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lab animal
11/3/98

stuart leland, DVM, ACLAM 

guinea pigs, 
hamsters, gerbils, chinchillas, and hedgehogs

[brief introduction about 
lab animal stuff in general]

the Hamster: we will focus on hamsters.


Rodentia, Cricetidae, Mesocricetus auratus
current US hamsters are 
derived from an initial 3 or 4 breeding pairs. most of the strains are 
golden hamster, aka syrian hamster. the other strain sometimes seen is 
chinese hamster which is grey with a black dorsal stripe.

hamsters are 
pretty aggressive. They are desert animals with low water intake 
requirements. they excrete concentrated urine. they are permissive 
hibernators - will hibernate when very cold, or if food is low -b ut do 
not need to  hibernate. are nocturnal.

they have sebaceous flank glands 
aka scent glands, on dorsolateral flanks. both sexes have them, more 
prominent in the male. hamsters also have huge cheek pouches which the 
unitiated sometimes think are tumors.  the pouches are cool - they are 
lined with squamous epi, very vascular, but with no glands or lymphatic 
drainage. so it's an immunopriveleged site, like the uterus. so in 
research, they will use these to grow tumor cells - they implant 
xenotumors into the lateral cheek pouch and they will grow. 

sexing 
hamsters is similar to sexing other rodents. anogenital distance is 
larger in males than in females. females are also larger in general, and 
her butt sort of tapers into a tail, whereas the male has a scrotal 
bulge.

uses in research: in vivo tumor cell growth, other oncologic 
studies since low rates of natural neoplasia and low number of indigenous 
viruses. 

hamsters are also radioresistant - you can put human tumors 
into lateral cheek pouches and test radiation therapy on them in high 
doses that might be lethal to other species without killing the hamster.


normal parameters - urine is normally milky white due to high 
concentration of Ca Carbonate, and urine normally alkaline.

hibernation 
is optional - client may call asking why hamster is moving so slow, not 
eating, etc. decreased daylight, cold temp and decreased amounts of food 
promote hibernation. usually lasts a few days. they are sensitive to 
tactile and thermal stimulation. they have lowered temp, HR, RR.


handling: remember they are aggressive, not good for kids. if you get 
them young you can work with them but it takes time. they are curious by 
nature so if they do get used to you they can do well. restraint: hold on 
back, splay front legs out, thumb supporting back end.you can also 
manually scruff the hamster by grasping the loose dorsal skin, so you can 
deal with the underside of the hamster.

if you want client to like you, 
put a container in there, put some food in there, and hamster will go 
into the container and you can pick up the hamster. also you can make 
your hand into a container. hamsters are phigmotactic, liking vertical 
spaces and enclosures (heh?)

repro: they are seasonal, usually quiescent 
in winter. they ovulate every 4 days. end of ovulation is characterized 
by copious white, snotty, mucoid vaginal d/c. so, count 3 days after the 
d/c and that is when she should ovulate so put in with male that day. day 
one = ovulation, day 2 = d/c, day 5 = put in with male, will ovulate 
again.

mating behavior - female will be receptive and exhibit lordosis, 
or she will give a "touch me and you die" signal.so watch them 
investigate each other first. if she isn't receptive, get her out of 
there or she'll kick his ass. 

gestation = 15-18 days, probably that 
number is one you should know b/c it is the shortest one of any commonly 
used lab species. on day 8, there are hourly changes you can observe in 
the embryo which makes them useful to study embryology and teratology.  
for parturition - females will cannibalize young if stressed or nervous, 
so isolate her a couple of days before parturition, give nesting 
material, and do not disturb her for 7-14 days postpartum. primiparous 
females are more likely to cannibalize than multiparous.

sick hamsters - 
hunched over, ruffled fur. typical sick rodent. 
runting - may be seen


proliferative ileitis aka wet tail: clients call this "wet tail" or one 
of any number of synonyms. used to be thought to be diffuse 
adenocarcinoma of ileum. causative agents are not known for sure. the 
disease has long been associated with gram negative, curved rods present 
in apical enterocytes at crypt level. intracellular, campylobacter like 
organisms is what they've been called. but we can't fulfill koch's 
postulate here. so causative agents have had multiple names, most 
recently lawsonia intrecellularis, similar to that which causes 
intestinal adenomatosis in pigs and proliferative colitis in ferrets. 
stress, crowding is correlated iwth it. fecal/oral transmission. most 
often seen in postweaning period. genetic predisposition exists.
slide: 
affected guts. corrugated, granulomatous distal small intestine.
slide: 
histo of normal cecum with normal villi
slide: histo of affected cecum 
with humongous villi, showing marked extension of villi. organism is in 
crypt epithelium, in apical intracytoplasmic space. gram neg, curved 
rods.

as it progresses, you can get abscess formation down extending 
from crypts to muscularis. grossly, white spots along ileal surface. as 
it goes further, you get serosal granulomatous lesions appearing. 


slide: TEM of normal cecum with little traffic cone type villi
slide: 
advanced ileitis with long wierd villi
slide: end stage - flat, fibrotic 
surface

prognosis is very bad. can respond to some symptomatic tx such 
as tetracycline, sq fluids, kaopectate. even if they recover from initial 
bout, fibrosis will occur, lumen can scar down, and obstructive disease 
can occur. 

viral dz of hamster: LCM - lymphocytic choriomeningitis - 
significant virus in pet hamsters b/c it is zoonotic. in people, presents 
as low grade, flulike signs, not feeling well, overall malaise - but can 
progress to choriomeningitis. natural host is the mouse. in hamster, 
virus can propagate to very high titers, and can persist. in hamsters, 
signs - usually asymptomatic, sometimes growth retardation, sometimes 
death. hamster can excrete virus by urine and aerosol at high levels so 
can spread to people. true story: woman came to vet - "I have this awful 
headache, and just found out my daughter used my toothbrush to clean her 
hamster's cage. could there be a connection?"

transmissible lymphoma - 
spreads among hamsters, can cause epizootic. due to hamster papovavirus 
which acts as transforming virus. seen in mesenteric LNs most often, can 
be cervical or axillary. doesn't usually involve spleen. 

papovavirus in 
older animals can cause trichoepitheliomas, keratinizing tumors of hair 
follicles. here, unlike with lymphoma, you can find replicating virus in 
the tumors. 

there's no test for this papovavirus. diagnosis is via high 
degree of suspicion, clinical signs, etc. virus is very stable in 
environment. decontamination won't necessarily get rid of it. tx = 
depopulation with no guarantee you've cleaned up well enough to 
repopulate.

hamsters are susceptible to antibiotic toxicity as are 
g.pigs, rabbits, chinchillas. if you give an abx they are susceptible to 
you wipe out normal flora allowing anaerobic proliferation. avoid PCN, 
erythromycin, cephalosporins, aminoglycosides esp neomycin and 
streptomycin which cause ascending flaccid paralysis 

amyloidosis - 
common aging dz of hamsters - nephrotic syndrome may occur, spleen 
infiltration with amyloid, etc. hamster presents with Fanconi syndrome 
-of ascites, proteinuria, low oncotic pressure, pitting edema, etc. 
adrenals, liver also affected. atrial thrombosis may also occur, 
typically left auricle/atrium, leading to left sided CHF. heart may get 
huge. common in aged hamsters, associated with amyloidosis. 

end of 
hamster talk.

Gerbils: mongolian gerbil aka jirds or sand rats
brought 
to US from mongolia in mid 50s. usually agouti color (sandy brown), with 
hair on their tails. will often stand up on hind limbs. large hind limbs, 
can jump high - 18 inches no problem. will explore in upright position. 
they also have strong claws for burrowing. come in black and grey, too.

these animals are nonaggressive, curious, and social (unlike hamster)

nocturnal
breed in monogamous pairs
males assist in raising young
very 
large back feet - may stomp when excited or as warning 
rather desirable 
as pets, compared to the evil vicious hamster :)

the ventral marking 
gland is present in males and very prominent, but not visible in the 
female although still histologically present. 
gerbils have huge adrenal 
glands, too.
gerbils normally have chromodacryorrhea - red tears, due to 
hardarian gland sitting near eye, remember we talked about this with 
rats, this is normal in gerbils, the porphyrins cause red staining around 
eyes and nose. it isn't bloody nose, or bloody tears.

incomplete circle 
of willis is present so you can ligate a common carotid and cause 
cerebral ischemia, used for stroke research. also high incidence of 
spontaneous epilepsy. 

like the hamster, not many naturally occuring 
spontaneous dzs, but are susceptible to dzs of other spp.

again - big 
hind legs, so need bigger/taller cages than other rodents. 
desert 
animals - urine and feces very concentrated - nice from husbandry 
perspective. can change cages every 2 wks. 
naturally lipemic on normal 
rodent diets - high serum cholesterol.

handling gerbils - grab by base 
of tail. they have a furslip escape mechanism like chinchillas - fur and 
a couple of layers of epidermis can peel off, leaving the tail with no 
covering. it will grow in over weeks/mos. so grab base of tail and scruff 
of neck, not end of tail. 

breeding pairs must be put together before 
puberty, or else female may not accept male. once established, if one 
dies, other usually will not accept another mate. whereas hamster is 
removed from cage and rears young by herself, for gerbils you have to 
leave them together b/c he assists. if you have to treat one of the 
breeding pair, realise you should only separate them briefly or they may 
not accept eachother when you return them. 

tyzzer's dz - gerbils are 
exquisitely sensitive to this organism, a clostridial piliformes, 
obligate intracellular gram neg rod. spore forming. spores last mos  to 
years on environment, so it is hard to clear from a colony.
gerbils often 
die of this. if gerbil is near it, it will get it.
signs: perineal 
staining, diarrhea - most common sign is sudden death.
gerbil is unique 
in that it can spread to brain and cause suppurative encephalitis. 
tyzzer's affects other rodents too - classic triad of signs is liver, 
intestine, heart - white spots on liver is common. focal necrosis. 

before it was reclassed as an anaerobic clostridial organism, it was 
often dxed on histo with silver stain - can find them on periphery of 
lesions.
tx: supportive care, oxytetracycline works in mice, probably not 
so in gerbils. 

sorenose - unique to gerbils. no one knows the cause. if 
you culture it you will get staph. most feel it is a secondary staph. 
harderian gland secretion may be part of cause - may irritate the nose. 
secretion increases with stress. enzymes in secretion may caues 
irritation leading to rubbing, scratching, and secondary staph infection. 
this is proposed. not known. 

tx of sorenose - change bedding to sand, 
try antibiotics, topicals. make sure to avoid the drugs listed as ones to 
avoid. 

no naturally occuring viruses are reported in gerbils

the 
gerbil pinworm, dentostomella translucida - was on his national boards.

gerbils are susceptible to spontaneous seizures, incidence 20% but 100% 
in some lines, is heritable. no tx. they get over it. do not use any 
dilantin or phenytoin, can be fatal. 

another common age change is 
cystic ovaries. 
chinchilla - related to g.pig. originated from south 
america, high altitude, up in andes mountains. they used to be nearly 
extinct b/c of fur valuation, but now are protected by federal law. they 
live a long time, they are hindgut fermenters like rabbits - remember 
chinchi, rabbit, g.pig, and hamster are all susceptible to abx toxicity. 
they have large ears which is why they are often used in research for 
auditory studies since their tympanic bullae are so well developed. low 
susceptibility to otitis media. 

they require dust baths. mixture of 
sand and some kind of earth. they get into bowls of dust and roll around. 
they need this daily. keep bowl in cage, let them do it, then remove it. 
if you leave it in there, make sure to clean it frequently. 
in research 
they are used often - female will have metal collar put on, then she's 
put into a cage. there is a tunnel in back of cage, and male can run in 
and out. when she is receptive, he will jump in but she can't get out b/c 
of her collar.

disease:highly susceptible to listeria, usually show 
vestibular signs. chinchis do not have high incidence of otitis media so 
think listeria if you see that. can be fatal in them. they come from the 
Andes and are well adapted to low temps, poorly adapted to high temps, 
can easily get heatstroke. 
if they are put near the radiator in winter 
they will not do well.

hedgehog - very cute. these are a fad pet right 
now, characterized by porcupine like projections on their dorsum. their 
faces/underbellies have soft white fur. originated from british islands, 
now all through europe, africa, asia. insectivores - good for the garden. 
eat slugs! woo! when nervous they don't move too fast, they curl into a 
ball. try stroking back end to make them unravel. when they explore they 
lick any new object they find, then do this weird rumination motion, and 
get frothy stuff in their mouth which they then deposit onto their caudal 
ventral areas. 
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joan cole
guinea pigs

all info is in 
handout.
five important things to know about guinea pigs will be pointed 
out to us :)

gpigs are south american rodents. not like rats/mice. they 
separated sooner than rats/mice from evolutionary tree.

"guinea pig" 
perhaps b/c they squealed like pigs and travelled through Guinea when 
imported to europe.

Cavia porcellus - related to porcupine. tailless, 
four digits on front feet and three on hind.

varieties: 
english or 
american
abyssinian

different colors - creams: buff is darker
lilac - 
born sort of dark and lightens
chocolate and black - tell apart by ear 
color, lighter in chocolate.
beige
agouti
himalayan aka dutch
torti
white 
crested
abyssinian is a hair thing, where hair is curlyish
peruvian has 
long hair, also called ragmop
"wooly" - short, coarse hair, pretty fuzzy


lab strains - english/american shorthair. Hartley G. pig -common outbred 
stock. 
hairless guinea pig used in dermal studies. normal immune system, 
just hairless. 

anatomy - a couple of things you might need to know - 
compact, stocky bodies, short legs, tailless. like most rodents, prone to 
overheat since no sweat glands. normally would burrow to cool off. 
sebaceous glands present circumanally and on rump - sometimes used to 
mark. males get scrotal plug around prepuce. two pairs of mammary glands, 
can raise several pups in a litter.

teeth grow continuously - not just 
incisors but premolars may overgrow. if you think teeth are overgrown, 
might be easier to xray instead of trying to pry mouth open.
can be 
polydactyls with extra toes!

pubic symphysis separates during 
parturition due to relaxin
tympanic bulla very large
sensitive smooth 
muscle in bronchial tract, very sensitive to histamines so have 
anaphylactic reactions.

perivascular lymphoid nodules in lungs, around 
venules and arterioles - incidental findings. 

GI system - cecum is 
biggest most imporrtant part. has balanced bacteria, susceptible to 
imbalances. 

repro - the boar has an open inguinal canal so you have to 
close it when you do castration surgery or you could have herniated 
intestines. do not confuse large seminal vesicles iwth a uterus!
sow has 
vaginal closure membrane open only during estrus and parturition


physiology: kurloff cell - unique to g.pig

g.pigs can live 8-9 yrs but 
only usually 5 yrs as pets.
lymphocytes are prevalent leukocyte
kurloff 
cell - granulated, vacuolated WBC from spleen, thymus - stimulated by 
pregnancy, estrogen, common in placenta.
RBC, Hb, PCV lower than other 
rodents - see chart in handout.

blood collection fairly difficult - 
simplest to clip a toenail. can get blood from jugular, tarsal, other 
veins, but takes practice. 
urine is opaque, creamy yellow.
resemble man 
more immunologically and hormonally than rats, mice.
repro research often 
done.

need to know: most diseases with G. pigs due to *poor husbandry* 
b/c people do not know how to maintain them properly. always review 
husbandry with owners.
can keep in solid bottomed cage, slatted bottomed 
cage. wire bottom not good - can hurt feet, get sores. also do not like 
to change from one type to another.
can't climb/jump well - can be in 
open container. humidity about 50% is best. 

nutrition ** most important 
to remember their vitamin C requirement. other rodents do not have this. 
so you can't feed rabbit food or whatever, they need g.pig food. they are 
fastidious eaters and if you change their food abruptly they will not eat 
it, they may starve. 
use g. pig food, and look at the date on it. some 
pet shops sell it in bins that are open - it shouldn't be over 6 mos old 
if stored at 50 F, if not only good for about 4 mos. they like to sit in 
their food bowls. handout suggests hanging all the food bowls. really, 
just wash the bowl and clean the water bottle frequently.

vitamin c 
requirement is discussed in handout - there are supplements to add to 
food. some people like to feed lettuce and carrots - so make sure to find 
out what the G. pig is eating. if a whole variety of veggies, fine, but 
if just carrots, maybe it isn't eating enough C. some people do not like 
to supplement them, but as pets, it's probably fine to do. sure, wash the 
food first, it shoudl be ok. 

behavior - very docile, easy to work with, 
but very sensitive. 
handling: don't pick up by one end. use two hands, 
support the body. can cradle them against your body. they exhibit some 
characteristics - the scatter response is important if you are raising a 
bunch of them they can sort of stampede and hurt eachother. immobility 
response - can get "frozen" for up to 20 minutes. that is normal. 
barbering - may chew hair off eachother like mice do.

they are fairly 
social, like to hang out with other guinea pigs.

repro ** important 
point to know. 
females pubic symphysis must separate to deliver pups, 
and if not bred by 6 mos the symphysis can fuse. 
a little hard to 
visually sex male vs female
slide: pregnant g.pig - huge caudal abdomen

newborns are very large
slide: four pup litter.

estrus - nonseasonal, 
continually polyestrus, spontaneous ovulators, usually breed at night, 
form vaginal plug after mating. more info in handout.
gestation 59-72 
days - long for rodent. optimal 69 d, avg 63. more pups, shorter 
gestation. 

parturition is called farrowing. there is no nest building. 
the pubic symphysis starts to separate and will be at 22-30 mm prior to 
parturition. hair loss common in pregnant sow. pups shed out when they 
get adult hair, too. abortion and stillbirth common. newborns are 
precocious but should nurse 14-21 days. they may not choose to nurse for 
first day. they need to stay with mom to get stimulated to urinate 
though. moms will nurse other pups - make sure small ones get a chance. 


breeding systems - can leave males in continuously
can do c-section on g 
pigs, pups usually survive. moms will foster readily. 

diseases:

husbandry is biggest cause
nutrition is second biggest cause (lack of C)

main etiology of dz is bacterial 
they have antibiotic sensitivity

parasits, mycosis
viral dz and neoplasia are rare

there is discussion of 
abx toxicity in handout, list of drugs ok to give. topicals can cause 
toxicity!

bacterial pathogens - you should know ** that many of these 
can be cultured from normal pigs, they just get sick when stressed. being 
cold, having dirty or wet cage can induce pneumonia. bordetella 
bronchiseptica is pathogenic to g.pigs. can catch from dogs. can get 
streptococcus pneumonia. very susceptible to tuberculosis. they can catch 
it and give it back to people. they get otitis media. they get 
torticollis. they are susceptible to salmonella which can cause acute 
death, but rarely causes diarrhea. can be zoonotic.
yersinia pseudoTB can 
cause weird neck abscesses, can lead to acute death, emaciation.
tyzzer's 
dz uncommon in g.pig.
cervical lymphadenitis common - strep zoo or other. 
may be secondary to oral abrasions? these animals can get septicemia if 
you drain the abscess but you have to try it and usually it is ok, no 
septicemia.

pododermatitis from diry wire cages or fat g.pigs.


chlamydia psittaci - colony of g.pigs may get weepy red eyes 1-3 wks of 
age.

viruses: g.pigs relatively free of viral dz. 
can carry LCM which 
is zoonotic, possibly fatal in people
they have a CMV, adenovirus, murine 
polovirus, cavian leukemia

parasites can occur - 47 spp of protozoa 
naturally present. few clinical signs if any associated with 
endoparasites. crypto can cause problems. eimeria may cause problems esp 
with stress. klosiella cavia - no signs. toxoplasma - may cause acute 
mortality. not usually clinical entity
encephalitozoon - not usually 
clinical entity
cecal pinworm
fasciola liver flukes from contaminated 
greens in diet
lice more common than mites
"glicricola" louse more common 
than gyropus
signs of lice - usually none, sometimes scratching
mites not 
as common - trixacarus caviea is the sarcoptic mite, but isn't always 
very pruritic despite what it says in handout. tx lyme sulfur or 
ivermectin. lyme sulfur doesn't smell good but doesn't harm animal. 

other mites that don't cause problems or are rarely identified are in 
handout.

mycotic dz: trichophyton mentagrophytes - doesn't fluoresce 
under UV light. 
neoplasia: very rare. they have asparaginase in serum 
and kurloff cell may be anti-tumor

cavian leukemia/lymphosarcoma - can 
look like the strep abscess lumps they get.
trichofolliculoma - common, 
easy to remove skin tumor.

vitamin C deficiency: usually, people show 
you animals with tons of hemorrhage and they look awful but clinically 
there are subtle signs. if you see a sick g.pig, put vitamin C in the 
water just in case. put it in every day, fresh batch. could be not eating 
enough, or food is deficient, or whatever. signs of deficiency may vary, 
may be vague. 

metastatic calcification - seen postmortem, in older GP


malocclusion: teeth can grow across and trap tongue, can cause 
"slobbers". once you dx this trim teeth every few months. 

diabetes 
mellitus in one gropu of GPs.

pregnancy toxemia - uterus presses on 
arteries and veins causing loss of circulation, also they may not eat 
well, get ketoacidotic. within 2-3 days of parturition in primiparous 
pigs.

vit E /selenium muscular dystrophy can occur, too.

alopecia 
during switch from baby fur to adult fur will occur
fight wounds may 
cause dermatitis alopecia
alopecia may be due to barbering

heatstroke 
common, 
anyphylaxis can occur
GDV can occur
urinary calculi can occur


research uses - wide variety - repro, immunology, genetics, oncology, 
nutrtion, toxicology, etc. lots of serum complement for serologic 
testing.

FIVE POINTS ***
-vitamin c important in diet: always supplement 
C in diet of ill or stressed pig. put in in water, give fruit.
-husbandry 
important
-breed females before 6 mos
-abx toxicity occurs
-be careful 
with anesthesia

during stage III anesth, may retain limb movement, and 
further dosing may kill them. try a toe pinch - if they respond, they 
need more. if they do not respond, do not give more! anesth is very 
difficult in GPs. pay attention to drugs you give, and followup postop. 
see handout for drugs, dosages. 
some people still use pentobarbital but 
dangerous. innovar not good. inhalation hard to induce, b/c they hold 
their breath. recommended to use ket/xyl to induce, use gas to maintain 
if required (via nose cone)
need to prevent hypothermia. 
recovery - warm 
subcu fluids may be useful
give vitamin C supplement orally


differentials:

rough hair coat:
abyssinian, normal whorls. wooly - 
normally rough coat

skin swellings - she added two bacteria to list but 
i didn't catch them. 

slide: very sick pig.

public health concerns: 
very allergenic - not good choice for people with allergies. very 
susceptible to TB and can spread it back to people. other pathogens 
listed in handout. chart of drugs and stuff also listed in handout, as is 
a chart of physiologic values and references :)

see, she's stopping on 
time even though she lost 10 min to the previous lecturer.
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