Evaluation of the U.S. Department of Agriculture's egg pasteurization processes on the inactivation of high-pathogenicity avian influenza virus and velogenic Newcastle disease virus in processed egg products.

Globally, 230,662 metric tons of liquid egg products are marketed each year. The presence of highly pathogenic avian influenza (HPAI) or Newcastle disease in an exporting country can legitimately inhibit trade in eggs and processed egg products; development and validation of pasteurization parameters are essential for safe trade to continue. The HPAI virus (HPAIV) A/chicken/Pennsylvania/1370/1983 (H5N2) and velogenic Newcastle disease virus (vNDV) AMPV-1/chicken/California/S01212676/2002 were inoculated into five egg products and heat treated at various times and temperatures to determine thermal inactivation rates to effect a 5-log viral reduction. For HPAIV and vNDV, the pasteurization processes for fortified, sugared, plain, and salted egg yolk, and homogenized whole egg (HPAIV only) products resulted in >5-log reductions in virus at the lower temperature-longer times of U.S. Department of Agriculture (USDA)-approved Salmonella pasteurization processes. In addition, a >5-log reduction of HPAIV was also demonstrated for the five products at the higher temperatures-shorter times of USDA-approved pasteurization processes, whereas the vNDV virus was adequately inactivated in only fortified and plain egg yolk products. For the salted and sugared egg yolk products, an additional 0.65 and 1.6 min of treatment, respectively, at 63.3 °C was necessary to inactivate 5 log of vNDV. Egg substitute with fat does not have standard USDA pasteurization criteria, but the D59-value was 0.75 min, adequate to inactivate 5 log of vNDV in <4 min.

Thermal inactivation of avian influenza virus and Newcastle disease virus in a fat-free egg product.

High-pathogenicity avian influenza (HPAI) virus, low-pathogenicity avian influenza (LPAI) virus, virulent Newcastle disease virus (vNDV) and low-virulent Newcastle disease virus (lNDV) can be present on the eggshell surface, and HPAI viruses and vNDV can be present in the internal contents of chicken eggs laid by infected hens. With the increase in global trade, egg products could present potential biosecurity problems and affect international trade in liquid and dried egg products. Therefore, the generation of survival curves to determine decimal reduction times (D(T)-values) and change in heat resistance of the viruses (z(D)-value) within fat-free egg product could provide valuable information for development of risk reduction strategies. Thermal inactivation studies using A/chicken/Pennsylvania/1370/83 (H5N2) HPAI virus resulted in D(55)-, D(56)-, D(56.7)-, D(57)-, D(58)-, and D(59)-values of 18.6, 8.5, 3.6, 2.5, 0.4, and 0.4 min, respectively. The z(D)-value was 4.4 °C. LPAI virus A/chicken/New York/13142/94 (H7N2) had D(55)-, D(56.7)-, D(57)-, D(58)-, D(59)-, and D(60)-values of 2.9, 1.4, 0.8, 0.7, 0.7, and 0.5 min, respectively, and a z-value of 0.4 °C. vNDV avian paramyxoviruses of serotype 1 (AMPV-1)/chicken/California/212676/2002 had D(55)-, D(56)-, D(56.7)-, D(57)-, D(58)-, and D(59)-values of 12.4, 9.3, 6.2, 5, 3.7, and 1.7 min, respectively. The z(D)-value was 4.7 °C. lNDV AMPV-1/chicken/United States/B1/1948 had D(55)-, D(57)-, D(58)-, D(59)-, D(61)-, and D(63)-values of 5.3, 2.2, 1.1, 0.55, 0.19, and 0.17 min, respectively, and a z(D)-value of 1.0 °C. Use of these data in developing egg pasteurization standards for AI and NDV-infected countries should allow safer trade in liquid egg products.

Dose-response of Listeria monocytogenes after oral exposure in pregnant guinea pigs.

Listeriosis, a severe disease that results from exposure to the foodborne pathogen Listeria monocytogenes, is responsible for approximately 2500 illnesses and 500 deaths in the United States each year. Pregnant women are 20 times more likely to develop listeriosis than the general population, with adverse pregnancy outcomes that include spontaneous abortions, stillbirths, and neonatal meningitis. The objective of this study was to determine an infective dose that resulted in stillbirths and infectivity of selected tissues in pregnant guinea pigs. Pregnant guinea pigs were exposed orally on gestation day 35 to 10(4) to 10(8) L. monocytogenes CFU in sterile whipping cream. L. monocytogenes was recovered at 64, 73, 90, and 100% from the livers of animals infected with 10(5), 10(6), 10(7), and 10(8) CFU, respectively. In dams exposed to > or =10(6) CFU, L. monocytogenes was cultured from 50% of the spleen samples and 33% of the gallbladder samples. Eleven of 34 dams infected with > or =10(6) CFU delivered stillborn pups. L. monocytogenes was cultured from the placenta, liver, and brain tissue of all stillbirths. Dams that delivered nonviable fetuses after treatment with > or =10(7) L. monocytogenes CFU had fecal samples positive for L. monocytogenes at every collection posttreatment. On the basis of a log-logistic model, the dose that adversely affected 50% of the pregnancies was approximately 10(7) L. monocytogenes CFU compared with that estimated from a human outbreak of 106 CFU. Listeriosis in pregnant guinea pigs can result in stillbirths, and the overall disease is similar to that described in nonhuman primates and in humans.