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Biomedical subjects

I K Barker

Publications and source records attributed to I K Barker.

At least 55 records · Page 3Linked to original sources
PubMed1993

The groundhog tick Ixodes cookei (Acari: ixodidae): a poor potential vector of Lyme borreliosis.

Evidence for infection with the spirochete, Borrelia burgdorferi, was sought in Ixodes cookei and in groundhogs (Marmota monax) in southern Ontario, Canada, and ticks fed on experimentally inoculated hosts were examined for the spirochete. Borrelia burgdorferi was not detected by immunofluorescent examination of 110 larval, nymphal or adult I. cookei collected from the environment, or taken from humans and other animals. Three groundhogs inoculated with B. burgdorferi developed titers of 1:20 to 1:80 by the indirect immunofluorescent antibody test, but B. burgdorferi was not isolated from the spleens, kidneys, or urinary bladders of these animals. One of 30 wild groundhogs had an antibody titer of 1:20 to B. burgdorferi. Three (5%) of 59 I. cookei larvae fed on B. burgdorferi-infected hamsters became infected, in comparison with 23 (28%) of 82 I. dammini larvae fed on the same hosts. Borrelia burgdorferi was present in 5%, 16% and 4% of molted I. cookei nymphs fed on infected hamsters, rats or a groundhog, respectively; prevalences of infection in I. dammini fed on the same hosts were significantly (P < 0.05) higher (45%, 36%, and 23%, respectively), as was the intensity of infection. A naive groundhog on which I. cookei nymphs from an infected cohort fed did not become infected with B. burgdorferi, but it is uncertain whether an infected tick engorged on the experimental host. Ixodes cookei seems to be an inefficient vector of B. burgdorferi, and is unlikely to be significant in nature. Groundhogs are potential wildlife reservoirs of B. burgdorferi, based on their capacity to transmit infection to I. dammini.

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PubMed1992

Distribution of the Lyme disease vector, Ixodes dammini (Acari: Ixodidae) and isolation of Borrelia burgdorferi in Ontario, Canada.

Ixodes dammini Spielman, Clifford, Piesman & Corwin was confirmed at Long Point, Lake Erie, Ontario, on small mammals and white-tailed deer and by dragging for ticks. Mean intensities of up to 16.2 larvae and 2.1 nymphs were found on Peromyscus leucopus (Rafinesque), with an overall prevalence of infestation up to 92%. Adult I. dammini (101.6 +/- 77.63) (mean +/- SD) were found on 8 white-tailed deer, Odocoileus virginianus (Zimmerman). The seasonal pattern of recovery of ticks from hosts and the environment resembled that described elsewhere. I. dammini was not found on 952 small mammals trapped at 25 other localities throughout Ontario, although other ticks (Derma-centor variabilis (Packard), Ixodes angustus Neumann, I. marxi Banks, I. muris Bishopp & Smith) were encountered sporadically. I. dammini is not widespread or common in Ontario other than at Long Point. Borrelia burgdorferi was isolated from 10 of 151 P. leucopus; from larval and nymphal I. dammini; and from nymphal and adult D. variabilis, all from Long Point. B. burgdorferi was not recovered from 116 small mammals from localities other than Long Point. Seropositive P. leucopus (indirect fluorescent antibody test titer > or = 1:20) were common (up to 30% prevalence in July 1988, n = 23) on Long Point. Where I. dammini was not found, the prevalence of seroreactors among Peromyscus was 0 (15 sites), < 12% (5 sites), and 29% (1 site); seroprevalence at 1:20 could not be calculated for a further 4 sites examined in 1987. Antibody to B. burgdorferi was also detected in other small mammals at some sites. Such antibody was interpreted as possibly cross-reacting or caused by direct transmission.

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PubMed1991

Apparent incompetence of Dermacentor variabilis (Acari: Ixodidae) and fleas (Insecta: Siphonaptera) as vectors of Borrelia burgdorferi in an Ixodes dammini endemic area of Ontario, Canada.

From April to October 1990, white-footed mice, Peromyscus leucopus (Rafinesque), were examined for ectoparasites on Long Point, Ontario, the only endemic area for Ixodes dammini Clifford, Spielman, Piesman & Corwin and Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner known in Canada. Larval and nymphal I. dammini and Dermacentor variabilis (Packard), and adult fleas Orchopeas leucopus (Baker), Epitedia wenmanni (Rothschild), and Ctenophthalamus pseudagrytes Baker were common on trapped mice. Questing ticks were collected by dragging, near the sites of mouse trapping, from April to November 1990. Indirect immunofluorescent assay established that 58.3% of adult, 17.3% of nymphal, and 0.15% of larval I. dammini questing at Long Point were infected with B. burgdorferi, indicating that infected mammalian reservoir hosts are common. None of 593 adult, 2 nymphal, and 4 larval D. variabilis collected while questing were infected; and only 1 of 322 fleas (O. leucopus) removed from white-footed mice was infected. The fact that no unfed adult D. variabilis and only one flea were infected, in a situation where the probability of exposure of hematophagous ectoparasites is moderately high, suggests that this species of tick and the fleas examined are poor vectors for the Lyme disease spirochete.

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PubMed1991

Cutaneous herpesvirus infection in a mallard duck (Anas platyrhynchos).

Investigations of mortalities involving wild mallard ducks (Anas platyrhynchos) revealed the presence of a herpesvirus associated with skin lesions on the plantar surface of the foot web of one duck. Ultrastructurally, the paracrystalline arrays of viral core particles and unencapsidated nucleoids in the nucleus, and the enveloped viruses in cytoplasmic vacuoles are compatible with a herpesvirus. This appears to be the first report of cutaneous lesions in a mallard duck attributable to a herpesvirus. Whether this lesion is due to duck virus enteritis (DVE), suggesting that cutaneous shedding is possible, or due to another uncharacterized herpesvirus of ducks is unclear.

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PubMed1991

Coccidiosis in common wombats (Vombatus ursinus).

Eimeria arundeli is a widespread coccidian parasite of the common wombat (Vombatus ursinus), and has been considered to be nonpathogenic. We describe disease in two captive juvenile wombats ascribed to infection with E. arundeli. One animal had diarrhea, the second had mucoid soft feces and lost weight over several weeks prior to death. Masses of coccidial gametocytes in hypertrophic cells in the lamina propria distended villi, causing grossly visible raised pale thickened regions over extensive areas of the mucosa of the small intestine in both animals. Neutrophils infiltrated affected mucosa, and there was an inflammatory exudate into the intestinal lumen in case one. In case two, neutrophils infiltrated the lamina propria of villi focally, crypts were distended by necrotic debris, and epithelium on villi was extremely attenuated. No bacterial pathogens were isolated from lung and intestine in case one; case two was not cultured. Oocysts consistent with E. arundeli were present in large numbers in floatations of diarrheic feces in both cases.

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PubMed1990

Failure to maintain interspecific pregnancy after transfer of Dall's sheep embryos to domestic ewes.

Over a 3-year period, 32 Dall's sheep (Ovis dalli dalli) embryos were transferred into 24 domestic sheep (O. aries) recipients and 4 were transferred into 2 Dall's sheep recipients. In the first year, none of the 10 O. aries recipients was diagnosed pregnant. In the following 2 years, 9 (37%) of the domestic sheep recipients were pregnant on Day 18, 8 (33%) on Day 40, 6 (25%) on Day 90 and 4 (16%) on Day 120; 1 aborted at Day 125 and another at Day 145. Pregnancies were established only in ewes that had previously been recipients of Dall's sheep embryos. The 2 remaining pregnant sheep were treated with progesterone from Day 125 until the fetuses were determined to be dead at Day 145. Both of the Dall's sheep recipients (Year 2) established pregnancies; 1 live Dall's sheep lamb was born 174 days after mating. No differences in serum progesterone, oestrone, prostaglandin F-2 alpha metabolites or cortisol concentrations could be detected during pregnancy between recipients carrying Dall's sheep embryos, recipients receiving progesterone treatment or domestic ewes carrying domestic sheep pregnancies. Six fetuses were necropsied (1 at Day 125 and 5 at Day 145-146): all fetuses were premature and had various degrees of hydranencephaly. No significant differences were found when cotyledon numbers were compared among domestic ewes carrying Dall's sheep lambs. Dall's sheep ewes lambing naturally and domestic ewes lambing naturally. These results demonstrate that the transfer of Dall's sheep embryos to domestic ewes results in the establishment but subsequent loss of pregnancy and that these losses occur throughout gestation.

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PubMed1990

A morphometric study of the canine colon: comparison of control dogs and cases of colonic disease.

The microstructure of the canine colon was described morphometrically. The artifacts induced by administration of enemas and biopsy technique were studied by comparing biopsy specimens to tissues obtained at necropsy from 15 normal dogs. Biopsies from control dogs and clinical cases of colonic disease were then evaluated quantitatively, and histological abnormalities which might clarify mechanisms underlying large bowel dysfunction in the dog were sought. In control dogs, gland length and diameter, epithelial, goblet cell and mucosal mast cell numbers, and intraepithelial lymphocyte and mitotic indices were remarkably uniform throughout the colon. Minor variations were found in the proximal and distal regions of the colon. An apparent shortening of glands, and a reduction in mucous goblets and intraepithelial lymphocytes in biopsies were attributed to suboptimal orientation and irritation caused by enemas. The only significant difference from controls identified by morphometric analysis of biopsies from clinical cases was fewer epithelial cells lining longitudinal sections of glands. It was concluded that failure to identify morphometric variations in the colonic mucosa of clinical cases might reflect either a biased, homogeneously mild clinical syndrome in this group, or the possibility that in many of the clinical cases, a functional rather than physical abnormality was involved. The proprial inflammatory cell population was not examined quantitatively; further investigation of this component is merited.

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PubMed1989

Host-parasite associations of Eimeria spp. (Apicomplexa:Eimeriidae) in kangaroos and wallabies of the genus Macropus (Marsupialia:Macropodidae).

Faecal samples from 514 kangaroos and wallabies representing 12 species of the genus Macropus were examined for oocysts of Eimeria spp. Six species of Eimeria were redescribed from their type hosts, and on the basis of finding homologous oocysts in the faeces of other Macropus spp., host ranges for these coccidia were extended. Eimeria hestermani Mykytowycz, 1964 is redescribed from M. giganteus (eastern grey kangaroo) and is described from M. fuliginosus (western grey kangaroo), M. rufogriseus (red-necked wallaby), M. dorsalis (black-striped wallaby), and M. eugenii (tammar wallaby). E. toganmainensis Mykytowycz, 1964 is redescribed from M. rufus (red kangaroo) and the host range is extended to M. giganteus, M. fuliginosus, M. rufogriseus and M. eugenii. E. wilcanniensis Mykytowycz, 1964 is redescribed from M. rufus, and the host range is extended to M. giganteus, M. fuliginosus and M. robustus (euro or wallaroo). E. macropodis Wenyon & Scott, 1925 is redescribed from M. rufogriseus, and is described from M. giganteus, M. fuliginosus, M. rufus, M. irma (western brush wallaby), M. parryi (whip-tailed wallaby), M. dorsalis, M. eugenii, and M. parma (parma wallaby). E. fausti Yakimoff & Matschoulsky, 1936, E. cunnamullensis Mykytowycz, 1964 and E. purchasei Mykytowycz, 1964 are synonymized with E. macropodis. E. marsupialium Yakimoff & Matschoulsky, 1936 is redescribed from M. giganteus, and from M. fuliginosus. E. gungahlinensis Mykytowycz, 1964 is redescribed from M. fuliginosus, and from M. giganteus. Seven new species of Eimeria are described. E. flindersi, new species, is described from M. eugenii, M. rufogriseus, and M. antilopinus (antilopine wallaroo). E. prionotemni, new species, is described from M. eugenii, M. parryi, M. rufogriseus, M. agilis (agile wallaby) and M. dorsalis. E. mykytowyczi, new species, is described from M. agilis, M. antilopinus, and M. parryi. E. parryi, new species, is described from M. parryi. E. yathongensis, new species, is described from M. fuliginosus and M. giganteus. E. parma, new species, is described from M. parma, and E. desmaresti, new species, is described from M. rufogriseus. E. kogoni Mykytowycz, 1964, and E. rufusi Prasad, 1960 are considered species inquirendae. The host-parasite associations of these coccidia, and of similar species of Eimeria in other genera of Macropodoid marsupials, are discussed in relation to the postulated phylogeny of the hosts.

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PubMed1989

Observations on the lungworm, Pneumostrongylus calcaratus, in impala (Aepyceros melampus) from Swaziland.

The lungworm, Pneumostrongylus calcaratus, was found in 85% (164 of 193) of impala (Aepyceros melampus) collected in Mlawula Nature Reserve in Swaziland. Infection was confirmed at 4.5 mo of age, and the prevalence increased to 100% at 11 mo, with a prevalence of 98% in animals greater than 1 yr of age. Pneumostrongylus calcaratus was usually found in firm, tangrey nodules along the lobar borders of the lungs, although an extensive granulomatous pneumonia with miliary caseous abscesses and calcified nodules was observed in some older animals. In the primary infection in lambs, adult parasites, larvae and eggs were observed in the alveoli and bronchioles within the nodule. There was peribronchial and perivascular mononuclear cuffing, with infiltration of mononuclear cells in the alveolar septum in the vicinity of worms. In lesions in older animals, there was local consolidation with macrophages and giant cells, and foci of parenchymal necrosis associated with degenerating eosinophils, which appeared to lead to the formation of eosinophilic granulomas. Resolving lesions caused interstitial fibrosis, with mineralized nodules. Pneumostrongylosis does not appear to pose a significant threat to the health of impala in Swaziland.

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PubMed1988

A method for reproducing fatal idiopathic colitis (colitis X) in ponies and isolation of a clostridium as a possible agent.

Severe colitis was induced in two ponies after oral pretreatment with clindamycin and lincomycin, followed by intestinal content from two horses which had died from naturally-occurring idiopathic colitis. Two ponies treated with antibiotic alone, and two ponies treated with intestinal content alone, were unaffected. In a further study, three ponies treated on separate occasions with lincomycin, administered orally, died or were destroyed 67 to 72 h after initial treatment. No established salmonella, yersinia or campylobacter pathogens were isolated from these ponies, but a clostridium closely resembling Clostridium cadaveris was isolated as the predominant clostridium from them all and from the colonic content of one of six horses which died from naturally-occurring idiopathic colitis. It was not isolated from six horses with non-fatal diarrhoea. This clostridium is a candidate as an agent of some cases of fatal colitis in horses.

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PubMed1988

An epizootic of Mycoplasma ovipneumoniae infection in captive Dall's sheep (Ovis dalli dalli).

In late spring of 1986, 10 of 23 Dall's sheep (Ovis dalli dalli) at the Metropolitan Toronto Zoo were moved to a new exhibit, where all developed severe respiratory signs refractory to anthelmintic and antibiotic therapy. In July, two animals died with chronic active bronch-pneumonia, and a third was euthanized because of pneumonia several months later. Bacteria were not isolated from the lungs of the first, steptococci and Pasteurella hemolytica were isolated from the other two, respectively; Mycoplasma ovipneumoniae was isolated from both. Pulmonary lesions in all three sheep were consistent with Mycoplasma sp. infection. Nasal swabs of the remaining animals yielded no consistent bacterial isolates; however, four of eight sheep were positive for M. ovipneumoniae. Viral cultures yielded an as yet unidentified herpesvirus. Sheep in the original and new herds had no serologic titers to parainfluenza-3, equine viral rhinopneumonitis, or infectious bovine rhinotracheitis, and had variable titers against bovine respiratory syncytial virus. No titers against M. ovipneumoniae were present in 13 sheep still in the original exhibit, but titers varied from 1:32 to 1:256 in eight pneumonic sheep. Sera taken from three sheep before or early in the outbreak were all negative for antibody to M. ovipneumoniae. Two of the affected Dall's sheep had been in contact with domestic sheep in the winter of 1985-1986, and M. ovipneumoniae was subsequently cultured from the domestic flock. Exposure to a new pathogen, and environmental and social stress in a new exhibit may have resulted in this severe disease in Dall's sheep.

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PubMed1988

Healing of cutaneous wounds in the common garter snake (Thamnophis sirtalis).

Healing of cutaneous wounds was studied in groups of common garter snakes (Thamnophis sirtalis) held at 13.5 degrees C, 21 degrees C and 30 degrees C. Linear unsutured incisions and circular excisional wounds were evaluated two, five, and ten days after surgery, while linear sutured and unsutured incisions and circular and square excisional wounds were studied three and six weeks after wound production. The sequence of events during healing was the same for all experimental situations. The epithelial margins of the wounds moved freely over exposed epaxial muscle until an exudate of fibrin and inflammatory cells caused adhesion. Heterophils and macrophages were present two days after wounding. Heterophils were present throughout the wound while macrophages were concentrated in areas containing fibrin and proteinaceous exudate. Fibroblasts moved laterally into the wound from the adjacent dermis producing a flat dermal scar oriented parallel to the wound surface. Epithelial cell hypertrophy and hyperplasia occurred in a zone extending up to 1.5 mm from the margin of the wound. A tongue of flattened epithelial cells extended across the wound surface, mingling with the superficial crust and migrating over eosinophilic fibrillar material. Maturation of the new epithelium, indicated by formation of a distinct basal layer, rounding of superficial cells and keratin production, began at the wound margins before the epithelial spurs linked. The epithelium over healed wounds appeared normal, but the dermis did not reorganize to form scales. Reptilian and mammalian healing differ in the character of the inflammatory reaction, the pattern of fibroplasia, and the interaction between epithelial and dermal repair.

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PubMed1988

The effect of ambient temperature and type of wound on healing of cutaneous wounds in the common garter snake (Thamnophis sirtalis).

The effects of ambient temperature (13.5 degrees C, 21 degrees C, 30 degrees C) and type of wound on healing of skin wounds were evaluated in common garter snakes (Thamnophis sirtalis). Linear unsutured incisions and circular excisional wounds were evaluated grossly and microscopically in three snakes held at each temperature at each of two, five and ten days after surgery. Linear sutured and unsutured incisions and circular and square excisional wounds were similarly evaluated three and six weeks after wound production in groups of six snakes held at each temperature. The rates of stabilization of wound margins, scab formation, migration and maturation of the regenerating epithelium, resolution of dermal inflammation, and fibroplasia varied directly with temperature. The inflammatory reaction to wounding was similar in character and intensity in snakes held at all three temperatures two days after surgery. Unsutured linear incisions, compared to sutured incisions, tended to have more rapid epithelial maturation and a less intense inflammatory response. Healing of square and circular excisional wounds was similar; contraction of round wounds was slightly more irregular and, at a few observations, dermal maturation was slower and inflammation more widespread. It was concluded that healing of skin wounds can be accelerated by holding reptiles at the upper end of their voluntary temperature range. Wounds, if possible, should be created along the axis of lines of skin tension. Suturing small incisional wounds may not be advantageous.

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