Chapter 5. Biology and Diseases of Hamsters Flashcards
1
Q
What is the scientific classification of hamsters?
A
Order Rodentia, Suborder Myomorpha, Superfamily Muroidea, Family Cricetidae
Animals in this family characterized by large cheek pouches, thick bodies, short tails, excess of loose skin
2
Q
What is the dental formula of hamsters?
A
(I 1/1, C 0/0, PM 0/0, M 3/3) x 2 = 16
Incisors erupt continuously
Cuspidate molars that do NOT continue to grow
3
Q
Describe the Syrian or golden hamster (Mesocricetus auratus).
A
Originated in Syria and naturally lives in arid, temperature regions of southeast Europe and Asia Minor
Lives in deep tunnels that provide cooler temps and high humidity
Nocturnal in the laboratory, but females may be diurnal in wild
Adult Syrian hamster: 6-8 inches (14-19 cm); 110-140 gram weight; females tend to be larger than males
Males can be identified by prominent flak glands and by large testicles that protrude on either side of tail
4
Q
Who initiated the use of the golden hamster in research?
A
Saul Adler. Looking for a laboratory animal susceptible in infection with Leishmania
Almost all Syrian hamsters in laboratories originated from one litter captured in Syria in 1930; 3 littermates retained in captivity and their progeny first imported in US in 1938; lab use of hamsters grew to a peak in early 1970s and then declined
5
Q
What cancers are golden hamsters used to study?
A
Oral tumors - cheek-pouch carcinogenesis model
Pancreatic ductal adenocarcinoma - administered nitrosamines or a transplantable cell line
Respiratory tract tumors - administered carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) to w/ or w/out hypoxia to develop nonsmall cell lung carcinoma
Disease process of Simian virus 40 (SV40), a polyomavirus - hamsters develop variety of tumors based on route of inoculation and age of hamster
Effect of exogenous estrogen compounds on tumor development - 100% male hamsters developed renal tumors in one study when administered estrogens
Hamsters are one of few animal models that permit the replication of human adenoviruses
6
Q
What metabolic syndromes are golden hamsters used to study?
A
Cholesterol cholelithiasis - induced via excess dietary cholesterol or sucrose-rich diet
Diabetes mellitus - induce with streptozotocin (STZ) or alloxan; giving nicotinamide IP 15 min before STZ results in partial protection against betacytotoxic effect of STZ and partial presevation of insulin stores; also induce with high fat, modest cholesterol diet - induce diabetes in 2 wks w comorbidities like obesity, hyperinsulinemia, hyperleptinemia, hypercholesterolemia, hypertriglyceridemia
Diabetes with nephropathy and coronary lesions - Syrian hamsters of albino-panda-albino (APA) strain when injected with STZ
Atherosclerosis - Syrian hamsters possess similar lipid metabolism to humans; induced via diet
7
Q
What cardiovascular diseases are golden hamsters used to study?
A
Cardiomyopathy - naturally occurring in Syrian hamsters, inherited, model for both hypertrophic and dilated cardiomyopathies; both DCM & HCM in hamsters caused by defect in sarcoglycan gene, a component of the dystrophin complex
Cardiomyopathic hamster lines - original polymyopathic line 1.50, BIO 82.62, BIO TO-2, BIO 53, UMX-7.1
Some strains characterized by significant cardiac hypertrophy, some by ventricular dilation without hypertrophy, some compensatory hypertrophy progressing to left ventricular dilation
8
Q
What infectious diseases are golden hamsters used to study?
A
Hantavirus pulmonary syndrome
Coronavirus severe acute respiratory syndrome (SARS)
Fungal infections incl Histoplasma spp. - sensitive to small inocula; most fungi grow in spleen, liver, and LNs
Mycoplasma pneumoniae - models of localized infx in respiratory tract
Mycobacteria spp., Clostridium difficile, Treponema pallidum, Toxoplasma spp., Babesia spp., leprosy, atypical TB, leptospirosis
Prions - susceptible to scrapie - prions replicate to high titers in brains of hamsters, transmissible mink encephalopathy (TME), Creutzfeldt-Jakob disease, Gerstmann-Staussler syndrome (GSS) - cause slow progressive degenerative diseases in the CNS; Hamsters develop amyloid-like deposits in their brains that may be similar to amyloid in human Alzheimer’s
9
Q
What other various diseases are golden hamsters used to study?
A
Chronic obstructive pulmonary disease (COPD) & emphysema - induce w/ single intratracheal dose of porcine pancreatic elastase or a copper deficient diet
Gastropathy due to NSAIDs
Assessment of human fertility - hamster oocyte penetrable to human spermatozoa = zona-free hamster oocyte assay - analyzes ability of sperm to capacitate eggs, undergo acrosome reaction, and fuse with oocyte; becoming less popular with development of new techniques like intracytoplasmic sperm injection
10
Q
What are neonatal developmental milestones for hamsters?
A
Incisors are visible at birth; weight 2-3 g at birth
Ears open at 4-5 days, hair growth first noted day 9, eyes open at 14-16 days
Weaned at 21 days & weigh 35-40 g
Maturity at 6-8 weeks - males weigh 85-110 g and females 95-120 g
11
Q
What is the reproductive life span for hamsters?
A
Begins at 6-8 weeks & continues until 14 months old
12
Q
What is the life span of hamsters?
A
Average 2 years (18-24 months), up to 3 years.
Average female life span may be markedly shorter than males, depending on strain and source
13
Q
When is the optimal time in gestation of hamsters for teratogenic studies?
A
Day 8 of pregnancy - hourly development of the fetus can be observed
14
Q
Describe the cheek pouches of hamsters.
A
Non-glandular, contain lots of mast cells, highly vascular, lined with stratified squamous epithelium.
Blood supply comes from branches of external carotid artery - supplied by 6 small arteries in the neck and face
Pouches can be easily everted - used to study microvascular studies of inflammation, tumor growth, vascular smooth muscle function, ischemia reperfusion
“Immunologically privileged” b/c lack intact lymphatic drainage - surface density of Langerhans cells markedly decreased in pouches - will support growth of foreign tissue without immunological rejection
15
Q
What influences development of caries in hamsters?
A
Retention of fine food particles between crown teeth, amount of carbohydrate in diet, form of carbohydrate in diet, vitamins (+/-) in diet; possibly infectious bacteria transmissible between rodents orally
16
Q
Describe the stomach of hamsters.
A
Glandular stomach and nonglandular forestomach, separated by the incisurae of the greater and lesser curvatures.
Nongladular forestomach similar to ruminant stomach, with elevated pH and microflora that contribute to digestion through fermentation
17
Q
What neoplasias can occur in the GI tract of hamsters?
A
Depends on age, strain differences, breeding environment, diet, and other unknown factors.
Two studies showed high incidence of spontaneous neoplasms in the GI tract, others did not confirm.
Experimental induction of papillomas, adenocarcinoma in forestomach and intestines, adeomatous polyps in the colon
18
Q
How do Syrian hamsters respond to intragastric administration of purified cholera enterotoxin?
A
Intraluminal accumulation of fluid in small bowel, cecum, proximal colon.
Historical model to study pharmacological agents, like indomethacin, polymyxin B sulfate, glucose electrolyte solutions, and colchicine that may inhibit intestinal fluid secretions
19
Q
Describe the pancreas and gallbladder of hamsters.
A
Major pancreatic ducts join the common bile duct shortly before it enters the duodenum.
Anatomical configuration is similar to that of mice and rats, but distinct from other mammals including humans.
Syrian hamster can serve as model for pancreatic carcinogenesis - most commonly induced by SC nitrosamines; transplantable cell line (PGHAM-1) can also reproduce metastatic pancreatic cancer
20
Q
Describe the pulmonary system of the Syrian hamster.
A
Conductive airways contain a limited number of glandular structures, primarily in the proximal trachea, which facilitates modeling chronic bronchitis.
Pulmonary vascular bed is similar to that of humans; hamsters develop pulmonary lesions that resemble human centrilobular emphysema when given intratracheal porcine pancreatic elastase
Spontaneous bronchiogenic and pulmonary cancers are rare = Syrian hamsters are good model to study chemical carcinogenesis in resp tract
21
Q
Why is the Syrian hamster kidney highly responsive to estrogen?
A
Their reproductive and urogenital tracts develop from the same embryonic germinal ridge.
Administration of estrogen to males leads to renal tumors - model of effects of exogenous estrogenic compounds on tumor development
Hamsters one of most reliable models for effect of chemical carcinogens on the urinary bladder
22
Q
Describe endocrine system of hamsters.
A
First model reported with equivalent of Addisonian adrenal necrosis.
Adrenals show distinct size difference by 4 weeks of age, depending on sex - males have greater number of reticular cells within the adrenal cortex = double size adrenals compared to females
23
Q
Why do hamsters not reject skin allografts to same extent as other laboratory animal species?
A
Littermates have very little alloantigenic variation & few mutational changes have occurred in their defined gene pool While there is diversity at the MHC class II locus, the region is likely similar among the strains of Syrian hamsters available in research
24
Q
Describe immunoglobulins (Ig) in hamsters.
A
Thymic system and associated cellular immunity development delayed in Syrian hamsters compared to other rodents.
Only 4 of the 5 Ig have been described in hamsters - IgM, IgG, IgA, and IgE (IgD remains to be defined; at least two inbred strains are deficient in the sixth component of complement)
Another IgG isotype, IgG3 has been isolated from some strains of inbred Syrian hamsters - IgG3 different from IgG1 and IgG2 by its affinity for protein A; immunodeficiency has NOT been linked to deficiencies in IgG3.
First crystal structure of a hamster IgG Fab fragment and the complete cDNA sequence of the stimulatory Ab HL4E10 (contains first examples of hamster lambda light chain) has been identified.
-HL4E10 Ab is uniquely costimulatory for γδ T cells - humanized versions may be of clinical relevance in treating γδ T cell dysfunction-associated dz, such as chronic non-healing wounds and cancer
25
Describe Harderian glands in hamsters.
Pigmented lacrimal glands located posterior to the ocular globes - release a lipid and porphyrin-rich material that lubricates eyes and eyelids
Also site of immune response, source of thermoregulatory lipids and pheromones, photoprotective organ, part of the retinal-pineal axis
Marked sexual dimorphism in Syrian hamsters (NOT Chinese, Armenian, or Djungarian) - females secrete up to 10^3 times more porphyrin than males & diffs in type of lipid droplets secreted; glandular dimorphism androgen-dependent & has seasonal variation
26
Describe flank glands in hamsters.
Coarse hair over darkly pigmented skin in the costovertebral area in males - marks dermal structures composed of sebaceous glands that produce secretions in response to androgens - when male sexually excited, hair may appear wet and hamster may seem pruritic - secretions likely for territorial marking
-Females also have dorsal sebaceous glands, but they are not assoc w/ estrous cycle and are harder to identify
27
Describe hibernation in hamsters.
Hibernation ability varies among species and individual animals.
Exposure to cold stimulates hamsters to gather food; will hibernate at ~5 C +/- 2 C.
European hamster is a TRUE hibernator; Syrian hamster may no reliably enter hibernation at cold temps & bouts of hibernation may be short
Cold exposure and hibernation in the hamster are assoc w/ desaturation of white fat = useful for studies of factors controlling saturation of fat
28
Describe genetic mutations in Syrian hamsters.
Have diploid chromosome number of 44.
18 mutations of coat and eye color (incl brown, cream, piebald, and white hamsters); 6 mutations of neuromuscular system; 6 mutations of quantity or texture of hair
In 2014, first successful transgenic hamsters created & hamster embryonic stem cell lines have also been created.
29
What is the typical daily food intake for Syrian hamsters?
5.5-8.9 g. Hamsters are typically feed commercial rodent (mouse and rat) feed; they have normal growth and reproduction on these diets.
30
Describe differences in hamster nutritional needs vs. mice and rats.
- Soybean meal offers better nutritional efficiency than fish meal for hamsters
- Carbs in diet can induce change in both glucose and lipid metabolism
- Increased requirements for dietary zinc, copper, and potassium compared to rats
- Require sources for many B vitamins and non-nutritive bulk
- Require Vitamin E to prevent myocytolysis (Vit E deficiency plus oxidative stress may play a role in heart disease in hamsters); Vit E can also reduce fatty streak accumulation in hypercholesterolemic hamsters
- Increased rates of survival linked to 20g lacalbumin/100g food
- Can be susceptible to colocolic intussusception within 7-10 days of changing to a semipurified feed
31
Why must hamsters have feed placed on the floor?
Broad muzzle - feed hoppers not recommended for hamsters, or must be able to allow feed pellets to drop through to cage floor.
- Placement of feed on floor acceptable per federal regulations (CFR 2013)
- Hamsters start to eat solid dry food at 7-10 days of age
32
What is the typical daily water intake for hamsters?
8. 5 mL/100 g body weight
- Provide stainless steel water bottle sippers, b/c hamsters can bite through glass or plastic
- Sipper must be low enough to be accessed by the smallest animal in the cage - nursing pups benefit from water, in addition to milk, to prevent GI issues
33
Describe unique pharmacology responses in hamsters.
- More sensitive to metabolic effects of corticosteroids
- Less sensitive to histamine
- Very resistant to morphine - no sedative or hypnotic effect
- Susceptible to Clostridium difficile overgrowth following administration of lincomycin, clindamycin, ampicillin, vancomycin, erythromycin, cephalosporins, gentamicin, penicillin
34
When does sexual maturity begin in hamsters?
Males - ~90g body weight
Female - 6-8 weeks; recommend wait to breed until 90-100 g weight
-Copulation can begin as young as 4 week, but pregnancy unusual before 8 wks
-Reproductive capacity for both genders decreases at ~14 months; senescent females can often breed with younger males, w/ notable increase in defective ova and decreased offspring produced
35
Describe the estrous cycle in hamsters.
4 days in length
- End of ovulation (usually day 2) noted by copious postovulatory vaginal discharge
- Can be successfully mated on day 3 of cycle
36
How should hamster mating pairs be established?
House individually for at least 1 wk - male establish cage dominance and female cycle normally
3rd day of cycle introduce female to male's cage 1-2 hr prior to start of dark cycle - females are receptive for ~16 hr from early evening until mid-afternoon next day
-If mating does not occur within 5 min or female is aggressive, remove female and try pairing a different female
-If mating occurs, pair can be left together until following light cycle; ovulation and fertilization generally occur during early morning hours, and the day of separation is considered day 1 of gestation
-Hamsters can be trio bred w/ 1 male and 2 females in cage for 1-2 weeks - to reduce aggression males should be older than females; check daily for fight wounds
37
What is gestation length in hamsters?
15-18 days
- After mating female moved to nesting cage for at least 2 days prior and 10 days after parturition; minimize disturbance during pregnancy - both to minimize maternal rejection or cannibalization
- No recent accounts of successful cross-fostering of hamsters and bottle feeding rarely successful
- Females can experience pseudopregnancy after infertile mating - is discharge present on days 5-9 after mating = NOT pregnant; pregnant hamsters have distinct weight gain w/ abdominal distension ~10 days after mating
38
Describe parturition in hamsters.
Just prior, females become restless & eat, groom, and nest-build
- Increased respiratory rate = litter in next several hours
- Most common day of parturition is 16 days gestation & parturition lasts for more than 3 hr
- Syrian hamsters display abrupt change to maternal behavior in late gestation (unlike gradual onset in mice and rats)
39
Describe development and management of hamster pups.
- Litter size range: 4-12 pups (6-8 most common)
- Possible to sex pups are birth, but preferable to leave cage undisturbed for 7-10 days; if cage must be disturbed - provide food pellets on cage floor for dam to stuff cheek pouches - may reduce cannibalism of pups; dam may put pups in cheek pouch if stressed and then remove them when calm
- Pups remain with dam until at least 19 days old
- Normal weaning is 21-28 days
- Dam estrous cycle does not resume for 1-8 days after parturition
- Young from different litters can be housed together until 40-50 days old, then need to separate d/t aggression in females; males from same litter can be kept together longer
40
What are required cage space dimensions for hamsters?
60 g or less: 10 in^2 floor space
>60 g: 13-19 in^2 depending on body weight
Female with litter: ~121 in^2
Cage height must be 6 inches from cage floor to cage top
41
Describe bedding/caging preferences of hamsters.
Essential to have solid floor for nesting females and young
- Prefer pine shavings over aspen shavings & corn cob and aspen shavings preferred over wood pellets when no nesting material; preferences eliminated when nesting material (paper towel) provided
- Aromatic hydrocarbons in bedding/nesting materials can induce nonspecific hepatic enzymes in hamsters
- Urine output is slight & typically use one corner of cage for elimination
- Provide some sort of burrow or shelter to mimic natural underground burrows; nest material recommended; more burrowing behavior if deeper bedding (40-80 cm depth) vs. shallow (10 cm depth)
- 12-14 hr light cycle; 14 hr required for breeders
42
What are housing temperature, humidity, and lux level recommendations for hamsters?
68-79 F
30-70% humidity
323 lux (30 foot candles) at 1 m above the floor recommended for rodents
-Hamsters fairly adaptable to cooler temps - pre-hibernation hamsters can prefer temps around 8 C (46 F)
43
What is the causative agent of proliferative enteritis (transmissible ileal hyperplasia) in hamsters?
Also called regional enteritis, enzootic intestinal adenocarcinoma, 'wet tail'
Extremely contagious; high morbidity and mortality
Lawsonia intracellularis - G(-), nonspore forming, slightly curved rod (1.5 x 0.35 μm); obligated intracellular bacterium; causes proliferative enteropathy in pigs, ferrets, horses, deer, and rabbits
44
What are clinical signs of proliferative enteropathy in hamsters?
Watery diarrhea - moist matted fur of tail, perineum, ventral abdomen
Dehydration, inactivity, hunched appearance (abdominal pain), abdominal distension, hypothermia, convulsions just prior to death, rectal prolapse, intussusception
Mortality 50-90%, usually within 48 hr of onset of clinical signs
Chronic cases also reported with mild diarrhea and weight loss
May also be self-limiting without clinical signs
45
How is proliferative enteritis transmitted in hamsters?
Fecal-oral
Increased severity and development of disease has been assoc w/ overcrowding, transport, surgery, limited and purified diets, transplantation of neoplasms, experimental leishmaniasis
Cross-species transmission has occurred experimentally between swine and hamsters
Vertical transmission has not been evaluated, but unlikely that L. intracellularis can cross placenta
Unknown how long L. intracellularis survives in environment
46
What are necropsy findings of proliferative enteritis in hamsters?
Gross: segmental thickening and congestion of ileum, enlargement of mesenteric lymph nodes, peritonitis, adhesions
Histology: hyperplasia of columnar mucosal epithelial cells in the terminal ileum, proliferation of glandular epithelium, lymphadenitis with lymphoid hyperplasia, edema, leukocytic infiltration of sinusoids; intestinal crypts may be lengthened with increased mitosis, decreased numbers of goblet cells, and villar atrophy
-L. intracellularis can often identified using Warthin-Starry silver stain in the apical cytoplasm of crypt enterocytes
47
How is proliferative enteropathy diagnosed in hamsters?
Weanlings are very susceptible - become less susceptible by 6 weeks & resistant to infx by 10 weeks
- Ileum lesions develop in 2 phases: hyperplasia that begins as focal lengthening of villi; ~3 wks following transmission, inflammatory phase with focal necrosis of crypt epithelium
- Particulate bacterial antigen can be detected by immunoperoxidase staining or in situ hybridization in the cytoplasm of mucosal epithelial cells
- Proposed model of bacterial entry: bacteria attach to microvillus brush border - ingestion by endocytosis - release from vacuoles into the cytoplasm of cell - bacteria multiple within cell prior to cell rupture
- Serum antibodies specific for intracytoplasmic antigen
- PCR of feces
48
What are differential diagnoses for proliferative enteritis in hamsters?
Tyzzer's disease (Clostridium piliforme), Clostridium difficile enterotoxemia, salmonellosis
-Described changes in ILEUM are pathognomonic for proliferative enteritis
49
What are prevention, control, and treatment strategies for proliferative enteritis in hamsters?
Only purchase from vendors with acceptable health history
Isolate hamsters with diarrhea
Treatment: correct nutritional and electrolyte imbalances; moderate success with antibiotics - tetracycline (10 mg/kg PO Q12 5-7 days), enrofloxacin (10 mg/kg PO Q12 5-7 days), and trimethoprim-sulfa combinations (30 mg/kg PO Q12 5-7 days) - can be added to drinking water
Colony depopulation, facility sanitation, repopulation with uninfected hamsters
50
What are research complications of proliferative enteritis in hamsters?
Enteritis, 20-60% morbidity, ~90% mortality
51
What are prevention, control, and treatment strategies for proliferative enteritis in hamsters?
Only purchase from vendors with acceptable health history
Isolate hamsters with diarrhea
Treatment: correct nutritional and electrolyte imbalances; moderate success with antibiotics - tetracycline (10 mg/kg PO Q12 5-7 days), enrofloxacin (10 mg/kg PO Q12 5-7 days), and trimethoprim-sulfa combinations (30 mg/kg PO Q12 5-7 days) - can be added to drinking water
Colony depopulation, facility sanitation, repopulation with uninfected hamsters
52
What are clinical signs of Tyzzer's disease in hamsters?
Roughened hair coat, diarrhea, high mortality in animals that tend to be of weaning age or immunosuppressed
53
What is the causative agent of Tyzzer's disease?
Clostriium piliforme - spore-forming, intracellular bacterium
Fecal-oral transmission
Has only been sporadically reported in hamsters, but transmission to hamsters is possible whenever housed near susceptible spp (rats, rabbits, gerbils, cats, rhesus monkeys, dogs, horses, guinea pigs)
54
How is Tyzzer's disease diagnosed in hamsters?
Necropsy lesions: enterocolitis, lymphadenitis, multifocal necrotizing hepatitis; hepatomegaly; loss of intestinal tone and serosal edema; hyperemia and hemorrhage in some cases
Diagnosis: organism in tissues, particularly epithelium and smooth muscle cells of the ileum, cecum and colon - Giemsa or silver stainin
Infection in hamsters may not always have clinical signs; can see localized lesions in intestines, liver, cardiac muscle with or without intestinal involvements
55
What are control and treatment measures for Tyzzer's disease in hamsters?
Sanitation and isolation - elimination of bacteria critical to containing an outbreak
Tx usually not done; oxytetracycline added to water in pet store hamsters WITHOUT success
56
Describe causes of Clostridium difficile overgrowth in hamsters.
Antibiotic-associated enteritis - lincomycin, clindamycin, ampicillin, vancomycin, erythromycin, cephalosporins, gentamicin, penicillin
Stress, experimental manipulation, heavy environmental loads of C. difficile
Hamsters on high fat and high cholesterol diets for atheroscleosis models - diet alterations may change GI microflora, pH, and ability to mount immune responses
57
Describe pathogenesis of Clostridium difficile in hamsters.
Causes entercolitis due to alterations in GI microflora; diarrhea & lesions of cecitis; sudden death with or without GI signs
Thought that cecal dysbiosis results in cecal hyperplasia, overgrowth of the bacteria, and resultant necrotizing cecitis
-Case of toxigenic, cytotoxin B-positive C. difficile resulting in profuse, hemorrhagic diarrhea highly asso w/ mortality
-Histo: typhlitis and colitis
58
Describe control of Clostridium difficile in hamsters.
- Development of antibodies against the virulence factors, toxins A and B, has proved useful in preventing disease relapse and subsequent reinfection
- Control of an outbreak: depopulation, decontamination of animal rooms with chlorine dioxide, repopulation
- Experimental infx of hamsters with C. difficile is a model of human disease
59
Helicobacter species in hamsters.
Helicobacter spp. are G(-), curved to fusiform bacteria
Hamsters naturally colonized with several spp - H. cinaedi, H. mesocricetorum, H. cholecystus, H. aurati, and a novel sp in the H. bilis cluster
-H. cinaedi does not cause disease in humans, but causes enteritis, proctocolitis, and rectal infection in humans
-H. mesocricetorum - considered nonpathological commensal; causal association with pancreatic lesions has NOT been established
-H. cholecystus - isolated from hamsters with cholangiofibrosis and centrilobular pancreatitis
-H. aurati - experimental infx lesions of gastritis, chronic and progressive typhlocolitis, intestinal metaplasia, and large intestine dysplastic lesions; hamsters showed no clinical signs of chronic weight loss/poor body condition
-Helicobacter spp also isolated from a hamster with gastric adenocarcinoma
-Novel H. bilis cluster spp isolated from livers of hamsters - may play a role in hepatobiliary disease as these livers has lesions of chronic hepatitis, hepatic dysplasia, and biliary hyperplasia
60
Helicobacter species in hamsters.
Helicobacter spp. are G(-), curved to fusiform bacteria
Hamsters naturally colonized with several spp - H. cinaedi, H. mesocricetorum, H. cholecystus, H. aurati, and a novel sp in the H. bilis cluster
-H. cinaedi does not cause disease in humans, but causes enteritis, proctocolitis, and rectal infection in humans
-H. mesocricetorum - considered nonpathological commensal; causal association with pancreatic lesions has NOT been established
-H. cholecystus - isolated from hamsters with cholangiofibrosis and centrilobular pancreatitis
-H. aurati - experimental infx lesions of gastritis, chronic and progressive typhlocolitis, intestinal metaplasia, and large intestine dysplastic lesions; hamsters showed no clinical signs of chronic weight loss/poor body condition
61
Which bacterial species are associated with pneumonia in hamsters?
Pasteurella pneumotropica, Streptococcus pneumoniae, other Streptococcus spp., Corynebacterium paulometabulum suspected for acute pneumonia in hamsters (C. kutscheri nasal infx subclinical in hamsters)
Clin signs: depression, anorexia, nasal and ocular discharge, "chattering", respiratory distress
Pathogenesis: stress, changes in environmental temperatures
Prevention, Control, Treatment: avoid stressful situations, isolate affected animals, determine etiologic agent to choose antibiotics
62
Lymphocytic choriomeningitis virus in hamsters.
RNA virus of the arenavirus group
-Hamsters are most common animal species to transmit LCMV to humans (although lab mouse is primary reservoir for virus)
Clin Signs: dependent on virus strain, dose of virus administered, route of infection, age and strain of host, host immunocompetence; adult hamsters - natural infx causes acute short-term illness; perinatally exposed hamsters remain subclinical, despite shedding large amts of virus during this period
~1/2 of hamsters infected congenitally or as newobrns remain persistently infected and may develop chronic, progressive fatal dz with inactivity, wt loss, and wasting
Imparied reproductive performance has been reported in chronically infected females
63
Transmission of LCMV in hamsters.
Implantation of infected tumors (primary method), direct contact, fomites and aerosols
- High concentraions of virus have been found in blood, organs, urine, and feces of Syrian hamsters
- Viral shedding primarily in urine and saliva, but also in feces, milk, semen, and nasal secretions
- Horizontal AND verical transmission
64
Necropsy findings of LCMV in hamsters.
Perinatally infected and chronic disease: lymphocytic infiltation of liver, lung, pancreas, kidney, spleen, meninges, brain; chronic glomerulonephropathy and widespread vasculitis
-Progressive glomerulonephritis can be attributed to antigen-Ab complex deposition in the arterioles and glomerular basement membranes
65
Pathogenesis of LCMV in hamsters.
- Exp infx of young adults: viremia that decreases in titer over 3 months - virus excreted in urine longer and detectable in greater amts than in blood; complement-fixing Abs appear by 10 days post-infx, reach peak levels by day 60, than slowly decline
- Some hamsters infected neonatally remain healthy and follow pattern similar to young adults; others develop persistent viremia and lower levels of complement-fixing and neutralizing Abs
- Presence of viral antigen and γ-globulin in glomeruli suggests immune complex mechanism for the glomerulonephropathy, similar to LCMV in mice
- Diff Dx: other causes of wasting disease like graft vs host disease, procedures resulting in immunosuppression; renal lesions - glomerular amyloidosis
66
Prevention and Research Complications of LCMV in hamsters.
Regular testing of hamster colonies & transplantable tumors; care in interpreting dirty bedding sentinel results as LCMV best transmitted through direct contact; avoid contact with feral mice
-ZOONOTIC (humans asymptomatic to severe CNS infx); LCMV-infx hamster studies are BSL-3; humans infected by direct contact or inhalation of infectious aerosolized rodent excretions or secretions
67
Sendai virus in hamsters.
Single-stranded pleomorphic RNA virus; genus Respirovirus, family Paramyxoviridae; mice believe to be natural host but rats and hamsters susceptible to natural infx
Clin Signs: mortality in newborn pups; most infections subclinical
Transmission: enzootic form reported historically; direct contact with infected rodents or fomites; aerosol inhalation has been successful experimentally
Necropsy: lung consolidation; experimental infx resulted in hyperplasia of nasal mucosal epithelium, hyperplasia of bronchial epithelium, peribronchial edema, peribronchial lymphocytic infiltration that resolves within 2 weeks postinoculation
68
Pathogenesis of Sendai virus in hamsters.
Descending infx typically restricted to the mucociliary epithelium of conducting airways but capable of spreading to alveolar epithelium
- Male Syrian hamsters intranasally inoculated - viral antigen present postinoculation day 3 in resp tract epithelium of nasal passages and trachea, present in bronchioles on day 5, and antibodies present by day 7 remaining at high levels throughout the 21 day study
- Differential diagnosis: Corynebacterium spp, Streptococcus pneumoniae, Pasteurella pneumotropica, Streptococcus spp, and MPnV
69
Prevention, Control, Treatment, Research Complicatons of Sendai virus in hamsters.
House hamsters separate from mice, rats, guinea pigs; hamsters from different sources should not be housed in same room unless all sources known to be free of virus
- Dirty bedding sentinels only variably efficacious for detecting Sendai outbreaks in mice
- Screen animal derived biological products by PCR or hamster antibody production (HAP)
- Complications: may be lethal to suckling hamsters, immunosuppressive effects of virus, d/t effects on nasal mucosal epithelium may complicate studies of behavior and olfactory function in hamsters
70
Murine adenovirus (MADV) in hamsters.
No specific hamster adenovirus has been isolated; can be experimentally infected with adenoviruses of other species
- Infection usually subclinical, unless animal stressed on immunocompromised
- Mice naturally infected with 2 strains: MADV strain FL (now MAdV A) and K87 (now MAdV B); hamsters can be positive for Ab to MAdV A
- Naturally occurring enteric adenovirus inection in hamsters, closely resembling MAdV B in mice, is not assoc w/ clinical disease and affects animals less than 24 days of age
- Adenoviral intranuclear inclusion bodies may be found in the intestinal epithelium in young hamsters
71
Hamster polyomavirus (HaPyV)
Double-stranded, non enveloped DNA virus; family Polyomaviridae, genus Polyomavirus
- Causes lymphoma (atypical of polyomaviruses) and spontaneous skin epitheliomas
- Exact origin unknown; isolated from spleen and kidney of subclinically infected European hamsters suggesting they are natural host
- Transmission: likely horizontal via ingestion of virions or contaminated fomites
- Tropism for both undifferentiated keratinocytes and lymphocytes = may cause 2 different disease syndromes; syndrome observed depends on individual hamster immune status and age
- Naive juvenile hamsters - epizootic multicentric lymphoma of mesentery, intestines, liver, kidney, and thymus
- Hamsters age 3 months to 1 year - trichoepitheliomas on the face, feet, neck, back, flanks, and abdomen
- Simultaneous lymphoma and trichoepithliomas in a single hamster RARE
- Virus likely persists in renal tubular epithelium and is shed in urine; virus-containing shed ketatinocytes or enterocytes in feces can be a source of infection
72
Hamster polyomavirus (HaPyV) clinical signs and prevention/control.
Clin Signs: Lymphoma - weight loss, dyspnea, dehydration, palpable masses on exam; trichoepitheliomas - nodules within the cutis, tumors may grow and regress spontaneously
Prevention/Control: treatment not recommended; culling of colony and decon of facility has failed to prevent new outbreaks in some facilities
-Virus stable in environment; susceptible to DNase, phenols, KOH; resistant to UV light, formaldehyde vapor, RNase, proteinasse K, chlorinated and iodinated disinfectants
73
Hamster parvovirus (rodent protoparvovirus 1 (RPV-1)).
Non-enveloped, single-stranded DNA virus, family Parvoviridae; shares homology with mouse parvoviruses; International Committee on Viral Taxonomy currently considers all rodent parvoviruses as one species
-Evidence that hamster is not natural host for any strain of RPV-1 b/c usually subclinical in their natural host (mouse is likely b/c MPV-3 is nearly identical)
74
Clinical signs, diagnosis, prevention of hamster parvovirus (RPV-1) in hamsters.
Adults: typically subclinical
Young hamsters, 2-4 weeks old: most susceptible; runted with incisor teeth abnormalities, domed craniums, small testicles, potbellied appearance; hemorrhagic dz has also been reported with diarrhea, ataxia, and mortality
-Hamsters that survive typically seroconvert within 1-3 weeks, but animals remain persistently infected for several weeks & it has not been determined if hamsters shed virus during that time
-Humoral immunity prevents reinfection
-Diagnosis: PCR for MPV-3/HaPV specific primers
-Control: monitor cell lines, serum, and tumors; outbreak management includes quarantine, facility disinfection, restocking with new hamsters
75
Protozoa in hamsters.
Spironuclues muris: incidental findings
Tritrichomonas muris: successfully eradicated from intestinal tract using 80mg metronidazole intragastrically for 6 days
Giardia: high prevalence in hamsters but not associated with clinical signs or lesions; can eliminated with dimetridazole in drinking water
76
Nematodes in hamsters.
Susceptible to pinworms: Syphacia mesocreceti, Syphacia creceti, Syphacia stroma, Syphacia peromysci, Syphacia obvelata, Syphacia muris, Aspiculuris tetraptera (specifically Siberian dwarf hamsters), Dentostomella translucida
- Mice have been shown to transmit S. obvelata to hamsters
- Hamsters can become infected with S. muris, the rat oxyurid, through direct contact with rats (eradicated with 2 courses of piperazine citrate 10 mg/ml drinking water for 7 days separated by 5 days
- Likely can adapt treatment from other rodents; avermectins, benzimidazoles
- Pinworm life cycle indirect; transmission through direct contact or fomites
77
Cestodes in hamsters.
Susceptible to a number of cestodes of family Hymenolepididae - Rodentolepis nana, Hymenolepis diminuta, Rodentolepis microstoma
-Historically R. nana important parasite of hamsters - 25-40 nm length, usually found in small intestine, host range includes mice, rats, NHP, and humans but host-specificity uncertain; human strain may be noninfective to rodents
Clin Signs: usually benign but depends on worm burden
Transmission: R. nana only known tapeworm with either direct or indirect life cycle - flour beetles or fleas as intermediate host, direct cycle more common and is 14-16 days in length, also autoinfection when eggs hatch within the host where they were produced
Diagnosis: eggs in feces or isolation of mature worm in intestines at necropsy; R. nana has hooks on the scolex, H. diminuta does not; PCR-RFLP also available
Prevention: isolation and quarantine of newly arrived animals; insect and wild rodent control; regular sanitation of cages and equipment
Treatment: praziquantel, thiabendazole, niclosamide; effective oral single dose agents for H. diminuta include praziquantel, bunamide, niclosamide, cambendazole, mebendazole
Research complications: potential morbidity and mortality; potential for transmission to humans
78
Mites in hamsters
Demodex criceti - Armenian hamsters, Demodex aurati; ear mites - Notoedres sp, tropical rat mite - Ornithonyssus bacoti, nasal mite - Spleorodens clethrionomys
Clin Signs: rare, even with high infestations; alopecia of rump and back with dry, scaly skin with D. criceti and D. aurati; notoedric mange in female usually only affects ears but in males lesions may also be on nose, genitalia, tail, and feet
Pathology: Demodectic mange - dilated hair follicles containing debris and mites, loss of hair shaft, increase in thickness of the corneum, little evidence of inflammation
Pathogenesis: Demodex direct life cycle takes 24 days; D. criceti and D. aurati complete life cycles in different areas of epidermis, permitting dual species infection; males more susceptible to infection than females; clinical disease assoc with immunosuppression - underlying diseases, advanced age, tumors
Diagnosis: skin scraping
Treatment: topical amitraz weekly to every 14 days & treat for at least 4 weeks following negative skin scrape; coumaphos, oral ivermectin; shampoos weekly with selenium sulfide and benzoyl peroxide in combination with topical treatments for critical animals
79
Benign neoplasms in hamsters
General consensus that most tumors occur more frequently in female hamsters than males.
Benign = intestinal polyps, adrenal adenomas, splenic hemangiomas, islet cell pancreatic tumors, hepatic adenomas, squamous papillomas of the forestomach, fibroadenomas of the mammary gland
One study found benign tumor incidence of 10% in males, 13% in females of BIO 15.16 line
80
Amyloidosis in hamsters.
Amyloidosis = normally soluble proteins polymerize as insoluble fibrils, common cause of death in hamsters on long-term experiments
- Two components of amyloid are amyloid A (AA) which is derived from amyloid fibrils, and amyloid P (AP) also known as 'female protein' (FP), a member of the pantraxin family of plasma proteins
- Sex hormone regulated expression of AP and levels in females typically 100-200x greater than males; female Syrian hamsters have predisposition to acquire amyloidosis earlier and with greater severity
- Organs involved: liver, kidney, stomach, adrenal, thyroid, spleen
- Testosterone has been linked to inhibition of hepatic synthesis of AP, which is the homolog of primary importance in the deposition of amyloid
- Nephrotic syndrome can occur due to amyloidosis: extensive SC edema, ascites, and hydrothorax; pale tan enlarged and misshapen kidneys, serum albumin decreased and globulin increased, proteinuria, hypercholesterolemia, triglyceridemia, high creatinine
- Histo for nephrotic syndrome: amyloid deposits initially in glomeruli of kidney and subsequently other tissues
- Amyloidosis in Syrian hamsters is a model for pathogenesis of same disease in humans, including link to Alzheimer's
- Amyloidosis can be induced experimentally using casein or LPS SC injections
81
Polycystic disease in hamsters
Cysts have been observed in up to 76% of Syrian hamsters over 1 year of age
- Liver common site, can also see in cecum, kidneys, ovaries, spleen
- Liver lesions related to developmental defects of normal ductal structures (bile ducts), while cysts in other organs likely d/t dilation of lymphatic system
- May see abdominal distension; at necropsy cysts are thin walled and contain clear watery fluid that is amber to green - in one study proteinaceous nature of fluid resulted in while solidified collections within cysts in the cecal walls
- Higher incidence of IP cysts in European hamsters than Syrian
82
Chronic hepatitis in hamsters.
First described as incidental findings in carcinogen studies
Linked to dietary contamination, infection with bacterial pathogens, immune system abnormalities - but a common etiology has not been identified
Diagnosis: necropsy as there are usually no clinical signs even in cirrhotic animals
-In most strains females more commonly affected than males
-Elevations of alanine aminotransferase (ALT) and bile acids
83
Atrial thrombosis in hamsters.
Common findings in aged Syrian hamsters; males and females equally affected but females develop at earlier age
Most commonly seen in APA strain, accompanied by cardiac hypertrophy that develops with age
Clin signs: suggestive of heart failure; include tachypnea, tachycardia, cyanosis
Necropsy: thrombi present, primarily in left atrium; may be accompanied by AV valve thickening (can also be seen in aged hamsters without thrombi)
Proposed that thrombi occur as a result of local blood stasis, secondary to heart failure
84
Chinese hamster
Cricetulus griseus
Also know as striped-back hamster
Today use of this hamster greatly overshadowed by use of cell lines derived from its ovarian cells - Chinese hamster ovary (CHO) cells
Susceptible to multiple infectious agents including bacteria, mycobacteria, protozoa, diphtheria, rabies, influenza, equine encephalitis
Spontaneous hereditary diabetes mellitus; susceptible to induction of stomach and esophageal cancer by oral diethylnitrosamine
Similar size to lab mouse - similar style caging is adequate
85
Chromosome number in Chinese hamster
Low number of 2n = 22; beneficial for cytogenetic studies
10 large pairs of autosomes and two sex chromosomes
Constant diploidy maintained in cell culture provides a stable cell system for assessment of agents with know/suspected mutagenic and carcinogenic properties
86
Chinese hamster biology
Adults: 39-46 g, ~9 cm long
Newborn: 1.5-2.5 g
Normal lifespan 2.5-3 years
Adult males have large testicles; brain and spleen both larger with respect to overall body size than in Syrian hamsters
Do well on standard rodent chow; may supplement with wheat germ for breeders
Average daily water intake: 11.4 ml/100 g body weight in males, 12.9 ml/100 g body weight in females
87
Estrous cycle of Chinese hamsters
Sexual maturity indicated by vaginal opening, with mucus-like material frequently secreted at beginning of estrus
Estrous cycle phases have distinct behavioral characteristics & vaginal orifice changes
During 4 day cycle, maximum progesterone on day 3 (differs from low levels in Syrian hamsters on day 3)
Gestation 20.5 days
Weaned 21-25 days
Sexually mature 8-12 weeks
Postpartum estrus 4 days
88
Breeding Chinese hamsters
Reversed illumination schedule needed for breeding
Females can be very aggressive immediately after mating - selective monogamous mating with docile females with high fecundity; can be mated in groups
Infertility in young females may be due to excess growth of hair around the vulva preventing penetration
89
Pregnancy in Chinese hamsters
Pregnancy indicated by a closed vagina with dry, pale, scaly perineal tissues at day 4 following mating
Progesterone levels increase through day 12, stabilize through day 18, peak on day 19, then dramatically drop prior to parturition
Dystocia may occur d/t fetal wedging in proximal portion of vagina - need surgical removal
90
Development of newborn Chinese hamsters
Newborns have front incisors
Body hair appears at day 3-4, complete coverage in 7 days
Eyes and ears open within 10-14 days
Testicles descend in males at ~30 days
As animals approach sexual maturity, aggressive females may fight until dominance is established
91
Infectious diseases in Chinese hamsters
- Tyzzer's disease is similar to Syrian hamsters
- Presence of antibodies to murine viruses has been reported
- Parasitic infections may include persistent colonization with Trichomonas spp; endo- and ectoparasites rare
- Demodex sinocricetuli have been reported in Cricetulus barabensis (considered synonymous with C. griseus), but appears to be very low susceptibility to demodectic mang in Chinese hamsters
92
Diabetes mellitus in Chinese hamsters
- Associated with degranulation of β-cells of the pancreatic islets of Langerhans - primary defect in the biosynthesis of insulin
- Animals can show signs as early as 18 days of age, but can occur at any age: polydipsia and polyuria (50-70 mL urine in 24 hr), urine staining/scald, initial weight gain, lethargy; occasional blindness, conjunctivitis, alopecia; very susceptible to mild stress and sudden death can occur
- Diabetic females may be infertile, but those that do become pregnant tend to have increased numbers of abortions and fetal deaths at delivery
- Appears to be transmitted as a recessive factor - appears that 4 genes involved & if 2 of 4 are homozygous glucosuria can result
- Duration, severity, and constancy of glucosuria controlled by modifier genes
- 100% of offspring become diabetic if parents at ketotic
93
Lesions of diabetes mellitus in Chinese hamsters
Gross lesions: kidneys can be slightly enlarged, spongy, and friable; dilated renal pelvis; when hydronephrosis is seen, retained urine is clear but odoriferous; urinary bladder usually distended with urine; liver may be moderately enlarged with yellow to gray color
Histopath: pancreatic islets of Langerhans decreased in number, decrease in number of β-cells - remaining cells stain lightly basophilic with cytoplasmic granulation and vacuolization & periodic acid-Schiff (PAS)-positive material within the cytoplasm accumulates around pyknotic nuclei
-Renal: convoluted tubules contain much protein precipitate; glomeruli hypocellular with marked sclerosis; intercapillary homogenous material can be observed that is PAS positive; Bowman's capsule may by slightly to moderately thickened; adhesions may be present between the glomerulus and capsule; PAS-positive material in basement membrane that may be wrinkled and slightly thickened
-Liver: Extensive vacuolization of cells with perinuclear halos; intracytoplasmic material is PAS-positive, but negative when stained for fat
-PAS-positive material occasionally found in pericardial adipose tissue
94
Pathogenesis of diabetes mellitus in Chinese hamsters
Degranulation of β-cells - results in decreased amount of insulin production with a reciprocal increase in glucagon
- In highly inbred glucosuric strains with diabetes, there is greatly reduced level of pancreatic insulin and significantly elevated level of glucagon in both pancreas and stomach
- A decrease in lactate dehydrogenase appears to be associated with severity of diabetes
- Contributing factor to renal pathology may be subnormal levels of specific glycosidases in the kidneys, with a resulting change in turnover of tissue glycoproteins
95
Differential diagnoses and research complications for diabetes mellitus in Chinese hamsters
Because is a spontaneous disease, should be ruled out whenever colony illness occurs; Tyzzer's disease is an initial differential and also as a secondary complication as diabetic animals are very susceptible to stress and subsequent immunosuppression
- Treatment with hypoglycemic drugs may be indicated in breeding females to maintain inbred lines
- Because cellular metabolism is affected, cytogenetic studies could produce unreliable data
96
Fighting in Chinese hamsters
Female littermates can become very aggressive as they reach maturity
- Bite wounds to tail and head area are common
- Litters should be separated before fighting occurs
- Must also anticipate means to remove male after breeding with female
97
Neoplasia in Chinese hamsters
Low incidence of spontaneous tumors; rarity of spontaneous and induced leukemias may reflect the absence of innate tumor viruses
- Uterine adenocarcinoma: firm, white growths on the visceral and parietal peritoneum; ~10% of hamsters in one study had lung mets, in another report no lung mets seen; vaginal bleeding most common initial sign
- Ovarian tumors: rare, but incidence significantly increased with exposure to radiation
- Hepatoma: benign & most often occur as multiple nodules; nodular hyperplasia, a nonneoplastic condition, can also be seen
- Pancreatic adenocarcinoma: believed to be rare in nondiabetic animals; reported in 3 yr old females partially inbred for development of diabetes
98
Cerebral hemorrhage in Chinese hamsters
Occurred in 20% of control and experimental animals in a 131iodine toxicity study - deaths at 1-2 yr old
- Hemorrhage most evident between cerebral hemispheres, blood often in lateral ventricles
- Hemorrhage shown to be caused by inflammation and necrosis of the anterior cerebral artery - homogenous PAS-positive material present within the media of the diseased artery
- Cause unknown but postulated to involve inflammatory or degenerative change in the anterior cerebral artery; true incidence beyond this report unknown
99
Periodontitis in Chinese hamsters
Found in a strain of Chinese hamsters with hereditary diabetes mellitus
- Lesion characterized by absorption of alveolar bone, inflammation, and pocket formation d/t splitting of the epithelial attachment
- Disease corresponds to that seen in humans with diabetes mellitus
100
Nephrosclerosis in Chinese hamsters
Study of 157 animals, found in 46
Pathology different from the intercapillary glomerulosclerosis seen with diabetes mellitus
-Gross lesions: pitting and decreased size of severely affected kidneys
-Histo: tubular degeneration, mild interstitial fibrosis, focal atrophy of the cortex seen in early disease; hyaline sclerosis of glomeruli, more severe interstitial fibrosis and tubular degeneration seen in late disease
101
Spondylosis in Chinese hamsters
Incidence and extent of spondylosis were increased in hamsters with spontaneous diabetes mellitus compared to nondiabetic control animals
102
Pulmonary granulomas in Chinese hamsters
Study of 157 animals, found in 54
-Gross lesions: subpleural, yellowish gray foci, 1-3mm diameter, variable involvement of lung parenchyma
-Histo: lesions consisted of alveolar collections of lipid-filled macrophages, mixed inflammatory cells, septal fibrosis, and occasional cholesterol clefts
Etiology remains unknown
103
Armenian hamster
Cricetulus migratorius; also known as gray hamster
- Susceptible to mutagenic and carcinogenic agents
- Cytological features similar to Chinese hamster, so also used for cytogenetic studies
- Like Syrian hamster, highly susceptible to oncogenic viruses but high tolerance for homologous and heterologous transplantable tumors
104
Biology of Armenian hamster
Care similar to Chinese hamster; similar body size and weight (33-80g)
Diploid chromosome number: 22; X and Y chromosome of equal size
Captured animals aggressive, but can be bred successfully in captivity
Sexual maturity: ~50 days of age
Gestation period: 18-19 day
Average litter size: 5-7 pups
105
Diseases of Armenian hamster
Spontaneous infectious diseases rare
- Expression of spontaneous amyloidosis differs in gender-specific AP expression ad susceptibility to AA amyloidosis from seen in Syrian hamster
- Hepatic carcinomas reported in animals exposed to estrogen
- Demodex cricetuli - skin lesions reported; this mite similar to D. aurati of Syrian hamster, occupies hair follicles particularly of face and back
106
European hamster
Cricetus cricetus
- Susceptible to N-diethylnitrosamine (DEN) with subsequent development of respiratory tumors (bronchogenic squamous cell carcinoma)
- More suitable model than Syrian hamster for highly concentrated and prolonged smoke-inhalation studies
- Bern Convention of 1979 established as strictly protected species in Appendix II, later listed in Appendix IV of Habits Directive - stict legal protection in all European countries
- No breeding colonies in US; sourced from European breeding colonies
- Not widely used in research; most studies are on hibernation
107
Biology of European hamster
Nocturnal, hibernate during winter months
- Largest hamster species (3x bigger than Syrian)
- Males larger than females
- White face and feet, reddish brown dorsum, cranioventral black patches, caudolateral white patches
- Very aggressive, easily frightened, will attack and bite
- Each litter defines a social order - heaviest male is dominant
- Chromosome diploid number 2n=22
- Water consumption: 5 mL/100 g BW
- Food consumption: 2.9 g/ 100 g BW in summer (August) & 1.8 g/100 g BW in winter (November)
- Mainly seed eaters,but will eat standard lab rodent diet
108
Lifespan of European hamster
Research-bred male: 31 months, female: 34 months - may be related to higher reported incidence of neoplasia in males
4-10 years in the wild
109
Reproduction in European hamsters
Sexual maturity: females 80-90 days, males 60 days
Estrus cycle: 4-6 days; proestrus lasts a few hours, estrus 1-2 days, metestrus 6 hours, diestrus 2-4 days; female only receptive to male during short period during estrus & aggressive otherwise; estrus determined by vaginal smears or test mating with a mesh divider
Gestation: 18-21 days (captured), 15-17 days (lab born)
Litter size: 6-9 pups; females have 1-2 litters per year
Weaning: 25-28 days; newly weaned animals ~75g BW; 6 month females and males 300-400g BW
-Sexual activity not observed in winter months - vagina closed and scrotum decreased in size with testes in abdominal cavity
110
Photoperiod regulation in European hamsters
Critical photoperiod, where gonadal regression is induced, is 15-15.5 hr
- Studies implicate a circannual rhythm in physiological variations animals, including changes in body weight and food intake even under conditions of constant photoperiod
- TRUE hibernators; hibernation affects thrombocyte and leukocyte values
111
Neoplasia in European hamsters
Spontaneous neoplasia common in older European hamsters - up to 70% incidence by 2 yr old
- Neoplasia slightly more prevalent in males
- Most frequent tumors: leukemias and lymphomas, adrenal pheochromocytomas, granulosa cell tumors in females
- Thymomas found in a small number - associated with large numbers of mast cells (not normally seen in human form)
- Similar to Syrian and Chinese, very low incidence of pulmonary neoplasia
112
Parasites in European hamsters
One outbreak of Spironucleus muris associated with chronic enteritis in newly captured animals reported
-In a small group of males, animals found to be generally free of endoparasites, ectoparasites, and blood parasites
113
Cysts in European hamsters
Prone to developing cysts in peritoneal cavity, particularly the liver
- Cysts more common in females
- Also seen in cecum, ovaries, spleen, kidney, and colon
114
Bacterial infection in European hamsters
Secondary infx with Corynebacteria, Staphylococcus, Pasteurella pneumotropica, and Pasteurella multocida have been assoc w/ pathological processes resembling fistulated abscesses in the head and jaws
115
Dental diseases in European hamsters
Develop malocculsion, osteomyelitis, and dysplasia - appear to increase with age - European hamster could be of use for dental research?
-These disease processes often accompanied by secondary bacterial infx, which ma be fatal
116
Djungarian hamsters
Phodopus campbelli (Russian dwarf) & Phodopus sungorus (Siberian dwarf) - believed to be 2 separate species
- In response to a short photoperiod: P. sungorus molts to a pure white haircoat & P. campbelli retains gray haircoat
- Close phylogenetic relationship; unique C-banding patterns in P. sungorus chromosomes distinguish karyotype from that of P. campbelli
- Russian dwarf hamster from Siberia, China, Mongolia; distant relative of Syrian hamster
- Siberian dwarf hamster from Kazakhstan, Manchuria, and northern China
- 50-100mm body length & 10mm tail
- BW range 18-25g, mature males reaching 40-50g
- Dorsal fur grey with dark stripe dorsally along length of body; ventrum, limbs, and tail tend to be white
- Used in behavior and reproductive physiology studies
117
Lifespan of Djungarian hamsters
Generally 9-15 months, up to 2 years
Karyotype is 2n=28 chromosomes
High incidence of neoplasia and susceptible to carcinogens; can be infected with oncogenic viruses, particularly Rous sarcoma virus (RSV), Human mastadenovirus A (formely known as human adenovirus 12), and SV40
118
Reproduction in Djungarian hamsters
Most compressed reproductive cycle of any eutherian mammal - can mate on day of parturition (following 18 day gestation) & deliver 2nd litter while weaning 1st within a 36 day period
- 4 day estrus cycle with spontaneous ovulation (like Syrian and Chinese)
- Pregnancy in P. campbelli dependent on continuous secretion of progesterone by corpus luteum through late gestation; prolactin levels absent during midgestation and resume in late gestation - possible reasons for this reappearance incl influences of lactogenesis, mammary gland development, regulation of maternal behavior toward newborns
- P. campbelli: monogamous parental care by both males and females; P. sungorus: males do not participate in offspring care
- Female NOT aggressive = can maintain breeding pairs throughout life
- Weaned at 3 weeks of age
- Females can bear total of 1-18 litters, each with 1-9 pups
- Reproductive development of females is accelerated when exposed to males of the same species
- Increased food hoarding reported in P. sungorus as a behavioral adaptation to provide accessible energy during pregnancy
- Endocrinology in P. sungorus is similar to other rodent species, but differs from P. campbellis - implies two species have undergone evolutionary selection pressures with respect to reproductive endocrinology
119
Photoperiod effects in Djungarian hamsters
Critical photoperod is ~13 hr (VERSUS 12.5 hr in Syrian, 15.5 hr in European)
- Changes in photoperiod influence breeding activities, thermoregulation, hair-coat growth, fat metabolism
- Used to study pineal gland and melatonin secretion in mediating the effects of photoperiod
- Do NOT hibernate, even when exposed to temps below -40 C; seasonal acclimation of blood-gas transport during periods of colder temps is facilitated by increased relative heart weight, increased surface area of erythrocytes, slightly altered hemoglobin content - all aid oxygen transport
- Decrease resting metabolic rate and increase capacity for nonshivering thermogenesis to adapt to temps
- Omnivorous; can maintain on same diet as Syrian hamsters
120
Neoplasia in Djungarian hamsters
High incidence of oral cavity, skin, and mammary gland neoplasia - particularly in females - in Russian dwarf hamsters
- Metastatic fibromas, fibrosarcomas, mammary adenocarcinomas, fibroma with liver cell carcinoma
- Incidence of tumors has changed over time, with mammary tumors increasing and skin tumor decreasing - may reflect genetic alterations linked to inbreeding
- Affected dwarf hamsters exhibit rapid weight loss (similar to that seen with bronchopneumonia and maloccluson)
121
Other diseases in Djungarian hamsters
- Demodectic mites: alopecia, ventral dermatitis
- Cystic ovaries: Russian dwarfs; clin signs of swollen abdomen, blood vaginal discharge
- Hypersensitivity to bedding, particularly cedar chips, reported: alopecia with dry skin and secondary bacterial infx
- Enteritis with rectal prolapse NOT reported in Russian hamster, although common in other hamster species
