cockroaches on plate
Photo by Roger Brown on

In one of our articles on home pests; we talked about cockroaches and effective natural ways of getting rid of them and the main reason behind getting rid of them is because they spread diseases; they habour pathogens and their eggs in their gut and this raises the risk of food infections and other diseases when man eats food contaminated by cockroaches.

There are over 4000 species of roaches and three major species plagues humanity the most and they are Periplaneta Americana, Blattella Germanica and Blattella orientalis. 

These three species feed on anything, from sweet and starchy items like sweets, cardboard and book binding to even the dead bodies of their fellow roaches; they also eat human feaces, septum, toe nails and bodily residues on surgical swabs.

Due to their dietary choices and dirty habitats which makes it easy for them to accumulate a range different microbes; roaches are source of infectious pathogens and their contamination of food items or other household properties have direct consequences on humans because it leads to diseases and health complications.

Roaches are also carriers of bacteria, viruses, fungi and parasites; bacteria and viruses settles in the crevices and cracks between the thorax and the head and start multiplying from there, microbes are also present on the hairs and they are also consumed by the cockroaches which will enable the microbes get into the alimentary canal and multiply there.

A study found out that in the gut of a cockroach; the bacterium Pseudomonas aeruginosa increased multiple folds over the course of 114 days; over 30 species of bacteria have been found on the cuticle and in the guts of roaches, most of these bacteria cause serious medical conditions like urinary tract infections, dysentery, diarrhea, pneumonia, cholera, polio, septicemia and wound infections.

Another study found out that roaches had up to 14 million microbes on their bodies and 7 million microbes in their fecal droppings. Even poliomyelitis, the virus that causes polio has been isolated from the guts of roaches and they even habour antibiotic resistant bacteria.

Note that roaches are not vectors of diseases, they are only reservoirs; a vector is an organism that spreads diseases like mosquitoes which spreads malaria, during a blood meal the mosquito will put its proboscis in the skin to get blood and at the same time inject plasmodium parasites which are the organisms that cause malaria.

Meanwhile cockroaches don’t inflict any disease on man; they simply contaminate things in the home and this is how they spread diseases. Entomologists call this “mechanical transmission” which is the indirect transmission of diseases to humans.

Historical evidences and studies that prove roaches are carriers of diseases

Many documented cases of outbreaks in the past pointed roaches as the culprits; even though their role was indirect, it was prominent in the transmission of diseases. These histories and studies prove that play roles in spreading diseases both in the home and hospitals.

In the late 1970s, a country in Northern Ireland experienced food poisoning; 15 food handlers in different restaurants fell ill to dysentery caused by Shigella, a bacterium.

It was later discovered that these restaurants had serious cockroach infestations, they were seen particularly in the dining areas and kitchen, some of the roaches were trapped and the content of their stomach showed the presence of Shigella dysenteriae.

In the late 1950s, these arthropods were also suspected to be the major cause of hepatitis A outbreak in a Los Angeles housing project; from 1956 to 1959, the rate of hepatitis was increasing in this area until a full scale cockroach control program was carried out using a newly developed insecticide and the epidemic stopped.

The insecticide used was the industrial silica aerogel Dri-Die 67; two years after this cleaning, the rate of hepatitis A dropped to 0.0% and that was when the roaches were pinpointed as the source of the epidemic.

In 1943, a study was conducted in Italy and it was discovered that typhoid patients had roaches in their homes that had Salmonella typhi, the microbe that causes typhoid fever.

Also in 1950; the same typhoid causing organism was found in roaches infesting a Belgian hospital’s children ward undergoing an epidemic of gastroenteritis. Also in Ethiopia and South Africa, an outbreak of Klebsiella pneumoniae in neonatal units was tied to the infestation of roaches.

In 2012, a study was conducted in Ethiopia using trapped roaches in a neonatal intensive care unit and they found many antibiotic resistant bacteria residing in the roaches; they were resistant to powerful antibiotics like ampicillin, augmentin, tetracycline, chloramphenicol, amoxicillin, doxycycline, and ciprofloxacin.

Also in South Korea, a study conducted proved that roaches trapped in homes located 3 miles from the hospitals haboured bacteria that were resistant to commonly used antibiotics.

In this article, we will be looking at some of the parasites spread by cockroaches and the diseases this parasites cause.

First, we will be looking at bacteria carried by roaches and it has been estimated that at least 32 species of bacteria have been isolated from domestic roaches. 174 bacteria were isolated from 39 German roaches specimen in hospital environment.

Some of the bacteria isolated from roaches are:

Aeromonas: This bacteria cause diarrhea, wound infections and other infections.
Alcaligens faecalis: This cause urinary tract infection, gastroenteritis
Bacillus cerrus: Cause food poisoning
Bacillus subtilis: Cause conjunctivitis
Campylobacter jejuni: Cause enteritis
Clostridum perfringens: They cause gas gangrene and food poisoning
Enterobacter: Cause bacteremia (which is a medical condition characterized by the temporary presence of bacteria in the blood, this is commonly followed by the development of various infections including abscesses).
Enterococcus: This species cause urinary tract and wound infections and they are antibiotic resistant.
Escherichia coli: Causes diarrhea and wound infections.
Helicobacter hepaticus: Cause inflammation of the gallbladder (cholecystitis), gallbladder stones and gallbladder cancer.
Klebsiella species: Cause pneumonia and urinary tract infections.
Mycobacterium leprae: Causes leprosy.
Morganella morganii: Causes wound infections.
Nocardia species: Cause actinomycetoma (a medical condition characterized by chronic infection of the skin and underlying tissues).
Oligella urethralis: This species may cause bacteremia, septic arthritis that mimics gonococcal arthritis, and peritonitis.
Pantoea species, Proteus rettgeri and Proteus vulgaris cause wound infections.
Proteus mirabilis causes wound infections and gastroenteritis.
Pseudomonas species cause respiratory infections and gastroenteritis.
Salmonella: Causes gastroenteritis and food poisoning
Salmonella typhi causes typhoid.
Salmonella pyogenes causes pneumonia.
Serratia species cause food poisoning.
Shigella dysenteriae causes dysentery.
Sphyngobacterium species cause sepsis (a medical condition characterized by the presence of pathogenic microorganisms or their toxins in the blood or other tissues).
Staphylococcus aureus causes wound infections, skin infections and infections of internal organ.
Staphylococcus epidermalis causes wound infections.
Streptococcus faecalis and other species cause pneumonia.
Chlamydia trachomatis causes trachoma which is an infectious disease of the eye, it is the leading cause of blindness the world caused by infection. Around the globe, it is estimated that 41 million people are suffering from this active infection and nearly 8 million people are visually impaired because of this disease.
Yersinia pestis (isolated from oriental cockroach), causes plague. Apart from bacteria, roaches also carry fungi, worms, protozoa and virus and here are few of them.
Worms or helminthes: Roaches have been found to habour the eggs of seven species of helminthes and the common ones are hookworm, giant human roundworm, pinworm, tapeworm and whipworm and they also habour helminthes.
Fungi and viruses: Roaches habour at least 17 fungal species that are capable of causing diseases in humans; they also habour two strains of poliomyelitis virus, the causal organism of polio.
Protozoa: They are carriers of three protozoan species; they are the protozoan Toxoplasma gondii which causes toxoplasmosis and Lophomonas blattarum a species of the multi flagellated protozoa; the cysts of these protozoa can enter the human body by ingestion and inhalation and this will lead to bronchopulmonary infection also known as bronchopulmonary lophomoniasis.

It will also cause respiratory symptoms like fever, dizziness, ear pain, progressive headache, green and sticky nasal discharge and sneezing. Infections caused by this parasite are resistant to antibiotics and they can also cause other infections like urinary and intrauterine infections.

From the above microorganism mentioned above, we will be looking at the most common diseases this organisms cause.

Common diseases spread by cockroaches

The World Health Organization stated that ““Cockroaches are not usually the most important cause of a disease, but like houseflies, they play a supplementary role in the spread of some diseases” and we will be looking at the most common diseases spread by cockroaches.


Roaches habour salmonella bacteria which is the microbe behind salmonellosis, a disease that shares similar symptoms with food poisoning; this bacteria can be in their digestive system for months and they deposit it through their vomit and faeces.

When a human eats food contaminated by a cockroach having this bacteria; he or she gets infected and symptoms starts to show 12 to 72 hours later. The symptoms include fever, diarrhea and vomiting.


Roaches are carriers of pathogens that cause the two forms of dysentery; they carry the Shigella bacterium that causes bacillary dysentery which is also known as Shigellosis and a single celled parasite called Entamoeba that causes amoebic dysentery.

This disease is gotten through food and drinks contaminated with these organisms and the signs and symptoms are diarrhea containing blood and mucus, nausea and vomiting, high temperature and painful stomach cramps.


It is believed that roaches habour and spread Yersinia pestis which is a bacterium that causes the bubonic plague that is characterized by swollen and painful lymph nodes, chills, high temperature and muscle cramps. Treatment is needed immediately to avoid severe consequences and death.

E.coli Infections

Roaches habour E.coli and they spread them by contaminating food and drinks, they do this by mechanical transfer on their feet and exoskeleton; although most of them are harmless, some of them can cause serious food poisoning; when infected with E.coli, one experiences watery stool, abdominal cramping, fever, chills, nausea and muscle aches.


This acute diarrhoeal infection is caused by the vibrio bacterium which roaches spread by contaminating food, drinks and surfaces with their faeces and vomit and it can be very fatal if not treated immediately, it is also highly contagious.


Another microbe haboured by roaches in their gut and external surface is Campylobacter bacterium; this organism is behind the most common food borne bacterial infection in man; it occurs when humans take in food and drinks that have been contaminated by roaches carrying this microbe and its symptoms are bloody stool, cramps, abdominal pain and fever.

Typhoid fever

Roaches are good reservoirs of Salmonella typhi; the microbes that cause typhoid fever which is a highly infectious disease; they accumulate this bacteria by eating faeces contaminated with the bacteria.

After infection, symptoms like high temperature, head and muscle aches, constipation or diarrhea, exhaustion and stomach pain will begin to surface.


Roaches are faithful carriers of the bacterium Listeria monocytogenes which is behind this serious infection; it occurs when food and drinks contaminated with this bacterium is ingested, it is severe in people with weakened immune systems like pregnant women, the aged and new born babies.

Symptoms are muscle aches, diarrhea and fever but in severe cases headache, stiff neck, loss of balance, confusion and convulsion can set in. in pregnant women; it can lead to miscarriage, still birth or premature delivery.


Roaches carry the virus poliomyelitis that causes polio in their throat and intestinal tracts; they spread it through their faeces and oral secretions like saliva and vomitus, this deadly disease causes permanent paralysis in 1% of polio cases and result in the death of 5 to 10% of patients.

The legs are usually affected; when he virus enters the bloodstream, it goes straight to the central nervous system where it causes lots of havoc and damages, even those who recover from this deadly disease are at high risk of post=polio syndrome.


Roaches are carriers of the bacterium Mycobacterium leprae which is behind the cause of leprosy; they spread it by contaminating food and other things with their faeces.

When the bacteria is ingested, it has an incubation period of five to twenty years and if it is left untreated, it can give rise to permanent damage to the skin, nerves and eyes and this will lead to deformities and disfigurement.


These insects can trigger asthma in some people that are reactive to certain proteins on the bodies of these insects; these allergens or tiny particles from the bodies of the roaches spreads through the air and when inhaled by sensitive people, it can trigger an asthmatic attack.

Cockroach allergy

This was first reported in 1953 when patients developed a rash after roaches crawled on their skin; the saliva, faeces and shed skin of roaches can both trigger an allergy and asthmatic attack.


They habour lots of microbes that can lead to infections like wound infections, UTI, respiratory infections and meningitis; they are carriers of the enterococcus which cause meningitis and UTI.

How do roaches spread diseases?

These persistent pests spread diseases by three main ways:

Their droppings: Roaches droppings are full of harmful microbes that can cause a wide range of illnesses and diseases; when roaches feed on contaminated or dirty stuffs, the microbes enter them and lay dormant in their digestive system and some microbes multiply there. The roaches then excrete these pathogens or their eggs through their droppings or faeces on food or clean surfaces.

Their saliva or vomit: There are millions of disease causing microbes in the saliva and vomit of roaches and they contaminate food and water with their saliva and vomitus thereby spreading diseases.

Direct contact: Having direct contact with these pets puts one at risk of having roaches borne diseases; also coming in contact with their dead bodies,  shed skin and some of their body parts can also put one at  high risk of coming down with roaches borne diseases.

How do humans catch diseases from cockroaches?
There are many ways diseases are contracted from roaches but the main ways are:

Coming in contact with them: The skin and exoskeletons of roaches are loaded with deadly microbes; they even have allergens on their skin that can trigger asthmatic attack in some people. Some people also develop skin rash and other allergies when roaches touch their skin.

Inhaling contaminated air: If there are lots of roaches in the house or area and the air is polluted or contaminated with proteins or allergens from their skin; or from their faeces, vomit and shed skin, it can trigger allergic reactions and asthmatic attacks in sensitive people.

Touching contaminated items: Touching items that have been contaminated with microbes by roaches is one way many become infected with these diseases; most times when the contaminated items are touched, the hands are not washed and they are used to touch the body and sensitive parts like the eyes, nose and open wounds, some even eat without washing their hands. That is why regular washing of hand is encouraged especially before eating and after using the toilets.

Eating and drinking contaminated food: This is the most common way diseases are contracted from roaches; all food should be properly covered including cooking utensils, cutlery, crockery and the kitchen slab should be cleaned always to avoid contamination or touching contaminated surface.

How can we prevent roaches from spreading diseases?

Total elimination

This can be done by eliminating them from your home or business center; there are many ways to go about this but in the case of massive infestation it is advisable to call in professionals who specialize in destroying pests from the home.

This will demand you leaving your home or business venue for days so that the powerful chemicals used won’t have any side effect on you, your family members or your employees.

If the infestation is not massive but you see few in your home or workplace; it is advisable to act fast; eliminate them before they reproduce and beside only one roach is capable of contaminating food and drinks thereby causing diseases, you can decide to use chemicals or go natural.

Chemicals act fast and eliminate them but it also affects humans and cause lots of symptoms as side effects when inhaled; this makes it a not-too-good choice for the presence of few roaches in the home, especially when the home will not be vacated for the period of days the chemical is used.

There are also reports of roaches reappearing after the effect of the chemical dies down and this is why many prefer natural approaches in eliminating these unwanted flat mates.

There are lots of natural remedies that are very effecting in eliminating and repelling roaches without side effects even if you stayed in the room when you used them. We have already covered that on this blog and you can find the solutions here.

Other ways to prevent contracting diseases from roaches are:

Regular cleaning

Roaches hate a very neat, well lighted, dry, cool and spacious environment; they appreciate and feel welcomed in a dark, dirty, warm, moist and compressed or overcrowded environment.

This is one of the most effective method of eliminating and preventing roaches infestation; do not keep many things in your home especially if you are not using them on a daily basis and make sure that the home is regularly cleaned and every area visited regularly so that they have no safe hideout.

Also do not leave food crumbs on the floor, the kitchen should always be cleaned, foods should be properly covered and stored, utensils and cutleries should be washed before and after use and floors, work surfaces, sinks and drains should be cleaned on a regular basis.

Those in food business or food industries should comply with proper food safety regulations and their kitchens, stores, dining and other apartments to be cleaned regularly to reduce their numbers and also reduce the risk of food contamination by roaches.

Regular washing of hands

Making it a duty to wash your hands on a regular basis will help prevent or reduce the risk of cockroach borne diseases. You might not know when you have touched a contaminated surface or item; that is why it highly advised to wash your hands with soap and warm water regularly; this will eliminate any bacteria, viruses or germs that are spread by roaches.

Also make it a habit to wash your hands before, during and after preparing meals, before and after eating, after handling any material or touching any surface that can transfer germs and after using the toilet.