The use of meso-erythritol sensitivity discs in the typing of Brucella strains.

Sensitivity discs containing 1 and 2 mg meso-erythritol were found to give comparable results to the use of meso-erythritol incorporated into growth medium at 1 and 2 mg/ml. The discs proved easy and efficient when used in a disc ring together with benzyl penicillin and streptomycin sulphate discs.

Brucellosis serology: reduced dose S19 vaccination of yearling heifers versus the use of the standard dose at 5-7 months of age in a clean herd.

In the 427 heifers vaccinated at 12 to 14 months of age with the reduced dose (3 X 10(8) to 1 X 10(9) viable organisms per dose) 3 had antibody titres in the complement fixation test of 196, 688 and 748 IU ml-1, respectively, at 5 months post-inoculation. At 23 to 25 months of age 8/128 (6.3%) of these heifers had rose bengal test (RBT) reactions, at least 6/128 (4.7%) a serum agglutination test (SAT) antibody titre in excess of 30 IU ml-1 and 1/128 had a suspicious reaction in the complement fixation test (CFT) of 30 to 49 IU ml-1. In the 116 heifers inoculated with the standard dose (4 to 12 X 10(10) viable organisms) at 5 to 7 months of age and tested at 22 to 24 months of age, a reactor rate of 37/116 (31.9%) in the RBT was seen. At least 34/116 (29.3%) had antibody titres in excess of 30 IU ml-1 in the SAT. Only 1 animal had a suspicious reaction in the CFT of 18 to 24 IU ml-1. No abortions could be attributed to the vaccine strain and no other isolates of the vaccine strain were made. The possible role of vaccine residues in syringes as a cause of persistent reactions is discussed. The use of disposable syringes is recommended. On serological grounds there appears to be little advantage in using the reduced dose vaccine in yearling heifers as opposed to the standard dose vaccination of 5 to 7 month old heifers.

The use of a single complement fixation test technique in bovine brucellosis, Johne's disease, dourine, equine piroplasmosis and Q fever serology.

The same techniques may be used in the complement fixation test (CFT) for the serological diagnosis of bovine brucellosis, Johne's disease (paratuberculosis), dourine, equine piroplasmosis and Q fever (caused by Coxiella burnetii). The reproducibility of results is excellent, falling for the most part within the twofold range and never exceeding the fourfold range. Agreement with other laboratories is excellent (i.e. within twofold) in the case of brucellosis and equine piroplasmosis antibody titres. A good correlation between the occurrence of the disease and serological reactions is found on circumstantial evidence in the cases of dourine, Johne's disease and Q fever. A standard unitage system is used to report the antibody titres found in all the tests. To simplify laboratory protocols, laboratories required to employ the CFT for the diagnosis of these diseases are advised to use a single proven technique in all the tests. Problems experienced with transient false-positive Johne's disease antibody titres in cattle following on tuberculin (bovine and avian) testing make it advisable to take specimens for the Johne's disease test prior to performing the tuberculin tests.

Profiles of serological reactions following adult cow inoculation with standard dose Brucella abortus strain 19 vaccine.

Experimental use of the standard dose (4-12 X 10(10) viable organisms per dose) Brucella abortus strain 19 vaccine (S19) in adult cattle led to a serological response in the complement fixation test (CFT) within 2 weeks. The antibody titres recorded could not be distinguished from those arising from infection for a period of 6-11 months. This was in the absence of the booster effect of Brucella antigen from either field or vaccine strains. The illegal or unintentional use of S19 in adult cattle may be recognized by a sudden steep antibody titre response in the CFT which will decline to negative levels within 6-11 months provided no booster Brucella antigen is present.

Leptospira interrogans serovar hardjo associated with bovine abortion in South Africa.

Leptospira interrogans serovar hardjo was isolated from urine from dairy cattle in the Onderstepoort area. This was the first successful isolation of this serovar as sole agent causing an abortion storm in the Republic of South Africa. Abortions occurred as early as at 4 months' gestation.

Addition of rabbit serum to EMJH medium improves isolation of Leptospira interrogans serovar hardjo.

The addition of 2% pooled rabbit serum to semi-solid commercial EMJH medium with EMJH enrichment and 0,5 mg of 5-fluorouracil per ml was found to enhance the growth rate and success of isolation of Leptospira interrogans serovar hardjo from bovine urine. Cultures made on media without serum had to be kept for more than 130 days before being discarded as negative.

On the inactivation of Brucella abortus in naturally contaminated milk by commercial pasteurisation procedures.

Following concern about the recent publication indicating the possible ability of Brucella abortus to survive commercial pasteurisation of naturally contaminated milk, such milk was subjected to biological (BT), serological and bacteriological tests. The raw milk was Brucella Milk Ring Test positive and biotype I was isolated from 4/5 BT guinea pigs, the one tested being seropositive to the Rose Bengal Test, and with serum agglutination and complement fixation titres of 160 and 36 international units respectively. After batch (63 degrees C/30 min) and high temperature, short time (72 degrees C/15 sec) pasteurisation, all 10 BT guinea pigs were bacteriologically and serologically negative, indicating that officially approved methods of commercial pasteurisation rendered naturally Brucella-contaminated raw milk safe for consumption.