Coccidiosis in Mice
Coccidiosis is an intestinal parasitic disease caused by microscopic protozoans of the genus Eimeria. In domestic mice, it primarily affects young animals and colonies where multiple mice live together. The parasite multiplies in cells lini...
What is it?
Coccidiosis is an intestinal parasitic disease caused by microscopic protozoans of the genus Eimeria. In domestic mice, it primarily affects young animals and colonies where multiple mice live together. The parasite multiplies in cells lining the intestine, damaging the digestive tract and disrupting nutrient absorption.
In most cases, infection remains mild and produces no visible signs in healthy adult mice. It becomes problematic during periods of stress, overcrowding, or in young mice whose immune system is still developing.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Infected mice may show watery diarrhoea, dull and raised fur, gradual weight loss and lethargy.
The belly may appear swollen or tender. In more severe cases, blood may be visible in the faeces.
Young animals are most at risk: they grow poorly, remain stunted and can dehydrate rapidly if diarrhoea persists.
Many carrier mice show no symptoms, making detection difficult without faecal examination.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
The disease is caused by coccidia of the genus Eimeria, single-celled parasites that specifically infect cells in the intestinal lining. Several species can affect domestic mice.
The parasite reproduces in the intestine and releases microscopic eggs called oocysts, which are shed in faeces. These oocysts become infectious after time in the environment, then are ingested by another mouse that becomes infected through grooming or consuming contaminated food or bedding.
Young mice and recently weaned animals are most vulnerable. Overcrowded housing, infrequently changed bedding, stress (transport, change of habitat, mixing with other mice) or weakened immunity from another disease increase the risk of clinical disease.
Introduction of a new carrier animal into a healthy group is a frequent cause of outbreaks.
Transmission
Transmission occurs by the faeco-oral route: the mouse ingests oocysts present in faeces, bedding, water or contaminated food. Close contact in shared cages, poor hygiene and stress promote rapid spread between individuals.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian makes a diagnosis through microscopic examination of faeces to identify coccidia oocysts. A thorough clinical examination helps assess overall health and rule out other causes of diarrhoea.
In a breeding setting, several animals from the group can be tested to assess the extent of contamination.
Treatment
Treatment relies on specific antiparasitic drugs (anticoccidials) prescribed by the veterinarian, combined if needed with rehydration and nutritional support.
Thorough cleaning of the environment is essential alongside treatment to prevent immediate reinfection.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Regular and thorough cleaning of the cage, bedding and accessories significantly limits the buildup of oocysts in the environment.
It is advisable to avoid overcrowding, disinfect equipment between groups of animals and quarantine any new animal before introducing it into an existing colony.
Balanced nutrition and a low-stress environment strengthen mice's natural resistance to this common parasite.
Possible complications
Severe and prolonged diarrhoea can cause significant dehydration, especially in young animals, with risk of death if not managed. Extensive intestinal damage can also promote secondary bacterial infections.
When to see a veterinarian
Diarrhoea lasting more than 24 to 48 hours in a mouse
Blood in the faeces
Rapid weight loss or refusal to eat
Marked lethargy, mouse remaining still or unresponsive
Multiple mice in the same group showing similar signs
Prognosis
The prognosis is generally good in healthy adult mice that receive appropriate treatment. It becomes more guarded in young mice or weakened animals, where rapid dehydration can become life-threatening without prompt care.
Frequently asked questions
Is a mouse carrying coccidia necessarily sick?
No. Many mice harbor coccidia without ever developing symptoms, especially if their immune system is strong and their environment is clean.
Can mouse coccidiosis be transmitted to humans?
No, the Eimeria responsible for murine coccidiosis are specific to rodents and do not represent a known risk to humans.
How can I prevent the entire cage from becoming contaminated?
Frequently cleaning the litter, isolating sick animals, and disinfecting equipment limit the spread of disease between mice in the same group.
Should all mice in the group be treated?
The veterinarian assesses each case individually; in collective farming, group treatment is often recommended to prevent cross-reinfestation.
References
ESCCAP — European Scientific Counsel Companion Animal Parasites
Content reviewed by the TunisieVet editorial team · Updated 27 August 2026
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