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Biomedical subjects

C A Mebus

Publications and source records attributed to C A Mebus.

At least 55 records · Page 3Linked to original sources
PubMed1987

Susceptibility of white-tailed deer to experimental heartwater infections.

Nine white-tailed deer (Odocoileus virginianus) were experimentally infected with Cowdria ruminantium, the causal agent of heartwater. All deer developed clinical signs; one was killed, one was treated, and seven died within 2 wk postinoculation. Diagnosis of heartwater was based on clinical signs, postmortem lesions and by microscopic observation of C. ruminantium in endothelial cells of brain capillaries of dead animals. Cowdria ruminantium was passaged by collecting blood from deer at the height of the febrile response and intravenous inoculation of susceptible deer and goats. Tetracycline was effective in the treatment of heartwater in a deer.

Animals↗
PubMed1987

The development of Cowdria ruminantium in neutrophils.

The sequential development of C. ruminantium (Kwanyanga and Kümm isolates) was followed in caprine leukocyte cultures by light microscopy, direct immunofluorescent microscopy (DFA), indirect immunoflourescent microscopy (IFA) and transmission electron microscopy (TEM). During the febrile response, one to several small cocci, large ring forms or rods were observed in neutrophils in blood smears and cytopreparations of neutrophil fractions using Diff Quik stain, Giemsa stain, DFA and TEM. One to several C. ruminantium colonies were seen in up to 35% of neutrophils maintained in vitro for 18 h to 5 days. The organisms were located in neutrophil phagosomes by TEM and were enveloped by two trilamellar unit membranes. Initially, C. ruminantium was tightly enclosed within phagosomes. At 20 h of incubation, organisms were frequently observed undergoing binary fission within enlarged phagosomal vacuoles. At later time periods, neutrophils harboured fully formed colonies (morula) containing numerous organisms. An occasional C. ruminantium-infected macrophage (Kümm isolate), and an occasional infected eosinophil (Kümm and Kwanyanga isolate) were found.

Animals↗
PubMed1987

Abortion in sows experimentally infected with African swine fever virus: pathogenesis studies.

Thirteen sows that were 38 to 92 days pregnant were experimentally infected with an African swine fever (ASF) virus strain of low virulence (Dominican Republic isolate). Seven of 11 sows that were not killed had aborted. The pathogenesis of the abortions was studied, using virus isolation, tissue immunofluoresence, and histopathologic techniques. African swine fever virus was recovered from 179 of 1,329 (13.5%) fetal tissues tested. The 3 fetal tissues most frequently yielding virus were the fetal placenta, amniotic fluid, and fetal heart blood. Virus was not recovered from fetal tissues obtained from 2 of the aborting sows. Direct immunofluorescent microscopy for ASF viral antigen was done on approximately 1,175 fetal tissues. Although brightly fluorescing cells were common in maternal tissues, specific immunofluorescence was present in only placental tissues from 2 sows. Microscopic lesions in fetal tissues were inconsistent and included mild focal placentitis, mild heptic degeneration and necrosis, and mild interstitial pneumonia. These changes were not considered to be sufficiently specific to have diagnostic significance. In marked contrast to these changes in the fetal tissues, maternal tissues had high titers of virus, with marked necrosis of lymphoid tissues, and contained many cells with ASF viral antigen. We conclude that specific diagnosis of abortion resulting from ASF infection should, therefore, be based on examination of maternal tissues, rather than fetal tissues. The pregnancy failure seems to result from the effects of the virus infection on the dam more so than from direct viral damage to the placenta or fetus.

Abortion, Veterinary↗
PubMed1986

Embryo transfer as a means of controlling the transmission of viral infections. VII. The in vitro exposure of bovine and porcine embryos to foot-and-mouth disease virus.

When 169 zona pellucida-intact bovine embryos were exposed to 10(6) pfu/ml of foot-and-mouth disease virus and then washed, no infectious virus was detected on any of the embryos. FMD viral infectivity was found, however, in association with 14 of 42 hatched (zona pellucida-free) bovine embryos and in a small number of zona pellucida-intact porcine embryos. The porcine embryos were assayed individually and in groups of 8 embryos. Four of the 124 individual embryos and 2 of the 9 groups of embryos carried the infectious virus.

Journal Article↗
PubMed1986

Embryo transfer as a means of controlling the transmission of viral infections. VIII. Failure to detect foot-and-mouth disease viral infectivity associated with embryos collected from infected donor cattle.

Foot-and-mouth disease (FMD) viral infectivity detectable in cell cultures or by animal inoculation was not found to be associated with any of 48 washed zona pellucida-intact (ZPI) embryos collected from 8 cattle during the acute stages of disease. Similarly, infectivity was not found to be associated with any of 42 washed ZPI embryos collected from 3 cattle 21 d after infection with FMD.

Journal Article↗
PubMed1986

Identification of a bovine enteric syncytial virus as a nongroup A rotavirus.

An atypical or nongroup A rotavirus was identified in feces obtained from gnotobiotic calves in which fecal preparations originally derived during an epizootic of neonatal calf diarrhea had been serially passaged. The epizootic was previously reported to be caused by a noncharacterized viral agent that induced the formation of epithelial syncytia on small intestinal villi of experimentally infected calves. This bovine, nongroup A rotavirus was found to be antigenically related to a described atypical rotavirus of rats by immunofluorescence and by enzyme immunoassay. Complementary DNA derived from the atypical rat rotavirus cross hybridized with RNA obtained from the bovine virus, but not with RNA extracted from group A rotaviruses. Complementary DNA derived from SA-11 group A rotavirus cross hybridized with other group A rotavirus RNA, but not with RNA obtained from either the rat or bovine nongroup A isolates. Additionally, another similar, if not identical, bovine atypical rotavirus was identified in a second epizootic of neonatal calf diarrhea that occurred several hundred kilometers and 8 months apart from the original epizootic.

Animals↗
PubMed1986

In vitro and in vivo association of African swine fever virus with swine erythrocytes.

The association of African swine fever virus (ASFV) with swine erythrocytes in vivo, in high titers, was verified by inoculating 30 pigs with 17 ASFV isolates and assaying their plasma and washed erythrocyte fractions for residual virus. Viral antigens were specifically localized on the surface of in vitro and in vivo swine erythrocytes, using the fluorescent antibody technique and 3 monoclonal antibodies specific for ASFV. The same monoclonal antibodies immunoprecipitated virus-specific polypeptides of molecular weights 13 kd and 73 kd from ASFV-infected Vero cells. Erythrocytes from viremic swine infected with Lisbon-60, Dominican Republic, Badajoz-M98, or Cameroon isolates of ASFV were studied by transmission electron microscopy. Virus was found in membrane depressions at the surface of erythrocytes. These surface depressions resembled stages of smooth surfaced pits. Erythrocytes from viremic pigs were fragile osmotically.

African Swine Fever↗
PubMed1985

Rotaviral and coronaviral diarrhea.

A number of different viruses can be primary pathogens in the neonatal calf diarrhea complex. By far the most common viruses causing calfhood diarrhea found throughout the world are rotaviruses and coronaviruses. Primary infection of newborn calves with either one of these viruses can cause severe intestinal alterations and diarrhea. Rotaviruses can produce high-morbidity outbreaks of diarrhea in calves under 10 days of age. Morality is variable mainly owing to secondary bacterial infections and electrolyte imbalances. Rotavirus infection of the small intestinal mucosa leads to loss of enterocytes of the upper third of the intestinal villi with subsequent villous atrophy and malabsorption. There is growing evidence that different rotavirus serotypes of different pathogenicity exist. Coronavirus infections can produce high-morbidity outbreaks of diarrhea in calves under 20 days of age, with variable mortality due to secondary complications. Coronaviruses affect not only the small intestinal mucosa, producing significant villous atrophy, but also the colon, causing a very severe intestinal damage that can lead to death due to subsequent electrolyte disturbances. All coronaviruses associated with neonatal calf diarrhea appear to be of the same serotype. The etiologic diagnosis of viral diarrheas of calves requires the support of the laboratory. One of the most useful diagnostic methods is the examination of fecal extracts for the presence of virus particles by electron microscopy. Other antigen-detection procedures like enzyme immunoassays have been found to be useful in the diagnosis of rotaviral diarrheas. The sample of choice for these diagnostic tests is a fresh fecal sample collected directly from the calf as close as possible to the onset of diarrhea. Samples from more than one calf during the outbreak enhance the laboratory ability to establish a proper viral diagnosis.

Animals↗
PubMed1984

Extraction of viral DNA from erythrocytes of swine with acute African swine fever.

The preparation of wild-type African swine fever (ASF) virus DNA from small amounts of viremic blood from acutely febrile pigs is outlined. The extracted DNA is viral and not host-cell DNA, because of specific homology with cell culture grown and purified ASF virus and because no DNA bands are obtained with an equal amount of nonviremic pig blood. Thus, in the absence of suitable serologic methods for strain identification, it is now possible to catalogue wild-type isolates by characteristic DNA restriction patterns. The wild-type virus genome contains terminal single-stranded DNA cross-links and has the largest genome size (180 kilobase pairs) reported for the ASF virus. Experimental passage of the virus in contact-infected pigs and buffy coat cultures appears to confirm the stable nature of the ASF genome in the field.

African Swine Fever↗
PubMed1983

Induction of cross-reactive serum neutralizing antibody to human rotavirus in calves after in utero administration of bovine rotavirus.

Sera from calves infected in utero or postnatally with bovine rotavirus NCDV or postnatally with human rotavirus D (serotype 1) were tested by plaque reduction neutralization assay for antibody to bovine rotavirus and to three serotypes of human rotavirus. Homologous antibody developed in all animals, but antibody to heterologous rotaviruses developed mainly in animals exposed in utero to bovine rotavirus. The development of heterologous antibody may explain the immunological implications for cross-protection, previously observed between bovine and human rotavirus in experimentally infected calves.

Animals↗
PubMed1981

Induced African swine fever in feral pigs.

Feral pigs trapped in Florida were exposed by intranasal/oral inoculation or contact to African swine fever virus isolants from the Iberian peninsula and the Dominican Republic. All exposed pigs became sick and died or were killed after becoming moribund. Necropsy revealed lesions typical of African swine fever, but several pigs had marked hemorrhage surrounding the kidneys or rectum or in the gastric, hepatic, or ventral abdominal region that, in the field, might have suggested trauma or poisoning as a cause of death. Most pigs had severe lesions associated with kidney worms. Virus was detected in the blood and selected tissues of each pig, using the hemadsorption reaction in porcine monocyte cultures; direct or indirect immunofluorescence was used to confirm the diagnosis.

African Swine Fever↗
PubMed1980

Western hemisphere isolates of African swine fever virus: asymptomatic carriers and resistance to challenge inoculation.

Convalescent clinically normal pigs were tested for the persistence of African swine fever (ASF) infection. One group of pigs was examined 135 days after inoculation with a Brazilian isolate and a 2nd group was examined 110 days after inoculation with a Dominican Republic isolate. Susceptible pigs exposed by contact to these groups remained clinically normal. These contact pigs plus 2 more pigs added to each group developed ASF after being fed and inoculated with tissues collected from recovered pigs. African swine fever virus was not isolated in swine buffy coat cultures inoculated with supernatant fluid from the collected tissues. The remaining convalescent Brazilian and Dominican Republic ASF pigs were challenge inoculated with homologous virus and then with Lisbon 60 ASF virus. Pigs in both groups remained clinically normal after homologous virus challenge inoculation. Pigs in the Brazilian group remained clinically normal after inoculation of the lisbon 60 ASF viral isolate. Of 5 pigs in the Dominican Republic group, 3 developed a transient viremia after inoculation of the Lisbon 60 ASF viral isolate.

African Swine Fever↗
PubMed1979

Rotaviral immunity in gnotobiotic calves: heterologous resistance to human virus induced by bovine virus.

The possibility of immunizing human infants against rotaviruses, which cause severe dehydrating diarrheal disease, may depend on the use of a related rotavirus, derived from another animal species, as a source of antigen. To test the feasibility of this approach, calves were infected in utero with a bovine rotavirus and challenged with bovine or human type 2 rotavirus shortly after birth. Infection in utero with bovine rotavirus induced resistance to diarrheal disease caused by the human virus as well as the homologous bovine virus. These data suggest that the bovine virus is sufficiently related antigenically to the human type 2 virus to warrant further evaluation of the former as a source of vaccine.

Animals↗