The persistence of serological reactions following heifer vaccination with Brucella abortus strain 19 on brucellosis-free farms.
Of 392 heifers vaccinated between 4 and 9.5 months of age and tested at 22 months or older, 3 (0.77%) had titres in the complement fixation test of between 30 and 98 international units per millilitre. The results confirm that persistent serological reactions can be a problem even in brucellosis-free herds. To reduce the incidence of these problem reactors, it is suggested that: in clean herds the age of inoculation be reduced to 3 months of age; the age at first testing be delayed as long as possible, but be done before the heifers are 4 months pregnant, c) consideration be given to reducing the vaccine dose for all heifers from the present 4 to 12 x 10(10) to between 3 x 10(8) and 3 x 10(9) and syringes used for strain 19 vaccination be exclusively reserved for this purpose to prevent the possibility of antigenic residues acting as a booster when used for other vaccinations.
Herr
S
S
Veterinary Research Institute, Onderstepoort, Republic of South Africa.
Ehret
W J
WJ
Ribeiro
L M
LM
Chaparro
F
F
D000367:Age Factors; D000818:Animals; D002003:Brucella abortus / Q000276:immunology*; D002007:Brucellosis, Bovine / Q000276:immunology*; D002417:Cattle; D003168:Complement Fixation Tests; D005189:False Positive Reactions; D005260:Female; D012395:Rose Bengal; D013997:Time Factors; D014611:Vaccination / Q000662:veterinary
D012395:Rose Bengal