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Johne's Disease: Young Cattle Spread Bacteria

26 August 2010

THE NETHERLANDS - Researchers at the GD Animal Health Service, Deventer have discovered that young stock shed more faecal culture positive Mycobacterium avium subsp. paratuberculosis (Map).

Knowing the age at which cattle become faecal culture positive for Map can be used as a proxy parameter for age at onset of faecal shedding, which is an important parameter in the control of Map in cattle herds.

The researchers carried out analysis on asynchronous interval censored data of faecal culture results from samples of 18,979 female Holstein-Freisian cattle.

The results indicate that the distribution of age at onset of faecal shedding in Holstein-Frisian dairy cattle in infected herds is associated with the within-herd prevalence. In higher classes of apparent prevalence, cattle started to shed Map at younger age on average.

In herds with an apparent prevalence <0.05, 0.05–0.1, 0.1–0.2 and ≥0.2, the proportion (95 per cent CI) of cattle with onset of faecal shedding before two years of age was estimated at one per cent (0.5 per cent; two per cent), four per cent (three per cent; five per cent), eight per cent (five per cent; 10 per cent) and 20 per cent (11 per cent; 32 per cent), respectively.

This study indicates that a considerable proportion of young stock are shedding Map, especially in high prevalence herds. Therefore, infectious young stock should be a major concern in the control of paratuberculosis.

Paratuberculosis, is often called Johne's Disease.

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