A comparison of diagnostic assays for the detection of type A swine influenza virus from nasal swabs and lungs.

Nasal swabs and lung samples from pigs experimentally infected with H1N1 swine influenza virus (SIV) were examined for the presence of SIV by the indirect fluorescent antibody assay, immunohistochemistry, cell culture virus isolation, egg inoculation, and 2 human enzyme immunoassays (membrane enzyme immunoassay, microwell enzyme immunoassay). Egg inoculation was considered to be the gold standard for assay evaluation. The 2 human enzyme immunoassays (EIA) and egg inoculation agreed 100% for the prechallenge nasal swabs. Agreement on SIV identification in nasal swabs with egg inoculation following challenge was considered to be good to excellent for membrane EIA (kappa = 0.85) and microwell EIA (kappa = 0.86). Agreement on SIV identification in lung tissue with egg inoculation following challenge was good to excellent for membrane EIA (kappa = 0.75), fair for microwell EIA, fluorescent antibody, and cell culture virus isolation (kappa = 0.48, 0.64, 0.62, respectively), and poor for immunohistochemistry (kappa = 0.36). No assay was 100% accurate, including the "gold standard," egg inoculation. In light of this information, it is important to consider clinical signs of disease and a thorough herd history in conjunction with diagnostic results to make a diagnosis of SIV infection.

Protective efficacy of a recombinant herpesvirus of turkeys as an in ovo vaccine against Newcastle and Marek's diseases in specific-pathogen-free chickens.

We investigated the potential of a herpesvirus of turkey (HVT)-based recombinant virus (rHVT) as an in ovo vaccine to protect specific-pathogen-free chickens against Newcastle disease (ND) and Marek's disease (MD). The rHVT, designed to express fusion (F) and hemagglutinin-neuraminidase (HN) glycoproteins of the lentogenic Hitchner B1 strain of ND virus (NDV), as well as glycoproteins A and B of the GA strain of serotype 1 MD virus (MDV) was efficacious in protecting chickens against ND and MD. No adverse effects on hatchability or the survival of chickens were observed following in ovo vaccination with rHVT. A single administration at embryonation day 18 (ED18) or at hatch protected chickens against challenge-exposures with virulent MDV strain RB-1B and velogenic NDV strain GB-Texas (NDV-GB-TX). Vaccinated chickens developed antibodies against both viruses as detected by serological tests, namely, hemagglutination inhibition, virus neutralization and western immunoblotting for NDV, and immunofluorescence and radioimmunoprecipitation assays for MDV. PCR analysis showed that in ovo vaccination with rHVT resulted in a persistent infection leading to systemic immunity against ND for up to 8 weeks of age, the longest period of time tested in this study. However, virus isolation tests indicated that rHVT-vaccinated chickens were only partially protected from the replication of NDV-GB-TX in the trachea. The results of the study indicate that rHVT is safe for both ED18 and posthatch vaccination for ND and MD, and because the vaccine persists, it may induce longer lasting immunity than conventional live NDV vaccines.

The safe and effective use of fowlpox virus as a vector for poultry vaccines.

The safety and efficacy of a fowlpox-Newcastle disease vaccine were evaluated by in vitro and in vivo methods. Genetic and phenotypic stability following cell culture and chick passage were demonstrated. The safety characteristics of the recombinant virus equalled or exceeded those of the parent fowlpox virus, as determined by lack of shed and spread to contacts, failure to revert to virulence following passage in chicks and innocuity in other avian species. The fowlpox-Newcastle Disease virus effectively immunized against virulent fowlpox challenge and virulent Newcastle disease challenge (intramuscular or intra-ocular administration). These results indicate that the recombinant FPV/NDV virus is a safe and effective vaccine for poultry.

Canine parvovirus serum neutralizing antibody assay: assessment of factors responsible for disparity of results between tests.

Canine parvovirus (CPV) serum neutralization (SN) test components were evaluated to determine their effect on antibody titer results. The use of different strains of CPV and different cell substrates had little effect on assay results. Variations in SN antibody titer results were associated with the use of challenge virus preparations that differed in the ratio of hemagglutination units (HAU) to infectivity units (FAID50). Sensitivity and reproducibility can be achieved by using a standardized challenge virus preparation containing a low HAU/FAID50 ratio.