The Topic of This Month Vol. 31, No. 1 (No. 359)
The Statistics of Food poisoning: Till 1999, Salmonella and Vibrio parahaemolyticus were main causes of the food poisoning, and food poisoning due to Campylobacter was much less. However, since 2000, the incidence of food poisoning caused by Salmonella and V. parahaemolyticus greatly decreased, but that caused by Campylobacter remained unchanged (Table 1).
In the statistics of food poisoning, single-case incidents have occupied significant portion of Campylobacter food poisoning since 1997, which was due to the fact that some municipalities started to report single-case food poisoning cases as incidents (see p. 14 of this issue). Recently, however, incidents involving two or more cases are increasing year by year (see p. 4 of this issue).
The number of patients per year exceeded 2,000 in 2002 and was as high as 3,439 in 2005. Campylobacter and Salmonella are the agents next to norovirus in causing large number of food poisoning patients (Table 1).
Isolation of Campylobacter : PHI/HCs have reported annually 1,100-1,200 isolations of Campylobacter since 2003 (Table 2). Campylobacter jejuni occupied 90% of the isolates and C. coli only few percentages. Imported cases were rare. Monthly reports of Campylobacter isolation showed peaks during May-July, similarly as before 2005 (Fig. 1).
In 2006-2009, PHI/HCs reported total 323 Campylobacter food poisoning outbreaks (Table 3). The peak of outbreak was from May to June preceding the peak in summer of food poisoning caused by Salmonella and V. parahaemolyticus . It should be noted that Campylobacter food poisoning incidents are not rare even in winter. There was only one outbreak involving more than 100 cases during 2006-2009 (see p. 10 of this issue), much less than in years before 2005. Outbreaks involving 50-99 cases were 8 (see p. 7, 9&13 of this issue and IASR 28: 115-116, 2007), those involving 10-49 cases were 103, and those involving 2-9 cases were 125 (Table 3). Among incidents whose potential responsible food was identified the commonest cause was meat (Table 3), mostly chicken and its internal organs. There were incidents caused by consumption of raw beef liver or other animal internal organs (IASR 27: 266, 2006).
From 75% of chicken meat and 75% of other meat examined, either C. jejuni or C. coli was isolated by PHI/HCs during 2006-2009 (Table 4).
Cases of hospital admission: Among 310 Campylobacter enteritis patients admitted to the infectious disease hospitals in 2006-2008, 25% were 0-9 year old, 23% 10-19 year old, and 27% 20-29 year old (Table 5). Patients older than 30 years were few though there was a slight increase among those older than 60 (11% in contrast to 5% in 2003-2005). Of 20-39 year old cases, 23% acquired infection abroad. As for gender of the patients, there were more males than females.
Serotypes of the isolates: The Campylobacter Reference Center is conducting serotyping of C. jejuni according to the Lior system. During 2005-2008, 2,504 strains of C. jejuni derived from sporadic diarrhea cases were subjected to serotyping. The most frequent serotype was LIO4 (524 strains) followed by LIO10 (122 strains) (see p. 15 of this issue).
Drug susceptibility: Among 2,366 C. jejuni strains obtained from sporadic cases and tested by Reference Center in 2005-2008, strains resistant to erythromycin (EM), the first choice antibiotic, were few (0.7%), though 35% were tetracycline (TC)-resistant and 33% fluoroquinolone (FQ)-resistant. Among 75 strains of C. coli , 21% were EM-resistant, 75% TC-resistant, and 63% FQ-resistant (see p. 15 of this issue).
Campylobacter is isolated also from livestock, C. jejuni mainly from cattle and chicken, and C. coli mainly from pigs. EM-resistance has been found among C. coli isolates though not among C. jejuni so far (see p. 17 of this issue).
Problems associated with Campylobacter food poisoning and preventive measures required: In many cases, Campylobacter enteritis is caused by ingestion of raw or undercooked meat that is contaminated by the bacteria (see p. 7, 10, 11&13 of this issue). The Campylobacter survey of the meat revealed its high prevalence in the marketed chicken meat and contamination of inner parts of liver of healthy beef cattle (see p. 4 of this issue).
In many incidents of food poisoning caused by Campylobacter , responsible food(s) cannot be identified. For many of the incidents in restaurants, the commonest place of the incidents, the investigation of responsible food(s) is impossible, as most of them do not preserve the samples of served food. Investigation of food poisoning in families is similarly difficult. In addition, there are other problems. Firstly, as few as some hundreds to some thousands Campylobacter bacteria can cause food poisoning, to identify the responsible foods, very low level of bacterial contamination in foods needs to be detected, which is technologically very demanding. Secondly, storage under frozen condition reduces the viability of the bacteria, which again reduces the detection sensitivity. Therefore, technological innovation is in real need.
On account of these situations, many of the cases are often classed as "claims of symptoms" without infection source(s) being identified. The actual number of Campylobacter enteritis cases per year is now estimated to be about 1,500,000, far exceeding the reported number (see p. 5 of this issue).
It should be remembered that Guillain-Barre syndrome, a neuroparalytic disease that occurs in 1-2 in 100,000 population, is now associated with Campylobacter infection.
Expert Committee on Microorganisms/Viruses, Food Safety Commission, Cabinet Office, conducted risk assessment of C. jejuni/coli in chicken meat in June 2009. The Committee concluded that consumption of raw chicken meat increases the probability of Campylobacter infection significantly, and combination of avoiding cross contamination in chicken meat processing factories and reduction of contamination rate in the poultry farms greatly reduce the probability (see p. 5 of this issue).
Campylobacter food poisoning can be prevented not only by avoiding consumption of raw meat, but also by thorough cooking and by avoiding cross-contamination to other food (particularly those consumed raw) through chopping boards, other cooking devices or unwashed fingers. Avoiding consumption of raw meat also reduces the risk to infection by enterohemorrhagic Escherichia coli , hepatitis E virus and other enteric pathogens. The Ministry of Health, Labour and Welfare (MHLW), the Tokyo Metropolitan government (TMG) and other local governments are diffusing the necessary information to consumers through web sites (MHLW: Prevention of Campylobacter food poisoning, Q&A, http://www.mhlw.go.jp/qa/syokuhin/campylo/index.html; TMG: Wait a moment! before eating raw meat, http://www.fukushihoken.metro.tokyo.jp/kenkou/anzen/anzen_info/nama/index.html). These activities should be further strengthened.
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