Chapter 4. Biology and Diseases of Rats Flashcards
What is the scientific classification of the rat?
Rattus norvegicus
Order Rodentia
Family Muridae
Genus Rattus - contains at least 56 species
Norway rat
Rattus norvegicus
What is the maxillary recess (sinus) in the rat?
Located between the maxillary bone and the lateral lamina of the ethmoid bone. Contains the lateral nasal gland (Steno’s gland)
Steno’s gland (lateral nasal gland)
Has morphologic similarities to a serous salivary gland. Secretes a watery product discharged at the rostral end of the nasal turbinate. This secretion may act to regulate the viscosity of the mucus layer overlying the nasal epithelium.
How many lung lobes does the rat have?
Five. Left lung is single lobed. Right lung has cranial, middle, accessory, and caudal lobes.
What is unique about the pulmonary vein in rats?
Contains cardiac striated muscle fibers within its wall that an contiguous with those in the heart.
How is bronchoconstriction controlled in the rat?
By vagal tone. The rat does not have an adrenergic nerve supply in the bronchial musculature.
What are the accessory sex glands in male rats?
Paired bulbourethral glands (Cowper’s glands) at the base of the penis - open into the dorsal surface of the urethral flexure.
Within the abdominal cavity and surrounding the bladder are large vesicular glands (seminal vesicles) and the prostate gland.
How many lobes does the prostate gland in a male rat have?
Three. Dorsocranial (coagulation gland), ventral, and dorsolateral.
What type of uterus do rats have?
Bicornate uterus, although the uterine horns appear fused distally there are two distinct ossa uteri and cervices.
Describe the kidneys of rats.
Unipapillate, like other rodents. The right kidney is more cranial than the left (cranial edge at L1 and caudal edge at level of L3)
Why is the rat a common model for investigating nephron transport?
Can investigate with an in vivo micropuncture system, because of the presence of superficial nephrons in the renal cortex.
Describe unique features of the rat brain.
Large olfactory bulbs, a lissencephalic (smooth) cerebrum, two parafloccular lobes of the cerebellum - lie in deep sockets of the periotic capsule of the skull.
The hypophysis (pituitary gland) lies beneath the optic chiasma and is attached to the base of the brain by a thn hollow stalk - the infundibulum.
Rats lack a foramen of Magendie (links fourth ventricle to cisterna magna in humans).
Where do the spinal cord and filum terminale in rats end?
Spinal cord ends at the fourth lumbar vetebra. Filum terminale (extension of pia mate, functions to suspend cord in CSF) ends at the level of the tail beyond the third caudal nerves.
Where is the recommended site for cardiocentesis in rats?
Along left thoracic wall between third and fifth ribs - heart is exposed to the thoracic wall in this area.
Describe the blood supply to the atria in rats.
Unlike in higher mammals, the blood supply to the atria in rats is largely extracoronary from branches of the internal mammary and subclavian arteries.
Black rat
Rattus rattus
R. rattus preceded R. norvegicus in migration from Asia to Europe and the Americas by several hundred years.
R. rattus reached Europe in the 12th century, Americas in 16th century.
R. norvegicus emerged in the 18th century in Europe, 19th century in Western Hemisphere.
Why has the Norway rat largely displaced the the black rat globally?
Norway’s rat’s larger size and aggressiveness
What is the history of the albino R. norvegicus rat?
Domesticated and used in Europe and America in the 1800s as prey for a sport (rat baiting) where terrier dogs would hunt rats in a pit. Because of the large number of rats needed, wild rats were purpose-bred and albinos were selected out by hobbyists.
What were some of the early experimental uses of rats?
Nutritional research with fasting studies as far back as at least 1828.
Used by Savory in 1863 in protein studies.
J.M. Philipeaux reported on effects of adrenalectomy in albino rats in 1856.
Used only sporadically in Europe and North America for research until ~1890.
What was the Wistar Institute?
Henry H. Donaldson & Milton Greenman at the Wistar Institute in the early 20th Century were pivotal in the development of the rat for reasearch use. Did much to produce and define early stocks of lab rats.
List some of the research uses for rats.
A standard species for toxicological, teratological, and carcinogenesis testing by the pharmaceutical industry and governmental regulatory agencies.
Use in behavioral, neurological, nutritional, and endocrinology.
ACI
Inbred strain used for: congenital genitourinary anomalies, prostatic adenocarcinomas
BB/Wor
Inbred strain used for: Juvenile insulin-dependent diabetes mellitus
BN (Brown Norway)
Inbred strain used for: Inducible, transplantable, myeloid leukemia, hydronephrosis, bladder carcinoma
BUF (Buffalo)
Inbred strain used for: Spontaneous autoimmune thyroiditis, host for transplantable Morris hepatoma
COP (Copenhagen)
Inbred strain used for: Prostate adenocarcinoma
F-344 (Fischer 344)
Inbred rat model for National Toxicology Program’s Carcinogen Bioassay Program and the National Institute of Aging
LEW (Lewis)
Inbred strain used for: Multiple sclerosis, various experimentally induced autoimmune diseases
LOU/C
Inbred strain used for: Myeloma, production of IgG autoantibody
SHR (spontaneous hypertensive rat)
Inbred strain used for: Hypertension, cardiovascular research
WF (Wistar-Furth)
Inbred strain used for: Mononuclear cell leukemia
Zucker
Inbred strain used for: Obesity
Brattleboro
Mutant strain used for: Diabetes insipidus (autosomal recessive)
Gunn
Mutant strain used for: Jaundice, kernicterus (autosomal recessive)
Nude
Mutant strain used for: T cell deficient (autosomal recessive)
Obese SHR
Mutant strain used for: Type 4 hyperlipoproteinemia (autosomal recessive)
Recommended room temperature for rats
70-76 deg F
Recommended room humidity for rats.
30-70%
Recommended room air changes per hour for rats.
10-15 air changes/hour are sufficient to compensate for heat load and the generation of NH3 and CO2 from animals
Recommended light intensity at cage level for rats.
130-325 lux is recommended to prevent retinopathy.
Rats are particularly susceptible to phototoxic retinopathy.
Management precautions such as not having exposed cages on the top shelves of tall racks should also be considered.
Why should rats be housed on solid-bottomed floors?
Unless there is an experimental need, rats should be housed on solid-bottomed instead of wire-bottomed cages to help prevent pododermatitis and injuries that are frequently associated with wire floors.
What are the most frequently used materials for solid-bottom rat cages?
Polycarbonate and polypropylene.
Polycarbonate is often preferred because it may be autoclaved repeatedly without damage and because its translucency allows for observation of animals.
Sold bottom cages should typically be sanitized 1-2 times per week; a less frequent cycle may be appropriate if cage density is very low, there are perinatal considerations, or ventilated cages are used.
Describe the tail lengths of different rat species.
Norway rat = tail ~85% the length of the body.
Black rat = tail is distinctly longer than the body
What is the hair growth cycle in young rats?
Resting period = 17 days, growing period = 17 days, repeats.
How many teats do rats have?
Usually 12; 3 pectoral pairs & 3 abdominal pairs.
Rank smallest to largest: Sprague Dawley, Wistar, Fischer 344
Outbred Sprague Dawley bigger than outbred Wistar; and inbred Fischer 344 smaller than both outbreds
Describe anatomic features of the rat eye.
Eyes are exophthalmic = increased risk of injury from trauma or during anesthesia.
Eyelids well developed & only corneas are visible.
Cornea moistened by secretions from lacrimal and Harderian glands.
Harderian gland is located medially to the orbit.
Orbital venous plexus has slightly different anatomy than the orbital sinus in the mouse, but can still be used for blood collection.
Rats do NOT have robust color vision.
What is chromodacryorrhea?
Production of Harderian gland products containing porphyrin.
The porphyrins will fluoresce; it has been suggested that the Harderian gland may have a function as a modulator of light-mediated responses
Describe the color vision of rats.
Dichromatic color vision with two types of cones; one cone type response to UV light with response centered around 359nm. The longer wavelength cone and rod have peak sensitivity around 505-509nm. (Why dim red lighting around ~625nm is used; however even dim red light can affect their photoperiodic physiology.)
What is the vomeronasal organ?
The vomeronasal organ (VNO) - essential to normal rodent reproductive behavior
i. When male rodents engage in anogential investigation of females prior to mounting, vaginal chemosignals are maneuvered to the roof of the mouth, then “pumped” through the nasopalatine duct into the opening of the VNO.
ii. Other signals may enter via the external nares (nostrils) and may be pulled down to the VNO from the floor of the nares.
iii. Neural information moves from the VNO to the accessory olfactory bulbs via the vomeronasal nerve bundle; thus, information originally obtained from the activation of VNO receptors is processed by the accessory olfactory bulbs.
iv. Information from the olfactory receptors is processed separately in the main olfactory bulbs
What is the hearing range of rats?
250 Hz to nearly 80 kHz; most sensitive hearing is in range of 8-32 kHz.
What is the ultrasonic range of hearing and vocalization in rats?
22-80 kHz.
Important to minimize ultrasonic noise in animal facilities (some things known to cause ultrasonic noise: some types of occupancy sensors, some types of energy-efficient high-frequency electronic ballasts that are used to drive fluorescent lamps).
What are vibrissae?
Extremely important sensory organ for touch in rats - whiskers.
What bones make up the skull of the rat?
Paired nasal, premaxillary, maxillary, zygoma, palatine, lacrimal, frontal, parietal, squamosal, periotic capsule, tympanic bulla, and mandible; six auditory ossicles; four turbinates; single vomer, ethmoid, basisphenoid, presphenoid, occipital ,interparietal, and hyoid bones.
What is the vertebral column formula for rats?
7 cervical, 13 thoracic, 6 lumbar, 4 sacral, 27-30 caudal
Describe the structure of the ribs in rats.
Ribs consist of ventral calcified and dorsal ossified segments without true costal cartilages.
How many bones make up the carpus and the tarsus in the rat?
Carpus = 9, Tarsus = 8
Describe the pelvic and hind limb bone structure of the rat.
Pelvis is formed by ossa coxae, which articulate with the first two sacral vertebrae. Hind limb bones = femur, tibia, and fibula that articulates with the tibia proximally but is fused distally.
What is the dental formula of the rat?
2(I 1/1, C 0/0, PM 0/0, M 3/3)
Name the salivary glands of the rat.
The salivary glands are paired and include the parotid, submandibular, and the smaller sublingual glands.
The parotid glands are serous, have 3-4 lobes located ventrolaterally from the caudal border of the mandible to the clavicle.
The submandibular glands are mixed, situated ventrally between the caudal border of the mandible and the thoracic inlet.
The sublingual glands are mucous, at the rostral pole of the submandibular glands
Where is brown adipose tissue located in the rat?
Also called multilocular adipose tissue or the hibernating gland; located on the ventral and lateral portions of the neck and can be confused with salivary glands.
Describe the anatomic structure of the rat stomach.
Divided into two parts - forestomach (cardiac portion) is nonglandular & corpus (pyloric portion) is glandular. The limiting ridge (margo plicatus) separates the two portions, with the esophagus entering at the lesser curvature through a fold in the ridge.
Why can’t rodents vomit?
Do not possess many of the anatomical and neurological components required for a functional vomiting reflex
Describe the anatomy of the rat intestine.
Small intestine = duodenum (8 cm), jejunum (80 cm), ileum (3 cm); comma shaped cecum with thin walls and a prominent mass of lymphoid tissue in its apical portion; colon = ascending colon with prominent oblique mucosal ridges, and the transverse and descending portions with longitudinal mucosa folds.
How many lobes does the liver have in the rat?
4: median - which has a deep fissure for the hepatic ligament; right lateral - partially divided; left - large; caudate - small and surrouds the esophagus.
Rats do NOT have a gallbladder - the bile ducts from each lobe form the common bile duct, which enters the duodenum about 25mm from the pyloric sphincter.
Describe the pancreas of the rat.
Very diffuse and lobulated organ; darker color and firm consistency compared to surrounding fat; numerous excretory ducts fuse into two to eight large ducts that empty into the common bile duct.
What are the three classifications of diets for rats?
Natural-ingredient, purified, chemically defined.
What is the most commonly used type of diet in most research applications?
Natural-ingredient; The nutrient composition of this type of diet varies from batch to batch because of various factors (e.g., relative costs of grains, weather conditions, harvesting and storage conditions, and concentrations of contaminants).
What type of diet is used for toxicological and other types of GLP studies?
Certified natural-ingredient diets. These are assayed and certified to not exceed maximum concentrations of a set list of contaminants (pesticides, heavy metals, mycotoxins, and estrogens).
Why are nutrient concentrations of purified diets less variable than natural ingredient diets?
Purified diets are made of defined ingredients, each composed of a single nutrient or nutrient class (e.g., casein, sugar, starch, vegetable oil, cellulose).
Downside = more expensive, often less palatable.
Name a frequently used purified rat diet.
AIN-76.
Describe chemically defined diets.
Formulated with very basically defined ingredients (e.g., specified amino acids, sugars, triglycerides, and essential fatty acids); often expensive and tend to be less palatable.
Name a dietary variable that can have significant impacts on both male and female rats.
Phytoestrogens.
List health benefits found to be associated with limit feeding (vs. ad lib feeding) in rats.
Increased longevity, reduction in incidence of neoplasia (e.g., lung, mammary, pancreatic islet, pituitary), reduction in chronic inflammation and fibrosis of the heart, reduction in acute inflammation of the prostate, reduction in radiculoneuropathy and acinal hyperplasia of the mammary gland.
What four pathways have been implicated to be involved in the caloric restriction effects on rodent health?
Insulin-like growth factor (IGF-1)/insulin signaling pathway, sirtuin pathway, adenosine-monophosphate (AMP)-activated protein kinase (AMPK) pathway, and the target of rapamycin (TOR) pathway.
What is the vaginal plate?
In the rat, the vagina is closed at birth by compact epithelium known as the vaginal plate. It begins to degenerate and cornify at 20-35 days of age and the canal is completely open between 40-80 days of age.
What clinical conditions can be seen with persistence of the vaginal plate?
Fully imperforate vagina or a vaginal septum. These conditions may be associated with infertility or metritis.
What anatomic changes can be used as signals of impending puberty in female and male rats?
Female = vaginal opening. Male = Balano-preputial separation
When does puberty occur in rats?
2-3 months old (significant variation between strains)
True/False. In rats, estrus occurs before full reproductive competency is reached.
True.
How long is the estrus cycle in rats?
4-5 days. Occurs year-round, including post-partum. ~1 day in each of the four stages. Cycles of up to 6 days are not uncommon.
How can the uterus appear in the proestrus in the rat?
Can appear “ballooned” with fluid; do not mistake for hydrometra.
When does ovulation occur in the rat?
~8-11 hrs after onset of estrus, usually between midnight and 2 am.
How long do ova remain viable in the rat?
10-12 hr.
When do testes descend in male rats?
~15 days of age.
When are sperm first produced and when does puberty occur in male rats?
Sperm production = 45-46 days of age. Puberty = 62-65 days. On histology, young rat testes show more degenerative germ cells prior to 75 days of age than afterward, indicative of poor efficiency of spermatogenesis at early ages in rats.
When during the dark cycle does coitus most commonly occur in rats?
Later in the dark cycle (rather than earlier)
What is ejaculatory latency?
Multiple intromissions (5-15), each lasting 0.3-0.6 sec and with two to nine pelvic thrusts precede the first ejaculation, which lasts about 1 sec. This first series of intromissions is called the ejaculatory latency and lasts about 10 min followed by a refractory period. Multiple series of intromissions and ejaculation, usu ~7, occur with increasing refractory periods between successive episodes.
When does implantation of the blastocyst occur in rats?
Between 5 to 7 days after fertilization the blastocyst implants in the endometrium; represents a process that takes 12-24 h to complete.
What is the gestation period in rats?
21-23 days, but can be as short as 19.
What are indications of estrus in the rat?
Ear quivering when back or head are stroked, lordosis when pelvic area stimulated, swelling of vulva, vaginal wall appears dry due to cornification of the vaginal epithelium
What percent of vaginal epithelial cells are cornified during estrus in the rat?
25-100%
Describe role of an impedence meter in detection of estrus in rats.
Changes in vaginal fluids and cytology also change the electrical impedance of the vagina during estrus. An impedence meter can be used to measure this with a probe inserted into the vagina. However, the impedence meter gives less info than cytology regarding the specific phase of estrus and the physical stimulation of the probe may induce pseudopregnancy.
When can pregnancy be detected in the rat?
Palpation = 10 days, esp accurate after 12 days.
Transabdominal ultrasound = 9-10 days
Doppler = fetal heartbeat can be detected by 12 days
Mammary gland and nipple development = 14 days
What effect does constant light have on estrous in rats?
Persistent estrus and cystic ovarian follicles without the formation of corpora lutea. Chronic exposure to even low intensity light during the dark cycle can result in early vaginal opening and ovarian atrophy.
What effect does caloric restriction have on estrous in rats?
15-30% restriction from ad lib can cause cessation of estrous cycles and delayed sexual maturation.
What effect can high ambient temperatures have on male rat fertility?
Can result in male infertility by causing irreversible degeneration of the seminiferous epithelium. Damage may occur in rats as young as 4 days and at temps as low as 26.6 C.
How long is average parturition in the rat?
1.5-3 hours.
Which litter in rats is usually the largest?
The second litter.
After 9 months of age, litter size if further decreased and the pregnancy rate declines after 12 months of age.
What is pregnancy wastage?
Loss of festuses. Occurs as a function of age. Primarily due to preimplantation and early posimplantation mortality. Can also be caused by maternal stressors (ex: earthquake, strenuous exercise; shipping?)
Maternal behavior in virgin rats enhanced at 19-20 months of age vs. 3-4 months of age.
Describe a newborn rat.
Altricial and nidicolous; hairless and blind; poorly developed limbs, short tails, and closed ear canals.
Inverse relationship between fetal weight and litter size.
What factors influence birth weight in rats?
Litter size, maternal age (pups of dams mated at 105 d weighed more than pup of dams mated at 35 or 70 d).
Describe the development of hearing in rats.
Cochlea and organ of Corti are immature at birth but develop to approx. adult morphology by weaning. First able to hear around 9 days old, but able to vocalize from birth.
Describe tooth eruption in rats.
Incisors erupt 6-8 days of age, molar 1 day 16, molar 2 day 18, molar 3 day 32-34.
Describe development of sight in rats.
Retina poorly developed at birth, equivalent to 4-5 month human fetus. Eyelids open at 14-17 days of age. Retina fully matures by 30-40 days of age. Final components of the angle of the anterior chamber not fully formed until 60 days of age.
Describe development of hair in rats.
Some hairs may be present on trunk at birth - usually associated with touch domes, indicating they are guard hairs. Pups fully haired at 7-10 days of age.
How is maternal antibody transferred to rat pups?
Transferred passively across the yolk sac in utero. CAn also be transferred across the intestinal mucosa from colostrum and milk to suckling rat. Transfer occurs at low rates shortly after birth, reaches maximal rates at day 14, and ceases by 21 days when gut closure said to be complete.
Describe the process for sex determination in preblastocyst rat embryos.
Males embryos cease development when exposed to antibody to the HY antigen, an resume development only after antibody washed off. 80% of embryos that developed into embryos in presence of the HY antibody produce female pups.
How can PCR determine sex of rat embryonic tissues?
PCR primers for sequences of the male sex determining region Y (SRY).
When does the micturition reflex mature in rat pups?
15 days of age.
Describe some way to sychronize estrus in female rats.
1) Administration 40 micrograms of luteinizing hormone releasing hormone agonist (LHRH) to mature female rats & can be bred 4 days later.
2) Administration of 40 mg methoxyprogesterone in the drinking water for 6 days in 200 ml ethanol/liter water, prepared fresh daily), followed by IM injection with 1 IU pregnant mare’s serum
Describe recommended steps for sperm collection in rats.
Semen from electroejaculation rapidly coagulates due to contributions of seminal vesicles and coagulating glands.
For AI or cryopreservation, instead collect sperm during terminal dissection. Sperm from the proximal portion (head) of the cauda epididymis are reported to have greater fertility than from middle or caudal portions.
What agents are used for hormonal superovulation in rats?
- Pregnant mare serum gonadotropin (PMSG) followed by human chorionic gonadotropin (HCG); similar to mice
- Follicle stimulating hormone (FSH) with or without luteinizing hormone (LH)
What technique can be used to rescue or maintain strains that do not have motile spermatozoa?
Intracytoplasmic sperm injection (ICSF) - IVF technique of microinseminaton of individual oocytes. By adding exogenous DNA, can also be used as a method for producing transgenic rats.
Which rat strains are generally more docile?
Sprague-Dawley background (CD or SC stocks) and Lewis generally more docile than Brown Norway or F-344 rats.
What is the typical frequency of rat alarm calls?
22 kHz (can be produced during handling)
Why do rat pups vocalize in the ultrasonic range?
To signal to their mothers before their ears are sufficiently developed for them to be capable of hearing.
When do female rats typically have a a shorter tail flick response?
Female rats have shorter tail flick response times in the middle of the dark period, as well as during estrus and metestrus.
What housing choices have rats shown preference for?
Solid flooring, bedding consisting of large particles of aspen wood chips, and nest boxes.
Streptococcal pulmonary disease - causative agent
Streptococcus pneumoniae (alpha-hemolytic) Numerous serotypes - infection usu assoc. w/ more pathogenic serotypes 2, 3, 8, 16, 19.
Transmission of S. pneumoniae?
Natural host is humans. Transmission primarily via aerosol, fomites may play minor role.
Clinical signs of S. pneumoniae?
Usually asymptomatic and colonizes rat’s nasopharynx. Rat is used as a model of human infection, but immunosupression, neutropenia, or other special techniques usu needed to induce clinical disease. Clin dz = suppurative inflammation spreads to lungs, bronchopneumonia; sometimes fibrinosuppurative pleuritis; may become bacteremic and develop fibrinous inflammation of other serous surfaces (peritoneum, synovium) and other tissues.
How to monitor for S. pneumoniae infection?
Nasopharyngeal culture on blood agar.
What is the role of optochin inhibition in diagnosing S. pneumoniae?
Used to differentiate S. pneumoniae from other alpha-hemolytic streptococci; optochin inhbition is greater for most S. pneumoniae than other species.
What is optochin inhibition?
Ethylhydrocupreine hydrochloride (optochin), is a quinine derivative. Optochin selectively inhibits the growth of Streptococcus pneumoniae at very low concentration (5 mg/mL or less). Optochin may also inhibit viridans streptococci, but only at much higher concentrations.
Optochin is water-soluble and diffuses readily into agar medium. Filter paper disks impregnated with optochin can be used in a disk diffusion test.
Does a PCR positive for S. pneumoniae indicate a health concern?
Not necessarily. S. pneumoniae may be detected from PCR of nasopharnyx or lung, but there are nonpathogenic isolates. Need to confirm with histopath. Isolation of S. pneumoniae from asymptomatic rats is not necessarily a colony health threat.
What is the recommended control strategy for S. pneumoniae in a rat colony?
Action to eliminate only indicated in presence of characteristic lesions or detection of known pathogenic serotypes - depopulation and restock from an SPF source.
Is asymptomatic carriage in rats of S. pneumoniae detrimental for research studies?
Physiologic variability associated with asymptomatic carriage has not been reported.
How are beta-hemolytic streptococci divided into groups?
By Lancefield antigens. Lancefield groups B and G most commonly isolated from rats.
When have beta-hemolytic streptococci been associated with disease in rats?
Only in one case of naturally occurring dz - a Group B streptococci was linked to myocarditis and abscesses in 21-24 day old pups of a Munich Wister-Frömter line transgenic for human diphtheria toxin.
Exclusion of beta-strep from rat colonies is neither necessary nor practical; human are often carriers.
What is streptococcal enteropathy?
Cause by nonhemolytic (gamma-hemolytic) Lancefield group D enterococci, including Enterococcus hirae, E. faecium-durans 2, and E. faecalis 2. Affects only suckling rats, not postweaning animals. Affected litters have diarrhea or soft stool that is bright yellow & pasty. Mortality can be high. Villi of small intestine are carpeted with G(+) cocci. Pathogenic isolates involved have the ability to adhere to the surface of microvilli
What are autochthonous flora?
Microorganism native to the host environment. Some Enterococcus spp. have been considered autochthonous flora in the rat.
How can streptococci be excluded from rat housing?
Aseptic microisolator technique or by use of isolators. Low incidence of disease may not warrant the additional time and expense to do this.
What is the etiologic agent of pseudotuberculosis in rats, mice, guinea pigs, and hamsters?
Corynebacterium kutscheri. G(+) coryneform (club-shaped); found in soil, sewage, and marine environments. In guinea pigs and hamsters there has only been bacterial evidence, but no disease reported.
What is the route(s) of transmission for Corynebacterium kutscheri?
Direct contact or oronasal exposure.
What are the clinical signs of Corynebacterium kutscheri?
Usually clinically silent. Advanced dz may have non specific signs - ruffled fur, hunched, dyspnea and rales, porphyria, mucopurulent ocular & nasal discharge, lethargy, lameness; usu followed by death in 1-7 days.
What are the gross pathology lesions of Corynebacterium kutscheri?
Solitary or multiple randomly distributed abscesses due to septic emboli getting stuck in organs/tissues with extensive capillary networks - lung, liver, kidney, joints. LUNG most frequently involved in rats. Suppurative inflammation in the preputial gland and tympanic bullae.
What are the histopathology lesions of Corynebacterium kutscheri?
LUNG - interstitial inflamm d/t hematogenous seeding; suppurative exudate in bronchi and bronchioles; caseous necrosis common, epitheliod macrophages and multinucleated giant cells may be present in abscesses.
LIVER - large areas of caseous necrosis
KIDNEYS - septic embolic glomerulitis, abscesses with or without pyelonephritis
Abscesses and caseous necrosis in virtually any tissue.
How is Corynebacterium kutscheri diagnosed?
Definitive dx = culture or PCR; sampling sites include submaxillary (cervical) lymph nodes, oropharynx, nasopharynx, middle ears, preputial glands, feces.
Oral cavity, cecum, colon, and rectum may harbor organism.
Microscopic evaluation of lesions - irregularly branching arrays of G(+) rods in tissue sections or impression smears.
Serology - can have false positives or false negatives.
What is the best diagnostic sampling site for Corynbacterium kutscheri in rats?
Other than direct lesions, submaxillary (cervical) lymph nodes.
What factors can trigger latent infections of Corynebacterium kutscheri to become clinical?
Stressors that cause immunosuppression - poor husbandry, overcrowding, shipping, malnutrion, intercurrent infections, irradiation, immunosuppressive drugs.
Increasing age - disease is more frequent in older animals.
What are differential diagnoses for multiple abscesses in rats?
Streptococcosis, streptobacillosis, mycoplasmosis (pulmonary abscesses), cilia-associated respiratory (CAR) bacillus (pulmonary abscesses).
Of these, ONLY CAR bacillus and mycoplasmosis would be found predominantly in older animals.
What tissue conditions are preferred for PCR to check for Corynebacterium kutscheri?
Fresh or frozen tissue are preferred to formalin-fixed paraffin-embedded tissue.
