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Why Do Medical Researchers Use Mice?

Last Updated: 16.06.24


Even if you declared war on mice and are checking some mouse poison reviews, take a minute to think about their contribution to today’s science. Mice have been used as lab animals for a long time and a lot of scientists are still using mice for tests. Because their behavior is easy to understand, they are convenient, and several generations can be observed during the same experiment, mice seem to be the best choice for medical researchers.


Mice are the first option for scientists

In order to formulate new diabetes drugs or test food supplements, mice and rats play an important part in developing new medical wonders. Actually, almost 95 percent of all animals used for scientific research are rats and mice, according to the Foundation for Biomedical Research (FBR).



What makes mice a good choice?

Researchers and scientists prefer to conduct their experiments using mice for a few reasons. First of all, mice are convenient. They have a small body, are easy to take care of, and have a high level of adaptability to new surroundings. 

Furthermore, they reproduce quickly and don’t have a long life span as most of them live for two or three years. Although it may seem insensitive, a short life span is an advantage because several generations of rodents can be used for research in a rather short period of time.


Using mice is practical

Imagine you are a scientist and need a testing subject so you can go on with your work. For certain reasons, you have decided to use mice as your subject of choice. This only makes sense as mice are easy to feed and house and some people who have worked with mice claim these rodents could form a bond with humans, which might create a more gentle behavior.

But kidnapping mice is not part of your job as a highly respected scientist. You can’t just search back alleys with a burlap sack and hope to catch a large number of testing subjects. So you do what you usually do when you need something. Search for it online. Mice are quite inexpensive and can be purchased in large quantities from a commercial producer that breeds mice especially for scientific research. 


Plenty of options

As a scientist, you don’t have a lot of mouse species to choose from since all laboratory mice are part of the Norway species. The mice from the Norway species are bred specifically for research and testing purposes, and some strains are more wanted for different experiments.


What is a strain?

The term ‘strain’ indicates a group of mice (or rats) having the same ancestor. There are a few strains that are highly popular in laboratories: the Wistar, the Fisher, and the Sprague-Dawley strains are used frequently in all types of research. 

Besides these initial strains, there are also sub-strains which might have certain differences regarding their genetic features. For example, the Zucker sub-strain is prone to obesity and diabetes, which makes it ideal for research on these diseases.



Why do scientists prefer to use mice from the same strain?

The majority of mice used in medical tests are inbred so there aren’t many differences between them. According to the National Human Genome Research Institute, for a more uniform medical trial, scientists use mice that are almost identical genetically. The only condition is that mice used as test subjects must be of the same purebred species.

However, inbred rats are not always the best option. Even if they have genetic uniformity, they could also have genetic features that aren’t relevant when it comes to studying general populations of mice. Outbred mice could be a better choice as they mimic better the human population’s traits.


Science uses previous results

Mice have been used for a long time as test subjects all over the world. So it only makes sense to select the same animal when researching similar or related topics. This is why the use of mice in laboratories has increased a lot during the last decades. Scientists want to use the same animal as previous studies did so they could accurately compare their results.


Mice are well understood by humans

These small rodents make proper research subjects because their genetics, physiology, and anatomy are well understood by scientists so it’s easy to observe any change in a mouse’s behavior. Also, mice are usually docile and mild-tempered so lab personnel can handle them easily, although some of the mice could be tougher to handle than others.


Mice’s genes are easy to mutate

If you think about developing drugs for human treatment, it would make sense to test them on primates. Thinking that primates are better test subjects than mice is not wrong. Keep in mind over 95 percent of the primates’ genetics is closely linked to us. However, using primates in research is way harder than using mice.

Think about how much it would cost to have over 100 primates as test subjects. Any species of primate would cost more to purchase, need more space, and eat way more than a mouse. To have accurate results, scientists have found a way to mutate the genes of mice so they could simulate the human genes.

Over the last twenty years, the similarities between humans and mice became stronger and stronger. Scientists are able to breed genetically modified mice, known as ‘transgenic mice’. These mice have genes similar to the genes that cause diseases among humans. 

The scientific process went even further as scientists can turn off or make inactive some of these genes. This led to the creation of the ‘knockout mouse’ which is used to better understand the effect of chemicals that are causing cancers (known as carcinogens). According to the Foundation for Biomedical Research, drug safety can be improved using knockout mice.

Furthermore, some of the mice ‘suffer’ from SCID (severe combined immune deficiency) so they are naturally born without a functioning immune system. These mice are used to study normal or malignant human tissue, according to the FBR.



Example of diseases studied using mice

Since animals have been used for a long time as test subjects, there are a lot of diseases studied using mice. They have been used to study obesity, deafness, cancer, heart diseases, etc. But their usage doesn’t stop here since mice are included in studies regarding nutrition, aging, sensory, and genetic studies. 


How many mice are used for scientific research

In laboratories all over the world, mice and rats are certainly the most used test subjects. Almost 95 percent of animal research taking place in the United States is using rodents. In the European Union, the number is a bit smaller as 79 percent of all animal testing is done on rodents.

However, there is not an exact number of how many mice are used in scientific research. While the Department of Agriculture keeps track of how many species of birds, cats, or rabbits are used for testing, nobody has a list of all the mice used in laboratories. 

The number is estimated to be between 11 and 100 million mice used in the U.S. laboratories. This includes hospitals, universities or colleges, research institutes, private companies, and government organizations. 

While the number of academic citations involving dogs or guinea pigs has remained constant over the last decades, the number of mice-related citations has quadrupled since 1965. In the UK in 2015, scientists made over 3.3 million procedures on rodents while 73 percent of them involved mice. 


A monument for laboratory mice

The Monument to the Laboratory Mouse is placed on a patio at the Institute of Cytology and Genetics in Akademgorodok, Russia. This facility is associated with the State University of Novosibirsk which explores the DNA’s nature. The bronze figure wears pince-nez on the tip of its nose and sits on a granite pedestal. 

The mouse itself is not big as it measures only 27 inches, but the entire monument’s height is 98 inches. The wise-looking mouse wears a lab coat and is shown knitting a double helix of DNA. This symbolizes the continuous DNA research over the years, and how its own species helped this progress through numerous sacrifices.

To show that we still have a lot to learn about DNA and how the scientific research should be continued, the spiral made by the mouse winds to the left. If you don’t think of it as being unusual, try and remember how the basic DNA form was depicted in school textbooks and you will see it winds to the right.



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