Abstract
Mycoplasma bovis causes mastitis in dairy cows and is associated with pneumonia and polyarthritis in cattle. The present investigation included a retrospective case–control study to identify potential herd-level risk factors for M. bovis associated disease, and a prospective cohort study to evaluate the course of clinical disease in M. bovis infected dairy cattle herds in Switzerland. Eighteen herds with confirmed M. bovis cases were visited twice within an average interval of 75 d. One control herd with no history of clinical mycoplasmosis, matched for herd size, was randomly selected within a 10 km range for each case herd. Animal health data, production data, information on milking and feeding-management, housing and presence of potential stress- factors were collected. Composite quarter milk samples were aseptically collected from all lactating cows and 5% of all animals within each herd were sampled by nasal swabs. Organ samples of culled diseased cows were collected when logistically possible. All samples were analyzed by real-time polymerase chain reaction (PCR). In case herds, incidence risk of pneumonia, arthritis and clinical mastitis prior to the first visit and incidence rates of clinical mastitis and clinical pneumonia between the two visits was estimated. Logistic regression was used to identify potential herd-level risk factors for M. bovis infection. In case herds, incidence risk of M. bovis mastitis prior to the first visit ranged from 2 to 15%, whereas 2 to 35% of the cows suffered from clinical pneumonia within the 12 months prior to the first herd visit. The incidence rates of mycoplasmal mastitis and clinical pneumonia between the two herd visits were low in case herds (0–0.1 per animal year at risk and 0.1-0.6 per animal year at risk, respectively). In the retrospective-case-control study high mean milk production, appropriate stimulation until milk-let-down, fore-stripping, animal movements (cattle shows and trade), presence of stress-factors, and use of a specific brand of milking equipment, were identified as potential herd-level risk factors. The prospective cohort study revealed a decreased incidence of clinical disease within three months and prolonged colonization of the nasal cavity by M. bovis in young stock.
Highlights
Bovine mycoplasmosis due to Mycoplasma bovis has caused major economic losses in the USA and Canada for several years, inducing mastitis [1,2], respiratory disease [3], and polyarthritis [4]
From April 2010 till October 2011, affected herds were reported. These herds, which had at least one animal with clinical signs of mastitis, pneumonia or arthritis and at least one M. bovis polymerase chain reaction (PCR) or culture positive sample in materials such as milk, broncho-alveolar lavage fluids, nasal swabs, lung or mammary gland-tissue during the last 3 months before study enrollment were included in the study and were defined as case herds
A total of 18 (2.4%; 95%-CI: 1.5-3.8%) milk samples collected in case herds during the first visit were M. bovis PCR positive and were collected from cows suffering from clinical mastitis with the typical symptoms of severe swelling and changes of secretion followed by spreading of the clinical signs to all four quarters
Summary
Bovine mycoplasmosis due to Mycoplasma bovis has caused major economic losses in the USA and Canada for several years, inducing mastitis [1,2], respiratory disease [3], and polyarthritis [4]. Both dairy and beef cattle have been affected [5]. Several authors [16,17] have suggested that mycoplasmas are frequently present in the cattle population, causing disease only if specific conditions are met Such circumstances can occur if animals’ immune response is impaired due to stress such as inadequate feeding, transportation or low environmental temperatures [17,18]. During the last 2 to 3 years, incidental field reports have indicated an increase in number of outbreaks due to M. bovis in Swiss dairy cattle herds, mainly associated with the development of mastitis and pneumonia
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