Diseases of Gerbils PAT 707, Pathology of Laboratory Animals II Prepared by Trenton R. Schoeb Department of Comparative Medicine University of Alabama at Birmingham Winter Quarter 1989-90 Taxonomy Gerbils are members of the subfamily Gerbillinae (order Rodentia, family Muridae). There are about 100 species of gerbils in 14 genera, including Rhombomys, Psammomys, Meriones, Brachiones, Desmodilliscus, Gerbillus, Microdillus, Sekeetamys, Pachyuromys, Desmodillus, Ammodillus, Tatera, Taterillus, and Gerbillurus. The gerbil most commonly used for research in the US is Meriones unguiculatus, the Mongolian gerbil or jird, which was introduced into this country in 1963. Some of the other species are used occasionally, so one must be careful to relate reported lesions to the correct gerbil species. Most Meriones unguiculatus used in research are obtained from Tumblebrook Farm, Inc., West Brookfield, MA, but many local breeding colonies are maintained by investigators and pet shops. Viral Infections No natural viral infection of gerbils has been reported, although it is most unlikely that none exists. Gerbils are susceptible to experimental infections with many viruses. Matsuzaki H et al. 1989. Experimental encephalomyocarditis virus infection in Mongolian gerbils (Meriones unguiculatus). Vet Pathol 26:11-17. Staphylococcal Dermatitis One report. Endemic disease occurred in weanling gerbils from commercial suppliers shortly after admission to a multisource user colony of 200 animals. Five to 7 days after arrival, weanlings developed localized alopecia and erythema around the external nares, which rapidly progressed to moist dermatitis of the feet, legs and ventral body surfaces. In some groups of newly acquired weanlings, morbidity was 75 to 100% and mortality 25%. The predominant lesion was acute suppurative dermatitis. Severity varied from minimal neutrophilic infiltrates in the epidermis with acanthosis and hyperkeratosis to severe suppurative epidermitis and dermatitis with folliculitis and, in a few gerbils, chronic ulcerative dermatitis. A few had microabscesses in the liver. The causative agent was identified as a beta hemolytic, coagulase positive Staphylococcus aureus, phage type WH1. High humidity, fighting, and the trauma of taking blood samples were thought to have been contributing factors. Peckham JC et al. 1974. Staphylococcal dermatitis in Mongolian gerbils (Meriones unguiculatus). Lab Anim Sci 24:43-47. Nasal (Facial) Dermatitis This condition clinically resembles staphylococcal dermatitis, but its cause is unknown. The dermatitis affects 5 to 25% of juveniles and adults within a colony, and all animals in affected cages. Alopecia and reddened scabs appear first around the external nares, mainly on the upper lip. Over a period of weeks the alopecia and reddened crusts spread over the head and to the forepaws. Lesions are pruritic; frequent scratching can result in bleeding. Spontaneous regression is rare, even if affected gerbils are housed individually for extended periods. Microscopic characteristics of the lesions include mild acanthosis, hyperkeratosis, and accumulation of large numbers of neutrophils and macrophages in the adjacent dermis. Some affected gerbils have focal hyperplasia of the Harderian glands, leading to the speculation that increased lacrimal secretion could have a role, but some unaffected gerbils have similar changes. Trauma from burrowing into bedding also could be a factor; use of sand as bedding results in improvement.The disease is not associated with the trauma caused by wire feed hoppers, as it also occurs when feed is placed on the cage floor. Bresnahan JF et al. 1983. Nasal dermatitis in the Mongolian gerbil. Lab Anim Sci 33:258-263. Farrar PL et al. 1988. Experimental nasal dermatitis in the Mongolian gerbil: effect of bilateral harderian gland adenectomy on development of facial lesions. Lab Anim Sci 38:72-76. Thiessen DD , Pendergrass M. 1982. Harderian gland involvement in facial lesions in the Mongolian gerbil. J Am Vet Med Assoc 181:1375-1377. Tyzzer's Disease Several outbreaks of Tyzzer's disease in gerbils have been reported. Clinical signs are vague: anorexia and lethargy. Diarrhea is inconsistent. Mortality is greatest in gerbils 3 to 7 weeks old and may reach 85%. The lesions are similar to those in other species, but tend to be particularly severe. Intestinal lesions are most pronounced in the distal ileum and cecum but also occur in duodenum, jejunum and colon. Multifocal necrotizing and suppurative hepatitis is consistent. Some animals develop myocardial lesions. Waggie et al. (1984) consider gerbils extremely susceptible to Tyzzer's disease in comparison to other common laboratory animals. Carter GR et al. 1969. Natural Tyzzer's disease in Mongolian gerbils (Meriones unguiculatus). Lab Anim Care 19:648-651. Koopman JP et al. 1980. An outbreak of Tyzzer's disease in Mongolian gerbils (Meriones unguiculatus). Z Versuchstierkd 22:336-341. Port CD et al. 1970. Tyzzer's disease in the gerbil. Lab Anim Care 20:109-111. Port CD et al. 1971. An ultrastructural study of Tyzzer's disease in the Mongolian gerbil (Meriones unguiculatus). Lab Invest 25:81-87. Waggie KS et al. 1984. Experimentally induced Tyzzer's disease in Mongolian gerbils (Meriones unguiculatus). Lab Anim Sci 34:53-57. White DJ, Waldron MM. 1969. Naturally-occurring Tyzzer's disease in the gerbil. Vet Rec 85:111-114. Yokomori K et al. 1989. Enterohepatitis in Mongolian gerbils (Meriones unguiculatus) inoculated perorally with Tyzzer's organism (Bacillus piliformis). Lab Anim Sci 39:16-20. Salmonellosis An outbreak of salmonellosis occurred in a colony of 306 3- to 6-week-old gerbils obtained from a supplier in south Florida. Within 5 weeks 95% of the animals had died. Clinical signs included diarrhea, rough coat, weight loss, listlessness and dehydration, but some animals died without previous signs. Necropsy findings were multifocal necrogranulomatous hepatitis and fibrinopurulent peritonitis. Some of the larger hepatic granulomas had mineralization of necrotic centers. Olson GA et al. 1977. Salmonellosis in a gerbil colony. J Am Vet Med Assoc 171:970-972. Listeriosis Not reported in Meriones unguiculatus, but in bushy-tailed jirds (Sekeetamys calurus), disease was characterized by acute deaths without clinical signs. Lesions included necrosuppurative hepatitis, enterocolitis, splenitis, and hepatic and mesenteric lymphadenitis. There also was diffuse acute pneumonitis. Tappe JP et al. 1984. Listeriosis in seven bushy-tailed jirds. J Am Vet Med Assoc 185:1367-1370. Parasites 1. Mites: Demodex sp. mites genus have been found in skin scrapings from gerbils with alopecia and dermatitis, but whether or not the mites were the cause of the lesions has not been established. Liponyssoides sanguineus infestation of Egyptian gerbils (Meriones libycus) has been described as an incidental finding; there was no disease. Levine JF, Lage AL. 1984. House mouse mites infesting laboratory rodents. Lab Anim Sci 34:393-394. Reynolds SL, Gainer JH. 1968. Dermatitis of Mongolian gerbils (Meriones unguiculatus) caused by Demodex sp. Abstract #150, 19th Annual Meeting AALAS; Las Vegas, NV. Schwarzbrott SS et al. 1974. Demodicosis in the Mongolian gerbil (Meriones unguiculatus): a case report. Lab Anim Sci 24:666-668. 2. Other: Syphacia muris and S. obvelata, Hymenolepis sp., Tritrichomo-nas sp., Entamoeba sp. None associated with naturally occurring disease. Dentostomella translucida is an oxyurid of gerbils and hamsters. Heavy infestation can cause mild eosinophilic and lymphocytic enteritis, but no clinical disease is described. Kellogg HS, Wagner JE. 1982. Experimental transmission of Syphacia obvelata among mice, rats, hamsters and gerbils. Lab Anim Sci 32:500-501. Ross CR et al. 1980. Experimental transmission of Syphacia muris among rats, mice, hamsters and gerbils. Lab Anim Sci 30:35-37. Smith GD, Snider TG III. 1988. Experimental infection and treatment of Dentostomella translucida in the Mongolian gerbil. Lab Anim Sci 38:339-340. Vincent AL et al. 1975. Spontaneous lesions and parasites of the Mongolian gerbil, Meriones unguiculatus. Lab Anim Sci 25:711-722. Wightman SR et al. 1978. Syphacia obvelata in the Mongolian gerbil (Meriones unguiculatus): natural occurrence and experimental transmission. Lab Anim Sci 28:51-54. Neoplasms Neoplasms of aged gerbils are among the most commonly reported diseases in this species. Neoplasms of the adrenal cortex, ovary and skin appear to be the most common types. A few of the skin tumors were from the ventral scent gland in males; one of these was malignant. Most tumors occurred in gerbils over 2 years old. Benitz KF, Kramer AW. 1965. Spontaneous tumors in the Mongolian gerbil. Lab Anim Care 15:281-294. Cramlet SH et al. 1974. Malignant melanoma in a black gerbil (Meriones unguiculatus). Lab Anim Sci 24:545-547. Glenn ME, Gray J. 1964. Effect of various hormones on the growth and histology of the gerbil (Meriones unguiculatus) abdominal sebaceous gland pad. Endocrinology 76:1115-1123. Guzm:an-Silva MA, Rossi MI, Guimaraes JS. 1988. Craniopharyngioma in the Mongolian gerbil (Meriones unguiculatus): a case report. Lab Anim 22:365-368. Raflo CP, Diamond SS 1980. Metastatic squamous-cell carcinoma in a gerbil (Meriones unguiculatus). Lab Anim 14:237-239. Ringler DH et al. Spontaneous neoplasms in aging Gerbillinae. Lab Anim Sci 22:407-414. Robinson FR. Gerbil. In Handbook of Laboratory Animal Science, Vol. III. Melby EC Jr, Altman NH (eds.); CRC Press, Inc.; Boca Raton, FL; 1976; pp. 271-273. Rowe SE et al. 1974. Spontaneous neoplasms in aging Gerbillinae. Vet Pathol 11:38-51. Shumaker RC et al. 1974. Tumors in Gerbillinae: A literature review and report of a case. Lab Anim Sci 24:688-690. Troup GM et al. 1969. Life span, chronologic disease patterns, and age related changes in relative spleen weights for the Mongolian gerbil (Meriones unguiculatus). Exp Gerontol 4:139-143. Vincent AL, Ash LR. 1978. Further observations on spontaneous neoplasms in the Mongolian gerbil (Meriones unguiculatus). Lab Anim Sci 28: 297-300. Vincent AL et al. 1979. The pathology of the Mongolian gerbil (Meriones unguiculatus): A review. Lab Anim Sci 29:645-651. Dihydrostreptomycin Sulfate Toxicosis In one case, ascending flaccid paralysis occurred, presumably due to inhibition of acetylcholine release from synaptic membranes resulting from overdose of dihydrostreptomycin sulfate. This antibiotic has a small margin of safety for laboratory rodents. Wightman SR et al. 1980. Dihydrostreptomycin toxicity in the Mongolian gerbil, Meriones unguiculatus. Lab Anim Sci 30:71-75. Miscellaneous Diseases & Lesions 1. epileptiform seizures 2. atherosclerosis 3. diabetes & obesity 4. chronic interstitial nephritis 5. ovarian follicular cysts 6. periodontal disease 7. overgrown incisors 8. trophoblastic emboli 9. aural cholesteatoma Chole RA et al. 1981. Cholesteatoma: spontaneous occurrence in the Mongolian gerbil Meriones unguiculatus. Am J Otol 2:204-210. Henry KR et al. 1983. Age-related increase of spontaneous aural cholesteatoma in the Mongolian gerbil. Arch Otolaryngol 109:19-21. McGinn MD et al. 1982. Cholesteatoma: experimental induction in the Mongolian gerbil, Meriones unguiculatus. Acta Otolaryngol 93:61-67. Ostapoff EM, Morest DK. 1989. A degenerative disorder of the central auditory system of the gerbil. Hear Res 37:141-162. Schiffer SP et al. 1986. Diagnostic exercise: head tilt in a gerbil. Lab Anim Sci 36:176- 177. Vincent AL et al. 1975. Spontaneous lesions and parasites of the Mongolian gerbil, Meriones unguiculatus. Lab Anim Sci 25:711-721. Vincent AL et al. 1979. The pathology of the Mongolian gerbil (Meriones unguiculatus): a review. Lab Anim Sci 29:645-651.