Incidence and distribution of foodborne acute gastroenteritis
To our knowledge, this is the first survey of foodborne acute gastroenteritis in a community population in Anhui Province, China. The monthly incidence of foodborne acute gastroenteritis recorded in the current study was 10.9%, which was higher than that reported in Italy (8.9%) [7], France (2.6%) [4], Japan (3.5%), Trinidad and Tobago (5.1%), and British Columbia, Canada (9.2%). In addition, the monthly incidence of foodborne acute gastroenteritis in the current study was greater than that previously reported in Jiangsu (4.4%) and Gansu (8.5%) [33,34,35,36,37] Provinces, China. Differences in illness prevalence may be related to exposure to risk factors, research design, and/or survey method.
Consistent with previous studies from China, the incidence of foodborne acute gastroenteritis differed in gender, age, education, economic level, and residence. In the current study, the incidence of foodborne acute gastroenteritis in women (15.3%) was double that of men (7.5%), subjects aged ≥50 years had the highest incidence of foodborne acute gastroenteritis (23.5%) and higher education (bachelor’s degree or above) was associated with the lowest incidence (6.0%). The incidence of foodborne acute gastroenteritis was lowest (7.5%) among respondents with a high income (total annual income greater than 90,000 CNY) and the incidence of foodborne acute gastroenteritis in rural residents (13.3%) was significantly higher than those living in urban areas (7.6%).
Meat and meat products, milk and dairy products, aquatic products, eggs and egg products, beans and bean products, and fruits and vegetable were the foods most commonly suspected of causing illness. Meat and meat products were the most commonly suspected foods (58.2%). The home (40.6%), street stalls (24.8%), and fast food restaurants (15.2%) were the most frequently reported locations where suspected foods were consumed. These results indicate that food hygiene inspection and food safety management of street stalls and fast-food restaurants must be increased and that information on proper food handling must be emphasized in the family environment.
Food handling in the family environment
Thorough heating of food, storing leftovers in the refrigerator, and the disinfection of kitchen utensils are critically important behaviors in the prevention of the growth of microorganisms [38, 39]. However, most people are not educated in the proper handling of food. Inappropriate food handling occurs in food production, food processing, storage, and consumption. In the current study, most respondents reported that they infrequently thoroughly heated milk (75.6%) and cooked food purchased from outside the home (71.2%). In addition, as many as 41.6% of respondents reported storing leftovers in the refrigerator infrequently.
The storage and processing of raw and cooked foods together is often the cause of cross contamination. For example, raw meat and cooked meat are often stored in the same container. In addition, foods containing toxic chemicals such as green beans and seafood are the cause of food poisoning outbreaks in China. The consumption of undercooked or raw foods that contain toxic chemicals, such as green beans and raw seafood, has led to many outbreaks of food poisoning [40, 41]. In the current study, 23.6% of respondents reported that they often store raw meat and cooked meat in the same container. Most respondents reported that they often thoroughly cook green beans (82.7%) and do not usually eat raw seafood (85.0%).
These results suggest that inappropriate food handling is prevalent among consumers in the family environment. Previous research has shown that a lack of food safety knowledge is detrimental to the behaviors of food handling [42,43,44]. These results indicate the importance of increasing education of the typical consumer on proper food handling procedures to produced long-term changes in healthier behaviors.
Food handling behaviors and foodborne acute gastroenteritis
The present study found differences in food handling behavior between respondents that reported foodborne acute gastroenteritis (case group) and those that did not (control group). The behaviors of infrequently thoroughly heating milk before eating, infrequently storing leftovers in the refrigerator, infrequently thoroughly heating leftovers stored in the refrigerator, often eating raw seafood, often storing raw meat and cooked meat in the same container, and infrequently thoroughly cooking green beans, were 1.2, 1.3, 1.6, 2.8, 2.5, and 2.0 times greater in the case group compared to the control group.
The risk of foodborne acute gastroenteritis was 4.7 times greater in those that responded “no” to “often thoroughly heat milk before eating”. Milk that is not thoroughly heated prior to drinking, can increase the risk of foodborne acute gastroenteritis. Drinking cold milk can stimulate the gastrointestinal tract and cause a negative gastrointestinal reaction [45]. In addition, reports of food quality monitoring from several cities indicate that microorganisms such as Staphylococcus aurous have been detected in milk and dairy products sold in stores [46,47,48]. As such, milk that is not heated prior to drinking may still contain high levels of microorganisms, leading to illness.
Respondents reporting that they do not often store leftovers in the refrigerator or infrequently thoroughly heat leftovers before eating were at a 1.8 and 3.3 times greater risk for foodborne gastroenteritis. Containers used for storage, storage time, and storage temperature are associated with microbial contamination of leftovers. Reusing containers that were used for cooking to store leftovers can cause cross contamination. Rapid bacterial growth occurs in leftovers that are maintained between 4 °C (40 °F) and 60 °C (140 °F) [49], and therefore leftovers must be stored in the refrigerator within 2 h. In addition, leftovers should be heated to at least 74 °C (165 °F) prior to eating in order to reduce the risk of any prior cross contamination and/or inappropriate storage temperature [49].
Infrequently thoroughly cooking green beans before eating was associated with a 2.9 times higher risk of experiencing foodborne acute gastroenteritis in the current study. Green beans can be classified into runner beans (Phaseolus coccineus), yardlong beans (Vigna unguiculata), hyacinth beans (Purple Haricot) and snap beans (P. var. chinensis Hort.). As an important crop worldwide, green beans are low in fat, high in protein, and rich in minerals and multiplex vitamins. However, the consumption of green beans is often the cause of foodborne disease outbreaks in China. Green beans contain two main substances that cause food poisoning: saponin and phytohemagglutinin. Saponin and phytohemagglutinin are relatively resistant to heat and can are only destroyed at temperatures above 100 °C (212 °F) for ten minutes [50]. Short cooking time and low cooking temperatures increase the risk of saponin and phytohemagglutinin poisoning.
Respondents reporting that they often eat raw seafood were 3.3 times more likely to experience foodborne acute gastroenteritis. One possible reason why eating raw seafood increases the risk of foodborne diseases is that seafood has been contaminated by Vibrio parahaemolyticus before consumption. In China, the detection rate of Vibrio parahaemolyticus in seafood is 25–40% [51]. The bacteria Vibrio parahaemolyticus is a major pathogen in seafood that can cause foodborne diseases outbreaks. For example, of the 2795 foodborne disease outbreaks between 2003 and 2008, 14% were caused by Vibrio parahaemolyticus. Moreover, approximately 28% of reported outbreaks caused by Vibrio parahaemolyticus were due by aquatic products [52]. Another possible cause that eating raw seafood increases the risk of foodborne diseases is that seafood eaten contains toxins, such as ciguatoxin, histamine, and saxitoxins which can also lead to foodborne diseases [53].
Food handling in the family environment is a complex behavior. Mishandling of food can occur at each step of the food chain process, from purchasing to cleaning, cooking, consuming, and storage. Consumers often do not follow proper food handling practices. Based on our study results, the following food handling behaviors are suggested. First, foods that are not immediately eaten (such as raw seafood, green beans, milk, and leftovers), must be thoroughly heated prior to eating. Second, to reduce cross contamination, containers for cooking food and storing surplus food must be kept separately. Third, leftover food must be stored in the refrigerator in a timely manner.
Limitations
While the present study provides valuable data on the risk factors associated with foodborne acute gastroenteritis, there are limitation that must be considered. Recall bias may have affected the study results. The data collected relied on respondents accurately relaying past experiences, prior to the start of the study which may result in recall errors. In particular, data on suspected foods and origin of food may be affected. In addition, respiratory diseases can be associated with symptoms similar to those in acute gastroenteritis and therefore, some cases of acute gastroenteritis may have been incorrectly diagnosed. Some respondents that were included in the study therefore, may have had respiratory disease. There was no exclusion criteria for the “control group”. And some respondents could not be excluded from the “control group”, which may have affected the study results. The “control group” was not paired with the “case group” following some criteria (e.g. gender). The distribution of some variables (e.g. gender) may be disequilibrium between the “case group” and the “control group”.