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Signs of a cockroach infestation

Cockroaches leave behind signs of their presence that are easy to spot before you are likely to see a live insect. As nocturnal creatures, cockroaches usually hide out of sight during the day and only become active at night to search for food.

It is important to discover a cockroach infestation as soon as possible so you can quickly take action to prevent them spreading and multiplying and minimise the health risks associated with this unhygienic insect.

Read below about the signs to look for and the places around your home or business where you can find cockroaches.

Get professional advice how to control cockroaches

Cockroaches can transmit the following diseases:

  • Salmonellosis
  • Campylobacteriosis
  • Listeriosis
  • E. coli infections
  • Typhoid fever
  • Cholera
  • Dysentery
  • Leprosy
  • Plague
  • Asthma

On this page you can also find information on:

  • How do cockroaches spread disease?
  • How can you catch a disease from cockroaches?
  • How to prevent cockroaches spreading diseases


Similar to rodents, cockroaches are known to transmit the Salmonella bacterium which can cause salmonellosis, a disease in humans with symptoms similar to food poisoning.

Cockroaches accumulate the bacteria by crawling in filth and feeding on contaminated food materials. The Salmonella remains in their digestive system for a month or more and is deposited through their vomit and faeces.

Human symptoms, which typically show 12 to 72 hours after infection, include diarrhoea, fever, and vomiting. Recovery usually occurs after four to seven days, with little to no medical treatment need, besides replenishing fluids.


Campylobacteriosis is an infection caused by the Campylobacter bacterium. It is one the most common bacterial infections in humans, and is a common foodborne illness. Researchers have isolated a Campylobacter jejuni subspecies in the gut contents and on the external surface of both American cockroaches and Oriental cockroaches.

Transmission occurs through ingesting contaminated food and drink such as unpasteurised milk and undercooked and poorly handled poultry. It can also be transmitted through sexual contact, although this is very rare.

Symptoms of campylobacteriosis include bloody diarrhoea as well as cramps, abdominal pain and fever. The disease usually lasts for 2-10 days and requires little to no medical treatment. However, as with any occurrence of diarrhoea, it is important to replenish fluids to avoid dehydration.


Listeriosis is a serious infection caused by the bacterium Listeria monocytogenes. It is usually contracted by consuming contaminated food and drink. According to the Centers for Disease Control (CDC) it is an important public health problem in the United States.

Listeriosis primarily affects people with weakened immune systems such as pregnant women, newborns and the elderly. Although rare, people with strong immune systems can also be affected.

Symptoms of listeriosis are usually a fever, muscle aches and diarrhoea. However, if the diseases spreads beyond the gastrointestinal tract, symptoms can also include headaches, a stiff neck, confusion, loss of balance and convulsions. For pregnant women, contracting listeriosis can sometimes lead to miscarriage, stillbirth or premature delivery.

E.coli Infections

Escherichia coli (E. coli) is a bacterium commonly found in the gut of humans. Although most strains of the bacteria are harmless, some can cause serious food poisoning.

The common symptoms of an E. coli infection are watery diarrhoea and abdominal cramping. Less common symptoms are:

  • Fever
  • Chills
  • Nausea
  • Muscle aches

Symptoms usually last three weeks and require little to no medical support.

Typhoid fever

Typhoid fever is a bacterial infection caused by the Salmonella typhi bacterium and is a highly infectious disease. It is believed that cockroaches accumulate this disease by consuming faeces contaminated with the bacterium.

According to the UK National Health Services (NHS) Typhoid fever is most common in developing countries where there is poor sanitation and limited access to clean water. Children and the elderly are thought to be most at risk due to their immunocompromised states.

The symptoms of typhoid fever include, but are not limited to:

  • High temperature
  • Head and muscle aches
  • Constipation or diarrhoea
  • Exhaustion
  • Stomach Pain

You should seek medical attention if you experience any of the symptoms for typhoid fever. With treatment, this disease will quickly improve within three to five days. If it isn’t treated, serious complications can develop.


Cholera is an acute diarrhoeal infection caused by the Vibrio cholerae bacterium. It is most common in developing countries and areas that have inadequate environmental management.

Infection occurs through ingestion of food and drink contaminated with the bacterium. If exposed to the bacterium, cockroaches can spread the organism through their faeces and vomit, contaminating surfaces and food.

Researchers from the World Health Organization have estimated that worldwide there are roughly 1.4 million to 4.3 million cases of cholera per year resulting in 28,000 to 142,000 deaths.

Around 80% of people infected with cholera do not develop any symptoms, although the bacterium is present in their faeces for 1-10 days after infection. Among the small percentage who do develop symptoms, 80% have mild to moderate symptoms with around 20% developing acute watery diarrhoea resulting in severe dehydration.


Dysentery is a type of gastroenteritis that results in diarrhoea with blood. Generally, most people suffer from mild symptoms and recover within a week or so without medical attention.

There are two types of dysentery. They are:

  • Bacillary dysentery — Sometimes referred to as shigellosis. It is caused by the Shigella bacteria.
  • Amoebic dysentery — Is caused by a single-celled parasite called Entamoeba. It is usually found in tropical areas.

Dysentery is usually spread through poor hand hygiene and consuming contaminated food and drink. Symptoms are diarrhoea containing blood and mucus, painful stomach cramps, nausea and vomiting, and a high temperature.


Cockroaches, along with other insects, are suspected of being carriers of the bacillus Mycobacterium leprae which causes the disease leprosy.

Cockroaches are believed to spread the disease through their faeces. Whilst the bacteria are not highly infectious, if left untreated, it can cause permanent damage to the skin, nerves, eyes and skin which can lead to disfigurement and deformities.

Leprosy has an incubation period of around five years but symptoms may take as long as 20 years to appear. Treatment is possible using multidrug therapy (MDT).


Although it is regarded as a rodent-borne disease, cockroaches are also suspected of spreading the Yersinia pestis bacterium which causes plague.

Common symptoms of plague include, but are not limited to:

  • Swollen and painful lymph nodes.
  • Chills
  • Muscle cramps
  • High fever

People infected by the plague need to receive urgent treatment and should be given antibiotics 24 hours after infection to avoid severe consequences.

It is estimated that the bubonic plague was responsible for around 50 million deaths in the fourteenth century. According to the WHO, from 2010 to 2015 there were 3248 cases reported worldwide including 584 deaths.

A few cases of plague are reported in the US each year (1-17 annually since 2000) and central Asia, though the most endemic countries recently have been the Democratic Republic of the Congo, Madagascar, and Peru.

Other diseases spread by cockroaches

Other pathogenic bacteria that cockroaches spread include:

Staphylococcus aureus
Staphylococcus aureus is a gram-positive cocci bacterium. This organism is generally harmless, but can cause serious infections.

Infection can occur in many forms ranging from minor skin infections, such as boils, to infections of the blood, lungs and heart. Cockroaches are known to carry the bacterium on their exoskeletons or in their digestive tracts.

Like Staphylococcus aureusStreptococcus infections come in many different forms, from mild throat infections to life-threatening infections of the blood or organs.

Cockroaches and asthma

Cockroach allergy was first reported in 1943. It was discovered when patients developed a rash after cockroaches crawled on their skin.

Cockroaches can trigger asthma because they certain proteins in their bodies which can be an allergen for certain people. When tiny particles from cockroach bodies are spread through the air in buildings, these proteins are inhaled and an asthma attack can be triggered in sensitive people.

The American College of Allergy, Asthma & Immunology reports that the saliva, faeces and shed skin of cockroaches can trigger both asthma and other allergic responses.

The National Pest Management Association has carried out studies around cockroach allergens and residential homes. Its studies show that around 63% of homes in the US contain allergens. This statistic rises for homes in urban areas (between 78% and 98%).

It is estimated by the WHO that 300 million people worldwide suffer from asthma. It has been discovered that frequent hospital visits of children living in cities suffering from asthma can often be as a result to contact with cockroaches. Around 23-60% of people with asthma are sensitive to cockroach allergens.

How do cockroaches spread diseases?

Cockroaches can spread diseases through:

  • Droppings
  • Vomit
  • Mechanical transfer from their feet and other body parts

Cockroach droppings

Due to their unsanitary eating habits, cockroaches can pass harmful pathogens through their droppings. When a cockroach feasts on something contaminated, such as a raw piece of chicken or animal faeces, the organism will enter, and may lay dormant in their digestive system. The pathogen will then be excreted in cockroach droppings and will contaminate surfaces and food.

Cockroach saliva

Cockroach saliva is also responsible for spreading a range of diseases. Similar to droppings, saliva can harbour pathogens accumulated from eating contaminated items.

Mechanical transfer

Cockroaches can be found living in sewers, cesspits, drains and rubbish bins where they come into contact with a range of organisms, such as bacteria and viruses, which can become attached to cockroaches’ bodies.

The legs of a cockroach, for example, have spines that are sensitive to touch and provide a very large surface area to pick up pathogens. Anything a cockroach touches or rubs past may then become contaminated.

How can you catch a disease from a cockroach?

How can you catch a disease from a cockroach

You can catch a disease from a cockroach in a range of different ways. However, for the most part, cockroach diseases are caught by coming into contact with items that a cockroach has contaminated.

Eating and drinking contaminated food

The most common form of transmission of a disease from a cockroach is from eating or drinking anything it has contaminated. This can occur from infectious particles it has picked up on the outside of its body (mechanical transmission), or its saliva or faeces.

Transmission can either be through consuming food or drink directly contaminated by cockroaches, or by eating or drinking something that has been made using contaminated cooking utensils, cutlery or crockery, or has touched contaminated surfaces.

How to prevent cockroaches spreading diseases

How can you catch a disease from a cockroach

Inhaling contaminated air

If the air supply is contaminated with proteins from cockroach faeces, vomit or shed skin and this is inhaled by people suffering from asthma, an attack can be triggered.

Touching contaminated items

Touching items contaminated with a organism deposited by cockroaches is also a route through which transmission can occur. Touching an item which has been contaminated then touching your eyes, nose, mouth or an open wound can result in the pathogen entering the body and infection setting in.

The most effective way to prevent to cockroaches spreading diseases in your home or business is to reduce to possibility of these crawling insects entering your property. 

You can prevent diseases spread by cockroaches by:

  • Through cleaning practices
  • Following proper hand hygiene
  • Building maintenance, such as sealing cracks and gaps where they can hide


Cleaning is one of the most effective methods for preventing cockroaches. Not only will it make your property less appealing to them in the first place, it will also get rid of any bacteria or virus they’ve spread.

It’s advised that you clean floors, worksurfaces, sinks and drains on a regularly basis and cooking utensils, cutlery and crockery before and after use. Removing any possible food sources, such as dropped food, grease behind ovens and pet faeces, is also a good idea.

For businesses operating within the food industry, complying with the proper food safety regulations in regards to cleaning can help reduce the risk of diseases carried by cockroaches being spread.

Hand hygiene

Washing your hands on a regular basis can assist in reducing the risk of cockroach-borne diseases. Wash your hands with soap and warm water on a regular basis to help eliminate any bacteria, germs or viruses which can cause the diseases spread by cockroaches.

It is important that you wash your hands:

  • Before, during and after preparing food.
  • After using the washroom.
  • Before and after eating.
  • After handling any material which could transfer germs.

Seal cracks and gaps

Sealing cracks or gaps in and around your property helps to reduce the number of entry points for cockroaches. This in turn reduces their potential to transmit organisms which cause diseases through your home or businesses.

It’s a good idea to regularly inspect your property to make sure there are no entry points, and seal them with expanding foam and other materials if necessary. It is also advised that you regularly inspect and repair damaged drains and pipes.

Professional cockroach control

The best way to reduce the risk of cockroach diseases is to enlist the help of a professional pest control professional (exterminator).

With over 90 years of experience, Rentokil provide a range of services and solutions to both prevent and exterminate cockroaches, which will reduce the potential for these crawling insects to spread diseases in your property.

Get professional advice how to control cockroaches


  1. Vector Control: Methods for use by individuals and communities. 1st ed. Geneva: World Health Organization, pp.288 to 301. (link accessed 4 October 2016)
  2. Foodpoisonjournal.com. Cockroaches and Foodborne Illness. (link accessed 4 October 2016)
  3. NHS UK. Typhoid fever - NHS Choices. (link, accessed 4 October 2016)
  4. World Health Organization. Cholera. (link, accessed 4 October 2016)
  5. NHS UK. Dysentery - NHS Choices. (link, accessed 6 October 2016)
  6. World Health Organization. Leprosy. (link, accessed 6 October 2016)
  7. Centre for Disease Control and Prevention. E.coli. (link, accessed 6 October 2016)
  8. American College of Allergy, Asthma & Immunology. Cockroach Allergies. (link)
  9. Umunnabuike, AC, & Irokanulo, EA. (1986) Isolation of Campylobacter subsp. jejuni from Oriental and American cockroaches caught in kitchens and poultry houses in Vom, Nigeria. Int. J. Zoonoses, 13(3), pp.180-6.
  10. Centre for Disease Control and Prevention. Listeriosis. (link, accessed 6 October 2016)
  11. World Health Organization. The Plague. (link, accessed 31 October 2016)

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