Virus Recovery Rates Research Articles

Pathogenicity of avian reoviruses isolated from tendons and tendon sheaths of chickens with leg weakness.

Pathological characteristics of six reoviruses, strains 56-168, 57-F, 56-93L, 57-161, 56-256T3 and 57-162 isolated from leg-tendon materials, were compared upon infection of day-old specific-pathogen-free chicks by the footpad or oral routes. The chicks were examined for clinical signs, body weight, gross lesions of footpad, microscopic lesions of tendon sheaths, virus recovery and AGP antibodies after inoculation. An apparent leg-weakness or lameness was not produced throughout the experiment by any reovirus inoculation, while growth retardation and abnormal feathering were observed mainly in footpad inoculated chicks. Considerable variations in the gross and microscopic lesions and virus recovery rates were recognized among six reoviruses. Strains 56-168, 57-F and 56-93L produced distinct tenosynovitis by either footpad or oral inoculations, moreover, they were recovered from the lesions at 35 days of age. Strain 57-162 could not induce tenosynovitis by not only oral but also footpad inoculation.

Pathogenesis of Infectious Bursal Disease in Chickens Infected with Virus at Various Ages

Chickens free from infectious bursal disease (IBD) maternal antibody were inoculated with a virulent strain of IBD virus at 1, 5, or 11 weeks of age. Chickens inoculated at 5 weeks developed severe clinical signs and had reduced levels of serum complement within 2-4 days postinoculation, but those inoculated at 1 or 11 weeks did not. However, at 1, 2, 4, and 8 days postinoculation, the rate of virus recovery from different tissues, severity of microscopic lesions, and frequency of detection of viral antigens in lymphoid organs of chickens inoculated at 5 weeks were comparable to those of chickens inoculated at 1 or 11 weeks of age. These findings suggest that age resistance to clinical manifestations of IBD is probably independent of the ability of virus to replicate and induce lesions in the host.

Activation of latent herpesvirus hominis in explants of rabbit trigeminal ganglia: the influence of immune serum

More than fifty albino rabbits were inoculated into the right scarified cornea with 10(7) PFU of the Kupka strain of human herpes virus type 1 (HHV-1). At intervals ranging from 4--280 days post infection (p.i.), both gasserian ganglia, both trigeminal nerve trunks and pieces from brain stem and from both corneas were explanted. Activation of the latent HHV-1 was found mainly in the homolateral ganglion tissue, but also in explants originating from the opposite ganglia. Within 24--72 hours, prior to the release of virus into the medium, one infectious unit of HHV was recovered from 10(4)--10(5) cells of the ganglion explant. In addition, a few neurons and satellite cells revealed the presence of virus-specific antigens when the explants were examined by immunofluorescence in serial sections. If the gangia were explanted in the presence of immune serum, the virus recovery rate was at least twice lower as compared to the virus activation in explants kept in the absence of immune serum.

Effects of 5-bromodeoxyuridine and 5-iododeoxyuridine on a latent herpes simplex virus infection.

A latent herpes simplex virus infection was established in rabbit kidney cells. Treatment of the cells with 5-bromo-2-deoxyuridine after the latent infection was established had no effect on the rate of virus recovery but did extend the latent period before active virus growth resumed. In contrast to this, treatment of cells with 5-bromo-2-deoxyuridine or 5-iodo-2-deoxyuridine prior to infection with virus increased the subsequent rate of virus recovery.

Ecology of California Encephalitis Viruses on the Del Mar Va Peninsula

The ecology of California encephalitis viruses was studied on the Del Mar Va Peninsula. Adult mosquitoes were collected weekly from May to October of 1971 and monthly from May to October of 1972, using CDC miniature light traps with Dry Ice. Floodwater mosquitoes were assayed for virus in suckling mice or cell cultures. In 1971 over 77,000 mosquitoes were processed, resulting in 33 virus isolations. In 1972, over 106,000 were processed and 63 virus strains were recovered. Of the 1971 strains, all but one were recovered from Aedes atlanticus mosquitoes, and of the 1972 strains all but two were recovered from A. atlanticus. All A. atlanticus strains were neutralized by Keystone virus mouse hyperimmune ascitic fluid (MHAF). All other strains were recovered from A. canadensis mosquitoes. The single 1971 strain, and one strain from 1972, were neutralized by Jamestown Canyon MHAF. The remaining strain was neutralized by Keystone MHAF. The rate of virus recovery from A. atlanticus remained approximately the same, both between years and during each year studied, even during periods when large numbers of adults were emerging, suggesting that these mosquitoes had emerged infected.

Ecology of California Encephalitis Viruses on the Del Mar Va Peninsula

The high rate of Keystone virus recovery from Aedes atlanticus collected in 1971 and 1972 suggested that these mosquitoes might be emerging infected. To demonstrate the suspected transovarial transmission of this virus, developmental stages of A. atlanticus were collected from the field. Larvae were identified and pooled for virus isolation in suckling mice. Pupae were allowed to emerge in the laboratory, then were segregated by sex and pooled for virus isolation. Keystone virus was recovered from larvae, reared males and reared females, demonstrating transovarial transmission of the Keystone strain of California encephalitis by A. atlanticus.

Hedamycin, a new antitumor antibiotic. II. Biological properties.

The effect of purified proflavine and light exposure was assessed in rabbits whose eyes had been infected with one of two strains of herpesvirus. In comparing proflavine-light and placebo-light treatment, 0.1% proflavine administered twice daily for 5 days had a significant effect in suppressing herpetic eye disease, but 0.05% proflavine was less effective. In addition to being effective in infections with either virus strain, the 0.1% proflavine also suppressed intensity of corneal epithelial ulceration and stromal opacity in animals pretreated with subconjunctival corticosteroids to produce more severe disease. Proflavine or idoxuridine (IDU) alone or in combination showed no differences in suppressing herpetic ocular disease, but all were significantly more effective than placebo. Virus recovery rates were approximately the same from eyes treated with proflavine, IDU, or placebo, indicating that viral replication in the cornea and conjunctiva was not completely suppressed by either of the antiviral drugs alone or in combination.

SSPE virus infections in suckling hamsters. Modification by intracerebral administration of poly I-C.

Subacute sclerosing panencephalitis virus inoculated intracerebrally into suckling hamsters produced approximately a 70% incidence of morbidity and mortality and an 80% virus recovery rate in untreated control animals. A therapeutic regimen, consisting of poly I/C administered intracerebrally three hours before and 7 and 14 days following virus challenge, significantly reduced the incidence of early death and virus isolation. Delay of therapy for 24 hours after virus administration resulted in loss of therapeutic efficacy under the conditions of this experiment. Poly I/C administered intraperitoneally also was without therapeutic benefit.

House sparrows, Passer domesticus (L.), as hosts of arboviruses in Hale County, Texas. I. Field studies, 1965-1969.

A study was made of the role of house sparrows in the epidemiology of arboviruses in Hale County, Texas, during a 5-year period (1965-1969). Virus isolation attempts on bloods of 3,964 wild sparrows yielded 234 western equine encephalitis (WEE), 15 St. Louis encephalitis (SLE), 15 Turlock (TUR), and 2 Flanders-Hart Park (FLA-HP) viruses. Virus recovery rates from viremic nestling house sparrows varied directly with human attack rates of WEE and SLE, and provided the most reliable of several indices used to measure human risk of contracting clinical WEE infection. Rates of WEE virus recoveries were greatest in nestlings found dead in the nest or live nestlings 8 to 12 days old. Arboviruses were not detected in bloods of artificially hatched nestlings, or in fecal specimens of wild nestlings (with or without viremia). WEE virus was recovered from oral swabs of some naturally infected nestlings, but probably originated from blood contamination. These and other results are discussed in terms of WEE virus overwintering and amplification during epizootic seasons in Hale County, Texas.

Comparison of Methods for Recovering Poliomyelitis Viruses from Human Sources.

SummaryOne hundred and four fecal and oropharyngeal specimens obtained directly from human sources were studied in 3 types of tissue cultures. The virus recovery rates among fecal samples were of the same order regardless of the type of tissue culture used. Under the conditions of the study, monkey kidney epithelial cell cultures were superior to HeLa or testicular cultures in the primary isolation of poliomyelitis virus from oropharyngeal specimens, A comparison of tests with fecal samples in monkeys and in tissue culture indicated that the latter was as good as, if not better than, monkeys in detecting poliomyelitis virus.