Is respiratory disease in rats and mice contagious?

Yes, respiratory infections are often highly contagious between rats and mice. Bacteria like Mycoplasma spread easily through aerosolisation - simply breathing or sneezing near one another - or via contact. If you have a colony, it is vital to keep an eye on all members if one starts showing symptoms, as isolation may be necessary to protect the rest of the group.

What is the red discharge around my rat's eyes and nose?

That red discharge is called porphyrin. While it can look like blood, it is actually a pigment produced by the Harderian gland. While a small amount during grooming is normal, excessive porphyrin staining around the eyes and nose is a common clinical sign of stress, illness, or respiratory distress in rats. If you see this, it is time for a vet visit.

Why is cage ventilation so important?

Poor ventilation leads to a buildup of ammonia from your pet's urine, which is highly irritating to their sensitive airways. Ammonia fumes can quickly lead to chronic inflammation of the respiratory tract, making your pets much more susceptible to infections. This is why well-ventilated wire cages are generally preferred over glass tanks or solid-sided plastic tubs.

What should I look for in bedding to prevent respiratory issues?

Dust is a major enemy of small animal respiratory health. Avoid dusty shavings or low-quality bedding materials that aren't dust-extracted. High-quality recycled paper pellets or dust-free options are much better for keeping the air quality inside their cage clean and safe.

When should I see a vet for my rodent’s breathing?

As prey animals, rats and mice hide illness very well. By the time you notice obvious signs like audible wheezing, gasping for air, or mouth breathing, they are likely quite unwell. You should seek veterinary attention at the very first sign of a change, such as persistent sneezing, a decrease in appetite, or lethargy.

Last Updated: 28/04/2026

Respiratory Disease in Rats and Mice: A Vet Guide

Does your rat or mouse have a runny nose or sneeze often? Learn about the causes, clinical signs, and treatment of respiratory disease in small rodents.

Author: Dr Emilee Lay BVSc BSc (Vet) Hons

Reading Time: 5 minutes - short read

Rats and mice are intelligent, charming companions, but they are notoriously sensitive when it comes to their respiratory systems. Seeing your tiny friend struggle with a sniffle or a wheeze can be distressing for any pet parent. While respiratory issues are common in these pocket pets, they are often manageable with the right environment and proactive veterinary support. This guide explores how to identify the early warning signs and what you can do to help your little mates breathe a little easier.

Learn more in our Rat Care Guide.

Common causes of respiratory issues

Respiratory disease in rats and mice can be caused by a range of bacterial or viral agents.

Mycoplasma is one of the main bacteria that can cause respiratory disease.

Mild cases: Can cause an increased production of mucous in the airways.
Severe cases: Can lead to abscesses and pneumonia of the lung.
Transmission: It is mainly spread via aerosolisation (when affected rodents breathe and sneeze near each other) or in utero.
Management: Once established in a colony, it is often difficult to completely eliminate.

Other bacteria and viruses of concern include Streptococcus Pneumonia, CAR Bacillus, Sendai, and Sialodacryoadenitis Virus.

Episodes are often triggered or worsened by stress and environmental factors, such as:

Ammonia buildup from unclean bedding
Bedding material that irritates the airways
Overcrowding
Poor ventilation

These factors are interconnected. High levels of ammonia over long periods can cause inflammation of the airways, making your pet more susceptible to disease. This is often caused by:

Poor ventilation: Avoid using glass tanks and completely enclosed plastic enclosures.
Accumulation of waste: Excessive buildup of waste in cages.
Dusty bedding: Material that has not undergone dust extraction can irritate the airways and often has poor absorbency and odour management.

Diet also plays a role, as poor nutrition can result in a weak immune system, making your pet more susceptible to disease:

Muesli mixes: Often rich in sugars and carbohydrates but low in key trace vitamins and minerals.
Recommended diet: Feeding a high-quality extruded pellet dry food can help minimise these issues.

Signs to watch for

Clinical signs can vary, as prey animals rats and mice are good at hiding signs of disease until they are extremely unwell. Signs can include:

Unkempt coat
Weight loss
Increased breathing rate
Difficulty breathing
Sneezing
Discharge from the nose
Red discharge from the eyes, i.e. porphyrin staining
Conjunctivitis
Head tilt

Regularly handling your pet mice or rat at home is essential to picking up early signs of illness or disease. If you notice a minor change in their behaviour or overall health - make sure to have it checked by a vet.

Treatment and management tips

Because rats and mice are prey animals that often hide signs of illness, it is important to have your pet assessed by an experienced exotics vet as soon as you notice clinical signs. Your vet will perform a physical examination and may dispense:

Antibiotics, anti-inflammatories, and other medications to help open up the airways.
Treatments to reduce mucous production.

Respiratory disease is often a matter of management rather than a complete cure. Long-term, some animals may continue to have mild respiratory signs or need regular nebulisation. Nebulisation produces a fine vapour that delivers medications directly into the airways and helps reduce mucous. You can set up your own nebuliser chamber at home, but ensure you speak to your exotics vet prior to nebulising your pet.

When managing your pet at home, focus on these steps:

Quarantine: Depending on your setup and the number of rodents affected, try to separate the affected animal.
Environment: Ensure you have adequate ventilation, a heat source, and clean, ammonia-free bedding.
Nutrition: Provide nutritionally balanced, healthy, and fresh foods.

Given the infectious nature of respiratory disease in rats and mice, your vet may determine that an entire mousery or rattery needs treatment, which is why a professional assessment is so important. In the interim, you can:

Keep enclosures clean using veterinary disinfectants.
Keep high-energy pastes on standby to support particularly unwell pets.

Rodent Respiratory Disease FAQs

While respiratory disease is a frequent hurdle for rat and mouse owners, it doesn't have to compromise their quality of life. By prioritising clean housing, high-quality nutrition, and early intervention from an exotics vet, you can help your small companions live long, comfortable lives. Remember, these little ones are experts at hiding illness, so if you notice any subtle changes in behaviour, it is always best to book a check-up.

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History

Our experts continually monitor the health and wellness space and we update our articles when new information becomes available.

Tue 28 Apr 2026

Edited by Dr Gillian Hill BVSc (Hons)

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About the Author

Dr Emilee Lay BVSc BSc (Vet) Hons

Veterinarian

Dr. Emilee graduated from the University of Sydney in 2018 with a Bachelor of Veterinary Science and Bachelor of Science (Veterinary Studies) and as a student worked for a number of years as a small animals and exotics nurse in clinics across Sydney. She is currently a practicing small animal and exotic vet along the Coast. Emilee holds a special passion for avian and exotic medicine (bunnies being her favourite patients), as well as animal behavioural medicine!