II. Heat Exhaustion
III. Urolithiasis
IV. Ringtail
V. Degenerative Diseases
Malocclusion is a condition caused by overgrown incisors which result from trauma, bacterial infection, or genetic factors. Hypersalivation may be observed. Treatment consists of clipping overgrown teeth with guillotine-type nail clippers or a Dremmel-type dental disc every 2 to 3 months.
Rats have a limited ability to regulate body temperature with
the primary thermoregulatory mechanism being tail vein dilation or constriction.
Predisposing factors to heat exhaustion are ambient temperatures above
28oC (85oF), high humidity (about 80%), poor ventilation
and overcrowding. The rats salivate profusely to wet the hair coat
for cooling, and water consumption increases (see photo). Death from
heat exhaustion can be diagnosed from history of high temperature, lack
of water (or empty water bottles), saliva soaked chins, hyperemia of lungs
and mesenteric vessels, and hemorrhage in the thymus. Treatment of
affected rats includes cool water baths, forced-feeding water, and subcutaneous
saline or 5% dextrose administration.
Uroliths occur both in the renal pelvis and the urinary bladder.
Clinical signs may be absent but obstruction within the pelvis may cause
hydronephrosis. Occlusion of the neck of the bladder will cause acute
dilatation, uremia and death.
Insufficient environmental humidity (<20%), artificially increased
temperature and drafts predispose this condition. Other physiological factors (age, hydration,
nutritional status, and genotype) can also be involved. Annular constriction
of the tail is observed in young (suckling and weanling) rats. Necrotic tails may slough.
Diagnosis is made via clinical signs and history of low environmental humidity.
There is no treatment for affected rats. Tail stumps usually heal
without complication. Prevention of ringtail is accomplished by providing
sufficient environmental humidity, reducing drafts, and maintaining room
temperatures between 70oF to 74oF. 
V. Degenerative Diseases
Spontaneous degenerative lesions of the spinal cord and peripheral nerves are usually seen in rats greater than two years of age. Clinical signs include paresis/paralysis of the hindlimbs. The lesions in the spinal cord and peripheral nerves are characterized myelin sheath vacuolation, Wallerian degeneration and infiltration of macrophages into intramyelinic spaces. Radiculoneuropathy is degenerative disease of the spinal roots. Demyelination is most prominent in the ventral root ganglia and associated motor nerves of the lumbosacral spinal cord and cauda equina.
Progressive glomerulonephrosis is an aging disease of rats that is influenced by gender, genotype, and dietary factors such as protein content and total calories consumed. Severely affected kidneys have a pitted surface and protein rich urine. Histologic features include glomerulopathy with thickened glomerular capillaries, dilated tubules often with proteinaceous casts and interstitial fibrosis. Complications of renal disease may include weight loss, hypertension, and secondary renal hyperparathyroidism.
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