II. Fight wounds
III. Self-Mutilation
IV. Infertility
V. Dystrophic Mineralization
A. Barbering: A female mouse may develop a fur-chewing vice
and chew the hair off a cagemate or her litter. The hair over the
nasal and orbital regions or the dorsal cervical area is most often barbered.
The exposed skin is intact and normal in appearance. The only cure
for barbering, if the client considers it a problem, is to remove the mouse
that has not been barbered.
B. Alopecia: Alopecia often with accompanying epidermal thickening is one of the most common lesions seen in genetically engineered mice (GEM). The causes of alopecia are frequently unknown, and may be related with the genotype of the mouse.
Mice (particularly males) may fight and can inflict severe wounds upon
each other. These usually are located on the face, back, and genital
areas. If tail biting occurs, the tail may become gangrenous and
slough. The wounds may become infected and develop into abscesses.
Wounds may be treated by lancing and flushing with a disinfectant or antibiotic
solution. Topical antibiotic ointments containing aminoglycosides
should be avoided since ingestion of aminoglycosides can be toxic to mice
(the mechanism of toxicity is respiratory paralysis from ganglion blockade).
Prevention is by separating the fighting animals.
A. Otitis Media: Otitis media has been reported to result
in enough irritation to cause the animals to scratch the base of the ears
with the hind feet. The scratching can lead to excoriation and ulceration
of the skin of the neck and subsequent inoculation of the wounds with environmental
bacteria contaminating the feet. The resultant dermatitis evokes
a more intense scratching reflex until a large ulcerative pustular dermatitis
results from the self-mutilating activity. Parenteral antibiotic
therapy appears to be of little help for the otitis media or the dermatitis.
Clipping of the toenails or applying an Elizabethan collar will allow resolution
of the dermatitis with or without medicinal therapy. Certainly, the
value of the animal will dictate the decision to treat or euthanize.
B. Ulcerative Dermatitis Syndrome: Black mice of a C57BL genotype are prone to develop a dermatitis with alopeica and epidermal ulcers. Mice will scratch the dorsal cervical region, shoulder and caudal axillary regions until ulcers form. The ulcerated areas often scar, causing restriction of forelimb movement. Ectoparasite infestation may exacerbate the syndrome, but the syndrome develops in mite-free mice. The disease appears to be multifactorial, and dietary factors may play a role in disease expression.
C. Chemical Irritants: Forceps disinfected with germicidal
solutions are often used to transfer the mice from dirty to clean microisolator
cages. The forceps are dipped in the germicidal solution and mice
are either grasped by the tail or by the loose skin over the neck.
Improperly diluted quaternary ammonium solutions can chemically burn the
skin of mice and induce an ulcerative dermatitis. Skin lesions must
be monitored and treated for secondary bacterial infections and self-mutilation.
The more common causes of decreased reproductive efficiency can be the result of physiological, neoplastic, infectious or toxicological aberrations. Physiological causes of infertility include senescence, starvation or poorly balanced diets, cystic ovaries, abortions, and irregular estrous cycles induced by inadvertent exposure of wild male mice to established breeding colonies or abnormally long or short photoperiods. Neoplastic diseases of the reproductive tract or cancers that cause debilitation cause diminished fertility and usually coincide with aging or with specific inbred strain characteristics. Primary pathogenic bacteria and viruses responsible for low fecundity have been discussed in earlier sections. Enteric bacteria such as E. coli, Proteus sp., and Klebsiella sp. have also been isolated from abscessed preputial glands or infected uteri. Contamination of food or water with chemicals such as organophosphates has been incriminated in inducing abortions. Estrogens in feeds have induced scrotal hernias in male mice and poor fertility in female mice.
Dystrophic calcification regularly occurs on the epicardium of the inbred
strains of DBA/2 and BALB/c mice, and in the myocardium of C3H mice.
Soft tissue mineralization also occurs less frequently in other viscera
such as the kidney, liver, serosa of the stomach, small and large intestines,
and gonads. The mechanism of this disorder is unknown.
Back to Disease Categories