A few days earlier, one of my colleagues asked me, Pests can cause what kind of contamination. Although I was not prepared for the question at that moment, I gave a glimpse of some insects and animal pests, which frequently contaminate foods.

pests can cause what kind of contamination

However, I was not satisfied with the answer. In the end, it pushed me to learn more about the relationship between pests and food contamination.

According to a report in 2010 from the U.S. Centers for Disease Control and Prevention (CDC), around 48 million Americans get sick, 128,000 hospitalized, and 3000 die every year from pests’ related food poisoning. Therefore, it is not so hard to imagine the global impacts of pests contamination.

These encouraged me to share a little information about pests and what kind of food contamination they can cause.

What is a pest?

Pests are living organisms, insects, or animals which directly or indirectly harm human or human properties. Additionally, they can cause damage to human health, livestock, plants, corps, even your home.

Rats are an excellent example of pests that destroy belongings and spread diseases. Even your dogs and cats fall on this group if they spoil foods or other things in your home.

Fortunately, not all pests are responsible for food contamination. Most well-known pests are cockroaches, rats, house flies, cats, house lizards, beetles, moths, and mites that corrupt foods.

What is food contamination?

Corruption of food by another substance, either physical, chemical, or biological, is referred to as food contamination.

Food contamination can happen in any step of production to ingestion. It is a universal health hazard.

According to the World Health Organization, around 600 million people fall ill, and 420,000 people die every year by eating contaminated food.

Children under five years are the most vulnerable. The report says 40% of the foodborne diseases affect children with 125,000 death each year.

Food contamination is the predominant reason for diarrhea around the world. Each year 550 million people get sick, and 230,000 people die due to contaminated foods. 

Several insects and animals primarily cause food contamination.

Pests such as cockroaches, house flies, and rodents spread hundreds of diseases in humans. The majority of them scatter through foods.

How food contamination occur?

Food corruption can happen in four different ways. What interesting is, pests can cause all kinds of contamination. Those methods are known as physical, biological, chemical, and cross-contamination.

Physical contamination

Physical contamination refers to when a foreign object mixes with foods. These include hair, nails, rats droppings, body parts of dead cockroaches, flies, and beetles. Moreover, steel, wool, and a piece of plastics may also cause physical contamination.

Physical contamination could injure a person after unintentional consumption. In addition to that, they can carry viruses, bacteria, and parasites, which in turn trigger disease manifestation.

Biological contamination

Biological contamination is the main reason for foodborne illness. It refers to food contaminated by harmful pathogens and has the potential to induce acute or chronic illness.

Viruses and bacteria are typically the most common vectors of biological contamination. They are responsible for a wide variety of food poisoning that includes E. coli, salmonella, campylobacter, cholera, and norovirus.

Chemical contamination

Chemical contamination is when toxic chemicals contaminate foods. Widespread use of pesticides in the fields and storage centers are the primary reason.

These toxic substances, if ingested in an inappropriate dose, can be fatal. It can lead to acute poisoning as well as long term illness such as cancer.


Cross-contamination is the transfer of physical, biological, and chemical contaminants into foods from indirect sources, resulting in unsafe to eat and risking foodborne disease.

It is a massive problem involving the food business. Therefore, it extremely important to increase awareness of how to handle food and hygiene.

Pests can cause what kind of contamination

Pests contaminate foods by all four methods. Suppose you found few body parts of cockroach, flies, or even pop of rats in your grains. Furthermore, you may often notice live insects roaming on your rice or wheat, or on the fruits. Resulting in physical contamination by pests.

Besides, those live or dead insects carry hundreds of harmful pathogens. If you don’t care about your food hygiene, you may infect yourself with these deadly organisms. That implies biological contamination.

On the other hand, chemical contamination most often not directly occur by pests, rather humans themselves do this.

To kill corps bugs, moths, and other harmful insects we use pesticides, not only in the fields but also in the storehouses. If these substances not used in a properly regulated manner, they can affect human health negatively.

In addition to that, pests also are able to cross-contaminate food. For example, you placed an uncontaminated piece of meats with a contaminated one, as a consequence, bacteria, viruses, or parasites can travel from a dirty one to a clean one.

Or possibly you used a piece of contaminated equipment to process the meats, which transferred pathogens. Therefore if you eat that contaminated food, you may get sick. That’s how cross-contamination occurs.

The fact is, pests can contaminate foods in many ways, either directly or indirectly.

That is why, one should be aware of the most common pests which cause contamination, as well as the diseases, arise from that. In the lower section of this article, I am going to give you some insight into that.

Common pests that can cause food contamination

Know what, hundreds of pests can cause food contamination. Here, you will learn about the common pests around you that are continuously poisoning.

Flies: House flies are the most significant source of food contamination. A single fly carries more than 100 pathogens and spread more than 65 diseases.

house fly: pests contamination

One study in 2015, scientists isolated 394 bacterial strains from 275 house flies. The most prevalent bacteria were Bacillus spp, with 31.1%, followed by Staphylococcus spp. (22.9%) and Escherichia coli (11.6%). These organisms have the ability to infect humans in a devastating way.

Cockroach: It is one of the most common pests visible globally. Cockroaches spread at least 33 deadly bacteria and 6 parasites.

They can contaminate foods with saliva, body parts, even walking over your meals. They would invade your kitchen even though you keep it clean.

Cockroaches generally scavenge in waste bins and carry harmful bacteria with their legs, wings, and digestive system. Later on, when they come in contact with foods, drop organisms such as E.coli, Staphylococcus spp, Salmonella spp and make you sick.

Rats and mice: They are the worst and destructive pests you ever heard of. Rats and mice eat or contaminate at least 20% of the total foods in the world each year.

Besides, they live in almost all households and farmlands. They destroy foods, furniture, books, cloth and surprisingly make fire by gnawing on electric cables.

Furthermore, they eat enormous amounts of food and contaminate it by their urine, faeces, and fur. Moreover, rats are incredibly potent in spreading disease.

The common diseases spread by rats are leptospirosis, plague, rat-bite fever, hemorrhagic fever with renal syndrome.

Flour beetles and weevils: weevils and flour beetles typically infest foods from warehouses and grocery stores. They destroy flour, rice, pasta, and cereals.

beetles: pests

Red flour beetles are the most common insects that are found in stored rice and flour.

You may notice some of your rice or other grains have small holes and completely collapse on gentle pressing. That’s because weevils or beetles may have already eaten them.

These insects generally contaminate foods with their legs, wings, and cast of skin. Although they destroy foods, and it is rather costly, they relatively spread less disease.

House lizards: lizards physically contaminate foods by their faeces and sometimes with eggs. They hang around the ceiling to find prey and drop faecal matter down on the foods. They even lay eggs on well packaged and stored foods.

Indian-meal moth: Unlike other moths, Indian meal moths reside and reproduce primarily in food packaging and processing plants. Their larvae eat, grow, and spoil foods, of which the financial burden is high. However, they don’t pose serious threats to human health.

Ants: If you like sweet foods, you know that ants are your prime enemy. They are present in every household and have a fascination with sugary foods. You might already be familiar with dead ants scattered on your milk bootle or in sweetened foods.

Birds: Birds are one of the common threats for fruit business.

When I was a child, I saw in every morning that bats and parrots damaged our mangoes and litchi. Moreover, It was impossible to prevent bats from contaminating date juice.

Bats leaking raw date juice

In 2018 in India, bats claimed 17 life by spreading the Nipah virus through raw date sap. Unfortunately, it has no existing treatment available.

In present days governments in many South Asian nations have to take extra precautions during the winter season because of the Nipah virus.

Furthermore, birds often eat and defecate on the corps, which transfer to the foods during packaging if not appropriately regulated.

There are many more pests that can contaminate foods. Even dogs and cats regularly contaminate foods.

In many parts of the world, dogs and cats are seen as dirty animals. They often steal or leak foods and drinks, resulting in damaging the whole meals. However, here I gave some examples of pests,  what kind of disease they can cause by food contamination.

Common diseases spread by pests contamination

Pests contamination can cause a wide variety of diseases. Below is a little list of pests contamination diseases that affect humans and are typically known as foodborne disease.

Bacterial disease

  • Salmonella, Campylobacter, and Escherichia coli: These are among the most common types of pathogens that spread by pests and affect millions of people annually. The outcomes sometime could be severe and fatal. Fever, headache, diarrhoea, vomiting are some prominent symptoms. House flies and cockroaches commonly spread these bacteria.
  • Listeria: It is one of the deadliest foodborne diseases that pests can spread. Listeria can lead to unplanned abortion and could be fatal among children and the elderly.
  • Vibrio cholera: It is famous for its quick epidemic transformation. Flies are the main culprit among pests that transfer cholera. Symptoms include vomiting, abdominal pain, and watery diarrhoea resulting in severe dehydration, even death.

Viral disease

House flies and cockroaches mainly transfer norovirus and rarely hepatitis A virus. Norovirus causes Abdominal pain, vomiting, and diarrhoea. Whereas Hepatitis A affects the liver and can have a long-lasting effect.


Echinococcus spp, or Taenia solium commonly spread by pests. Other parasites such as Ascaris, Cryptosporidium, Entamoeba histolytica may enter into the food chain through pests, especially cockroaches. 

Who is at risk for pests contamination

Insects and animals love garbage for finding foods. Therefore, those who live in an unhygienic lifestyle and don’t care about clean waste materials are most prone to have pests contamination.

Health hazards that occur due to contamination, first affect the weaker group in society. However, unsafe foods pose threats to everyone.

Toxic compounds in the foods exert long-lasting effects as they are one of the primary precursors of cancer.

Infants, young children, pregnant women, older people, and those who have the underlying disease are at higher risk.

Moreover, pests contamination is a threat to the nutritional status where food supply is insecure.

Few tips to get rid of pests contamination

I believe everyone knows how to get rid of pests. Nevertheless, some essential steps can ensure better protection of your foods from harmful bugs.

  • Make sure you buy quality products that were packaged recently
  • Don’t store grains such as rice, corn, wheat, nuts for a long time
  • Repair cracks and holes in your wall regularly
  • Make sure that adequate sun and air enter in your house
  • Store dry foods in a closed container
  • Necessary kitchen equipment should keep hanging
  • Frequently dispose of waste products
  • Always wash equipment before using
  • Always keep dinning and kitchen clean and sanitize

I think that should be enough to minimize pests contamination.

Signs of Pest infestation

To prevent pests from infestation, you must have to understand a few signs.

  • Eggs casing of cockroaches, which are small black, brown or red shells
  • Cockroach produce a robust oily smell
  • You may see flies regularly flying near your establishments
  • A large number of flies around waste bins
  • Small droppings of rats and mice
  • A strong odor of ammonia ( rats urine)
  • Small pieces of cloths or paper, rats use to make nests
  • Little droppings of house lizards with a whitetail
  • Casts of moths skin in your kitchen

Few last words

Pests contamination is a global issue. It is a challenge to our food security.

Nevertheless, it is practically impossible and not viable to think that we can eradicate pests contamination. But we can minimize the effects by taking a few simple steps.

On the other hand, those animals play a vital role in the maintenance of the ecosystem. Therefore, pests are essential for the world itself.

In fact, if we maintain cleanness and hygiene to minimize the effects, we don’t need to kill them.

Dr Mazharul Islam

Dr. Mazharul Islam acquired a Bachelor of Medicine and Bachelor of Surgery from Sylhet MAG Osmany Medical College and trained in internal medicine at Dhaka Medical College, Bangladesh. He is a practicing and motivated Medical doctor. He is exclusively working to eliminate superstitious belief from the society


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