The Syrian Hamster

1. A. Scientific name
   Syrian hamster= Mesocricetus auratus, chromosome # 2N=44
   Chinese hamster= Cricetulus griseus, chromosome # 2N=22
   European hamster= Cricetulus Cricetulus, chromosome # 2N=22
2. History
   Unlike most other laboratory rodents. the origin of current research hamsters is precisely known. Dr. Aharoni of the Hebrew University in Jerusalem collected a litter of 8 in Syria in 1930. One male and 2 females survived and were bred in the laboratory. Quickly became an important model for the study of human visceral leishmaniasis, caused by L. donovani. Hamsters were eventually shipped to the U.S. during WWII.
3. Biology: See attached data sheet
   Highlights
   1. cheek pouches - highly distensible, extend posteriorly from the cheek to the scapulae, - thin walled, well vasculized, and markedly deficient in lymphatic vessels. - used for food storage - immunologically privileged sites for research use
   2. Flank gland (Hip gland) - prominent in male, darkly pigmented in adult male - composed of sebaceous gland, terminal hair and pigment cells - usually covered by haircoat - secrete pheromones, used to mark out territory and contribute to the stimuli determining mating behavior.
   3. Brown adipose tissue: - mainly located between the scapulae. - the main function is to heat the blood passing through it - important for hibernation
   4. Stomach Forestomach:function similar to the rumen, the site of some pregastric fermentation.
   5. Adrenal gland: male is bigger than female
   6. Spleen: male is smaller than female (in contrast to mice)
   7. Harderian gland: present, like rat
   8. Uterus: duplex, each uterine horn having a cervix which communicates directly with the vagina
   9. Teeth - 2(I 1/1, C 0/0, P 0/0, M 3/3)=16 - molar:fixed roots - incisor: open-rooted
   10. Colon and kidney - very long colon and long renal papilla, function in water conservation. - hamsters are desert animals and excrete very thick concentrated urine.
   11. pancreas: diffuse, like rat
4. Reproduction
   Highlights
   1. Mating
      • female is more aggressive than male, the female is always introduced into the males cage to prevent territorial defensive aggressive behavior by the female.
      • mature female ovulates every 4 days, usually around midnight to 1 A.M.after a period of heat. Hand mating should be performed on the 3rd evening after the appearance of post-ovulatory mucus plug.
      • sequential monogamy mating: a series of 7 females is rotated.
      • group mating: 10 to 12 females with 3 to 5 males, careful of fighting. - monogamous pair mating:place a prepubertal female and male together permanently.
   2. Pregnancy
      • confirmed by the absence of the post-ovulatory plug on days 5 and 9 after breeding.
      • short gestation (16 days) (Chinese hamster: 21 days)
      • pseudopregnancy may occur on nonsuccessful breeding.
   3. Maternity care
      • neonate hamsters are very immature, and require nest.
      • cannibalism is common during the first pregnancy and the first week post-partum.
      • Do'nt bother mother and babies between 2 days before and 10 days after birth.
      • fostering is rarely successful.
   4. Post-partum estrus: female is reported to have post-partum estrus, but ovulation does not occur.
5. Caging
   1. Conventional cages are most commonly used, either solid bottom or wire.
   2. Space requirement -19 square inches for adults over 100 gm in body weight.
   3. Males may be housed together, but females will fight if housed together after 2 months of age.
   4. Hamster are escape artists- be sure lids are secure.
6. Environment
   1. Hamsters are nocturnal.
   2. If environmental temperature falls below 480 F, hamsters will hibernate, with a resulting decrease in their basal metabolic rate, body temperature, heart and respiration rate.
7. Nutrition
   1. Hamsters have been maintained very well by feeding commercial rodent diets.
   2. Eat about 12 g, drink 10 ml water per 100 g body weight daily.
   3. Hamsters are also coprophagic, like Guinea pig and rabbit.
8. Handling
   1. Hamsters may be very aggressive, especially females.
   2. Hamsters will often bite if startled or are not used to handling.
   3. May pick up animals by:
      • Grasp over head and shoulders
      • Grasping skin over the back
      • Using containers to pick up and transport
      • Leather gloves are handy to have around
9. Laboratory Procedures
   1. Injections Intravenous (IV) - femoral vein cephalic vein saphenous vein Intraperitoneal (IP) Subcutaneous (SQ) skin over neck Intramuscular (IM) - caudolateral thigh muscles
   2. Blood collection tail tip orbital plexus (anesthetize) cardiac puncture (anesthetize)
10. Pharmacology
    1. Hamsters are very resistant to morphine; reduced response to histamine (anaphylactic shock); sensitive to corticorsteroid.
    2. Antibiotic toxicity like rodent and rabbits. Avoid or limit the duration of penicillin, tetracycline, erythromycin, and lincomycin.
11. Important Characteristics Relating To Major Research Uses
    1. Cheek pouches-thin membranes that can be completely everted and exteriorized for study: a. Vascular research- blood vessels in the cheek pouch are readily visualized after the pouches are everted. b. Tumor growth studies- the cheek pouch has no lymphatic drainage and is termed "immunologically privileged." Thus, iso-, allo-, and xenogeneic tumors will grow on the cheek pouch. Tumors implanted in the cheek pouch can be readily observed.
    2. Predictable, regular female reproductive cycle: Reproductive physiology and endocrinology-the female reproductive cycle and hormone fluctuations have been closely studied. The short 4 day cycling time is useful.
    3. Hibernation at 480F and below: a. Hibernation physiology and metabolic regulation studies. b. Hypothermia studies.
    4. Susceptibility to oncogenic viruses in neonatal hamsters: Experimental infections with human adenoviruses, SV-40, polyomavirus, and others often result in viral-induced tumors. Consequently, many viral oncogenesis studies are performed in hamsters.
    5. Susceptibility to infectious agents: hamsters have been used in studies of many bacterial infections. (salmonella, M. leprae, others). Also sensitive to experimental-induced infection diseases such as leptospirosis, influenza and canine distemper.
    6. Dental caries studies: hamsters have been used in experiments in dental caries production. Diet # 2000 can establish Streptococcus mutant in hamster and produce caries.
    7. Diabetes mellitus: Spontaneous diabetes mellitus in Chinese hamster.
    8. hyperglyceridemia:
    9. cardiomyopathy: BIO 14.6 hamster
12. Brief Summaries of Diseases
    1. Lymphocytic Choriomeningitis Virus-LCM virus is an arenavirus with zoonotic potential. Human outbreaks associated with infected hamster are well known. In humans, LCM usually produces flu like symptoms. However, infections can be fatal. Nearly all neonates and about half of young adults develop persistent viremia and systemic lesions. large amounts of virus are shed in the urine. Screening tests are available. Infected colonies should be destroyed, The incidence of LCM in pet shop hamsters is unknown.
    2. Proliferative Ileitis-Known commonly as "wet tail". One of the more common diseases of hamsters. Diarrhea is the primary clinicalsign. Mortality in weanlings and young can be high. Mucosal hyperplasia and/or hemorrhagic necrosis of the ileum is common. The prevalence of the disease in hamster colonies is unknown because screening tests are not available. There is no effective treatment, but tetracycline therapy has been reported to reduce mortality associated with epizootic. The etiology is unknown, but Campylobactera fetus subspecies jejuni has been isolated from animals in a number of epizootic. Experimental campylobacter infections have not transmitted by feeding ground ileal tissue from affected hamsters, so an infectious etiology is strongly suspected.
    3. Lymphomas Due to a Viroid (non-encapsulated naked DNA):A highly unusual horizontally transmitted mammalian viroid causes epizootic of ;lymphomas. 50-90% of infected young develop lymphomas. Clinical signs include emaciation, lethargy, diarrhea, rectal and abdominal hemorrhages, and SQ lumps. Also seen in infected animals are non-bacterial enteritis, intussusception, pyelonephritis, several hepatic lesions, and warts due to an enzootic papillomavirus. No treatment, no diagnostic tests available. Prevalence unknown.
    4. Antibiotic-Induced Diarrhea:A number of antibiotics (tetracycline, penicillin, erythromycin, vancomycin, clindamycin) may cause gram negative overgrowth in the gut. Other antibiotica can lead to overgrowth of gram positive clostridial difficile that elaborate toxins. High morbidity and mortality can occur due to toxemia. 5). A age related diseases include amyloidosis, chronic nephropathy(high protein diets increase the severity), and polycystic disease.