**2. Risk factors for food poisoning**

With regard to food poisoning, several factors play a role in its occurrence. These factors include the individual factors such as their age, gender, socioeconomic status, their residence, health status and others; other factors include the contextual country and place of residence together with the characteristics of their macro- and micro-environment as explained below.

In the macro-environment, the chemicals and biological agents are found in environmental media such as water, soil, air and food itself. Moreover, there are interactions between these media with regard to food poisoning. For instances, crops grown in soils that are polluted by heavy metals and other chemicals as well as those sprayed with toxic pesticides may contain high levels of these chemicals that may lead to acute or chronic poisoning based on the circumstances of consumption [64, 65].

Several contextual determinants affect the occurrence of food poisoning; these include the accessibility, the availability, the affordability of controlled chemicals and drugs that may be used for instance in para- or suicide, criminal food poisoning or harvesting of fish or hunting. Other associated determinants are the seriousness of the rule of law and the enforcement of food control regulations. Sadly, in African settings, even controlled chemicals such as pesti‐ cides and pharmaceuticals can be found and brought from the streets in most cities. And as discussed further, foods vended in the streets are one of the major risk factors for food poisoning [66–69].

Foods and drinks form part of the micro-environment as they are found in the house where people live and at other settings, such as workplaces and places of entertainment. The presence of foods in the household means that accessibility and availability are guaranteed. Hence, if the storage and means of preparations are inadequate, the foodstuffs or drinks may be subjected to spoilage, contamination or chemical degradation and fermentation that would render them prone to cause food poisoning. This observation is equally true for restaurants and other food-serving venues [69–71].

If any of these areas in the micro-environment have food likely to cause poisoning, the only determinant that will trigger the occurrence of food poisoning will be the individual circum‐ stances including how susceptible the person is to the toxic agents in the offending food, the freedom of choice they have, which is linked to their economic status and the amount of offending food consumed [72–74].

Furthermore as explained by Haddon [75], several factors are involved in the three phases of a poisoning event. These phases are the pre-event, the event and the post-event. It is noted that factors in the pre-event phase contribute to the likelihood or the possibility that a poisoning event may occur; the factors mediating in the event phase affect the likelihood that a poisoning event or an injury will actually occur and how severe it would be. Finally, the factors in the post-event phase influence the outcomes or consequences of the poisoning event once it has occurred.

In the case of acute food poisoning, the factors in the 'pre-event phase' include the whole political and regulatory frameworks that ensure that crops and foods standards of quality and safety are respected by producers, importers and retailers in such a way that consumers can have access to foods that are safe and nutritious [76, 77].

In the event phase, the sociodemographic, socioeconomic and psychosocial factors of the potential victims of poisoning determine whether they will consume foods that will lead to a poisoning event. These include their age, gender, socioeconomic status, how hungry they are and the type and state of foods available to them. While, in the post-event phase, the factors in this phase include the promptness and quality of care that the victims of food poisoning will receive in line with the existing health care system [78].

Figure 1. Phases of a poisoning incident. Source: Malangu (2011). Acute poisoning in three African countries: Botswana, South Africa Source: Malangu (2011). Acute poisoning in three African countries: Botswana, South Africa and Uganda. Available at: http://hdl.handle.net/10386/674.

The above phases of poisoning event are intertwined in their interactions; the country' context, the individual characteristics and the status of offending foodstuffs combine to determine whether a food poisoning occurs or not. Whether the country is experiencing food shortage or there is food for everyone depends on the economic situation and on the distribution of income across various segments of the populations [79–81]. As depicted below, the country's context and the characteristics of an individual interact to produce the

type of poisoning as well as the outcomes of the incident.

and Uganda. Available at: http://hdl.handle.net/10386/674. **Figure 1.** Phases of a poisoning incident.

The above phases of poisoning event are intertwined in their interactions; the country' context, the individual characteristics and the status of offending foodstuffs combine to determine whether a food poisoning occurs or not. Whether the country is experiencing food shortage or there is food for everyone depends on the economic situation and on the distribution of income across various segments of the populations [79–81]. As depicted below, the country's context and the characteristics of an individual interact to produce the type of poisoning as well as the outcomes of the incident. determine whether a food poisoning occurs or not. Whether the country is experiencing food shortage or there is food for everyone depends on the economic situation and on the distribution of income across various segments of the populations [79–81]. As depicted below, the country's context and the characteristics of an individual interact to produce the type of poisoning as well as the outcomes of the incident.

context, the individual characteristics and the status of offending foodstuffs combine to

Source: Malangu, N. (2014). Contribution of plants and traditional medicines to the disparities and similarities in acute poisoning incidents in Botswana, South Africa and Uganda. African Journal of Tradition Complement Altern Medicine 11(2): 425–438.

**Figure 2.** Risk factors involved in the occurrence of a poisoning incident.

Figure 2. Risk factors involved in the occurrence of a poisoning incident.

Page **15** of **55** With regard to sociodemographic factors of individuals, a comparative study of acute poisoning in three countries reported that females were more significantly affected by food poisoning than men in Botswana and Uganda, as well as in South Africa although the difference was not statistically significant. With regard to age, food poisoning occurred in ≤10% of cases and affected more young adults aged 20 to 30 years in South Africa; more adults aged over 30 years in Uganda; while in Botswana food poisoning affected equally children younger than 12 years old and adults over 30 years [78].

The above findings suggest that the contextual circumstances of individuals in their respective countries affected the onset of food poisoning. It also suggests that all strata of populations are susceptible to food poisoning particularly to staphylococcal food poisoning. However, the severity of symptoms may vary depending on the amount of the offending agent consumed in the food and the general health status of affected individuals. Hence, the young and elderly, because of their weak immune status or defence mechanisms, are more likely to develop more serious symptoms [82–84].

Moreover, although noroviruses have been reported as a leading cause of sporadic cases and outbreaks of acute gastroenteritis across all age groups, a systematic review estimated that 12% of all cases of sporadic acute gastroenteritis caused by *Norovirus* occur in children [85].

With regard to socioeconomic and regulatory factors, in the African region, poverty is considered as the underlying cause of consumption of unsafe foodstuffs that are likely to cause food poisoning because it exacerbates food safety problems through unsanitary living conditions in rapidly growing urban centres, lack of access to clean water, unhygienic transportation and storage of foods and low education levels among consumers and food handlers, together with a false sense of invulnerability as people eat unsafe foods with the belief that nothing will happen to them [86–89]. The poor environmental conditions, particu‐ larly unsafe sanitation systems, exacerbate the situation as explained above.

Interestingly, most countries do not have appropriate policies and legislation to deal with street vending [90]. Even when national legislation and regulations exist, there is a limited capacity and capabilities to control the quality of both locally produced and imported foodstuffs [91]. It has been documented that several street food vending facilities often do not meet proper hygiene standards, in large part because of weak regulatory systems, inadequate food safety laws, lack of financial resources to invest in safer equipment and lack of education for food handlers [92]. Because street food is frequently cooked well in advance of consumption, it is prone to contamination from exposure to dust, flies, bacteria and their spores. The handling and processing of foods by the preparers who may be carrying germs open opportunities for contamination of food if adequate precautions are not implemented [93, 94].

Yet because of inadequate coordination between surveillance, food laboratories and food inspection services, there is a disorganised sampling and quality control of foodstuffs. Furthermore, the emphasis is on sampling for enforcement purposes and often there is no systematic monitoring for food contaminants as well as no surveillance systems capable of identifying common agents of foodborne diseases [95, 96].

Moreover, food safety control laboratories generally do not exist in some countries; and when they do exist, they do not function as a result of lack of human, material and financial resources. In addition, most of the public health laboratories in the African region lack the capacity to test for chemical contaminants and naturally occurring toxins [97, 98]. There is a lack of skilled inspectors who have relevant competencies and means to do their work properly [97, 99, 100].

With regard to environmental factors, it is also established that they contribute to the occurrence of food poisoning. As explained above, food may serve as a carrier of either the microorganisms (bacteria, parasite or virus) or chemicals that ultimately elicit the symp‐ toms of food poisoning. Several well-known examples of food poisoning in which the environment has a strong influence include the case of *Salmonella* spp. and heavy metals poisoning from drinking water. Contamination of surface and ground waters by pesticides is a clear example of the influence of poor environmental management resulting in poison‐ ing [34, 40, 102]. Other examples are *S. aureus*, a bacterium that causes food poisoning, and

Source: Mwamakamba, L., Mensah, P., Takyiwa, K., et al. (2012). Developing and maintaining national food safety con‐ trol systems: Experiences from the WHO African region. African Journal of Food, Agriculture, Nutrition and Develop‐ ment 12(4): 6291–6304. – African Scholarly Science Trust.

**Figure 3.** Status of food policy formulation in Africa.

*S. aureus*, a bacterium that is commonly found in the environment (soil, water and air) and also found in the nose and on the skin of humans. It is established that food handlers carrying enterotoxin-producing *S. aureus* in their noses or on their hands are regarded as the main source of food contamination via direct contact orthrough respiratory secretions when proper hygiene is not maintained [103].

This situation is not unique to Africa. A survey of food from retail markets and dairy farms in Turkey was performed between 2007 and 2008. Enterotoxigenic *S. aureus* was found in at least 10% of samples of meat and unpasteurised milk but in less than 10% of samples of dairy and bakery products [104]. While in an Italian survey performed between 2003 and 2005, also less than 10% of samples of dairy products and meat products were tested positive for *S. aureus*  [105]. In Japan, a retail survey performed between 2002 and 2003 found 17.6% of raw chicken were tested positive for *S. aureus* [106].

Another case involves *Vibrio* species that grow naturally in marine environments worldwide and are able to survive and replicate in contaminated bodies of water particularly those with increased salinity. The *V. cholerae* "O1 and O139" produce cholera toxin, which is responsible for the onset of cholera. Asymptomatically, infected humans can also be an important reservoir for this organism in areas where *V. cholerae* disease is endemic. It has been reported that water contaminated with human faeces or sewage is the main route of infection, but some cases have resulted from the consumption of fish and other seafood products [107, 108].

In the case of seafood, it is known that some of them are susceptible to surface or tissue contamination originating from the marine environment due to polluted waters from broken sewage, overboard sewage discharge and sewage run-off after heavy rains or flooding. Moreover, during various processing and preparation activities, contamination of seafood by pathogens with a human reservoir can occur. Other contributing factors may include inap‐ propriate storage and transportation at inappropriate temperatures and cross-contamination through contact with contaminated seafood or seawater [109].

In the case of agricultural products, several reports have been written about fungal toxins, namely mycotoxins such as aflatoxins, which pose a serious challenge as they contaminate various agricultural commodities either before harvest or under post-harvest conditions [110, 111]. Generally, tropical conditions such as high temperatures and moisture, unseasonal rains during harvest and flash floods are favourable to fungal growth and production of mycotoxins. Additionally, poor harvesting practices, improper storage and less than optimal conditions during transport and storage at market places can also contribute to fungal growth and increase the risk of mycotoxin production. Hence, chronic poisoning due to foodstuffs containing aflatoxins has been reported [112–115].

Similarly, food processing factors play a role in the onset of food poisoning mediated by meat. For instance, the level of bacterial contamination associated with live animals can be amplified through slaughtering plant operations. During transportation, the animals infected with *Salmonella* do shed it and thus contaminate other animals. The level of contamination is believed to increase during the containment of the animals in holding pens before slaughter [116]. After slaughter, the subsequent dressing of meats increases the spread of *Salmonella* on meat surfaces and by the time the meat is in retail outlets, contamination levels may have increased by up to 20% [17].

Street vending of foods is also a major risk factor for food poisoning. The major concern with street foods is their safety, mainly because vending is done in places that may have poor sanitation and inappropriate utensils. Street foods in some African countries have been tested for various microorganisms including faecal coliforms, *E. coli*, *S. aureus*, *Salmonella* spp. and *B. cereus*. It is noted that *E. coli* and *S. aureus* were recovered in a significant proportion of the food, water, hand and surface swabs tested in Harare. Samples of fufu and other staple foods tested in Accra yielded positive results and counts for *E. coli* and *S. aureus*. One study reported that of 511 street food items examined in Accra, up to 69% contained bacteria. In the same study, *Shigella sonnei* was isolated from macaroni, *Salmonella arizonae* from meat-based soup and *E. coli* from macaroni, tomato stew and rice. In a separate study, it was observed that over 26% of street food samples analysed in Nigeria contained *B. cereus*, whereas 16% contained *S. aureus* [117–120].

#### In North Africa

The following discussion illustrates the issues about mycotoxins. These substances are ingested orally but they may also be inhaled and may be transdermally absorbed. Of the more than 400 mycotoxins identified in the world, ochratoxin A (OTA) is one of the most prevalent. It is a ubiquitous mycotoxin produced by several fungal species belonging to the genera *Aspergillus* such as *Aspergillus ochraceus* and *Penicillium* such as *Penicillium verrucosum*, is responsible for chronic food poisoning in North Africa [120, 121]. OTA contaminates several agricultural products such as wheat, barley, rice and sorghum, cereal-derived products, dried fruits, spices, beer and wine. Additionally, OTA was found in high amounts in animal feeds. Because of its long elimination half-life (about 35 days in serum), as a consequence of its binding to plasma proteins, its enterohepatic circulation and its reabsorption from urine, OTA is the most detected mycotoxin in human blood. Its human exposure has been clearly dem‐ onstrated by its detection in human blood and urine (Zimmerli and Dick, 1995; Zaied et al, 2011) [122–124]. Its adverse effects in a variety of animal species have been described, such as teratogenicity, immunotoxicity, genotoxicity and mutagenicity [125, 126]. Its most important toxic effect in humans is nephrotoxicity; it was implicated in the human "Balkan endemic nephropathy" which is similar to the Tunisian chronic interstitial nephropathy of unknown aetiology in many aspects [127, 128].

In Tunisia, a clear correlation has been established between the consumption of OTA-contami‐ nated food and nephropathy; it has been speculated that this is due to the favourable climatic, geographic, social and economic conditions that Tunisia provides for the growth and surviv‐ al of this toxigenic fungi [127–129]. Similarly, studies from Morocco have detected that of 60 samples of grains of cereals sold in Morocco, 40% to 55% of samples of corn, wheat and barley were contaminated by OTA. In a follow-up study by the same authors, 10% of samples of corn flour sold in Rabat exceeded the maximum recommended limits for aflatoxins [130, 131].

#### In East Africa

The following discussion illustrates the role of food handlers in the onset of food poisoning. In Ethiopia, the prevalence of intestinal parasites among food handlers was found to be 29.1% to 63% [132]. This high prevalence has been attributed to poor personal hygienic practices and poor environmental sanitation. Of concern is that in one study, 6.5% of food handlers working in the kitchens had been suffering from diarrhoea at the time of the survey. And the microor‐ ganisms associated with the diarrhoea were identified as *Entamoeba histolytica*, *Giardia lam‐ blia* and larva of *Strongyloides stercoralis*. It is important to note that food handlers can directly transmit *Giardia* to consumers if they do not exercise appropriate hygiene practices [131, 133].

#### In Central Africa

The following discussion illustrates how food poisoning can result from the way the food is harvested. The use of plant-based poisons to harvest fish and bush meat has been in Africa since centuries. Plants such as *Tephrosia* sp. and *Mundulea sericea* were used throughout tropical Africa; but in recent years, because of their ease of accessibility, availability and affordability, synthetic chemicals are used to harvest fish in the Democratic Republic of the Congo and Cameroon and to kill birds and animals even vultures in several African countries [134–137].

In southern Cameroon, some respondents in a survey claimed that eating fish harvested with the use of synthetic chemicals induced vomiting and stomach pains, and in some cases even death (reference). It is also reported there that a massive killing of cane rats (*Thryonomys* spp.) has been performed using pesticides. These rats were subsequently eaten as bushmeat. A major incident of human deaths due to eating fish contaminated with pesticides occurred around Lake Victoria and ultimately prompted authorities to take action against this fishing method [136–140].

#### In West Africa

The influence of lack of knowledge and relevant equipment for safe handling of food proc‐ essing activities as well as cultural ethos in the onset of food poisoning is plausible as shown in the following reports. In Nigeria, it has been reported that the unhygienic states of some restaurants have contributed to the onset of foodborne diseases. It is known that in some parts of Nigeria, food poisoning is believed to be associated with evil spirit, malice or curses. Moreover, an urban adult Nigerian eat food from street vendors regularly because it is easily available, affordable and usually fresh [141–144].

However, street-vended foods pose some risks due to lack of basic infrastructure and services, such as potable water and reliable electricity, as well as poor knowledge of basic food safety measures. In addition, there are other issues such as poor drainage systems, unsanitary waste disposal systems, presence of flies and apparent lack of facilities for food protection [118, 120, 145, 146]. Inappropriate personal hygiene practices such as the use of unwashed fingers to feel foodstuffs or sometimes to dish out augur a high potential for contamination in the handling and preparation of foods. Moreover, an investigation about food poisoning among three families in Kano due to yam flour consumption showed that the use of certain unsafe preser‐ vatives for the processing of yam flour was responsible for the incident [142–144, 147]. Furthermore, the lack of regulatory monitoring of foodstuffs results in unsafe foodstuffs being sold in the market. For instance, a recent survey of heavy metal levels in commonly consumed canned and non-canned beverages available in the Nigerian market indicated a high preva‐ lence of beverages with levels of heavy metals that exceed the maximum contaminant levels (MCLs) for these metals [148–150].

#### In Southern Africa

The influence of food processing factors in the occurrence of food poisoning is illustrated as follows. Botswana is one of the leading beef cattle–rearing countries in Africa. Although as a semi-desert, the country is fairly free from most tropical diseases that are associated with heavy rainfall and high humidity, foodborne diseases which have been reported in Botswana to be mainly associated with poor handling as well as lack of awareness with regard to safety of food [151]. It has been observed that the meat exported from the country undergoes extensive scrutiny by both local and international experts under the supervision of the Botswana Meat Commission and the European Commission (EEC); yet *Salmonella* spp. has been isolated in local abattoirs, which process meat for local consumption [151, 152].

In Mozambique, cassava is one of the main staple foods in some areas where it is harvested from August to October each year. Bitter cassava, which is high in cyanogenic glucoside content, is mostly produced and harvested. Hence, indigenous knowledge has taught com‐ munities that sun drying preceded or not by fermentation is the process that helps to lower the cyanogenic glucosides [153]. Sometimes this is not done. Consequently poisoning may result from this mishap. In 1981, the first epidemic of Konzo was reported in Mozambique; over 1,100 cases occurred in northern Nampula Province. This condition, Konzo, is character‐ ised by the sudden onset of irreversible spastic paraparesis. Epidemiological findings showed that this was associated with prolonged high dietary cyanogenic glucoside consumption and a diet deficient in sulphur amino acids. Laboratory findings confirmed that people in the affected areas had high serum thiocyanate concentrations [154–157]. Sadly, Konzo is report‐ edly still spreading to new areas in Mozambique; it is being diagnosed outside major agricul‐ tural crises, with persistent cases and smaller epidemics. Affected communities continue to suffer cyanide intoxication at the time of the cassava harvest [158–160].
