ALAT Chapter 20 Hamsters PDF

ALAT Chapter 20 Hamsters General USDA regulated? Gestation Weaning Sex determination Maturity Uterus details Dental formula Housing needs Unique physio Common clinical concerns General Clinical Concerns Pathogens Rx Options Zoonotic concerns Sample collection sites Medication admin...

ALAT Chapter 20 Hamsters General USDA regulated? Gestation Weaning Sex determination Maturity Uterus details Dental formula Housing needs Unique physio Common clinical concerns General Clinical Concerns Pathogens Rx Options Zoonotic concerns Sample collection sites Medication admins sites Meds to avoid 1. 2. 3. 4. 5. 6. 7. 8. Can you list one condition hamsters have that would make them a good research model? Size Short gestation Short life span Relative cost Adapt well to surroundings Free of many rodent-related spontaneous diseases Useful for unique conditions; diabeties, cancer research, genetic studies, metabolism, heart disease, dental research Cheek pouch is a useful research tool Infectious disease Behavioral Genetic models of human disease  Cancer  Atrial thrombosis  Caries (aka cavities) and periodontal disease         Muscular dystrophy Teratology Renal physiology Hibernation Reproduction Relatively few spontaneous diseases compared to other lab rodents, but susceptible to many experimentally induced diseases and infections Most commonly used Syrian (golden) hamster Chinese hamster European hamster Armenian hamster Djungarian hamster Biological Data Cheek pouches Stomach = two compartments Scent Gland Delicate GI tract Nocturnal Hibernation The word ‘hamster’ originates from a German word ‘hamstern,’ which translates into ‘to hoard’  Temporary storage of food and bedding (and pups!)  No glands/lymphoid tissue  Rich in mast cells  Highly vascular  Supplied by external carotid artery (branches)  Used for micro-vascular studies:     Inflammation Tumor growth Vascular smooth muscle function Carcinogenic agents  “Immunologically privileged”  Lack intact lymphatic drainage pathway  Decreased Langerhans cells  Will support tissue transplant without rejection Not a tumor Unlike other rodents, the hamster has a stomach that is divided into two compartments.  The non-glandular fore-stomach is joined with the glandular stomach by a narrow passageway.  The tissue of the forestomach is similar to that of a ruminant (such as sheep and cattle).  Some researchers have speculated that the forestomach acts as a fermentation chamber to aid in digestion.  The actual role that the compartmentalized stomach plays in hamster digestion has yet to be determined. The scent gland, or flank organ, is another interesting anatomical feature of the hamster.  These glands are located on both the right and left dorsolateral flanks.  In mature males, these areas are identified by darkly pigmented skin with obvious black, bristly hairs; in females, the hairs are softer and less noticeable.  These glands secrete a musk-like fluid, and are probably related to sexual attraction and territorial marking. Hamsters tend to spend much time grooming the fur around these glands. The intestinal tract of hamsters has a delicate balance of microorganisms. This balance can easily be disrupted by stressors, such as handling by humans or changing feed.    A disruption in the composition of this intestinal flora can cause overgrowth of some microbes that may result in inflammation of the intestinal tract (enteritis). This intestinal sensitivity has research applications, such as creating vaccines for intestinal illnesses. Some antibiotics, such as penicillin, should never be used in hamsters because the disruption of their intestinal flora can be lethal. Hamsters are nocturnal animals, with very distinct biological (circadian) rhythms.  Their hormone levels and the level of other physiological molecules fluctuate predictably throughout the day, and throughout the year.  Careful manipulations of room light cycles and management of the necessary husbandry and research procedures can change their biological rhythms.  Bite when startled – wake carefully  Permissive hibernators  Option to hibernate depending on conditions ▪ Temperature: <41oF ▪ Food supply ▪ Short days, low light intensity  Characteristics:  Narcosis  Sharp reduction in body temp  Reduction in metabolic activity  Depressed vital signs BE SURE THE HAMSTER IS AWAKE BEFORE DISTURBING!!!!  2-3 days of inactivity interspersed with short periods of normal activity Because of their ability to hibernate, hamsters are important models for studies of hibernation and cold adaptation. Hamsters are also used in research on viral diseases, investigating specific metabolic pathways, and for studies of degenerative disease such as cardiomyopathy.      1003 ICPM 1 00 3 Hysodontic incisors Pups are born with erupted incisors!! Hamsters have a unique kind of enamel, normally yellowish-orange to brown. The older they are, the darker their teeth get. So it’s even possible to tell how old a hamster is by the darkness of its teeth. Weight @ maturity: 250-500 grams Syrian = 110140gms Djungarian = 1850gms Life span 1.5 -2 years Body temperature 98.6 – 100.4F Heart rate: 250-500bpm Respiratory rate: 35-135 breaths per min Water Consumption 8-10mls/100gms Food Consumption 10-12 grams Broad muzzle = challenges Urine output 7mls Milky white d/t calcium carbonate  Male (boar)  Pointed posterior ▪ Inguinal canal fat pads ▪ Fat pads usually cause testes to remain in abdomen  Longer anogenital distance  Female (sow)  Rounded posterior  Nipples  Shorter anogenital distance Short AG distance Longer AG distance   Sexual maturity: 4-6 weeks Estrus: 4-5 day cycle  Lasts 8-26 hours  Gestation: 15-18 days (shortest of any other lab animal)     Seasonal polyestrous Day 10: Female looks pregnant Will hide pups in cheek pouches when disturbed DND till ~Day 7    Aggressive animals Can’t mate as we do with mice To avoid fighting:  Pair-bond at weaning  Or introduced when the female has reached estrus. Post-ovulatory discharge is indicative of the animal having reached estrus the day before and is predictive of the next estrus 3 days after its appearance.  Female hamsters can be successfully mated in the evening of the 3rd day following the post-ovulatory discharge. Four different mating systems are used for hamsters: hand, harem, intermittent, and monogamous pair mating. • Hand breeding: A female is introduced in the cage of a male at the beginning of the dark cycle. If no copulation occurs within 5 minutes, or if the female becomes aggressive, she is removed from the cage. If copulation occurs, she can be left in the cage until the following light cycle begins. A vaginal plug should be visible for a few hours following copulation. • Harem mating: A male and two or three females are housed together. The pregnant females are removed from the cage at least 2 days before parturition and housed separately until their litter is weaned. Fighting may occur when females are returned to the group cage. • Intermittent mating: Females are sequentially placed one after another into the cage of a male for a week. They are then moved to a separate cage to give birth or until it is determined that they are not pregnant. • Monogamous pair mating: One male and one female are housed together immediately after weaning, before they become aggressive. When successful, monogamous mating can produce a litter every 35 to 40 days, beginning about 30 days after the pairing.     Burrowing/tunneling Nest building Gnawing, chewing Solitary except when mating or when weaned together  Fighting common in social groups  Females dominate males  Larger hamsters dominate smaller ones  Monitor new groups carefully Wake up carefully! 1. Can pick up by grasping the loose skin across its shoulders 2. Use your hands as a scoop to transfer it from one cage to another 3. Place a small container in the cage. A hamster will usually crawl into the container and can then be transferred from one cage to another. A hamster can be restrained by gently grasping the loose skin across the back. 1. Place the hamster on a flat surface, such as a cage top. 2. Then press the palm of one hand gently against its back with your fingers straight. 3. Your fingers and thumb can then curl around opposite sides of the hamster, gathering in as much loose skin as possible.  Bunching the loose skin tightly in your hand will pull the skin taut against the hamster’s abdomen and thorax.  The animal should not be held so tightly that it is unable to breathe, nor should it be held so loosely that it can turn its head and bite the handler. Hamsters are a USDA-regulated species; therefore, housing, husbandry, and recordkeeping are governed by the Animal Welfare Act and Regulations.  Hamsters are usually housed in microisolation caging or static cages that are at least 6 inches high.  Since they like to burrow and create sleeping areas, contact bedding should be provided in the cage.  Hamsters are adept at escaping from cages, so the cage top should be secured firmly to the cage. There should be no cracks or holes in the cages; hamsters will gnaw their way out if given the opportunity.  House at temperatures and humidity levels that are similar to those for rats and mice.       Standard rodent diet, ad libitum May struggle to eat from overhead hoppers due to broad muzzle Weanlings may not be able to reach hopper PRN - Feed on floor of cage with IACUC approval Coprophagic Will chew plastic H2O bottles Hamsters use any items that they can climb through, into, and on, such as boxes, tubes, and shelters. Likes: exercise wheels, wire bars, and cage lids for climbing. What type of enrichment would they find meaningful? In the wild, hamsters burrow extensively. Varying sizes and types of bedding substrates will facilitate their burrowing and nest-building behaviors and should be provided when possible to allow expression of natural behaviors.            Hunched posture Eye squinting Tightened whiskers Ear position changes Ruffled hair coat Weight loss Poor body condition Lethargy Dyspnea Soft stool/diarrhea Death of young animals Facial grimace scales are being developed as we speak      Euthanasia methods for hamsters include cervical dislocation and exposure to high levels of inhalant gases, such as carbon dioxide or isoflurane. An overdose of barbiturates administered intraperitoneally is also a commonly used method. In all cases, those performing euthanasia must be trained and proficient in the correct techniques. As with other species, death must be verified; your institution’s SOPs may require an additional procedure to be performed. Carcass disposal should be according to the facility’s guidelines.