Vendor Apparent Source of Mouse Parvovirus in Sentinel Mice ( P. 8-11)
Contemporary Topics
Volume 43, Issue 4 (July 2004)
Vendor Apparent Source of Mouse Parvovirus in Sentinel Mice (p. 8-11)
Summary: Mouse Parvovirus (MPV) is growing in prevalence in laboratory animal facilities. It tends to be hardy in the environment and can be transmitted primarily by fecal oral contact and fomite spread. After the detection of sporadic MPV in the sentinel population, the author developed a system to assess vendor mice used as sentinels by group housing them in individually identified large cages (A-U) in a isolation type location, deploying some as sentinels into the facility, while retaining some in the isolation location. Two mice from each of these cages were tested serologically for murine viruses 3 weeks after arrival and before sentinels were deployed from them. All tested negative at the time.
After a month, the sentinels were eye bled under anesthesia or terminal collections were done on mice euthanized with CO2. The blood was analyzed using at a major testing facility to look for routine murine viruses including MPV. The results indicated that mice deployed from cage C in the isolation area were positive for MPV. As a matter of of fact all the sentinels deployed from cage C were positive for MPV. None of the other group housed cages in the isolation area had deployed sentinels that tested positive. At this time the remaining mice in cage C which had been isolated and not exposed to other mice were tested and they too were seropositive. This seems to indicate that there is a possibility that these mice came in from the vendor infected with MPV, and subsequently seroconverted in the lab animal facility.
While the vendor facility tested rigorously (.8% of the population monthly), they housed their mice in open top cages with the prevailing thought being that if all of the mice would be exposed to everything by aerosol. MPV has been documented to be transferred by direct contact (contact sentinels), and by fomite (dirty bedding), but has not been documented as being transmitted by aerosol. This may account for it not being detected at the vendor location.
Questions:
1. Parvoviruses are:
a. Hardy
b. Transmitted by fecal oral
c. Becoming more prevalent in research facilities
d. All of the above
Answer D
Title: Evaluation of Cage Micro-Environment of Mice Housed on Various Types of Bedding Materials (pages 12-17)
Summary:
A variety of environmental factors can affect study outcomes. Bedding is one such factor. This study addressed the cage micro-environment (ammonia levels, temperature, humidity) of mice on different beddings and their combinations. The types of beddings studied were as follows: ALPHA-dri (Alpha cellulose), Bed-O"-cobs (corncob), Beta Chip (Hardwoods maple, beech and poplar), Cell-Sorb Plus (recycled newspaper), CareFRESH Ultra (long-fiber, high-grade bleached pulp), and pine shavings. The study also compared results for bedding supplied as Nestpaks vs. loose bedding.
With the exception of one component of the study that compared static vs. ventilated cages, the remaining mice in this study were housed in static duplex cages for a period of three weeks with no change-out. Each side of the duplex cage housed 4 male mice or a litter with both parents. The results showed little effect of bedding type on in-cage temperature and humidity but considerable variation in ammonia concentrations.
Past studies have reported the effects of exposure to gaseous ammonia on laboratory rodents. Such effects have included mortality in rats, immunosuppression in guinea pigs, decreased concentration-dependent running (on a wheel) in Long-Evans rats and Swiss mice, and decreased ciliary activity in rats. A previous study showed that, regarding rats undergoing continuous exposure to 262 ppm ammonia for 90 or more days, 25% had a mild nasal discharge. Continuous exposure to >400 ppm ammonia resulted in the death of 32 of 51 rats by day 25 of exposure and 50 of 51 by day 65. These rats had mild dyspnea with nasal irritation. However, the authors also pointed out that the early literature that addressed the noxious effects of ammonia concentrations on rodents must be considered in the context of their microbial status at the time. Infectious diseases of the respiratory tract, specifically M. pulmonis infection in rats, have been reported as cofactors in ammonia toxicity. Therefore, contemporary rodents may be able to tolerate higher in-cage ammonia concentrations in the absence of such exacerbating cofactors.
Human exposure to ammonia concentrations as low as 20 ppm can cause discomfort and conjunctival hyperemia. Standards put forth by NIOSH (National Institute of Occupational Safety and Health) indicate that workplace exposure to ammonia should not exceed 25 ppm over 8 hours or 35 ppm over a 15 minute period. There are no accepted standards for rodent exposure to ammonia. In the absence of data indicating what ammonia concentrations might be noxious for mice, the authors suggest we may need to defer to the OSHA standards established for people.
The ammonia levels in cages with loose bedding did not differ from those with Nestpaks containing the same bedding. Beta-chips and a combination bedding (Bed-O-Cobs mixed with ALPHA-dri) yielded the lowest intra-cage ammonia concentrations. CareFRESH Utlra bedding yielded the greatest ammonia concentrations of all beddings studied. In light of cage micro-environment results, especially ammonia levels, the authors concluded that all bedding types that evaluated, except for CareFRESH Ultra, were acceptable choices for use in static cages and that the practice of changing bedding every 2 weeks would likewise be acceptable. Ammonia concentrations in ventilated cages housing mice on CareFRESH Ultra bedding were acceptable, however.
Questions:
1. T/F Infectious diseases of the respiratory tract coupled with
ammonia levels have been reported as synergistic factors in regards to ammonia toxicity.
2. What does the acronym NIOSH stand for?
Answers:
1. True
2. National Institute of Occupational Safety and Health
To Enrich or Not to Enrich: Providing Shelter Does Not Complicate handling of Laboratory Mice (pages 18-21)
Summary
The authors describe Environmental Enrichment (EE) as a method used in laboratory animal housing to provide stimuli exceeding those of barren cages and is intended to improve the welfare of captive animals.
Providing EE is more effective in reducing abnormal behavior than is housing animals in larger cages. The authors mentioned some of commonly used methods of EE for rodents as providing access for conspecifics, shelters, nesting materials, climbing structure, and gnawing objects. Animals when given access to EE, express a more species specific repertoire of behavior, have a better learning abilities, neurologically more stable and don’t perform stereotypic behavior to the same degree as when maintained without EE.
Specific aim of this study was to evaluate whether the use of EE would complicate catching and handling mice by comparing the time needed to catch animals and by evaluating the response to handling. Inbred FVB/Nhan Hsd and outbred NMRI/Hsd Win strains were used in the study.
The study was conducted by housing 20 FVB and 20 NMRI male mice in Standard cages and another 20 FVB and 20 NMRI male mice in cages enriched with two PVC conduits. Measurement of food, water consumption, weight, latency Of catching, and a behavior score in response to handling during a sham subcutaneous injections were performed weekly for four consecutive weeks when mice were 10 weeks old.
Food and water consumption and weight were influenced by strains, but The presence of EE in the home cage did not affect these parameters as much.
Outbred mice ate, drank, and weighed more than the inbred mice, but didn’tsignificantly gain weight during the course of the four testing weeks. Cage enrichment in the form of PVC conduits decreased the time needed to catch outbred mice and didn’t increase the time needed to catch mice from the inbred strain. No difference in resistance to being held during the sham injection between animals from the enriched versus non-enriched group.
In conclusion, the authors, based on the result of the study suggest, EE in the form of sheltering object doesn’t complicate catching or handling. Allowing access to enrichment in the laboratory cage, which has been Shown to have positive effect on welfare, doesn’t interfere with the management or cost of laboratory animals.
Endotracheal Tubes Versus Laryngeal Mask Airways in Rabbit Inhalation Anesthesia: Ease of Use and Waste Gas Emissions (p. 22-25)
The rabbit is a standard animal model for biomedical research in which many procedures require anesthetic procedures. The anatomical features of the rabbit makes it difficult to use inhalation gas anesthesia. This purpose of this study was to compare ease of placement of cuffedendotracheal tube, uncuffedendotracheal tube (Cole) and pediatric laryngeal mask airways (LMA) and to assess the extent of anesthetic pollution. A second purpose was toproduce a comprehensive procedure for the placement of LMAs in the rabbit The hypothesis was that the LMAs would be a simpler method of gas delivery but would permit greater leakage of anesthetic gas. The reason for the study was to develop training procedures for animal technicians and researchers to deliver gas anesthesia with lecture and hands on training.
Rabbits were anesthetized with ketamine and xylazine and maintained with isoflurane using a precision vaporizer to two circuits, one to a two liter acrylic box and on with direct delivery to the animal. The exhaust system was connected to gas-scavenging canisters. Thesystem was calibrated beforeuse and evaluated with portable equipment during the study for leaks. Also, during the study waste gas was measured at the rabbit's oral commissure and in the operator's breathing zone. Rabbits were recovered on heating pads maintained at 37 degrees C.
Rabbits were placed in ventral recumbancy with the heads tilted up at a 90 degree angle to inset the endotracheal tubes blindly into the trachea. The tubes were advanced with the convex side of the tubeagainstthe pharynx down into the trachea. The rabbits were placed in right lateral recumbancy for LMA placement and the head tilted upward90 degrees. The LMAs were held laterally with the aperture turned toward the tongue and the LMA wererotated 90 degreesin a counterclockwise so the cuff would cover the edges of the larynx.
Rabbits were evaluated every 5 minutes for pain (toe pinch) and levels of waste anesthesia weremeasured. The original hypothesis was proven to be true; LMAs are easier to place for animal technicians and researchers with a minimal amount of training. Adequate levels of anesthesia were established and maintained during the study. In addition, smaller amountsof anesthetic waste was emitted from both the cuffed and non-cuffed endotracheal tubes as compared to the LMAs emissions which was higher and statistically significant. However, the amounts of emitted isoflurane from all three anesthesia delivery methods exceeded NIOSH levels of 2 ppm; theresults of this study measured 6.3 to 8.4 ppm at the commissures of the rabbits' mouths. The waste anesthesia levelsdid not surpassmost common European8 hr time-weighted average defined for stand-alone use of isoflurane (10 ppm established by Germany, Sweden and Switzerland).
Questions:
1. What were the three methods of distributing isoflurane tothe rabbits in the study?
2. (True or False) Did the wasteanesthesia measured in this study meet HIOSH guidelines?
3. Which guideline did the wasteanesthesia for this method meet?
Answers:
1. cuffedendotracheal tube, uncuffedendotracheal tube (Cole) and pediatric laryngeal mask airways (LMA)
2. False
3. European8 hr time-weighted average defined for stand-alone use of isoflurane (10 ppm established by Germany, Sweden and Switzerland)
Vitamin A Toxicity and Vitamin E Deficiency in a Rabbit Colony (pages 26-30)
Summary: Clinical signs of both vitamin A toxicity and deficiency include absorption of fetuses, abortions, stillborn kits, decreased litter size, low neonatal viability, and hydrocephalic kits. Hypovitaminosis A can affect cartilage formation in rapidly growing rabbits, which present clinically with droopy ears. Except in cases of severe deficiency or toxicity, rabbits maintain fairly constant blood serum levels of vitamin A; therefore, serum levels may not accurately reflect an animal’s true vitamin A status. Liver values provide a more faithful representation of vitamin A status and are thus considered the “gold standard.”
Rabbits are the most sensitive laboratory animals to vitamin E deficiency. Accordingly, rabbits have been used as models to determine the physiological role of vitamin E. Vitamin E functions as an anti-oxidant that prevents peroxide damage to tissues. Clinical signs of vitamin E deficiency in kits include muscular dystrophy, with paresis to paralysis of hind limbs. Breeding does experience problems with infertility, abortions, stillbirths, and in vivo hemolysis. Vitamin E deficiency can be diagnosed by the in vitro peroxide hemolytic test, serum Creatine Phosphokinase, or vitamin E levels in the serum or liver.
Vitamin E has been shown to modulate the effect and levels of vitamin A. Whereas small doses of vitamin E increase vitamin A utilization, larger doses markedly reduce the amount of vitamin A formed and stored in the liver.
Vitamin A toxicities are frequently reported in rabbit literature, but no treatment regimens have been proposed. Here the authors evaluate vitamin A and E levels in rabbits with clinical signs of vitamin A toxicosis and vitamin E deficiency, and assess the impact of vitamin E-based therapy on clinical signs, reproduction, and vitamin A and E levels.
Case presentation: A concerned commercial rabbitry owner contacted MURADIL regarding a 4-6 week history during which several does had reabsorbed fetuses or had spontaneous abortions or hydrocephalic kits. The few kits that survived were unthrifty or became weak, with most dying by 27 days of age. The diet consisted of a commercial pelleted rabbit chow that the owner had used with confidence for 4 years. Several rabbits were submitted to MURADIL for diagnostic necropsies. Vitamin A toxicosis and vitamin E deficiency were diagnosed. Specifically, laboratory tests showed elevated serum and liver vitamin A levels and low serum and liver vitamin E levels. The vitamin E deficiency had produced paresis and muscular dystrophy in the juvenile rabbits.
It is important to note that clinical manisfestations of toxicity or deficiency consequent to misformulated rations may remain silent for as long as 3 months in rabbits after eating the feed. In addition, one should note that hypervitaminosis A may result in elevated vitamin A levels in the milk at kindling and cause hypervitaminosis A in the offspring.
In addition, the owner donated several rabbits from the affected colony to MURADIL. The donated rabbits were provided Laboratory Rabbit Diet 5321 (Purina) and supplemented with parenteral vitamin E (SQ injections q 2 days X 14 days) to assess the effect of vitamin E therapy on clinical signs, reproduction, and vitamin A and E serum and liver levels. Over a 60-day period, this diet had little effect on serum vitamin E levels, and this finding may indicate that diet alone does not adequately correct hypovitaminosis E. In this study, pregnancy also may have played a role in the high serum vitamin A levels, as the females were close to kindling when samples were drawn. In dams, serum vitamin A levels are known to increase significantly at kindling, then decrease within 1 week after kindling to pre-parturition levels.
Blood samples were taken before and after dietary changes and vitamin E therapy. The parenteral administration of the vitamin E for 2 weeks lowered the serum vitamin A levels and increased the vitamin E serum and liver levels. In conclusion, vitamin E therapy appears to be an effective treatment for hypervitaminosis A. In addition, previous studies have shown that when high doses of vitamin A were given to rats, rabbits, and guinea pigs, the animals rapidly became deficient in vitamin E. The mechanism of interaction between vitamins A and E and its relevance to vitamin A toxicity are not fully understood.
In agreement with other findings, rabbits in this study appeared to return to normal reproductive levels 12 weeks after the RADIL diet change. The authors conclude that the administration of vitamin E decreases the serum levels of vitamin A in rabbits with hypovitaminosis E. Vitamin E therapy appears to be an effective treatment for hypervitaminosis A in rabbits, and it may decrease the teratogenic effects of hypervitaminosis A during embryonic development.
Questions:
- Why are rabbits are among the most susceptible laboratory animals to misformulated rations?
- Where is vitamin A primarily stored in the body?
Answers:
- Because of their rapid growth and development, heavy reproductive demands, and short gestation period.
- In the liver.
Vaginal and Cervical Atresia in a Cynomolgus Macaque (p 31-32)
Clinical Case Summary: A 2.5 year old, female, 2.3 kg, cynomolgus monkey ( Macaca fascicularis - captive-bred, and imported from south centralChina) presented clinically with a firm, slightly mobile mass in the caudal abdominal. Ultrasound exam revealed a fluid filled mass with a granular free-floating appearance that enlarged from ~2 cm in diameter on ultrasound to double the size within a month. Exploratory laparotomy revealed a large caudal abdominal mass encompassing the middle of the uterus, ovaries, rectum, and bladder. Due to extensive adhesions and severely decreased pelvic outlet, animal was euthanized under general anesthesia. Mass was removed and fixed in formalin. Histological evaluation identified the mass as an enlarged uterus with no neoplastic components. It appeared grossly that the cervix and uterus had no external opening and resulted in dilation of the uterus and fluid (blood, presumptive) build-up. There was also a lack of an opening between the cervix and vagina. Diagnosis: vaginal and cervical atresia. Different surgical techniques have been described to correct this anomaly in human patients, with some presented in the discussion section.