isolated, nor were I. dammini found.

Animals↗

PubMed2004

Interaction and transmission of two Borrelia burgdorferi sensu stricto strains in a tick-rodent maintenance system.

In the northeastern United States, the Lyme disease agent, Borrelia burgdorferi sensu stricto, is maintained by enzoonotic transmission, cycling between white-footed mice (Peromyscus leucopus) and black-legged ticks (Ixodes scapularis). B. burgdorferi sensu stricto is genetically variable and has been divided into three major genotypes based on 16S-23S ribosomal DNA spacer (RST) analysis. To better understand how genetic differences in B. burgdorferi sensu stricto may influence transmission dynamics in nature, we investigated the interaction between an RST1 and an RST3 strain in a laboratory system with P. leucopus mice and I. scapularis ticks. Two groups of mice were infected with either BL206 (RST1) or B348 (RST3). Two weeks later, experimental mice were challenged with the opposite strain, while control mice were challenged with the same strain as that used for the primary infection. The transmission of BL206 and B348 from infected mice was then determined by xenodiagnosis with uninfected larval ticks at weekly intervals for 42 days. Mice in both experimental groups were permissive for infection with the second strain and were able to transmit both strains to the xenodiagnostic ticks. However, the overall transmission efficiencies of BL206 and B348 were significantly different. BL206 was more efficiently transmitted than B348 to xenodiagnostic ticks. Significantly fewer double infections than expected were detected in xenodiagnostic ticks. The results suggest that some B. burgdorferi sensu stricto strains, such as BL206, may be preferentially maintained in transmission cycles between ticks and white-footed mice. Other strains, such as B348, may be more effectively maintained in different tick-vertebrate transmission cycles.

Animals↗

PubMed1978

Ultrastructural and immunological aspects of the phagocytosis of Trypanosoma brucei by mouse peritoneal macrophages.

Trypanosome-activated mouse peritoneal macrophages phagocytized and digested Trypanosoma brucei in vitro and in vivo, but in the absence of specific antiserum and complement the degree of phagocytosis was minimal. Ultrastructurally, the parasites attached to the macrophage by their flagella, and ingestion proceeded flagellum first. Once ingested, T. brucei was degraded, presumably due to fusion of the parasite-containing phagosome with lysosomes. Contrariwise, normal mouse peritoneal macrophages displayed negligible ability to ingest T. brucei, even in the presence of specific antiserum and complement. During trypanosomiasis in deer mice (Peromyscus maniculatus), the development of hypergammaglobulinemia correlated with enhanced phagocytosis of T. brucei by macrophages, but only at early post-inoculation days (PID 5 to 15). Complement lysis of trypanosomes was not identified in these experiments. Between PID 20 to 30, antiserum and complement either had no phagocytosis-promoting ability or depressed the phagocytosis of T. brucei by macrophages. These results indicate that both specific antibody and complement contribute to the ingestion of T. brucei by activated macrophages, but that parasite antigenic variation effectively abrogates the phagocytic defense mechanism.

Animals↗

PubMed1985

Identification of endemic foci of Lyme disease: isolation of Borrelia burgdorferi from feral rodents and ticks (Dermacentor variabilis).

Borrelia burgdorferi, the etiological agent of Lyme disease, was isolated from the blood, kidneys, spleens, eyes, or livers of white-footed mice (Peromyscus leucopus) (n = 19 of 22) and from the blood, kidneys, or spleens of eastern chipmunks (Tamias striatus) (n = 2 of 2) captured at three foci for Lyme disease in eastern Connecticut. These bacteria were cultured most frequently from spleens (n = 19) and kidneys (n = 15). B. burgdorferi persisted in one mouse for at least 60 days. One spirochetemic mouse had infected Ixodes dammini and Dermacentor variabilis larvae attached, suggesting that these ticks may have acquired spirochetes from the host. Spirochetes isolated from P. leucopus, T. striatus, and D. variabilis larvae were serologically and genetically indistinguishable from reference B. burgdorferi isolates. We conclude that isolation of spirochetes from feral rodents is a method for identifying endemic areas of Lyme disease.

Animals↗

PubMed1987

New infectious spirochete isolated from short-tailed shrews and white-footed mice.

A spirochete with two periplasmic flagella was isolated from the blood or tissues of spleens and kidneys from short-tailed shrews (Blarina brevicauda) and white-footed mice (Peromyscus leucopus) in Connecticut and Minnesota. After inoculation, the shrew-mouse spirochete infected Swiss mice and Syrian hamsters. This spirochete is morphologically and serologically distinct from the species of Treponema, Borrelia, Leptospira, and Spirochaeta examined.

Animals↗

PubMed1987

Prevalence of Borrelia burgdorferi in white-footed mice and Ixodes dammini at Fort McCoy, Wis.

Borrelia burgdorferi, the causative agent of Lyme disease, was isolated from 15 of 17 white-footed mice (Peromyscus leucopus) and 54 of 82 subadult Ixodes dammini from Fort McCoy, Wis. Of the 47 isolates tested, all reacted in indirect fluorescent-antibody tests with monoclonal antibodies directed against a surface protein of B. burgdorferi (approximate molecular weight, 31,000) and flagellins that are common to all Borrelia species. Indirect fluorescent-antibody reactions were variable when an antibody that binds to a surface protein with an approximate molecular weight of 34,000 was tested. The major proteins of isolates from ticks and mice had approximate molecular weights of 31,000, 34,000, and 41,000. Antibodies to B. burgdorferi were present (titer, greater than or equal to 1:64) in 16 of 97 white-tailed deer (Odocoileus virginianus). The mean number of subadult I. dammini on mice captured in June 1986 was 6.5, and the mean number of adult I. dammini on deer killed in November 1986 was 5.9. The presence of ticks and the high prevalence of I. dammini and mice infected with B. burgdorferi establish that Fort McCoy is an area in which the Lyme disease agent is highly endemic, even though there have been relatively few documented cases in humans. The low number of reported cases in humans may be a result of National Guard and reserve unit personnel returning home to civilian life and having symptoms expressed subsequently, or it could be due to misdiagnosis or nonreporting.

Animals↗

PubMed1988

New Borrelia burgdorferi antigenic variant isolated from Ixodes dammini from upstate New York.

A previously undescribed Borrelia burgdorferi antigenic variant was isolated from each of four Ixodes dammini larvae removed from white-footed mice, Peromyscus leucopus, captured in Millbrook, N.Y. This site is in the northern range of the known distribution of the tick in the northeastern United States. The molecular weights of approximately 32,500 and 35,500 for outer surface A and outer surface B proteins, respectively, were distinctly higher than those for previously characterized isolates from North American ticks, humans, and wild mammals. A prominent low-molecular-weight protein of about 23,500 was also present. All four isolates infected Syrian hamsters and retained their antigenicity after passage through these rodent hosts. Serum samples from patients with Lyme disease tended to have immunoglobulin M, immunoglobulin G, and immunoglobulin antibodies to Connecticut B. burgdorferi 2591 at titers slightly higher than or equal to those recorded for an antigenically different strain of B. burgdorferi from Millbrook, N.Y.

Animals↗

PubMed1988

Borrelia burgdorferi infection surrounding La Crosse, Wis.

This investigation defined the extent of Borrelia burgdorferi infection surrounding La Crosse, Wis. White-footed mice, Peromyscus leucopus or P. maniculatis, were captured from sites in Wisconsin, Minnesota, and Iowa and cultured for B. burgdorferi to define the local boundaries of the midwestern Lyme disease area. All foci of B. burgdorferi infection (N1, N2, N3, and N4) were located north of interstate highway 90 except focus S2, which was south of the highway near Fort McCoy, Wis. The interstate highway may have been a barrier to deer movement which slowed the southward dispersal of Ixodes dammini. B. burgdorferi was isolated from 12 (63%) of the mice captured from site N4, which was adjacent to the western border of Fort McCoy. Unexpectedly, no B. burgdorferi-infected mice were isolated at site N0, located north of interstate highway 90 and enclosed by areas in which B. burgdorferi infection is endemic. This site is surrounded by natural barriers which may have slowed the spread of I. dammini by deer. The Wisconsin area in which B. burgdorferi is endemic should now include the surrounding area north of interstate highway 90 west from Fort McCoy to the Mississippi River. Additional studies are needed to define the rapidity, limits, and means of I. dammini dispersal into southern Wisconsin.

Animals↗

PubMed1988

Ticks and biting insects infected with the etiologic agent of Lyme disease, Borrelia burgdorferi.

Members of 18 species of ticks, mosquitoes, horse flies, and deer flies were collected in southeastern Connecticut and tested by indirect fluorescent-antibody staining methods for Borrelia burgdorferi, the etiologic agent of Lyme disease. An infection rate of 36.2% (116 tested), recorded for immature Ixodes dammini, exceeded positivity values for all other arthropod species. Prevalence of infection for hematophagous insects ranged from 2.9% of 105 Hybomitra lasiophthalma to 14.3% of seven Hybomitra epistates. Infected I. dammini larvae and nymphs coexisted with infected Dermacentor variabilis (American dog tick) immatures on white-footed mice (Peromyscus leucopus), but unlike I. dammini, none of the 55 adult American dog ticks collected from vegetation harbored B. burgdorferi. Groups of 113 field-collected mosquitoes of Aedes canadensis and 43 Aedes stimulans were placed in cages with uninfected Syrian hamsters. Of these, 11 females of both species contained B. burgdorferi and had fed fully or partially from the hamsters. No spirochetes were isolated from the hamsters, but antibodies were produced in one test animal.

Aedes↗

PubMed1989

Ear punch biopsy method for detection and isolation of Borrelia burgdorferi from rodents.

An ear punch biopsy method for the detection and isolation of Borrelia burgdorferi from rodents was developed. The ear punch biopsy proved to be extremely sensitive, detecting spirochetes in 100% (11 of 11) of laboratory hamsters infected by tick bite and 95.8% (23 of 24) of hamsters infected by intraperitoneal inoculation. When cultured at 4 to 6 weeks postinfection, 92 to 100% of the ear punches taken from individual hamsters yielded viable spirochetes. B. burgdorferi was detected in sequential cultures from animals as early as 4 days postinfection and as late as 20 weeks postinfection. A total of 86% (6 of 7) of field-collected white-footed mice (Peromyscus leucopus) which were positive for B. burgdorferi as determined by xenodiagnosis were also positive by the ear punch method. The ear punch biopsy method allows individual rodents to be sampled for B. burgdorferi serially over a long period and thus should prove useful for both field and laboratory experiments.

Animals↗

PubMed1991

Antibody to a 39-kilodalton Borrelia burgdorferi antigen (P39) as a marker for infection in experimentally and naturally inoculated animals.

Borrelia burgdorferi expresses a conserved, species-specific 39-kDa protein (P39) that can stimulate antibodies during human infection. To confirm that anti-P39 antibodies are produced consistently in animals exposed to infectious spirochetes, white-footed mice, Peromyscus leucopus, and laboratory white mice, Mus musculus (strain BALB/c), were experimentally inoculated with either infectious or noninfectious B. burgdorferi and the antibody response to P39 was determined by immunoblot at 21 days postinoculation. All mice inoculated with approximately 10(7) infectious B. burgdorferi produced anti-P39 antibodies and were cultured positive for this spirochete. Mice inoculated with similar numbers of inactivated or viable noninfectious B. burgdorferi still producing P39 did not induce anti-P39 antibodies. By contrast, putative antiflagellin antibodies were detected in less than 18% of the infected animals, which supports the notion that antibody reactive with flagellin may not be reliable as a marker for B. burgdorferi exposure as was originally thought. Mice infected with B. burgdorferi following exposure to ticks (Ixodes dammini) produced anti-P39 antibodies no later than 7 days postinfection, indicating that P39 is an effective immunogen in natural infections. Notably, anti-P39 antibodies were the predominant B. burgdorferi reactive antibodies detected early in the infection. Our results indicate that anti-P39 antibodies are produced in response to an active infection and are therefore reliable markers for infection in experimentally and naturally inoculated animals.

Animals↗

PubMed1994

Comparison of different strains of Borrelia burgdorferi sensu lato used as antigens in enzyme-linked immunosorbent assays.

Eight strains of Borrelia burgdorferi sensu lato were tested with serum samples from persons who had Lyme borreliosis or syphilis in class-specific enzyme-linked immunosorbent assays (ELISAs). Antigens of B. burgdorferi sensu stricto, of Borrelia garinii, and of Borrelia spirochetes in group VS461 were prepared from cultured bacteria isolated from ticks, a white-footed mouse (Peromyscus leucopus), or human tissues in North America, the former Soviet Union, and Japan. Nearly all of the serum specimens that contained immunoglobulins to strain 2591, a Connecticut isolate, were also positive in antibody tests with the other seven strains. In general, all eight strains reacted similarly and were suitable as coating antigens in class-specific ELISAs. Assay sensitivities ranged from 82.6 to 100% in analyses for immunoglobulin M and G antibodies. Compared with reference antigen strain 2591, strains 231 (a tick isolate from Canada) and NCH-1 (a human skin isolate from Wisconsin) resulted in higher antibody titers in an ELISA. Syphilitic sera cross-reacted in all tests regardless of the antigen used. Key immunodominant proteins are shared among the closely related strains of B. burgdorferi sensu lato tested, but it is suspected that variations in antigen compositions among these spirochetes may sometimes affect assay performance for detecting serum antibodies.

Animals↗

PubMed1996

Comparison of infectivities of six tick-derived isolates of Borrelia burgdorferi for rodents and ticks.

The infectivity and dissemination to the skin of six isolates of Borrelia burgdorferi were evaluated by inoculating them into groups of deer mice (Peromyscus maniculatus), hamsters, and Swiss Webster mice. Rodent infection was assayed by culture of ear punch biopsy specimens taken at 4, 8, and 12 weeks postinoculation (p.i.). Spirochetes were detected in biopsy specimens from individuals of all three host species that had been inoculated with four isolates (CA3, CA4, CA7, and CA8). Ear punch biopsy specimens taken from Swiss Webster mice at 12 weeks p.i. yielded an additional reisolate (CA2), even though these animals did not seroconvert. The remaining isolate (CA9) was not recovered from any host. However, two deer mice and all hamsters and Swiss Webster mice inoculated with CA9 seroconverted. All six isolates were of low infectivity to ticks when inoculated intramuscularly into hosts. Only 4 (1.6%) of 250 Ixodes pacificus larvae acquired and transstadially maintained infection from hosts inoculated intramuscularly. Infectivity of three isolates for ticks also was tested in Swiss Webster mice injected intradermally. The mean prevalences of infection in xenodiagnostic ticks fed on these mice at 4 weeks p.i. were 47.9, 1.2, and 2.2% for isolates CA4, CA7, and CA8, respectively. The mean prevalences of infection for ticks fed on the same mice at 12 weeks p.i. were 36.4, 11.8, and 20.4%, respectively. Such differences in the infectivity and rate of dissemination of individual isolates of B. burgdorferi should be considered during studies of reservoir and vector competence.

Animals↗

PubMed1996

Novel Borrelia burgdorferi isolates from Ixodes scapularis and Ixodes dentatus ticks feeding on humans.

Seven cultures of Borrelia burgdorferi differing from strains B31 and ZS7 were identified from among 99 isolates from Ixodes scapularis ticks and from white-footed mice (Peromyscus leucopus) and 1 isolate from an Ixodes dentatus tick. Five of the six novel isolates from I. scapularis and the isolate from I. dentatus were from ticks feeding on humans. The six isolates from I. scapularis lacked OspA and OspB, four possessed an OspD band, and two reacted with an anti-OspC monoclonal antibody. Restriction fragment length polymorphisms of HindIII-digested DNAs from six OspA-negative isolates did not hybridize with radiolabeled ospA or LA88 DNA, and only isolate 46047 hybridized with the pG gene. Fragments similar to those recorded for the standard B. burgdorferi sensu stricto strains B31 and ZS7 were obtained with the fla and the HSP70 genes. Pulsed-field gel electrophoresis patterns of DNA digested with MluI included the specific B. burgdorferi sensu stricto band at 135 kbp for the five OspA-negative isolates from I. scapularis ticks. The six novel isolates apparently lack the 55-kbp plasmid encoding OspA. The pG-containing plasmid may be missing from all but isolate 46047. The isolate from the I. dentatus tick was similar to previous isolates from I. dentatus ticks feeding on rabbits. None of the isolates could be recovered from inoculated C3H/HeNCrlBR or white-footed mice. All isolates reacted with sera from humans with early or late Lyme disease. Our studies demonstrate that these borreliae occur in ticks feeding on humans, and therefore, at least some humans in the northeastern United States are likely being exposed to borreliae other than the classic B31-type strains that have thus far been isolated from humans.

Animals↗