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Objective: An epidemiological study was undertaken at a Hunter Valley dairy with persistent Salmonella Typhimurium infection. The aim of the study was to identify cattle currently or previously infected with Salmonella, possible sources of the organism, patterns of spread, and husbandry practices that could be improved., Methodology: Faecal samples, feed, water and environmental samples were cultured for Salmonella and blood samples were tested for antibodies against Salmonella (Dublin and Typhimurium). A questionnaire was designed to identify possible risk factors associated with Salmonella excretion., Results: S Typhimurium was apparently introduced from an old to a new dairy through manure spread as fertiliser. Salmonella apparently persisted in the effluent pond, and the following year clinical cases occurred after pasture, irrigated with water from the pond, was grazed by dry cows, and adult cattle became clinically ill with salmonellosis. The disease spread to other cows and calves. Poor design of calf pens assisted spread of Salmonella from sick to healthy calves. In addition, there was suspected transmission to the dairy farmer's 9-month-old daughter. Salmonellosis on a farm is a potential zoonotic risk to farm workers and their families. There is also the risk that cull cows may carry Salmonella to the abattoir and subsequently into the human food chain. Methods of waste management, and the design of calf pens, were identified as major risk factors that could be improved to minimise the spread of salmonellosis on this property.

A comprehensive genetic analysis of 60 Mycoplasma sp. bovine group 7 isolates from different geographic origins and epidemiological settings is presented. Twenty-four isolates were recovered from the joints of calves during sporadic episodes of polyarthritis in geographically distinct regions of Queensland and New South Wales, Australia, including two clones of the type strain PG5O. A further three Australian isolates were also recovered from the tympanic bulla, retropharyngeal lymph node and the lung and another three isolates had unconfirmed histories. Six isolates originated from Germany, Portugal, Nigeria, and France. Twenty-four epidemiologically related isolates of Mycoplasma sp. bovine group 7 were recovered from multiple tissue sites and body fluids of infected calves with polyarthritis, mastitic milk, and from the stomach contents, lung and liver from aborted foetuses in three large, centrally managed dairy herds in New South Wales, Australia. Restriction endonuclease analysis (REA) of genomic DNA differentiated 29 Cfol profiles among these 60 isolates and grouped all 24 epidemiologically related isolates in a defined pattern showing a clonal origin. Three isolates of this clonal cluster were recovered from mastitic milk and the synovial exudate of clinically-affected calves and appeared sporadically for periods up to 18 months after the initial outbreak of polyarthritis indicating a persistent, close association of the organism with cattle in these herds. The Cfol profile representative of the clonal cluster was distinguishable from profiles of isolates recovered from multiple, unrelated cases of polyarthritis in Queensland and New South Wales and from other countries. All 24 isolates from the clonal cluster possessed a plasmid (pBG7AU) with a molecular size of 1022 bp. DNA sequence analysis of pBG7AU identified two open reading frames sharing 81 and 99% DNA sequence similarity with hypothetical replication control proteins A and B respectively, previously described in plasmid pADB201 isolated from M. mycoides subspecies mycoides. Other isolates of bovine group 7, epidemiologically unrelated to the clonal cluster, including two clones of the type strain PG5O, possessed a similar-sized plasmid. These data confirm that Mycoplasma sp. bovine group 7 is capable of migrating to, and multiplying within, different tissue sites within a single animal and among different animals within a herd.

Objective: To report an outbreak of mastitis, polyarthritis and abortion caused by Mycoplasma sp bovine group 7 in three large, centrally-managed dairies and to review the relevant literature., Design: Epidemiological, clinical and laboratory data were analysed, collated and reported. Multidisciplinary procedures were employed. These included clinical assessment and comprehensive laboratory investigations of affected calves, aborted foetuses and milk samples. Mycoplasma cultures and genetic analyses of isolates were undertaken to identify the aetiological agent., Results: About 30% of 240 calves usually kept in a calf rearing facility developed severe polyarthritis as a result of Mycoplasma sp bovine group 7 infection between 2 and 3 weeks of age. Multiple abortions occurred on these farms. Mycoplasma sp bovine group 7 was recovered from the fibrinopurulent synovial exudates of four 14-day-old calves, from the stomach contents and lungs of two aborted foetuses, from 14 of 21 bulk milk and four of 10 mastitic quarters. Three bulk colostrum samples cultured during the outbreak were negative for mycoplasma., Conclusion: Mycoplasma sp bovine group 7 caused significant economic losses as a result of polyarthritis, abortion and mastitis. The disease probably originated from udder infections with spread being facilitated by the decreased use of tetracycline in the treatment of mastitis. Neonatal calves were most likely infected by the consumption of milk contaminated with the organism. Abortions presumably resulted from mycoplasmaemia. This appears to be the first report in Australia of bovine abortion resulting from Mycoplasma sp infection.

An enzyme-linked immunosorbent assay (ELISA) measuring IgA antibodies in the vaginal mucus was used to diagnose bovine venereal campylobacteriosis in 241 herds with infertility and abortions. The presence of the disease was confirmed on 84 farms (34.8%) and it was suspected on a further 27 farms (11.2%). The specificity of the ELISA was found to be 98.5% but in the absence of a reliable comparative test sensitivity can not be estimated. Vaccination against campylobacteriosis will not interfere with the IgA ELISA because only IgG is present in the vaginal mucus of vaccinates. Because of the possibility of false reactions caused by antibody fluctuations in individual cattle, the ELISA is best used as a herd test. It appears that at present the vaginal mucus IgA ELISA is the test of choice for the diagnosis of bovine venereal campylobacteriosis.

An enzyme-linked immunosorbent assay (ELISA) was developed to detect antigen-specific secretory IgA antibody in bovine vaginal mucus after abortion due to Campylobacter fetus subsp venerealis. Abortions were diagnosed by isolating the organism from 8 foetuses and/or foetal membranes and by histopathology. Vaginal mucus was collected from 7 cows shortly after abortion. All showed a high level of IgA antibody in their vaginal mucus when they were compared with an uninfected control group. The new ELISA is simple and practical and provides a useful tool for diagnosis of bovine venereal campylobacteriosis.