Key Points
- Enterocolitis is the most important cause of morbidity and mortality in hamsters.
- “Wet-tail” is a non-specific clinical sign that can result from enterocolitis and resultant diarrhea in pet hamsters.
- The etiology of enterocolitis may be multifactorial in hamsters of all ages including bacteria such as Clostridium spp. and Campylobacter jejuni and parasites, particularly Hymenolepis nana, and even fungal agents.
- Many of the potential pathogens of “wet-tail” are zoonotic.
- Clinical outbreaks of diarrhea in hamsters may be precipitated by stress, including high temperatures or humidity, overcrowding, malnutrition, dietary changes, shipping, or underlying diseases, such as endoparasitism.
- Prevention and treatment of “wet’-tail”, which centers around the use of antimicrobials, husbandry practices, selective breeding, and culling, have generally proved unrewarding.
Introduction
Diarrhea is the most common problem in pet hamsters. In a recent survey of two large American commercial breeding facilities, approximately 3% of shipped hamsters develop diarrhea. Diarrhea caused by enterocolitis can occur in hamsters of any age or breed and is commonly known as “wet-tail” (Fig 1). Clinical signs in weanlings usually include diarrhea, anorexia, ruffled hair, dehydration, weight loss, and death. The mortality rate is often highest in 3-10 week old hamsters, however adult hamsters may also suffer debilitating disease and death.

Figure 1. “Wet tail” or diarrhea in a hamster (Mesocricetus auratus). Photograph by Dr. Lauren Richey. Click image to enlarge.
Etiology
The cause of enterocolitis (Fig 2) may be multifactorial in hamsters, involving bacterial, parasitic, and even fungal etiologic agents. A number of the pathogens documented in hamsters are also transmissible to humans. Clinical outbreaks may be precipitated by stress, such as high temperatures or humidity, overcrowding, malnutrition, dietary changes, shipping, or underlying disease, such as endoparasitism.

Figure 2. Gross appearance of enterocolitis in a hamster (Mesocricetus auratus). Photograph provided by Dr. Lauren Richey. Click image to enlarge.
Bacteria
Historically, enterocolitis or “wet-tail” has been associated with proliferative ileitis caused by Lawsonia intracellularis, however there was no evidence of proliferative ileitis in studies by Barron et al or Motzel et al. Other bacteria that have been implicated in “wet-tail include Clostridium spp., E. coli, Campylobacter jejuni, Helicobacter aurati, Salmonella spp., and Pasteurella pneumotropica. In a recent survey of two large American commercial breeding facilities, the most clinically significant infections were with species of Campylobacter and Clostridium. Clostridium piliforme is a gram-negative, spore-forming, obligate intracellular bacterium and the causative agent of Tyzzer’s disease. Clostridium difficile has also been associated with enterotoxemia, typhlitis and enteritis in hamsters (Fig 3).

Figure 3. Histologic appearance of Tyzzer’s disease in a hamster (Mesocricetus auratus). Photograph provided by Dr. Lauren Richey. Click image to enlarge.
Parasites
Concurrent mild to severe infections with the tapeworm, Hymenolepis nana, are very common in hamsters with bacterial enterocolitis (Fig 4). As the degree of disease and debilitation increase, so does the tapeworm burden. In some individuals, the tapeworm load is high enough to nearly obstruct the intestines. The protozoa Giardia, Entamoeba, Spironucleus muris, and trichomonads are also variably found in affected individuals.

Figure 4. Gross appearance of the tapeworm, Hymenolepsis nana, from a hamster (Mesocricetus auratus). Photograph provided by Dr. Lauren Richey. Click image to enlarge.
Fungal
The yeast Torulopsis sp. (Candida sp.) can heavily colonize the stomach of hamsters.
Control
Prevention and treatment of “wet’-tail” has historically centered around antimicrobials, husbandry practices, selective breeding, and culling. Unfortunately this approach is rarely rewarding because of the intracellular nature of C. piliformeand the acute progression of Tyzzer’s disease.
Bacterial spores are quite stable and can remain infectious for 1 to 2 years. Control of enterocolitis in a commercial breeding facility would ideally involve depopulation, rigorous disinfection, and repopulation with C. piliforme-free breeding stock.
Care of the individual patient relies upon antibiotic therapy and supportive care. Begin oral antibiotics such as sulfa-trimethoprim (Bactrim®, Roche) at 30 mg/kg PO q12h or enrofloxacin (Baytril®, Bayer) 5-10 mg/kg PO q12h. Depending on the clinical status of the patient, subcutaneous fluids and nutritional support may also be indicated.
Theorizing that high worm burdens make the gut more vulnerable to bacterial infection, Barron et al treated weanling hamsters with praziquantel (Droncit®, Bayer) 20 mg/kg PO, repeat in 10d and fenbendazole (Panacur®, Hoechst) 20 mg/kg PO q24h x 5d prior to shipping. (Note: Napa Nectar™ Plus is a useful and easy way to administer fenbendazole to large hamster colonies). Unfortunately this treatment regimen made no significant difference when compared to control animals.
Summary
“Wet-tail” is a non-specific clinical sign that can result from enterocolitis and resultant diarrhea in pet hamsters. Unfortunately enterocolitis is the most important cause of morbidity and mortality in hamsters. The cause of enterocolitis may be multifactorial in hamsters of all ages and may include bacteria such as Clostridium spp. and Campylobacter jejuni and parasites, particularly Hymenolepis nana. Clinical outbreaks of diarrhea in hamsters may be precipitated by stress, including high temperatures or humidity, overcrowding, malnutrition, dietary changes, shipping, or underlying diseases, such as endoparasitism. Prevention and treatment of “wet’-tail”, which centers around the use of antimicrobials, husbandry practices, selective breeding, and culling, have generally proved unrewarding.
Acknowledgement: I thank Dr. Lauren Richey who was instrumental in the study referenced below (Barron et al) and who also provided the photographs provided above.
References
References
Alworth L, Simmons J, Franklin C, Fish R. Clostridial typhlitis associated with topical antibiotic therapy in a Syrian hamster. Lab Anim 43(3):304-309, 2009.
Barron HW, Richey L, Hernandez-Divers S, Ritchie B. Etiology, pathology, and control of enterocolitis in a group of hamsters. Proc Annu Conf Assoc Exotic Mammal Vet 2007. Pp. 123-126.
Chang J, Rohwer RG. Clostridium difficile infection in adult hamsters. Lab Anim Sci 41(6):548-552, 1991.
Dillehay DL, Paul KS, Boosinger TR, Fox JG. Enterocecocolitis associated withEscherichia coli and Campylobacter-like organisms in a hamster (Mesocricetus auratus) colony. Lab Anim Sc 44(1):12-15, 1994.
Donnelly TM. Disease problems of small rodents. In: Quesenberry KE, Carpenter JW (eds). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. 2nd ed. 2003.
Frisk DC, Wagner JE, Owens DR. Hamster (Mesocricetus auratus) enteritis caused by epithelial cell-invasive Escherichia coli. Infect Immun 31(3):1232-1238, 1981.
Lesher RJ, Jeszenka EV, Swan ME. Enteritis caused by Pasteurella pneumotropica infection in hamsters. J Clin Microbiol 23(3):448, 1985.
Motzel SL, Gibson SV. Tyzzer’s disease in hamsters and gerbils from a pet store supplier. J Am Vet Med Assoc 197:1776-1778, 1990.
Patterson MM, Schrenzel MD, Feng Y, Fox JG. Gastritis and intestinal metaplasia in Syrian hamsters infected with Helicobacter aurati and two other microaerobes. Vet Pathol 37(6):589-596, 2000.
Percy DH, Barthold SW. Hamster. In: Pathology of Laboratory Rodents and Rabbits, 2nd ed. Ames, Iowa. Iowa State University Press; 2001.
Barron H. Enterocolitis in hamsters. February 25, 2010. LafeberVet Web site. Available at https://lafeber.com/vet/enterocolitis-in-hamsters/