Diagnosis, Treatment & Control of Common Food-borne Diseases

Foodborne diseases are caused by contamination of food and occur at any stage of the food production, delivery and consumption chain. They can result from several forms of environmental contamination including pollution in water, soil or air, as well as unsafe food storage and processing.

The most common types of foodborne diseases are caused by bacteria such as Salmonella, Campylobacter, and E. coli. Other pathogens include viruses such as norovirus and hepatitis A. Symptoms of foodborne diseases can range from mild to severe and can include nausea, vomiting, diarrhea, abdominal pain, fever, headache, and body aches.

The best way to prevent foodborne diseases is to practice good hygiene and safe food handling practices such as washing hands before handling food, cooking food thoroughly, keeping hot foods hot and cold foods cold, and avoiding cross-contamination. Food-borne illnesses can thus be broadly categorized as:

Food-borne infections
Food-borne intoxications

Food-borne Infections and Intoxications

Food-borne infections occur through consumption of contaminated foods or beverages. Food intoxication occurs when toxic chemical substances produced by microorganisms in food get into the human/animal’s system and cause adverse reactions.

While some foods like mushroom, fish, and cassava may be primarily toxic, others like molluscs have secondary toxicity. When an animal eats a mollusc, it produces chemical substances that cause toxicity to their secondary host.

Food additives may also become poisonous in food during production.

Sources of food contamination

There are many sources of food contamination and various stages of the food chain including production, transport, processing, storage, and consumption levels.

The most common sources include:

i) Food animals (edible)

These may contain infectious organisms in their intestines and/or muscles that cause food contamination.

ii) Meat

May be contaminated during slaughtering or handling.

iii) Fresh fruits and vegetables

When grown in contaminated soils, these can be a source of food contamination. Contamination can also set in during handling when contaminated water is used to clean the produce.

iv) Eggs

When the hens feed on heavy metals or feed that is contaminated with chemicals, the contaminant is transferred to the final consumer through the eggs.

v) Seafood

Seafood is notorious for heavy metal contamination.

vi) Infected humans

May introduce the contamination during handling of food. The most notorious case is tuberculosis.

vii) Cross contamination

Happens when one contaminated food is mixed with a different clean food. Happens mostly during handling of raw food or during cooking.

Foods that are commonly associated with food borne diseases

Food animals; especially those that people tend to consume in their raw state like meat, fish, or milk.
Foods that mix animal products e.g. milk, eggs, and minced meat.
Fruits and vegetables since people tend to consume most of them raw.
Fresh manure when used in a vegetable farm to increase soil fertility may contaminate the plants.

People who are at risk of food-borne infections include:

It is important to note that food-borne diseases pose a risk to every living soul. However, there are those individuals with increased risk to infection than others.

For instance, people who handle animal products are at a higher risk due to their increased levels of exposure. Pregnant women, the elderly, infants, and people with compromised immunity are at a higher risk as well.

General symptoms of food-borne disease infection and general prevention measures

Most of these infections take the oral route because they tend to be consumed with the food. When infected, you will notice any or a combination of the following:

Nausea
Vomiting
Abdominal pain/cramps
Diarrhoea

To reduce the risk of infection, you can ensure the following:

Sufficient cooking of all foods, especially for animal products.
Proper preservation – refrigerate or freeze all foods of animal origin
Keep foods in separate containers (avoid mixing foods)
Use clean and sterile equipment and work surface when handling food. This goes for the water used as well.

It is usually not easy to trace the origin of an outbreak because it is not easy to tell where you might have picked an infection.

Food-borne infections could be caused by strict human pathogens such as Salmonella typhimurium or pathogens that affect both man and animal such as Salmonellosis. Either way, it is important to be safe.

Some of the very common food borne diseases and infections include:

1. Salmonellosis

This is a bacterial infection that affects both man and animal.

Aetiology (cause)

Salmonella bacteria have very many strains (over 1700) with potential to harm man and animal. It is gram negative, rod-shaped, non-lactose fermenter enterobacteria.

Salmonella typhimurium is the most common strain that affects man while Salmonella dublin causes disease in animals.

Sources

The primary source is in the intestines and they are shed in faeces. Animals and man can harbour this disease without showing any signs hence they become chronic carriers.

In such cases, the organisms reside in the gall bladder, liver, and spleen. The diseases causing microorganisms in these animals are usually transferred during slaughter.

Where commonly found

Meat and meat products such as beef, mutton, etc.
Pork (between 2 – 5 percent of all slaughtered pork contains Salmonella typhimurium in their lymph node hence continues to contaminate the rest of the products during processing).
Poultry has the highest contamination by Salmonella typhimurium in their intestines,
Eggs and egg products (especially duck eggs) pose a great danger when cracked.
Milk and milk products contain both typhimurium and S. dublin especially during warm weather and in farms that use poor milking techniques.
Direct contact with animals, animal products and carcasses of infected animals.
Water contamination from faeces
Pests and rodents who are the intermediaries for the disease especially when they come into contact with animals and food.

Clinical signs in animals

The condition is more prominent in young stock than adults that can harbour it without showing any symptoms. The symptoms include:

Anorexia
Dullness
Slight fever
Severe diarrhoea (initially watery then dysentery sets in)
Dehydration (the animals become so weak, their skin wrinkles and death follows.

Symptoms in man

In man, the disease incubates for about 36 -72 hours before showing any signs. The symptoms include:

Abdominal pains
Diarrhoea with chills
Vomiting
Fever
Headache
Prostration (weakness)
Septicaemia, which may lead to cardiac failure

Note: the severity of the symptoms depends on the dosage of the microorganism and the age of the patient.

Diagnosis and treatment

Diagnosis is done at a medical facility through lab testing. The doctor prescribes treatment depending on the lab results.

Control measures

Properly cook animal products
Ensure hygienic handling of all animal products
Use proper milking and milk handling techniques.
Never wash eggs when they are cracked

2. Typhoid Fever and Paratyphoid

Caused by two strains of Salmonella bacteria that are strictly human pathogens. They are;

S. typhi (typhoid fever) and
S. paratyphi (paratyphoid).

Aetiology

The pathogens are strictly human pathogens, especially for those who carry the disease.

The disease reaches the chronic carrier state where the hosts retain the bacteria in the gall bladder and GIT.

It affects middle-aged women more than any other group of human beings.

Transmission

Contaminated water and foods e.g. milk, fruits, and vegetable.
Can be shed through stool and urine
Mechanical transfer by insects from one food to the next

Symptoms

Incubation period for typhoid fever is between 3 – 28 days while paratyphoid incubates for between 1 -15 days. The observable symptoms include:

Septicemia
Slight fever (up to two weeks). After the 2 weeks, the organism moves from the blood into the GIT affecting the lymph nodes leading to severe abdominal pains.
Nausea
Vomiting
Diarrhoea
Rosebuds (petcheatons)
Breaking of capillaries
Kidney failure

Fatality rates in humans average 10 percent annually.

Diagnosis

Suspect the disease from the symptoms. Isolation of the bacteria from the stool is a confirmatory test for the disease. The organism can also be isolated from the blood by culturing.

Serological tests (checking the actions of antigens against this organism) can also confirm the disease.

Treatment

Seek medical attention in a hospital. Good nursing care is important for quick healing.

Control measures

Proper sewage disposal
Use boiled water for domestic consumption
Wash fruits and vegetables with clean boiled water
Consume only properly pasteurized milk
Test and treat chronic carriers
Vaccinate people (vaccines will give 2 – 3 years of protection)

Where there is a massive outbreak of this disease, people will still get it.

3. Shigellosis

It is also referred to as Bacillary Diarrhoea and is caused by a strict human pathogen.

This disease breaks out depending on geographical locations. You may not get it depending on where you stay.

It occurs in temperate countries (where it also slowly disappearing).

Aetiology

About four sub-species of the Shigellae spp are culprits. However, Enterobacteriaceae spp is the most pronounced. It produces potent toxin that affects the host.

Sources

Humans are the most common carriers. However, monkeys have been reported to carry the organism in some areas.

It occurs mainly in children, young adults and the elderly.

Foods commonly associated with this infection include:

Milk and milk products
Raw vegetables
Fish

When the infection occurs, it is common to pass it from one person to the next in 80 percent of the cases. This is not very common with food infections.

Symptoms

The organism requires a very small dose to cause a disease. The bacteria attach itself to the walls of the intestines where they multiply and produce toxins.

The toxins cause toxaemia, which spreads to other parts of the body.

Some of the common symptoms include:

Diarrhoea that comes on and off
Mild abdominal pains; you may pass a few loose stools
Nausea for people with HIV
Watery stool with mucus/pus and stained with blood.
An agonizing pain (colic) and temptation to diarrhoea (tenesmus)
Fatality is low but the rate increases in children, the elderly, and people with compromised immunity.
Patients take long to recover (about 3 months).

Diagnosis

Check the bacteria in the stool and isolate it.

Treatment

Seek medical help from a medical facility and use antibiotics. Fluid replacement (hydrotherapy) is critical.

Control measures

Maintain high standards of personal hygiene
Boil water before using it for consumption purposes
Proper sewage treatment and disposal is key
Properly pasteurize milk before consumption
Proper handling and cooking of vegetables

4. Haemorrhagic Colitis

This food borne disease is an enteropathogenic Escherichia coli infection that affects both man and animals. It is widespread in man and is very common in infants under poor sanitary conditions.

The specific strain that causes disease is E. coli 0157H.

When the bacteria cause disease in animals, the condition is referred to as colibacillosis.

Colibacillocis will occur in small animals between 1 – 14 days. They get a very serious disease that is commonly referred to as Septicaemic coli. The bacteria use the navel as the route of infection.

The disease may also affect the nervous system. It usually has very high fatality rates.

Animals that manage to recover harbour the organism in the joints leading to arthritis. If the bacteria hide in the brain, they cause meningitis, while those that hide in the lungs will cause pneumonia.

Ophthalmitis occurs if the bacteria harbours in the eyes of animals that manage to recover and enteric colibacillosis is the disease that affects animals aged between 3 – 8 months.

Predisposing factors

Overcrowding
Poor housing
Poorly lit and ventilated room
Poor waste management (including animal droppings and sewage)
Poor feeding management
Overfeeding young calves with colostrum gives the physiological diarrhoea, which impairs their immunity.
Poor hygiene management and poor milking techniques.

Sources

Intestines of animals and will be shed through faeces that contaminate water and soil. Pathogenic strains are very resistant and remain potent for long.

If any food product comes into contact with contaminated water, soil or faeces, it becomes a source of contamination.

In institutions where kids are fed using feeding bottles, there is a risk of spreading the disease if only one bottle is contaminated.

Symptoms

Incubation period is 2 – 4 days.

The bacteria attack the epithelial cells and produce toxin that causes gastroenteritis. The observable symptoms include:

Sudden onset of severe stomach pains with cramps followed by watery blood-stained diarrhoea.
Vomiting
Small fever
Fatality is not very common
The disease may progress for a week if not treated. In which case, other strains of E. coli will cause other illnesses including:

Travellers’ diarrhoea, which is usually associated with consuming unhygienic foods while travelling.

Haemolytic uremic syndrome, which is an equivalent of Septicaemic coli.

It has high fatality rates of up to 50 percent. People that manage to recover may suffer from kidney failure if the organism is logged in the kidney. Those that manage to recover may be forced to undergo dialysis for the rest of their lives.

Diagnosis

Culture the stool. It should have a high plate count.

Treatment

Hospitalization for early treatment.

Rehydration to replace the lost electrolytes and restore normal balance.

Adults may pass to notice the symptoms of the disease.

Control measures

Maintain strict hygiene
Encourage breastfeeding and maintain high standards of hygiene for the feeding utensils.
Properly cook meat and meat products, milk, and eggs. Wash vegetables and fruits properly before consuming them.
Use boiled water for domestic activities.

5. Cholera

Of all the food borne diseases, cholera is one of the most ravaging. It is caused by a strict human pathogen that spreads fast and affects many people. It usually leads to epidemics with mortality rates of up to 30 percent.

Aetiology

Caused by Vibrio cholera. The typical biotype E1 and TOR.

Epidemiology/Sources

Spread through contaminated water and the bacteria survives longer in an alkaline condition. Acidic conditions usually kill it.

It is common for this disease to occur in crowded areas. It is usually associated with symptomless carriers.

Pathogenicity is very clear. The organism is ingested through water. Once it reaches the intestines, it multiplies fast and produces an enterotoxin that causes severe enteritis (inflammation).

Symptoms

One requires a very small dose for the disease to occur. Incubation takes between 3 – 12 hours. The observable symptoms include:

Sudden onset of effortless vomiting followed by profuse diarrhoea (between 20 -30 times in a day), which leads to rapid dehydration.
“Rice” watery diarrhoea when small bits of mucosa is present in the stool
Severe dehydration that leads to suppression of urination. The patient develops wrinkled skin, sunken eye sockets and becomes very weak.
Lowering of the blood pressure leading to rapid and weak pulse. This may lead to circulatory failure and death.

Diagnosis

The bacteria are very easy to identify because it is filamentous and motile.
Cultural isolation of the stool or water can be effective as well.
Serological testing (titrating the antigen/antibody reaction) can be used to identify the microorganism.

Treatment

Immediate hospitalization. Medication with antibiotics and rehydration is very critical to survival of the patient.

Control measures

Maintain personal hygiene
Boil/treat the water you intend to use for domestic consumption
Proper sewage disposal
Hygienic handling of foods
Vaccination (effective for six months).

Atypical Cholera

Caused by Vibrio parahaemolyticus. It is usually associated with marine life and sea foods are the major culprits of the microorganism.

It incubates for 12 hours

Symptoms

Abdominal pain
Nausea
Vomiting
Diarrhoea

The disease is not as severe as typical cholera and it can end without medical intervention.

Control measures

Avoid consumption of poorly prepared sea food
Freeze the sea food; it kills these microorganisms
Avoid mixing raw with cooked food.

Food-Borne Viral Infections: Diagnosis & Control Measures

Foodborne viral infections are caused by viruses that can contaminate foods during all stages of the food supply chain. The most common types of foodborne viral infections are noroviruses and hepatitis A virus (HAV). Rotavirus is also associated with foodborne illness.

Foodborne viruses originate from the human intestine and are excreted in high numbers in the faeces or through emesis. The low infectious dose and robust survival in food and various environments facilitates the spread of viral infections.

Some of the most common food-borne viral infections include:

1. Infectious Hepatitis

Hepatitis is a common / prevalent infection that is easy to diagnose. It is caused by virus types A and B.

Aetiology

When the disease occurs, the virus is shed through the blood, stool, and urine of the infected person.

The disease is more severe in children. Adults experience a protracted period of the disease.

Transmission

Majorly transmitted through oral consumption of contaminated water by stool or urine of an infected person.

You can also get it through contact with the blood of an infected person.

Hepatitis type B can be transmitted through sexual contact.

Symptoms

Incubation period is between two and six weeks.

It takes quite long to get a slight manifestation. Some of the noticeable symptoms include:

Slight increase in body fever
General malaise
Faintness and weakness
Anorexia
Nausea
Abdominal discomfort
Liver failure symptoms (jaundice)
Ascites (accumulation of fluid in the abdomen)
Changes in urine colour due to presence of bile

Diagnosis

Once the incubation period is complete, the onset of the symptoms is characteristic.

Test the liver functions and identify the virus in the blood or urine through cultural isolation.

Control measures

Vaccination is the most effective way.
Maintain high hygiene standards for food, water, and self.
Proper sewage treatment and disposal channels.

2. Poliomyelitis

This disease can occur in apparent forms (i.e. cases where the disease is present but the patients do not show any symptom). It is caused by polio virus 1, 2, and 3.

Aetiology

The virus is shed through the stool and pharyngeal excretions. People catch the virus through consumption of contaminated water, milk, and other fluid foods.

Symptoms

Incubation takes between seven and 10 days.

It starts with fever followed by headache
General malaise
Constipation
Stiffness of the neck
Paralysis of limbs
Meningitis may also occur

Diagnosis

The symptoms are helpful in making a tentative diagnosis.

Isolate the virus from the stool and other secretions of the body.

Serological tests are also helpful in diagnosing this disease.

Control measures

Vaccination is very effective; done only once and remains effective for life.
Maintaining high standards of personal hygiene is crucial. Food and must be kept clean and uncontaminated.

General Disease Control Methods

i) Increasing the host resistance

You can achieve this in two ways:

Proper and improved nutrition
Vaccination

ii) Taming the environment

Here, you eliminate or reduce the hazards / predisposing factors to the disease. You can achieve this through environmental sanitation, e.g.

Water should be safe and adequate
The housing should be sound to eliminate physical and biological hazards
Food hygiene should be high throughout all the stages of production. Check and control the type of soil, the food storage premises, and even the chemicals used in production. Inspect and reduce all sources of contamination (including the health of human handlers). Refrigerate stored foods at the right temperature.
Conduct mass education on food hygiene
Disinfect areas where the sick animals stay to avoid contamination and cross-contamination to a healthy host. You can use chemical disinfectants or irradiation for this purpose.
Practice proper waste and sewage disposal. Properly manage and dispose industrial wastes as well
Control the quality of the air you breathe through sanitation or filtering
Minimize contact with animals to reduce chances of spread of zoonotic diseases

Food Borne Intoxications: Intentional or Accidental Food Poisoning?

Food borne intoxications are diseases/infections caused by ingestion of toxic materials found in animals and plants. They are metabolic products of microorganisms that they produce as they multiply.

Intoxication could also arise from consumption of various compounds added to food whether intentional or otherwise. These could include compounds that are generally regarded as safe (GRAS), e.g. food colouring or flavouring agents.

The most common food borne intoxications include:

1. Staphylococcus aureus intoxication

Staph. aureus is both infectious and intoxicating. It is a ubiquitous microorganism that is not easy to eliminate.

Intoxication occurs after consumption of foods containing the exotoxins produced by the bacteria.

Alternatively, one can consume the bacteria in the food and the bacteria will multiply rapidly and cause infection after reaching the GIT.

This bacterium produces toxins A, B, C, and D, which are very potent and heat stable. These toxins are also resistant to proteolytic enzymes.

These bacteria easily contaminate food due to their presence on the skin.

Predisposing factors

High levels of contamination by the bacteria
Foods at pH of 4.5
High temperatures (above 15°C; ideally between 35°C and 45°C).
The bacteria are present in the food for a long period enough to multiply and produce toxin. For instance, keeping cream at 24°C for five hours of exposure will allow for toxins to be produced. Mashed potatoes will take six hours to achieve the same results while contaminated fish will take 72 hours to produce the toxins.

Staphylococcus aureus has very poor ability to compete with other microorganisms. They occur in foods that have marked reduction in number of other microorganisms.

This is the reason why foods like cured meat and salted foods that kill other microorganisms give Staph. aureus a head start.

Sources of contamination

Man harbours this microorganism on the skin and mucus membrane.

Commonly affected foods include meat and milk products. The bacteria come from the animal and people who handle the milk and meat.

Staph. aureus also causes mastitis.

Modes of transfer

Bacteria moves from one organism to the food and the food becomes a hazard for all who consume it.

High dosage is necessary for propagation and toxin production.

Symptoms

Incubation period usually takes between one and six hours. Observable symptoms include:

Nausea and vomiting
Abdominal pain and cramps
Diarrhoea
In severe cases, blood is present in vomit and stool
Other symptoms vary based on individual status and dosage of the bacteria. They may include headache, sweating, and marked prostration.

Fatality rates are very low. Recovery happens between 24 to 72 hours.

Diagnosis

Tentative diagnosis is done from the symptoms. To confirm the disease, isolate the bacteria and the toxins.

Control measures

Avoid conditions that allow toxin production
Ensure hygienic preparation and handling of foods.
Freezing meat before cooking

2. Botulism

Botulism is an intoxication that affects both animals and people. It comes from the Latin word Botulus, which means sausage because it is majorly associated with sausages.

The disease is very common in animals and produces very severe intoxication often resulting in outbreaks.

It takes a low profile in people but will have pre-formed toxins when one gets infected.

Aetiology

The toxins are produced by Clostridium botulinum, which is harboured in the GIT. It forms highly resistant spores.

It is both proteolytic and non-proteolytic and it can cause food spoilage or produce toxins in unspoilt food.

The bacteria produce several toxins including A, B, C, D, E, and F. All these toxins will occur in both man and animals in varying severity.

Toxins C and D are very common in animals and cause intoxication in animals.

Conditions for toxin production.

A pH range of between 4.6 and 5.3 or above.

The bacteria have a range of favourable temperatures depending on the food in question. The minimum is usually between 25°C and 37°C.

However, some foods can facilitate toxin production at low temperatures of 10°C while others as high as 50°C. Toxins A and B can be produced and temperatures lower than 10°C.

Food preservation method will affect toxin production. Anything that will cause an anaerobic condition will lead to toxin production.

Sources of contamination in animals

Anything rich in organic matter (e.g. cadavers of animals that had these bacteria. Animals tend to eat these when they have pica).

Decaying plant matter may contain bacteria from dead rodents that come into contact with them. When these come into contact with animal feed, they transfer the contamination.

Sources of contamination in man

Animal proteins especially if kept improperly leading to formation of food pH of between 4.6 and 5.3. When this food is consumed after warming slightly, it leads to poisoning.

People who love to eat raw animal products are at a higher risk. Type B poisoning is common in marine foods and fresh water fish.

Highly acidic/spiced/fermented foods or foods with low protein needs delicate handling. Such food may already be spoilt but you will fail to notice it due to the food’s acidic nature. This often leads to outbreaks.

Major sources of these toxins

Toxin type A – is very common in man. It is transmitted through chicken meat, fish, and canned vegetables.

Toxin type B – will occur in both man and horses. It is associated with meat in men and forage/silage in horses.

Toxins types A and C will occur in birds that eat rotten vegetables.

Toxins C and B are common in most domestic animals. They pick the toxin from decaying organic matter.

Type B is common in cattle. They get the toxin from eating contaminated feed.

Toxin type E is usually associated with man and wild birds. They contact it from marine foods and fish.

Type F usually affects man. Common in Europe.

Symptoms of intoxication in man

The toxins interfere with the production of acetylcholine leading to motor paralysis.

Incubation period is between 12 and 36 hours. It can be shorter (4 hours) or longer (36 hours) depending on the individual.

Observable symptoms include:

Upset of the gastrointestinal tract
Nausea
Vomiting
Burning sensation
Diarrhoea with/without pain
Constipation may occur in some cases.

Nervous symptoms will set in as follows:

Dizziness followed by drying up of the mouth
Pain in the pharyngeal region
Blurred vision due to paralysis of the optical region
Mydriasis – normal dilation, jerky or involuntary
Nystagmus – when the eyes fixate on an object/target
Loss of light stimuli, which will lead to blindness
Temperature is usually unaffected and people will not lose memory.
When the muscles are affected, swallowing food will be very difficult
Pharyngeal muscles will be affected leading to respiratory failure and even death

In animals, the effects vary in severity. Mostly affected are chicken and cattle.

It will lead to sudden deaths
Paralysis is shown in uncoordinated movements
Death due to respiratory failure

Diagnosis

Tentative diagnosis from the symptoms shown. Isolate suspected foods and carry out tests to identify the toxins and/or the bacteria.

Treatment

Very difficult to treat. Give the patient antitoxins and treat the symptoms.

Control measure in animals

Vaccination protects the animals
Avoid feeding the animals on decaying hay/forage.

Control measures in man

Take great care with animal protein foods. Avoid eating cold food preserved from the previous day. Thoroughly heat it up before eating.

3. Clostridium pufringens intoxication

In animals, these bacteria produce toxins type A, B, C, D, and F. it causes what is known as enterotoxaemias.

It usually affects young animals and usually leads to high mortality rates.

Toxin A enterotoxaemia is very rare in animals. In people, they will get it when they eat preserved animal protein without sufficiently heating it first.