Lyme borreliosis in Ontario: determining the risks.
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Animals↗
Biomedical subjects
I K Barker
Publications and source records attributed to I K Barker.
Effects of delivery method on serological responses of bighorn sheep to a multivalent Pasteurella haemolytica supernatant vaccine.
The safety and efficacy of a remotely delivered multivalent Pasteurella haemolytica supernatant vaccine (serotypes A2 and T10) were examined in captive Rocky, Mountain bighorn sheep (Ovis canadensis canadensis). Twenty bighorn sheep were grouped according to baseline leukotoxin neutralizing antibody titers (< or =2 or >2 log2(-1)) and vaccination history (previously vaccinated or unvaccinated). Within these groups, animals were randomly assigned to one of two delivery treatments: hand injection (control) or biobullet implantation. All bighorns received a single dose from the same lot of vaccine (n = 10/treatment); four additional animals were injected intramuscularly with 0.9% saline as unvaccinated sentinels. Mild, transient lameness one day after hand injection or biobullet implantation was the only adverse effect. Serum neutralizing antibody titers to P. haemolytica leukotoxin differed between delivery treatments (P = 0.009) and among baseline titer/vaccination history groups (P = 0.013). Neutralizing titers were higher among hand-injected bighorns. Although neutralizing titers were lower among implanted bighorns than hand-injected controls at 1 wk (P = 0.002) and 2 wk (P = 0.021) after vaccination, seroconversion rates in response to implantation (6/10) and hand injection (9/10) did not differ (P = 0.303). Agglutinating antibody titers to T10 were high and did not vary over time or between delivery treatments. Agglutinating antibody titers to A2 in the hand-injected controls were not different (P > or = 0.07) than those in bighorns vaccinated with biobullet implantation. These data demonstrate that although hand injection elicits higher absolute titers, biobullet implantation may also stimulate effective antibody responses to P. haemolytica supernatant vaccine. Further evaluation of biobullet vaccination against pneumonic pasteurellosis in free-ranging populations of wild bighorn sheep is warranted.
Animals↗
Abundance of Ixodes scapularis (Acari: Ixodidae) larvae and nymphs in relation to host density and habitat on Long Point, Ontario.
Ixodes scapularis Say populations were evaluated within 4 habitats on Long Point, Ontario, from 1990 to 1992 to ascertain whether differences in density of mouse populations within and among habitats were correlated with that of immature I. scapularis populations. I. scapularis immatures were rarely collected by dragging within the cottonwood dune habitat. Significantly more larvae (P < or = 0.05) were collected by drag sampling within the maple forest habitat than in the oak savannah or white pine habitats for the 1989, 1990, and 1991 cohorts, whereas the size of the 1992 larval cohort did not differ significantly among these habitats. Significantly more nymphs were collected by dragging within the maple forest than in the other 2 habitats for all 4 cohorts. Nymphs from the 1989 and 1990 cohort were more abundant within the oak savannah than the white pine habitat, whereas the 1991 and 1992 cohorts were similar. With few exceptions, I. scapularis immatures were most prevalent on white-footed mice, Peromyscus leucopus (Rafinesque), captured within the maple forest > oak savannah > white pine > cottonwood dune, although differences were not significant in all years and in all habitats. The number of mice captured within the 4 habitats was not correlated with the number of I. scapularis larvae or nymphs infesting them. Likewise, the minimum number of mice alive was not significantly correlated with conversion indices of larvae to nymphs or nymphs to adults. Lack of association between mouse availability and relative size of subsequent cohorts of host-seeking ticks suggests that factors other than the size of the mouse populations were responsible for the observed differences in tick abundance among habitats.
Animals↗
Microclimate and habitat in relation to Ixodes scapularis (Acari: Ixodidae) populations on Long Point, Ontario, Canada.
The impact of microclimate and density of hosts for adult ticks on the density of Ixodes scapularis Say was evaluated within 4 habitats on Long Point, Ontario, from 1989-1992. During the period from May to September, mean weekly vapor pressure deficits were greater within the oak savannah and cottonwood dune habitats than at the maple forest and white pine habitats, which were similar. Vapor pressure deficit was likely the major factor affecting the survivorship of eggs and immature tricks in these habitats. Based on drag sampling, I. scapularis adults demonstrated peak activity in April and October of each year. The mean number of I. scapularis adults collected by dragging during the fall or in the spring did not differ significantly within each habitat. The mean number of adults collected also did not differ among tick cohorts within each habitat; however, significantly more adults were collected within the maple forest than in the white pine habitat. The mean number of I. scapularis adults per white-tailed deer, Odocoileus virginianus (Zimmerman), increased from 1989 to 1991 and then decreased in 1992. Significantly more adult I. scapularis infested deer were observed in 1990 than in 1989. Removal of deer in 1989 and 1990 resulted in a calculated decrease of > 100,000 fed female ticks. Although seasonal variation in microclimate within habitats was closely linked with tick survival and partly explains the differences in abundance of I. scapularis among habitats on Long Point, habitat utilization by deer was also a primary factor governing the local abundance of I. scapularis populations.
Animals↗
The 1992 epizootic of Newcastle disease in double-crested cormorants in North America.
In the summer of 1992, morbidity and mortality in juvenile double-crested cormorants (Phalacrocorax auritus; DCC) attributable to Newcastle disease virus (NDV) was observed for the first time in seven northern USA states and one Canadian province, and recurred in three western Canadian provinces. Based on clinical signs and laboratory diagnostic findings, DCC mortality from NDV occurred in 59 of the 63 nesting colonies and two of three non-colony sites investigated. An estimate of in excess of 20,000 DCC died, with mortality rates ranging from < 1 to 37% in Great Lakes colonies to 20 to 92% in Minnesota (USA) and North and South Dakota (USA) colonies. Sick juvenile white pelicans (Pelecanus erythrorhynchos) exhibiting signs similar to sick cormorants, and dead pelicans were observed in Minnesota and North Dakota. Mortality rates in pelican colonies were as high as in the adjacent cormorant colonies, but no cause for the mortality of an estimated 5,000 pelicans was determined. No evidence of NDV was found in other species nesting in proximity to affected cormorants. Although the source of the NDV infection is unknown in cormorants, the simultaneous onset of the epizootics in juvenile birds over a wide geographic area implies that the virus was acquired by adults prior to migration and was carried back to nest sites, exposing susceptible nestlings. The possible transmission of this virus from free-ranging wild birds to domestic poultry is a concern. Based on repeated epizootics in cormorants since 1990, NDV seems to be established in DCC.
Animals↗
Humoral response and protection from experimental challenge following vaccination of raccoon pups with a modified-live canine distemper virus vaccine.
Eight 8-wk-old raccoon pups (Procyon lotor) with maternal canine distemper virus (CDV) neutralizing antibodies (NAb) and 24 8-wk-old seronegative pups were administered a commercial modified-live CDV vaccine (Galaxy, D, Solvay Animal Health, Inc., Kitchener, Ontario, Canada). All 24 seronegative raccoons had detectable serum CDV NAb titers 14 days after the initial dose. Titers rose to maximum levels 4 wk post-vaccination. Mean titers for groups of vaccinated seronegative pups were maintained between 1:256 and 1:2,048 for the remainder of the 3 mo observation period. Geometric means of the serum CDV NAb titer of eight seronegative pups given a single vaccine dose at 8 wk of age did not differ significantly from those of eight pups that were given serial doses at 8, 12, and 16 wk of age, or from those of eight pups vaccinated once at 16 wk of age. Seven unvaccinated 8-wk-old raccoon pups used as controls remained seronegative throughout the trial. Seven out of eight 8-wk-old pups with maternal antibodies, vaccinated at 8, 12, and 16 wk of age, failed to develop a rise in their CDV NAb titers until at least 18 wk of age, 2 wk after the third vaccination. Titers in eight unvaccinated raccoons with maternal antibodies declined steadily to undetectable levels at 20 wk of age. A half-life of 10.55 days was calculated for maternally-derived CDV NAb in raccoon pups. Sixteen vaccinated raccoons were protected from clinical disease following experimental oronasal challenge with a virulent raccoon strain of CDV, 13 to 23 wk after vaccination. Serum CDV NAb titers at the time of challenge ranged from 1:12 to 1:384 and increased during the period of observation. Three of four unvaccinated seronegative raccoons used as controls failed to mount any detectable CDV NAb and were euthanatized after developing clinical signs of canine distemper 26, 29, and 30 days post-challenge (PC). Necropsies confirmed the diagnosis. The fourth control raccoon exhibited transient equivocal clinical signs, mounted a sluggish humoral response, but was clinically normal when euthanatized 42 days PC. In this raccoon, there was focal non-suppurative encephalitis with intranuclear inclusion bodies typical of CDV infection.
Animals↗
Tumors in wild adult raccoons from a suburban area.
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Adenoma↗
Eimeria species in the Pearson Island Rock Wallaby, Petrogale lateralis pearsoni.
Four species of previously described Eimeria were identified from oocysts present in the faeces of Pearson Island rock wallabies, Petrogale lateralis pearsoni from Pearson Island, South Australia. Eimeria petrogale and Eimeria sharmani have been reported in P. lateralis; however, the presence of Eimeria godmani and Eimeria inornata expands the suite of eimerian species known in rock wallabies of the "lateralis" complex. These observations indicate that the host distribution of Eimeria species in rock wallabies is more diverse than previously thought, and supports the hypothesis that these coccidia have an ancient association with rock wallabies which persisted as the hosts radiated.
Animals↗
Survival and development of the different life stages of Ixodes scapularis (Acari: Ixodidae) held within four habitats on Long Point, Ontario, Canada.
From November 1989 to April 1993, blood-fed females and unfed adults and nymphs of lxodes scapularis Say were maintained in housings within 4 different habitats on Long Point, Ontario, Canada, to evaluate the effects of habitat on tick development. More fed females survived the winter within the maple forest (75.6%) than the cottonwood dune (36.1%), whereas 52.8-62.0% survived the winter within the 2 remaining habitats. The proportions of females that laid eggs within the maple forest (90.3%), oak savannah (83.9%), and white pine habitats (78.4%) were similar and greater than in the cottonwood dune (53.8%). In each habitat and all years, females began laying eggs during late April or early May. The time of egg deposition was consistent whether females fed in November and overwintered, or fed during April of the subsequent year. Significantly more eggs hatched within the maple forest (96.4%) and white pine (79.3%) than in the oak savannah (3.8%) or cottonwood dune habitats (0.0%). Hatch occurred in mid- to late July each year. The proportion of unfed I. scapularis adults that survived the winter was not significantly different among the 4 habitats. Unfed adults held in the oak savannah and cottonwood dune habitats died by early June, whereas ticks survived until late June or early July within the maple forest and white pine habitats. Unfed nymphs survived an average of 3.4 mo (range, 0.5-5.5) longer than unfed adults. Fed larvae placed in the field from 22 April to 3 July 1992 molted or died that year. In contrast, 66.7 and 100% of fed larvae placed in the field between 15 and 28 July, and after 28 July, respectively, overwintered before molting. More larvae successfully molted before overwintering (46.9%) than did those that overwintered (17.9%). The proportion of larvae that successfully molted was greatest within the maple forest and least within the cottonwood dune. Fed nymphs placed in the field from 22 April to 4 June molted or died in 1992, whereas 53.6 and 99.2% of fed nymphs placed in the field between 17 June and 28 July, and later than 28 July, respectively, overwintered before molting. Over all habitats, the proportion of nymphs that molted successfully was similar for those that overwintered (43.5%) and those that did not (36.0%). The proportion of nymphs that molted successfully was greatest in the maple forest (60.6%) and least within the cottonwood dune (13.3%). Differences in seasonal extremes of vapor pressure deficits among habitat types were likely responsible for habitat-specific differences in survival of I. scapularis. Based on observations on captive I. scapularis, the life cycle of this tick on Long Point is completed in 3 or 4 yr.
Animals↗
Serologic survey for antibodies to Borrelia burgdorferi in white-tailed deer in Ontario.
Serum samples collected from 623 white-tailed deer (Odocoileus virginianus) in southern Ontario (Canada) from 1985 to 1989 were tested for antibodies to Borrelia burgdorferi using an indirect fluorescent antibody (IFA) staining method. Samples from 150 of the deer were also tested using an enzyme-linked immunosorbent assay (ELISA). At IFA titers of 1:64 and 1:128 deer with antibodies to B. burgdorferi appeared to be widespread throughout southern Ontario, with an apparent prevalence ranging from 3 to 47%. At IFA titres > or = 1:256 and ELISA titres > or = 1:160 deer with antibodies to B. burgdorferi were only present on Long Point which is the only known endemic focus of Ixodes scapularis, the primary vector for B. burgdorferi, in southern Ontario. At these titres the apparent prevalence of antibodies to B. burgdorferi on Long Point was only 5 to 7%, even though the mean intensity of infestation of adult I. scapularis on deer was > 180, and 60% of the adult ticks are infected with B. burgdorferi. Based on these results, white-tailed deer do not appear to be a good sentinel species for the distribution of B. burgdorferi.
Animals↗
Duration of Borrelia burgdorferi infectivity in white-footed mice for the tick vector Ixodes scapularis under laboratory and field conditions in Ontario.
The duration of Borrelia burgdorferi infectivity in white-footed mice (Peromyscus leucopus) experimentally inoculated or infested with infected Ixodes scapularis nymphs was evaluated. Infectivity was assessed by infesting these mice with unfed I. scapularis larvae at 7, 21, 35 and 49 days post-inoculation (DPI) or post-infestation (PI). At 7 DPI, B. burgdorferi was transmitted from 18 of 24 syringe-inoculated mice and all three tick-infected mice to I. scapularis larvae which fed upon them. However, at 21, 35 and 49 DPI, significantly fewer mice were infective. Borrelia burgdorferi was isolated from tissues of 14 of 22 syringe-inoculated mice about 56 DPI, and from all three tick-infected mice. However, the level of agreement between xenodiagnosis and bacterial culture was no greater than would be expected by chance alone. We also determined if B. burgdorferi infectivity of mice varied in relation to periods of tick feeding in the field. White-footed mice were trapped during April, July and August 1993 from two habitats on Long Point peninsula (Ontario, Canada), where B. burgdorferi is endemic. Mice from each habitat were infested with laboratory-reared I. scapularis larvae. Ticks from each mouse were subsequently examined by immunofluorescent assay for B. burgdorferi infection and mice were cultured for B. burgdorferi. None of 3577 I. scapularis larvae fed on 62 mice captured within the cottonwood dune habitat were infected with B. burgdorferi, although it was isolated from six of these mice. Within the maple forest habitat, 0/24, 8/21 (38%) and 1/21 (5%) mice transmitted B. burgdorferi to I. scapularis larvae during April, July and August, respectively. Most mice from the maple forest with B. burgdorferi-positive tissues (14/21) were collected during July, although the level of agreement between xenodiagnosis and tissue culture was poor. Because B. burgdorferi infectivity in mice appears to be of short duration, overwintered I. scapularis larvae and nymphs may have to feed upon infected hosts at the same time of year in order for a cycle of B. burgdorferi infection to be maintained on Long Point. Infected I. scapularis nymphs, rather than persistently infected vertebrate hosts, likely serve as the overwintering "reservoir" for B. burgdorferi on Long Point.
Animals↗
The Canadian Cooperative Wildlife Health Centre and surveillance of wild animal diseases in Canada.
The Canadian Cooperative Wildlife Health Centre (CCWHC) was established in 1992 as an organization among Canada's 4 veterinary colleges, with a mandate to apply veterinary medicine to wildlife management and conservation in Canada. A major function of the CCWHC is nation-wide surveillance of wild animal diseases. Disease surveillance is conceived as consisting of 4 different activities: detection, diagnosis, information management, and use of information. In the CCWHC surveillance program, detection of disease is carried out by a wide range of professional and avocational field personnel, and much effort is expended to stimulate and support this activity. Diagnosis is done by personnel of provincial and federal veterinary laboratories and the CCWHC. Information management is achieved through a national database of wildlife disease incidents developed and maintained by the CCWHC. Use of information is enabled through established channels for distribution of information derived from the surveillance program to persons responsible for wildlife programs and policies, and to the public. There has been a high demand for the services of the CCWHC since its establishment. The CCWHC responds to approximately 2000 requests for information annually, distributes its newsletter to over 1700 recipients, examines approximately 1200 wild animal submissions each year, and has accumulated records of over 5000 disease incidents in its database. Technical information from the CCWHC has benefited federal, provincial/territorial, and nongovernment wildlife agencies; endangered species recovery programs; federal and provincial veterinary services; and federal and provincial public health programs.
Animal Diseases↗
The anatomy and perfusion of the renal portal system in the red-eared slider (Trachemys scripta elegans).
The anatomy of the renal portal system of the red-eared slider (Trachemys scripta elegans) is described, based on dissection of six double latex-injected specimens (three males, three females). The anatomy of these vessels, which had not previously been described in this species, was found not to differ significantly from the fundamental chelonian pattern. Fluoroscopic radioangiography revealed that venous blood returning from the hindlimbs flowed predominantly to the liver and bypassed the kidneys. Blood from the tail either flowed to the kidneys or bypassed them and flowed directly to the liver. A putative valve is described that governs venous blood flow from the caudal body to or around the kidneys.
Animals↗
The effect of the renal portal system on pharmacokinetic parameters in the red-eared slider (Trachemys scripta elegans).
The premise that drugs not be injected into the caudal body of reptiles because they will be carried by the renal portal system to the kidneys, where they may be nephrotoxic or rapidly excreted, was tested by comparing the pharmacokinetics of gentamicin (excreted via glomerular filtration in mammals) and carbenicillin (excreted partly via renal tubular secretion in mammals) following injection into the forelimb or hindlimb of red-eared sliders (Trachemys scripta elegans). Ten sliders received intramuscular gentamicin (10 mg/kg) in a forelimb (n = 5) or a hindlimb (n = 5), and plasma levels of the drug were assayed over time. Following drug clearance, the experiment was repeated with the site of injection reversed so that each animal acted as its own control. Another 10 sliders were similarly treated, using intramuscular carbenicillin (200 mg/kg). Injection site of gentamicin had no effect on any pharmacokinetic parameter (time to maximum plasma concentration, maximum plasma concentration, half-life, area under the curve, clearance, and volume of distribution). However, the area under the curve of plasma carbenicillin concentration vs. time was significantly lower following hindlimb injection, in comparison with forelimb injection, at 1, 4, and 8 hr, which may reflect reduced bioavailability of the drug, as would be expected with renal portal perfusion and tubular excretion on first pass through the kidney. This effect on carbenicillin likely is not clinically important because plasma levels remained above recommended minimum inhibitory concentrations. Because blood draining the caudal body of reptiles passes through the kidneys or the liver before reaching the central circulation, the effect on the pharmacokinetics of a drug injected in that region will vary with its renal or hepatic extraction rate. Generally, this effect is unlikely to be significant.
Animals↗
Determination of plasma concentrations of epirubicin and its metabolites by high-performance liquid chromatography during a 96-h infusion in cancer chemotherapy.
In order to determine epirubicin and its metabolites at low concentrations (< 38 ng/ml) in small plasma samples, a fast reliable method based on a precipitation pre-treatment and sensitive reversed-phase isocratic HPLC has been developed and validated for epirubicin in the range 5-100 ng/ml. The R.S.D. was 5-9% over this concentration range. For human serum containing 25 ng/ml of epirubicin, the inter- and intra-day variation was < 10%. Recoveries of the metabolites epirubicinol, 7-deoxydoxorubicinone and 7-deoxydoxorubicinolone at 20 ng/ml ranged from 94-104%. The assay has been used to study human plasma samples taken during a 96-h infusion of epirubicin in a patient with multiple myeloma. The combined levels of the unseparated metabolites, epirubicin glucuronide and epirubicinol glucuronide, were semiquantitatively determined after treatment with beta-glucuronidase. The metabolites epirubicinol and 7-deoxydoxorubicinolone, but not 7-deoxydoxorubicinone, were also detected and measured.
Antibiotics, Antineoplastic↗
Effects of the intestinal flagellate, Cochlosoma anatis, on intestinal mucosal morphology and disaccharidase activity in Muscovy ducklings.
Newly hatched female Muscovy ducklings were randomly separated into 2 groups of 12 and 1 group of 13. Ducklings in the first 2 groups were each orally inoculated with 0.5 ml of sterile normal saline containing 0 and 3 x 10(6) trophozoites of Cochlosoma anatis, respectively. Birds in the third group were each orally inoculated with 3 x 10(6) trophozoites for 5 consecutive days. Birds were weighed daily for the first 5 days and then on days 7, 14 and 21 post-inoculation (p.i.). On days 6, 7, 8, 13, 14, 15, 20, 21 and 22 p.i., 1 bird from each group was killed and samples of intestine at 7 levels were taken for trophozoite counts, mucosal disaccharidase analyses and morphometric analysis. Body weights did not differ among treatment groups at any time during the experiment. Trophozoite numbers did not change over the period 6-22 days p.i. Trophozoite numbers were lowest in the anterior small intestine and increased distally, but very few were observed in the caecum. Crypt depth was greater in all regions of the small intestine in inoculated groups compared to uninoculated controls, and was significantly increased in the duodenum, proximal jejunum and mid-jejunum (P < 0.05). Villus height was greater in inoculated groups compared to controls at all levels of the intestine and was significantly increased in the duodenum, proximal jejunum and ileum (P < 0.05). Mucosal palatinase and maltase activity in the small intestine were reduced in inoculated groups compared to uninoculated controls; palatinase activities were significantly reduced in the proximal and mid-jejunum and maltase activities were significantly reduced in the mid-jejunum (P < 0.05). Sucrase activities were significantly increased at all levels of the small intestine in inoculated ducklings compared to uninoculated controls (P < 0.05). Although no clinical signs were evident, Cochlosoma infection significantly altered intestinal morphometrics and mucosal enzyme concentrations in ducklings, in several cases in a counter-intuitive direction.
Animals↗
Prevalence of hepatic helminths and associated pathology in impala (Aepyceros melampus) in Swaziland.
The livers of impala (Aepyceros melampus) collected in the Mlawula-Mbuluzi-Simunye Nature Reserve and Protected Area complex in northeastern Swaziland from October 1985 to September 1986 were infected with three species of helminths: a nematode (Cooperioides hepaticae), a cestode (Stilesia hepatica), and a trematode (Fasciola gigantica). Cooperioides hepaticae caused a severe cholangitis. Lambs were infected at 1.5 to 2 mo of age, and the prevalence increased to 100% by 5 mo of age. The prevalence was 82% in yearlings and 44% in adults, with the highest prevalence and intensity of infection at the end of the dry season. Stilesia hepatica was found primarily in adults. Heavy infections caused a thickening and distension of the main bile ducts, but no changes were evident in the liver parenchyma. Fasciola gigantica, found only in one adult male, caused a thickening and distension of main bile duct. There was no apparent association between the helminth infections and body condition.
Age Factors↗
Development of a laboratory animal model of postoperative small intestinal adhesion formation in the rabbit.
In order to establish a model of postoperative intestinal adhesions that would simulate the problem experienced in horses, New Zealand White rabbits were utilized to compare two models of adhesion formation that had been successful in the horse, an ischemic strangulating obstruction (ISO) model and a serosal scarification model. An untreated control group was compared with animals subjected to 1, 2, 3 and 4 h periods of ISO, and to serosal scarification. At postmortem examination 14 d postoperatively, the number of rabbits in each group with adhesions was recorded. Serosal scarification was significantly more consistent at producing adhesions than ISO (Fisher's exact test, P = 0.0022). The 3 h of ISO group was significantly different from the control group: however, compared to the serosal scarification group, fewer animals had adhesions and one animal died of complications associated with the experimental procedure. Based on these results, serosal scarification was selected as the best model for utilization in further studies of adhesion prevention.
Animals↗