GASTROINTESTINAL DISEASES Main
I. Aminoglycoside ToxicityAminoglycosides are toxic to gerbils. Antibiotic ointments containing aminoglycosides have caused mortality presumably from ingestng the ointment, and experiencing neuromuscular paralysis from impaired acetylcholine release.
Endoparasites of the gerbil may include mouse pinworms (Syphacia obvelata) which can be found in the cecum and a small intestinal gerbil pinworm Dentostomella translucida (A.). Syphacia ova can be recovered on a cellophane tape test (see mouse parasitic diseases), while Dentostomella ova (B.) are identified by the fecal floatation test.
Gerbils also are commonly colonized by intestinal flagellated protozoa (Giardia and Tritrichomonas sp.). No clinical signs of disease are usually associated with naturally occuring helminth infections in gerbils. Please refer to the appropriate section elsewhere in this handbook for details on diagnosis, treatment, and control if any of these parasites are suspected or diagnosed.
Identification of intestinal protozoa can be made by performing examination of feces for protozoal cysts or by preparing wet mount preparations of intestinal contents at necropsy. The hard fecal pellet of gerbils can be softened in saline, and a flotation performed to look for protozoal cysts. Metronidazole at 10 mg/ 100 ml water may be effective in controlling protozoal infections.
Tapeworm infections (Hymenolepis nana or H. diminuta) have been infrequently reported to cause clinical signs of dehydration and diarrhea during heavy infections in a wide variety of rodents, including gerbils. Because of the direct life cycle of H. nana, tapeworm infections in gerbil should be definitively diagnosed. It is not known whether praziquental or niclosamide are effective in eliminating tapeworms from gerbils.
Public Health Significance: Man is a definitive host for H. nana.
Salmonella enterica, along with protozoal infestation, and food deprivation, have all been reported to be causes of enteritis in gerbils. The affected animal may rarely have moderate to severe diarrhea, but frequently displays a rough hair coat, weight loss, depression, and dehydration. Acute death will sometimes be encountered. Gross lesions may include a congested liver, gastrointestinal distension, and a fibrinosuppurative peritonitis in gerbils with salmonellosis. Positive culture of Salmonella sp. should indicate concern for personnel safety. No treatment has been reported to be effective and severely affected colonies should be depopulated.
Public Health Significance: People may contract salmonellosis from infected gerbils.
Although much less common than in other rodent species, malocclusion and overgrowth of the incisors do occur in gerbils. Gnawing on metal in the cage can cause the incisors to break resulting in overgrowth of the opposing pair. Clinical signs of malocclusion can include weight loss, depression and emaciation. Treatment is by carefully trimming back the overgrown teeth with dummel tools. Resco nail clippers may also be used but it is possible to case detrimental longitudinal fractures of the teeth with this method.
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.
VI. Starvation and Water DeprivationThese 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.
A. Etiology: Clostridium piliforme is a gram-negative, pleomorphic, obligate intracellular bacteria that produces spores. The incidence of spontaneous disease is quite low, occurring in sporadic outbreaks.
B. Transmission: Infection occurs by contact with infected animals or bedding, via the fecal-oral route. Unlike most other rodents and rabbits, gerbils are innately susceptible to expressing overt Tyzzer's disease without a need for physiologic stress or steroid therapy to aid in disease development.
C. Clinical Signs: This is an acute enterohepatic disease in gerbils. In colony situations, high mortality rates can occur with some animals exhibiting depression, unthrifty appearance, and varying degrees of watery diarrhea. Morbidity and mortality is highest in young gerbils and pregnant females, although all age groups can be affected.
D. Pathology and Diagnosis: Grossly, multiple white foci of necrosis in the liver with mild to moderate enteritis (A.), serosal edema, and possible brain and cardiac involvement may all appear in affected animals. Coagulative liver necrosis with minimal inflammatory cell infiltrate (arrows) is observed on histopathologic examination of the liver (B.). Definitive diagnosis is made by demonstration of the organism in hepatocytes (arrows) surrounding necrotic foci of the liver or intestine sections stained by silver (C.) methods. Infection can also be diagnosed by PCR and detection of antibodies by ELISA.
E. Treatment and Control: No treatment is effective once the disease is clinically apparent due to the intracellular nature of the organism and its ability to sporulate. Treatment with tetracycline may decrease mortality. Control is achieved by strict sanitation and the reduction of environmental and experimental stress and/or by elimination of exposed and symptomatic animals. Disinfection of cages and equipment is best accomplished with sporocidal disinfectants such as 1% bleach solutions.
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