Contemporary Topics 39 (3)

1999

Fenbendazole treatment without environmental decontamination eradicates Syphacia muris from all rats in a large, complex research institution. Contemporary Topics 39(3), 9.
Abstract: Syphacia muris is the most widespread rat pathogen in research facilities in the U.S. and can exert untoward effects on growth, immunology, and digestive physiology. To eradicate this pinworm from rats and 2 colonies of voles (Microtus ochrogaster and M. montanus ) in a large, complex research facility with a minimal effect on research projects, fenbedazole-medicated chow (150 ppm) was fed for five 7-day periods with a week in between treatments. No environmental clean-up was done, nor was breeding or scientific research halted. Treatment was effective immediately in voles, and no eggs were found in rats after 22 days.
Questions:
1.) Which of the following is NOT true for Syphacia muris :
a.) Short pre-patent period
b.) Indirect life cycle
c.) ability to autoinfect
d.) hardiness of the egg in the environment
2.) What are 2 disadvantages to the use of ivermectin for treatment of pinworms?
3.) Besides the cellophane tape-test, how is Syphacia muris diagnosed (at post mortem)?
Answers:
1.) b (direct life cycle)
2.) narrow spectrum of efficacy, and preponderance of side-effects; also more labor intensive to apply ivermectin topically or prepare and distribute medicated drinking water (light sensitive).
3.) exam of cecal contents (81% sensitive, versus 67-88% sensitivity for anal tape test).

Declawing of neonatal rabbits destined for use in animal biosafety level 4 containment studies. Contemporary Topics 39(3), 13.
Abstract: This paper describe a procedure to declaw rabbits kits within the first 8 days of life by combining techniques used to remove the declaws of canine pups with methods used to declaw cats. Personnel working in Animal biosafety Level 4 are required to wear a one piece, ventilated positive-pressure containment suit. This suit is made of 2 mm. thick (not 20 mm. as described in this paper) chlorinated polyethylene that can accidentally be punctured, exposing the user to a potentially lethal infectious agent. To protect the suits from damage, rabbits normally are declaw at 3 to 4 months of age by removing the distal phalanx (P3) from each digit. This procedure requires significant surgical effort and causes considerable discomfort for ambulatory rabbits. Therefore, declawing at an early age might be more humane.
Pilot studies to assess the doe's willingness to accept kits that have been surgically manipulated demonstrated that in no case dis does reject any of their offspring. For pre-surgical analgesia buprenorphine was used 30 min. prior to anesthesia. Isoflurane by nose cone was used for general anesthesia. After preparation for surgery, a packer mosquito hemostat between the second and third phalanx. the distal digit was then removed with a scalpel blade #15. Cyanoacrylate glue was applied. Post-operative bleeding was minimal and bandaging of the feet was never used. Declawing was performed on 3, 6, 7, and 8- day-old kits weighing more than 90 g. It was determined that the acceptable age range for declawing was 6 to 8 days. The non-ambulatory status of the kits at the time of the surgery was beneficial. The procedure is relatively simple, the post-operative care is neglegilble, the effect on the animal is minimal and rabbits can be introduced into the ABSL-4 facility by 3 months of age.
Questions:
1. T or F Animal Biosafety Level 4 involves practices suitable for addressing dangerous or exotic agents that pose high risk of life threatening disease, aerosol transmission or related agents with unknown risk of transmission
2. T or F In a ABSL-4 suit operation, a complete clothing change is required. A personal shower is required following removal of decontaminated suit. soiled lab clothing is laundered before autoclaving.
3. Indicate the recommended ABSL (1, 2, 3, 4, or 5) practices for the following:
a) Bacillus anthracis infected laboratory rodents
b) Transmissible Spongiform Encephalopathy experimentally infected rodents
c) Coxiella burnetii experimentally infected rodents
d) hendra virus infected livestock
e) LCM virus infected hamsters
Answers:
1 T, 2 F, 3 a2, b2/3, c3, d4, e3

Anesthesia of six-week-old new zealand white rabbits for thoracotomy. Contemporary Topics 39(3), 19.
Abstract: Introduce a method for intubation using direct laryngoscopy and for administration of anesthesia applicable to six-week-old NZW rabbits. These young rabbits are used in a research of the effects of anterior thoracic spinal procedures on the growth of young rabbit spines.
Benefits of this method of intubation and anesthesia:
1. direct laryngoscopy for correct atraumatic intubations
2. no need for premedication
3. able to deliver positive pressure ventilation
4. achieve deep levels of surgical anesthesia, maintain anesthesia and with rapid reversal.
Procedures: 5% isoflurane in a anesthesia box, then direct laryngoscopy by using an otoscope. A 5-French polypropylene catheter was passed through the spectrum of otoscope and through the vocal cords. The endotracheal tube was advanced over this guide and rabbit would have cough reflex (an index for correct placement) when the tube passed though the vocal cord.
Questions:
1. Tracheal intubation of rabbit is difficult due to the small size of the mouth and larynx and the propensity of rabbits to develop reflex laryngospasm. (T or F)
2. What's taxonomy of the NZW rabbit?
Answers:
1. True
2. Order-Lagomorpha
Family-Leoridae
Genus-Oryctolagus
Species-cuniculus (European rabbit)

Mammalian thermoregulation: species differences. Contemporary Topics 39(3), 23.
Abstract: Tissues factors that affect thermoregulation are: brown fat, leptin content, sweating, panting, neural control, and heat shock proteins. Euthermic animals maintain body temperature within narrow limits. Basil Metabolic Rate (BMR) is defined when the body is at complete rest, in a thermal neutral environment, in a post-prandial state. Body temperature (Tb) can be divided into "core" and "shell" temperature. Core temp. is defined as brain and contents of abdomen and thorax. Shell temp includes skin, SQ, muscle, limbs. Thermal neutral zone is the ambient temperature (Ta) at which maintenance of Tb is least difficult. Resting metabolic rate (RMR) ignores digestive activity and is assessed when animals are at rest in a thermal-neutral environment. Lower critical ambient temp (Tcr) is when additional heat must be generated to maintain Tb.
Heat Generation:
Basic rate in euthermic mammals is 70 Kcal/kg 0.75 daily, therefore every doubling of body mass BMR/unit body tissue decreases ~15%. Cells of large mammals, compared to small, have more mitochondria, more double bonds in fatty acids, and more Na+-K+ pump activity across cell membranes. A mouse can only increase its RMR by a factor of 3-5, whereas a rat can increase 5-7 X, and humans can increase 15-20 X. Heat is produced in endotherms by shivering or exercise. Many endotherms can also produce heat by non-shivering thermogenesis (NST): action of norepinephrine on brown adipose tissue (BAT). BAT has extensive vascularization, many mitochondira, and proteins that uncouple mitochondria from their ATP generating activity so that energy of oxidation is liberated as heat. One form of BAT is found in all hibernating animals and another form is found in many neonates for only the post-natal period. Marsupials and monotremes have no BAT. FOK rat which is inbred for resistence to heat, has low BAT activity and secretes more saliva from the submaxillary salivary glands than other rat strains. The evapouration of each gm of H2O from saliva at 30 degrees causes a heat loss of 576 kcal (2421kJ). Leptin, a hormone secreted by white adipose tissue, suppresses food intake and increases energy expenditure in proportion to body fat levels. The Zucker rat (fa/fa) rat, characterized by excesive food intake, is relatively insensitive to leptin.
Fever:
It is not a failure of Tb regulation but an "acute defense response". It is characterized by reductions in plasma levels of zinc and iron, and release of "endogenous pyrogens", cytokines that induce fever. Endogenous pyrogens include interleukin 1, Il-2, IL-6, tumour necrosis factor (TNF), and interferon alpha and beta. Exogenous pyrogens, lipopolysachrides of bacterial cell walls, stimulate endogenous pyrogens to produce fever. IL-8 induces febrile response in rabbits and rats. Indomethacin inhibits this in rabbits but not in rats. Corticotropin releasing factor mediates IL-8 in rats but attenuates fever in rabbits. Dexamethosone abolishes fever (caused by IL-8 and lipopolysac) in rats, but not as well in rabbits. Aspirin resets the thermostat only in febrile mammals, however in rats will reduce t he Tb even if there is no fever and even when the Ta is as low as 5 degrees C. Obese rats (fa/fa) are much more responsive to Il-1 than lean (Fa/Fa) rats, however the opposite is true for Il-6.. Etiocholanolone, an intermediate metabolite of testosterone is one of the few steroids that induce fever in humans and Macaca mulatta. New world monkeys have no 5 alpha- or 5 beta-reductase to act on etiocholanolone to form Il-1.
Inflammation:
Cytokines (IL-12) produce reactive O2 species (respiratory burst) with lipid mediators (prostaglandins and leukotrienes) and proteases. The transciption of heat-shock genes and the sythesis of heat shock proteins contribute to the defense against inflammation, as does leukemia inhibitory factor.
Heat Dissipation:
Heat is lost by conduction, convection, radiation, and evapouration. Conduction takes place when physical bodies are in contact with each other.Convection refers to the transfer of heat when a fluid flows over a solid body or thru a channel. Radiation is the loss or gain of heat by electromagnetic rays. Dominant response to heat in mammals is an increase in the blood flow to peripheral BV. Apical regions (ears, nose, lips, hands, feet, tails) are rich in arteriovenous anastomoses, and are enriched with blood refexively by loss of vasomotor tone. Baboon and rat respond to heat only by a reflex loss of vasomotor tone and not by active vasodilation. The rat, muskrat and squirrel monkey increase flow to tail reflexively during heat stress. Heat dissipation occurs thru ears of rabbit, and the horns of cattle and Pene David's deer. Evapouration is the most effective means of heat loss. It takes 100 cal to heat 1 gm of water from freezing to boiling and 584 cal to change 1 gm of liquid H2O to water vapour at room temp. Sweating, panting, salivation, licking are eg of evap. Humans, horses, cattle, camels sweat profusely. Rodents, lagomorphs, pigs, dogs, cats, elephants, gazells cannot. Eccrine glands secrete hypotonic sweat ~99% water, and apocrine glands, which
develop from hair follicles, secrete hypertonic sweat. Eccrine are stimulated by cholinergic receptors by adrenergic nerves. Apocrine glands(horses) stimulated by Beta-adrenergic receptors. During panting (dogs and sheep) the tendency is to decrease the CO2 tension in the blood to critical levels.
Species Differences in Response to Variations in Ta: Nine-banded armadillo increases its Tb when subjected to a decrease in Ta. Marsupials, monotremes, insectivores, and the desert mouse (spiny mouse) the normal Tb is lower than in most mammals. Desert rodents, spiny mouse, has a decrease utilization of glucose, a condition that subjects the animals to hyperglycemia when fed lab chow and to a 20% incidence of diabetes. A camel (and hippo) when subjected to extreme heat increase their Tb. For a 500 kg camel, a 7 degree change in Tb corresponds to 2900 kcal of heat and a saving of 5 L of water that would otherwise be required to maintain Tb by evapouration. The Tb can be lowered during the night when cooler.
Torpor:
Includes hibernation (winter) and estivation (summer). Evolved as a means of saving energy when the lower crtical temp zone has been exceeded or food/water source is diminished. It is an advanced form of thermoregulation.It incolves a resetting of the thermal centre located within the subfornical organ in the vicinity of the hypothalamus. Torpor is either seasonal or non-seasonal. Seasonal is controlled by circannual rhythm and independent of Ta change. Non-seasonal is very sensitive to environmental changes. Marsupials and bats have both types of torpor. Estivation occurs wehn limited food and water and is an adaptation to hot, dry environments. Hibernation is reponse to cold. Deer mice when restriced to drinking water, underwent a 25% decrease in metabolic rate and a 47% decrease in evapourative water loss.
Questions:
1. For every doubling of the body mass, the BMR reduces by -----------%?
2. The Ta at which the maintenance of Tb is least difficult is called?
3. What hormone is secreted by white adipose tissue?
4. What endogenous pyrogen induces febrile response in the rabbit? in the rat?
5. Torpor in response to hot, dry environments is called?
Answers:
1. 15%
2. Thermoneutrality zone
3. Leptin
4. IL-8
5. Estivation

Housing of dogs in simulated home environments for the study of the efficacy of drug activity against fleas. Contemporary Topics 39(3), 28.
Abstract: The study was conducted to determine if a self-propagating flea life-cycle could be established in a simulated home environment. These types of studies are often conducted to ascertain the effectiveness of a particular flea treatment, and are often done within the homes of private individuals that own pets. Noncompliance by pet-owners can occur if the flea infestation becomes overwhelming, or if the pet develops pruritis or other clinical manifestations of the flea infection.
Therefore, a dog room was designed to maintain flea infestation in a simulated home environment using dogs. A specially-designed dog room with carpeting was used and the husbandry practices were meticulously performed to ensure that no fleas were transfered by personnel between pens of treated and untreated animals. Dog weights were recorded throughout the study, and weekly flea counts were taken from each dog for 11 weeks.
The various products that have been tested using this simulated environment include lufenuron, methoprene, imidacloprid, and other proprietary products still in development. In this paper, the author shows that a self-propogating flea population was established for up a minimum of 11 weeks. Under most household conditions, the flea life cycle is 3-5 weeks.
Questions:
1) What is the genus and species of the cat flea?
2) How does Lufenuron work to control fleas?
3) How does imidacloprid work to control fleas?
Answers:
1) Ctenocephalides felis
2) Lufenuron prevents the flea eggs and flea larvae from developing. It prevents the linking of a chain of molecules that make chitin. Chitin makes up the hard shell of the adult flea, as well as an egg-tooth that flea larvae use to break out of their eggs. Without chitin these stages cannot develop properly and the life cycle is broken. Lufenuron is stored in the pet's body fat and released over the course of 32 days following dosing. Lufenuron is the active ingredient in the product "PROGRAM" sold as an oral medication.
3) Imidacloprid works by interfering with the transmission of stimuli in the insect nervous system. Specifically, it blocks nicotinergic pathways, that are more abundant in insects than in warm-blooded animals (making the chemical selectively more toxic to insects than warm-blooded animals). This blockage leads to the accumulation of acetylcholine, an important neurotransmitter, resulting in the insect's paralysis, and eventually death. It is effective on contact and via stomach action. Imidacloprid is the active ingredient in the prooduct "ADVANTAGE" sold as a topical insecticide.

Parotid gland papillary cystdenocarcinoma in a Fischer 344 rat. Contemporary Topics 39(3), 31.
Abstract: Thirty types and subtypes of primary epithelial salivary tumors have been described in humans, but salivary gland tumors are rare in rats. Previously described salivary gland tumors in rats are 1) squamous cell carcinomas with keratin formation, 2) acinar or tubular adenomas/adenocarcinomas, 3) a pleomorphic adenoma in the submandibular gland, and 4) a poorly differentiated carcinoma in the parotid gland.
This report described a tumor that occurred in a 72 week old female Fischer 344 rat that was involved in a pharmacological study to identify carcinogenic drugs. No other rats developed tumors and this rat was determined to have a spontaneous occurring tumor. The tumor was 23x20x18 mm and was well circumscribed in the left neck region. The tumor was excised after euthanasia and examined histologically. The tumor consisted of multiple various sized cysts. Most of the cyst lumina contained numerous branching papillae with a thin fibor-vascular core. Atrophied parotid gland tissue was found between and in the periphery of the cystic lesions. The tumor was partially encapsulated but had invaded the dermis beyond the muscle layer of the skin. No metastatic lesions were found. The tumor was diagnosed as a papillary cystadenocarcinoma of the parotid gland which is the first reported case of a tumor of this type
in the rat.
Questions: No questions

Neoplastic mass in an experimental mongolian gerbil. Contemporary Topics 39(3), 34.
Abstract: History: 33-month-old male Mongolian gerbil (Meriones unguiculatus) with a rapidly growing, firm, immovable mass encompassing the right thoracic limb and extending across the ventral thoraxà unable to ambulate on the affected limb. In a conventional colony with a history of pinworms and Clostridium piliforme, but apparently not affected by said organisms. On an IACUC-approved protocol as a model for human filiariasis, infected with Brugia pahangi organisms subcutaneously. SACÆd due to poor prognosis.
Diagnostics: CBC only û RBC count normal, with slight decrease in hemoglobin and hematocrit; leukocytosis with neutrophilia (6% bands), lymphocytosis, monocytosis, and disintegrated WBCÆs.
Pathology: Pale yellow, firm, 4x3x2 cm, 16 g, well-encapsulated lobulated mass engulfing right humerus, proximal radius and ulna, and involving the right thoracic wall (without thoracic invasion) from neck to last rib.
Spleen 3x normal size with raised pale, yellow nodular masses bulging from capsule and cut surface; one mesenteric lymph node 2-3x normal size.
Microscopic lesions included solid sheets of moderately differentiated, uniform, large lymphocytes bearing scant cytoplasm with indistinct borders, high nuclear:cytoplasmic ratio, pleomorphic nuclei with few prominent nucleoli, 10-12 (normal + atypical) mitotic figures per HPF. Aggressive infiltration of lymphocytes into muscle tissue; found also in PeyerÆs patches, spleen, lung, liver, and mesentery. Forelimb bone had hypercellular marrow with large blastocysts (round to pleomorphic nuclei) rather than granulocytic precursors, erythroid cell line, and fat; extensive resorptive activity and woven bone deposition on periosteal surface of cortex suggesting tumor-associated bone modeling. Wright-stained blood smear showed numerous medium to large lymphocytes with prominent nucleoli; larger in size than neutrophils.
Diagnosis: Lymphoblastic lymphoma with concurrent leukemiaà significant as lymphoreticular neoplasms are rare and metastasis is unusual in gerbils; first published report of a spontaneous homogenous lymphoma in M. unguiculatus.
Questions:
1. What lymphoma has been reported in other Gerbillinae?
2. What forms of spontaneous neoplasms are common in M. unguiculatus? What age?
3. Do gerbils show a gender difference in developing neoplasms?
4. Beyond neoplasia and not counting TyzzerÆs or salmonellosis, what two other gross or histologic lesions have been reported in aged gerbils?
Answers:
1. Hodgkins-like lymphoma (ref: LAS 22(3):407-414, Vet Pathol 11:38-51)
2. Incidence of spontaneous neoplasia in gerbils > 2 yrs is rather high. Affected organs in decreasing order of frequency (Bluebook, p. 199):
- OVARY: granulosa cell tumors, theca cell tumors, leiomyoma
- SKIN: SCC, melanoma, sebaceous gland pad adenoma, carcinoma
- KIDNEY: adenoma, hemangioma
- ADRENAL: cortical adenoma or carcinoma
- CECUM: adenocarcinoma
- LIVER: hepatoma, bile duct adenoma, cholangio-carcinoma
- UTERUS: carcinoma, hamangiopericytoma, leiomyoma
- PANCREAS: islet cell adenoma
- TESTIS: teratoma, seminoma
Others (LAS 29:645-651) report adrenal (cortical adenoma), ovarian (granulosa cell tumors, leiomyomas) and cutaneous neoplasms (squamous cell carcinoma) most common
3. Females have a higher incidence of neoplasia than males (Lab Anim Care 15(5):281-294).
4. Amyloidosis (uncommon, spontaneously occurring, associated with experimental infection with filarid Litomosoides carinii) and cystic ovaries (Bluebook, p. 199).