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MAP: helping farmers to make informed decisions
  1. Alasdair J. C. Cook, BVM&S, MSc, DipECVPH, CertPM, MRCVS
  1. School of Veterinary Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford
    GU2 7TE, UK
  1. E-mail: alasdair.j.cook{at}

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Mycobacterium avium subspecies paratuberculosis (MAP) may cause chronic infections in a range of host species, especially ruminants (Collins 2011). Infection occurs early in life and may initially progress to cause a loss of productivity without obvious clinical signs. Later, a chronic enterocolitis may develop and manifest as the progressive weight loss (Fig 1) and diarrhoea typical of severe Johne's disease (Begg and Whittington 2008). This disease is of particular concern to dairy farmers due to the welfare and production losses associated with the condition (Stott and others 2005, Kudahl and Nielsen 2009). In addition, there remains contention over the possible role of MAP in the aetiology of Crohn's disease, a debilitating inflammatory bowel disease (Pierce 2010). Although there is insufficient evidence to reach a definitive conclusion (Over and others 2011), the Food Standards Agency is taking a precautionary view with respect to the risk to human health. If there was incontrovertible evidence that MAP causes Crohn's disease this would have important implications for control.

FIG 1:

A cow with chronic Johne's disease

Photograph: Michael T. Collins

Laboratory confirmation of MAP infection relies on serology to detect antibodies or detection of MAP through culture or newer PCR-based approaches. However, all of these have limitations, given …

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