Evaluation of the presence and risk of foot and mouth disease virus by commodity in international trade.

Potential sources of foot and mouth disease (FMD) virus include semen from bulls, rams, goats and boars; embryos and ova from ruminants and pigs; meat and meat products and milk and milk products. The author discusses precautions to prevent the transmission of FMD via these commodities.

Vesicular exanthema of swine virus: isolation and serotyping of field samples.

Virus isolation was attempted from 262 field samples of vesicular material collected during the outbreaks of vesicular exanthema of swine in the U.S.A. from 1952-54. Using primary swine kidney culture, viral cytopathogenic agents were isolated from 76.3% of the samples. However, an overall recovery rate of 82.1% was obtained after samples negative in tissue culture were inoculated intradermally in susceptible swine. All vesicular exanthema of swine virus isolates were identified as serotype B51 using complement fixation and serum neutralization tests. Two isolates did not react with antisera to known vesicular agents of swine and failed to produce vesicles or clinical signs of disease upon inoculation in swine. One vesicular exanthema of swine virus isolate from tissue of equine origin was pathogenic for swine but produced limited vesiculation at the site of intradermalingual inoculation in the tongue of a pony infected experimentally. Type B51 virus was reisolated from lesions produced in the pony and the pony became seropositive for virus type B51.

Dose-response evaluation of a genetically engineered foot-and-mouth disease virus polypeptide immunogen in cattle.

Four groups of 9 cattle each were vaccinated with 10, 50, 250, or 1,250 micrograms of foot-and-mouth disease (FMD) virus A12 VP1 fusion protein that was produced in Escherichia coli and emulsified in an oil adjuvant. The groups given the 10 and 50 micrograms of antigen were revaccinated at 15 weeks and were challenge exposed at 30 weeks; 5 of 9 and 7 of 9 cattle, respectively, were protected from FMD virus infection. The remaining 2 groups, vaccinated with 250 or 1,250 micrograms of antigen, were revaccinated at 32 weeks and were challenge exposed at 45 weeks; 8 of 9 and 9 of 9 cattle, respectively, were protected. The results indicated that the biosynthetic polypeptide FMD vaccine was effective using vaccination intervals frequently followed with conventional whole-virus vaccines.

Effect of pasteurization and evaporation on foot-and-mouth disease virus in whole milk from infected cows.

The effects of pasteurization and evaporation on foot-and-mouth disease virus in whole milk from infected cows obtained one day postinoculation were studied. Virus survived the heating of milk at high temperature-short time pasteurization at 75 degrees C for 15-17 seconds. In addition, virus from infected milk survived heating at 80 degrees C for the same time. Infective virus also survived in the pasteurized milk after evaporation at 65 degrees C to 50% of the original volume. The bovine udder was found to be highly susceptible to foot-and-mouth disease virus replication. Seven log10 plaque-forming units/ml of virus were recovered in whole milk 24 hours postinoculation, and decreasing titers were recovered for as long as seven days postinoculation.

The thermal death time curve for foot-and-mouth disease virus contained in primarily infected milk.

Whole and skim milk obtained from cows after intramammary and intravenous inoculation with foot-and-mouth disease virus (primarily infected milk) were exposed to various temperatures ranging from 80 to 148 degrees C for various times ranging from 2.5 s to 27 min then tested for viral infectivity. The average pretreatment titre of the 53 lots of milk used was 10(5.9) plaque-forming units of virus per millilitre 10(3.7)-10(6.8)). A thermal death time curve was plotted using the data obtained. The curve demonstrates that in order to inactivate the virus, times of over 20 min are necessary at 'low' temperatures (100 degrees C) while 2.5 s is sufficient at a temperature of 148 degrees C.

Foodborne Viruses: Their Importance and Need for Research 1.

All viruses known to be normally transmissible through foods and of concern to human health emanate from the human intestine. The outbreaks of hepatitis A and recently of gastroenteritis attributed to Norwalk-like viruses most likely developed from feces-contaminated fingers of infected food handlers or water polluted with feces. With few exceptions no recorded outbreak has depended on the ability of virus to withstand even limited heating in food. New and better methods of detection are needed for hepatitis A and Norwalk viruses in foods. It has been well documented that international trade in food products of animal origin can result in the introduction of animal disease into areas in which the disease does not exist. This fact has given rise to programs of research and development for industrially applicable technology to rid animal products from the agents of animal diseases. The survival of viruses inclusive of etiological agents of foot-and-mouth disease, African swine fever, swine vesicular disease and hog cholera virus is reviewed in this paper and new research approaches are suggested. The general need for additional research of foodborne viruses is discussed.