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Biomedical subjects

R G McLean

Publications and source records attributed to R G McLean.

At least 37 records · Page 2Linked to original sources
PubMed1994

Serologic surveillance for the Lyme disease spirochete, Borrelia burgdorferi, in Minnesota by using white-tailed deer as sentinel animals.

To determine the effectiveness of white-tailed deer as sentinel animals in serologic surveillance programs for Borrelia burgdorferi, we performed enzyme-linked immunosorbent assay (ELISA) and Western immunoblotting analyses on 467 deer serum samples. The seropositivity rate in the ELISA was 5% for the 150 samples collected at the three sites in which the tick Ixodes scapularis was absent. The three sites with established I. scapularis populations had a seropositivity rate of 80% for 317 samples. Results were similar for two closely situated sites, one with an established I. scapularis population and one without; these sites were only 15 km apart. Rates of seropositivity were significantly higher in yearling and adult deer than in fawns. The mean numbers of bands seen on Western immunoblots were 3.0 for samples negative in the ELISA and 13.8 for samples positive in the ELISA; all of these samples were collected from sites in which I. scapularis was established. At sites in which I. scapularis was absent, the mean numbers of bands seen were 1.6 for samples negative in the ELISA and 8.2 for samples positive in the ELISA. There were 14 different B. burgdorferi antigens that reacted with more than 50% of the ELISA-positive samples from areas with I. scapularis. A 19.5-kDa antigen reacted with 94% of the ELISA-positive samples. Reactivity against OspA and OspB was weak a infrequent (2%). Serologic analysis of white-tailed deer sera appears to be an accurate and sensitive surveillance method for determining whether B. burgdorferi is present in specific geographic locations.

Animals↗
PubMed1994

Isolation of pseudorabies (Aujeszky's disease) virus from a Florida panther.

Pseudorabies virus was isolated in cell culture from the brain tissue of a 3.5-year-old male Florida panther (Felis concolor coryi). The virus was not isolated from other tissues collected at necropsy. Based upon a nested polymerase chain reaction (PCR), the virus was determined to have the classical wild-type virulent genotype, glycoprotein I+ (gI+) and thymidine kinase+ (TK+).

Animals↗
PubMed1994

Arboviruses in water birds (Ciconiiformes, Pelecaniformes) from Florida.

Sera from 360 ciconiform and pelecaniform birds collected in Florida (USA) from 1974 to 1990 were tested for serum neutralizing (SN) antibodies to eastern equine encephalitis (EEE), St. Louis encephalitis (SLE), and Everglades (EVE) viruses. Serum neutralizing antibodies to EEE virus were detected in 2%, to SLE virus in 7%, and to EVE virus in none of the samples. Pelecaniform birds (16%) had a higher antibody prevalence (P < 0.02) for SLE virus than did ciconiform birds (5%). Virus could not be isolated from 67 samples. Nestling birds with SN antibodies to both EEE and SLE viruses were found in both fresh water and marine colonies. Antibodies were more prevalent in adult and fledged juvenile birds than in nestlings.

Age Factors↗
PubMed1994

Vector competence of Aedes albopictus from Pine Bluff, Arkansas, for a St. Louis encephalitis virus strain isolated during the 1991 epidemic.

The vector competence of Aedes albopictus from Pine Bluff, AR, was assessed for a St. Louis encephalitis (SLE) virus strain isolated during the 1991 epidemic. Aedes albopictus were fed on hamsters with viremia levels of 10(4.6)-10(4.9) Vero cell plaque-forming units (PFU)/ml. At 7 and 15 days postbloodfeeding, transmission trials were conducted using individual suckling mice. Three of 313 Ae. albopictus were determined to be infected with SLE virus with titers of 10(6.3)-10(7.0) PFU/mosquito. At 15 days postbloodfeeding, one of 209 Ae. albopictus that refed transmitted virus resulting in a 15-day population transmission rate of 0.5%. The infection threshold (i.e., the amount of virus required to infect from 1 to 5% of mosquitoes) was determined to be approximately 10(2.3) PFU/mosquito. Virus inoculated intracoelomically into Ae. albopictus replicated and reached mean titers above 10(6.0) PFU/mosquito on day 6. The combination of low susceptibility to infection and a mammalophilic bloodfeeding pattern suggests that Ae. albopictus is unlikely to play a significant role in SLE transmission.

Aedes↗
PubMed1993

Susceptibility parameters of Aedes albopictus to per oral infection with eastern equine encephalitis virus.

Aedes albopictus (Skuse) mosquitoes were fed on snowy egrets, Egretta thula (Thayer and Bangs), that had been infected by subcutaneous inoculation of eastern equine encephalitis (EEE) virus. Freshly fed mosquitoes were frozen and tested to determine how much virus they had ingested. Other fed mosquitoes from the same lots were incubated for 7 d at 27 degrees C before testing. Seven lots of Ae. albopictus fed on viremic birds. Based on average amounts of virus ingested and day 7 virus infection rates in mosquitoes from the same lots, the amount of virus required to infect 50% of the mosquitoes was calculated to be 10(2.8) Vero cell plaque-forming units (PFU). The infection threshold (i.e., the amount of virus required to infect from 1 to 5% of mosquitoes) was determined to be < or = 10 PFU per blood meal. These parameters indicate that Ae. albopictus is sufficiently susceptible to infection with EEE virus to enable it to acquire infectious doses from a wide variety of viremic birds and possibly from equines.

Aedes↗
PubMed1993

Ecology of porcupines (Erethizon dorsatum) and Colorado tick fever virus in Rocky Mountain National Park, 1975-1977.

The involvement of porcupines, Erethizon dorsatum (L.), in the ecology of Colorado tick fever (CTF) virus in Rocky Mountain National Park was investigated from 1975 to 1977. Porcupine dens and feeding activity were found mostly on rocky knolls or on south-facing slopes within open stands of the montane coniferous forest, and 20 adult porcupines were trapped or captured by hand at those locations. An average of 24.6 +/- 5.4 adult Dermacentor andersoni Stiles ticks were found per animal (annual range, 17.5-31.4 ticks). The minimum CTF virus infection rate of the ticks removed from porcupines varied from 129 to 257, whereas for questing adult D. andersoni ticks from the same geographic area was 205 in 1976. No virus was isolated from the 20 animals, but 85% had neutralizing antibody against CTF virus. Porcupines utilize the same habitats described for the CTF ecosystem in Rocky Mountain National Park and appear to be an important host for adult D. andersoni.

Animals↗
PubMed1993

Serologic analysis of white-tailed deer sera for antibodies to Borrelia burgdorferi by enzyme-linked immunosorbent assay and western immunoblotting.

White-tailed deer serum samples were collected in the Minneapolis-St. Paul, Minn., metropolitan area during the fall and winter months from 1989 to 1992 and analyzed for antibodies to Borrelia burgdorferi, the etiologic agent of Lyme borreliosis. Ninety-eight percent of the serum samples were collected from regions where currently the vector tick, Ixodes dammini, is nonexistent. Antibodies to B. burgdorferi were detected in 2.2% of 508 samples by enzyme-linked immunosorbent assay, and their presence was confirmed by Western immunoblot analysis. Western immunoblotting yielded mean numbers of reactive bands of 0.1 and 6.0 for samples that were negative and positive for antibodies by enzyme-linked immunosorbent assay, respectively. The molecular weights of the antigens in many of the reactive bands from positive samples were similar to the molecular weights of antigens reactive with samples from humans with Lyme borreliosis. An antibody response to the major outer surface proteins A and B was not detected. Serologic analysis of deer sera may provide a valuable method for surveillance programs designed to monitor the spread of B. burgdorferi in nature.

Animals↗
PubMed1993

Isolation and characterization of Borrelia burgdorferi from blood of a bird captured in the Saint Croix River Valley.

Field investigations were conducted to further evaluate the role of birds in the maintenance and dissemination of Borrelia burgdorferi. Blood specimens were taken from 39 passerine birds of 17 species captured during June 1991 at the Saint Croix National Riverway in Wisconsin, and one isolate, WI91-23, was cultured from an adult song sparrow (Melospiza melodia). This isolate was shown to be infectious for Peromyscus leucopus and Mesocricetus auratus (golden hamster). Isolate WI91-23 was confirmed as B. burgdorferi by immunofluorescence assay by using species-specific anti-OspA monoclonal antibodies H3TS and H5332 and anti-OspB antibody H5TS. Isolate WI91-23 was compared with Borrelia anserina Es, Borrelia hermsii MAN-1, and other B. burgdorferi strains (ATCC 53210, CT-1, and Catharus fuscescens [veery] liver 10293). Pulsed-field gel electrophoresis of in situ-lysed spirochetes revealed that the DNA plasmid profile of WI91-23 was most similar to those of plasmids from B. burgdorferi and most different from those of plasmids from B. anserina and B. hermsii. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis indicated that the protein profile of WI91-23 was like that of other B. burgdorferi strains studied, with dominant proteins corresponding to OspA and OspB, and that it differed from the protein profiles of B. anserina and B. hermsii. These findings indicate that passerine birds may serve as reservoirs for B. burgdorferi.

Animals↗
PubMed1993

Avian hosts of St. Louis encephalitis virus in Pine Bluff, Arkansas, 1991.

An investigation of the extent of St. Louis encephalitis (SLE) virus activity in the avian population in Pine Bluff, Arkansas was conducted from August 30, 1991 through September 5, 1991, following an SLE epidemic that resulted in 25 human cases. A total of 363 birds of 33 species were captured with ground-level mist nets at four sites along the northern edge of the city. No viruses were isolated from the serum of these birds, but 91 birds (25%) of 11 species had detectable neutralizing antibody against the TBH-28 strain of SLE virus in the constant-virus, serum-dilution, plaque-reduction neutralization test in Vero cell culture. No antibody to eastern equine encephalitis virus was detected. The prevalence of antibody to SLE virus varied among the sites from 11% to 44%, but the prevalence at each site was influenced by the avian species composition. The two most abundant species captured in the city, the American robin (43%) and house sparrow (42%), also had the highest prevalence of antibody. Nine other bird species were serologically positive but at significantly lower rates than for the abundant species. The antibody prevalence was higher in immature birds (27%) than in adult birds (15%), but the antibody titers were higher in adult birds than in immature ones. The overall SLE antibody prevalence and the prevalence for house sparrows were significantly higher than the average prevalence for avian hosts studied during previous SLE epidemics. Therefore, house sparrows would be a good choice for a local sentinel species.

Animals↗
PubMed1993

Experimental infection of the eastern chipmunk (Tamias striatus) with the Lyme disease spirochete (Borrelia burgdorferi).

Lyme disease, caused by the spirochete Borrelia burgdorferi, is endemic in the northeast, north-central, and Pacific coastal states of the United States. The eastern chipmunk (Tamias striatus) is found throughout the disease-enzootic regions except along the Pacific coast, and may serve as an important reservoir host in some locations. To characterize their potential as a host, 11 adult chipmunks were inoculated with 10(5) spirochetes from strains of B. burgdorferi isolated from Peromyscus leucopus and Ixodes scapularis in a hyperendemic area of Westchester County, New York (USA). All inoculated chipmunks became infected. Spirochetemias were detected by isolating spirochetes in Barbour-Stoenner-Kelly media in eight of eight chipmunks, and lasted for 2 to 5 days. Spirochetes were isolated from the ears of all animals, starting at 1 wk and for < or = 4 mo, and from various internal organs at 133 days post-inoculation. Laboratory-reared larval I. scapularis ticks became infected with spirochetes after feeding on two of the inoculated chipmunks.

Animals↗
PubMed1992

Oral colon transit scintigraphy using indium-111 DTPA: variability in healthy subjects.

Oral colon transit scintigraphy using indium-111 diethylene-triamine-pentaacetic acid was performed in 41 healthy subjects (22 females, 19 males) to determine variability with age and sex and to define normal ranges. Repeat studies were performed in 10 females and 9 males to assess intra-subject variability. Females showed slightly but significantly slower colonic transit than men and slightly greater intra-subject variability. There was no correlation between age and colonic transit. The results have implications for the definition of normal ranges.

Adult↗
PubMed1992

Borrelia burgdorferi infection in white-footed mice (Peromyscus leucopus) in hemlock (Tsuga canadensis) habitat in western Pennsylvania.

White-footed mice (Peromyscus leucopus) were captured and their tissues sampled from 27 sites in seven counties of western Pennsylvania in 1990 for isolation and identification of Borrelia burgdorferi. Two hundred sixty mice were captured from which there were 27 isolations. Significantly more mice were captured and significantly more isolations made from hemlock (Tsuga canadensis) habitat than from deciduous species forest. Hemlock habitat is sparse and focal but evidently increases winter survival of mice, and thus possibly results in increased infection rates in mice.

Animals↗
PubMed1992

Serologic survey for selected arboviruses and other potential pathogens in wildlife from Mexico.

During 1988 and 1989, a serologic survey of wildlife was conducted in northeastern Mexico to determine the presence, prevalence, and distribution of arboviruses and other selected disease agents. Eighty mammal specimens were tested. Antibodies to vesicular stomatitis-Indiana, Venezuelan equine encephalitis-Mena II, Rio Grande virus, and vesicular stomatitis-New Jersey were detected predominantly in small mammals. Deer and mouflon (Ovis musimon) had antibodies to bluetongue and epizootic hemorrhagic disease. Two species had serologic evidence of recent exposure to Francisella tularensis. A white-tailed deer (Odocoileus virginianus) had antibodies to Anaplasma marginale. All specimens tested for antibodies against Yersinia pestis and Brucella abortus were negative. Sera from 315 birds were tested for antibody against five equine encephalitis viruses and six avian pathogens. During 1988, antibodies to Venezuelan equine encephalitis-Mena II, Venezuelan equine encephalitis-TC83, St. Louis encephalitis, eastern equine encephalitis, and western equine encephalitis were detected in birds of several species. Antibodies to Pasteurella multocida and Newcastle disease virus were also detected. Birds from five species presented antibodies to Mycoplasma meleagridis. Specimens tested for M. gallisepticum, M. synoviae, and Chlamydia psittaci were negative. To the best of our knowledge, this survey represents the first serologic evidence of bluetongue, Cache Valley virus, epizootic hemorrhagic disease, Jamestown Canyon virus, vesicular stomatitis-Indiana, vesicular stomatitis-New Jersey, Rio Grande virus, and tularemia reported among wildlife in Mexico.

Animals↗
PubMed1992

Experimental inoculation of three arboviruses in black-bellied whistling ducks (Dendrocygna autumnalis).

Wild-caught, immature black-bellied whistling ducks (Dendrocygna autumnalis) were inoculated with eastern equine encephalitis (EEE), St. Louis encephalitis (SLE), or western equine encephalitis (WEE) virus. Susceptibility, duration and titer of viremia, and antibody response to these arboviruses were determined. Birds from all inoculated groups became viremic. Higher virus titers occurred in the EEE group but overall mean titers were not significantly different among experimental groups. All birds inoculated with EEE and SLE viruses developed antibodies, and six of seven ducks receiving WEE virus were seropositive. All seropositive ducks had antibodies for at least 59 days, when the study was terminated. The EEE group had significantly more seropositive ducks during more days than the WEE and SLE groups. Geometric mean antibody titers were significantly smaller in the WEE group when compared to the EEE and SLE groups. Control ducks did not develop viremia or antibodies. Gross and histopathologic lesions compatible with viral encephalitis were absent in all of nine ducks necropsied. Black-bellied whistling ducks can develop low and short-term levels of viremia sufficient to infect mosquitoes, but probably cannot contribute significantly to the transmission of EEE and SLE. They may serve as good indicators of virus activity.

Animals↗
PubMed1991

Venezuelan equine encephalomyelitis virus infection in and transmission by the tick Amblyomma cajennense (Arachnida: Ixodidae).

To assess a possible role of ticks as the maintenance host for epizootic strains of Venezuelan equine encephalomyelitis (VEE) virus, laboratory experiments were conducted to determine if ticks could become infected, maintain, and transmit the virus. Larval and nymphal Amblyomma cajennense (F.) and larval Dermacentor nitens Neumann ticks were exposed to epizootic VEE virus (Trinidad donkey strain) by allowing them to feed on viremic guinea pigs (strain 13). In A. cajennense, transstadial transmission was observed from larvae to nymphs and adults. Horizontal viral transmission to a mammalian host was accomplished by nymphs. Infection rates in nymphs and adults were 2% (42/2,750) and 4% (9/244), respectively, afer ingestion of virus as larvae. Virus was detected in A. cajennense adult ticks for up to 171 d after infection in the larval stage. A cajennense, exposed as nymphs, ingested virus but did not become infected (0/164 after 10 d after taking an infective bloodmeal). No virus was detected in D. nitens 7 d after exposure. These findings suggest that A. cajennense potentially could be involved in an interepizootic maintenance cycle of epizootic VEE viral strains.

Animals↗
PubMed1991

Comparison of oral iodine-131-cellulose and indium-111-DTPA as tracers for colon transit scintigraphy: analysis by colon activity profiles.

In 11 normal subjects and 11 patients with a clinical diagnosis of constipation, oral 131I-cellulose and 111In-DTPA were compared simultaneously as tracers for radionuclide colon transit scintigraphy. Visual assessment of the images revealed no differences between tracers. Quantitation was performed using total and segmental percent retention and the derived value of clearance half-time. In addition, profiles of the activity distribution along the length of the colon were generated and the mean position of the activity in the colon calculated. For all indices, the results were similar in both normal subjects and constipated patients when comparing tracers, although marked differences were present between normal subjects and constipated patients for each tracer. Indium-111-DTPA was easy to administer and dosimetry was more acceptable than for 131I-cellulose, especially in constipated patients. It is concluded that 111In-DTPA is the preferred tracer for oral colon transit scintigraphy.

Administration, Oral↗
PubMed1990

Isolation of Tete serogroup bunyaviruses from Ceratopogonidae collected in Colorado.

Two viruses were isolated from ceratopogonid midges collected in northern Colorado. Electron microscopy indicated that both isolates were bunyavirus-like. Indirect fluorescent antibody and serum dilution-plaque reduction neutralization tests showed that these isolates were members of the Tete serogroup, most closely related antigenically to Tete and Batama viruses but distinguishable from both and from each other. We suggest the name Weldona virus for these isolates. Antibody in both waterfowl and passerine birds in northern Colorado indicates the enzootic presence of these viruses in northern Colorado and raises unanswered questions about the introduction and establishment of Tete serogroup viruses in the Americas.

Animals↗