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PubMed1976

Human babesiosis on Nantucket Island: transmission by nymphal Ixodes ticks.

In order to identify potential vectors of human babesiosis (Babesia microli) in southern Massachusetts, I attempted to transmit the infection via nymphal ticks of that species found to be most abundant on reservoir hosts (Peromyscus leucopus) in nature. Mice were collected at frequent intervals throughout a year in a known enzootic focus on Nantucket Island, and ticks were removed by hand. Ticks of only two species were present; larvae and nymphs of Ixodes scapularis were about 10 times as numerous as were those of Dermacentor variabilis. Accordingly, I. scapularis were used in attempts to transmit a strain of Babesia derived from a human infection recently acquired near the study site. Larvae were permitted to feed on an infected hamster and nymphs derived from these larvae were placed on each of 11 non-infected hamsters. All but one hamster became infected. Nymphs reared from larvae that had attached to a non-infected hamster did not transmit babesiosis to other hamsters. These results suggest that I. scapularis serves as a vector of babesios-s on Nantucket hamsters. These results suggest that I. scapularis serves as a vector of babesiosis on Nantucket Island.

Animals↗
PubMed1976

Experimental infection of North American mammals with epidemic Venezuelan encephalitis virus.

Eighty-three wild mammals of ten species were inoculated with a first mouse passage level Venezuelan encephalitis (VE) virus isolated from south Texas in 1971 during the VE outbreak. Rodents were highly susceptible to VE infection and circulated VE virus at levels ranging from 10(7.7) to 10(11.5) suckling mouse intracranial lethal doses per ml for 2 to 4 days. These levels of virus could easily infect vector mosquitoes. Mortality was high in all species of rodents except Sigmodon hispidus, adult Neotoma micropus, and adult Peromyscus leucopus. Lagomorphs were susceptible to VE infection but circulated VE virus at or near mosquito threshold levels for 1 day only. Raccoons and opossums were relatively resistant to VE infection or circulated low levels of virus in the blood. Juvenile animals of four species were more susceptible and experienced higher viremias than did adults. In two of the four, mortality was higher in the juveniles than in adults. A consideration of results obtained during this study and those of other investigators led to the conclusion that equines were of major importance, that canines, lagomorphs and rodents were of minor importance, and that other species tested were of no importance as virus amplifiers in VE epizootics.

Animals↗
PubMed1981

Experimental Colorado tick fever virus infection in Colorado mammals.

One hundred and twenty-four small mammals of six species were inoculated with three strains of Colorado tick fever (CTF) virus to define viremia and neutralizing (N) antibody responses. Adult Eutamias minimus and Eutamias embrinus, and juvenile Peromyscus maniculatus and Spermophilus lateralis, were highly susceptible to development of viremic infection. Adult S. lateralis and P. maniculatus were moderately susceptible (greater than or equal to 50% viremic). Five Sylvilagus nuttalli did not become viremic following experimental inoculation. Spermophilus richardsoni was also relatively resistant (less than or equal to 50% viremic). The longest duration of viremia (mean 15.8 days) and highest peak viremia levels (mean peak titer 10(3.9 plaque-forming units per ml) occurred in E. minimus. Adult E. umbrinus, juvenile S. lateralis, and juvenile P. maniculatus had moderate viremias. Adult S. lateralis and S. richardsoni often had short viremias during which virus was only intermittently detectable. N antibody production was most rapid in E. minimus in comparison with other species. In addition, N antibody persisted for 1 year in this species. In other species, many animals lost detectable antibody 5-11 months after infection. No significant differences were found in patterns of infection between three CTF virus strains. We conclude that of the six species inoculated, E. minimus is the best experimental host for CTF virus.

Animals↗
PubMed1981

The ecology of Colorado tick fever in Rocky Mountain National Park in 1974. II. Infection in small mammals.

Field studies of Colorado tick fever (CTF) in small mammals in Rocky Mountain National Park (RMNP) in 1974 established that Eutamias minimus and Spermophilus lateralis were the most important hosts for CTF virus and were the source of virus for immature stages of the tick vector, Dermacentor andersoni. Other species (Peromyscus maniculatus, Spermophilus richardsonii, Eutamias umbrinus) are secondary hosts. The intensity of viral activity in rodents varied greatly from locality to locality. Highest rodent infection rates were found to occur in the Moraine Park area of RMNP. Lowest infection rates occurred above 3,290 meters in altitude at Rainbow Curve and on the tundra. The prevalence of infection in rodents was constant from April--July (5--6% of animals captured were viremic) and then declined to 1.7--2.5% in August and September coincident with a decline in nymphal tick ectoparasitism. Many animals were captured which were simultaneously viremic and antibody-positive. Under field conditions, neutralizing antibody seroconversion does not always occur.

Animals↗
PubMed1981

Endemicity of spotted fever group rickettsiae in Connecticut.

To compare rickettsial infectivity and seropositivity rates against spotted fever group (SFG) rickettsiae, ticks and wild mammals were collected from three areas where Rickettsia rickettsii was thought to be enzootic in Connecticut during 1978-1979, and from four additional sites (with no reported human cases) between 1976 and 1979. Of the 1,001 Dermacentor variabilis examined by the hemolymph test, 59 (5.9%) contained rickettsia-like organisms; direct immunofluorescence tests verified the presence of SFT rickettsiae in 14 specimens. Prevalence of rickettsiae-infected ticks at Newtown, an area where human cases of Rocky Mountain spotted fever probably originated, was 2.2%. Rates for six other areas ranged between 0 and 6.3%. Isolations included Rickettsia montana from four ticks collected at Branford and Woodbridge, and R. rickettsii (R-like strain) from the blood of an acutely ill person. Microagglutination (MA) tests indicated that 15 (14.9%) of 101 Peromyscus leucopus (white-footed mice) from Newtown had agglutinins in titers greater than or equal to 1:8 against R. rickettsii, whereas five of 92 white-footed mice (5.4%) from Brandord, West Hartford, Woodbridge, and Sharon were considered MA-positive. Indirect microimmunofluorescence tests of Procyon lotor (raccoon) sera revealed antibodies to R. rickettsii in 33 of 69 (47.8%) samples from Newtown and in two of 60 (3.3%) from Guilford. Additionally, 17 raccoons had sera specific to R. montana (n = 8) or to the 369-C rickettsia strain (n = 9). Since rickettsia-positive ticks are high-titered seropositive mammals occurred at widely separated sites in Connecticut there are probably several foci of SFG rickettsiae distributed throughout the D. variabilis range.

Animals↗
PubMed1982

Survey for evidence of Colorado tick fever virus outside of the known endemic area in California.

A virus very similar or identical to Colorado tick fever (CTF) virus was recovered from the blood clot of one of 104 black-tailed jack rabbits (Lepus californicus) examined during a survey for various zoonotic agents in mammals and ticks from the University of California, Hopland Field Station, Mendocino County, California, 1974--79. This is the first reported isolation of a CTF-like virus from L. californicus, and only the second time such a virus has been found in northwestern California. Mendocino County is located far outside the known distributional ranges of the most common mammalian hosts of CTF virus and of Dermacentor andersoni, the only proven tick vector for man. The viral isolate is very similar to a CTF-like virus previously recovered from the blood and spleen of a western gray squirrel (Sciurus griseus) from San Luis Obispo County, an area also outside of the previously-known CTF area. Virus was not isolated from 14 additional species of mammals (354 specimens) or from eight species of ticks (4,487 individuals), but CTF-neutralizing antibodies were detected in 28 of 771 (3.6%) sera from seven of 15 mammalian species including significant titers (greater than or equal to 1:8) in two species and one subspecies not previously reported as natural hosts, i.e., brush mouse (Peromyscus boylii), pinyon mouse (P. truei), and Columbian black-tailed deer (Odocoileus hemionus columbianus). CTF indirect immunofluorescent antibodies also were detected in 26 of 129 (20.2%) sera belonging to four of five mammalian species tested. Neutralizing antibodies were found in sera of deer from other localities in Mendocino County, from a deer mouse from Napa County, and from a brush rabbit from Monterey County as well. These findings suggest that a virus identical or similar to CTF virus is widespread in northwestern-westcentral California, and that surveillance for human cases of CTF or a similar disease should be extended to cover this region.

Animals↗
PubMed1986

Diurnal detachment of immature deer ticks (Ixodes dammini) from nocturnal hosts.

To test the possibility that immature deer ticks (Ixodes dammini) may concentrate in the nests of their mouse hosts, we recorded their pattern of detachment. In laboratory experiments, most engorged larvae (greater than 90%) and nymphs (greater than 80%) detached from hamsters between 1200-2000 hours when the 14-hr photophase began at 0600 hours. Time of drop-off was similar regardless of when ticks attached to hosts, but attachment late in the day delayed drop-off by one full day. Ticks detached similarly from naturally-infested Peromyscus leucopus. A post-attachment cue or cues appeared to regulate time of detachment. Such synchronous diurnal detachment may serve to concentrate ticks in the nests of their nocturnal mouse hosts, thereby enhancing pathogen transmission.

Animals↗
PubMed1987

Lyme disease ecology in Wisconsin: distribution and host preferences of Ixodes dammini, and prevalence of antibody to Borrelia burgdorferi in small mammals.

Lyme disease recently has been recognized in Wisconsin. Trapping studies were conducted at four geographically separate and ecologically distinct regions in Wisconsin to elucidate the distribution and host preferences of Ixodes dammini on small and medium sized mammals, and the occurrence of antibodies to Borrelia burgdorferi in these wild mammals. Peak I. dammini larval activity occurred from June-September. Nymphs were most active from May-August. White-footed mice (Peromyscus leucopus) and chipmunks (Tamias striatus) were important hosts for immature ticks. Mean numbers of I. dammini per mouse were highest in regions of high prevalence of Lyme disease. Antibody to B. burgdorferi was detected in sera of 60/371 (16%) white-footed mice, 5/104 (5%) chipmunks, 3/5 (60%) gray squirrels (Sciurus carolinensis), 0/8 raccoons (procyon lotor), and 0/12 opossum (Didelphis virginiana); antibody prevalence correlated positively with I. dammini occurrence, and seropositive animals were not detected in areas where I. dammini were not found. Two of 15 recaptured P. leucopus had greater than or equal to 4-fold changes in antibody titer. B. burgdorferi was cultured from blood of a P. leucopus captured in west-central Wisconsin, and was observed by direct immunofluorescence in 9/23 (39%) I. dammini nymphs. In Wisconsin, I. dammini has increased in numbers and has significantly expanded its range since its first recognition in 1968.

Animals↗
PubMed1987

Prospective seroepidemiology of hantaviruses and population dynamics of small mammal communities of Baltimore, Maryland.

We used a prospective seroepidemiological study, in conjunction with a mark-release-recapture protocol, to investigate the transmission of hantaviruses in four rodent species from Baltimore, Maryland, from June 1984 to June 1986. A total of 1,208 captures of 762 rodents provided 984 individual blood samples. The antibody prevalence, as determined by frequency of reciprocal indirect fluorescent antibody (IFA) titers greater than or equal to 32, was 33.9% in rats (Rattus norvegicus, n = 466), 28.3% in meadow voles (Microtus pennsylvanicus, n = 67), 1.4% in house mice (Mus musculus, n = 146), and 1.2% in white-footed mice (Peromyscus leucopus, n = 83). Populations of all rodents were maximal during the fall and winter months, but population trends were not clearly associated with periods of virus transmission. The mean incidence of seroconversion to a Hantavirus for rats was 12.06/100 rats/month, but incidence rates could not be established for other species. Rats which seroconverted were generally sexually mature animals, and there was evidence of transmission throughout the year. Animals which seroconverted to a Hantavirus achieved high IFA titers, and remained seropositive for the duration of the study.

Animals↗
PubMed1995

Borrelia burgdorferi in eastern Virginia: comparison between a coastal and inland locality.

In Virginia, Borrelia burgdorferi was more prevalent in a site along the Atlantic Ocean, near Maryland, than in an inland site near Williamsburg and Yorktown. At the coastal site on Assateague Island, B. burgdorferi was isolated from 4.2% of 475 animals sampled, including four species of small mammals. Serologic tests indicated that 25-37% of the small rodents assayed had been exposed to B. burgdorferi. Immunofluorescence antibody assays specific for B. burgdorferi showed spirochete infection in Ixodes scapularis and Dermacentor variabilis but not in other species of ticks also examined from this site. At another coastal site (Parramore Island), no evidence of Peromyscus leucopus was found, no immature specimens of I. scapularis were collected, and no isolations were made from numerous raccoons or small mammals sampled. Borrelia burgdorferi infection was found in one I. cookei nymph, but not in numerous specimens of I. scapularis or other tick species from this locality. At the inland site between Williamsburg and Yorktown, B. burgdorferi was isolated from two small mammal species and antibodies to B. burgdorferi were found in only 7-10% of the small mammals sampled. Ixodes scapularis were less abundant at this locality than at the Assateague Island site. Borrelia burgdorferi spirochetes were found in I. scapularis and a single nymph of Amblyomma americanum, but not in any of numerous specimens of four other species. Infection with B. burgdorferi was found in 20% of unfed adult I. scapularis from vegetation, but in only 0.2% of numerous adults from hunter-killed deer. Infection in immature ticks was much lower than at Assateague Island. Borrelia burgdorferi may be more prevalent along the Atlantic coast than in inland areas. Isolations, seroprevalence, immature I. scapularis densities, and spirochete infection rates in ticks were higher at the Assateague Island site than the Williamsburg/Yorktown site. Consequently, the risk of human exposure to Lyme disease may be higher in some parts of the coastal area than elsewhere in Virginia. Overall, B. burgdorferi is less intense in Virginia than in the northeastern United States.

Animals↗
PubMed1995

Isolation of Leishmania (L.) mexicana from wild rodents and their possible role in the transmission of localized cutaneous leishmaniasis in the state of Campeche, Mexico.

Leishmania parasites were isolated from four of seven small rodent species captured in the State of Campeche, Mexico. Signs and/or symptoms of leishmanial infection were restricted to the tail of the mice. Peromyscus yucatanicus endemic to the peninsula of Yucatan and Oryzomys melanotis were added to the list of carriers of Leishmania. Leishmania (L.) mexicana, characterized by an indirect immunofluorescence antibody method using monoclonal antibodies, was identified in one Sigmodon hispidus and one Or. melanotis. The possible role of the different species as primary reservoirs of Leishmania in the peninsula of Yucatan is discussed.

Animals↗
PubMed1996

Occurrence of hantavirus within the rodent population of northeastern California and Nevada.

These studies were initiated to determine the prevalence and hosts of hantaviruses within the rodent population of Nevada and northeastern California. A total of 1,867 rodents were collected, sexed, weighed, identified, and tested by enzyme-linked immunosorbent assay for the presence of antibody against hantavirus nucleocapsid. The primary hosts for hantaviruses in this region were found within the family Muridae (Peromyscus maniculatus. Reithrodontomys megalotis. and Microtus montanus). Studies over time of animals within a defined geographic area indicated that animals with hantavirus antibody are not distributed uniformly over the rodent population in a specific area but were found in foci spanning a distance of only several hundred meters. The antibody prevalence in a given geographic area remained relatively constant with repeated sampling of between 0% and 30%. These data support the hypothesis that rodents within the family Muridae are the primary reservoir for hantaviruses, and the primary risk to biologists for exposure to hantavirus is by contact with members of this family.

Animals↗
PubMed1996

Reservoir competence of four chaparral-dwelling rodents for Borrelia burgdorferi in California.

Aspects of the reservoir competence of four rodents for the Lyme disease spirochete, Borrelia burgdorferi, were evaluated in California. Rodents were live-trapped and ear-punch biopsies were cultured during each season. A second set of biopsies was cultured from representative individuals after 2-3 weeks of captivity and the results of culturing biopsies taken on both dates were compared with the results of feeding Ixodes pacificus larvae on hosts xenodiagnostically. The prevalence of infections did not differ significantly between dusky-footed woodrats (Neotoma fuscipes) and California kangaroo rats (Dipodomys californicus) nor among seasons. Combined results of the three tests showed that 85.7% of dusky-footed woodrats (n = 21) and 78.6% of California kangaroo rats (n = 14) were infected with B. burgdorferi. In contrast, only 22.2% of brush mice (Peromyscus boylii) (n = 14) and 7.1% of pinyon mice (P. truei) (n = 9) were infected. The sensitivity of culturing ear-punch biopsies as an assay for borrelial infection was significantly greater when biopsies were taken after a short period of captivity (0.89) rather than on the day of capture (0.52). Tick xenodiagnosis, in which I. pacificus was used as the vector, revealed borrelial infections in 90.3% of infected rodents. Spirochetes were observed in 37.7% of 239, 45.2% of 155, 60.0% of 10, and 7.1% of 14 cultures of nymphal I. pacificus fed as larvae on naturally infected woodrats, kangaroo rats, brush mice, and a pinyon mouse, respectively. The mean prevalence of infection in xenodiagnostic ticks varied significantly among host species with a greater proportion of ticks infected while feeding on woodrats and kangaroo rats than on mice. This study reconfirms previous reports that implicated woodrats and kangaroo rats as reservoirs of B. burgdorferi in California.

Animals↗
PubMed1997

Distribution, diversity, and host specificity of Bartonella in rodents from the Southeastern United States.

A number of Bartonella isolates were obtained from seven species of rodents sampled from 12 geographic sites representing the major biotic communities of the southeastern United States. Bartonella were isolated from the blood of 42.2% of 279 tested rodents. The highest prevalence of infection typically occurred among the most commonly captured species in the rodent community. Four phylogenetic groups, uniting 14 genotypic variants of Bartonella, were identified by sequence analysis of the citrate synthase gene. The level of sequence homology between genotypic groups varied from 88.8% to 96.4%, and the degree of homology among variants within groups was > or = 97%. Cotton rats (Sigmodon hispidus) harbored up to three phylogenetic groups of Bartonella at a single site, and Bartonella of two phylogenetic groups were isolated from a single rodent. All the Bartonella isolated from three species of Peromyscus clustered in a single distinct phylogenetic group, suggesting some host specificity may occur. Mouse ascitic fluids produced in BALB/c mice inoculated with Bartonella of three phylogenetic groups demonstrated high indirect fluorescent antibody (IFA) titers to homologous antigens. However, use of eight Bartonella antigens in an IFA test with sera from 394 wild-caught rodents resulted in either little or extremely low titers of antibody.

Animals↗
PubMed2001

Persistent infection in Neotoma fuscipes (Muridae: Sigmodontinae) with Ehrlichia phagocytophila sensu lato.

Dusky-footed wood rats (Neotoma fuscipes Baird) and two species of Peromyscus mice (P. maniculatus Wagner and P. truei Shufeldt) were collected over a 16-month period from three sites in Sonoma County, California. Blood was collected from 93 wood rats and 177 mice and serum or plasma was tested for seroreactivity with Ehrlichia phagocytophila sensu lato (also known as the human granulocytic ehrlichiosis agent). Thirty-five (37.6%) wood rats and 15 (8.5%) mice were seropositive. Positive Neotoma serology by site ranged from 9.4% to 62.1%. Polymerase chain reaction (PCR) testing for the Ehrlichia groESL heat shock operon was performed on all the seropositive and selected seronegative wood rats; 24 (68.6%) seropositive animals were PCR positive. Two seroconversions and no seroreversions were detected among 18 of the seropositive wood rats that were recaptured and tested multiple times (range = 2-6). Fourteen (77.8%) of the 18 were also PCR positive with six of these positive at every testing point (range = 2-6). One wood rat remained serologically and PCR positive in six specimens collected over a 14-month period. One male of 84 questing adult Ixodes pacificus Cooley & Kohls collected was PCR-positive for E. phagocytophila. Borrelia burgdorferi, the agent of Lyme disease, was cultured from ear punch biopsies from six of seven E. phagocytophila seropositive and one of four seronegative wood rats.

Animals↗
PubMed1976

Adiaspiromycosis in the Franklin's ground squirrel, Spermophilus franklini, and pika, Ochotona princeps, from Alberta, Canada.

Pulmonary adiaspiromycosis due to Emmonsia crescens was diagnosed in three of six Franklin's ground squirrels (Spermophilus franklini) captured in Rochester, central Alberts, Canada in the summer of 1971, and in one of 240 pikas (Ochotona princeps) collected in southwestern Alberta in 1969. Granulomas measuring 0.5 to 1 mm in diameter were found in both lungs. These granulomas contained adiaspores measuring 60 to 400 mum in diameter. The disease was not found in six Franklin's ground squirrels collected in 1964, nor in 10 white-footed mice (Peromyscus maniculatus), one porcupine (Erethizon dorsatum), and 270 snowshoe hares (Lepus americanus) from the Rochester area. Lungs from an additional 17 hares from Alaska and 25 from New Brunswick and 96 pikas from Colorado were also examined but no adiaspores were found.

Alberta↗
PubMed1976

Prevalence of cuterebrid parasitism among woodmice in Virginia.

Botfly infestation was analyzed in 1319 small mammals from varied habitats and elevations in upland Virginia, 1972-1974. Adult Cuterebra fontinella were reared from bots infesting the woodmouse (Peromyscus leucopus). Of 651 woodmice, 199 (30.6%) were infested at least once. The season of bot infestation extended from May through November of all years, with peak prevalence (mean 42.2%) in August. Infestation in woodmice was general over a 2000 km2 study area during peak months. Significantly greater prevalence (P less than 0.001) was seen in forested and brushy habitat (39.9%) compared with old fields (2.6%). Higher prevalence (P less than 0.01) was found in males than in females, and in postjuveniles compared to adults. Greatest overall prevalence (39.1%) was in postjuvenile males. Most warble sites (98%) were inguinal, and observations suggested that many infested adults were non-reproductive. Mean burden (1.27) was independent of host age, sex, habitat, and month of capture. Multi-infestations occurred in 23% of the affected mice; maximum burden was six bots. Botflies were absent or negligible in sympatric deermice (P. maniculatus) and twelve other species of rodents and shrews.

Age Factors↗
PubMed1976

Prevalence of Bordetella bronchiseptica in certain central Iowa.

Bordetella bronchiseptica was isolated from 6 of 13 short-tailed shrews (Blarina brevicauda) and 1 of 47 house sparrows (Passer domesticus) trapped in the vicinity of a swine Bordetella rhinitis experimental area. The organism was found in four of 50 foxes (Vulpes fulva), 2 of 36 opossums (Didelphis marsupialis) and 1 of 37 raccoons (Procyon lotor) trapped in the Ames, Iowa area. This bacterium was not culturally isolated from 14 deer mice (Peromyscus maniculatus), 64 house mice (Mus Musculus), 10 masked shrews (Sorex cinereus) and 54 starlings (Sturnus vulgaris).

Animals↗