Chapter 6. Biology and Diseases of Guinea Pigs Flashcards

Question 1

Q

What is the only New World rodent used commonly in research?

Answer

A

Guinea pig - Cavia porcellus

First domesticated by the Andean Indians of Peru; Dutch introduced to Europe in 16th century & bred by fanciers
Colors include white, black, brown, red, brindle, roan; may be mono-, bi-, or tricolored
Short regular hair (shorthair or English); longer hair with whorls (Abyssinian), long straight hair (Peruvian), medium-length fine hair (silky)

Question 2

Q

What stocks of guinea pigs are currently commercially available in the US?

Answer

A

Outbred pigmented stocks, albino Hartley stocks, and IAF hairless stocks
-Two inbred strains (strains 2 and 13) no longer available; strain 13 can be obtained from US Army Medical Research Institute of Infectious Dieases (USAMRIID)

Question 3

Q

What is the taxonomy of the guinea pig?

Answer

A

Order Rodentia has 3 suborders Sciuromorpha (squirrel-like rodents), Myomorpha (rat-like rodents), Hystrichomorpha (porcupine-like rodents)

Guinea pigs: Order Rodentia, Suborder Hystrichomorpha (currently controversial), Family Caviidae, Subfamily Caviinae, Genus Cavia

Question 4

Q

Family Caviidae

Answer

A

Five genera and ~23 species of South American rodents
Have 4 digits on forefeet and 3 digits on hind feet
Soles of feet are hairless, nails are short and sharp

Question 5

Q

Genus Cavia

Answer

A

Stocky bodies with a large head, short limbs and ears, single pair of mammae, vestigial tail

Question 6

Q

Axenic guinea pig

Answer

A

Guinea pig was first laboratory animal species maintained in an axenic state

Question 7

Q

Research uses of guinea pigs

Answer

A

Closely model human Vitamin C metabolism and airway reactivity in asthma

Anaphylaxis, asthma, delayed hypersensitivity, genetics, gnotobiotics, immunology, infectious disease, nutrition, otology, pharmacology, research in space
Pharmaceutical industry use: preclinical testing of cardiac safety of new drugs, hairless G pigs used for development of topical drugs
Medical device industry: sensitivity testing, source of serum complement in labs using the complement fixation test to diagnose infx dz

Question 8

Q

Blood collection in guinea pigs

Answer

A

Lack of tail and thick skin make blood collection relatively challenging
Can collect small volumes (~100 µl) from jugular, saphenous, cephalic
Collection of larger volumes from retro-orbital, cranial vena cava, terminal cardiac puncture

Question 9

Q

Guinea pig intubation & oral dosing

Answer

A

Challenging due to their unique pharyngeal anatomy - an elongated soft palate covers the back of the throat, leaving only the small palatial ostium for access to the trachea and esophagus

Question 10

Q

Guinea pig bedding

Answer

A

Solid bottom flooring recommended over wire (only use if necessary experimentally)
Guinea pigs given wood shavings and paper sheets spent sig more time during light cycle in areas of wood shaving, and had slight preference for paper sheets in dark conditions
Some bedding materials will interfere with animal tests involving ascorbic acid depletion because of presence of low levels of Vitamin C - cedar shavings

Question 11

Q

The Guide cage space requirements for guinea pigs

Answer

A

Animals weighing 350g or less: 60 in^2 floor space
Weighing more that 350g: 101 in^2
Height of primary enclosure should be at least 7 inches
Macroenvironmental temp of 20-26 C (68-79 F), relative humidity 30-70%, ventilation of 10-15 fresh air changes per hour with no draft, 12:12 light:dark cycle

Question 12

Q

Guinea pig feeding and watering

Answer

A

Do not adapt readily to changes in how feed and water are presented - need to observe animals often
Feed usually given in J feeder
Water usually given in bottles or by automatic watering system; automatic watering valves used in solid bottom caging should be located outside the cage to minimize wet or flooded cages

Question 13

Q

Learning in guinea pigs and tonic immobility

Answer

A

Positive reinforcement (operant conditioning) recommended
Aversive stimuli that induce anxiety or fear may induce in the guinea pig a profound somatic and autonomic motor inhibition known as TONIC IMMOBILITY behavior - also known as animal hypnosis or feigning death, mediated by periaqueductal gray matter, the limbic forebrain, and spinal areas; should NOT be used as a means of restraint

Question 14

Q

Circulatory and lymphoreticular system in guinea pigs

Answer

A

RBC indices (red cell count, hemoglobin, packed cell volume) relatively low compared to other laboratory rodents
Historical erythrocyte counts were lower than modern and historical mean white count was higher (subclinical disease)
Lymphocytes are predominant leukocyte in peripheral blood
Neutrophils (heterophils or pseudoeosinophils) have distinct eosinophilic granules in cytoplasm
Foa-Kurloff or Kurloff cell = estradiol-dependent mononuclear leukocyte unique to guinea pigs; found primarily in thymus, sinusoids of spleen, liver, and lung; increased # in circulation during pregnancy; large numbers in placenta - may have role in preventing maternal rejection of fetal placenta; has LARGE MUCOPOLYSACCHARIDE, INTRACYTOPLASMIC INCLUSION BODY - metachromatic and PAS(+), contains proteoglycans and hydrolytic enzymes similar to smaller intracytoplasmic granules in NK cells; has NK cytotoxic activity in vitro and may be part of cancer resistance in guinea pig
Guinea pigs, like ferrets and primates, relatively resistant to effects of steroids - thymic and peripheral lymphocytes not markedly reduced by corticosteroid injections
Guinea pig is model of genetic control of the histocompatibility-linked immune response
Thymus is located in ventral cervical region, easy to remove surgically but accessory thymic islets exist in contiguous fascia, has no apparent afferent lymphatic vessels

Question 15

Q

Guinea pig dental formula and oral cavity

Answer

A

2(I 1/1, C 0/0, PM 1/1, M 3/3) = 20

Diastema between incisors and premolars
All teeth are open rooted and grow continuously - hypsodontic
Incisors normally white (unlike yellow-orange in other rodents); upper incisors shorted than lower
Oral cavity small and narrow; soft palate covers nearly entire back of pharynx except for small palatal ostium = guina pig is OBLIGATE NASAL BREATHER

Question 16

Q

Guinea pig GI system

Answer

A

Monogastric hind-gut fermenters

Unlike other rodents, stomach is undivided and lined entirely by glandular epithelium
Cecum can hold 65% of total GI content
Gastric emptying time is ~2 hour
Cecal emptying time very slow
Total GI emptying time is ~20 hour
With coprophagy, entire transit time can be ~60-70 hour

Question 17

Q

Guinea pig cardiovascular system

Answer

A

Both a lower basal coronary blood flow and a lower peak coronary blood flow compared to rat

Intercoronary collateral network is well developed = cardiac infarct difficult to produce by acute coronary artery occlusion
Myocardiocytes are not as “stiff” compared to rat

Question 18

Q

Preyer or pinna reflex

Answer

A

Cocking of pinnae in response to a sharp sound

-Used in otologic studies as measurement of hearing function

Question 19

Q

Guinea pig ear

Answer

A

Advantages of using guinea pig ear include large bullae, ease of surgical entry to the middle and inner ears, protrusion of the cochlea and blood vessels into the cavity of the middle ear - allows exam of the microcirculation of the inner ear
-Two reported mutations causing inner ear malformation and ‘waltzing’

Question 20

Q

Guinea pig pituitary gland

Answer

A

Pituitary growth hormone is responsible for postnatal growth in vertebrates & removal of pituitary gland in most species alters growth pattern
-Hypophysectomy in guinea pigs does NOT alter growth rate & supplementation with guinea pig pituitary extract fails to alter growth rate of both hypophysectomized and normal guinea pigs

Question 21

Q

Somatomedins in guinea pigs

Answer

A

Somatomedines insulin-like growth factor I (IGF-I) and IGF-II are responsible for growth in guinea pigs

Unlike other species, somatomedins in guinea pigs are NOT growth hormone dependent & hypophysectomy does not decrease level of somatomedins
What regulates somatomedins in guinea pigs is unknown

Question 22

Q

Reproductive values for guinea pigs

Answer

A

First ovulation: 4-5 wks
First ejaculation: 8-10 wks
Breeding onset in males: 600-700g (3-4 months)
Breeding onset in females: 350-450g (2-3 months)
Cycle length: 15-17 days
Implantation: 6-7 days post ovulation
Gestation period: 59-72 days
Postpartum estrus: 60-80% fertile
Litter size: 2-5
Liter interval: 96 days
Weaning age: 180g (14-8 days)
Breeding life: 18 months-4 years (4-5 litters)
Milk composition: 3.9% fat, 8.1% protein, 3.0% lactose
Milk yield maximum: 45-65ml/kg body weight/day

Question 23

Q

Guinea pig diet

Answer

A

Feed diet specifically for the species and containing Vitamin C; most feeds now contain stabilized Vitamin C that can be used for 180 days

Some cases feed additional high Vit C foods: orange wedges, kale, cabbage
Commercial guinea pig pellets are ~18-20% crude protein, 9-18% fiber
Metastatic calcification has been assoc w/ diets low in Mg, with incorrect Ca:P ratios, or with extremely high levels of Vit D
“Imprint” food types early in life so may not recognize other foods (powdered, additives, vegetable supplements, etc.); placing powder in agar or blending foods for transition can help; guinea pigs scatter food and dribble water so measuring consumption is difficult

Question 24

Q

Guinea pig hierarchy

Answer

A

In mixed-sex groups, a dominant male hierarchy and a less defined female hierarchy develop

Scent marking with urine, anal, and supracaudal gland secretions and vocalization and agonistic displays used to assert dominance and defend territory
In harem breeding, a dominant female may be apparent by lack of fight wounds or hair loss from barbering
Sexually immature males can be housed together, but not recommended for adult males as can fight; shelters placed in group housed male cages reduce aggression

Question 25

Q

Guinea pig vocalizations

Answer

A

Use a dozen or more audible calls for various reasons including calls to increase proximity, greeting, proximity-maintaining calls, proximity-regaining calls, distress calls, alarm calls

Question 26

Q

Reproductive anatomy in male guinea pigs

Answer

A

Accessory sex glands include larger, transparent, smooth seminal vesicle (up to 10 cm in length), prostate, coagulating glands, bulbourethral glands, and rudimentary preputial glands
Testes remain in inguinal pouches & inguinal canals open for life
Os penis present

Question 27

Q

Reproductive anatomy in female guinea pigs

Answer

A

Uterus is bicornate & terminates in single os cervix
Vagina sealed by vaginal closure membrane - epithelial structure that ruptures just before onset of estrus and reforms after ovulation
Sows should be bred first when large enough to bear a litter but before calcification of the fibrocartilaginous pubic symphysis - calcifies and becomes fused between 6-9 months of age - prone to dystocia if first give birth after this fusion
Vendors first breed sows when 350-500g (5-13 weeks) and boars when 500-800g (7-13 weeks)
Spontaneous ovulators and polyestrous; have postpartum estrus
Heavily bred sows may cease hair growth, resulting in patchy alopecia

Question 28

Q

Estrous cycle in guinea pigs

Answer

A

~16 days (13-21 days)

Proestrus: 1-1.5 days, characterized by vaginal swelling, rupture of vaginal closure membrane, increased activity, nucleated and cornified epithelial cells on vaginal smear
Estrus: 8-11 hours, swollen congested vulva, perforate vaginal membrane, lordosis and rear quarters elevated
Metestrus: 3 days
Diestrus: 11-12 days
Fertile postpartum estrus occurs from 2-10 hour after parturition
Estrus can be synchronized with progesterone administered orally or as a SC implant
Vaginal impedence measureents can be used to assess stage of estrous cycle

Question 29

Q

Mating in guinea pigs

Answer

A

Boar makes one or two intromissions and then ejcaulates
Coital completion indicated by grooming, scooting, and perianal marking by the boar
Copulatory plug may be found in the female or bedding
~60-85% of matings, including postpartum matings, are fertile

Question 30

Q

Gestation in guinea pigs

Answer

A

68 days (59-72 days)

Blastocysts implant on day 6 or 7 of gestation
Placentation is labyrinthine hemomonochorionic, similar to humans - good model for reproductive toxicology studies
Fetuses can be palpated at day 15, 5mm diameter firm swelling
Fluid-filled round swellings apparent on U/S at day 16, diagnosis approaches 100% by day 19
Pubic symphysis separates to 3 cm during last week of gestation
Gestation length generally inversely proportional to litter size
Relaxin produced by placenta beginning around day 30 through about day 63 - responsible for loosening of the fibrocartilaginous pelvic symphysis
Sows do NOT build nests
Pups delivered every 3-7 min; completetion of parturition in 30 min
Large litters (3 or more) assoc w/ higher incidence of stillbirths
Dystocia can occur in sows bred for the first time after fusion of pubic symphysis, obese sows, sows with large fetuses

Question 31

Q

Development of newborn guinea pigs

Answer

A

Born precocious with hair, teeth, open eyes and ears, fully mobile
Begin to eat and drink within hours of birth; feeder and sipper tube may be lowered to provide access
Average birth weight 45-115g; pups weighing less than 50g at birth generally do not survive
Do not nurse for first 24 hr
Pup mortality of up to 50% can be seen if pups are undersized or do not receive milk from a sow during first 3-4days of life
Voluntary micturition does not occur until 7-14 days of age
Can be weaned at 14 days but generally weaned at 21 days

Question 32

Q

Artifical insemination in guinea pigs

Answer

A

Electroejaculation produces 0.4-0.8mL of semen; in some electroejaculated boars the ejaculum coagulates in the urethra
Sperm can be harvested from the vasa deferentia and epididymides
IP insemination has been reported with up to 100% incidence of conception when used in conjunction with estrus synchronization; additional methods include injection of sperm directly into uterine horns following laparotomy, endoscope-guided transcervical insemination
AI has been successful up to 16 hr postestrus

Question 33

Q

Superovulation and embryo transfer in guinea pigs

Answer

A

Superovulation induced by IP human menopausal gonadotropin (hMG) and by active immunization against the inhibin α-subunit
Embryo transfer reported rarely in guinea pigs - a method for rederivation purposes has been described where embryos were harvested from donors at 1.5 and 2.5 days post-coitus and transferred to pseudoprenant females mated to vasectomized males 1.5 to 2.5 days earlier - 59 embryos were transferred & two pups were born at 69 & 71 days gestation

Question 34

Q

Helicobacter species in guinea pigs

Answer

A

Naturally occurring Helicobacter spp. in guinea pigs have NOT been reported
Experimental infx with Helicobacter pylori results in severe gastritis that can persist for at least 5 months - model for dz in humans

Question 35

Q

Guinea pigs as respiratory models

Answer

A

Similar pulmonary system to humans
Used to model Legionnaires disease, TB, and other viral and bacterial infx
Extremely sensitive to infection with TB and have been used as sentinels in human hospitals; guinea pig model of TB remains gold standard for testing the potency and standardizing PPD use in humans

Question 36

Q

Bordetella bronchiseptica

Answer

A

Commensal in many species including guinea pigs, rats, rabbits, mice, dogs, swine, cats, turkeys, primates

Short, G(-) rod or coccobacillus, aerobic, motile, non-sporeforming
In vitro growth best at 30 C but slow to poor at 37 C, with minute, circular, pearlescent colonies present at 24 hr and maximum-size colonies at 72 hr; colonies embed in media and surrounded by zone of β-hemolysis
There is serotypic variaton within the species, even within one host species
Variably dissociates in culture (isogenic mutation) - these isolates vary in hemolysin, dermonecrotoxin, proteases, adenylate cyclase, and hemagglutinin production - may affect host specificity, virulence, and disease manifestation

Question 37

Q

Bordetella bronchiseptica - clinical signs in guinea pigs

Answer

A

Subclinical infxs more common
Epizootic respiratory or septicemic disease can progress rapidly (often within 24 hr-72 hr) with high mortality
All ages and both sexes affected
Can see sporadic deaths in enzootically infected colonites
Inappetance, depression, upper respiratory discharge, dyspnea, cyanosis, death
Genital form with a 5-7 day incubation period causes infertility, stillbirth, abortions

Question 38

Q

Bordetella bronchiseptica - transmission in guinea pigs

Answer

A

Potential for transmission from rabbits to guinea pigs is a primary reason these species are not housed together

Transmission: fine particulate aerosol onto the respiratory mucosa, by contaminated fomites, genital contact
Many guinea pigs carry as a commensal resident
Higher morbidity and mortality occur among young and historically in Strain 2 inbred animals

Question 39

Q

Bordetella bronchiseptica - necropsy findings in guinea pigs

Answer

A

Pulmonary consolidation with respiratory exudation, purulent bronchitis, tracheitis, otitis media; consolidated lung areas dark red to red brown to grey
Peribronchiolar and perivascular inflammatory cells contribute to fibrinous or fibrinopurulent bronchopneumonia
Uterine infections may be pyosalpinx and dead embryos/fetuses

Question 40

Q

Bordetella bronchiseptica - pathogenesis in guinea pigs

Answer

A

Organism attaches to ciliated respiratory epithelium - proliferates rapidly and causes ciliary paralysis, an inflammatory response, antiphagocytic activity, and dermonecrosis - presumably through action of an intracellular heat-labile toxin

Question 41

Q

Bordetella bronchiseptica - differentials and diagnosis in guinea pigs

Answer

A

Bronchopneumonia: Stretococcus pneumoniae, S. zooepidemicus, Klebsiella pneumoniae, adenovirus

Definitive diagnosis = swabbing of lumen of bronchi or lower trachea and aerobic culture on sheep blood and MacConkey agar or Smith and Baskerville medium
ELISA and IFA more sensitive then culture for detecting, but various Bordetella antigenic variants should be used on serologic testing

Question 42

Q

Bordetella bronchiseptica - prevention, control, and treatment in guinea pigs

Answer

A

Reduction or elimination of stressors as clinical dz often arises from preexisting subclinical infx
Purchase Bordetella-free stock
Commonly carried by dogs and cats; some research facilities restrict pet ownership
Control by isolating infected animals and those susceptible and treat or remove the clinically ill
Treatment is supportive care and appropriate antibiotics - fluoroquinolones or trimethoprim-sulfonamides

Question 43

Q

Streptococcus equi subsp. zooepidemicus

Answer

A

Lancefield’s group C streptococcus; β-hemolytic, G(+), has antiphagocytic capsule (M-like antigen), produces exotoxin including hyaluronidaze, a protease, and a streptokinase
Subspecies zooepidemicus survives longer off host than the obligate pathogen S. equi

Question 44

Q

S. zooepidemicus - clinical signs in guinea pigs

Answer

A

Pyogenic bacterium assoc w/ suppuration and abscess formation - usually at cervical lymph nodes (cervical lymphadenitis or ‘lumps’)
Torticollis, nasal or ocular discharge, dyspnea, cyanosis, hematuria, hemoglobinuria, cyanotic and swollen mammary glands, abortions, stillbirths, unexpected deaths
Cervical nodes in otherwise health guinea pig is the usual sign
May be inapparent upper respiratory infections

Question 45

Q

S. zooepidemicus - transmission in guinea pigs

Answer

A

Zoonotic potential, although transmission from guinea pigs to humans has not been reported
All ages affected, may be more common in females
Organism inhabits mucosal surfaces
Transmission = via aerosol onto respiratory, oropharyngeal, conjunctival, or female genital epithelium
Disease is of low contagion

Question 46

Q

S. zooepidemicus - necropsy findings in guinea pigs

Answer

A

Most common = Abscessed and encapsulated cervical lymph nodes (node itself may be destroyed) - abscesses contain a nonodorous, yellow-white to red-grey pus
Pneumonia, generalized lymphadenitis, septicemia, focal hepatitis, otitis media, pleuritis, peri- and myocarditis, nephritis, mastitis, metritis, arthritis with necrosis and hemorrhage

Question 47

Q

S. zooepidemicus - differentials and diagnosis in guinea pigs

Answer

A

Cervical lymphadentitis: Streptobacillus moniliformis - carried by wild rats
Upper respiratory lesions & death: S. pneumoniae, B. bronchiseptica, K. pneumoniae, adenovirus
Masses in the neck: lipoma, lymphoma in aged guinea pigs
Diagnosis: clinical and necropsy signs, isolation of β-hemolytic streptococci from abscess margin or heart blood; chains of streptococci can be seen on Gram stain of exudates

Question 48

Q

S. zooepidemicus - prevention, control, treatment in guinea pigs

Answer

A

Prevention: obtain disease free stock, nonabrasive feed (assuming crude fiber may abrade pharyngeal mucosa), trim overgrown or broken teeth, use feeders that do not abrade skin of neck
Control: remove affected animals or replace entire colony
Treatment: surgically remove abscess and capsule; antibiotics safe for use in guinea pigs (fluoroquinolones, trimethoprim-sulfonamides, gentamicin, or chloramphenicol) may be effective

Question 49

Q

Streptococcus pneumoniae

Answer

A

G(+), α-hemolytic, oval to lancet shaped; occurs in culture in paired or chain formation
Two serotypes recovered most often from guinea pigs = 4 and 19F; some of which are assumed to be identical to certain human serovars; one study found guinea pigs may be a reservoir for a serotype 19F that had unique allele combination not found in humans

Question 50

Q

Streptococcus pneumoniae - clinical signs in guinea pigs

Answer

A

Subclinical upper respiratory tract carrier states common in guinea pigs and humans, often over 50% prevalence in some colonies; may then see sporadic epidemics when animals are stressed or malnourished
Clinical signs: high mortality or, in less acute cases, depression, anorexia, nasal and ocular discharge, sneezing and coughing, dyspnea, torticollis, abortions and stillbirths

Question 51

Q

Streptococcus pneumoniae - transmission in guinea pigs

Answer

A

Infections rarely reported or detected in research colonies
Transmission: respiratory aerosol, direct contact with infected animals (including humans), vertically during birth

Question 52

Q

Streptococcus pneumoniae - necropsy findings in guinea pigs

Answer

A

Primarly pyogenic processes: fibrinopurulent pleuritis, pericarditis, peritonitis, suppurative pneumonia, otitis media, endometritis, arthritis
Pulmonary lesion is an acute fibrinopurulent bronchopneumonia with thrombosis of pulmonary vessels

Question 53

Q

Streptococcus pneumoniae - pathogenesis in guinea pigs

Answer

A

-Organism becomes established in upper respiratory tract where it is protected by a polysaccharide capsule and can activate an alternative complement pathway which initiates some of the pathologic changes associated with the infection

Question 54

Q

Streptococcus pneumoniae - differentials and diagnosis in guinea pigs

Answer

A

S. pneumoniae can usually be observed on Gram-stained impression smears of infected tissue, or can be cultured on blood agar incubated under 5-10% CO2
ELISA for streptococci available
Definitive dx requires serotyping among the 83 different capsular polysaccharides; serotyping test = Quellung reaction - utilizes a serum pool product or type-specific antisera - bacterial capsule appears opaque and swollen when the antibody reacts with surface antigens
Differentials: Bordetella sp, other streptococci, Salmonella sp., Klebsiella sp., adenovirus

Question 55

Q

Salmonella enterica

Answer

A

Seen rarely in research guinea pigs
Caused by several serovars of the G(-) bacillus Salmonella enterica, subspecies enterica
Serovars Typhimurium and Enteritidis are encountered most frequently

Question 56

Q

Salmonella enterica - clinical signs in guinea pigs

Answer

A

Peracute or acute infections: only signs may be high morbidity and mortality; mortality may be as high as 50-100% of the population
Epizootic outbreaks occur more often in late pregnant, weanling, aged, and malnourished guinea pigs
In longer term survivors or in sporadic clinical cases: rough hair coats, weakness, conjunctivitis, abortion of small litters, light-colored feces or intermittent diarrhea

Question 57

Q

Salmonella enterica - transmission in guinea pigs

Answer

A

Inapparent carriers shed the organisms intermittently - continued threat to other animals and humans
Transmission: fecal-oral, blood-oral, tissue-oral, via conjunctiva
Shed in the feces of wild rodents or other animals, contaminate food (green veggis, hay) intended for guinea pigs
Guinea pigs HIGHLY SUSCEPTIBLE to Salmonella; incubation period is 5-7 days

Question 58

Q

Salmonella enterica - necropsy findings in guinea pigs

Answer

A

-Gross lesions may not be present; may see hepatomegaly, splenomegaly, small yellow necrotic foci throughout the viscera

Question 59

Q

Salmonella enterica- pathogenesis

Answer

A

Enter body through GI tract or via conjunctiva & elicit histiocytosis, tissue necrosis, abscess formation

Question 60

Q

Salmonella enterica - diagnosis in guinea pigs

Answer

A

Diagnosis: recovery of organism from feces, heart, blood, spleen, or other affected organs through enrichment in a broth such as selenite F or tetrathionate, culture on MackConkey’s or brilliant green agar, and identification of organism
Serotyping identifies the serovar

Question 61

Q

Salmonella enterica - prevention, control, treatment

Answer

A

Aging, other diseases, malnutrition, and environmental stress are predisposing factors
Treatment: NOT recommended; antibitoic use may cause infx to become subclinical and antibiotic resistant
Control: euthanize entire colony, sanitize caging and equipment thoroughly, restock with animal known to be free of Salmonella spp.

Question 62

Q

Clostridium piliforme in guinea pigs

Answer

A

G(-), curved rod; obligate intracellular anaerobe with subterminal spores that persist for years in the environment
Causative agent of Tyzzer’s disease - dz occurs in several species including rodents, rabbits, cats, dogs, horses, some NHP
Rare in guinea pigs
Clin signs in guinea pigs: emaciation, dehydration, lethargy, diarrhea, death
Necrotizing ileitis, typhlitis, and hepatic necrosis in weanling guinea pigs
Necropsy: multifocal necrosis and inflammation of ileum, cecum, colon
Prevention: avoid stressors and maintain good sanitation
Diagnosis: characteristic filamentous bacteria in a Giemsa or Warthin-Starry stained section of enterocytes; organism has not bee directly cultured in vitro

Question 63

Q

Pasteurella multocida in guinea pigs

Answer

A

Rare in well-managed colonies; prevalence of infection unknown
An epizootic reported in literature involved sporadic, unexpected deaths with pulmonary consolidation, fibrinopurulent serositis, conjunctivitis
Diagnosis: culture and identification of characteristic G(-) coccobacillary rods

Question 64

Q

Pseudomonas aeruginosa in guinea pigs

Answer

A

Rare in guinea pigs
Have been associated with pulmonary lesions involving lung consolidation and severe, focal, necrotizing bronchopneumonia; may also cause conjunctivitis and otitis media; one case study found enlarged, inflamed, fibrous prostate gland with local extension of inflammation
Diagnosis: clusters of bacteria surrounded by necrotic debris (‘sulphur granules) in suppurative lesions
Pseudomonas is ubiquitous and may be spread in drinking water or in damp bedding or food

Answer 65

A

Formerly Chlamydia psittaci
G(-), obligate intracellular bacterium
Causes guinea pig inclusion conjunctivitis

Answer 66

A

May be subclinical
Mild reddening of eyelids up to conjunctivitis with serous to purulent exudate, rhinitis, and genital tract infections; abortions and lower respiratory tract infections
Clinical disease is self-limiting with complete recovery in 3-4 weeks

Answer 67

A

Demonstration of intracytoplasmic inclusion bodies in Giemsa- or Macciavello-stained conjunctival epithelial cells
PCR
Differentials for bacterial conjunctivitis: streptococci, coliforms, S. aureus, Pasteurella multocida

Answer 68

A

Self-limiting and typically does not require treatment; Chlamydiophila sp. sensitive to sulfonamide antimicrobials when indicated
Conjunctival and genital infections have served as models for human disease; ZOONOTIC POTENTIAL
Experimental infx of guinea pig genital tract is good model for human chlamydial genital infx - can be sexually transmitted, similar to children, pups born to infected sows are prone to conjunctivitis

Answer 69

A

G(-), nonmotile bacillus; causes rare epizootics in guinea pigs of all ages and both sexes
Predisposing factors: manutrition, magnitude of exposure, unsanitary environments, genetic predisposition
Clinical signs: anorexia, dyspnea, death
Necropsy: seropurulent or serofibrinous lesions in the thoracic and abdominal cavities, mastitis, splenomegaly, thrombosis, coagulative necrosis of the liver, granular degeneration of the renal tubular cells, septicemias; pulmonary lesion is acute bronchopneumonia
Diagnoses: isolate from blood, liver, spleen, peritoneal exudate, cerebrospinal fluid

Answer 70

A

Organism of low contagion carried by wild rats and birds; rarely causes disease in research guinea pigs
Lesions: cervical adenitis with abscessation like S. zooepidemicus, and a pyogranulmatous bronchopneumonia

Answer 71

A

G(-), nonhemolytic, exotoxin- and enzyme-producing, pleomorphic rod
Optimal incubation temperatures are 20-30 C
Virulent strains may grow within macrophages
Infects both sexes and all ages
Clinical signs: 1) Acute, highly fatal septicemia, 2) chronic emaciation, diarrhea, and death within 3-4 weeks, 3) nonfatal lymphadenitis, 4) subclinical carrier state usually following a clinical phase
ZOONOTIC
Because of persistent carrier state, euthanasia is recommended

Answer 72

A

Rare in guinea pigs
G(+) rod; widespread in environment including soil and bedding
Clinical signs: in hairless guinea pigs unilateral or bilateral keratoconjunctivitis and reproductive disorders
Prevention and control involve general precautions
Treatment NOT recommended, instead euthanasia because ZOONOTIC

Answer 73

A

-Mycoplasma caviae, M. pulmonis, etc. and acholeplasmas may occur as latent infections in the reproductive tract, brain, and nasopharynx of guinea pigs

Answer 74

A

Enveloped DNA virus, typical iscosahedral symmetry and 252 capsomers
Genetically distinct from adenoviruses infecting other species; is a separate serotype within the genus Mastadenovirus and has the highest homology with other animal Mastadenoviruses and human subgroups A, C, and F

Answer 75

A

Subclinical infections may be common - prevalence unknown
Clinical disease rare - affected animals usually die without prior signs; may develop dyspnea, tachypnea, dry rales, crepitations, lethargy

Answer 76

A

Infx occurs worldwide and may have a higher prevalence than reported
Clinical disease has no age predilection, is sporadic in endemically affected colonies, and is characterized by low morbidity and high mortality
Transmission: respiratory route

Answer 77

A

Well-demarcated dark red areas of pulmonary consolidation, compensatory emphysema, sometimes catarrhal exudate in air passages
Histology includes necrosis and sloughing of bronchiolar, bronchial, and tracheal epithelial cells - contain large, oval, intranuclear inclusion bodies; surviving epithelium and underlying lamina propria are underlain with a mixed population of inflammatory cells

Answer 78

A

Predisposition factors: stress, immunologically compromised, strain and site of replication of the virus, perhaps anesthetic gas irritation of respiratory tract
Virus enters tracheal and bronchial epithelial cells where replication and cell damage occur - followed by epithelial erosion, parenchymal inflammation, exudation in airways

Answer 79

A

Diagnosis: exclusion of other causes and by histologic and electron microscope examination of air passageway epithelial tissue; no specific serologic test - use of mouse adenovirus strain FL antigen produces excessive false (+) reactions; active disease can be detected by PCR from feces or freshly frozen lung
Differentials for respiratory disease: B. bronchiseptica, Streptococcus spp., K. pneumoniae, cytomegalovirus, herpesvirus, Sendai, parainfluenza

Answer 80

A

Obtain stocks without history of infection, reduce colony stress, observe immune compromised animals
NO treatment

Answer 81

A

Adenoviral vectors used for experimental delivery of aural genes in models of hearing loss; natural infx of study animals did not obviously affect the transfection efficiency of human adenoviral vectors expressing GFP
Inapparent pulmonary infections may become clinical problems when animals are stressed

Answer 82

A

Species specific pathogen

- Detected sporadically in lab guinea pigs

Answer 83

A

Usually subclinical
Strain of host, pregnancy, and immune compromise may predispose to more serious illness
Clinical signs: weight loss, conjunctivitis, lymphadenopathy

Answer 84

A

Presence likely partially dependent on housing conditions
Acute infx followed by chronic, persistent infx
Transmission: exposure to saliva carrying the virus, transplacental transmission throughout gestation - preexisting maternal Ab does NOT prevent transmission to fetuses & C-section does NOT interrupt transmission due to transplacental infection

Answer 85

A

Experimental infection cases more severe signs
Natural disease: karyomegaly of salivary gland epithelium (submaxillary gland) to severe interstitial pneumonia, splenomegaly, lymphadenopathy, fetal meningitis
Congenital neurological abnormalities and deafness can occur

Answer 86

A

Viremia within 2 days of exposure - results in widespread, systemic dissemination - salivary gland, hepatic, and renal cells are primary sites of replication
Many more organs become infected by 10 days
By 12-14 days viremia ceases and virus is more difficult to find in visceral organs
By 3 wks postexposure, inclusion bodies are present in salivary glands - chronic, persistent phase contnues in the salivary gland and thymus in adult and in the salivary gland and spleen of fetuses

Answer 87

A

Microscopic identification of large, eosinophilc, usually intranuclear inclusion bodies in the ductal epithelial cells of submaxillary salivary gland - inclusions form at 5 days-3weeks postexposure
Inclusion bodies may also be seen in brain, lung, kidney, spleen, pancreas, thymus, liver
Indirect fluorescent antibody techniques and histopathology are methods of diagnosis

Answer 88

A

Prevention and control: select guinea pig stocks known free of GPCMV, screen new arrivals, selective necropsy, serology
NO treatment

Answer 89

A

-Natural disease may be unapparent (unless detected by serology or necropsy) but could interfere with studies involving tissues harboring virus

Answer 90

A

RNA virus; family Picornaviridae; some antigenic cross -reaction with the GDVII strain of Theilovirus

Genetic variants among host guinea pigs may affect predisposition to infx and clinical signs
Appears more common in pet store than lab guinea pigs, but still a possible diagnosis in guinea pigs with lameness

Answer 91

A

Clinical signs are rare; within colonies clinical disease is sporadic if it exists at all
Clinical signs: depression, lameness in one or more limbs, flaccid paralysis, weight loss, death over 2 weeks

Answer 92

A

Transmission route not proven, but fecal-oral common among Picornaviridae
In mice and rats the endemic epizootic cycle of Theilovirus is by fecal-oral transmission

Answer 93

A

Findings are histologic and include meningomyeloencephalitis, perineuronal inflammation, neuronal degeneration, necrosis of anterior horn cells of the lumbar spinal cord
In mice the virus replicates presumably in the grey matter of the cortex and progresses into the white matter and upper motor neuron pathways

Answer 94

A

-ELISA using the Theilovirus strain GDVII mouse virus antigen combined with histo findings of CNS and lumbar spinal cord lesions

Answer 95

A

One paper recommended Vitamin C for prevention, control, and treatment, given that Vitamin C contributes to adrenocorticosteroid production and presumably, protection of myelin
Infection may complicated investigations of CNS in guinea pigs

Answer 96

A

RNA arenavirus
Causes lymphocytic choriomeningitis in mice, dogs, primates (including humans) and rarely guinea pigs when contracted iatrogenically via inocluation with contaminated biologicals or possibly through inhalation, ingestion, or through the skin following exposure to biting insects or infected wild mice
Clinical signs: CNS dysfunction, hindlimb paralysis
Lesions: lymphcytic infiltration in meninges, choroid plexus, ependyma, liver, lungs
Diagnosis: IFA - liver is best site for detection; ELISA to detect antibodies
ZOONOTIC
Has many systemic effects in guinea pigs that would interfere with research projects

Answer 97

A

Rare and usually clinically inapparent
Poxviruses, guinea pig retroviruses, parainflunza viruses, murine pneumonia virus, mammalian orthoreovirus (reovirus 3), simian virus 5, herpesvirus, Sendai virus

Answer 98

A

Protozoan; phylum Apicomplexa; moderately pathogenic
Coccidian with ellipsoidal oocytes without a micropyle
-Infx associated with high populations of Balantidium coli may occur in the proximal colon, with B. coli as a secondary agent producing clinical disease
-Stress is also significant predisposing factor
-Can be commensal without clinical signs

Answer 99

A

Ingestion of sporulated oocysts

Oocysts in feces require 2-11 days outside the host to develop to an infective stage; factors impacting maturation include heat, humidity, oxygen
Prepatent period = 10 or more days

Answer 100

A

In severely infected weanlings: lethargy, anorexia, watery to pasty feces lasting 4-7 days

Oocysts may not occur in feces until 10 days post-infx, so may see soiled hair coat, diarrhea, and even death before oocysts detected in feces
In survivors constipation may follow diarrhea

Answer 101

A

Edema, hyperemia, hemorrhage, white or yellow plaques in the thickened proximal colon and adjacent cecal wall
Intestinal contents watery and often contain blood
Histo: colonic epithelial cell hyperplasia, intracellular coccidian forms, enterocyte sloughing, edema and congestion of lamina propria
Ingested, sporulated cysts invade the mucosal crypts of Liekberkühn in proximal colon and, during schizogony, damage the epithelium

Answer 102

A

Oocysts on fecal float, mucosal scraping, stained tissue sections
Diff Dx: pantothenic acid or Vitamin C deficiency, cryptosporidiosis, bacterial enteropathies, coronavirus

Answer 103

A

Good sanitation and husbandry, reduction of stress, provision of fresh, appropriate feed
Sulfonamides with known anti-Eimeria activity and provision of Vitamin C

Answer 104

A

Coccidium of guinea pigs that has a prolonged phase of endogenous replicaton

Answer 105

A

Subclinical infx may be common
Clin signs most often seen in young animals (under 300g or up to 16 wks old); may be exacerbated by concomitant E. coli enterotoxemia
Weight loss (most common sign), anorexia, potbellied appearance, rectal prolapse, uncommonly diarrhea and death

Answer 106

A

Transmission: fecal oral; infxs are patent for 2 weeks and cleared by 3-4 wks postingestion in young adults and 1-2 wks in adults
Necropsy: diffuse enteritis from duodenum to cecum; intestinal hyperemia, edema, atrophy or necrosis of villus tips, lymphocyte infiltration, hyperplasia of crypt epithelium

Answer 107

A

Cryptosporidial bodies intracellularly in brush border epithelium near villus tips and most numerous in anterior ileum
Bodies are basophilic, round to oval, 1-4 µm diameter
Detect organisms in mucosal scrapings examined on phase contrast microscopy or on stained tissue sections

Answer 108

A

Acquired when guinea pigs ingest feces from infected cats
Infx rare and primarily subclinical
Clin signs: vulvar bleeding, abortion; encephalitis
Asexual stages of organism, which may survive up to 5 years, are distributed in most tissues - tachyzoites in virtually every organ, bradyzoites in brain, heart, skeletal muscle where they may be detected histologically
Moderate immune reponses occur in the host & can identify antibodies to T. gondii
Infx of the uterus, placenta, and fetus may be subclinical or cause a blood-filled uterus, fetal deaths, and abortion

Answer 109

A

Usually nonpathogenic; ciliated protozoan possessing a micro- and macronucleus
Transmission: fecal oral
Inhabits cecum and colon
Its trophozoites may be an opportunistic pathogen in bacterial enteropathies, following mucosal damage, or with E. caviae present in the intestinal wall
Identified histologically in intestinal wall (postmortem invasion also possible) and in intestinal contents and feces

Answer 110

A

Sporocysts ingested with urine and excyst in gut - sporozoites pass via circulation to renal tubule epithelium, glomerular capillaries, spleen, lungs - maturing schizonts contain 8-12 merozoites, which on host cell rupture pass to the proximal tubular epithelium where second generation schizogony occurs
Large schizonts, containing up to 100 merozoites, can cause significant enlargement of infected epithelial cells
Gametogonous and sporogonous forms occur in the epithelium of the loop of Henle, and schizogonous stages occur in the epithelial cells of the proximal convoluted tubules and in the glomeruli
Merozoits in the loop of Henle produce zygotes, which undergo sporogony
Histo: protozoal forms and inflammatory cell infiltrates

Answer 111

A

Clinical signs and gross necropsy findings are rare except in heavy infestations = renal surface irregular with gray mottling d/t proliferation of interstitial fibroblasts, which may cause some renal impairment
-Prevention: good sanitation, removal of susceptible animals from exposure to the urine of infected animals

Answer 112

A

Endolimax caviae, Entamoeba caviae, Giardia duodenalis (enteritis), Leishmania enrietti (cutaneous nodules and ulcers), Tritrichomonas caviae, Sarcocystis caviae, Trypanosoma cruzi (chronic myocarditis)

Prevention and control are strict sanitation and periodic screening for the organism
Sulfonamides are NOT effective treatment

Answer 113

A

Cecal worm & only common helminth of guinea pigs

Inhabits but does not penetrate the cecal and colonic mucosa
Considered non-pathogenic; single report that causes bronchoalveolar eosinophilia
Worms mature in 45 days; ellipsoidal egg to egg life cycle is 51-66 days; ova are transmitted in feces and become infective in 3-9 days after shedding
Prevention/control: removing fresh feces and maintaining good sanitation
Adult male worms: 11-22mm long, females 16-28mm long

Answer 114

A

Guinea pig is a paratenic (substitute intermediate) host -Ingest embryonated ascarid eggs present in raccoon feces - larvae migrate via small intestine, other organs, and the bloodstream throughout the host, often including the CNS (cerebral larval migrans), where they may cause damage and inflammation

Clin signs: torticollis, ataxia, anorexia, opisthotonos, stupor, hyperexcitability
Prevention: exclusion of raccoon feces & removal of ova from environment
ZOONOTIC

Answer 115

A

Pentastome ‘tongue worm’
Live in nasopharyngeal region of mammals
Nymphs reported in guinea pigs in 1970s

Answer 116

A

Reported in guinea pigs in South America

-Anoplocephala sp. = tapeworms

Answer 117

A

Trematodes; rarely infect guinea pigs - exposed to infectious metacercariae shed from snails
Metacercariae move to a vegatation substrate, lose their tails, and encyst on leafy vegetables that guinea pigs may eat
Adult flukes mature in host liver and shed eggs into the small intestine and feces
Eggs require a snail intermediate host to mature
Consequent biliary and hepatic damage may cause anorexia, debilitation, death; infected guinea pigs may become emaciated, anemic, possibly paretic due to aberrant parasite migration
Primary lesions in LIVER

Answer 118

A

listrophorid fur mite: Chirodiscoides caviae, Demodex caviae, Mycoptes musculinus, sarcoptids Trixacarus caviae and Sarcoptes scabiei and Notoedres muris
-Only Chirodiscoides and Trixacarus reported commonly, and usually in pet guinea pigs

Answer 119

A

Usually subclinical, although a dense population of elongated mites moving on hair shafts is apparent
Heaviest infestations on POSTERIOR TRUNK
May cause pruritis, self-trauma, alopecia, and dermatitis
Heavy infestation: self-mutilation, weight loss, lethargy, in response to pruritis run and bump into objects, convulse, die; stress of disease may cause infertility and abortion
Adult males often couple in noncopulatory position with females

Answer 120

A

Burrowing, sarcoptidiform mite
Asymptomatic or intensely pruritic generalized dermatitis - presence and severity of lesions related to variations in host strain susceptibility and to self-traumatization
Secondary infx may contribute to severity and distribution of signs
Lesions most common on TRUNK, INNER THIGHS, NECK, SHOULDERS; patchy or generalized; affected skin dry to oily with alopecia and marked hyperkeratosis
Heavy infestation: self-mutilation, weight loss, lethargy, in response to pruritis run and bump into objects, convulse, die; stress of disease may cause infertility and abortion

Answer 121

A

Confined to the stratum corneum and consist of epidermal hyperplasia (or thinning) and orthokeratotic an parakeratotic hyperkeratosis

Folds in stratum corneum contain mites and eggs; adult mites found in short tunnels
Spongiosis and leukocytic/monocytic infiltration occur in dermis
CBC may show heterophilia, eosinophilia, basophilia

Answer 122

A

Reported rarely

- May localize to CONJUNCTIVAE, FOREQUARTERS - alopecia and crust and papule formation

Answer 123

A

May cause pruritic dermatitis

Answer 124

A

Both widely distributed in North America and Europe & probably occur worldwide
Transmission: direct contact, via pelage, cage debris, fomites, bedding
Trixacarus has 10-14 day life cycle
Sows pass mites to weanlings, naive adults; cool carcasses pass mite to warm living guinea pigs

Answer 125

A

No abnormal necropsy findings, except mite and ova on hair shafts
Attach to hair shafts and do not burrow in skin

Answer 126

A

Severe cutaneous lesions, associated loss of body fat, pale liver, subcutaneous signs of secondary bacterial infx (e.g., staphylococcal pyoderma)
Burrow into stratum corneum; pruritic response apparently due to initial allergic response to mite antigen and consequent inflammation

Answer 127

A

Ovoid and elongated with a triangular anterior; paired male and female nymphs also characteristic
Lice, other mites

Answer 128

A

Indicated by clinical signs, especially pruritis & mites on skin scraping or biopsy
Shorter than S. scabiei (200-450 µm); skin and hair may have to be dissolved in 10% potassium hydroxide and then filtered to retain the mites
Mites often on lumbar region and lateral aspects of rear legs
Pediculosis, dermatophytosis, barbering, sarcoptic and notoedric mange

Answer 129

A

More likely to occur when maintained in unsanitary conditions with inadequate veterinary care
Trixacarus lesions seem to occur in some strains more than others and in stressed animals
Control is by repeated treatment of all animals & thorough cleaning and sanitization of environment; larvae and nymphs in environment may establish new infestations

Answer 130

A

Application at 2 week interval of a diluted (water and propylene glycol) spray of ivermection, selamectin, or pyrethrin

Answer 131

A

Ivermection 0.2-0.5 mg/kg SC or orally 3x at 7-10 day intervals
Treated guinea pigs may be shaved or bathed in medicated shampoo to loosen and remove cutaneous debris
Infestation may persist despite ivermectin tx

Answer 132

A

T. caviae can cause transient, pruritic papulovesicular lesions in humans
G pigs with untreated, severe acariasis are not useful in research, especially if study involves cutaneous responses

Answer 133

A

Suborder Mallophaga (chewing or bitiing lice) - abrade the skin and ingest fluids

Gliricola porcelli = slender louse
Gyropus ovalis = ovoid
Trimenopan hispidum & Trimenopan jenningsi

Answer 134

A

1.0-1.5 mm adult lice attached to hair shafts
Sometimes asymptomatic
Heavy infestations: erythema, scratching, alopecia, scabbing around the ears and nape of neck
Transmisson: direct contact with infected host or via contaminated bedding
Gliricola porcelli seen more often than Gyropus ovalis; infx rare in laboratory guinea pigs
On death of host, lice migrate away from cooling body along hair shafts

Answer 135

A

Diagnosis: viewing adult or immature lice with hand lens
Gliricola = narrow head and body (0.3 mm wide)
Gyropus = ovoid and broader (0.5 mm wide)
Prevention: obtaining clean stock, maintaining good sanitation
Control: isolation, treatment with dust, dip, or ivermectin, medicated shampoos and shaving, and cleaning the environment

Answer 136

A

Ctenocephalides felis (cats [and dog] flea) & Nosophyllus fasciatus (northern rat flea) reported to be able to infest guinea pigs
Occurrence in laboratory guinea pigs rare
Clin signs: pruritis, skin crusts, anemia
C. felis is intermediate host for cestode Dipylidium caninum, & N. fasciatus for hymenolepid tapeworms
Some tick genera (Dermacentor) could possibly affect guinea pigs

Answer 137

A

Primarily caused by Trichophyton mentagrophytes (zoophilic, filamentous dermatophyte; aerobic, ubiquitous, saprophytic, keratinophilic fungus)
Also reported in guinea pigs: Arthroderma benhamiae (teleomorph derived from mating strains of T. mentagrophytes complex), Microsporum spp., Scopulariopsis brevicaulis
Fungi live in soil, on other animals, in straw, wood, food

Answer 138

A

Lesions begin on the muzzle and head, hair, nails
Lesions occur most often in young guinea pigs or guinea pigs genetically predisposed, stressed, pregnant, malnourished, diseased, or living in unsanitary conditions
Subclinical infx possible
Lesions in ‘hairless’ guinea pigs resemble humans lesions more closely
Irregularly shaped areas of alopecia, scaling, crusing, reddening may extend to back and sides but rarely to limbs
May see associated vesicles, pustules, abscesses d/t secondary bacterial infx
Lesions sometimes pruritic, often self-limiting, can last up to 30 or more days
Severely affected young may die

Answer 139

A

Dermatophytoses occur in many warm-blooded species, especially younger animals in close contact; primates, dogs, cats, horses, swine, ruminants, rodents, and birds
Transmission: direct contact with spores either on animal itself or fomites like bedding
ZOONOTIC
Incubation period of 9-12 days

Answer 140

A

Changes in skin confined to superficial keratin layers and structures of the skin and hair follicles
UV light may cause M. CANIS to fluoresce yellow green, but false positive and false negative possible

Answer 141

A

-Fungi solubilize keratin with proteases - produces scale accumulation on and around the lesion and loosening and weakening of the hair shafts - dermatophyte penetrates the stratum corneum or invades hair follicles - growth continues down the hair shaft to the keratogenous one until the growth inwards equals the outward growth rate

Answer 142

A

Hair loss: protein and caloric deficiency, chewing and barbering, bacterial dermatopathies (Staph and Strep), cystic ovary effects, acariasis, continuous breeding
Diagnosis: observation of irregularly shaped, nonpruritic, flaky-skin lesions on the head; recovery of organism from hair and epithelial debris on Sabourand’s dextrose agar or dermatophyte test media; observation of species-characteristic morphologic features and macroconidia in Microsporum or microconidia in Trichophyton
Epithelial cells and debris best obtained by vigourous brushing with a toothbrush
Most reliable diagnostic method: fungal culture; growth usually occurs within 10 days

Answer 143

A

Selection of nonsusceptible animals, good husbandry including appropriate feed and clean environment, alleviation of stress
-Dark, moist environments support survival and replication of dermatophytes

Answer 144

A

Improved sanitation and husbandry, reduction of stressors, removal of infected animals and environmental control

Infected hairs MUST be removed from environment
Disease is usually self-limiting bu full resolution may take months

Answer 145

A

Griseofulvin 25 mg/kg PO Q24hr for 2 weeks past resolution of clinical signs; oral griseofulvin absorbed poorly in the intestine unless given with a high fat meal & is teratogenic
Topical griseofulvin in dimethyl sulfoxide solution for 5-7 days
1% tolnaftate topically
Butenafine topically for 10 days
Thiabendazole, ketoconazoe (hair clipped), itraconazole, terbinafine hydrochloride

Answer 146

A

Single-cell, intracellular microsporidian (and true fungus) affecting canids, rabbits, rats, NHPs, guinea pigs, and other species

In guinea pigs no know clinical signs & few if any necropsy findings
True prevalence in guinea pigs unknown due to subclinical infx and infrequent serologic screening

Answer 147

A

Infective spores disseminated in urine and then ingested or inhaled; transplacental transmission suspected in several species
Guinea pigs relatively resistant to infx (source of spores may be rabbit urine)

Answer 148

A

Microscopic lesions occur primarily in the brain and kidney
Infected brain: may have randomly distributed necrotic foci, microgranulomas, perivascular lymphoplasmacytic cuffs, lymphocytic meningitis
Renal lesions: may or may not occur; multiple, 2-4mm grey to white granulomatous foci seen as indentations or plaques just beneath the renal capsule (could confuse with nephrosis in older guinea pigs)
Interstitial, mononuclear nephritis
Lesions may also occur in liver and lungs

Answer 149

A

Ingested organism undergoes merogony and then sporogony in cytoplasm of endothelial cells, peritoneal macrophages, renal tubular epithelium, and oligodendrocytes
Spores are found intracellularly and, after cell rupture, extracellularly

Answer 150

A

Characteristic histo lesions, birefringence of organisms under polarized light, staining with periodic acid-Schiff or Goodpasture-carbol fuchsin stain, indirect ELISA, fluorescent immunoassay, Western blot
Serologic screening is preferred method
Diff dx: toxoplasmosis - distinguish by Gram stain

Answer 151

A

Purchase and breed seronegative animals, house away from seropositive rabbits, regular program of serologic screening and removal of seropositive animals, strict sanitation

Answer 152

A

No treatment reported for guinea pigs, but fenbendazole and albendazole have been used with variable results in rabbits

Answer 153

A

Spontaneous infections have occurred

- Emaciation, lameness, gastroenteritis, lymphadenopathy

Answer 154

A

-Spontaneous infections have occurred - was associated with occlusive capillary embolism and tissue infarction

Answer 155

A

Cryptococcus neoformans, Coccidioides immitis, Blastomyces dermatitidis, Aspergillus fumigatus
A normal stomach inhabitant, Torulopsis pintolopesii, may cause enteritis
Scopulariopsis sp., Aspergillus sp., Penicillium sp. may be part of fungal microbiota of guinea pig haircoat

Answer 156

A

Increased susceptibility to infectious dz, esp streptococcal infx and enteropathies
Signs of conjunctivitis or upper respiratory dz should always suggest a marginal Vitamin C deficiency and treatment should include Vitamin C supplementation
In group housing, larger guinea pigs can bully smaller or younger guinea pigs, resulting in nutritional deficiencies

Answer 157

A

Also known as scorbutus or scurvy
Occurs in a small number of species - notably humans, some other primates, guinea pigs, bats - that lack the genetic code to produce the hepatic enzyme L-gulonolactone oxidase - this enzyme converts L-gulonolactone into the isomers L-ascorbate (AH) & L-dehydroascorbic acid (DHA)
Probable primary roles of vitamin C are acting as a cofactor in hydroxylation and amidation reactions by transferring elections to enzymes that provide reducing equivalents (i.e., protons) and scavenging both intracellular and extracellular superoxide radicals and singlet oxygen, whose activity results in tissue damage
Lack of vitamin C results in defective cross-linking of collagen fibrils characterized by defective wound healing and fragile capillaries

Answer 158

A

May be subclinical, accompanied by overt signs of infectious dz (e.g., diarrhea, upper resp infx), or a primary vitamin C deficiency
Marginal deficiencies particularly impt in laboratory guinea pigs d/t increased susceptbility to infectious disease
Signs of secondary (usually bacterial) infx include unexpected death, diarrhea, weight loss, swollen and reddened orbital margins, dehydration, dyspnea
Most obvious clinical signs of Vit C deficiency = fragility of small blood vessels - rupture causing bruises, reluctance to move, screaming when restrained, swollen joints

Answer 159

A

Hemorrhage in the subperiosteum, adrenal cortex, skeletal muscle, joints (especially stifles and costochondral junctions), and intestine; gut may be atonic and hyperemic
Histology: changes related in many cases to absence of hydroxyproline and hydroxylysine elements in connective tissue; epiphyseal growth centers of long bones are deranged w/ greatly reduced osteoid formation, degenerating and deranged chondrocytes, decreased bony trabeculae in the marrow cavity, reduced osteoclastic and increased osteoblastic activity, multiple microfractures; myofilaments fragmented and mitochondria swollen; hemorrhage in many tissues

Answer 160

A

With defects in amino acid metabolism (including tyrosine and phenylalanine), fibroblasts and osteoprogenitor cells produce defective intracellular architecture and the products dentin, collagen, and osteoid
Junctional defects and cytoplasmic disruption occur between endothelial cells; in muscle, liver, connective tissue cells; in pericapillary fibrous tissue; and in arterial intimae
Subendothelial cholesterol deposition increases, as does lipid peroxidation of cardiac muscle
Iron absorption in the gut and steroidgenesis in the adrenal gland decrease - may be related to increased macrophage cytotoxicity
Macrophage migration and heterophil phagocytosis are decreased
Cholesterol catabolism slowed, reducing bile acid production and consequently fat-soluble vitamin assimilation, and cholesterol accumulates in the liver

Answer 161

A

Weakness, pain, and death in young guinea pigs: infectious disease, osteoarthritis, heat stress, toxemias
History of inappropriate feed, decreased prothrombin time, and serum Vitamin C level below 0.55 mg/dL (normal around 2.01 mg/dL) indicate hypovitaminosis C

Answer 162

A

Foods providing at least 6 mg Vitamin C per day are adequate
Vitamin C level of 250-500 mg/L in drinking water also provides adequate levels if the water is replenished daily
Vitamin C ‘half-life’ in glass bottles is ~24 hr
In food stored at 72 F, vitamin C has only 33% of original activity at 30 days postmilling and 14% at 90 days; most commercial guinea pig chows now use a stabilized vitamin C guaranteeing a shelf life of at least 180 days
Guinea pigs on alcohol consumption studies have an increased need for vitamin C
Lesions develop in 7-10 days with NO vitamin C & in ~3 weeks with marginally deficient diets
Improper compounding and storage, autoclaving, and feeding food formulated for other species are common errors
Pregnant guinea pigs may require up to 30 mg/kg daily. but the levels given commonly (10 mg/kg daily) probably exceed requirements

Answer 163

A

Parenteral or oral administration of Vitamin C daily at levels up to 30 mg/kg
-Recovery occurs rapidly over 1-2 weeks

Answer 164

A

Research with scorbutic guinea pigs is compromised in several ways due to profound and extensive changes, including decreased disease resistance

Answer 165

A

1) Preeclampsia, eclamptogenic toxemia, or the circulatory form
- Arises from abnormal vascular changes that lead to ischemia of the uteroplacental unit
2) Fasting ketosis, of the metabolic-nutritional form
- Progresses from hypoglycemia and hyperlipidemia

Answer 166

A

Occurs in late pregnancy (last 2 weeks) and immediately postpartum
Occurs more often in obese, multiparous, stressed sows
Affected animals may die without clinical signs or may be dehydrated, depressed, anorexic, underweight
Proteinuria, acidic urine (pH 5-6; normal pH 8), ketonuria, elevated serum creatinine, increased or decreased plasma triglyceride levels
UNLIKE preeclampsia in humans (who also have labyrinthine hemomonochorionic placentation), guinea pigs exhibit hypertension variably and edema rarely
Guinea pig placentation = hemomonochorial with maternal blood circulating around a single trophoblastic layer over fetal capillaries

Answer 167

A

Occurs in last trimester (after 45 days), but most often in the last 1-2 weeks
Weakness, depression, dehydration, may die following a 1 to 3 day fast
Acidic urine, ketonuria, variable plasma glucose levels, hyperlipidemia, elevated alkaline phosphatase and ornithine carbamyl transferase serum levels

Answer 168

A

Many mammals, including humans, NHPs, rabbits, dogs, ruminants, and guinea pigs, exhibit similar conditions in late pregnancy or early lactation but characteristics vary

Answer 169

A

Preeclamptic animals usually exhibit more severe changes
Preeclamptic/circulatory form: uterus, placenta and adrenal cortices show petechial and ecchymotic hemorrhage and focal necrosis; placental attachment sites, which detach easily, are also affected; fetuses are dead and decomposing; enlarged, yellow-tan liver with necrotic foci, subcapsular hemorrhage of kidneys,
Fasting ketosis/metabolic-nutritional form: gastric ulcers; fatty infiltration of liver, kidney, adrenal glands, and vessel walls; uterus and placentae have petechial and ecchymotic hemorrhages but NOT as severe as preeclampsia form; livers develop fewer necrotic areas, if any

Answer 170

A

Preeclampsia has been induced experimentally in guinea pigs by constricting the abdominal aorta or severing or ligating arteries supplying the pregnant uterus
Pathogenesis behind uteroplacental ischemia poorly defined; proposed course in guinea pigs involves thrombocytopenia, thromoplastin release, alterations in the renin-angiotensin aldosterone system, vasoconstriction, deposition of fibrin, and disseminated intravascular coagulation
Initial causes of preeclampsia IN HUMANS multifactorial and involve reduced placental perfusion d/t insufficient valvular dilation (uterine vessels in late pregnancy only 40% of normal size) and defective trophoblastic replacement of vascular endothelium accompanied by fibrinoid accumulation in and around vessels - proceeds to generalized endothelial dysfunction through a maternal response to trophoblast antigens or vasoconstriction and activation of a clotting cascade initiated by oxygen-free radicals, lipid peroxides, and proteases; triglyceride levels increase within endothelial cells; apparently a genetic predisposition

Answer 171

A

Depression and death in late pregnancy suggest pregnancy ketosis
Acidic urine, absence of acute septicemic disease (e.g., salmoellosis, bordetellosis), and poor response to treatment support this diagnosis

Answer 172

A

Pregnant guinea pigs should be fed nutritious and balanced diet continuously without changes
Guinea pig breeding stock with no history of obesity or deaths during pregnancy should be selected and housed in a reduced stress environment

Answer 173

A

Rare success with treatment
Administration of electrolyte fluids, glucose, calcium gluconate, coticosteroids, and various combintions of fruits and veggies provide no certain disease reversal

Answer 174

A

Any research project involving breeding or obese guinea pigs, particularly in a stressful environment, can have many sudden animal deaths

Answer 175

A

Specific cause of uroliths unknown, but probably involves genetic factors, diets with calcium, magnesium, and phosphorus imbalances, cystitis, nephritis, or urinary tract environmental factors
Decreased urine flow, elevated urine pH, and the uroliths themselves may predispose to cystitis
Proteinaceous urethral plugs fund occasionally in older male guinea pigs probably originate from seminal vesicle content
Bacteria assoc w/ cystitis in guinea pigs include E. coli, Staphylococcus sp., Streptococcus pyogenes
Cystitis often accompanies urolithiasis, lower urinary tract infection, immunosuppression, estrogenic stimulation, diabetes; may be mild to severe, and acute, subacute ulcerative, or chronic

Answer 176

A

Urolithiasis usualy subclinical and occurs in older sows
When urinary blockage or infx occurs, can see weakness, weight loss, pain on palpation, vocalization, straining, anuria or dysuria, anorexia, a small thickened bladder, hematuria
Signs may progress over several weeks; untreated animals may die
Urine sediment may contain crystals, erythrocytes, and epithelial cells

Answer 177

A

Occurs most often in aged (over 30 months) females

- Urinary tract blockage by proteinaceous plugs occurs in aged males

Answer 178

A

Unilateral or bilateral uroliths in the bladder, kidneys, ureters, urethra, vagina, or passed in the urine; concretions of up to 2 cm in diameter may occur in the bladder or urethra
With concurrent cystitis, bladder may be distended with urine and have thickened, hemorrhagic walls with calculi adherent to the mucosa
Proteinaceous plugs occur in the male urethra or bladder
Hydroureter, hydrourethra, hydronephrosis d/t continued occlusion of urinary output with fluid containing white to brown mineral sediment or solid masses

Answer 179

A

In order of frequency: calcium carbonate, calcium phosphate, magnesium ammonium phosphate hexohydrate, calcium oxalate
-Individual uroliths may contain a mixture of these crystal types

Answer 180

A

Progression of ionic saturation, supersaturation, nucleation, crystallization, and crystal growth in urolith formation
In urinary bladder, protein may provide a nucleus for crystal formation

Answer 181

A

Diagnosis: based on clinical signs of cystitis, detection of uroliths on radiographs or U/S
Diff dx: infection, neoplasia, trauma to genitalia

Answer 182

A

Selection of animals known free of urolithiasis, provision of appropriate food and ample water, immediate clinical care of guinea pigs with cystitis
Alfalfa hay and some of the dark leafy veggies are high in calcium
Grass hay and other sources of Vitamin C are preferable in order to avoid stone formation

Answer 183

A

-Provision of fluids and appropriate systemic antibiotics based on C&S (fluoroquinolones), proper diet, if indicated cystoscopic or surgical removal of uroliths

Answer 184

A

Occur occasionally when feeding is restricted or neglected, or due to malocclusion
Usual consequences are reproductive impairment, both infertility and death of low weight (<50g) neonates, hair loss
Pregnancy and lactation may cause a negative energy balance and subsequent hair loss

Answer 185

A

Arginine, Methionine, Tryptophan

-Guinea pigs can produce niacin from tryptophan - tryptophan-deficient diets can produce cataract formation

Answer 186

A

Weight loss, ulcerative dermatitis, hair loss, visceral abnormalities

Answer 187

A

Rare in herbivores

- Poor growth, keratitis, squamous metaplasia, crust eyelids and pinnae, loss of organization in tooth forming elements

Answer 188

A

Can be caused by giving a multivitamin supplement
-Degeneration of cartilaginous epiphyseal plates in long bones, abnormal bone repair, teratogenic effects during organogenesis at 14-20 days

Answer 189

A

Effects of vitamin K in guinea pigs not well defined

- May synthesize sufficient vitamin K (and most B vitamins) to prevent overt abnormalities

Answer 190

A

Experimental deficiency produces wider epiphyseal cartilage plates, enamel hypoplasia, weight loss
Rickets is NOT a spontaneous disease in guines pigs
Hypervitaminosis D caused by diet misformulation reported to cause anorexia, weight loss, death

Answer 191

A

CNS disorders, including tremors and imbalance

- In B-deficient scorbutic animals, increased muscle weakness occurs

Answer 192

A

-Corneal vascularization, skin lesions, myocardial hemorrhage, decreased growth and failure to thrive

Answer 193

A

-In young guinea pigs causes anemia and diarrhea

Answer 194

A

-In young animals causes depression in phagocytic activity of myeloid cells

Answer 195

A

-In young animals causes general signs as well as profuse salivations and terminal convulsions

Answer 196

A

-Anorexia, weight loss, and - if deficient in weeks 9-10 of gestation, causes abortion and sometimes death of dams

Answer 197

A

-Poor growth and fatty liver

Answer 198

A

Major signs: Hindlimb weakness through myasthenia or muscular dystrophy, reduced reproductive performance, paralysis, death
Associated signs: coagulative necrosis of muscle, testicular degeneration, degenerative changes in seminiferous tubules, reduction of spermatozoa and spermatids. elevated creatine phosphokinase
Mucular dystrophy precedes testicular degeneration
Lethargy and conjunctivitis seen in debilitated animals
Iatrogenic deficiency of selenium and Vitamin C reported to cause skeletal muscle cell death

Answer 199

A

Excess increases the requirement for magnesium, which contributes to metastatic mineralization
Guinea pigs use cation exchange and phosphate anions for removing excess hydrogen ions rather than removing protons by excretion of ammonium ions
Calcium turnover is rapid in guinea pigs
Phosphate ions are critical component of metastatic mineralization; magnesium supplementation essential to offset hyperphosphatemia; high phosphate levels lower plasma pH
Potassium will counteract adverse effects of excess phosphate by providing an exchange cation to remove excess hydrogen ions

Answer 200

A

-Reproductive disorders, pancreatic hypoplasia

Answer 201

A

-Slow growth and myelination failure

Answer 202

A

-Poor weight gain, hair loss, hindlimb weakness

Answer 203

A

May occur in guinea pigs over 1 year of age
Usually subclinical
Occurs on skeletal and cardiac muscle fibers; renal collecting tubules, interstitium, convoluted tubules, Bowman’s capsule; in other soft tissue esp around elbows and ribs; in lungs, trachea, aorta, liver, stomach, uterus, sclera
Gross lesions: irregular, grey patches on tissue surfaces that grate when cut with a blade
Histo changes: notable in hindlimb muscles; mononuclear cell infiltration, mineralization, fibrosis
Clinical signs: if present, poor growth, hair loss, muscle stiffness, bone deformities, nephrosis, death
Probable causes: diets with calcium, phosphate, magnesium, and Vitamin D imbalances
Mineral deposits are usually calcium, phosphates, or carbonates combined with other minerals
May have local low tissue pH
Prevention: don’t feed diets for other species to guinea pigs

Answer 204

A

Uncommon in guinea pigs, except for certain inbred colonies or male Abyssinian-Hartley colonies with a genetic predisposition or a yet unidentified infectious agent
Clinical signs evident at 3-6 months of age, affect both sexes; polyuria, weight loss, infertility, cataract formation, variable glycemia, hyperlipemia, glycosuria, (over 100-2000 mg/dl), rare ketouria
Resembles Type I diabetes mellitus in humans = islet hyperplasia, degranulation of beta cells, thickening of basement membranes of peripheral capillaries, fatty infiltration of exocrine cells, glomerulosclerosis
Spontaneous remissions accelerated by feeding hay and leafy greens occur; injected insulin not needed to maintain animals but insulin or an oral hypoglycemia agent has decreased glucosuria

Answer 205

A

Common, especially if feeders or waterers or food (odor, taste, density, texture, form) or water (flavor) has changed
Guinea pigs are neophobic & by 4 days old develop food preferences & then may not recognize as food other diets (powders, veggies, supplements, etc.)
Other factors: postsurgical stress, ketosis, malocclusion, drafts, illness, water deprivation
Treatment: provide preferred or sweetened foods, changing feeder or waterer, treating existing disease, reducing crowding, reducing obesity

Answer 206

A

Sensitive to sudden or extreme environmental changes; such changes are predisposing factors for respiratory disease and stress-precipitated illnesses
Guinea pigs’ ancestors lived at high, cooler altitudes = heat stressed easily, even when in direct sunlight at temps as low as 70 F.
Clinical signs: shallow, rapid respiration; weakness, hyperthermia, coma, death
Treatment: cool water baths, corticosteroids, parenteral fluids

Answer 207

A

Pulling and ingestion (trichotillomania) of cage mates’ hair occurs primarily in group-housed females; may be precipitated by stressors or need to displace another guinea pig from food/water source
Chewing of hair (trichophagia) may occur without wounds; self-barbering occurs caudal to the anterior shoulders; dominance-associated or agonistic trichophagia by conspecifics usually on rump, back, and around eyes and ears
Barbering and skin damage most often occur among status seeking adult males with or without a sow present, when parents groom young, or weanlings chew sow’s hair
Self-barbering may be ameliorated by feeding hay and dark, leafy greens
Biting may cause alopecia, scratches, lacerations, deep wounds; perineal wounds contaminated with bedding or food can become infected, extend to prepuce, cause urine retention & bleeding, pain during mating, reduced reproductive performance; some boars scoot around cage and push bedding into prepuce causing similar signs
Prevention: reduce environmental stressors, early weaning, separation of boars to single housing or provision of shelters, perhaps hay feeding
Treatment: cleaning of wound and placing in clean cage; few topical antimicrobials are effective and, if ingested, may precipitate enterotoxemia

Answer 208

A

Aggressive behavior

- Severe damage can results in infections and partial or complete loss of pinnae

Answer 209

A

Limbs caught and injured in wire cage walls or flooring
Bone fractures from improper handling or dropping
Diaphragmatic hernia
Broken or luxated vertebral column
Fracture of liver capsule
Broken teeth

Answer 210

A

Guinea pigs injected SC with Freud’s complete adjuvant may develop pulmonary granulomas
Lesions are similar to perivascular lymphoid nodules or focal pneumonia caused by other conditions

Answer 211

A

Frequently bred sows show hair thinning - d/t high metabolic demands or pregnancy and probable genetic and metabolic factors
Hair loss in breeding groups may be d/t trichophagia
Hair regrows when breeding stops or social dynamic changes
Alopecia may also occur in young animals at weaning, when the hair coat changes character, and when guinea pigs are on low-protein or low-calorie diets

Answer 212

A

Common in guinea pigs
May be d/t uterine inertia, pregnancy toxemia, fetuses too large to pass through pelvic canal, os coxae failed to separate - despite relaxin release, to the 2.5-3 cm needed to allow fetuses to pass
Failure or fibrocartilaginous pelvic joint to separate occurs most frequently in sows bred for the first time over 7 months of age b/c symphysis usually fuses and becomes resistant to relaxin
Clinical signs: still narrow symphysis near 73 days gestation, straining, depression, vaginal discharge
Prevention: first breeding before 7 months of age, prevent obesity and fasting while pregnant, remove animals with known family history or dystocia
Young guinea pigs involved in dystocia experience hypoxia, which is often fatal
Treatment: digital removal of fetus; calcium, glucose, 1-3 mg/kg oxytocin (ONLY if pubic symphysis confirmed open); C-section

Answer 213

A

Occurs on volar surfaces of one or more feet and presents with enlarged, firm, ulcerated wounds
Chronic, ulcerative lesions may have Staphylococcus involvement
Can be associated with amyloid accumulation in the liver, adrenals, spleen, pancreatic islets
Prevention and treatment: provide smooth wire or solid-bottom flooring with bedding, good sanitation, reduction of obesity; severe cases antibiotic treatment, softening with lotion, surgical debriding
S. aureus can cause pneumonia, mastitis, conjunctivitis, cheilitis, osteoarthritis; has been assoc w/ exfoliative dermatitis with alopecia, erythema, scabs, epidermal cracks
Staph enter skin through abrasions
Histology: parakeratosis with minimal inflammation
Pododermatitis rapidly progresses to osteomyelitis is not treated
Amputation NOT an option due to body weight distribution

Answer 214

A

Enteropathies and deaths in guinea pigs occurring w/in 1-5 days of administration of certain antibiotics assumed to result from 1) antibiotic-induced suppression of resident microflora, perhaps Bacteroides; 2) loss of cecal colonization resistance; 3) colonization, proliferation, and toxin production by transiting or resident commensals, usually one or more strains of C. difficile
E. coli is NOT a normal intestinal inhabitant in guinea pigs; may proliferate in antibiotic-caused dysbiosis
Antibiotics most often implicated: AMINOPENICILLINS, CEPHALOSPORINS, CLINDAMYCIN, STREPTOMYCIN, LINCOMYCIN (penicillin dose as low as 2000 U or ampicillin over 6 mg/kg Q8hr for 8 days known to cause death)
Clinical signs: vary with drug dose and strain of opportunisitic pathogen; rapidly progressive lethargy, rough hair coat, diarrhea, death
Necropsy: hemorrhagic typhlitis, cecum distended with bloody liquid feces; severe inflammatory rxn in the lamina propria and microulceration of the mucosa with inflammatory cell infiltration
Treatment: supportive fluids, highly palatable food, heat

Answer 215

A

Common, fecal-borne, anaerobic, G(+), commensal whose large subterminal spores persist in the environment
Some strains produce protein exotoxins (cytotoxins) A & B - bind to epithelial cell membrane receptors
Toxin B is more cytotoxic but requires Toxin A (enterotoxin) to access mucosal cells
Toxin A causes fluid secretion, mucosal damage, inflammation - results in cell death
Cause of antibiotic-associated typhlocolitis
Drug prophylaxis NOT recommended: treatment of choice in humans, metronidazole, may exacerbate toxicosis in guinea pigs
Treatment: supportive fluids, highly palatable food, heat

Answer 216

A

Use cautiously in immature guinea pigs
Report showed single SC dose of 350 mg/kg quinolone nalidixic acid in 6 week old guinea pigs cause severe degeneration of middle-zone chondrocytes

Answer 217

A

Otoconial (inner ear cell) loss in the striola region of both utricle and saccule in adult, mixed-sex guinea pigs following seven IP injections of 250 mg/kg streptomycin
Recovery often occurred in 8-10 weeks

Answer 218

A

-Interfere with calcium uptake into otoconia (inner ear cells)

Answer 219

A

Most common in animals over 3 years of age
Most common type are those of hemolymphopoietic system, followed by respiratory system, integument, reproductive tract, mammary gland, hemopoietic system, cardiovascular system, endocrine glands

Answer 220

A

Elodontic and hypsodontic teeth
Maocclusion may occur because of shortness of maxilla, abnormally narrow mandibular separation (anaesognathism), nutritional deficiency, broken or deviated teeth d/t trauma or periodontal infx
Root abscesses may extend into mandible or maxillary sinus & cause exophthalmos
Premolars and molars involved most often, but incisors can also be maloccluded
Clinical Signs: weight loss, inappetance, drooling (‘slobbers’), oral laceration and bleeding, gaping mouth, death
Necropsy: periodontal dz and overgrown teeth, often with sharp edges and POINTS ON LABIAL SIDE OF MAXILLARY & LINGUAL SIDE OF ROSTRAL MANDIBULAR MANDIBULAR CHEEK TEETH; elongated coronal surfaces may arch, inhibit tongue movement, and force open the mouth
Diagnosis: clinical signs and oral exam
Differentials: drooling can also be d/t folic acid deficiency, chronic fluorosis, heat stress, hypovitaminosis C, dental abscesses
Treatment: trim overgrown teeth to 2-3 mm above the gingiva & file sharp points (dental bur or rongeurs; only in anesthetized animals); remove infected teeth, drain abscess, antibiotics
Tooth extraction via bucotomy is complicated b/c of difficulty in access and relative paucity of alveolar bone in mandible
INHERITED, esp in 2/N and 13/N inbred strains = don’t breed

Answer 221

A

-Probably secondary to uremia, ketosis, excessive stress, Citrobacter infection

Answer 222

A

Reported in 6 breeder guinea pigs aged up to 26 months

Found dead or with dyspnea, cyanosis, tachycardia, distended stomachs containing fluid and gas rotated 180 degrees on mesenteric axis; diaphragm displaced anteriorly
Cause of volvulus not apparent

Answer 223

A

All ages; Strain 13 more commonly involved
May be due to manipulation, antibiotic use, corticosteroid injection, fasting, torsion, advanced pregnancy
May be no clinical signs except death

Answer 224

A

Caused by wood shavings, hair, inspissated digesta

Answer 225

A

Colonic stricture, dilation, cecal torsion, cecal and rectal impactions, rectal prolapse, circumanal sebaceous accumulations

Answer 226

A

Contusion, focal coagulative necrosis (maybe d/t agonal hypoxia), idiopathic cholangiofibrosis

Answer 227

A

Cardiac rhabdomyoma
Pale, pink foci or streaks with indistinct margins in the myocardium, usually the left ventricle
Relatively common in guinea pigs; similar lesions occur in dogs, swine, humans
Streaks = glycogen accumulation in myofibers or Purkinje fibers d/t congenital abnormality of glycogen metabolism
Diagnosis: alcohol-fixed specimens stained with periodic acid-Schiff stain
No apparent cardiac impairment caused by the lesions

Answer 228

A

May begin at early age and continue as common occurrence in older animals
Primary cause for nodules unknown; may be antigenic stimulation and are less common in SPF guinea pigs
Perivascular lymphoid nodules, consisting of normal lymphocytes, may be in the adventitia of the pulmonary arteries and veins
In older guinea pigs, aggregations reach 0.5mm diameter & visible grossly as pinpoint-sized subpleural foci

Answer 229

A

Rarely reported

- Thickened pulmonary artery musculature, osseous metaplasia in alveolar septa, foreign body pneumonia

Answer 230

A

Incidental findings in aged guinea pigs
Characterized by weakness, anemia, dilute urine, increased BUN and creatinine
Autoimmune, infectious, and vascular diseases may contribute
Necropsy: pitted subcapsular renal surface with pale streaks extending into the cortex and even medulla; segmental to diffuse interstitial fibrosis causes kidney to have irregular surface
Histo: most glomeruli remain normal, but immune complex deposition occurs in basement membrane
Chronic renal failure may predispose to cochlear dysfunction, especially in the hair cells

Answer 231

A

Normal guinea pig: ovaries lie caudo-lateral to kidneys, 6-8mm long & 4-5mm diameter; rete ovarii are derived from the mesonephric tubules & occur in the hilus of the ovary
Cysts of the rete ovarii are common in sows 1.5-5 yrs of age
Cause of cysts unknown; both androgens and estrogens may be involved in the pathogenesis
Incidence may range from 76-90% in older sows
Clinical signs: anorexia, depression, abdominal distension, bilateral symmetric hair loss over flanks and rump, reproductive failure
Diagnosis: careful clinical exam (avoid rupturing cyst), radiography, U/S imaging using a 6.0 or 10.0 MHz mechanical sector transducer
Cysts are up to 7 cm or more in diameter, singular or multilocular, unilateral or bilateral (R more often than L), may be assoc w/ leiomyomas of the uterine body or horn, cystic endometrial hyperplasia, or endometritis; larger cysts may cause pressure atrophy in adjacent ovarian tissue
Treatment: surgical removal

Answer 232

A

Report noted spontaneous, progressive osteoarthritis in stifle and other joints of male Dunkin Hartley guinea pigs
Noted as early as 3 months of age; became severe by 22 months
Changes in cartilage included increased levels of proteoglycans and decreased collagen
Histo: osteophytse, calcification of collateral ligaments of the joint, degeneration of weight-bearing, articular surfaces
Hypovitaminosis C, obesity, joint injury may contribute to joint degeneration
Mechanical load and stiffness are significant pathogenic mechanisms

Answer 233

A

-Scorbutus lesions, osteodystrophy, nutritional myopathy, consequences of injections and bites

Answer 234

A

Paurangiotic retina - retinal blood vessels are minute and restricted to the direct neighbourhood of the optic disc - and NO tapetum
Pupil dilation by using 1% tropicamide drops or, in pigmented animals, one drop each of 1% atropine and 10% phenylephrine 3-4x within 15 min
Exam best accomplished using a 20-diopter (D) or 30-D indirect condensing lens
Fluorescein dye use, exfoliative conjunctival exam, and culture are diagnostic methods

Answer 235

A

Blepharitis with epithelial flaking, crusting, alopecia, swelling, reddening of lids = ‘dull eyes’
Usually seen in guinea pigs with marginal hypovitaminosis C, with subclinical infx - usually of upper respiratory tract, or with malocclusion or renal disease

Answer 236

A

-Caused by chlamydophilae, streptococci, staphylococci, Pasteurella spp., physical or chemical irritants

Answer 237

A

-Upper molar root abscess extending into maxillary sinus and orbit, orbital trauma, foreign bodies, sialocele, lacrimal gland cysts or inflammation, neoplasia (lymphosarcoma)

Answer 238

A

-May be a portion of a lacrimal gland, or a yellow subconjunctival fat deposit

Answer 239

A

May result from feeding a diet low in L-tryptophan (under 0.1%). diabetes
Heritable cataracts have been reported in strain 13/N d/t a single, autosomal, gene deletion of 34 residues that produces a novel zeta-crystallin lens protein; homozygous = lenses completely opaque; heterozygous = lenses have a well-demarcated opaque nucleus with a normal cortex

Answer 240

A

Dermatophytosis of the lids, common bacterial infections, herpesvirus conjunctivitis, listerial keratoconjunctivitis, ophthalmitis, ocular dermoid, microphthalmia, corneal dryness, optotoxicity from toxin ingestion, ulceration, osseous metaplasia, osseous choristoma of the ciliary body

Answer 241

A

-Topical or systemic antibiotics; known safe and effective = fluoroquinolones, chloramphenicol, trimethoprim-sulfonamide

Answer 242

A

Hyperthyroidism, hyperparathyoidism, and hyperadrenocorticism have been reported, but incidence of these is low

Answer 243

A

Deposition of amyloid A (AA) in the kidney, liver, spleen, adrenal glands
Associated with aging or chronic inflammatory conditions, such as staphylococcal pododermatitis and osteoarthritis, or with multiple casein injections
Amyloid = extracellular deposition of polymerized serum protein subunits that have a role in inflammation
Condition is slowly progressive, begins in the renal mesangium, and extends into subendothelial portions of capillary basement membranes

Answer 244

A

Guinea pigs that eat grasses contamined with hyphal masses (sclerotia) of Claviceps purpura - which produces alkaloids ergotamine and ergometrine - may develop dry gangrene of feet
Toxins damage the capillary epithelium and lead to thrombosis and necrosis

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Chapter 6. Biology and Diseases of Guinea Pigs Flashcards

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