Bovine Spongiform Encephalopathy - Epidemiology

Epidemiology

The table to the right summarizes reported cases of BSE and of vCJD by country. (The vCJD column is by county of residence of patient at time of diagnosis and not suspected origin of beef.) BSE is the disease in cattle, while vCJD is the disease in people.

The tests used for detecting BSE vary considerably, as do the regulations in various jurisdictions for when, and which cattle, must be tested. For instance in the EU, the cattle tested are older (30 months or older), while many cattle are slaughtered younger than that. At the opposite end of the scale, Japan tests all cattle at the time of slaughter. Tests are also difficult, as the altered prion protein has very low levels in blood or urine, and no other signal has been found. Newer tests are faster, more sensitive, and cheaper, so future figures possibly may be more comprehensive. Even so, currently the only reliable test is examination of tissues during an autopsy.

It is notable that there are no cases reported in Argentina, Australia, Brazil, New Zealand, Uruguay, and Vanuatu, where cattle are mainly fed outside on grass pasture and, mostly in Australia, grain feeding is done only as a final finishing process before the animals are slaughtered for meat.

As for vCJD in humans, autopsy tests are not always done, so those figures, too, are likely to be too low, but probably by a lesser fraction. In the United Kingdom, anyone with possible vCJD symptoms must be reported to the Creutzfeldt-Jakob Disease Surveillance Unit. In the United States, the CDC has refused to impose a national requirement that physicians and hospitals report cases of the disease. Instead, the agency relies on other methods, including death certificates and urging physicians to send suspicious cases to the National Prion Disease Pathology Surveillance Center (NPDPSC) at Case Western Reserve University in Cleveland, which is funded by the CDC.