Chapter 8. The Laboratory Woodchuck Flashcards
1
Q
Woodchuck: taxonomic information
A
Eastern woodchuck = Marmota monax
Order Rodentia
Family Sciuridae
Common names - groundhog, whistle-pig, chuck
2
Q
Natural distribution of woodchucks
A
Eastern and Midwestern US, Southeastern Alaska, Southern Canada
3
Q
Average body size of woodchucks
A
In captivity, 3-5 kg males & 2.5-5 kg females
4
Q
Hibernation in woodchucks
A
Obligate hibernators in the wild. Body weight increases 25-100% during spring/summer; decreases by 15-50% during autumn/winter hibernation.
Brief breeding season in spring after emerging from hibernation.
Similar changes seen in laboratory woodchucks, even when prevented from entering deep hibernation
In lab, circannual cycles advance with breeding 2-8 weeks earlier than in the wild
5
Q
Studies based on woodchuck hibernation
A
Used to study food intake, obesity, energy balance, endogenous circannual cycles, photoperiod entrainment of circannual cycles, seasonal breeding, hibernation, viral hepatitis & sequelae incl. hepatocellular carcinoma
6
Q
Woodchuck model of viral hepatitis
A
There are indigenous populations with high incidence of woodchuck hepatitis virus (WHV)
7
Q
Woodchuck circannual cycles in laboratory
A
Use of artificial photoperiod to synchronize circannual cycles of animals in a group or colony important for reproduction and to synchronize metabolic cycles.
Consider possible asynchrony between animals when use or experiments.
8
Q
Obtaining woodchucks for study
A
If trapped from wild - tattoo identification, dust with insecticidal powder, bled periodically to check for WHV, isolated from main colony for 6 months.
Difficult to accurately age, but can tell juvenile (<1 yr) and yearling from adult.
9
Q
Geographic distribution of woodchuck hepatitis virus (WHV)
A
Woodchucks from New York and New England may be preferable to woodchucks from the Mid-Atlantic region as foundation animals
10
Q
Woodchuck housing
A
- Metal cages designed for rabbits, dogs, cats
- Close any gaps >1.5 inches (can fit through anywhere their head fits through)
- Solid floors (feces do not fall through slats, slats can rip toenails)
- Secure floor, food and water dishes so woodchucks cannot remove
- Can house in large pens (enclose top of chain link runs because good climbers)
- If positive for WHV housed in Horsfall cages to prevent transmission
- Include a wooden or metal nest box as a burrow
- Provide bedding material like woodchips (woodchucks use in nest and to cover feces)
- Provide ad lib water; woodchucks drink a large amount of water
11
Q
Temperature & humidity range for woodchucks
A
Temp: 17-23 C; sensitive to high temps, use A/C or fans if necessary
Humidity: ~50%; lower humidity associated with ring-tail like syndrome in pups
Light cycles should approximate seasonal day length
12
Q
Identification methods in woodchucks
A
- Clip or dye hair; tattoo ink on fur lasts about one week
- Hair growth is rapid between late May and October - clipped areas should be checked weekly
- Ear tags, ear notches, tattoos
- Tattoo chest or inner thigh; clip and surgically scrub area first, apply antibiotic ointment afterwards
13
Q
Woodchuck restraint
A
- Woodchucks have powerful jaws and large incisors - bite wounds
- Carry in a nest box with a handle
- Carry with a gloved hand underneath (primate handling glove) and supporting the body
- Lift by grasping the tail
14
Q
Woodchuck anesthesia
A
- 50 mg/kg ketamine + 5 mg/kg xylazine for phlebotomy or short surgical procedures (20 min)
- For woodchucks with compromised liver function, isoflurane; Woodchucks CAN VOMIT
- 2-6 mg/kg IV pentobarbital to prolong anesthetic state of ketamine/xylazine (20-40 min)
- Innovar Vet (fentanyl + droperidol) 0.35 mg/kg IM
- Withhold water after anesthesia to prevent accidental drowning
15
Q
Woodchuck venipuncture sites
A
- Femoral vein or artery in the inguinal region - feel pulse as vessels not visible
- Maxillary or linguofacial vein near the clavicle
- Cephalic and tarsal veins - small amounts
- Cardiac puncture has complications - cardiac tamponade and death
16
Q
Injection sites in woodchucks
A
- IM: gastrocnemius or quadriceps muscles
- Hold the tail and allow the animal to grasp the edge of the cage with front paws
- Myonecrosis can occur with repeated injections- alternate muscle groups
17
Q
Annual metabolic cycles in woodchucks
A
- Hibernation induced by food withdrawal and temp of 5-10 C
- Circannual cycles can shorten to 11, 10, or 9 mths if not subjected to seasonal changes in photoperiod
- Most woodchucks maintained at 20-25 C and with food and water constantly available will undergo seasonal periods of reduced body temp - autumn or early winter may be found with rectal temps or 30 C or lower
18
Q
Circannual low body temp in woodchucks
A
Associated with low levels of free thyroid hormone despite the presence of moderate to high levels o total thyroid hormone
Majority of thyroid hormone at that time is bound to thyroxine-binding globulin (TBG) and other proteins - very little free hormone available to promote mitochondrial activity and basal metabolism
19
Q
Resting metabolism in woodchucks
A
VO2 average 4.4 +/- 0.3 ml/min/kg in early autumn
VO2 average 7.3 ml/min/kg in early spring
20
Q
Seasonal physiology in woodchucks
A
- Gonads slowly regain function such that they are fully recrudesent at the end of the ‘hibernation period’ in mid to late winter
- Body weight declines autumn-early spring as fat stores are utilized; in one study, weight losses were greater in females
- In late winter-early spring, metabolic activity increases and rectal temp increases to high normal
- Changes d/t increased pituitary secretion of TSH causing more thyroxine secretion, and to decreased amounts of TBG & increased amounts of free thyroxine; also seasonal increase in prolactin at this time
- Brief breeding season and 31 day pregnancy in late winter/early spring
- Majority of animals will become asynchronous and “free-run” in 2-3 years if photoperiod cues simulating natural environment are not provided (large block photoperiod changes like in other species don’t work)
21
Q
Seasonal feed intake in woodchucks
A
- Spring/summer = decline in thyroid hormones and change from minimal weight gain to rapid weight gain
- Weight gain is almost entirely at deposits to prepare for hibernation
- In summer, food intake spontaneously declines rapidly, several weeks before peak body weight is reached - signal mechanism not known, but creates a brief period of positive energy balance in summer before slow protracted decline in body weight in autumn and winter
22
Q
Molting in woodchucks
A
Fur molts in late summer and late winter
23
Q
Photoperiod control in woodchucks
A
- Best method: microprocessor controlled timers for natural, 0-4 minute per day changes in photophase
- Can also do weekly, twice monthly or monthly changes
24
Q
Hibernation in woodchucks
A
- In the wild, enter burrow between Sept 15-Nov 1, emerge in Feb-Mar
- Males emerge before females. adult emerge before yearlings
- Bouts of torpor an arousal, lasting 1-7 days each
- In the lab, induce hibernation with room temp 15 C or lower (6-8 C) and removing food
- Make sure appropriate preparative weight gain occurs to avoid morbidity/mortality
- Body temps may go as low as 1-2 C above room temp (hypothyroid state, reduced metabolism)
25
Woodchuck lifespan
14. 9 mths in the wild
| 4. 5 yrs in captivity (maximum 14 yrs)
26
Woodchuck hematology
Hct & percent saturation of hemoglobin can be higher in autumn vs spring
27
Diet for captive woodchucks
- Rabbit food (at least 15% protein) formulated into large blocks (~5.5 x 1.5 cm) for gnawing to wear down incisors
- A rabbit 'breeder's formulation' diet (at least 17%) and smaller sized pellets can be fed to pregnant females and pups
- Provide two large bowls of food per litter and check bowls twice daily - reduce periweaning pup mortality (30-80 days old) d/t food competition
28
Breeding in woodchucks
- Single, 2-4 week winter breeding season - late winter shortly after hibernation emergence
- Can produce one litter per year
- Peak gonadal function during late winter
- Breeding intervals can become shorter than 12 mths in lab without cirannual photoperiod entrainment - place breeding groups based on testis enlargement and vulval swelling
- Pair housing or Male housed with harem of 2-5 females
- Place in cages with solid floor rather than grate
- Provide one or more nest boxes
- Can move pregnant female to birthing pen or keep with male
- Leave female undisturbed from midgestation onwards
29
Breeding season in woodchucks
Wild: late Feb-March
Captivity: later Jan-early Feb
30
Fertility in woodchucks
- Yearling females: 50% fertility; adults 2 yr or older: ~100% fertility
- Male puberty: 10-11 mths
- Male sexual maturity: 22 mths
- Fertility lower in yearling females, females 5 yr or older, and in females subjected to repeated handling
31
Estrus detection in woodchucks
- Vulval swelling over 1-3 weeks, with maximal vulval diameter for 5-8 days
- Proestrus lasts 1-2 weeks
- Estrus lasts ~1 week; 5-10 days in most instances
- Pair for breeding when vulvar diameter reaches 7 mm
32
Female reproduction in woodchucks
- Reflex ovulators = ovulation is induced by multiple copulations
- Can have spontaneous ovulations (like cats; rare)
- Progesterone elevated during gestation, the 5-8 wks of lactation, and 1-8 weeks after lactation
- Progesterone decline for 8-24 hr period before and during parturition
33
Woodchuck gestation length
31-32 days
34
Litter size in woodchucks
- 1-10; usually 2-7 pups
| - Smaller litters for yearlings vs older females
35
Spontaneous luteinization in woodchucks
In the absence of mating, spontaneous luteinization of follicles in nonbred and in mated but non pregnant females typically coincides with the time when cohort females are giving birth and suckling young
36
Female reproductive tract in woodchucks
Double cervix and complete medial septum in the body of the uterus = all conceptuses are derived from the unilateral ovary
37
Antimesometrial implantation
Initial embryonic attachment and early implantation occur during a decidual reaction of the uterine endometrium at sites in the lumen OPPOSITE the region of the uterine mesentery (or mesometrium), away from the mesentery and blood supply
-Subsequent embryo development and attachement of the discoid placenta occur on the mesometrial side of the uterus, close to the mesentery and blood supply
38
Placentation in woodchucks
Discoid
39
Male reproduction in woodchucks
- Abdominal testes in summer and early autumn
- Testicular recrudescence, scrotal development, and testis descent occur during hibernation & males emerge with peak spermatogenesis and peak size testes
- In lab-housed males these changes occur more rapidly in late autumn and early winter
- Breeding season of an individual male is 4-8 weeks, avg 6 wks
- Onset of testiculat recrudescence has been advanced by exogenous gonadtropin
- Prominent Cowper's glands (bulbourethral glands) - urethral and vaginal plugs
40
When to place woodchucks in breeding groups?
- Calendar date of expected breeding season
- Vulval swelling of individual females or swelling in 25% of colony females
- 2 weeks after enlarged scrotal testes confirmed in 50% of the males
41
Detection of estrus in woodchucks
- Proestrus = vulval diameter >7 mm
- Estrus = peak vulval size (8-12 mm)
- Late estrus = softening of vulva/loss of turgor
- Cytology: DECREASED neutrophils during proestrus and estrus
42
Detection of pregnancy in woodchucks
- Abdominal palpation following ketamine/xylazine anesthesia
- Fetal heartbearts on U/S at midgestation
- Time of earliest fetal detection has NOT been determined
43
Woodchuck pup development
- 20-40g birth weight
- Umbilical remnant lost by day 4
- Hair growth begins at day 4; fur has developed by 2 wks
- Can transfer to foster dams between day 4-21
- Teeth erupt day 17-24; upper teeth erupt at 4 wks
- Testes scrotal at 3-4 wks
44
Woodchuck weaning age
4-6 weeks of age
- Pups can stay in pen with dam for up to 1 yr of age
- Provide small rabbit pellets for 6-9 months
45
Why must female woodchucks be housed individually for several weeks after weaning?
Serious fighting will occur.
| -Not seen in group-housed females after weaning or in inbred yearling females
46
Signs or torpor in woodchucks
Shaking, lethargy, anorexia
-Must differentiate from sick animal = sick animal will have a normal body temp (37 C); torporous animal will have a low body temp near room temp (8-10 C)
47
Prevention of aggression in male woodchucks
- Elevated testosterone levels during breeding season = more fighting
- Adult males in proximity to females should be housed in individual cages
- Young males may be housed together until their second spring
- Adult males can be housed together if introduced outside of the breeding season, given additional nest boxes, and isolated from females
48
List common health conditions in woodchucks
1) Bacterial folliculitis (tail base dermatitis in woodchucks housed in metal stovepipes)
2) Bite wounds and associated cellulitis (can progress to osteomyelitis) during breeding season
3) Diarrhea - stress, transitional changes in food or water intake (loose stool common during the breeding season and around hibernation); Giardia may contribute but is not a primary pathogen; can progress to rectal prolapse, intussusception, intestinal volvulus
4) Dental problems - traumatic lesions MORE common than congenital malocclusion
5) Ocular lesions - fighting, conjunctivitis d/t bacteria or environmental irritants
6) Respiratory conditions - diaphragmatic hernias, cardiomyopathy, profound obesity, rhinitis, pneumonia
7) Ear infections
8) Chronic debilitation
49
CNS signs in woodchucks
- CNS signs or edema occur in <5% of woodchucks
- Cerebral nematodiasis common in WILD woodchucks
- Otitis media/interna in colony born
- Cerebral hemorrhage
- Vit E/selenium deficiency
- Renal encephalopathy
- Hepatic encephalopathy (& cardiomyopathy, immune-mediated glomerulonephritis) in WHV infected animals
50
Parasites in wild woodchucks
- Taenia crassiceps
- Ackertia marmota
- Baylisascaris sp.
51
Most common cause of death in WHV positive woodchucks?
Hepatocellular carcinoma
52
Most common cause of death in WHV Negative woodchucks?
```
Cardiomyopathy with congestive heart failure
Aorta rupture
Nephritis
Glomerulonephritis
Pneumonia
Diaphragmatic hernia
```
53
Bacterial folliculitis in woodchucks
- Common in woodchucks
- Staph aureus and Strep Group A most common; sometimes Pasteurella multocida
- Erythema, papules, pustules, epidermal collarettes, ulcers, draining tracts, matted hair overlying
- Late stage: crust, alopecia, hyperpigmentation, lichenification
- Dorsal lumbosacral region, limbs, face, inguinal areas
- Pododermatitis with severe erythematous swellings and draining tracts
- Can be fatal to neonates = septicemia
54
Bacterial folliculitis etiology in woodchucks
- Housing in Horsfall units
- Staph aureus and Strep Group A are common mouse and rat flora
- Stress related to transfer between facilities
- Hormonal fluctutations
55
Bacterial folliculitis prevention in woodchucks
- Individual housing - contagious!
- Limiting movement of woodchucks between facilities
- Cleaning and disinfection of cages and all materials in contact with animals
56
Bacterial folliculitis treatment
- Clip, clean with chlorhexidine or povidone-iodine, debride if necessary, apply topical bactericide
- Reserve parenteral abx tx for deep cellulitis or multiple lesions
- Lesions typically resolve within 10 days; result in hyperpigmentation and alopecia until subsequent hair growth occurs during the summer
57
Otitis in woodchucks
- More common in older woodchucks
- Occasionally extends to inner or middle ear
- Signs: head tilt toward affected ear, nystagmus, circling, rolling, loss of balance, otic discharge
- Can progress to meningitis, encephalitis, prolapse of cerebellum through the foramen magnum
58
Otitis etiology in woodchucks
Morganella morganii, Proteus sp., Escherichia coli, Citrobacer koseri diversus, Streptococcus sp.
59
Otitis treatment in woodchucks
- Anesthetized woodchuck, culture ear canal
- Examine canal for foreign bodies, polyps, or ruptured tympanic membrane
- Flush with dilute (1:40) chlorhexidine solution & apply topical antibiotic solution
60
Otitis treatment in woodchucks if tympanic membrane is ruptured or progresses to otitis media/interna
- Ruptured: Flush ear with saline rather than dilute chlorhexidine
- Topical antibiotic/antiinflammatory product
- Systemic antibiotics
- If tympanic membrane intact with otitis media or interna - need to rupture for ventilation and drainage
61
Pneumonia in woodchucks
- Lobar or bronchpneumonia, occasionally aspiration pneumonia
- Bacterial pneumonia more common
- Severe cases: pulmonary abscesses, suppurative pleuritis, septicemia
- Mild, chronic granulomatous reactions to inhaled or aspirated irritants with animals usually asymptomatic
62
Clinical signs of pneumonia in woodchucks
- Sudden death
- Inappetence, lethargy, weight loss
- Naso-ocular discharge
63
Bacterial pneumonia etiology in woodchucks
- MOST COMMON: Beta-hemolytic Strep
| - S. aureus, Pasteurella sp., E. coli, Bordetella bronchiseptica
64
Bordetella bronchiseptica in woodchucks
Unique lobar pneumonia
| -DDx: pulmonary abscesses, neoplasia
65
Helicobacter marmotae
- Possible interaction with WHV and may be co-factor in hepatocarcinogenesis
- In A/J mice that get hepatic neoplasia assoc w/ H. hepaticus, they develop hepatitis but NOT hepatic neoplasms with H. marmotae
66
WHV positive woodchuck models
- Hepatitis B virus: WHV & HBV both family Hepadnaviridae; infx with both can lead to chronic hepatitis and HCC
- Study mechanism of hepatocellular injury in acute and chronic viral hepatitis, oncogenic role of virus, interactions between hepadnaviruses, diet, and/or environmental factors
- Antiviral strategies for treating HCC and chronic liver disease
67
Median time to HCC in woodchuck WHV carriers?
29 months
68
Hepatocellular carcinoma (HCC) in WHV positive woodchucks
- Histo: densely packed tumor cells in thick, irregular trabeculae, basophilic cytoplasms, large vesicular nuclei, prominent nucleoli
- Elevations in serum alpha-fetoprotein or serum GGT
- Clin signs: asymptomatic; anorexia, weight loss, lethargy
- Death frequently preceded by encephalopathic episode with elevated blood ammonia and/or hypoglycemia
69
Herpes virus of marmots (HVM)
- No clinical signs or death
- Lysis of hepatocytes by HVM in tissue culture
- NO association btwn HVM status and outcome of WHV infection
- Isolate virus from blood, lymphocytes, saliva, urine, rectal/genital swabs
- Transmission: venereal from males to females, from mother to offspring
70
Rabies in woodchucks
- Rare, but increasing in eastern US
- Clin signs: CNS signs incl aggression, unprovoked attacks
- Ddx: cerebrospinal nematodiasis (Baylisascaris sp.)
- Dx: Direct immunofloescent antibody staining of brain tissue
71
Powassan virus in woodchucks
- Flavivirus; causes encephalitis in humans
- Woochucks are reservoirs
- No clinical signs in woodchucks
- Vector: Ixodes cookei
72
Parasites that may persist in laboratory woodchuck colonies
Giardia spp., Entamoeba muris, Citellina triradiata
73
Parasites in woodchucks associated with hepatic lesions
Ackertia marmotae & Capillaria hepatica
74
Giardia sp. in woodchucks
- Harbor in small intestine
- Unclear if it causes clinical signs in woodchucks
- Unclear if transmissible to humans from woodchucks
- Dx: cysts in feces using zinc floatation; trophozoites in fresh fecal smear; ELISA
- Tx: Metronidazole (10-25 mg/kg PO once daily x 5 days), albendazole (25 mg/kg BID PO x 4 days), fenbendazole (50 mg/kg PO once daily x 10 days)
75
Entamoeba muris in woodchucks
- Nonpathogenic protozoan amoeba of rodents
| - Found in ~50% of woodchuck fecal samples
76
Eimeria sp. in woodchucks
- 4 species: E. monacis, E. os, E. perforoides, E. tuscarorensis
- No groos lesions in woodchucks
77
Toxoplasma gondii in woodchucks
- Woodchucks are intermediate host - infx by ingesting cat feces or transplacental migration of tachyzoites from mother
- No clin signs or gross lesions
- Cats are definitive host
78
Sarcocystis sp. in woodchucks
- Bradyzoites have been found in woodchuck muscle
| - No clin signs or reactions reported
79
Ackertia marmotae
- Adults present in lymphatics of liver and gallbladder, rarely in lung and kidney
- No inflammation or lesions
- Microfilariae in skin cause microfilarial dermatitis
- Intermediate host: Ixodes cookei
- Eliminate from colony by manual removal of ticks & tx with insecticidal powder on arrival to colony
80
Baylisascaris sp. in woodchucks
- B. procyonis (raccoon) & B. columnaris (skunk)
- Encephalities d/t larval migration to brain in woodchucks
- Clin signs: abnormal behavior, increased tameness or viciousness, head tilt, circling, paralysis
- Ddx: Rabies = so tx NOT recommended!
- Dx: Immunoflorescent antibody staining of brain tissue to R/O rabies, histo exam of brain tissue or examine Baermannized brain tissue
81
Citellina triradiata
- Pinworm found in cecum and large intestine
- No clinical signs
- Sanitation and single housing reduce incidence of infection
82
Obeliscoides cuniculi
- Common in wild woodchucks; short-lived infection in captive woodchucks
- Found in stomach, sometimes causes petechiae of mucosa
- Natural host: wild rabbit
- Larvae and adult forms do not survive hibernation of host
83
Taenia crassiceps
- Tapeworm of large canids- large, fluid-filled masses containing hundres of cysticerci
- Woodchucks ingest infected eggs - embryos migrate - replication occurs by budding w/ many cysticerci in a single cyst
- Masses most common in axilla & adjacent thoracic wall, sometimes SC abdomen or thorax, liver or lung
- Tx: surgical removal of masses is possible - be careful not to rupture the cyst
84
Taenia mustelae
-4-6 mm cysts on the surface and in parenchyma of liver containing cystecerci & calcified pus
85
Dicrocoelium dendriticum
- Lancet liver fluke
- Found in bile ducts of sheep, cattle, pigs, deer, cottontail rabbits, woodchucks
- Fluke eggs eliminated in feces of definitive hosts & ingested by snails - cercaria develop in snails & secreted in snail mucus & ingested by ants - definitive host ingests ants while grazing - metacercaria migrate up common bile duct
- Scarring of liver
- Histo: perilobular cirrhosis in sheep and woodchucks
86
External parasites of woodchucks
- Androlaelaps fahrenholzi - mite
- Endeleinellus marmotae - louse
- Orpsylla arctomys - flea
- Ixodes cookei - vector for Acketrtia marmotae & Powassan virus; Rocky Mountain Spotted Fever, B. burgdorferi
- Tx: manually remove ticks; organophosphate-containing powders
87
Capture myopathy
- Gross: discrete, pale, white muscle
- Histo: swelling, loss of cross striation with hyalinization or fragmentation, occasional mineralization
- Clin signs: lethargy
88
White muscle disease
- Insufficient intake or bioavailability of Vit E and/or selenium
- Lesions indistinguishable from those of capture myopathy; seen in muscles used most often - upper forelegs, hindlegs, cranial dorsum (hypaxial and epaxial muscles), heart
- Clin signs: wekaness, dysphagia, reluctance to move
- Histo: dark pink stained, swollen muscle w/ fragmentation, mineralization; chronic cases - muscle atrophy and fibrosis
89
Hepatic lipidosis
- Inadequate food intake, chronic debilitation illness, failure to adapt to laboratory conditions and diet from wild, hepatotoxic medication
- Example: antiviral drug FIAU
90
Traumatic injuries in woodchucks
- Bite wounds: head, neck, limbs; usually during breeding season
- Jumping out of cages: broken incisors, fractured limbs; broken incisors may grow back but need to trim opposite incisor; simple fractures can heal with cage confinement
91
Catheterization complications in woodchucks
- Localized infections and septicemia common - clip and prep area first!
- Apply topical antibiotic ointments and give parenteral antibiotics for catheterization & surgeries
92
Other iatrogenic conditions in woodchucks
- Gait abnormalities d/t repeated IM injections & subsequent fibrosing myositis
- Ateriovenous fistulas at venipuncture sites, esp inguinal area - cardiomyopathy, heart failure, death d/t rupture and hemorrhage
- Thrombus formations at catheter sites
93
Most common neoplasia in woodchucks?
Hepatocellular carcinoma - mets outside of liver rare; neoplastic cells arranged in sheets or cords without portal structures or lobar architecture
94
Other neoplasms in woodchucks
Testicular teratoma, seminoma, Sertoli cell tumor, testicular lymphosarcoma, interstitial cell tumor and adenoma of the rete testis, lymphosarcoma, meningioma, fibrosarcoma, uterine leiomyoma
95
Common neoplasias in woodchucks other than HCC?
Lymphoma, seminoma, interstitial cell tumors of testicle, myeloproliferative disease
96
Diaphragmatic hernia in woodchucks
- Seem to have natural weakness in the dorsal portion of the diaphragm
- Pressure during restraint may enlarge opening and allow herniation of omentum or abdominal organs
- Clin signs: dyspnea, tachypnea, muffled thoracic auscultation - signs d/t pulmonary atelectasis
- Dx: can be challenging, rads and U/S may or may not show
97
Ringtail in woodchucks
- 7-28 days of age
- Humidity levels <50%
- Annular constriction of the tail - progress to edema, inflammation, necrosis, sloughing of tail distal to constriction
98
Cardiovascular conditions in woodchucks
Arterosclerosis, aortic rupture, cerebrovascular and cardiovascular disease
99
Cardiomyopathy in woodchucks
- Clin signs: respiratory distress, ascites, SC edema, muffled heart sounds, heart mumurs, arrhythmias, sudden death
- Dx: rads and U/S; grossly enlarged heart at necropsy (normal hearts weigh avg 11.6 g +/- 2.8 g)
100
Aortic rupture in woodchucks
- Common cause of death in woodchucks older than 2 yrs
- No premonitory signs
- Young woodchucks dying from aortic rupture more likely have concurrent glomerulonephritis, interstital nephritis - suggests systemic hypertension involved
101
Cerebral and cerebellar hemorrhage in woodchucks
- May be assoc w/ arteriosclerosis of the brain
- Vascular hypertension and atherogenic diets are possible causes
- Vascular disease including vessel rupture may be linked to renal disease, vasculitis, associated hypertension
- Immune-complex deposition in glomerular capillaries related to hepatitis virus?
102
Renal disease in woodchucks
- Interstitial nephritis, glomerulonephritis, tubular nephrosis, pyelonephritis
- Clin signs: lethargy, inappetence, weight loss, PU/PD, uremic odor, facial swelling, abdominal distension, neurologic signs, anasarca (typical of protein-losing nephropathy), enlarged kidneys
- Immune-mediated glomerulnephritis assoc w/ WHV infection - membranous nephritis more common in younger animals
- Woodchuck may be good model for gomerulonephritis assoc w/ HBV infx
103
Inflammatory bowel disease (IBD) in woodchucks
- Nonsuppurative IBD - lymphocytic plasmacyti enteritis, enterocolitis, enterotyphlocolitis, colitis
- Infrequent clin signs - diarrhea, ascites, lymangiectasia
- Can be assoc w/ necrotizing enteritis and bowel infarction, colonic-mesenteric volvulus
- Clostridium difficile may be involved in some cases
104
Rectal prolapse in woodchucks
- Rare condition seen in young woodchucks, pregnant dams, or dams that have recently delivered
- Assoc w/ colonic intussusception - intussusceptions required sx
- Tx: manual reduction and purse string suture
105
Colon strangulation in woodchucks
- Ascending colon is a short straight segment that is firmly attached to the body wall by the mesocolon, and two lops that lie free in the abdomen - the two loops occasionally twist upon each other = strangulation
- Typically found dead with no prior clinical signs
106
Intestinal obstruction in woodchucks
- D/t entrapment in diaphragmatic hernias, stricture formation by omental adhesions
- Clin sigs: Partial obstruction = anorexia, weight loss, depression; Total obstruction: sudden death
107
Alternative animal models for human hepatitis B virus
-Chimpanzees: cost and physical limitations; NIH policies restricting use
108
Woodchuck hepatitis virus classification
- Genus Orthohepadnavirus
- Family Hepadnaviridae
- Similar viral DNA polymerase and viral particles to HBV
- 22-nm spherical particles and related filaments found in the serum of infected woodchucks - composed of viral envelope proteins (WHsAg)
- Complete virions = 42-45-nm diameter, composed of exterior envelope (WHSAg), nucelocapsid or core protein (WHcAg) & dsDNA genome
- Identical replicative cycle of WHV compared to HBV
- Hyperendemic in wild woodchucks in mid-Atlantic states
109
WHV replication
- Transition of viral DNA to viral RNA comparable to retroviruses, BUT integration of viral DNA into the host genome NOT required for WHV (unlike retroviruses)
- Integration of WHV DNA sequencesinto host genome assoc w/ hepatocarcinogenesis
110
Liver changes due to WHV
- Chronic, active hepatitis in the nonneoplastic liver; scattered parenchymal hepatocellular necrosis, bile duct proliferation, early fibrosis
- Well-differentiated HCCs with hperchromatic nuclei and prominent nucleoli
- Mets uncommon, but pulmonary mets have been observed
111
Hepadnavirus infections in other mammals
- Ground Squirrel Hepatitis Virus (GSHV 1) - California ground squirrels; frequency of associated HCC less than WHV & develops at older age
- Artic Ground Squirrel Hepatitis Virus (AGSHV) - in Spermophilus parryi (artic ground squirrel); very high rate of HCC
- Putative Hepadnavirus - Eastern gray squirrels (Spermophilus carolinensis); hepatitis seen but NOT hepatic tumors
- Hepadnavirus infection in Richardson's ground squirrels (Urocitellus richardsonii) resulting in HCC
- Wooly monkey hepatitis B virus (WMHBV) - Woolly monkey (Lagothrix labotricha)
112
Hepadnavirus infections in birds
- Duck hepatitis B virus (DHBV) - first reported in Pekin ducks; worldwide distribution (Anas domesticus)
- Heron hepatitis B virus (HHBV) - in gray heron (Ardea cinerea)
- Snow goose hepatitis B virus (SGHBV) - in snow geese (Anser caerulescens)
- White stork hepatitis virus (STHBV) - in white stork (Ciconia ciconia)
- Crane hepatitis virus (CHBV) - in Demoiselle crane (Anthropoides virgo) & Gray crowned crane (Balearica reglorum)
- Parrot hepatitis B virus (PHB) - in ring-necked parrot (Psittacula krameri)
- Hepatic neoplasms NOT assoc w/ heron HBV infx
113
Experimental chronic WHV infection
- Treatment with immune suppressive doses of cyclosporine A significantly increases the rate of chronic WHV infection
- Clearance of experimental WHV infx in adult woochucks is associated with robust humoral and cell-mediated immune responses
- Attempts to infx juvenile and adult woodchucks with chronic WHV often produce self-limiting, acute disease only
- Infection early in life (possibly in utero) needed for chronic carrier state in most cases
- Inoculated negative woodchucks at birth with diluted serum from standardized infectious pools obtained from chronic WHV carriers (rate of chronic WHV with this method 60% or greater)
114
Sex influence on HCC development
- Sex of experimental woodchucks does NOT influence rate of WHV associated HCC
- In humans and mice with HBV, males tend to have higher rates of HCC
- May be related to woodchuck decrease in testosterone production for 8 mths of the year
115
Other syndromes associated with WHV infection
-Immune-mediated glomerulonephritis - like glomerulonephritis in humans assoc w/ chronic HBV infx
116
Cross species hepatitis virus sensitivities
- Woodchucks can be infected with ground squirrel hepatitis virus (GSHV)
- Chipmunks (Eutamias species) also susceptible to GSHV infection
- WHV has greater oncogenic capacity than GSHV
117
Hepatitis viruses oncogenic ability
Integrated viral DNA (like retroviral proviral DNA) causes malignant transformation by insertional mutagenesis - alteration of expression of genes that regulated cell cycle
- Activation of c-myc as observed in 10% of WHV HCC tumors
- N-myc messenger RNA overexpressed in 60% of woodchuck HCCs
118
N-myc gene in woodchucks
- Woodchucks have 2 N-myc loci
- One locus is homologous to the N-myc gene of other mammals
- The other is an intronless gene with the characteristic structure of a retrotransposon = N-myc2 - located on X chromosome
- Brain is the only normal tissue of the woodchuck where N-myc2 RNA was detected
- Viral integrations appear to be preferentially associated with the N-myc2 locus
- Transgenic mice carrying the N-myc2 gene under the control of WHV regulatory sequences are highly predisposed to liver cancer
119
Gene activation/suppression in WHV HCC
-Activation of N-myc2
-Diminished expression of p53
(Shown in transgenic mice)
-Overexpression of HBX 1 required for malignant transformation of the cell line - HBX known to promote hepatocarcinogenesis in c-myc transgenic mice
-Woodchuck hepatitis X (WHX 1) protein is coexpressed with WHCAg in liver of chronic carriers - WHX/p53 complexes demonstrated chronic carrier livers
120
C-myc expression
-More common in GSHV ground squirrel neoplasms than woodchucks
121
WHX and p53 interaction
Binding of WHX to p53 may prevent entry of p53 into the nucleus, diminish tumor suppressor activity, and represent an important mechanism by which the hepadnavirus X-gene product could promote hepatocarcinogenesis
122
Hepatocellular injury hypothesis for HCC in WHV woodchucks
- Hepatic injury and hepatocellular regeneration provide environment that enhances spontaneous mutations, rearrangments, or chromosomal translocations
- Chronic liver injury with cirrhosis frequently precedes HCC in people infx w/ HBV
- In transgenic mice, direct relation btwn expression and retention of HBsAg in hepatocyes and severity of hepatitis; close correlation btwn severity of hepatitis and development of HCC
123
Aflatoxin and HCC in woodchucks
- When administered early in life to woodchucks experimentally infx at birth with WHV, aflatoxin B did not increase the rate of chronic WHV infx or rate of HCC
- When administered beginning at 1 year of age to established chronic WHV carriers, the time to tumor was sig REDUCED by aflatoxin B1 tx (also seen in tree shrew)
124
HBV transgenic mice
-When exposed to nitrosodiethylamine (NDMA1) or aflatoxin, developed hepatic adenomas and HCC more rapidly & extensively than unexposed transgenic control or normal mice receiving either carcinogen
125
NO production in liver and HCC
- In the liver, NO biosynthesis from argmme is catalyzed by inducible NO synthetase
- Endotoxin, y-interferon, and other cytokines can increase the activity of this enzyme significantly
- NO production in liver may protect against experimental hepatic injury, but may also contribute to development of hypotension with septic shock
- Chronic WHV woodchucks excrete more nitrate in urine and have more NMD - nitrate and NDMA derived from NO produced rom L-arginine
- Increased NO production in transgenic mice
- NO could act as carcinogen indirectly by causing formation of hepatocarcinogenic nitrosamines like NDMA; point mutations can be induced by NDMA by methylation of guanine & adenine
- NO can also be a direct mutagen - deaminate guanine and adenine
126
Antiviral therapy testing in woodchucks
- First tested against HBV cell line (HepG2 cell line)
- High antiviral activity agents in woodchucks: Adenine-5' arabinoside monophosphate, 1-(2-Deoxy-2-fluoro-Beta-D-arabinofuranosyl)-5-iodouracil, L-FMAU/clevudine, Lobucavir, Lamivudine, Emtricitabine
- Extended lamivudine treatment delayed development of HCC (very high rate of polymerase gene mutations detected in both humans and woodchucks after long-term lamivudine tx)
