FOOD BORNE INFECTIONS AND FOOD POISONING
Raw foods such as meat, fish, milk and vegetables grown on sewage purchased from the market are likely to be contaminated with harmful microorganisms. These are generally destroyed during cooking or processing of the food. Some of the microorganisms may survive due to inadequate heat processing. Further, some of the foods if consumed in the raw state can cause food poisoning Recent studies have shown that food grains when stored in humid atmosphere are infected by pathogenic fungus which can cause serious illness.
Some of the important diseases caused by pathogenic bacteria contaminating foods are discussed below:
1. Typhoid and Paratyphoid
Shell fish and vegetables grown on sewage are common carriers of typhoid and paratyphoid. Foods kept exposed for sale are liable to be infected by typhoid and paratyphoid bacteria as flies can transmit these bacteria from infected material to exposed foods. The symptoms include vomiting, diarrhoea and fever.
Botulism is usually caused by consuming canned foods contaminated by botulinum spores. The causative organism is clostridium botulinum and it produces an endotoxin, which is highly toxic. The exotoxin can be inactivated by heat The incubation period is 8-36 hours. The onset of the disease is sudden. The signs and symptoms include disturbed vision, dizziness, and sometimes headache, abdominal pain and physical exhaustion. The toxin affects the central nervous system causing paralysis affecting speech and swallowing. Death from respiratory or cardiac failure occurs after a few days.
3. Clostridium Perfringens Food Poisoning
This is mostly associated with consumption of defectively processed pre cooked meat product. The causative organism is clostridium perfringens and the symptoms are abdominal pain and diarrhoea. The incubation period is 8 - 12 hours.
4. Salmonella Food Poisoning
The causative organism is Salmonella typhosa. Defectively processed meat, fish and egg and raw vegetables grown on sewage are mainly involved in transmitting the infection. The symptoms are vomiting, diarrhoea and fever. The incubation period is 12 - 48 hours and the duration is for 1 - 7 days.
5. Staphylococcal Food Poisoning
The causative organism is staphylococcus aureus. This organism produces an exotoxin and the poisoning is due to the presence of exotoxin in the contaminated food. The toxin is heat stable. Pre cooked animal foods are most commonly involved in this type of poisoning. The symptoms are vomiting, diarrhoea and abdominal pain. The incubation period is 2 - 6 hours.
Streptococci are the causative agents for sore throat and scarlet fever.
This group causes bacillary dysentry. The symptoms are loose motions with mucous and blood and abdominal pain. It is caused mainly from consuming raw milk to which unclean water has been added and cooked food kept exposed. Flies are the common carriers of this disease, transferring the bacteria from infected material to food.
This is caused through water polluted with sewage. The viruses however only multiply in living cells and not in food. The various diseases spread include hepatitis, cholera and poliomyelitis.
Fungal Contamination of Foods
1. Fusarium and Cladosporium
This is caused due to the consumption of cereals and millets infected with fusarium and cladosporium.
2. Aspergillus Flavus
This fungus can grow in moist groundnuts, soyabean, cottonseed, legumes and cereals. It produces toxins called as aflatoxins. These can cause liver damage and cancer.
The mode of transmission and the effects of some worm infestation is given in the following list.
WORMS MODE OF TRANSMISSION
Taeria saginata : Infested pork
Taeria saginata : Through meat infested with tapeworm
Diphyllobothrun latum : Through sea fish
Ascaris lumbricoides (round worm) : Through people, food and water
Trichinella Spiralis : Fine worm transmitted through infested pork, meat and its products
Threadworms : Through food infected with human feces. Generally infects the lower bowel.
Entamoeba Histolytica : Raw vegetables grown on sewage farms
Toxicants Naturally Occuring in Some Foods
Some foods contains toxic substances which may cause serious illness when consumed in large amounts. An important example is the legume - Lathyrus sativus, which contains a toxin. When consumed in large amounts, the subjects develop a crippling disease
known as lathyrism. Some varieties of mushrooms contain toxic substances which when consumed produce serious ill effects.
Insect and Rodent Contamination of Stored Foods
1. Insect Infestation
Insect infestation of food grains causes heavy losses and damage to the quality of grains in storage. Taste, flavour, hygienic quality and acceptability of the food grains are affected due to the presence of insect excreta, insect fragments and dead insects. The content of B-Vitamins and the nutritive value of the proteins are also lowered.
Damages caused by rodents to stored foods are as follows:
1. They consume large quantities of food grains.
2. The hygienic quality of the grain is affected by the excreta of the rodents and also by some disease producing microorganisms present in the food grains. They cause diseases like leptospirosis and plague.