Researchers have found that over the years some forms of contagious mastitis have emerged from rarity to become more common, like Mycoplasma sp., while others, like Streptococcus agalactiae, have been largely eradicated.
The idea that mycoplasma mastitis is re-emerging is reflected in reports from Canada, Britain and Belgium. In Quebec, Canada, David Francoz, adjoint professor at the University of Montreal, studied the presence of contagious mastitis in dairy herds. There he found mycoplasma was present in 2.6% of herds. Before the survey was presented, he and his colleagues said that the disease had been previously unreported in that region.
The same happened in Belgium where independent dairy consultant Pieter Passchyn and his colleagues indicated that mycoplasma mastitis had increased from zero in 2007 to 1.5% in 2008.
Similarly, in England, Robin Nicholas and his team found that mycoplasma has become a significant problem, where they say that a large number of cases go undiagnosed.
The first case of mycoplasma mastitis
The first case of mycoplasma mastitis occurred in the state of Connecticut in the USA in 1961. At the time, in a herd of 95 cows, 25 presented mild or subclinical mastitis. The cows were treated with an intramammary suspension of procaine penicillin G. Within a day, all treated mammary quarters were clinical, hard and swollen with little secretion. On top of that, in the next 7-10 days new mammary quarters presented as clinical. Three weeks later, five new cases emerged, and more than half of the cows affected were sent for slaughter. Initially, the causative agent was deemed idiopathic and could not be cultured using standard mastitis diagnostic techniques. This led to the opening up of new investigations into mycoplasma mastitis research.
Where are we today?
A summary of some surveys estimating the prevalence of mycoplasma mastitis over the last 10 years can be found in Table 1 online in the June 2015 issue of M2-magazine. According to most of the surveys, mycoplasma mastitis affects less than 5% of herds in various countries. It should be noted, too, that there is a wide range in the percentage of mycoplasma mastitis-affected herds. While it appears to be a significant problem in some regions, it has been fairly minor in others. Looking at the aforementioned Table 1, one can see that prevalence has ranged from 1% to 48.75%.
Since that first outbreak in 1961, the nomenclature around mycoplasma mastitis has undergone significant change as well. At first it was thought that the agent causing mycoplasma mastitis was similar in nature to the contagious M. agalactiae in goats and sheep. Later, it became clear that the agent causing mastitis in cattle had a different phenotype and genotype. As a result, a change in name was suggested; eventually, the species became known as Mycoplasma bovis.
Mycoplasma bovis appears to be the most virulent species to cattle. It is now know that M. bovis also causes several other diseases in cattle, including arthritis, pneumonia, vaginitis and otitis.
This is part one of three focused on mycoplasma mastitis. The next part, a piece looking at transmission of the disease, will appear in two weeks’ time. Following that, a third part will cover prevention and control.
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