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in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association

Summary

Of swine from 104 herds, 2,616 were tested for antibodies against Toxoplasma gondii, using an elisa. Data were analyzed according to swine type, herd size, facility type, and season. The true prevalence of toxoplasmosis was estimated as 5.4% among finishing swine and 11.4% among sows and gilts. Herds with <100 breeding swine were significantly (P < 0.05) more likely to be infected than were herds with ≥100 breeding swine. The rate of seropositivity in breeding swine was approximately the same in infected herds, regardless of herd size. Herds with finishing swine maintained in total confinement were as likely to become infected as were herds maintained in other types of facilities, but infected herds with finishing swine maintained in confinement appeared to have a lower in-herd prevalence than did herds maintained in other types of facilities (P = 0.09). Seasonal effects were not observed, and prevalence remained relatively constant throughout the year.

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To genetically type Campylobacter jejuni isolates from broiler houses or the external environment to identify the source of Campylobacter organisms in broiler chickens.

Sample Population—Environmental samples associated with broiler chickens, in commercial grow-out houses.

Procedure—Polymerase chain reaction (PCR) was used to amplify flaB, and the amplicon was digested with Sau3A to create a restriction fragment length polymorphism assay; PCR was also used to detect a transcribed spacer region in the 23S rRNA gene.

Results—Isolates possessing a 23S spacer region were more prevalent outside broiler houses than inside. Houses that had previously contained chickens or lacked biosecurity procedures were more likely to contain isolates possessing the 23S spacer. One house contained only isolates possessing the spacer, whereas an adjacent house contained only isolates lacking the spacer. The flaB type detected in broiler houses was different from the type detected in the environment; however, many isolates within the broiler houses contained untypable flaB genotypes.

Conclusions and Clinical Relevance—Most isolates from within houses were genetically distinct from isolates from outside houses that were examined by bacteriologic culture, suggesting an undetected source of C jejuni. Detection of isolates containing the 23S spacer appeared to be an indicator of environmental contamination of the houses. The observation of completely different C jejuni genetic types simultaneously within adjacent houses suggests that some types do not compete successfully during the grow-out period. In addition, the diversity of genotypes identified within broiler houses indicates the complexity of the ecologic features of C jejuni in the chicken environment. (Am J Vet Res 2001;62:190–194)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the effect of various routes of administration and number of doses of 3 commercially produced rabies vaccines on serum antibody responses and protection in mice challenged by intracerebral injection with fixed-strain rabies virus.

Animals—2,213 mice.

Procedure—Inactivated, adjuvanted rabies vaccines were administered to mice in either 2, 1, or 0 (control) doses via IP, IM, and SC routes, and mice were challenged intracerebrally with fixed-strain rabies virus.

Results—Vaccination route and dose number significantly influenced serum antibody responses and protection from rabies virus challenge, independent of vaccine strain origin and mouse strain, although mouse age significantly affected results. Extended challenge studies revealed that IM vaccination of mice resulted in the highest serum neutralizing antibody responses and protection levels equivalent to IP vaccination. Even multiple doses administered SC (a vaccination route used in dogs) resulted in poor serum anti-rabies neutralizing antibody responses in mice and were far less protective than other routes.

Conclusions and Clinical Relevance—Findings suggest possible improvements for the current rabies vaccine potency test in mice by using 1 dose, the IM route, and a delayed time of challenge. These modifications would more closely model vaccination practices in target species and yield more accurate information regarding primary immunogenicity of a vaccine. (Am J Vet Med 2003;64:491–498)

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in American Journal of Veterinary Research

Abstract

Objective—To determine effect of route of challenge and strain of rabies virus on efficacy of inactivated rabies vaccines in mice.

Animals—3,056 mice.

Procedure—Challenge was performed with fixed and street rabies virus strains by use of footpad and intracerebral routes as well as IM injection into the hip, shoulder, neck, and masseter muscles. Intraperitoneal and IM vaccination was performed with 1 or 2 doses of 1 of 3 vaccine-strain inactivated rabies vaccines. For 2 of the vaccine strains, the vaccines were adjuvanted and nonadjuvanted.

Results—Incubation periods were dependent on route, dose, and virus strain used for challenge. Use of an intramasseter challenge route with challenge virus-strain rabies virus, which more accurately models natural exposure to rabies virus, resulted in reproducible mortality rates in mice. Use of this route revealed that differences among vaccines and challenge virus strains affected mortality rate less than that observed in the National Institutes of Health potency test, even when street isolates of widely variant origin were used for challenge.

Conclusions and Clinical Relevance—These results, combined with earlier data, support a proposal for a new rabies potency test that more closely models current vaccine administration practices and natural infection routes. (Am J Vet Res 2003;64:499–505)

Full access
in American Journal of Veterinary Research
in Journal of the American Veterinary Medical Association

SUMMARY

Objective

To determine susceptibility, incubation and morbidity periods, clinical signs, serologic response, and excretion of virus in domestic ferrets inoculated with rabies virus.

Animals

55 domestic ferrets.

Procedure

5 groups of 10 ferrets were inoculated with rabies virus, IM, at doses of 105.5 to 101.5 median mouse intracerebral lethal dose. Ferrets were observed and behavior was recorded. Rectal temperature, body weight, and samples from the oral cavity and samples of saliva and blood were obtained. Virus isolation was attempted, using intracranial mouse inoculation and cell culture. Virus neutralizing antibodies were determined by rapid fluorescent focus inhibition test. Ferrets were euthanatized immediately if clinical signs were severe. Rabies was confirmed by direct immunofluorescent antibody test.

Results

Mean incubation period was 33 days (range, 16 to 96 days). Clinical signs included ascending paralysis, ataxia, cachexia, bladder atony, fever, hyperactivity, tremors, and paresthesia. Mean morbidity period was 4 to 5 days (range, 2 to 10 days). Virus antigen was detected in brain tissue from all clinically rabid ferrets. Ferrets given the highest viral dose were euthanatized and had VNA; ferrets receiving the next dilution also were euthanatized, but only 4 had seroconverted. Of 17 ferrets that survived, 5 seroconverted. Survivors remained clinically normal except for 1 that recovered with severe paralytic sequelae. Rabies virus was isolated from the salivary gland of 1 ferret that was euthanatized.

Conclusions and Clinical Relevance

Rabies should be considered as a differential diagnosis in any ferret that has acute onset of paralysis or behavioral changes and a condition that rapidly deteriorates despite intense medical intervention. (Am J Vet Res 1997;58:1327–1331)

Free access
in American Journal of Veterinary Research