6.3.6. Food and waterborne infections

 

Mass catering, intensified farming, industrial food production, and a largely international food market have created new, wide-ranging pathways along which infectious disease agents can spread. Changes in consumer behaviour (and, consequently, in the production and distribution of foods) have led to the situation that one contaminated part of food can affect a large number of individuals, often in geographically distant areas. Large multinational food-borne outbreaks are much more difficult to prevent and control. Effective surveillance of this group of diseases is restricted by variations in reporting systems and different degrees of coordination between food, animal and environmental control authorities. Effective prevention and control requires close collaboration not only between microbiologists and epidemiologists in public health, but also with veterinary and food safety authorities. At EU level, besides the ECDC, also the Commission, EFSA and WHO EURO are important players.

 

For several of these diseases surveillance has improved considerably in many Member States over the last decade, and it is difficult to decide whether an increase in reported incidence reflects a genuine increase or simply the improved detection. However, for two important infections, salmonellosis (including typhi and paratyphi) and shigellosis, there seems to be a declining trend in the EU. Campylobacter is the most commonly diagnosed food-borne bacteria in the EU, and may have been slightly increasing over time, while Cryptosporidium has caused waterborne outbreaks in several Member States. Although the majority of the symptomatic Campylobacter and Salmonella infections do not require any drug treatment, invasive infections do occur. Hence the monitoring of antibiotic resistance is important and should be included in the surveillance. The available vaccine for S typhi is used mostly for travellers to endemic areas.

 

Besides these important infections, there are several food or waterborne infections that are either of regional concern (brucellosis, echinococcosis, trichinellosis), or of main concern in the immuno-compromised, for the foetus or in the very young (listeriosis, toxoplasmosis). Indications are that listeriosis may be declining, but for toxoplasmosis the data are quite unreliable.

 

Hepatitis A is declining in Europe, but this also means that more and more people remain susceptible to this virus, and outbreaks are still seen in several countries. An effective vaccine is available but it is recommended mostly for travellers.

 

Cholera is exclusively an imported disease to the EU, with almost no secondary domestic cases seen in recent years. The available vaccine is used mostly for travellers to endemic areas.

Norovirus and rotavirus infections are not reportable in the EU, but are important causes of gastroenteritis all over the Union. It may be that outbreaks caused by norovirus in confined places, such as schools, hospitals and cruise ships are on the increase, but it should be noted that methods for laboratory diagnosis have really been available only in the last decade.

 

The true size of this problem is difficult to ascertain: even the best national surveillance systems miss the majority of cases, namely those patients who do not seek healthcare for their symptoms of gastroenteritis. Surveillance of these diseases remains important, not only to discover and, ideally, stop an outbreak, but even more importantly, to identify weaknesses in food (and water) processing and handling in order to make informed improvements in the future. An enhanced surveillance for all food-borne diseases (covering all the diseases, but also enhancing the collected information, including antibiotic resistance where appropriate) is therefore a priority. Such a system should integrate laboratory data, in particular from molecular sub-typing. The list of diseases currently under surveillance needs to be reviewed with regard to food-borne viruses, and rapid information exchange platforms should be established for all food-borne diseases.

 

6.3.6.1. Bacterial infections

 

Campylobacteriosis

 

Campylobacteriosis is a gastrointestinal disease caused by the bacterium Campylobacter. The most frequent route of transmission is consumption of contaminated food (mainly chicken) or water. Other risk factors include outdoor swimming and direct contact with infected animals.

The incidence of campylobacteriosis showed a steadily increasing trend from 85 000 cases in 1995, to 180 000–190 000 more recently, though this increase could be a result of better reporting (Figure 6.7). The most affected age group is children under the age of five years. The disease shows a characteristic seasonality with the highest reported numbers in the summer. A disturbingly high proportion of the Campylobacter isolates are now resistant against commonly used antibiotics such as fluoroquinolones and tetracycline.

 

Figure 6.7. Campylobacteriosis trends between 1995 - 2004

 

In 2005, more than 200 000 cases were reported, with the highest incidence reported by the Czech Republic (296 per 100 000), followed by the UK (87.95 per 100 000). Campylobacteriosis is the most commonly reported enteritis in the EU, but the high degree of under-reporting known to occur in many countries makes direct comparisons between them very difficult. Furthermore, the proportion of imported cases varies considerably between countries with 99% domestic cases in Czech Republic, Lithuania and Slovakia, whereas in Sweden and Finland, respectively 61% and 52% of reported cases were imported.

 

Salmonellosis

 

Salmonellosis is a diarrhoeal disease caused by the bacterium Salmonella. Poultry, pigs, cattle, and other animals such as reptiles serve as its reservoirs. The most frequent route of transmission is the consumption of contaminated food. After a peak in 1995, the incidence of salmonellosis in Europe has remained high, although exhibiting a decreasing trend.

 

Despite the generally decreasing trend, some countries – the Czech Republic, Denmark, Estonia, Finland, Latvia and Lithuania - have reported a 5% or more increase in incidence since 2004 . This could be due to improved surveillance systems (particularly in the new Member States), but also to the occurrence of outbreaks. A global epidemic of egg-related Salmonella enteritidis infections has heavily contributed to the European salmonellosis epidemiology, and this serotype has been by far the most common in Europe, and more dominant here than in most parts of the world.

 

In 2005, a total of 181 876 human salmonellosis cases were reported by 27 countries, with the highest incidence reported in the Czech Republic (322 per 100 000), followed by Slovakia (223.67 per 100 000). The highest incidence was reported in the age group 0–4 years (27% of cases), decreasing steadily in the older age groups. Some countries, notably Sweden, the Netherlands and Norway had a very high proportion of imported cases (77–87%).

Alternative sources of standardised information, i.e. returning travellers used as sentinels, indicate a very large under-reporting of cases in some of the Member States.

 

Typhoid fever / Paratyphoid fever

 

Typhoid/paratyphoid fever is a potentially life-threatening systemic disease caused by the Salmonella typhi and Salmonella paratyphi bacteria. Typhoid and paratyphoid fever occur worldwide and humans are the only reservoir for these bacteria. The mode of transmission is the consumption of contaminated food and water. Preventive measures include good personal and food hygiene.

 

The overall incidence rate of typhoid/paratyphoid fever has been steadily declining since 1995. The highest proportion (31%) of all reported cases (n=20 746), was reported by Italy between 1995 and 2004 (6 440 cases). In 2005, a total of 1 364 human typhoid/paratyphoid cases were reported by 26 countries. Norway, with 0.87 per 100 000, reported the highest incidence rate, followed by the UK (0.79 per 100 000).

 

Shigellosis

 

Shigellosis is a disease caused by the bacterium Shigella with the only reservoir in humans. Transmission occurs directly from person to person or indirectly via contaminated food or water. General hygiene measures are crucial, and proper hand-washing is the most effective individual way to prevent the spreading of disease. However, an outbreak of shigellosis in Germany was described linking the cause to sexual contacts between men who have sex with men.

The incidence has been declining over the last 10 years with a slight peak in 2001. In 2005, a total of 7 425 human shigellosis cases were reported by 26 countries. The European incidence rate was 1.82 per 100 000, with the highest incidence in children less than five year-old (3.5 per 100 000), representing 10% of all cases. Lithuania (13.43 per 100 000 total population), followed by Slovakia (9.51 per 100 000) reported the highest national incidence rates. As shigellosis is highly endemic in many parts of the world visited by European tourists, information about recent travel would be important to monitor for the future.

 

Verocytotoxin-producing Escherichia coli (VTEC)

 

Verocytotoxin-producing Escherichia coli (VTEC) causes an enteric infection, with often non-specific watery or bloody diarrhoea that in some cases may proceed to a severe disease with renal failure and haemorrhages: haemolytic uremic syndrome (HUS). HUS is the leading cause of acute renal failure in children, and 3–5% of patients die. The main reservoir is cattle but the bacterium has also been found in goats, sheep, pigs and wild game. The most frequent route of transmission is the consumption of contaminated food (especially beef and raw milk), or contaminated water. Direct contact with infected animals and swimming outdoors in contaminated surface waters have been shown as a possible route for acquiring the infection. Controls of VTEC infections at the farm level are important in preventing the introduction of the bacterium into the food chain. In addition, good hygiene practices in meat processing and food handling are essential preventive measures.

In the last 10 years, the incidence has more than doubled, rising from 1995 to 2002 and levelling off in more recent years. However, this data may in some countries and for some of the years include both E. coli and VTEC. The most affected age group appears to be 0–4 year one. In 2005, a total of 5 218 cases were reported by 25 countries. The Czech Republic (16.72 per 100 000) followed by Sweden (4.27 per 100 000) reported the highest incidence. A total of six outbreaks were monitored in 2005, with beef, lettuce and camembert cheese identified as the sources.

 

Yersiniosis

 

Yersiniosis is caused by the bacterium Yersinia (species other than the plague-causing Yersinia pestis). Yersiniosis occurs worldwide, but mostly in the Northern hemisphere. Pigs and cattle are known reservoirs. Infection is often acquired by eating contaminated, particularly raw or undercooked, pig meat. Other sources of infection have been vegetables kept in chilled stores for long periods.

 

In the last 10 years, the incidence rate of reported cases has been relatively stable, but clear peaks were seen in 1998 and 2002. In 2005, 23 countries notified a total of 9 564 cases of human yersiniosis with Lithuania (14.63 per 100 000) followed by Finland (12.2 per 100 000) reporting the highest incidence rates. The overall incidence in the EU was 2.23 per 100 000 per year, with children under five years old having the highest incidence (30.4 per 100 000 per year).

 

Listeriosis

 

Listeriosis is a disease caused by the bacterium Listeria monocytogenes. The infection is mostly mild and self-limiting, but may lead to abortion in pregnant women. In immuno-compromised or elderly people, listeriosis may take a severe course. Listeria is ubiquitous in the environment, and food-borne outbreaks have been detected worldwide. Many animals carry the organism in their faeces, and consumption of contaminated food is the principal route of transmission. Control measures are directed at the farm and food-processing level to prevent the contamination of food products. Preventive measures include providing appropriate information for consumers about the risks.

 

The annual incidence in Europe decreased between 1995 and 1998, but since then it has shown a sustained increasing trend. The incidence in 2004 (0.28 per 100 000 per year) was similar to that for 1995. Twenty-six countries reported 1 491 cases in 2005. Denmark (0.85 per 100 000), followed by Finland (0.69 per 100 000) reported the highest incidence rates. More than half the reported cases occurred in individuals over 65 years of age. In 2005, 96 listeriosis cases were associated with pregnancy. These were reported by Germany (56 cases), France (37 cases) and Denmark (three cases).

 

Brucellosis

 

Brucellosis is a disease caused by Brucella genus bacteria. The reservoirs for these bacteria are sheep, goat, swine and cattle. Humans become infected by direct or indirect contact with animals or animal products (including milk and dairy products) or by inhalation of aerosols. Control measures to prevent the disease in humans include controlling and eliminating the disease in animals by vaccination and/or the test-and-slaughter of infected animals and proper pasteurisation of dairy products. The number of cases steadily decreased from 1999 (just under 4 000 cases (0.87 per 100 000)) to 2004 (1 743 cases (0.38 per 100 000)). Twenty-six countries reported 1 429 cases in 2005, with an overall incidence of 0.31 per 100 000. Portugal (1.40 per 100 000), followed by Ireland (1.29 per 100 000) reported the highest incidence rates.

 

Botulism

 

Botulism is a rare but serious paralytic illness caused by a nerve toxin produced by the bacterium Clostridium botulinum. Eating food that contains the botulism toxin causes food-borne botulism, while wound botulism is caused by toxin produced from an infected wound. Botulism appears to be a serious problem in only a few countries in Europe, and the trend of the disease seems to have been stable over the years. Poland reported the most cases over the 10-year period. In 2005, a total of 152 cases were reported by 22 countries but only five reported 20 or more cases, with Lithuania reporting the highest incidence (0.15 per 100 000).

 

Cholera

 

Cholera is an acute enteric infection caused by the bacterium Vibrio cholerae. Humans are the only important reservoir, even though the bacteria can survive for a long time in contaminated coastal waters, transmitting diseases through infected seafood. Cholera is not an endemic disease in Europe. The number of imported cases has remained small; a peak of 40 cases was observed in 1998 but subsequently dropped to lower levels. In the last 10 years, 237 cases were reported ( <0.01 per 100 000 per year). In 2005, 34 cases were reported by 20 countries, of which twenty were from the UK.

 

6.3.6.2. Viral infections

 

Hepatitis A

 

Hepatitis A is a viral disease of the liver caused by hepatitis A virus (HAV). Up to 90% of HAV-infected young children do not have any symptoms. Transmission is through close contact with an infected person, or through ingestion of contaminated food, though recently sexual transmission among men who have sex with men has been described. A very effective vaccine is available. Almost 210 000 cases have been reported in Europe between 1995 and 2004, and during this period a steady decrease was observed from a peak in 1996–97 to 2000 and has remained stable since then. In 2005, 6 695 cases were reported by 25 countries. Slovakia (9.81 per 100 000) and Latvia (6.29 per 100 000) are the only countries with incidences of more than five per 100 000 per year. The highest incidence was seen in children under the age of 15.

 

6.3.6.3. Parasitic infections

 

Toxoplasmosis

 

Toxoplasmosis is caused by the protozoan parasite Toxoplasma gondii. The infection is asymptomatic in most humans, but can be life-threatening in immuno-compromised individuals. Infections in pregnant women can cause congenital toxoplasmosis, with varying degrees of foetal damage. The definitive host of T. gondii is cats. Humans are usually infected through direct exposure to faeces from infected cats or from inadequately washed contaminated fruits or vegetables, but can also become infected from the ingestion of raw or undercooked meat.

There is wide variation in the consistency of reporting, as well as in the reporting criteria. Reporting from most countries in Europe started in 1996, following the highest incidence observed in 1995 (1.68 per 100 000 per year), and has shown a steadily decreasing trend since then. In 2005, 1 519 toxoplasmosis cases were reported by 14 countries, with Lithuania (6.86 per 100 000), followed by Slovakia (4.85 per 100 000) reporting the highest incidence. As toxoplasmosis is a very common infection in humans and animals, the reported cases only reflect a minute proportion of all cases, and very few conclusions can be drawn from the data.

 

Giardiasis

 

Giardiasis is a parasitic infection caused by Giardia intestinalis (also called Giardia lamblia), causing both acute and chronic diarrhoea. Infants and children are at particular risk. Domestic and wild animals carry the parasite, although the major reservoirs are contaminated surface waters and humans. Infection occurs after ingestion of contaminated food or water, and several large waterborne outbreaks have occurred in Europe. As for many diseases, large differences between surveillance systems make comparisons between countries very difficult. However, the available data suggest a relatively stable trend over the last 10 years. In 2005, some 15 103 cases were reported by 18 countries. Estonia (24.28 per 100 000), followed by Iceland (14.65 per 100 000) reported the highest incidence rates.

 

Cryptosporidiosis

 

Cryptosporidiosis is a parasitic disease caused by Cryptosporidium, infecting many species of large and small animals. Humans can be infected from other people or from the environment. Cryptosporidiosis can be life-threatening in immuno-deficient patients. Outbreaks have been reported in child day-care centres, in families, from lakes and swimming pools and through contaminated drinking water. Cryptosporidiosis is not reportable in many countries, and trend data are scanty. In 2005, almost 8 000 cases were reported by 16 countries, with Ireland (13.75 per 100 000) and the UK (9.26 per 100 000) reporting the highest incidence rates. Most cases occurred in the age groups under 15 years. Comparisons between reporting countries are complicated due to differences in the surveillance systems.

 

Echinococcosis

 

Echinococcosis is a zoonotic parasitic disease, caused by the larval stage of the tapeworm Echinococcus. Humans are infected through close contact with infected animals (sheep, cattle, goats, horses, pigs) or through ingestion of undercooked infected food. The number of reported cases has been steadily decreasing since 1996. In 2005, altogether 337 cases were reported by 22 countries. Lithuania (0.44 per 100 000), followed by Slovenia (0.30 per 100 000), reported the highest incidence rates. The real number of cases is probably considerably higher than those reported given the slow progression of the disease over many years.

 

Trichinellosis

 

Trichinellosis is a zoonotic disease caused Trichinella. The main source of human infection is the consumption of raw or undercooked meat products from pigs, wild boar and horses. As a preventive measure, all slaughtered pigs and horses undergo an investigation for Trichinella larvae in meat inspection in the EU. The risk remains higher in imported and wild animal meat and consumption of such undercooked or raw meat should be avoided.

In the last 10 years, the incidence of trichinellosis in Europe has shown an overall decreasing trend despite peaks in Slovakia, France and Italy in 1998, in Poland 1999, in Latvia in 2000, and in Lithuania in 2001. Since 2000, the incidence has been relatively stable. In 2005, 153 cases were reported by 25 countries. Latvia (2.12 per 100 000), followed by Lithuania (0.35 per 100 000) reported the highest incidence rates. The two most affected age groups are children 5–14 years of age and adults 45–64 years of age.

 

6.3.6.4. Prion diseases

 

Variant Creutzfeldt-Jakob disease (vCJD)

 

Variant Creutzfeldt-Jakob disease (vCJD) is a novel form of human spongiform encephalopathy (prion disease), which has been causally linked to bovine spongiform encephalopathy (BSE). The disease is fatal, with a mean survival of about 14 months. The main suspected route of transmission is through past consumption of infected beef products, although recently human-to-human transmission has been described through blood transfusion. Preventive measures include ensuring that the BSE prions do not enter the human or animal food chains, and that blood or tissue for transplants from potentially infected persons are not used in medical care.

 

The transmission of vCJD through prions in the food chain has had profound political, social and economic implications. Because of the long incubation period, extending to years or even decades, there has been uncertainty about the likely extent of a future outbreak of variant CJD in the UK and in other countries. Current data are relatively reassuring, as the number of deaths from vCJD in the UK has declined over recent years after a peak registered in 2000. However, uncertainty remains about the possibility of increased numbers of cases in the future, particularly as there is now evidence of transmission of vCJD through blood transfusion.

 

Since 1995, vCJD has been detected mainly in the UK but has also been seen in six other European countries. The highest reported annual number of cases (30) was in 1999. Since 1999, the number of reported cases declined steadily until 2004

In 2005, a total of 21 cases were reported by 18 EU Member States. Slovakia reported 11 cases; however, the criteria for reporting these cases may have been different from those used in the other countries. Six cases reported in France, two in Ireland and one each in Estonia and in the Netherlands make up the remainder of the cases reported.