Biology, Husbandry and Diseases of the Hamster VCM 656

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Biology, Husbandry and Diseases of the
HamsterVCM 656
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Taxonomy

• Order Rodentia
• Family Cricetidae
• Genera Cricetus, Mesocricetus, Cricetulus,
  Phodopus
• Animals of these genera are characterized by
  large cheek pouches and short tails
• Native to SE Europe and Asia Minor
• Live in deep tunnels and hoard grain
• Nocturnal, mostly solitary

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Syrian hamster Golden hamsterMesocricetus
auratus

• Advantages as a research model
• Availability and ease of reproduction.
• Relatively free of spontaneous diseases, but
  susceptible to many induced pathogens.
• Special anatomical and physiological features
• Cheek pouches
• Hibernation
• Radioresistance
• Others
• Short life cycle and rapid development.

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• Syrian hamster Mesocricetus auratus
• 22 chromosome pairs
• 18 centimeters long, 85-130 gm adult weight
• Chinese hamster Cricetulus griseus
• 11 chromosome pairs
• 9 centimeters long, 42 gm adult weight

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Biological Data

• Average life span 18-36 months
• Sexual maturity 2 months
• Average adult weight 85-130 gm
• Heart rate 300-470 bpm
• Respiratory rate 38-110 bpm
• Rectal temperature 37.6 oC (100oF)

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Sexual Dimorphism
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Sexual Dimorphism

• Male
• Greater anogenital distance
• Scrotal bulges at tail base
• Female
• 3 distinct openings rectum, vulva, urethra

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Mouth

• Dentition
• I 1/1, C 0/0, P 0/0, M 3/3
• Continuously growing teeth
• Cheek pouch
• Storage food, bedding, young
• Immunological privileged site

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Flank glands

• Sebaceous glands on each flank
• Sexual odors and olfactory territorial marking
• More noticeable in sexually active males.

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Two-Chambered Stomach

• Distinct separation
• Squamous forestomach
• Glandular stomach

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Reproductive Anatomy

• Female
• Bicornuate uterus
• Each uterine horn opens separately into vagina
• 12-14 nipples
• Male
• Os penis
• Large seminal vesicles

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Husbandry

• Solid bottom caging
• Wide feeder slots
• Nocturnal
• Coprophagic
• Tend to eliminate in 1 corner
• Like hiding places, are escape artists
• Females are dominant and may attack males
• Mature animals are usually housed separately
• Untamed or startled hamsters may bite

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Reproduction

• Estrus cycle 4 days
• Gestation 16 days
• Litter size 6-8
• Weaning 21-28 days
• Neonates hairless, toothless, eyes and ears
  closed
• Cannibalism
• Do not disturb mother for 7-10 days postpartum
• Provide fresh greens, treat food just prior to
  parturition
• Young require access to water, in addition to
  mothers milk
• Estrus end marked by postovulatory vaginal
  discharge
• Copious, white, thick, tenacious, distinctive
  odor

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Hibernation

• Cold stimulates food gathering
• Do not fatten prior to hibernation
• May hibernate at 5oC (41oF)
• Intermittent sleep 1-7 days, arousable
• Will starve if dont eat periodically
• Normally eat several times a day
• Food intake does not vary from day-to-day
• Hamsters do not respond to fasting by increased
  food consumption.

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Restraint
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Restraint - Scruffing
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Bacterial Disease

• Predisposing Factors
• Shipping
• Overcrowding
• Poor nutrition
• Sanitation
• Parasitic or viral disease
• Experimental manipulation

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Proliferative Ileitis

• Common synonyms
• Wet tail
• Regional enteritis
• Terminal ileitis
• Transmissible ileal hyperplasia
• Enzootic intestinal adenocarcinoma

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Proliferative Ileitis

• Clinical signs
• Watery diarrhea
• Dehydration
• Lethargy
• Irritable
• Anorexia
• Weight loss

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Proliferative Ileitis

• Intracellular bacteria
• Undetermined etiologic agent
• E. coli
• Campylobacter-like
• Desulfovibrio-like
• Transmission
• Fecal-oral
• Fomites
• Direct contact
• Rapid spread
• Most susceptible
• 3-8 weeks of age

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Proliferative Ileitis

• Gross pathology
• Thick, congested ileum
• Enlarged mesenteric lymph nodes
• Peritonitis
• Adhesions

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Proliferative Ileitis

• Microscopic pathology
• Epithelial hyperplasia
• Crypt, villous and glandular
• Markedly increased mucosal thickness
• Villar necrosis
• Microabscesses
• Crypt and wall
• Mucosal edema
• Lymphoid hyperplasia

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Proliferative Ileitis

• Treatment
• Antibiotics and fluid support
• Variable results
• Control
• Remove infected hamsters
• Sanitation
• Research complications
• May have high prevalence
• Variable morbidity 20-60
• High mortality 90

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Clostridial Enterotoxemia

• Clostridium difficile
• Anaerobic, cytotoxin production
• Normal gut inhabitant low numbers in cecum
• Environment
• Bacterial overgrowth
• Secondary to antibiotic administration
• High fat diets, stress
• Clinical Signs
• Anorexia, rough hair coat
• Diarrhea, marked dehydration
• Death within 4-10 days

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Clostridial Enterotoxemia

• Gross pathology
• Characteristic gross lesions
• Markedly hemorrhagic distal ileum
• Distended cecum
• Acute case
• Hyperemia of SI
• Vascular congestion of cecal vessels
• Mucosal hemorrhages
• Fluid-filled cecum

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Clostridial Enterotoxemia

• Microscopic pathology
• Marked mucosal hemorrhage
• Loss of mucosal architecture
• Submucosal edema

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Clostridial Enterotoxemia

• Diagnosis
• History and clinical signs
• Characteristic gross and microscopic lesions
• Isolation of large numbers of C. difficile on
  anaerobic culture
• Cell culture assay for clostridial cytotoxin B
• Treatment
• Vancomycin, 20 mg/kg, daily, PO
• Effective in controlling preventing clostridial
  disease
• Major adverse effect severe gaseous cecal
  distention death

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Tyzzers Disease

• Clostridium piliforme
• Obligate, intracellular, spore-forming bacteria
• Fecal-oral transmission
• Lesions may occur in

• Heart
• Intestine
• Liver

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Tyzzers Disease

• Clinical signs
• Subclinical until stressed
• Death without signs
• Hunched posture, rough hair coat
• Diarrhea
• Pale yellow and watery
• Staining tail and ventral abdomen

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Tyzzers Disease

• Gross pathology
• Liver - most common
• Hepatomegaly
• Multifocal hepatic necrosis
• Intestine
• Ileum through colon
• Serosal edema
• Gaseous distention
• Occasional hyperemia or hemorrhage

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Tyzzers Disease - Microscopic pathology
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Tyzzers Disease

• Diagnosis
• Gross and histologic lesions
• Typical bacteria clusters on silver stain
• ELISA tests
• Treatment
• Antibiotics may control outbreak, but not
  eliminate infection
• Control
• Remove symptomatic and/or serological positive
  animals
• Improve sanitation

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Salmonellosis

• Uncommon
• S. typhimurium or S. enteriditis
• Fecal-oral transmission
• Clinical signs
• Lethargy, rough hair coat, anorexia, weight loss,
  increased respiratory rate
• Gross pathology
• Pulmonary hemorrhages, multiple liver white
  spots, hyperemic lymph nodes
• Microscopic pathology
• Thrombosis hepatic and pulmonary veins
• Multifocal interstitial pneumonia
• Multifocal hepatic necrosis
• Control Depopulation - Zoonotic

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Respiratory Disease

• Usually associated with streptococcal or
  pasteurella infections
• Clinical signs include
• Nasal and ocular discharge, anorexia, depression,
  dehydration, labored breathing, weight loss
• Gross lesions
• Lung consolidation
• Conjunctivitis
• Otitis interna
• Diagnosis
• Clinical signs
• Gross lesions
• Culture

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Lymphocytic Choriomeningitis

• Arenavirus, RNA
• Transmission
• Urine (feral mice possible reservoir), direct
  contact, fomites, aerosols, tumor transplantation
• Clinical signs
• Vary with age, animal strain, viral strain, route
  dose of infection, immunocompetence
• Naturally occurring disease persistent,
  subclinical
• Experimental neonatal infection chronic wasting
  disease

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Lymphocytic Choriomeningitis

• Zoonotic
• Spread by aerosol and direct contact
• Pet research hamsters
• Virus-infected tissues, transplantable tumors,
  cell lines
• Human clinical symptoms
• Initially
• Fever, headache, myalgia, nausea, vomiting, sore
  throat, photophobia
• Recurrence
• Sudden appearance of meningeal signs, focal
  hemorrhagic meningoencephalitis
• Differential diagnosis
• Influenza, mononucleosis, herpes encephalitis,
  tuberculous meningitis

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Demodecosis

• Two demodectic mites in hamsters
• Clinical signs
• Alopecia without pruritis and without
  inflammation
• Increased incidence with age
• More common in males

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Demodecosis

• Demodex criceti
• Small, rounded
• Epidermal pits
• Demodex aurati
• Long, thin
• Hair follicles

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Pinworms

• Hamster pinworm
• Syphacia mesocriceti
• Mouse pinworms
• Syphacia obvelata
• Aspicularis tetraptera

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Tapeworms

• Hymenolepis nana dwarf tapeworm
• Usually resides in lower small intestine
• Very small 7-100 mm long
• Indirect life cycle pass through a vector
• Direct life cycle
• Can reinfect via coprophagy
• Zoonotic

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Tapeworms

• Hymenolepis diminuta
• Rat tapeworm
• Upper small intestine
• Much larger 60 cm
• Indirect life cycle
• Severe infections
• Retarded growth, emaciation
• Intestinal impaction/occlusion
• Death

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Atrial Thrombosis

• Spontaneous cardiac thrombi in aged hamsters
• Common 13 to 27 months of age
• Usually left atrium
• Both sexes affected
• Occurs earlier in females
• Clinical signs
• None prior to death
• Tachypnea cyanosis
• Postmortem findings
• Ventricular hypertrophy
• Nonseptic inflammation
• Myocardial degeneration
• Pulmonary edema and plural effusion

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Amyloidosis

• Most common disease of aging in hamsters
• 80 over 18 months
• Clinical signs
• Edema, ascites, wasting, hypoproteinemia,
  proteinuria
• Multiple tissues may be affected
• Kidneys first and most common
• Normal glomerular architecture obscured by pink
  amyloid

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Amyloidosis

• Liver
• Deposits in vascular walls and portal areas
• Diagnosis
• Confirmed by Congo red stain of tissues
• Apple green birefringence with polarized light

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Polycystic Liver Disease

• Common, incidental finding in hamsters over 1
  year of age (76)
• Development of large cysts
• Surface parenchyma
• Congenital in origin
• No clinical signs

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