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Abstract

Objective

To determine the efficacy of leukotoxin-based Fusobacterium necrophorum vaccines and dietary tylosin in providing protection against experimentally induced hepatic abscesses in steers.

Design

30 steers assigned randomly to 6 treatment groups of 5 steers each: 1, phosphate-buffered saline solution (PBSS; control); 2, PBSS control, fed tylosin (100 mg/steer) daily; 3, inactivated whole-cell culture with oil emulsion adjuvant; 4, culture supernatant (crude toxoid) with oil emulsion adjuvant; 5, semipurified leukotoxoid with oil emulsion adjuvant; and 6, semipurified leukotoxoid with saponin adjuvant.

Procedure

Steers were inoculated SC with emulsified antigen or PBSS on days 0 and 21. Blood samples were collected at weekly intervals to monitor serum antileukotoxin antibody titer. On day 42, all steers were challenge exposed intraportally with F necrophorum culture. Three weeks later (day 63), steers were euthanatized and necropsied to examine liver and assess protection.

Results

Antileukotoxin antibody titers of all vaccinated groups markedly increased from baseline values, and mean titers of vaccinated groups were higher than those of the control and tylosin-treated groups. Steers vaccinated with culture supernatant with oil emulsion adjuvant or semipurified leukotoxoid with saponin adjuvant had the highest mean antibody titers. All 5 steers in the control group developed liver abscesses. Tylosin feeding did not protect steers challenge exposed with F necrophorum intraportally.

Conclusions

Culture supernatant was more protective than whole-cell culture or semipurified leukotoxin against experimentally induced hepatic abscesses. Partial purification of leukotoxin appeared to reduce its protective immunity. (Am J Vet Res 1996;57:483–488)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether daily administration of pyrantel tartrate can prevent infection in horses experimentally challenged with Sarcocystis neurona.

Animals—24 mixed-breed specific-pathogen-free weanling horses, 10 adult horses, 1 opossum, and 6 mice.

ProcedureSarcocystis neurona-naïve weanling horses were randomly allocated to 2 groups. Group A received pyrantel tartrate at the labeled dose, and group B received a nonmedicated pellet. Both groups were orally inoculated with 100 sporocysts/d for 28 days, 500 sporocysts/d for 28 days, and 1,000 sporocysts/ d for 56 days. Blood samples were collected weekly, and CSF was collected monthly. Ten seronegative adult horses were monitored as untreated, uninfected control animals. All serum and CSF samples were tested by use of western blot tests to detect antibodies against S neurona. At the end of the study, the number of seropositive and CSF-positive horses in groups A and B were compared by use of the Fisher exact test. Time to seroconversion on the basis of treatment groups and sex of horses was compared in 2 univariable Cox proportional hazards models.

Results—After 134 days of sporocyst inoculation, no significant differences were found between groups A and B for results of western blot tests of serum or CSF. There were no significant differences in number of days to seroconversion on the basis of treatment groups or sex of horses. The control horses remained seronegative.

Conclusions and Clinical Relevance—Daily administration of pyrantel tartrate at the current labeled dose does not prevent S neurona infection in horses. (Am J Vet Res 2005;66:846–852)

Full access
in American Journal of Veterinary Research