Unwanted Variables
Environmental and biological factors may profoundly effect data from animal
experiments by exerting a subtle influence on the investigator's research and testing. One
possible factor is disease. Many diseases of laboratory animals are highly contagious and
can spread rapidly through an animal colony. The best way to avoid such a disaster is to
follow a sound disease prevention program. One chapter of the disease prevention
program is the chapter on rodents as pets at home. These animals can carry infectious
diseases and parasites which can be brought into an animal facility and spread through the
animal population. We all need to develop an awareness that street clothing and shoes can
act as disease formites. Street clothing and shoes can be contaminated with
microorganisms and brought into the animal facility. For example, it is advisable, when
you are involved in research involving rodents, not to have a rodent at home as a pet.
Even if the pet appears to be healthy, it can be a carrier of a microbial agent that could
effect the research animals, which could also effect the outcome of an experiment. We all
have an appreciation of the potential impact of cross contamination on a study. The
following chart will give you some information on microbial factors.
Microbial Factors*
Microbial agents often interfere with animal research. Pathogens may disrupt studies by
causing clinical disease, lesions, or even death. Less obvious and perhaps less appreciated
are the insidious effects that microbes exert on several biological systems. Tumor
preparations and other transferable biological material can become contaminated with
infectious agents. Without adequate precautions, these infected materials may spread
infections to otherwise clean colonies.
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Complicating Microbial Factors
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Factor
Potential Complications
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Rodent viruses
Sendai Virus may complicate respiratory
research and modulate immune system
Mouse hepatitis virus may modulate
immune system and some important
enzyme systems.
Rodent mycoplasmas
M. pulmonis may complicate respiratory
research and immune responses
M. arthritidis may alter immune and
interferon responses
Bacterial disease
May interfere with research by causing
clinical disease, lesions, or death (for
example Pseudomonas aeruginosa may
kill immunocompromised animals)
Parasites
research; may influence immune
Rodent pinworms (for example,
Syphacia obvelata and Syphacia muris )
may depress antibody response to some
antigens
Encephalitozoon cuniculi , a common
protozoan infecting rabbit brain and
kidneys, may complicate CNS and kidney
response
* from The Biomedical Investigators Handbook
Foundation for Biomedial Research, Washington DC