Control of Brucella melitensis infection in sheep and goats--a review.
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Biomedical subjects
G G Alton
Publications and source records attributed to G G Alton.
Distribution of Brucella abortus in infected cattle.
Experimentally and naturally infected cattle were examined bacteriologically to determine the anatomical distribution of specimens yielding Brucella abortus. In 91 experimentally infected pregnant cows, examined 3 to 4.5 months after conjunctival challenge during pregnancy, the most frequently infected specimen was the mammary (syn. supramammary) lymph node. All experimentally infected cows could be identified from cultures of the mammary, mandibular (syn. submaxillary), medial iliac, caudal superficial cervical (syn. prescapular) lymph nodes and uterine caruncles, cotyledons or foetal tissues. Forty-six naturally infected cows were examined and again the most frequently infected specimen was the mammary lymph node. All naturally infected cows could be identified from cultures of the mammary, parotid, mandibular and subiliac (syn. prefemoral) lymph nodes. The distribution of infected specimens was somewhat different in heifers. In 61 naturally infected heifers the most frequently infected specimen was the mandibular lymph node but 8 other specimens would have been required to enable identification of all infected heifers. Specimens from 3 infected bulls were cultured and 11 of the 12 specimens examined were infected in at least one of the bulls. The most frequently infected tissues were the mandibular, caudal superficial cervical, subiliac and scrotal lymph nodes. The results suggest which specimens should be selected for culture, particularly when only a limited amount of effort can be expended.
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An evaluation of a biphasic medium for the isolation of Brucella abortus from bovine tissues.
The isolation of virulent Brucella abortus from specimens taken from cattle was studied using culture in biphasic medium in which solid and liquid media were contained in the same flask and on solid medium in Petri plates. A total of 8638 specimens from 441 cattle, reactors to one or more of several serological tests or to an allergic test, were used. The specimens consisted of lymph nodes, udder, spleen, uterine caruncles, cotyledons, foetal tissues, foetal stomach contents and mammary secretions. Following maceration each specimen was inoculated into 2 flasks of biphasic medium one with 1 ml (Flask A) and the other with 2 ml (Flask B), and on to solid medium in one Petri plate. The biphasic medium and solid medium were shown to have equal ability to support the growth of B. abortus. The increased rate of detection in the biphasic medium was due to the increased volume of the inoculum used. Brucella were isolated from 1151 specimens. By direct plating on the solid medium 685 specimens were positive whereas Flask A positive for 961 specimens and Flask B for 1031 specimens. The success of the biphasic medium can be judged by the increase in the number of infected animals detected. Of the 150 infected cattle, both techniques identified 126 animals in common, 4 were identified only by the plate technique and 20 only by the biphasic technique. Culture on both solid medium and in biphasic medium is recommended for optimum results.
Animals↗
Vaccination against bovine brucellosis.
Four experiments are summarized. Initially an attempt was made to modify strain 19 calfhood vaccination so as to eliminate the persistent serological reactions which interfere with eradication programmes. Later the project broadened into a search for an effective method of vaccination that could be applied when required, to all ages of cattle, thus allowing calfhood vaccination to be safely stopped. In the first experiment, reducing the age at vaccination with strain 19 to 1 month practically eliminated the serological response to vaccination, but the resulting immunity was not satisfactory. However, vaccination at 1 month followed by a booster consisting of a reduced dose of strain 19, given conjunctivally 1 year later, stimulated an immunity at least equal to that given by conventional calfhood vaccination. The vaccination of pregnant cows with either of 2 reduced dose levels of strain 19 gave better immunity than calfhood vaccination with the full dose. Uterine strain 19 infections were unacceptably frequent in cows given 6 X 10(9) c.f.u. of strain 19 in early pregnancy, but no such infections were found in 9 cows given 3 X 10(8) c.f.u. Vaccinal antibody titres declined rapidly in the latter group. Vaccination of mature, non-pregnant heifers with 3 X 10(8) c.f.u. of strain 19 produced immunity at least as good as that produced by calfhood vaccination, with a serological response greatly reduced in the majority of cattle. However, a small proportion of vaccination cattle developed high titres persisting for at least 7 months.(ABSTRACT TRUNCATED AT 250 WORDS)
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An evaluation of the anamnestic test for brucellosis in cattle of the northern pastoral area.
An investigation of the anamnestic test for brucellosis using Brucella abortus 45/20 vaccine was carried out in 3 groups of weaner cattle on 2 farms in western Queensland. Each group originally consisted of about 500 cattle. They were bled before and at 6 or 10 weeks after vaccination and again in the following year. The serums were tested by the complement fixation (CFT), Rose Bengal (RBT) and indirect haemolysis tests (IHLT). Most of the cattle reacting to one or more of the tests were killed and selected tissues were subjected to bacteriological examination for B. abortus. B. abortus was isolated from 19 of 30 (63%) pre-vaccinal reactors, 23 (24%) of 96 cattle reacting at 6 or 10 weeks after vaccination (the anamnestic test) and 1 (2%) of 50 cattle reacting one year after vaccination. The reactor found to be infected the year after vaccination had high serological titres in each of the 3 serological tests: RBT of 3, CFT of 128 and IHLT of 256. A subsequent test showed the group to be brucellosis-free. The CFT was the most efficient test. In the pre-vaccination tests 17 of 19 infected animals were positive in the CFT compared with 11 positive in the IHLT and 17 in the RBT. In post vaccination tests 22 of 23 infected animals were positive in the CFT compared with 18 in the IHLT and 19 in the RBT. At the pre-vaccinal and anamnestic tests (6 or 10 weeks after vaccination) 19 of 57 (33%) cattle with CF titre of 4 or 8 yielded B. abortus on culture compared with none of 26 cattle with similar titres in the year after vaccination. The interpretation of CF titres in cattle following 45/20 vaccination needs to be re-examined.
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The role of the differential complement fixation test, using rough and smooth brucella antigens, in the anamnestic test.
To assess the ability of the differential complement fixation test to distinguish vaccinal reactors from infected cattle, approximately 1,000 heifers were tested by the complement fixation test (CFT) using rough and smooth brucella antigens, before the injection of 45/20 vaccine and at 3 and 6 or 10 weeks after vaccination. Before vaccination 91.5% of heifers were negative to the rough antigen but 0.6% were positive with high titre (greater than or equal to 128). By 10 weeks after injection of 45/20 vaccine 97.6% of heifers were positive to the rough CF antigen, at greater than or equal to 8, a majority reaching greater than or equal to 128. Nineteen pre-vaccinal reactors to the standard CFT were killed and Brucella abortus was isolated from the tissues of 14. Twenty-six post-vaccinal reactors were killed and B. abortus was isolated from the tissues of 8. In the 22 B. abortus infected animals the differential CFT classified 9 correctly as infected, 5 incorrectly as vaccination reactions and 8 as inconclusive. The differential CF was ineffective in distinguishing titres resulting from vaccination with 45/20 vaccine from those due to infection.
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Vaccination of cattle against brucellosis using either a reduced dose of strain 19 or one or two doses of 45/20 vaccine.
Three groups, each of 14 mature Jersey heifers, were vaccinated. They were mated about 2 months later and those that became pregnant were challenged at about 6.5 months of pregnancy by the conjunctival application of virulent Brucella abortus. Group 1 heifers received 2 doses of B. abortus 45/20 vaccine 2 months apart. Only 5 of the 14 heifers became pregnant, and of these 5 only one resisted challenge. Group 2 heifers received only one dose of 45/20 vaccine, 5 of the 10 challenged resisted infection. Group 3 heifers received 3 x 10(8) cfu of strain 19. Six of the 10 heifers challenged resisted infection. All of 5 non-vaccinated control cattle became infected. It appeared advantageous to give only one dose of 45/20 rather than 2 as presently recommended. A single dose of 45/20 vaccine induced resistance to virulent B. abortus approximately equal to that given by the reduced dose of strain 19. One dose of 45/20 vaccine stimulated transient serological positivity in 2 of 28 heifers whereas the reduced dose of strain 19 gave rise to persistent titres in 2 of 14 vaccinated heifers.
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Vaccination of heifers with a reduced dose of brucella abortus strain 19 vaccine before first mating.
Ten Jersey heifers aged 14 to 23 months were vaccinated with 2.25 x 10(8) cells of living Brucella abortus strain 19 vaccine. They and 10 similar non-vaccinated heifers were subsequently mated and when about 6 months pregnant were challenged by the conjunctival application of a virulent culture of B. abortus. The serological responses to vaccination was much less than is usually seen following vaccination with the normal dose of strain 19, especially when the indirect haemolysis test was used. A persistent vaccinal reaction was observed in one heifer. Significant resistance to infection was demonstrated which was greater than that previously observed in calfhood vaccinates given the full dose but less than that shown by cows given the smaller dose in early pregnancy. The effectiveness of strain 19 vaccination appears to be related to the age of the animal at vaccination.
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Persistence of Brucella abortus strain 19 infection in adult cattle vaccinated with reduced doses.
Brucella abortus strain 19 was recovered at necropsy from cows vaccinated with reduced doses of strain 19, three to six months previously. Strain 19 was isolated from four of nine cows vaccinated with 5.8 x 10(9) viable cells during pregnancy. In two of these nine cows vaccination had led to colonisation of the uterus with erythritol-utilising mutants of strain 19 and consequent abortion or premature calving. In one of another group of nine pregnant vaccinated with 2.8 x 10(8) viable cells, the vaccine strain was recovered from the colostrum. There was no interference with the course of pregnancy in over 700 cattle vaccinated with 3 x 10(8) viable cells. Thirteen of these cows, serologically positive approximately three months after vaccination, were necropsied and strain 19 was isolated from six. This lower dose has already been shown to produce immunity equal to that of higher doses and is recommended as suitable for whole herd vaccination.
Abortion, Veterinary↗
The indirect haemolysis test (IHLT) for bovine brucellosis - comparisons with the complement fixation test (CFT) in vaccinated and experimentally infected cattle.
Cattle were vaccinated with Brucella abortus strain 19 subcutaneously in doses ranging from the normal (2.0 ml) dose of standard vaccine down to 1/400 of the normal dose, and via the conjunctival sac with 1/2 of 1/20 of the normal dose. Under all vaccination regimes serum antibody titres in the complement fixation test (CFT) rose more rapidly, reached higher levels, declined more slowly and involved a greater proportion of animals, than titres in the indirect haemolysis test (IHLT). The interval between the first positive serological test and parturition was determined for 54 pregnant cows infected with a virulent field strain (VRI 3) of B. abortus. On average the CFT titre rose to 1/4 43 days, and 1/8 33 days, before parturition, while the IHLT reached a 2/8 reaction 31 days before parturition.
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Failure of a single dose of Brucella abortus strain 19 vaccine to protect cattle when given early in calfhood.
Groups of heifer calves were vaccinated subcutaneously with the standard dose of strain 19 at the age of 3 to 5 weeks or 5 months. Twelve months after primary vaccination a group of the younger vaccinates were revaccinated with a small dose of strain 19 via the conjunctival sac. The effectiveness of vaccination was assessed by challenge with virulent B. abortus after 5 to 6 months of pregnancy. Animals vaccinated at 3 to 5 weeks, but given no intraconjunctival boost, were not effectively protected, but the group receiving the boost were at least as resistant as those which received the subcutaneous dose at 5 months. The intraconjunctival boost caused only slight and transient serological responses in a few animals.
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Vaccination of pregnant cows with low doses of Brucella abortus strain 19 vaccine.
Two groups, each of 9 Jersey cows, were vaccinated subcutaneously with reduced doses of Brucella abortus strain 19 vaccine (measured by the number of bacteria in the vaccine dose) early in their second pregnancy. Ten weeks later they were challenged, along with a similar group of non-vaccinated cows, by conjunctival instillation of a virulent strain of B. abortus biotype 1. Cows in Group 1 received 1/20th and those in Group 2 received 1/400th the recommended dose of strain 19. Marked reduction in the serological response to vaccination was seen only in Group 2. Four cows in Group 1 excreted strain 19 after parturition, one of them aborted and another calved prematurely with heavy infection of the placenta and foetus with strain 19 in both cases. Resistance to challenge was similar in both vaccinated groups, and higher than previously demonstrated after conventional calfhood vaccination with strain 19. It is concluded that pregnant cows can be effectively vaccinated by the subcutaneous administration of a dose of strain 19 vaccine containing approximately 3 x 10(8) organisms without undue interference with subsequent serological tests or inconvenience resulting from persistence of strain 19 infection.
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Recent developments in vaccination against bovine brucellosis.
Recent research in vaccination against bovine brucellosis has been directed towards reducing the serological response to vaccination and to developing serological tests better able to distinguish vaccinal titres from those resulting from field infection. In the case of strain 19 vaccination, developments such as reducing the dose of vaccine and improving serological tests have so reduced the serological response as to allow adult vaccination to be carried out in combination with eradiction by test and slaughter. B. abortus 45/20 vaccine is being increasingly used as a combined diagnostic aid and protective agent. Progress has been made in identifying antibodies produced in response to this vaccine.
Agglutination Tests↗
The serological diagnosis of bovine brucellosis: an evaluation of the complement fixation, serum agglutination and rose bengal tests.
In a collaborative investigation in which 4 laboratories took part, the Rose Bengal Test (RBT), Serum Agglutination Test (SAT) and 4 different Complement Fixation (CFT) techniques were evaluated in selected cattle for the diagnosis of bovine brucellosis, by comparing the results they gave with the bacteriological examination of a selection of lymph nodes taken from the same animals at slaughter. The RBT correctly classified all but 1 of 79 culture-positive cattle, but was more often positive in culture-negative animals than the other tests. The RBT may be most useful as a screen test. 11% of the culture-positive cattle had SAT titres below 100 iu and almost 4% of them had less than 30 iu. However, the SAT was more effective in cattle vaccinated with the 45/20 vaccine. The CFT, in 1 of 4 techniques used, identified all of the culture-positive cattle at a serum dilution of 1/4 or above and was considered to be far superior to the SAT as a diagnostic test, except perhaps in cattle vaccinated with the 45/20 vaccine.
Agglutination Tests↗
A mechanism for prozone formation in the complement fixation test for bovine brucellosis.
Complement fixation (CF) by bovine IgG1 or IgM antibodies to Brucella abortus was inhibited by specific non-complement-fixing antibodies of the IgG2 subclass. This inhibition may account for the appearance of prozones in CF titrations of some antiserums, and for the occurrence of serums which are positive to the Rose Bengal test, but negative to the CF test.
Agglutination Tests↗
Laboratory techniques in brucellosis.
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Proceedings: Brucellosis as a human health hazard in Australia.
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