Botulism in the European Union

Introduction

Botulinum toxin was first described as a potent neurotoxin in the late eighteenth century. Currently three main distinct clinical and epidemiological botulism syndromes are described - foodborne botulism, which results from the ingestion of food contaminated with performed toxin; infant botulism, due to the endogenious formation of toxin by germinating spores of Clostridium botulinum, in the intestine of the infant; and wound botulism, caused by organisms that multiply and produce toxin in wounds contaminated by soil. Seven types of C.botulinum (A to G), distinguishable by the antigenic characteristics of the toxin they produce, are described. Types A, B, E and rarely F cause disease in humans (1).

Changes in dietary habits, improvements in food preservation techniques and in industrial food processing, and awareness of the risk of botulism have made botulism a rare disease.

Nevertheless, following several outbreaks of botulism this year in various European Union (EU) countries (cases of botulism associated with the consumption of mushrooms and vegetable soup in Italy, shrimps in France, fermented fish in Norway, and cases in the United Kingdom), Eurosurveillance has taken the opportunity of surveying the current epidemiology of botulism and its surveillance in the countries of the EU.

Discussion

The epidemiological pattern of botulism in European countries seems to have been relatively stable during the last decade. Surveillance is usually based on mandatory notification. Under-notification, although not estimated, may be important in some countries.

Most affected countries

Data collected through this survey suggest that Italy, France, Spain and Germany are the European Union countries most affected by botulism, although at differing levels. Outbreaks of foodborne botulism are the commonest form of botulism in all these countries. In France and Italy, type B toxin seems to predominate. In France between 1993 and 1996, all outbreaks were due to toxin type B. Although no outbreak due to toxin E was notified in France since 1987 (2), two such outbreaks were reported recently, in 1997 and 1998. The case in 1998 was suspected to be due to raw shrimps. All cases of botulism type E, as notified in Germany and France, were linked to consumption of seafoods.

Botulism type-E associated with fisheries products from the Baltic sea area is a matter of concern. A recent Finnish study reported 3 to 10% positive identification of C.botulinum type E gene by polymerase chain reaction (PCR) in various preparation of these products and called for a review of their processing and marketing standards (3).

Otherwise, although C.botulinum is the most commonly found specie linked with botulism, Italy reported cases of botulism caused by C.butyricum.The species of clostridium, first described in an outbreak of foodborne botulism in China in 1994 (4), has more recently been described in cases of infant and adult botulism in Italy (5).

There is no common pattern of implicated foods in countries where botulism occurs frequently, but rather a large range of products. Outbreaks linked to manufactured products are rarer than outbreaks linked to home-made preparations, but should not be forgotten. Infant botulism is relatively rare in Europe, with seven cases reported in Germany, Italy, and Spain in 1997 and 1997, most linked to consumption of honey.

Wound botulism remains very rare in Europe in contrast to the United States, where it is mainly observed among injecting drug users. In contrast, in Italy, the only country that reported such cases during the last decade, such form of botulism has occurred among some categories of workers.

A recent case occurred in an injecting drug user in Norway.

Conclusion

Although quite rare in the European Union, botulism remains a disease with serious clinical features that can be prevented by adequate preparation of food products. Whether these foods are manufactured or home-made, caution must be applied regarding the preservation process. Control of temperature, salt concentration, and pH is crucial to prevent the sporulation of clostridium.

Notification systems are not always exhaustive and, in some countries, botulism has been included only very recently on the list of notifiable diseases. Epidemiological features of botulism may differ between countries because of differing dietary habits. Furthermore, the risk associated with imported products still remains, even if it is rare. A recent example of Italian vegetable soup contaminated with C.botulinum and marketed in several European countries (6) shows the importance of correct handling in industrial preservation processes, and of the implementation of control measures through to a rapid alert system between countries.

References

1. Benenson AS. Control of Communicable Diseases Manual. Washington DC: American Public Health Association, 1995:66-71
2. Solomon J, Delarocque-Astagneau E, Popoff M, Carlier JP. Le botulisme en France en 1997. Bulletin Epidémiologique Hebdomadaire 1998; (44): 201
3. Hyytïa E, Hielm S, Korkeala H. Prevalence of Clostridium botulinum type E in Finnish fish and fishery products. Epidemiol Infect 1998; 120: 245-50
4. Xiaoqi M, Tadahiro K, Kaiyong Z, Xin K, Xingmin W, Cunnu L, et al. Characterisation of a neurotoxigenic Clostridium butyric strain isolated from the food implicated in an outbreak of food-borne type E botulism. J Cline Microbial 1997; 35: 2160-2
5. Aurally P, Fence L, Pasolini B, Gianfranceschi M, McCroskey L, Hatheway C. Two cases of type E infant botulism caused by neurotoxigenic Clostridium butyricum in Italy. J Infect Dis 1986; 154: 207-11
6. Bruno S. Botulism caused by Italian bottled vegetables. Lancet 1998; 352: 884