A List of Undesirable Organisms in Rodents that Could Potentially Affect Human Beings

A List of Undesirable Organisms in Rodents that Could Potentially Affect Human Beings
Page content

Existing Regulatory Laws and Bodies for Laboratory Testing

Here we discuss a partial list of undesirable organisms in rodents to illustrate examples of the different bacteria, viruses and pathogenic strains considered as disease carriers. The examples were selected from the many organisms discovered in our research, which exist as parasites among laboratory mice, rats, wild rodents and hamsters. Their inclusion in our list was based on the consideration that said parasitic organisms considered humans as alternative hosts.

Because of the dangers of undesirable organisms in rodents, the Clinical Laboratory Improvement Amendment was passed by Congress in 1988. This enhanced the specific regulatory requirements for laboratory testing by instituting the Laboratory Accreditation Program.

This was in addition to the already existing Commission on Office Laboratory Accreditation. These federal units are responsible for monitoring the laboratory testing done in facilities, whether community, independently or industrially operated.

However, these regulations and accreditations are primarily for accuracy and reliability standards pertaining to test results. Nonetheless, an accredited laboratory should adhere to the Good Clinical Laboratory Practice (GLCP) which covers both the research and clinical aspects in collecting data. This was subject to external audits that assessed compliance with the protocol-mandated standards of safety provided by the GLCP.

The significance of providing information about the existence of regulatory bodies to monitor these laboratory facilities is to put the readers’ mind at ease, while proceeding with the information this article is about to reveal.

The dangers presented by undesirable organisms in rats and mice used for laboratory testing are quite unsettling, inasmuch as incidences have been noted that prior to the 1988 Clinical Laboratory Improvement Amendment, there were lapses that caused the spread of diseases through infected laboratory personnel.

Selected List of Undesirable Organisms in Rodents

The list of parasites presented below are dangerous undesirable organisms in rodents capable of infecting humans with maladies and severe disorders in the form of respiratory tract diseases, digestive disorders in the form of diarrhea, skin and joint diseases, disorders of the central nervous system and other tissues, spleen, bone marrow, tonsils and lymph nodes.

Respiratory Disease Causing Parasites and Bacteria

462px-Virus Replication.svg

The Sendai Virus (SV)

This virus is one of the most important pathogens. It could combine with another organism called Mycoplasma Pulmonis and spawn serious respiratory outbreaks.

This was discovered in the 1950s; in line with the studies made to determine the possible cause of a critically dangerous respiratory outbreak of pneumonitis affecting newborns in Japan.

It was initially established as coming from swine afflicted with influenza, elevating as influenza among humans in Japan.

Inasmuch as rodents have been established as the natural hosts of SV, it was widely considered that the influenza strain emanated from laboratory testing sites. Studies have shown that the SV considered human beings as natural hosts through reactive viruses that could bring about parainfluenza 1 and hemadsorption. Hemadsorption is a viral condition where the red blood cells tend to absorb or envelope each other.

SV is described as highly contagious, in fact, one of the most contagious infections found in lab rodents. Natural infection takes place in the respiratory tract and can be transmitted airborne within 5 to 6 feet.

Mycoplasma Pulmosis or M. Pulmosis

Mycoplasma pulmosis, or M. pulmosis, is classified as a bacterium that can find natural breeding grounds in rodent bodies resulting in a disease among rats called Murine Respiratory Mycoplasmosis or MRM. Rodents infected with this pathogen were observed as snuffling, chattering, experiencing weight loss, exhibiting hunched posture or ruffled coats, with tilted heads and manifesting inactivity. Infection from this bacterium could also take place in the genital tracts of female rats.

The development or worsening of the disease could be influenced by another strain, known as CAR bacillus, as the latter could cause the increasing growth of M. Pulmosis.

Streptococcus Pneumonia

Streptococcus pneumonia is a bacterial strain of pneumonia described as lancet-like and found to grow on blood sugar. The growth of this bacterium is facilitated by the presence of CO2. Scientific studies revealed that this pathogen considers humans as its natural hosts.

Although present in rodents, studies show that about 40 percent to 70 percent of normal human adults carry this type of bacteria in their throats, often occurring in the host’s nasal passages and middle ears, and transmissible by aerosol.

Clinical signs include labored abdominal breathing, weight loss, hunched posture and snuffling..Scientists are unable to determine by what methods thess organisms can spread in rats or men. Severe infection with this bacterium could lead to arthritis, meningitis, hepatitis, spleen inflammation, peritonitis and swelling of the testicular organs.

Continuation of Respiratory Diseases Caused by Undesirable Organisms in Rodents

Mycobacterium Avium-Intracellulare

This bacterium is described as reliant on oxygen or free air, acid resistant to discoloration, non-spore performing and its known hosts are birds and man. There are non-tuberculous types found existing in soil and water.

The most common carriers of this bacterium are urine-infected puddles or vessels containing contaminated drinking water.

Pneumocystis Carinii

These pulmonary alveol-causing bacteria consider humans among its many natural hosts. Animals affected by this strain tend to become emaciated, and their lungs tend to enlarge.

This bacterial strain can be transmitted through inhalation of infectious sacs of air or liquid expelled through exhalation or coughing.

Klebsiella Pneumoniae

This organism is commonly found as part of the normal gastrointestinal tract in humans and animals, while infection from this bacterium could be manifested by sneezing, lack of appetite and hunched postures.

Streptococcus Pyogenes

This pathogen is a bacterium of the streptococcaceae, considers humans as its natural hosts, and is usually exhibited in the human body in the pharynx, skin and genital area.

Undesirable Organisms in Rodents that Cause Diseases in the Digestive System

Mouse Rotavirus

This is a disease-carrying virus largely found among suckling mice. It was later called epizootic diarrhea of infant mice. Clinical studies show that these types of viruses are common causes of neonatal diarrhea in children.

Studies show that this viral strain is transmissible via airborne infection as it is carried by contaminated dusts emanating from mice beddings. Additional findings disclosed that susceptibility to this disease is age dependent. Passively and and actively acquired imuno agents are important as defense against this viral strain.

Rat Rotavirus-like Agent

This virus was found to be the prevailing cause of widespread diarrhea in human adults and children in the city of Baltimore Maryland. It could be acquired through airborne transmissions emanating from mouse rotavirus-like infected cages.

This is one case where it was also suspected that the spread of the disease was transmitted from infected rats to infected personnel.

Salmonella Enteritidis

Salmonellas were determined to be primarily acquired by ingestion of contaminated food and water, wherein rat beddings are considered as the main source of the infective strain.

Infected carrier hosts included those that were described as shedding organisms and lab personnel.

However, researchers found it difficult to perform the detection of carrier animals inasmuch as there were no satisfactory method that could test suspected carrier animals.

Hymenolepis Nana or Dwarf Tapeworm

These organisms are directly infectious when eggs are ingested by a potential host.Thereafter, the eggs could hatch within the intestines of the new host.

Example of transmission could be by way of an arthropod beetle that ingests the eggs; another host, usually a bird, preys on the beetle, and the eggs continue to contaminate the possible food of the definitive host. The final host considered as a natural host, is where the egg develops as an adult tapeworm.

Parasites and Bacteria in Rats & Mice that Cause Skin and Joint Infections

Poxvirus in Rats

Incidents of personnel infected with this virus disclosed that four out of the 40 exposed to rats infected with this virus, suffered from headaches, weakening, cough, rhinitis, irritation in the throat and stomach upset. Two out of the four infected individuals developed rashes on the head, shoulders, knees and on the back of their hands.

An outbreak of this disease was recorded as having taken place in USSR and was deemed associated with the entry of wild rodents in animal facilities. Its effects could be in a pulmonary form or dermal form, wherein high mortality rates were noted among rats infected through pulmonary disorder.


The skin infection from this disease-causing bacterium is manifested through alopecia, lesions appearing around the mouth and eyes, and anywhere in the body.

Staphyloccocus Aureous

A type of skin disease described as extremely powerful that could infect the tissues and enter the bloodstream, which could lead to death.

Viruses in rodents that Attacks the Central Nervous System

Encephalitozoon Cuniculi

This is a viral protozoa whose disease is transmitted orofecally, wherein urine or feces excreted by these organisms could be ingested by a host, usually a rabbit, and transmitted vertically to the final host, possibly a human being.

This disease is found occurring in humans, and could compromise the immunity of human infants.


Laboratory facilities are controlled. However, the parasites and bacteria included in our list of undesirable organisms in rodents could still exist in our own households. The existence of rodents is possible in abandoned or other uninhabited structures in nearby areas within our communities.

Based on the information gathered, the matter of keeping our surroundings clean, free of dust mites, or spore growths, and eliminating places where rodents could build nests for their offspring is important. Some of these disease-causing organisms thrive on air, hence diseases could be airborne and a part of the air we breathe. Others are transmissible through smaller living creatures as the eggs of the parasites could transfer from host to host in an ascending order.

Reference Materials and Image Credit Sections

Reference Materials:

Image Credit:

  • All images courtesy of Wikimedia Commons