Vaccines for preventing enterotoxigenic Escherichia coli infections in farm animals.

Fimbrial vaccines are routinely given parenterally to pregnant cattle, sheep and swine to protect suckling newborn calves, lambs and pigs against enterotoxigenic Escherichia coli (ETEC) infections. Such vaccines are practical and effective because (1) most fatal ETEC infections in farm animals occur in the early neonatal period when the antibody titres in colostrum and milk are highest; (2) more than 90% of the ETEC in farm animals belong to a small family of fimbrial antigen types; (3) fimbriae consist of good protein antigens on the bacterial surface where they are readily accessible to antibody; (4) fimbriae are required for a critical step (adhesion-colonization) early in the pathogenesis of the disease. ETEC infections continue to be a significant clinical problem in farm animals in spite of extensive use of fimbriae-based vaccines. Definitive data on the efficacy of the commercial vaccines in field use are not available. The prevailing perception among animal health professionals is that the vaccines are effective, that the problem occurs chiefly among non-vaccinated animals, and that in some herds vaccination moves peak prevalence of disease from the first to the second or third week after birth, when mortality is lower. It has been suggested that extensive use of vaccines will rapidly select for the emergence of novel or previously low prevalence fimbrial antigen types. There is no evidence that this has happened after a decade of routine vaccine use in the United States. However, there is no active direct surveillance for such emergence.(ABSTRACT TRUNCATED AT 250 WORDS)

Testing of veterinary biologics in the United States.

The National Veterinary Services Laboratories (NVSL) in Ames, Iowa, are responsible for the confirmatory testing of veterinary biologics produced in the United States and regulated by the United States Department of Agriculture. There were 22.101 serials of biological products produced and submitted to the NVSL during fiscal year (FY) 1991 (October 1, 1990, to September 30, 1991). All serials were tested by the manufacturer; and 2.086 (9.44 percent) were also tested by the NVSL for purity, safety, or potency of at least one component. Of the serials tested, 97.84 percent were found to be satisfactory. The total number of tests conducted during FY 1991 was 4.283. The criteria for establishing test rates and test methods are discussed. In addition to the testing of finished biological products, the NVSL tested 129 bacterial or viral master seeds and 31 master cell stocks during FY 1991 for identity and freedom from extraneous bacterial and viral agents. These master seeds and master cell stocks will be used to make future biological products.

Comparison of in vitro replication and cytopathology caused by strains of canine distemper virus of vaccine and field origin.

Three biological properties of canine distemper virus were examined to determine if any would consistently differentiate field from vaccine strains of the virus. The properties were the ability to (1) infect macrophages and epithelial cells, (2) produce distinct cytopathologic effect in alveolar and peritoneal macrophages and Vero cells, and (3) produce pocks on the chorioallantoic membrane of embryonated chicken eggs. Four vaccine strains and 5 field isolates were used in the study. The 5 field isolates were obtained directly from canine tissues. Of the 3 properties studied, only the comparison of the ability of the viruses to infect macrophages and epithelial cells was a consistent marker of virus origin. Virulent field isolates would only infect macrophage cultures, whereas the vaccine strains infected both types of cells. One avirulent field isolate from a case of old dog encephalitis reacted more like a vaccine strain by infecting both cell types.

Antigenic relationships among autonomous parvoviruses.

The antigenic relatedness of minute virus of mice (MVM), Kilham rat virus (KR), H-1 virus (H-1), haemorrhagic encephalopathy of rats virus (HER), porcine parvovirus (PPV), canine parvovirus (CPV), feline panleukopenia virus (FPV), goose parvovirus (GPV) and bovine parvovirus (BPV) was studied by immunofluorescence microscopy (FA) and by serum neutralization (SN). An antigenically related group comprising MVM, KR, HER, PPV, CPV and FPV was recognized by FA and most reactions within the group were reciprocal. Antigenic relatedness was less evident when the same viruses and antisera were tested by SN. Only CPV and FPV were closely and reciprocally related. Other cross-reactions by SN were quantitatively minor and included neutralization of CPV and FPV by pig anti-PPV serum and neutralization of H-1 and HER by rat anti-KR serum. Neither FA nor SN revealed any antigenic relationship of BPV and GPV either with each other or with any of the other viruses tested.

Use of monoclonal antibodies to confirm vaccine-induced rabies in ten dogs, two cats, and one fox.

A panel of 8 monoclonal antibodies to rabies glycoprotein antigen was used to characterize the modified-live virus vaccines marketed in the United States during the last 10 years. Thirteen of 14 rabies virus isolates from 11 dogs, 2 cats, and 1 fox suspected of developing vaccine-induced rabies were shown to have reactivity patterns that were identical to the vaccine administered. Reactivity patterns for 20 rabies isolates from human beings, wild animals, or domestic animals with no history of recent vaccination with modified-live virus rabies vaccine were different from those obtained for vaccines.

Rabies induced in a cat by high-egg-passage Flury strain vaccine.

An adult male domestic short-hair cat developed posterior paralysis 22 days after being vaccinated for rabies with a high-egg-passage Flury strain vaccine currently approved for use in cats. A diagnosis of rabies was confirmed by mouse inoculations, and viral typing using a panel of monoclonal antibodies demonstrated that it was vaccine induced.

Canine distemper virus titration in ferret peritoneal macrophages.

The sensitivity of a ferret peritoneal macrophage fluorescent antibody technique for assay of various strains of canine distemper virus was investigated. The macrophage system was compared with established methods of titration in canine kidney cell culture, Vero cell culture, and embryonated chicken eggs. It was found to be as sensitive as and in several instances more sensitive than the established methods.

Efficacy of inactivated tissue culture rabies vaccine in dogs.

Inactivated, nonadjuvanted tissue culture-origin rabies vaccine was tested in 168 dogs for its ability to provide protection against challenge of immunity 1 year after vaccination. Several laboratory methods were used concurrently to measure the potency of the vaccine. When used at full strength, the vaccine protected 70% of dogs after either a 1- or 2-dose vaccination schedule. When vaccine was diluted to contain less antigenic mass, the 1-dose schedule was not as effective as 2 doses. High serum-neutralizing antibody titers developed by 7 days after vaccination, but the titers declined rapidly thereafter. The US reference vaccine protected 28 of 30 dogs.