Unmasking the Hidden Threats: Squirrel Diseases in Urban and Wild Populations

Whether darting through city parks or scampering across woodland canopies, grey squirrels are a familiar sight. But behind their lively antics lies a hidden world of diseases that affect both squirrels and the ecosystems they inhabit.

From parasitic infestations to bacterial infections, these health threats can impact urban and rural environments—and occasionally pose risks to humans and pets.

Understanding these diseases is the first step to protecting your home, garden, and local wildlife. Here’s a clear, comprehensive guide to squirrel diseases, their effects, and how to manage grey squirrel issues responsibly with professional pest control.

Learn how to safeguard your environment with our in-depth look at Grey Squirrel Diseases, including symptoms to watch for, risks to native wildlife, and practical control measures.

Why Squirrel Diseases Matter

Grey squirrels (Sciurus carolinensis) are resilient, adaptable, and widespread across the UK. Yet they are susceptible to a range of health issues, including:

• Parasitic infestations like mange and intestinal worms

• Viral infections such as squirrelpox

• Bacterial diseases including leptospirosis and tularemia

• Fungal infections like ringworm

These conditions not only harm squirrels but can also disrupt ecosystems, affect native red squirrel populations, and, in rare cases, transmit zoonotic diseases to humans or pets.

Did you know?

A single grey squirrel can host over 40 parasites, and their nests may harbour pathogens linked to serious diseases.

Take action: Contact a BPCA-certified pest control professional like Apex Pest Control to inspect and address squirrel-related risks safely and legally.

Parasitic Infections: Hidden Threats Inside and Out

Internal Parasites: Worms in the Gut

Inside a squirrel’s digestive system, parasitic worms like roundworms (Ascaris spp.) and tapeworms (Taenia.
spp.) thrive, often undetected until symptoms appear. These parasites steal nutrients, causing:

• Weight loss and malnutrition

• Digestive issues or intestinal blockages

• Lethargy and reduced activity

Squirrels contract these worms by ingesting contaminated food or nesting materials tainted with faeces. Severe infestations can weaken squirrels, lowering their survival rates, especially in winter.

External Parasites: Fleas, Lice, and Mites

A squirrel’s dense fur is a haven for external parasites, including:

• Fleas (Ctenocephalides felis, Orchopeas howardi): These carry bacteria like Bartonella and jump between hosts.

• Lice (Enderleinellus spp.): They cling to hair, causing intense itching.

• Mites (Sarcoptes scabiei, Demodex): These trigger skin damage and hair loss.

Infested squirrels scratch relentlessly, leading to open sores and secondary infections. Heavy parasite loads can cause anemia, dehydration, and altered behaviours like reduced foraging.

Mange: A Microscopic Menace

What Causes Mange?

Mange is caused by Sarcoptes scabiei mites, which burrow into a squirrel’s skin, triggering inflammation and severe itching. Symptoms include:

• Patchy hair loss, starting around the head and shoulders

• Crusty, thickened skin, often grey or white

• Lethargy and emaciation due to disrupted foraging

Squirrels with mange may scratch obsessively or rub against trees, worsening their condition.

How Mange Spreads

Mange spreads through direct contact in shared nests or during social interactions. It can also affect other mammals, like foxes or dogs, in shared environments. In dense urban squirrel populations, outbreaks spread quickly.

Spot an outbreak: Watch for squirrels with bald patches in colonies near your home. Report sightings to a licensed wildlife rehabilitator.

Viral Diseases: Squirrel pox and Beyond

Squirrel pox: A Devastating Threat to Red Squirrels

Squirrel pox, caused by a poxvirus, is deadly to native red squirrels (Sciurus vulgaris) but often harmless to grey squirrels, which act as carriers. Symptoms in red squirrels include:

• Skin ulcers around the eyes, ears, and face

• Swelling and crusting of lesions

• Rapid decline and death within two weeks

Grey squirrels spread the virus through direct contact or shared surfaces like feeders. This disease has driven red squirrel declines across England and Wales, with numbers dropping from 3.5 million in the 19th century to under 140,000 today, according to the Red Squirrel Survival Trust.

Conservation efforts: Pilot vaccine programs are underway to protect red squirrels, but no broadly available vaccine exists yet. Support red squirrel conservation by reporting sightings to local wildlife trusts.

Other Viruses: Herpesvirus and Adenovirus

Squirrels can contract herpesviruses (ScHV-1), causing oral ulcers or lethargy, and adenoviruses, leading to respiratory or digestive issues. Grey squirrels often carry these viruses without symptoms, while red squirrels suffer higher mortality. These dynamics exacerbate red squirrel displacement in the UK.

Bacterial Infections: Silent but Serious

Common Bacterial Threats

Bacteria like Pasteurella multocida (pasteurellosis) and Streptococcus spp. enter squirrels through wounds or contaminated food, causing:

• Abscesses and inflammation

• Respiratory issues or pneumonia

• Neurological symptoms like head tilt or disorientation

Urban squirrels face higher risks due to dense populations and exposure to human waste.

Tularemia: A Rare but Potent Risk

Tularemia, caused by Francisella tularensis, is a rare bacterial disease in squirrels. It spreads through:

• Direct contact with infected animals

• Tick bites (Dermacentor variabilis, Amblyomma americanum)

• Contaminated soil or water

Human cases are uncommon, with fewer than 200 annually in the US, but untreated tularemia can cause severe symptoms like fever and swollen lymph nodes. Protect yourself: Avoid handling dead squirrels and use insect repellent in wooded areas.

Leptospirosis: A Waterborne Concern

Leptospirosis, caused by Leptospira interrogans, spreads via urine-contaminated water or soil. Symptoms in humans include fever, muscle aches, and, in severe cases, kidney or liver damage. Urban parks and wet environments increase transmission risks.

Prevention tip: Clean pet bowls daily and avoid leaving standing water in gardens to deter squirrels.

Lyme Disease: Squirrels as Tick Hosts

Grey squirrels host ticks (Ixodes ricinus in the UK), which can carry Borrelia burgdorferi, the bacterium behind Lyme disease. While mice are primary reservoirs, squirrels sustain tick populations, increasing human exposure risks in woodlands and gardens.

Reduce tick encounters:

• Clear brush piles and dense vegetation

• Use squirrel-proof bird feeders

• Apply tick preventives to pets

• Check for ticks after outdoor activities

Rabies: Separating Fact from Fiction

Squirrels rarely carry rabies in the UK, as the country is considered rabies-free in terrestrial wildlife, according to the Animal and Plant Health Agency. Erratic behaviour in squirrels is more likely due to parasites, trauma, or neurological conditions than rabies.

Key takeaway: Squirrels pose no significant rabies risk in the UK. Report unusual behaviour to a licensed wildlife rehabilitator for assessment.

Zoonotic Risks: Diseases That Can Spread to Humans

Squirrel-borne zoonotic diseases are rare but include:

Disease - Cause - Transmission - Human Symptoms

• Tularemia - Francisella tularensis - Tick bites, contact with infected animals - Fever, ulcers, swollen lymph nodes

• Leptospirosis - Leptospira interrogans - Contaminated water or soil - Fever, muscle aches, kidney damage

• Salmonella - Salmonella spp. - Faecal contamination - Diarrhea, fever, cramps

• Ringworm - Fungal infection - Direct contact - Itchy, circular rash

Stay safe:

• Wear gloves when handling squirrel feeders or nests

• Wash hands thoroughly after outdoor activities

• Avoid direct contact with wild squirrels

Spotting Diseased Squirrels

Healthy squirrels are agile and alert. Diseased squirrels may show:

• Lethargy or unresponsivenes

• Hair loss or open sores (e.g., mange, squirrelpox)

• Erratic movements like circling or stumbling

• Swollen abdomen or laboured breathing

What to do: Don’t attempt to treat sick squirrels yourself. Contact a licensed wildlife rehabilitator or local wildlife authority to ensure safe, legal handling.

Preventing Disease Transmission

Personal Hygiene

• Use disposable gloves when cleaning squirrel feeders or handling traps

• Wash hands with soap for 20 seconds after contact with wildlife areas

• Use alcohol-based sanitizers (60% ethanol) when water isn’t available

Home and Garden Tips

• Clean feeders weekly with a 10% bleach solution (1 part bleach, 9 parts water), rinse thoroughly, and air-dry

• Secure bins and compost to deter squirrels

• Avoid hand-feeding to reduce bite risks

Protecting Pets

• Apply vet-recommended flea and tick preventives

• Supervise outdoor pets to prevent squirrel interactions

• Clean outdoor pet bowls daily to avoid contamination

Ecological Impacts of Squirrel Diseases

Squirrel diseases reshape ecosystems in profound ways:

• Red Squirrel Decline: Squirrelpox, carried by grey squirrels, has reduced red squirrel populations by over 90% in some UK regions.

• Biodiversity Shifts: Disease outbreaks regulate squirrel populations, affecting seed dispersal and predator-prey dynamics.

• Climate Change: Warmer climates expand parasite ranges, increasing mange and tick-borne disease risks.

Support conservation: Preserve natural habitats and report squirrel sightings to local wildlife trusts to aid red squirrel recovery.

Wildlife Rehabilitation: A Vital Role

Licensed wildlife rehabilitators, regulated by Natural England, treat thousands of sick or injured squirrels annually. They:

• Quarantine animals to prevent disease spread

• Administer treatments like miticides for mange or antibiotics for infections

• Ensure animals are fit for release or humane dispatch, per UK law

How to help:

• Report sick squirrels to your local wildlife rehabilitator

• Avoid feeding wildlife to reduce disease transmission

• Support rehab centres with donations of supplies like linens or heat lamps

Legal and Humane Grey Squirrel Control

Grey squirrels are an invasive species in the UK, and their control is regulated under the Wildlife and Countryside Act 1981 and the Invasive Alien Species Order 2019. Key regulations include:

• No release: It’s illegal to release trapped grey squirrels into the wild or allow them to escape.

• Humane dispatch: Trapped squirrels must be humanely euthanised, adhering to the Animal Welfare Act 2006.

• Licensing: Keeping grey squirrels as pets or for long-term rehabilitation requires a licence from Natural England.

Why choose professionals? BPCA-certified technicians are trained in legal, humane, and effective methods, ensuring compliance and safety.

Act now: If grey squirrels are nesting in your attic or causing damage, contact Apex Pest Control for a compliant, professional solution.

Frequently Asked Questions

Can I keep a grey squirrel as a pet in the UK?

No, unless you have a licence from Natural England or Natural Resources Wales. Keeping grey squirrels without permission is illegal.

Can I release a trapped grey squirrel?

No. Releasing grey squirrels into the wild is illegal under the Invasive Alien Species Order 2019. They must be humanely dispatched, per the Animal Welfare Act 2006.

Are squirrel-borne diseases a risk to my family?

Most squirrel diseases pose low direct risk, but ticks from nests can transmit Lyme disease in some areas. Use gloves and avoid handling wildlife.

How do I spot a squirrel infestation?

Look for scratching noises in attics at dawn or dusk, shredded nesting materials, or chewed wires and insulation.

Why choose a BPCA-certified pest control company?

BPCA-certified technicians ensure legal, humane, and effective pest control, protecting your home and wildlife, in line with BPCA standards.

Take Control with Confidence

Grey squirrel infestations and their diseases require more than DIY solutions. From attic damage to zoonotic risks, prompt action delivers lasting results. Trust Apex Pest Control for BPCA-certified, humane, and compliant solutions tailored to your needs.

Contact us today for a professional inspection and peace of mind.