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This Is Probably Why Your Fancy Mouse Died


It’s always sad to lose a beloved pet, and even more so when that pet is a fancy mouse. Mice are generally very hardy creatures, but there are still some things that can cause them to succumb to an untimely death. Here are some of the most common reasons why your fancy mouse may have died:


Respiratory Infection

Mice are so very small and fragile, and so are their lungs. It’s very easy for them to develop a respiratory infection, and these are often fatal in mice.

This usually doesn’t lead to an instant and sudden death and is often accompanied by wheezing, lethargy, and a runny nose prior to death. If your mouse had any of these symptoms, it’s likely that a respiratory infection was the cause of death.

Many things can cause a respiratory infection in a mouse, from poor cage ventilation to a cold draft or some dust.

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Genetic predisposition

Fancy mice have been bred for generations to have certain physical traits. Unfortunately, this often comes with a price.

Many of these mice are bred to have very short noses and small mouths. This can cause problems with their breathing, and they are more prone to respiratory infections.

In addition, They have much higher cancer rates than other species of mice. This is likely due to inbreeding and a long history of genetic manipulation. Fancy rats also have a high incidence of cancer.

Most times a tumor will develop long before the mouse dies, but sometimes they can be quite sneaky and cause death quite suddenly.


Tyzzer disease

Tyzzer disease is a potentially fatal condition that affects mice and other small mammals. The disease is caused by a bacteria called Clostridium piliforme, which is found in soil and contaminated water.

Tyzzer disease is typically spread when an animal comes into contact with contaminated material, and the bacteria enter through the skin or mucous membranes.

In some cases, the bacteria may also be inhaled. Once inside the body, the bacteria multiply rapidly, causing severe damage to the liver, kidneys, and other organs.

Symptoms of Tyzzer disease include poor appetite, dehydration, diarrhea, lethargy, and jaundice. If left untreated, the disease will eventually cause death.

Treatment is typically limited to supportive care, as there is no cure for the disease. However, early diagnosis and treatment can improve the chances of survival.

Sometimes the onset is quick and symptoms aren’t observed until it’s too late, making Tyzzer disease a common cause of sudden death in mice and fancy mice.

Pancreatic tumors

Pancreatic tumors are another common cause of cancer in fancy rats and mice. These tumors can be benign or malignant, but either way, they can cause serious health problems.

Symptoms of a pancreatic tumor include weight loss, appetite loss, weakness, and diarrhea. In some cases, the tumor may also be visible on the outside of the body.

If left untreated, a pancreatic tumor will eventually cause death. Treatment options are limited and typically only involve supportive care.


Internal damage

Internal damage is often unseen and can be caused by a variety of things.

One common cause of internal damage is fighting with other mice. Mice are very territorial creatures, and fights are not uncommon.

Fights can often lead to serious injuries, such as punctured lungs or a ruptured spleen. These injuries can be fatal, especially in small animals like mice.

Mice can also fall and hit their heads, which can lead to internal bleeding and death.

External damage can sometimes go noticed, especially if the mouse is good at hiding it.

A common cause of external damage is barbering. This is when a mouse gnaws on its fur, which can lead to bald spots, open wounds, and infection.

Barbering is often a sign of stress, and if not addressed, it can eventually lead to death.



Although fancy mice often have a few extra things working against them, they are still relatively hardy creatures. Any mouse species can suffer from respiratory infections, Tyzzer disease, and pancreatic tumors, but fancy mice are especially susceptible due to their small size and genetic predisposition.

If your mouse has died suddenly and you wish to know why, place the mouse in the refrigerator (not the freezer), and contact your local vet to do a necropsy. It’s the only way to be sure.

If you are considering getting a fancy mouse, be sure to do your research and find a reputable breeder. Fancy mice are delicate creatures, but with proper care, they can make excellent pets.