Field evaluation of a commercial M-protein vaccine against Streptococcus equi infection in foals.
A double-blind randomized clinical trial was undertaken to determine the value of parenterally administered Streptococcus equi M-protein vaccine in foals during an epizootic of strangles. Weaned mixed-breed foals (n = 664) housed on 2 adjacent feed-lots (A and B) arrived over a 5-day period, 2 weeks before primary vaccination. Foals in lot B (n = 114) were randomly administered vaccine (n = 59) or saline solution (placebo; n = 55) on 3 occasions at biweekly intervals. Foals in lot A (n = 450) were given 1 dose of vaccine (n = 225) or placebo. The following clinical observations were scored blindly by a single observer for all foals in lot B and for 120 (randomly sampled) foals in lot A on a single day, 2 (Lot B) and 6 (lot A) weeks after final vaccination: cervical lymphadenopathy, type of bilateral nasal discharge, and palpable swelling at injection site(s). Bacteriologic culture of nasal swab specimens or lymph node aspirates from selected foals with clinical disease yielded S equi. Cervical lymphadenopathy was observed in 17 of 59 (29%) vaccinates and 39 of 55 (71%) nonvaccinated controls in lot B and in 32 of 60 (53%) vaccinates and 29 of 60 (48%) controls in lot A. Contingency chi 2 analysis confirmed significantly lower cervical lymphadenopathy rate (chi 2 = 18.5; P less than 0.001) and prevalence of mucopurulent nasal discharge (chi 2 = 11.4; P less than 0.01) for vaccinates in lot B only. Swelling(s) at the vaccine injection site were palpated in 44% of lot B and 29% of lot A vaccinates vs less than 2% of placebo controls.(ABSTRACT TRUNCATED AT 250 WORDS)
Hoffman
A M
AM
Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Canada.
Staempfli
H R
HR
Prescott
J F
JF
Viel
L
L
D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000276:immunology; D001428:Bacterial Vaccines; D002352:Carrier Proteins; D003430:Cross-Sectional Studies; D004196:Disease Outbreaks / Q000517:prevention & control*; D004311:Double-Blind Method; D006734:Horse Diseases / Q000517:prevention & control*; D006736:Horses; D008199:Lymphadenitis / Q000517:prevention & control / Q000662:veterinary; D009333:Neck; D013290:Streptococcal Infections / Q000517:prevention & control / Q000662:veterinary*; D013291:Streptococcus / Q000276:immunology*; D014611:Vaccination / Q000662:veterinary
D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D002352:Carrier Proteins; C014689:streptococcal M protein