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Biomedical subjects

B Meehan

Publications and source records attributed to B Meehan.

At least 19 recordsLinked to original sources
PubMed2002

Evaluation of a porcine circovirus type 2-specific antigen-capture enzyme-linked immunosorbent assay for the diagnosis of postweaning multisystemic wasting syndrome in pigs: comparison with virus isolation, immunohistochemistry, and the polymerase chain reaction.

Quantitative virus isolation, immunohistochemistry, polymerase chain reaction (PCR) assay, and a porcine circovirus 2 (PCV2)-specific antigen-capture enzyme-linked immunosorbent assay (ELISA) were used for differentiation between clinical and subclinical PCV2 infections of swine. Tissue samples from pigs experimentally infected with PCV2 and field cases of postweaning multisystemic wasting syndrome and PCV2-associated reproductive disorders were used in this evaluation. In initial studies on 6 PCV2 pools using 3 previously published PCR protocols for PCV2 detection, quantitative virus isolation, and antigen-capture ELISA, substantial differences in sensitivity were identified among these procedures. Examination of tissue samples from diseased and clinically normal pigs indicated that immunohistochemistry, quantitative virus isolation, and antigen-capture ELISA could be used to differentiate between clinical and subclinical PCV2 infections, but the PCR assay could not. Because subclinical infections of pigs with PCV2 are common, the use of nonquantitative PCR as a diagnostic tool for PCV2-related diseases should be discouraged and the PCV2-specific antigen-capture ELISA evaluated further.

Animals↗
PubMed2001

Lack of antibodies to porcine circovirus type 2 virus in beef and dairy cattle and horses in western Canada.

Porcine circovirus type 2 (PCV2) is a recently recognized agent that is consistently associated with postweaning multisystemic wasting disease in swine. There are conflicting data concerning the ability of this virus to infect and cause disease in other species. To determine if normal cattle, cattle affected with various illnesses, and normal horses in endemic areas of PCV2 infection in swine have had PCV2 infections, 100 randomly selected bovine sera, 100 equine sera, and 100 colostrum samples from clinically normal dairy cattle were examined for the presence of antibodies to porcine circoviruses by using ELISAs. All samples tested were negative for antibodies to porcine circoviruses. As well, a seronegative neonatal Holstein calf and 6 seronegative, 6-month-old beef calves that were experimentally infected with PCV2 failed to develop antibodies to the virus. These results suggest that natural infection of cattle and horses with PCV2 does not occur, or is a rare event, in western Canada.

Animals↗
PubMed2001

Association of porcine circovirus 2 with reproductive failure in pigs: a retrospective study, 1995-1998.

In order to determine if vertically transmitted porcine circovirus (PCV) has played a role in reproductive failure in pigs in areas of endemic infection, archival fixed tissues were examined by polymerase chain reaction (PCR) and immunohistochemistry. Tissues tested were from routine cases of abortion or reproductive failure submitted between 1995 and 1998 to the diagnostic laboratory at the Western College of Veterinary Medicine, Saskatoon. They originated from 29 high-health herds in the provinces of Alberta and Saskatchewan and comprised a total of 36 individual submissions. Porcine circovirus type 1 (PCV1) was not detected by PCR in any submitted tissues. Porcine circovirus type 2 (PCV2) was not detected by PCR or immunohistochemistry in any of the submitted tissue. The effect of extended formalin fixation on the detection of PCV2 by PCR was assessed and fixation for up to one week had no gross effect on sensitivity of detection using this PCR technique. Failure to detect porcine circoviruses in cases of reproductive failure prior to 1999 in areas of endemic infections, suggests that reproductive disease may be a new clinical manifestation of PCV2 infection, and that vertical transmission may not have been the primary mechanism of initial dissemination of the virus in the pig population.

Abortion, Veterinary↗
PubMed2000

Experimental infection of colostrum deprived piglets with porcine circovirus 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV) potentiates PCV2 replication.

Experimental infection of colostrum-deprived (CD) pigs with a combined inoculum of porcine circovirus 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV) potentiated the replication and distribution of PCV2 virus, when compared with pigs inoculated with PCV2 alone. The replication and distribution of PRRSV in dually infected pigs was not enhanced, when compared to pigs inoculated with PRRSV alone. The mechanisms involved in the potentiation of PCV2 replication in PCV2/PRRSV and PCV2/porcine parvovirus (PPV) dually infected pigs may relate to the fact that monocyte/macrophage cell types are common targets of these 3 viruses.

Animals↗
PubMed2000

Reproduction of lesions of postweaning multisystemic wasting syndrome by infection of conventional pigs with porcine circovirus type 2 alone or in combination with porcine parvovirus.

Post-weaning multisystemic wasting syndrome (PMWS) has recently emerged as an important disease of pigs in North America, Europe and Asia. Porcine circovirus type 2 (PCV2) and porcine parvovirus (PPV) have been isolated from affected pigs. To investigate the pathogenicity of these isolates, groups of colostrum-deprived conventional pigs were inoculated with PCV2 alone (n=4), PPV alone (n=3) or dually with PCV2 and PPV (n=7) and examined post mortem between 21 and 26 days post-infection (dpi). Two control pigs were inoculated with an uninfected cell culture lysate. All pigs that received both viruses became dull at approximately 10-12 dpi and six of these animals subsequently developed jaundice. Hepatomegaly and enlarged kidneys were prominent post-mortem findings in these animals. Histopathological examination revealed severe macrophage infiltration, syncytia formation and numerous cytoplasmic and nuclear amphophilic inclusion bodies in lymphoid tissues. Granulomatous lesions were apparent in liver, lung, kidney, pancreas, myocardium, intestines, testis, brain and salivary, thyroid and adrenal glands. Abundant PCV2 antigen was detected in affected tissues. Only one of the four pigs inoculated with PCV2 alone developed clinical signs, but they all had histopathological lesions which, although less severe, were similar to those in the dually infected animals. The control pigs and those infected with PPV alone remained clinically normal and did not have gross lesions. The only histopathological lesion seen in these animals was mild interstitial nephritis in the pigs infected with PPV alone. These results indicate that lesions of PMWS can be induced by inoculating pigs with PCV2 alone, thereby fulfilling Koch's postulates. Concurrent infection with PPV increased the severity of the lesions, suggesting that co-factors are important in the pathogenesis of PMWS.

Animals↗
PubMed2000

Coinfection by porcine circoviruses and porcine parvovirus in pigs with naturally acquired postweaning multisystemic wasting syndrome.

Postweaning multisystemic wasting syndrome (PMWS) is an emerging disease in swine. Recently, the disease has been reproduced with inocula containing a newly described porcine circovirus (PCV), designated PCV 2, and porcine parvovirus (PPV). In order to determine if these viruses interact in naturally acquired PMWS, affected tissues from field cases were examined by immunohistochemistry (IHC) and polymerase chain reaction (PCR) for PCV 2 and PPV, as well as by PCR for the other recognized porcine circovirus, PCV 1. Porcine circovirus 2 was detected by PCR or IHC in affected fixed or frozen tissues from 69 of 69 cases of PMWS collected over 3 years from 25 farms. Porcine parvovirus was detected in 12 of the same cases, and PCV 1 was detected in 9 of 69; however, an apparent decrease was found in the sensitivity of the PCRs used to detect the latter 2 viruses when fixed tissue from the same cases were compared with the use of frozen tissues. Porcine circovirus 2 was not detected by PCR in affected tissues from 16 age-matched pigs that had Streptococcus suis-associated disease. Electron microscopic examination of plasma pooled from 15 pigs with PMWS revealed the presence of PCV and PPV, whereas these viruses were not observed in pooled plasma from 5 age-matched clinically normal pigs. These results confirm and extend previous findings documenting a consistent association of PCV 2 with PMWS. As well, infection by PPV or PCV 1 or both may be an important cofactor in the pathogenesis of some, but apparently not all, cases of PMWS.

Animals↗
PubMed2000

Viral wasting syndrome of swine: experimental reproduction of postweaning multisystemic wasting syndrome in gnotobiotic swine by coinfection with porcine circovirus 2 and porcine parvovirus.

One-day-old gnotobiotic piglets were inoculated intranasally with in vitro passaged porcine circovirus 1 (PCV-1), PCV-2, and porcine parvovirus (PPV) alone or in combination (PCV-1/PCV-2, PCV-1/PPV, and PCV-2/PPV). Piglets were evaluated for 1) the development of porcine postweaning multisystemic wasting syndrome (PMWS), 2) distribution of viral antigens by immunochemistry, and 3) viremia and the presence of viral DNA in nasal and ocular secretions and feces. All single agent-infected piglets and piglets infected with PCV-1/PCV-2 or PCV-1/PPV were clinically asymptomatic. They were transiently viremic and seroconverted to homologous virus(es). At termination of the study on postinfection day (PID) 35, microscopic lesions were restricted to focal inflammatory cell infiltrates in livers and myocardia. One piglet given PCV-1/PPV was PPV viremic for 2 weeks after infection and had lymphangiectasia of the spiral and descending colon associated with granulomatous inflammation. All four PCV-2/PPV-inoculated piglets developed PMWS, characterized by sudden onset of depression and anorexia, icterus, and submucosal edema. One piglet became moribund on PID 27, and the remaining three piglets were euthanatized between PID 27 and PID 30 because of severe disease. Lymph nodes were small and the livers were mottled. Disseminated angiocentric granulomatous inflammation was present in all tissues examined except the brain. Multiple lightly basophilic intracytoplasmic inclusion bodies were identified in macrophages and histiocytes. PCV-2 antigen was widely distributed within macrophages; PPV antigen was sparse. Hepatocellular necrosis and bile retention were prominent. PCV-2 DNA was identified in ocular, fecal, and nasal secretions. Terminal sera contained antibodies to PPV (4/4) and PCV-2 (3/ 4). Production of PMWS in gnotobiotic swine appears to require PCV-2 and additional infectious agents such as PPV for full disease expression in gnotobiotic piglets.

Animals↗
PubMed2000

Age-dependent metabolic effects of repeated hypoxemia in piglets.

The aim of this study was to determine whether repeated exposure to hypoxemia would modify the response to hypoxemia during maturation. We exposed piglets to three 1-h cycles of hypoxemia (PaO2 = 30 to 35 mmHg; 1 mmHg = 133.3 Pa) at 1 week (n = 9), 2-3 weeks (n = 10), and 4-5 weeks of age (n = 10). O2 consumption (V(O2)) and CO2 production (V(CO2)) were measured, and alveolar ventilation (V(A)) was derived from V(CO2) and PaCO2. Levels of lactic acid (lactate) and serum catecholamines were also measured. With hypoxemia, time had a significant effect on V(O2) and body temperature in an age-dependent fashion: that is, whereas the 1 week group and the 4-5 week group showed both variables decreasing over time, the 2-3 week group showed no drop in V(O2) and a small increase in body temperature over time. Lactate levels increased with hypoxemia in all animals during the first exposure. However, with repeated exposures to hypoxemia, only the 2-3 week group continued to increase its lactate levels. Furthermore, the changes in lactate levels paralleled the changes in epinephrine levels with hypoxemia. We found, too, that although V(A) increased significantly with hypoxemia in all animals, this change was not modified by age or repeated exposures. No significant effects of age or repeated exposures were found in the cardiovascular response to hypoxemia. We concluded that, from a metabolic viewpoint, after repeated exposures to hypoxemia the 2-3 week animals responded differently.

Aging↗
PubMed1999

Reproduction of lesions of postweaning multisystemic wasting syndrome in gnotobiotic piglets.

Neonatal gnotobiotic piglets were inoculated with tissue homogenates and low- and high-passage cell culture material to determine if the lesions of the newly described porcine postweaning multisystemic wasting syndrome (PMWS) could be reproduced. For this, 17 3-day-old gnotobiotic piglets were inoculated intranasally with pelleted chloroform-treated, filtered extracts from cell cultures, filter-sterilized homogenates of lymphoid tissue from PMWS-affected piglets, or control materials. Piglets were maintained in germ-free isolators for up to 5 weeks after infection prior to euthanasia and collection of samples for analysis. All piglets inoculated with the viral inocula developed lesions typical of PMWS, including generalized lymphadenopathy, hepatitis, nephritis, interstitial pneumonia, myocarditis, and gastritis. Porcine circovirus (PCV), as well as porcine parvovirus (PPV), was detected in tissues by virus reisolation, polymerase chain reaction analysis, or immunohistochemistry. All infected piglets developed moderate to high titers of antibody to PCV and moderate titers to PPV. No lesions, virus, or virus-specific antibodies were detected in sham-inoculated or uninoculated control piglets. These studies demonstrate that the lesions of PMWS can be experimentally reproduced in gnotobiotic piglets using filterable viral agents derived from pigs with PMWS and provide an experimental basis for further investigation into the pathogenesis and control of this emerging infectious disease in swine.

Animals↗
PubMed1999

Neuronal apoptosis in sudden infant death syndrome.

Although evidence shows that victims of sudden infant death syndrome (SIDS) suffer repetitive episodes of hypoxemia, only subtle abnormalities have been found in their brains by light microscopy. The aim of the present study was to determine whether apoptosis, a form of cell death that can be triggered by hypoxemia and that leaves no scarring detectable by light microscopy, would be present in hypoxia-sensitive brain regions of SIDS victims. We looked for the presence of apoptosis with an in situ end-labeling method that detects DNA fragmentation. We studied 29 SIDS victims who were age-matched to nine control cases. We found significant neuronal apoptosis in 79% of the SIDS cases: 55% of the cases positive in the hippocampus and 96% positive in the brainstem. Whereas the distribution of apoptosis in the hippocampus was in hypoxia-sensitive subregions, the distribution in the brainstem was mostly in dorsal nuclei, including those involved with sensation in the face and position of the head (nucleus of the spinal trigeminal tract and vestibular nuclei). The control cases showed no significant apoptosis in the hippocampus and a mild degree in the brainstem in three cases. Our results indicate the occurrence of an acute insult at least several hours before death, an insult from which the infants had apparently recuperated. This suggests that SIDS victims suffered repeated apoptosis resulting in significant neuronal damage and, thus, functional loss in key brain regions. The involvement of specific nuclei in the brainstem may be linked to the fact that prone sleeping is a significant risk factor for SIDS. Enhanced neuronal death by apoptosis may thus have major implications for understanding the sequence of events leading to SIDS.

Apoptosis↗
PubMed1998

Isolation of circovirus from lesions of pigs with postweaning multisystemic wasting syndrome.

Postweaning multisystemic wasting syndrome (PMWS), an apparently new disease, has been recognized in swine herds in western Canada. Young pigs with this disease have progressive weight loss, tachypnea, dyspnea, and jaundice, accompanied by interstitial pneumonia, lymphadenopathy, hepatitis, and nephritis. We examined more than 400 pigs from more than 70 herds in Alberta, Saskatchewan, and Manitoba with cases of PMWS. A small virus was isolated from a range of tissues from 8 of 8 affected pigs examined. The agent was identified as a circovirus-like virus using electron microscopy, immunohistochemical staining with porcine and rabbit immune serum, and in situ hybridization. Immunohistochemical examination of tissues from more than 100 affected pigs has revealed widespread viral antigen, often contained in circovirus-like inclusion bodies, in lesions from numerous organs. Although Koch's postulates remain to be fulfilled, these results demonstrate a high degree of association between the presence of the circovirus-like virus and PMWS in affected swine.

Alberta↗
PubMed1996

Respiratory responses to rapid-onset, repetitive vs. continuous hypoxia in piglets.

Repeated, frequent hypoxic exposures may precede Sudden Infant Death. This study assessed whether such hypoxic modality, vs. continuous hypoxia, compromised compensatory cardiorespiratory responses. Following aseptic, chronic instrumentation, 10 to 20 day-old, unsedated piglets underwent measurements of arterial O2 saturation, pH and gas tensions, respiration, heart rate, physical activity, O2 consumption and rectal temperature on several experimental days. The piglets were exposed to 21 min of either 10% or 6% O2 in N2, each comprising either seven, 3-min exposures alternating with 3-min intervals in 21% O2 balance N2, or 7 consecutive hypoxic exposures. Responses to 6% hypoxia were greater than those to 10% hypoxia. In 10% hypoxia, responses to repetitive vs. continuous exposure differed only in PaCO2. In 6% hypoxia, repetitive vs. continuous exposure resulted in lower respiratory frequency (p < 0.05) and in lower ventilation equivalent (p = 0.07) despite higher activity levels. Thus, the mode of hypoxic exposure determines the extent of the respiratory response: Severe, repetitive hypoxia mitigates protective respiratory responses when compared to equivalent, but sustained hypoxia.

Animals↗