Epilepsy: The gerbil displays spontaneous epileptiform seizures (see photo). These seizures may be precipitated by sudden stress, handling, or introduction to a novel environment. Incidence of this syndrome is about 20% in natural populations. The condition appears to be inherited, and both seizure-resistant and seizure-sensitive strains have been developed by selective breeding. Inbred animals can have up to 100% incidence. Seizures vary in severity from mild hypnotic episodes characterized by cessation of activity and twitching of the pinnae and vibrissae, to severe myoclonic convulsions followed by tonic extensor rigidity. Post-seizure fatality occurs in less than 1% of affected animals. There is no permanent damage. Seizure onset occurs at 2 to 3 months of age with seizure incidence and severity increasing with age until the animal reaches six months of age. A refractory period of up to five days can follow more severe seizures. Research has shown that the seizure response can be almost completely suppressed in genetically predisposed animals if they are frequently stimulated by handling during the first three weeks of life. Anticonvulsant therapy is neither necessary nor recommended.
Nutritional Problems: Gerbils normally thrive on a good quality rodent chow, but may have deficiency problems when fed home-made diets, sunflower seed diets, or table scraps which lack specific nutrients. Signs of deficiencies will be manifest as in other mammals. A feeding level of 5 grams of pelleted chow per day has been recommended to prevent obesity which can predispose to islet cell hyperplasia and hyperglycemia.
Neoplasia: Older gerbils commonly develop a number of spontaneous neoplasms most commonly affecting the skin, adrenal gland, kidney, spleen, intestine and the female reproductive tract. The most frequently seen neoplasms include leiomyomas, subcutaneous fibrosarcomas, sebaceous gland adenomas and adenocarcinomas, splenic hemangiomas, adrenal adenomas, duodenal adenocarcinomas (usually in males), and malignant melanomas. Diagnosis is based upon clinical course of the disease and histopathology.
Geriatric Diseases: Syndromes commonly seen in aged gerbils include cystic ovaries (20% of all females) and chronic interstitial glomerulonephritis. Cystic ovarian disease accounts for the majority of cases of decreased fertility in breeding aged gerbils. Gerbils with glomerulonephritis develop polyuria and polydipsia, and progressive weight loss clinically. Chronic interstitial glomerulonephritis may occur in combination with neoplastic lesions.
Starvation and Water Deprivation: These managerial problems are often seen with overcrowding or prolonged shipping. Weanlings are particularly susceptible to starvation and water deprivation if they are unable to reach the food hopper or sipper tube on the water bottle. A good history and review of husbandry practices help in formulating a diagnosis since no gross lesions except an empty stomach and loss of body fat (adult gerbils only) are observed on post-mortem exam. Attention to proper husbandry practices is the main aim in prevention.
Tail Lesions: Barbering of the tail hairs is observed in cages that are overcrowded. The hair grows back once the cage population is diminished. Fractures of the tail vertebrae, and slipping of the tail skin can all occur with improper handling. This usually involves picking up animals by the distal portion of the tail. Surgical amputation with cautery (silver nitrate cautery) supportive post-surgical care may be necessary when large amounts of tissue are compromised. Such injuries may be prevented by handling animals by the base of the tail.
Rough Hair Coat: An unkept, matted hair coat is often an indicator of excessive humidity levels in the environment (50% relative humidity). (Rough looking hair is also the most frequent physical reflection of active disease in most rodents.) This problem is often seen in animals kept in solid-topped aquariums or microisolator cages. Adequate air exchange to remove excess moisture is the best preventative measure.
Aminoglycoside Toxicity: Aminoglycosides are toxic to gerbils. Antibiotic ointments containing aminoglycosides have caused mortality presumably from ingesting the ointment, and experiencing neuromuscular paralysis from impaired acetylcholine release.