While this article was in press, we have learned of the sad death of Professor Artur Galazka on the 11 May 1999 in Warsaw (Poland). He has been a valued and regular collaborator to Eurosurveillance. We will miss him greatly.

Human foodborne botulism, in contrast to the other two forms of botulism (wound and infant botulism), is an intoxication that results when preformed botulinum toxin is ingested. Sporadic cases and family and general outbreaks occur when food products are prepared or preserved improperly and stored under anaerobic conditions that permit germination, multiplication, and toxin formation.

Public awareness of the risk of botulism, changing dietary habits, improvements in food preservation techniques, and the growth of industrial food processing have made botulism rare in Europe (1). In Poland, however, foodborne botulism remains a serious epidemiological problem due to the practice in some parts of Poland of home-preserving meat and, to a lesser extent, vegetable and fruit products. In Poland, people often use a system of weck jars (weckglas) to hermetically seal cooked food at home. Weck jars are glass jars with rubber seals and a device used to create a vacuum. Inadequate heating during the preparation of food and failure to follow detailed instructions during ‘wecking’ leave spores viable and permit toxin formation.

Since 1952 botulism has been notifiable among other cases of ‘food poisoning’ (2). In 1963 it became a statutory notifiable disease. There is no standard case definition, and patients with compatible symptoms or signs are registered. Obligatory epidemiological investigations are performed by the Sanitary-Epidemiological Stations (of which there are 49, one in each administrative region). The results of these investigations are collected and analysed at the National Institute of Hygiene in Warsaw. At the same institute, the National Centre for Sporulating Anaerobes performs diagnostic and reference tests to determine the type of botulinum toxin and offers training in diagnosis of anaerobic bacteria.

The incidence of botulism was high in the 1960s and 1970s and during the period of social change in the 1980s when the country suffered from food shortage. The numbers of cases registered from 1960 to 1990 ranged from 201 in 1964 to 738 in 1982, equivalent to attack rates between 0.6 to 2.0 per 100 000 (table 1) .

Year

No. of cases

Attack rate per 100 000

No. of deaths

Case-fatality ratio (%)

1961

204

0.7

-

-

1962

404

1.3

-

-

1963

295

0.9

-

-

1964

201

0.6

-

-

1965

252

0.8

-

-

1966

428

1.3

-

-

1967

423

1.3

-

-

1968

491

1.5

-

-

1969

389

1.2

-

-

1970

401

1.2

6

1.5

1971

439

1.3

11

2.5

1972

335

1.0

5

1.5

1973

247

0.7

5

2.0

1974

333

1.0

4

1.2

1975

271

0.8

6

2.2

1976

307

0.9

5

1.6

1977

297

0.9

3

1.0

1978

392

1.1

14

3.6

1979

383

1.1

4

1.0

1980

269

0.7

1

0.4

1981

608

1.7

11

1.8

1982

738

2.0

15

2.0

1983

645

1.8

11

1.7

1984

541

1.5

13

2.4

1985

551

1.5

10

1.8

1986

416

1.1

9

2.2

1987

283

0.8

14

4.9

1988

356

0.9

4

1.1

1989

315

0.8

3

1.0

1990

328

0.9

5

1.5

1991

173

0.5

?

?

1992

165

0.4

2

1.2

1993

143

0.4

2

1.4

1994

116

0.3

3

2.6

1995

118

0.3

1

0.8

1996

107

0.3

4

3.7

1997

81

0.2

0

0

1998

93

0.2

4

4.3

From 1988 to 1998, nearly 2000 cases of botulism have been registered in Poland, considerably more than in Italy (412), Germany (177), and Spain (92) (1). Since 1991 the numbers of cases have started to decline below 200 each year, probably due to improvement in the supply of food (attack rate 0.2/100 000) (table 1).

Between zero and 15 deaths occurred each year, and rates were highest in the early 1980s. In the last decade deaths of sporadic cases were registered. The case fatality rate reached 4.9% (in 1987) and has subsequently varied between 1% and 4% (table 1).

Botulism in Poland mainly affects young and middle aged people (20 to 59 years), who account for 74% of all cases (figure 1). Less than 10% of botulism cases are children under 15 years of age and people over 60 years. From 1980 to 1997, the incidence in males (0.23 - 2.3/100 000, median 0.86) was higher than in females (0.4 - 1.8/100 000, median 0.43).

The reported geographical distribution of disease varies markedly. In the 1970s and 1980s the highest rates were registered in rural areas of the northern and western provinces of Poland. The incidence exceeded 3/100 000 and in some years reached 12/100 000 (Bydgoszcz Region in 1982). In the 1990s this pattern become less visible (figure 2). In the southern and central regions the incidence from botulism was lower than 3/100 000. Between 1971 and 1997, differences between provinces waned and an increasing number of provinces registered no cases (18.4% in 1971 – 9 provinces - and 53% in 1997 – 24 provinces). The number of cases usually increases in May to August and in December. This is probably associated with increased slaughtering of pigs in private farms and more intensive preparation of home-made wecked products.

Most cases of botulism were registered as single, sporadic cases (74% in from 1980 to 1984 and 79% from 1993 to 1997) or as small, two-person outbreaks (16% from 1980 to 1984 and from 1993 to 1997) (table 2). Outbreaks of three cases accounted for 6% of all outbreaks from 1980 to 1984 and 3% from 1993 to 1997. The rarity of large outbreaks is balanced by the number of cases they make up; larger outbreaks - including four, five, six, or seven cases - were rare but constituted up to 10% of all cases. The epidemiological patterns of outbreaks were similar in two periods analysed (table 2) although four times as many outbreaks were registered in the second period.

Number of outbreaks (%)
1980/84

Number of outbreaks (%)
1993/97

1 case outbreaks

1425 (73.6)

341 (78.9)

2 cases  outbreaks

310 (16)

67 (15.5)

3 cases  outbreaks

117 (6)

13 (3)

4 cases  outbreaks

41 (2.1)

6 (1.4)

5 cases  outbreaks

22 (1.1)

4 (0.9)

> 5 cases outbreaks

20 (1)

1 (0.2)

Total

1935 (100)

432 (100)

Between 90% and 100% of cases reported are admitted to hospital. In 1997, 15% of cases were admitted to hospital for up to one week, 39% to between one and two weeks, 21% between two and three weeks, 11% between three and four weeks, and 14% for over four weeks. The course of the disease was assessed as moderate in 47%, severe in 20%, and mild in 16%. There are reports of secondary onset of botulism, occurring between one and ten years after the first episode (3,4). They suggest that people do not change their dietary habits, and that there is no strong immunity following disease. No cases of wound and infant botulism have been recorded in Poland.

Most cases of botulism (81%) were associated with eating meat (mainly pork) products; while fish (13%) and vegetables (6%) were rare vehicles (table 3).

Meat

Fish

Vegetables

Cans

Wecks

Sausages

Ham

Pasty

Other

Wecks   or cans

Pickled

Wecks or cans

Total

-

124

10

38

-

11

3

11

13

210

22

-

17

-

5

4

23

-

4

75

22

124

27

38

5

15

26

11

17

285

Seventy-four per cent of the 285 cases registered in 1990 were attributed to the consumption of home-processed food, mostly prepared from meat and conserved in weck jars. There is no special Polish home-made food linked with botulisum, in contrast to the ‘rakfisk’ (half-fermented fish eaten at Christmas in Norway) (6) or ‘isushi’ (pickled relish made of raw fish, rice and diced vegetable) (7). The foodstuffs implicated have been prepared in wecks, pickled, or smoked and often allowed to stand for a time (from several weeks to several months) and eaten without cooking. The commonest foods implicated in cases of botulism were wecked pork products and sausages, ham, headcheese (brawn), liver sausage, and bacon (3,4,5). The most important risk factors for botulism in preparing home-processed food appear to be a heavy initial contamination by the spores, insufficient heating (too short treatment with too low temperature), improper conditions and temperature of storing, and the use of food without final cooking (8).

Home wecking, being a relatively ill controlled process, is far more likely than industrial canning to result in poisoned food. Nevertheless, commercially prepared food was implicated as the vehicle in 26% of all cases; most often canned meat and fish. Control measures, including hazard analysis critical control points are being introduced in the food production industry, and further cooperation with the veterinarian authorities is being established.

Most of the outbreaks of botulism in Poland have been caused by toxin type B (table 4). In recent years the proportion of cases caused by type E has increased.

Year

Total No. of cases

No. of cases  tested for toxin

No. of cases with positive test (100%)

Type of toxin found (in %)

A

B

E

F

Mixed types mixted

Type not determined

1971/74

1354

?

327

3.1

93.2

3.1

0.6

-

-

1980

269

211

147

3.4

85.7

0.7

-

-

10.2

1985

551

428

274

1.8

88.7

2.6

-

-

6.9

1990

328

271

158

9.5

79.1

2.5

-

-

8.9

1995

118

105

68

2.9

82.4

2.9

-

4.4

7.4

1997

93

93

50

2.0

76.0

8.0

-

2.0

12.0

Public education, the most effective method of preventing botulism, was unsatisfactory until 1990 (9). Simple advice on proper methods of home canning/wecking (for example, using a pressure cooker and acidifying foods with vinegar, as C. botulinum does not grow in pH £ 4.6, or thoroughly heating all home-canned foods by boiling or baking before they are served) could prevent many cases of botulism. Public education is being intensified. In the mid-1970s, people at high risk (laboratory staff working with botulinum toxin) were successfully immunised with ABE botulinum toxoid; in general, the response to botulinum toxoid was similar to the response to tetanus toxoid (10).

Surveillance of botulism in Poland has been used to assess the importance of the problem, to monitor trends over time and by place, and to identify the commonest food vehicles and risk factors. Although all cases are probably not reported (minor cases not admitted to hospital are probably missing), this surveillance system is an effective tool to guide and target public health action.

1. Therre H. Botulism in the European Union, Eurosurveillance 1999; 4: 2-7.

2. Przybylska A. Registration of the foodborne and waterborne diseases in Poland in 1919 - 1997. Przeglad Epidemiologiczny 1998; 52: 263-7.

3. Anusz Z. Botulism - 1982. Przeglad Epidemiologiczny 1984; 38: 175-82.

4. Anusz Z. Botulism - 1985. Przeglad Epidemiologiczny 1987; 41: 78-84.

5. Anusz Z. Botulism - 1990. Przeglad Epidemiologiczny 1992; 46: 93- 7.

6. Kuusi M, Hasseltvedt V, Aavitsland P. Botulism in Norway. Eurosurveillance 1999; 4: 11-2.

7. Kanzawa K. Foods as vehicles in botulism in Japan. Jap J Med Sci Biol 1963; 16: 303-13.

8. Przybylska A. Botulism in 1995. Przeglad Epidemiologiczny 1997; 51: 111-89

9. Anusz Z. Botulisms. Przeglad Epidemiologiczny 1981; 35: 111-7.

10. Galazka A, Rymkiewicz D, Aleksandrowicz J. Botulinum antitoxins and bacterial IgM and IgG antibodies in sera of persons immunized with botulinum polytoxoid combined with cholera vaccine. I. Response to botulinum toxoid Arch Immunol Ther Exper 1976; 24: 631-9.