The prevalence of BJD (Bovine Johne's Disease).

The following is a list of references that gives some detail on the prevalence of BJD (Bovine Johne's Disease) in cattle herds in various countries across the world. Unfortunately, since research into this topic has not been conducted everywhere, data is not available for all countries.

For a thorough discussion of the global prevalence of Johne's Disease, by continent and by country, see the paper "Johne's Disease - The International Perspective".

In the UK, where the prevalance of Johne's disease in cattle was recorded to be 3.5%, an average of 7% of supermarket milk supplies were contaminated with Mycobacterium paratuberculosis DNA. At peak times of the year, up to 25% of supermarket milk supplies were contaminated.

In some parts of the USA, very high prevalance rates of Johne's disease(18%) have been recorded. This is most likely caused by intensive modern farming practices, where higher numbers of cattle are grazed on smaller plots of land. Since infection with paratuberculosis is spread through contact with contaminated faeces (i.e. cowpats), these intensive practices increase the chances of cross contamination between animals in a herd.

Since the milk from an entire herd is likely to be pooled together (in tankers) for transport to pasteurization processing plants, the herd prevalence figure (i.e. the number of herds in a region that contain infected animals) is more likely to indicate the level of contamination of milk.

The statistics.

• U.S.A.The most recent national survey of BJD conducted has uncovered that Bovine Johne's Disease has become an enormous problem for US cattle farmers. The USDA survey Johne's Disease on U.S. Dairy Operations has discovered that 40% of large farms (with more than 200 animals) contain animals infected with BJD, and over 20% of small farms contain infected animals.
  • New England. This survey of cattle herds in New England found that 18% of cattle in that region had bovine paratuberculosis. "The prevalence of paratuberculosis in culled New England cattle."

  • Florida. This survey of Florida cattle was conducted in 1986 and 1987. It found that 17.1% of dairy cattle and 8.6% of beef cattle in that region had bovine paratuberculosis. "Use of an enzyme-linked immunosorbent assay to estimate prevalence of paratuberculosis in cattle of Florida."

  • Wisconsin. This survey, published in 1994, found that 4.79% of dairy cattle in Wisconsin were infected with bovine paratuberculosis, and that 34% of dairy herds contained infected animals. "Herd prevalence and geographic distribution of, and risk factors for, bovine paratuberculosis in Wisconsin."

  • California. This survey of California cattle, conducted in 1988 and 1989, found that 8% of dairy and beef cattle had bovine paratuberculosis. "Mass screening of cattle sera against 14 infectious disease agents, using an ELISA system for monitoring health in livestock."

• Canada. This survey of cattle in Ontario, conducted between 1986 and 1989, found that 6.1% of dairy cattle in that region had bovine paratuberculosis. "An epidemiological study of paratuberculosis in dairy cattle in Ontario: study design and prevalence estimates."

• England. This survey of cattle in southwest England found that 3.5% of them were infected with Mycobacterium paratuberculosis. "An abattoir-based study of the prevalence of subclinical Johne's disease in adult cattle in south west England."

• Switzerland. This survey of cattle in the Plateau de Diesse region found that 5.99% of cattle in that region were infected with bovine paratuberculosis. "[The prevalence of paratuberculosis in the Plateau de Diesse region]".

• Belgium. This survey of Belgian cattle found that 12% of them had a positive immune response to Mycobacterium paratuberculosis. "Development of species-specific enzyme-linked immunosorbent assay for diagnosis of Johne's disease in cattle."

• Australia. This first study only discusses the testing of herds for bovine paratuberculosis. "Aggregate testing for the evaluation of Johne's disease herd status." This second study discusses cost-benefit analysis of testing a herd for bovine paratuberculosis infection. "Determination of the optimal cutoff value for a serological assay: an example using the Johne's Absorbed EIA."

• Netherlands. Unfortunately this paper restricts itself to discussing the progress of two herds infected with BJD. "Incidence of paratuberculosis after vaccination against M. paratuberculosis in two infected dairy herds."

Source: http://archive.crohn.ie/johne.htm
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