In the realm of biomedical research, mice are widely used for various experiments. To guarantee their well-being and enhance the precision of experiments, it is imperative to dedicate time and attention to their daily care. This article delves into the nuances of maintaining mouse health, shedding light on key aspects of daily care and observation that significantly impact the success of scientific endeavors.

1. Hair Loss in Mice: Causes and Management

Most mouse hair loss is a benign, reversible process that often resolves on its own after eliminating influencing factors. The following information provides an overview of how to diagnose and treat hair loss in a lab mouse colony.

Differentiating Hair Loss Symptoms:

Hair loss in mice, whether overall or partial, accompanied by exposed skin, is more prevalent in certain strains. Differentiating between natural hair loss and injuries from fights or trauma is crucial. Hair loss typically involves the absence of fur without skin damage, while injuries manifest as bleeding or scabbing on the skin surface.

Causes of Hair Loss in Lab Mice: 

There are many causes of hair loss, including mouse behavior, feed nutrition, hormonal changes, parasitic infection/Escherichia coli infection, genetic influences, and drug effects. These factors are not completely independent.

The most common cause of hair loss in mice is over-grooming behavior, which is behavior that involves excessive grooming and varies significantly between different strains. For example, BALB/c mice rarely experience hair loss due to over-grooming, while strains such as B6 and 129S1 are more prone to it. Environmental stressors, such as high housing density, can exacerbate over-grooming.

During lactation, maternal mice may engage in over-grooming behavior towards their offspring due to hormonal changes, which can result in hair loss among the litter. There is a considerable amount of research on over-grooming and hair barbering in mice, which can be found by searching for relevant keywords and exploring our other articles on the topic.

When a mouse experiences hair loss, it is important to be aware of the possibility of microbial infections, such as surface parasite infections (mites are more common), which may cause the mouse to continuously scratch and appear hairless. In addition, infection with Corynebacterium can lead to patchy hair loss in immunodeficient mice.

Facility-Wide Impacts ofMicrobial Infections: 

In cases of microbial infections, such as mites, consideration of facility-wide impact is essential. Biological purification is recommended for infected mice, coupled with thorough facility cleaning and disinfection. The next section reviews mite infestations in more detail.

2. Mouse Mite Problems: Identification and Solutions

Many mites on the surface of mice cannot be directly observed by the naked eye and require microscopic examination. However, some larger mites, such as Dermanyssus gallinae, can be directly observed without magnification. Dermanyssus gallinae can feed on animal blood and typically climb to the top of the cage/cage after feeding. After being infected with mites, mice may exhibit hair loss alongside anxious and restless behavior due to itching.

Causes: Mostly caused by foreign mice carrying mites entering the facility.

Solutions: Try to eliminate them through biological purification and isolation protocols. Alternatively, drugs like pyrethroids/ivermectin can be used for treatment, including drug bathing for mice, cage/scaffold/facility spraying, etc. During the treatment process, it is necessary to fully consider the risks of mite transmission and the impact of drug toxicity on mice.

3. Mouse Bites: Risks and Handling

For standard specific-pathogen free (SPF) mice, biting incidents are generally not a cause for major concern. The first thing to do is to clean the wound and disinfect it in a timely manner. If bleeding occurs, compression and rinsing with clean water are advised. Since rodents are not reservoir hosts for rabies, rabies vaccination is usually unnecessary after a mouse bite.

4. Nutritional Supplementation Issues for Mice

In experiments utilizing sunflower seeds or other supplements for weight recovery or accelerated growth, caution is necessary. While mice may prefer sunflower seeds, their nutritional impact is similar to feeding them high-fat feed. Feeding sunflower seeds in large quantities can raise questions about experimental rigor and cannot replace standard feed.

5. Maternal Infanticide: Causes and Prevention

Several reasons may prompt mother mice to consume their offspring, including poor maternal instinct, alterations in scent, nutritional deficiencies, and environmental stressors. Maintaining a consistent environment and providing proper nutrition can mitigate these occurrences.

Poor maternal instinct: First-time mother mice may have inconsistent behavior in caring for their young, and there may also be individual cases of mother mice having a habit of eating their young.

Scent: Mother mice use smell to recognize their offspring. When the newborn mice have been recently handled or the cage has been changed, they may acquire the scent of disinfectant or marker, which can affect the mother mouse's ability to identify them and lead to her not caring for them. Any operation that affects the smell of the offspring may cause this problem, which is a common occurrence in handling.

Nutrition: When the feed lacks nutrition, mother mice may have insufficient milk production or their own nutrition deficiency, leading to an increase in the incidence of eating their young. For lactating mother mice, it is best to use breeding feed instead of maintenance feed.

Environmental factors: There are many environmental factors that can cause mother mice to eat their young. Many reports have suggested that factors such as excessive light and noise can lead to mother mice eating their young. Therefore, it is necessary to pay attention to areas that require frequent handling and areas with the closest lighting. Other environmental factors include high density of breeding or being scared, in a threatening environment, etc.

6. Ulcerative Dermatitis in Mice: Causes and Treatment

The cause of ulcerative dermatitis is not clear yet, but it may be a combination of genetic, dietary, environmental, and neural factors, which are more common in certain strains. Ulcerative dermatitis is often observed with mice constantly scratching themselves which leads to skin breakdown, resembling combat wounds in their appearance. Treatment methods, including toenail trimming, are explored in many available literature reports on ulcerative dermatitis as a way to help prevent injury.

7. Conclusions

In conclusion, meticulous attention to the daily care and observation of lab mice is paramount for the success of biomedical research. Understanding and addressing common issues ensure the well-being of these essential research subjects and enhance the reliability of experimental outcomes.