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Biomedical subjects

J W McVicar

Publications and source records attributed to J W McVicar.

At least 19 recordsLinked to original sources
PubMed1989

Guidelines for the prevention of simian immunodeficiency virus infection in laboratory workers and animal handlers.

The authors are members of a working group that formulated guidelines to minimize transmission of simian immunodeficiency virus (SIV) infection to man. Biosafety level (BSL) 2 standards are recommended for handling of clinical specimens and housing of SIV inoculated animals. Manipulation of SIV preparations may be performed in a BSL 2 facility with additional BSL 3 practices and equipment; for large volume or concentrated preparations of SIV BSL 3 containment is necessary. Written policies regarding management and testing of workers exposed to SIV are recommended.

Animals↗
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↗
PubMed1984

Quantitative aspects of the transmission of African swine fever.

The contagiousness of pigs during different stages of infection with African swine fever virus was assessed by measuring the amount of virus excreted and the amounts of virus in the blood and other tissues, as well as determining the infectious dose of the virus by various routes. The virus was present in substantial amounts in secretions and excretions of acutely infected pigs for only 7 to 10 days after the onset of fever and was present in the greatest amount in the feces. Virus persisted in the blood of some recovered and clinically normal pigs for 8 weeks and in the lymphoid tissues for at least 12 weeks. The intranasal/oral ID50, and the IV/IM ID50 of a moderately virulent isolate of African swine fever virus were determined to be 18,500 and 0.13, 50% headsorbing units, respectively. A highly virulent isolate required approximately 10-fold more virus to cause infection by the intranasal/oral route.

African Swine Fever↗
PubMed1983

Aerosol exposure of cattle to foot-and-mouth disease virus.

Slight modifications of a small, plastic covered greenhouse provided a chamber for the exposure of cattle of all ages to aerosols of foot-and-mouth disease virus. Particle size distributions of aerosols were 76% less than 3 microns, 17% 3-6 microns, and 7% greater than 6 microns immediately after the deVilbis no. 40 nebulizer used was turned off and 90% less than 3 microns, 8% 3-6 microns, and 2% greater than 6 microns 20-30 min later. Pharyngeal virus growth curves and viremia patterns correlated well with the dose of virus to which test cattle were exposed and were similar to those of cattle inoculated intranasally.

Aerosols↗
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↗
PubMed1978

Pre-lytic release of foot-and-mouth disease virus in cytoplasmic blebs.

The pre-lytic release mechanism of foot-and-mouth disease virus was investigated by immunofluorescence, acridine orange staining, and electron microscopy in infected bovine and porcine kidney coverslip cultures. Cells with cytoplasmic fluorescence and which were positive for single stranded RNA with acridine orange staining were observed at 2 h after infection. Scanning electron microscopy showed cytoplasmic blebs in all cultures examined 2 h after infection. Rounded cells with virus inclusions began to appear 3 h after infection. Rounded cells and cytoplasmic blebs were shown to have single stranded RNA by acridine orange staining. Immunofluorescence and transmission electron microscopy with immunoferritin tagging demonstrated foot-and-mouth disease virus in cytoplasmic blebs. This study presents evidence for a pre-lytic release of foot-and-mouth disease virus through virus-containing cytoplasmic blebs emerging from infected cells.

Aphthovirus↗
PubMed1976

Pathogenesis of foot-and-mouth disease: the lung as an additional portal of entry of the virus.

Donor cattle infected with foot and mouth disease (FMD) virus subtype O1 were used to expose experimental cattle. The pharyngeal virus growth and viraemia patterns after contact exposure were quite different from those obtained after intranasal inoculation and suggested that the lower respiratory tract might provide an additional portal of entry for the virus. A tracheotomy was performed on experimental cattle to let the respiration bypass the pharynx, followed by exposure to FMD virus by different routes. The results confirmed that FMD virus can enter the bloodstream via the lung, followed by haematogenic infection of the pharynx and other replication sites simultaneously. These observations led to further experiments in which the intravenous route of infection was used to study the interaction of virus growth in the phayrnx, in other sites, and in viraemia.

Aerosols↗
PubMed1976

Pathogenesis of foot-and-mouth disease: clearance of the virus from the circulation of cattle and goats during experimental viraemia.

Viraemia is an important aspect of the pathogenesis of infectious diseases, but the mechanisms of entry and removal of virus from the vascular system particularly in natural hosts are poorly understood. The results of this study showed that the clearance of foot and mouth disease virus (FMDV) from the circulation of cattle and goats followed the general rules for the clearance of inert particulate materials and other viruses from the circulation. High doses of infused FMDV were cleared less efficiently than low doses, probably as a result of a depletion of the reticulo-endothelial system by the higher doses. FMDV was cleared from the circulation of cattle at a considerably slower rate than from the circulation of goats, but in both species significant individual variation in clearance was observed. These results could explain individual as well as species variations relative to the onset and duration of viraemia.

Animals↗
PubMed1976

Growth of foot-and-mouth disease virus in the upper respiratory tract of non-immunized, vaccinated, and recovered cattle after intranasal inoculation.

Non-immunized, vaccinated, and recovered cattle were inoculated intranasally with various doses of foot-and-mouth disease virus. Samples of oesophageal-pharyngeal (OP) fluid were taken periodically for up to 7 days after inoculation and virus titres of these samples were plotted as pharyngeal virus growth curves. In non-immunized cattle, the length of the lag period and of the growth period were inversely proportional to the dose of virus given. Maximum titres were observed when clinical signs were first detected. Three of the 10 cattle studied had virus growth rates that were lower than rates of others given the same dose of virus, and clinical signs appeared later than expected in these three cattle. Cattle vaccinated with an inactivated virus oil-adjuvant vaccine had pharyngeal virus growth curves that were similar to those obtained from non-immunized cattle for 30 h. after inoculation. Titres of virus in OP fluid samples taken 2-7 days after inoculation were substantially lower in cattle with a high pre-exposure serum mouse protection index than titres from partly-immunized or non-immunized cattle. Nine of 14 cattle had detectable but reduced virus growth after intranasal inoculation with homologous virus. Five recovered cattle inoculated with heterologous virus reacted similarly to non-immunized animals.

Animals↗