In the fight against food-borne illness, *Sun Tzu’s quote “know thine enemy and know thyself” is a good dictum to follow.
Why? Because in numerous kitchens (commercial kitchens, domestic kitchens in homes, and even communal village open-space kitchens) across the length and breadth of this country, the bugs that cause food-borne illness have been doing a lot of damage to the health and well-being of the public, and places considerable burden on the public health in Nigeria. Aided by ignorance of the populace, these pathogens seem to be having a field day. To turn the tide of this fight, folks need to know these germs, know how they infect, know the foods they are commonly associated with, know how they affect human health, and know how they can be curbed.
I have tried to profile five important food borne illness causative bugs in Nigeria in simple layman’s language as part of increasing awareness of these bugs, how they operate, and how they can be checkmated.
1. Vibrio Cholerae – Count for count, this food borne & water-borne bug has done more damage to public health in Nigeria than any other food borne illness bug.
To understand this check out my posts of 7th December and 22nd December titled 2013 Cholera Outbreak and Chronicling Cholera’s Carnage Parts 1 & 2 respectively.
Vibrio cholerae, the bug that causes cholera, is transmitted by consuming contaminated water or food washed or prepared with contaminated water or food prepared by a person sick with cholera.
Once the bug gets into the intestine of its victims it multiplies rapidly and secretes cholera toxin, it’s the toxin that does the damage by causing the intestine to release plenty of fluid that leads to its trademark symptoms; a sudden onset of watery stools and diarrhea. If not quickly treated the victims loose a lot of fluid from the body and die from dehydration. The suddenness of the watery stools and diarrhea is the characteristic of vibrio cholerae.
Hand-washing practices, properly boiling water before use, cooking food thoroughly, proper environment sanitation, use of latrines and toilets instead of open defecating are all ways of countering this bug.
2. Salmonella Spp – Salmonella bacterium is another major cause of food borne illness in Nigeria. The bug is transmitted by eating contaminated foods especially food of animal origin i.e meat, poultry, eggs, milk. However fresh produce and vegetables have also been implicated in salmonella outbreaks. The bug gets into the food chain from infected livestock and animals where the livestock has been fed with salmonella contaminated animal feed. Fresh produce are contaminated when they are irrigated with sewage water containing salmonella or fertilized with animal manure of infected animals.
Food implicated in salmonella food borne illness in Nigeria are eggs (cracked eggs & eggs smeared with feaces), edible snails, roasted chicken sold by roadside vendors, improperly cooked chicken, local soft cheese “wara”, unpasteurized (raw) milk sold as fura-de-nunu, local sandwich and local salad. The salmonella bug was isolated in fillings from sandwiches that caused an outbreak of food borne illness in Ibadan that claimed about 20 lives some years ago.
In healthy adults the bugs needs to be consumed in large numbers to cause illness, but in the young and elderly a small dose is enough to cause trouble. Even though majority of the ingested bug gets destroyed in the stomach by gastric acid, the ones that survive and pass into the intestine and multiplies there resulting in the symptoms of diarrhea, fever, nausea, vomiting and stomach cramps usually between 12 – 72 hours after ingesting the bug. The illness may last 4-7 days. Serious forms of the illness can lead to fatality when the bugs spread from the intestines to the blood stream and then to other body organs especially in the young, elderly, or the sick.
Cooking food at temperatures at 75C for is sufficient to kill the bugs. Other means of preventing the bug from infecting is by avoiding cross contamination of the bug from raw food to other food i.e. not using same utensils (chopping boards, knives, work surface) for raw foods and ready to eat foods without thoroughly washing with soap and hot water, separating raw foods from ready to eat food in storage in fridge, ensuring proper cleanliness in the kitchen, and thorough washing and sanitizing fresh produce before eating.
3. Listeria monocytogenes – A contaminant found in Nigerian foods like smoked fish, kilishi (sun-dried & partially roasted seasoned meat slices), kununzaki (fermented sorghum drink), wara (local soft cheese popular in South West Nigeria), and unpasteurized (raw) milk sold as fura-de-nunu, Listeria monocytogenes, the bug that causes Listeriosis also referred to as L.Mono, is an uncanny food borne illness bug. Uncanny in the sense that unlike most food borne illness causing bugs, L.Mono can survive and even grow at temperature as low as 0C such that it multiplies even when food is refrigerated.
Naturally existing in soil, water and vegetation from where it gets into the food chain, L.Mono can be destroyed in food by proper cooking and pasteurizing. It’s symptoms are diarrhea, vomiting, nausea, fever, and muscle aches which may begin to manifest as short as few hours to as long as 3 months after ingestion (for the very severe type). Where you see the normal symptoms of food borne illness accompanied with aches at the knees and elbows as well as stiff neck, it’s probably L.Mono at work.
Healthy adults are rarely affected by L.Mono, it’s aged/elderly persons, pregnant women, newborns, and adults with weakened immune systems that are the groups mostly at risk of this bug. And of this group pregnant women are the highest number of its victims where the bug passes from the intestine into the blood and becomes blood borne affecting the fetus resulting in miscarriage or stillbirth.
Infection by L.mono can be prevented by cooking food thoroughly to safe temperatures, by washing and proper handling of food before eating, keeping kitchen environment clean, proper handwashing, separating raw food from ready to eat food, avoiding cross contamination, and avoid eating the high risks foods as listed above.
4. Staphylococcus aureus – This bug by itself is harmless and occurs naturally on skin, hair as well as nose and throats of humans and animals. However when it gets into food it rapidly multiplies and secretes very potent toxins into the food. The major source of contamination is from food handlers and food preparers.
Once it has multiplied and produced the toxins into the food, heating treatment or cooking of the food makes no difference anymore because the toxins are very heat stable and are not easily destroyed by heat. So cooking food that has been colonized by staph aureus may destroy the bugs themselves but the toxins survive and when the food is eaten the toxins cause the illness with symptoms of vomiting, diarrhea, nausea and stomach pains typically one to six hours after ingestion of the toxin and this may last between 24 – 48 hours before it subsides.
Staph aereus need time to multiply in food to the dangerous levels that are sufficient to cause illness. Leaving food unrefrigerated for a short period gives it the chance to do this.
Moi-Moi (bean pudding), Agidi (Fermented Corn Meal), Abacha (African Salad), Suya (Roasted Meat) and similar hand prepared meals are examples of Nigerian foods implicated in staph food borne illness.
Ways to prevent staph infection are avoiding time and temperature abuse of food, proper handwashing before food preparation, not allowing food handlers (and children’s nannies & caregivers) with open sores/boils/wounds/long fingernails/skin infections/nose & eye infection to prepare food, avoid coughing and sneezing unto food, eating food immediately after preparation, rapid chilling and cold storage of food to prevent multiplication of the bug in food.
5. Aspergillus flavus – Aspergillus flavus, unlike the previous four bugs above, is not a bacteria but a fungus found in food like maize, groundnuts, sorghum, groundnuts that produce poisonous toxin. This toxin can be very dangerous when ingested and cause aflatoxicosis. It has been reported to causes liver cancer, suppresses the immune system, and retards the growth and development of children.
Even though the toxin is invisible to the naked eye, the bugs can be discerned in crops by a characteristic mould green color.
Prevention of aflatoxicosis begins at the farm by treating the crops to kill the bugs and also during storage. Infected crops are usually destroyed to prevent human consumption. However some of these infected crops inevitably enters the food chain as Agidi, the peanut paste used to prepare Kilishi, Kuli-Kuli (local snack made from fermented groundnut), Yaji (the spice that accompanies Suya) and when livestock eat feed contaminated with Aspergillus flavus.
The toxins produced by the Aspergillus bug are not affected by routine cooking temperatures, but simple food preparation methods such as sorting, washing, crushing, and dehulling may reduce aflatoxin levels (Public Health Strategies for Preventing Aflatoxin Exposure 2005).
These five food borne illness pathogens, along with other such pathogens not profiled in this post, have collectively brought a huge burden on the public health system of this country.
*Sun Tzu was a Chinese general, military strategist, and author of The Art of War, an immensely influential ancient Chinese book on military strategy. (Source: http://www.wikiquote.org)