Medical information  
 
 Terms Glossary
 First Aid
 Diet Information
 Preventive Medicine
 Immunization Schedules
 Biological Warfare Effects & Treatment
 Men's health
 Infertility
 Atlas of skin diseases
 Drug encyclopedia
 Atlas of human anatomy
 Alternative medicine
 Baby's developmental milestones
 Medical laboratory tests
 Smoking and health effect
 Advice for travelers
 Hearth attack: risk chart
 Diabetes: risk chart
 Cancer: risk chart
 Alcoholism and treatment
 Topic of the Week
 Medical Topic
 Latest News
 News Archive
 
  » Advice for travelers  »  Bovine Spongiform Encephalopathy and New Variant Creutzfeldt-Jakob Disease

Description

Since 1996, evidence has been increasing for a causal relationship between ongoing outbreaks in Europe of a disease in cattle called bovine spongiform encephalopathy (BSE, or "mad cow disease") and a disease in humans called new variant Cruetzfeldt-Jakob disease (nvCJD). Both disorders are invariably fatal brain diseases with unusually long incubation periods measured in years, and are caused by an unconventional transmissible agent (a prion). Although there is strong evidence that the agent responsible for these human cases was the same agent responsible for the BSE outbreaks in cattle, the specific foods that might be associated with the transmission of the agent from cattle to humans are unknown. However, bioassays have identified the presence of the BSE agent in the brain, spinal cord, retina, dorsal root ganglia (nervous tissue located near the backbone), distal ileum, and bone marrow of cattle experimentally infected with this agent by the oral route.

In addition to cattle, sheep are susceptible to experimental infection with the BSE agent by the oral route. Thus, in countries where flocks of sheep and goats might have been exposed to the BSE agent through contaminated feed, a theoretical risk exists that these animals might have developed infections caused by the BSE agent and that these infections are being maintained in the flocks, even in the absence of continued exposure to contaminated feed (for example, through maternal transmission). In December 1999, the World Health Organization published a report encouraging countries to conduct risk assessments related to BSE in populations of sheep and goats. In August 2000, survey data of sheep farms in the United Kingdom were reported to have shown no rise in BSE-like illnesses in sheep that could be related to the BSE outbreaks in cattle. Currently, cattle remain the only known food animal species with disease caused by the BSE agent.

Occurrence

From 1986 through August 2000, >99% of the cases of BSE reported were from the United Kingdom, but endemic cases of BSE were also reported in other European countries, including Belgium, Denmark, France, Liechtenstein, Luxembourg, Netherlands, Portugal, Ireland, and Switzerland. From 1995 through early August 2000, 79 human cases of nvCJD were reported in the United Kingdom, 3 in France, and 1 in Ireland. During that period, the reported rate of occurrence of these new cases increased. Based on data available in mid-2000, the proportion of the total number of BSE cases in Europe reported outside the United Kingdom rose to 6.7% in 1998 and to >10% in 1999, primarily reflecting the declining large outbreak of BSE in the United Kingdom and the sharp rise in the number of reported cases in Portugal. In July 2000, the European Union Scientific Steering Committee (SSC) on the geographic risk of BSE adopted a final opinion on the risk of BSE in the cattle populations of 23 different countries. The United Kingdom and Portugal were the only ones classified as countries where BSE was confirmed in domestic cattle at a higher level (over 100 cases per 1 million adult cattle in the 12-month period ended June 15, 2000). Despite the absence of reported endemic cases of BSE in Germany, Italy, and Spain, the SSC oncluded that it was likely that cattle were infected in those three countries and classified their geographic risk of BSE as similar to that of the countries where BSE had been confirmed (but at a level below 100 cases per 1 million adult cattle). Because no data were available from Greece, the SSC reported that it was prudent to assume that the geographic BSE risk there was at a "high level." The reports of the final opinion of the SSC and its BSE risk assessments of individual countries are available on the European Union Commission on Food Safety and Animal Welfare Internet website, http://europa.eu.int/comm/food/index_en.php (search for "BSE-risk assessment"). In addition, the numbers of reported cases, by country, are available on the Internet website of the Office International des Epizooties, at http://www.oie.int/eng/info/en_esb.htm These numbers should be interpreted with caution because of differences in the intensity of surveillance over time and by country. Information is being generated rapidly on BSE issues. Updated sources should be consulted.

Risk to Travelers

The current risk of acquiring nvCJD from eating beef (muscle meat) and beef products produced from cattle in Europe cannot be precisely determined, and this risk in specific countries might not reflect the fact that cattle products from one country might be distributed and consumed in others. Nevertheless, in the United Kingdom, this current risk appears to be extremely small, perhaps about 1 case per 10 billion servings. In the other countries of Europe, this current risk, if it exists at all, would not likely be any higher than that in the United Kingdom, except possibly in Portugal. In the 12-month period ending June 15, 2000, Portugal had about half the reported incidence of BSE cases per 1 million adult cattle as that reported in the United Kingdom; however, Portugal has less experience with implementing the BSE-related public health control measures.

Preventive Measures

Public health control measures, such as BSE surveillance, the culling of sick animals, or banning specified risk materials (SRMs), or a combination of these, have been instituted in Europe to prevent potentially BSE-infected tissues from entering the human food chain. The most stringent of these control measures have been applied in the United Kingdom and appear to have been highly effective. In June 2000, the European Union Commission on Food Safety and Animal Welfare adopted a decision requiring all member states to remove SRMs from animal feed and human food chains as of October 1, 2000; such bans had already been instituted in most member states.

To reduce the possible current risk of acquiring nvCJD from food, travelers to Europe should be advised to consider either (1) avoiding beef and beef products altogether or (2) selecting beef or beef products, such as solid pieces of muscle meat (versus brains or beef products such as burgers and sausages), that might have a reduced opportunity for contamination with tissues that might harbor the BSE agent. Milk and milk products from cows are not believed to pose any risk for transmitting the BSE agent.