What are the common diseases caused by pests? Pests can affect human health, animals, plants and crops in several ways. Some pests carry bacteria, viruses, parasites and other pathogens, while others contaminate food, trigger allergies or help plant diseases spread. Understanding the signs, risks and methods of prevention can make it easier to take action before an infestation causes serious problems.
What Diseases Can Pests Cause or Spread?
Pests can contribute to a wide range of diseases and infections. Rodents, ticks, mosquitoes, fleas, lice, cockroaches and other insects may carry pathogens or create conditions that increase the risk of illness. Some diseases pests spread are passed through bites, while others are linked to contaminated food, water, urine, faeces or surfaces.
The level of risk depends on the pest species, the pathogens present, the level of exposure and the health of the person affected. In extreme cases, pest-related infections can cause severe illness or death, although many of the diseases discussed on this website are uncommon in the UK.
Pests can also have a major impact outside the home. Plant pests attack garden plants, trees, fruit and commercial crops. Some insects feed directly on leaves and roots, while others spread bacteria, fungi and viruses between susceptible plants. Effective pest and disease control is therefore important for both public health and agriculture.
Health Problems Linked to Common Pests
Common pests can affect health in several ways. Vector-borne diseases are infections transmitted by organisms such as ticks, mosquitoes and fleas. Examples include Lyme disease, malaria and plague. Rodents may also spread infections through urine, faeces and contaminated food.
Indoor pests can cause different problems. Cockroaches, for example, may contaminate food and surfaces with bacteria. Their body parts and excrement can also contribute to asthma and allergic reactions in susceptible people. Bed bugs do not have an established role as important disease vectors, but their bites can cause skin irritation, itching and loss of sleep.
Good hygiene, suitable food storage and prompt pest control can reduce the risk. However, pesticides and other chemicals should always be used correctly. Depending on the pest and the area affected, physical control, proofing, traps or professional treatment may be more suitable.
Rodents and the Diseases They Can Spread
Rodents can reproduce quickly when they have access to food, water and shelter. Human environments can provide an ideal natural habitat substitute for rats and mice, which is why these pests are often found near homes, food premises, farms and waste storage areas.
Rodents can carry various diseases directly or indirectly. Transmission may happen through bites, contaminated food, urine, faeces or parasites living on the animal. Fleas, lice, ticks and mites associated with rodents can also carry pathogens.
The presence of rodents does not mean that disease transmission will occur. However, an infestation should be managed because rodents can contaminate food, damage buildings and create a potential health risk.
Leptospirosis and Weil's Disease
Leptospirosis is a bacterial infection caused by Leptospira bacteria. People can become infected after exposure to water, soil or other material contaminated with urine from infected animals. Rats are one possible source, although other animals can also carry the bacteria.
Symptoms can include fever, headache, muscle pain, nausea and tiredness. In severe cases, the infection can affect the liver, kidneys, brain or lungs. A severe form of leptospirosis is sometimes called Weil's disease.
According to figures published for England, 115 confirmed or probable cases of leptospirosis were reported in 2025, compared with 156 in 2024. This shows that the disease remains relatively uncommon, but prevention is still important for people who may be exposed to contaminated water or animal urine.
Leptospirosis can be treated with antibiotics. Anyone who develops concerning symptoms after possible exposure should seek medical advice rather than trying to identify or treat the infection themselves.
Salmonellosis
Salmonellosis is caused by Salmonella bacteria. Rodents may carry Salmonella and can contaminate food preparation areas, stored ingredients and water through their faeces. Infection can cause diarrhoea, stomach pain, fever, nausea and vomiting.
Cleaning contaminated areas safely and preventing rodents from reaching food are important parts of control. Food that may have been contaminated should not be eaten. Good hygiene and suitable storage can also help prevent infections.
Rat-Bite Fever
Rat-bite fever is a bacterial disease associated with infected rodents. Infection may follow a bite or scratch, although bacteria may also be present in rodent secretions.
Symptoms can include fever, vomiting, muscle pain, joint pain, headache and a rash. Antibiotics are normally used for treatment. A bite from a rat or another potentially infected animal should be cleaned thoroughly, and medical advice may be needed depending on the severity of the injury.
Hantavirus Infections
Hantaviruses are a group of viruses carried by certain rodents. Infection can occur when people are exposed to infected rodent urine, faeces or saliva, particularly if contaminated material becomes airborne.
Different hantaviruses cause different diseases around the world. Symptoms can begin with fever and flu-like illness, while some infections can become much more serious. The exact risk varies greatly between countries and rodent species.
Plague
Plague is caused by the bacterium Yersinia pestis. The bacteria can circulate between rodents and fleas, with infected fleas able to transmit the infection to humans and other animals.
Plague caused devastating outbreaks in earlier periods of history, but modern diagnosis and antibiotics have changed its impact. The disease is now extremely rare in Britain. Nevertheless, it remains present in parts of the world.
Tularaemia and Other Rodent-Associated Infections
Tularaemia is caused by Francisella tularensis bacteria. It can affect a range of mammals and may also be carried by ticks and other biting arthropods. Human infections are uncommon in the UK.
Rodents may also be linked with diseases caused by Bartonella bacteria, arenaviruses and certain parasites. The range of diseases present varies considerably between countries, climates and animal species, so the risk from rodents should be considered in its local context.
Ticks and Lyme Disease
Ticks are small parasites that feed on the blood of animals and people. They may be found in woodland, grassland, heathland, parks and gardens. Not every tick carries disease, but some can spread pathogens while feeding.
Lyme disease is the most common locally acquired vector-borne infection reported in England. In 2025, there were 1,168 laboratory-confirmed acute cases in England, compared with 959 in 2024. The true number of infections is likely to be higher because some cases can be diagnosed from their symptoms without laboratory testing.
A common symptom of early Lyme disease is a circular or oval skin rash that can gradually spread from the area of the bite. It does not always appear. Other symptoms may include fever, headache, tiredness, muscle pain and joint pain.
If Lyme disease is not treated, some people can develop problems affecting the joints, nerves or heart. Antibiotics are used for treatment, and early diagnosis generally leads to good results.
How to Reduce the Risk of Tick Bites
Ticks can be active throughout the year, although activity often increases during warmer months. In England, reports of tick bites typically increase in late spring and peak around June.
When walking through long grass, woodland or other areas where ticks may be present, covering exposed skin can reduce contact. After spending time outside, check clothing, skin and pets for ticks. Pay particular attention to warm or hidden areas of the body.
If a tick is found, it should be removed as soon as possible with a suitable tick-removal tool or fine-tipped tweezers. Avoid squeezing the body of the tick. Check the affected area over the following days and weeks for signs of Lyme disease.
Tick-Borne Encephalitis
Tick-borne encephalitis is a viral infection that can affect the central nervous system and, in some cases, cause meningitis or inflammation of the brain. Many infections are asymptomatic, while others begin with symptoms such as fever, headache and muscle pain.
Locally acquired infection remains very rare in Britain. Two unrelated probable locally acquired cases of the tick-borne encephalitis complex were identified during 2025, bringing the total number of locally acquired human cases recorded since the virus was first identified in the UK in 2019 to six.
The finding does not mean that most UK ticks carry the virus. The overall risk remains low, but continued surveillance is important as environmental and climate changes can affect the range and activity of ticks.
Diseases Spread by Mosquitoes
Mosquitoes are among the most important disease-carrying insects globally. Different mosquito species live in different habitats, feed at different times and carry different pathogens. Climate, high temperatures, rainfall and access to standing water can all affect mosquito populations.
Mosquito-borne diseases include malaria, dengue, chikungunya, yellow fever and several forms of encephalitis. Most of these diseases are associated with warmer countries and are not normally acquired in the UK.
Climate change may alter the areas where some mosquito species can survive and reproduce. Changes are already being monitored across Europe, where invasive mosquitoes capable of transmitting diseases such as dengue and chikungunya have become established in a number of countries.
Malaria
Malaria is not a virus. It is a potentially life-threatening disease caused by Plasmodium parasites and spread to people through the bites of infected female Anopheles mosquitoes.
The disease remains a major global health problem. The World Health Organization estimated that there were 282 million malaria cases and 610,000 deaths worldwide in 2024. Around 95% of those deaths occurred in the African Region.
Malaria commonly causes fever, chills and headaches. Severe disease can cause breathing difficulties, seizures, confusion and other serious problems. Treatment is available, and prevention is particularly important for people travelling to areas where malaria is present.
Chikungunya
Chikungunya is a viral disease spread mainly by infected mosquitoes. Common symptoms include sudden fever and severe joint pain. Headache, muscle pain, tiredness and a rash can also occur.
Most people recover, but joint pain can continue for a long period in some cases. Mosquito species capable of spreading chikungunya have expanded their range in parts of Europe, making surveillance increasingly important.
Fleas, Lice and Other Biting Insects
Fleas and lice can cause skin irritation directly through their bites. Certain species can also carry pathogens. Rat fleas are historically associated with plague, while some human lice can spread bacterial diseases including epidemic typhus, trench fever and relapsing fever.
The health risk depends heavily on the species involved and the location. Hygiene, pest management and avoiding contact with infested animals can help reduce exposure.
Bed Bugs
Bed bugs are small insects that feed on human blood. They are usually most active at night and often hide in mattresses, furniture, cracks and other sheltered places during the day.
Bed bug bites can cause red marks, itching and swelling. Some people have a stronger skin reaction, while others show almost no visible signs. At present, bed bugs are not regarded as important transmitters of infectious diseases to humans.
An infestation can still have a considerable impact on health and wellbeing because repeated bites may disturb sleep and cause stress. Bed bugs can also be difficult to eliminate without a carefully managed treatment process.
Cockroaches
Cockroaches are common pests in warm indoor environments where they have access to food and water. They may pick up bacteria from waste, drains and contaminated surfaces and move them into kitchens and food storage areas.
Cockroach droppings, shed skins and other material may also trigger allergies and asthma in susceptible people. Prevention includes removing food sources, fixing water leaks, sealing holes and cracks and keeping food preparation areas clean.
Flies
Flies can move between waste, animal material and food. In doing so, some species may mechanically transfer bacteria and other pathogens onto food or surfaces. Good waste management and food hygiene can therefore reduce problems caused by flies.
In other parts of the world, biting flies can transmit more serious diseases. For example, certain black flies can spread onchocerciasis, while some tsetse flies can transmit African trypanosomiasis.
Pests and Diseases Affecting Plants
Pests and diseases are also a major concern in the garden, commercial nurseries and agriculture. Plant pests can damage leaves, stems, fruit and roots directly, while some insects spread pathogens from one plant to another.
It is important to distinguish between pest damage and plant diseases. Aphids, beetles, moths, thrips, mites and nematodes may attack plants directly, while fungal diseases, bacterial diseases and viruses are caused by pathogens. However, pests and diseases often interact, which is why correct identification is essential before control begins.
Pest damage can weaken plants, reduce growth and lower crop yields. In severe infestations, pests can cause significant damage to crops and trees and may contribute to the death of vulnerable plants.
Aphids and the Diseases They Spread
Aphids are among the most common pests found on garden plants and crops. They feed by taking sap from leaves and young growth. Large populations of aphids can cause distorted leaves, poor growth and a reduction in the nutrients available to developing parts of the plant.
Aphids can also spread plant viruses. As the insects move from an infected host to healthy plants, pathogens may be carried between them. This is one reason why controlling aphids can form an important part of disease control in susceptible crops.
Before using pesticides, gardeners can check whether natural predators are already controlling the population. Ladybirds, lacewings and other insects feed on aphids and can reduce their numbers naturally.
Mites, Thrips and Other Insects
Mites can feed on leaves and cause pale markings, discolouration and reduced plant growth. Some species become particularly active during warm, dry conditions. The undersides of leaves should be checked because pests and eggs can be difficult to see from above.
Thrips are small insects that feed on plant tissues and can damage flowers, fruit and leaves. Some thrips species also transmit plant viruses. Beetles and their larvae may chew holes in leaves, stems or roots, while moths and butterflies can produce caterpillars that feed heavily on crops.
Not all insects found in a garden are pests. Many butterflies are useful pollinators, and a large number of beetles and other insects contribute to a healthy environment. Correctly identifying the species before treatment helps avoid killing beneficial insects unnecessarily.
Nematodes and Root Damage
Nematodes are microscopic roundworms found naturally in soil. Many species are harmless or beneficial, but certain plant-parasitic nematodes attack roots and can interfere with the plant's ability to absorb water and nutrients.
Damage to the root system can result in slow growth, yellow leaves and poor crop production. Some affected plants may appear to be short of water or nutrients even when suitable growing conditions are present.
Management depends on the nematode species, the crops involved and the severity of the problem. Crop rotation, resistant varieties and healthy soil management can help in some situations.
Powdery Mildew
Powdery mildew is one of the most familiar fungal diseases affecting garden plants and crops. A common symptom is a white or grey powder-like coating on the leaves, stems or flowers of affected plants.
Different fungi cause powdery mildew on different host plants. The disease can reduce photosynthesis, weaken growth and affect fruit or flower production. Warm conditions and poor air movement can encourage some forms of powdery mildew.
Removing heavily affected plant material, improving air circulation and choosing less susceptible varieties can help with prevention. Where products are used for control, always check that they are suitable for the plant and disease being treated.
Downy Mildew
Downy mildew describes a group of diseases caused by fungus-like organisms. Symptoms vary between plants, but affected leaves may develop yellow, brown or purple patches. A grey or white growth can sometimes be found on the undersides of leaves.
Unlike many forms of powdery mildew, downy mildew often develops quickly when leaves remain wet and conditions are cool or humid. Watering plants near the base rather than over the foliage and improving air movement may help reduce the risk.
Dead or badly infected leaves should be removed where appropriate. Garden tools and equipment should also be kept clean to reduce the chance of spreading pathogens between plants.
Bacterial and Fungal Diseases in Crops
Bacterial diseases and fungal diseases can affect a wide range of crops, trees and garden plants. Signs may include leaf spots, rotting fruit, cankers, wilting, unusual growth or changes in leaf colour.
Problems can become harder to manage once pathogens are well established. Prevention can include using healthy plants from trusted nurseries, allowing suitable space between plants, avoiding unnecessary damage to roots and stems and keeping tools clean.
Changes in climate can also influence plant health. Warmer conditions, changes in rainfall and longer growing seasons may affect pest generations, the establishment of introduced species and the period during which pests and diseases remain active.
How Climate Change Can Affect Pests and Diseases
Climate change can alter where pests and disease-carrying species are able to survive. Increasing temperatures may allow some insects to remain active for longer periods or complete more generations within a year.
Climate also affects natural habitats, water availability, plants and the animals on which some pests feed. As these conditions change, the geographical range of certain pests and pathogens can change too.
The UK Health Security Agency has reported an increasing distribution of ticks across the UK, although tick numbers vary from year to year. Weather, habitat changes and host populations all contribute to these patterns.
Climate change does not mean every pest-borne disease will become common in Britain. Whether a disease becomes established depends on many factors, including whether a suitable vector and host are present and whether temperatures allow the pathogen to develop and spread.
How to Identify a Pest or Disease Problem
Early identification can make pest problems easier to manage. In a building, signs may include droppings, gnaw marks, nesting material, unusual smells, damaged food packaging or sightings of live or dead pests.
In the garden, check plants regularly for holes, distorted leaves, insects, larvae, mites, changes in colour or unusual growth. Look at the undersides of leaves as well as the stems, fruit, soil and root area.
It is important to identify whether the problem is being caused by pests, diseases, poor growing conditions or a combination of factors. Applying chemicals without identifying the cause can be ineffective and may harm beneficial species.
If a problem cannot be identified confidently, use information from a reliable website or seek advice from a suitable specialist before taking action.
How to Prevent Pest-Related Health Problems
Prevention is usually easier than dealing with a large infestation. In homes and businesses, store food securely, clear waste regularly and prevent pests from reaching sources of water and shelter. Cracks and other possible entry points should be repaired where practical.
Where rodents are present, avoid direct contact with urine, faeces or nesting materials. Contaminated areas should be cleaned using an appropriate method rather than dry sweeping material that could contain harmful particles.
People working outside should be aware of ticks and other biting insects, particularly around woodland, long grass and areas where animals are present. Checking the skin after outdoor activity can help identify ticks early.
In a garden, healthy plants, suitable watering and good soil conditions can make crops less susceptible to attack. Natural predators can also help keep certain common pests under control.
When Should Professional Pest Control Be Used?
A small pest problem can sometimes be managed through cleaning, proofing or removing food and water sources. However, professional control may be appropriate when an infestation is large, keeps returning or creates a risk to health, food safety or property.
A pest specialist can identify the species, assess how it is entering the site and decide which control method is appropriate. This can reduce unnecessary pesticide use and help address the base cause of the infestation rather than only removing pests that are currently visible.
Treatment may involve several visits depending on the pest and its life cycle. Some insects have eggs or larvae that survive an initial treatment, meaning further action may be required before the infestation is eliminated.
When to Seek Medical Advice
Most encounters with pests do not lead to serious diseases. However, seek appropriate medical advice if you become unwell following a rodent bite, tick bite, possible contact with contaminated animal urine or another significant exposure.
Symptoms such as a high fever, severe headache, breathing problems, spreading skin changes, unusual weakness or neurological problems should not be ignored. Tell the healthcare professional about any recent pest, animal or insect exposure, as this information can help with diagnosis.
People returning from countries where malaria is present should treat a fever seriously and provide details of their recent travel. Malaria can become severe quickly if diagnosis and treatment are delayed.
Are Diseases Caused by Pests Common in the UK?
Many of the world's serious pest and vector-borne diseases are uncommon or are not normally acquired in the UK. Malaria, for example, is mainly a risk for people travelling to countries where the disease is present rather than from local mosquitoes in Britain.
Lyme disease is more relevant locally. England recorded 1,168 laboratory-confirmed acute cases during 2025, making it the country's most common locally acquired vector-borne infection.
Leptospirosis is much less common, with 115 confirmed or probable cases reported in England during 2025. Locally acquired tick-borne encephalitis is rarer still.
These figures provide useful context. Pests can carry diseases, but the presence of a pest does not automatically mean that a person will become infected. The actual risk depends on the pest, pathogen, type of contact and location.
Why Pest and Disease Control Matters
Pests can cause problems ranging from food contamination and structural damage to bites, allergies and infections. They can also have an important impact on plants, trees, fruit and crops.
Good pest and disease control begins with identifying the cause of the problem. Removing food sources, improving hygiene, blocking entry points and maintaining a healthy garden environment may prevent many infestations before pesticides become necessary.
For plant pests and diseases, regular checks can help detect changes early. The sooner aphids, mites, nematodes, powdery mildew, downy mildew or other problems are found, the easier they may be to manage before they spread or cause significant damage.
For pests that could affect human health, the same principle applies. Identify the problem, reduce exposure and use an effective form of control. Where there is a serious infestation, repeated problems or uncertainty about the species present, professional help may be the safest way forward.
Are you looking for pest control services in Portsmouth, Southampton, Basingstoke or Hampshire? Use the links on this site to find information about local pest control services and the options available for dealing with an infestation.
