Fall 1997 Vol. 18, No. 1
Editor:
Benjamin J. Weigler, DVM, MPH, Ph.D*
Regional Primate Research Center
Box 357330
University of Washington
Seattle, WA 98195-7330
Telephone: (206) 616-1706
FAX: (206) 616-1710
E-mail: bweigler@bart.rprc.washington.edu
* Items for the Newsletter, general comments
Editorial Assistant:
Joan Bailie*
Yale Animal Resource Center
Yale University
220 South Frontage Road
New Haven, CT 06510
Telephone: (203) 785-7256
FAX: (203) 785-3099
E-mail: joan.bailie@yale.edu
* Address changes, memeber dues
ACLAD Officers 1997:
PRESIDENT
John D. Strandberg (E-mail: jstrand@welchlink.welch.jhu.edu)
VICE-PRESIDENT (PRESIDENT-ELECT)
Diane J. Gaertner (E-mail: gaertner@aecom.yu.edu)
SECRETARY & NEWSLETTER EDITOR
Benjamin J. Weigler (E-mail: bweigler@bart.rprc.washington.edu)
TREASURER
Kimberly Waggie (E-mail: waggiek@zgi.com)
COUNCILORS
Stephen W. Barthold (E-mail: swbarthold@ucdavis.edu)
Julia K. Hilliard (E-mail: juliah@icarus.sfbr.org)
WEB SITE RELOCATED:
The ACLAD Web Site has moved!
Please update your browser's bookmark to the following:
http://www.rprc.washington.edu/aclad/index.html
CONTRIBUTORS THIS ISSUE:
CONTRIBUTORS THIS ISSUE:
1. Susan Stein. Hamster disease outbreak at Michigan State University.
2. Patricia L. Farrar and Marie LaRegina. Diagnostic Exercise: Interstitial
pneumonia in viral and mycoplasmal antibody-free Sprague Dawley rats.
3. Lisa J. Ball-Goodrich, Stuart E. Leland, Elizabeth A. Johnson, Frank
X. Paturzo, and Robert O. Jacoby. Rat parvovirus-1 (RPV-1): The prototype
for a new rodent parvovirus serogroup.
4. David Knudsen and Alison Pohl. Retrospective incidence of diagnostic
syndromes in a SCID mouse barrier colony (1993-1996).
5. Karen A. Sokol. Update on the quality assurance program.
AALAS MEETING ANNOUNCEMENTS:
1. The Scientific Program
ACLAD'S scientific program at the 48th AALAS National Meeting has been scheduled as Seminar Session S-11 on Tuesday, November 18th 1997 to be held from 2:00 - 5:00 p.m. in Room A-9 of the Anaheim Convention Center. The seminar title, "FAQ's in Rodent Health Monitoring," will be chaired by Dr. Lela K. Riley and includes a variety of timely and important topics, as follows:
"Diagnostic serology: Do's and don'ts" by Dr. Earl Steffen
"Molecular Diagnostics: To PCR or not to PCR" by Dr. Lela Riley
"Background lesions: Are they significant or can I ignore them?"
by Dr. Craig Franklin
"Pathogens, opportunists, or commensals" by Dr. Robert Russell
"My rodents are infected. Now what do I do?" by Dr. William White
2. The Wally Rowe Lecture
ACLAD is proud to announce that this year's Wallace E. Rowe lecture is to be given on Tuesday, November 18th 1997 at 11:00 in Room B-1 of the Anaheim Convention Center by Dr. Marian G. Michaels, an Assistant Professor of Pediatrics and Surgery at the University of Pittsburgh. Dr. Michaels will present the topic,
"Xenozoonoses: The possibility of infection after cross species transplantation. Where are we now?"
Dr. Michaels received her undergraduate degree in anthropology from Yale
University, her MD degree from the University of Pennsylvania, and her MPH
in epidemiology from the University of Pittsburgh. Her research interests
include xenotransplant infections and epidemiologic follow-up of case-patients,
as well as infections among pediatric thoracic organ recipients. She has
served on numerous committees addressing the ethics and policies surrounding
xenotransplantation and the associated risks of post-transplant infections.
3. The Annual Luncheon for Trainees
DATE: TUESDAY, NOVEMBER 18, 1997
TIME: 12:00 noon - 2:00 PM
PLACE: Salons 1 & 2 Anaheim Marriot
CUISINE: Down Home Country Deli Buffet @ $27.00 per person
(including tax and gratuity)
TOPIC: This year's event will include a program entitled: "Keys to Successful Job Hunting." A panel of discussion leaders representing different areas within the laboratory animal medical profession has been scheduled, including academia, the military, private industry, and a research veterinarian.
Contact Valeria Krizsan at Yale University to purchase tickets for this luncheon (deadline November 1, 1997). Accepted forms of payment include a personal check or institutional check (no purchase orders please!), made payable to "Yale/Comparative Medicine 697A". Please send your check to Valeria at the Section of Comparative Medicine, Yale University, School of Medicine, P.O. Box 208016, New Haven, CT 06520-8016. She can also be reached via telephone (203) 785-2525 or e-mail (valeria.krizsan@yale.edu) for more information. Please come and participate in this important topic!
NEWSLETTER SUBMISSIONS:
As always, ACLAD is in need of high quality submissions for the Newsletter! In this issue, we highlight a new concept in communication for ACLAD members; the combination of printed text with images of the corresponding lesions displayed via the ACLAD Web Site. In this manner, ACLAD hopes that the information content of its articles will be substantially enhanced and rapidly available to the membership. See the article by Drs. Farrar and LaRegina in the Newsletter to see more of what's now possible.
WEB SITE DETAILS:
In the ACLAD Web Site you will find a listing of ACLAD's Scientific Seminars and other sponsored events at National AALAS in Anaheim, archived copies of the Newsletter, a list of contacts with expertise in different areas of laboratory animal disease research, some directions to diagnostic laboratories, a resource for obtaining funding for research (including pointers to downloadable copies of grant applications), and information about training programs in comparative pathology and laboratory animal medicine. A "What's your diagnosis" page has also been included as a demonstration of intent; ACLAD would greatly appreciate updated material for this section and all others that would be worthwhile for the membership. Please send your comments and suggestions about the web site to Ben Weigler (bweigler@.bart.rprc.washington.edu).
HAMSTER DISEASE OUTBREAK AT MICHIGAN STATE UNIVERSITY.
by Susan Stein, DVM, Dipl. ACLAM
University Laboratory Animal Resources
Michigan State University
East Lansing, Michigan 48824
E-Mail: 22723SS@msu.edu
Telephone: (517) 353-5064
Dear Colleagues,
I have submitted a description of a clinical/diagnostic dilemma we faced at MSU to the ACLAD Newsletter in hopes of receiving some suggestions. Any insights would be appreciated. What follows is a synopsis of problems that started in a closed colony of hamsters in January, 1996.
A unique colony of Wh/wh hamsters experienced a series of acute deaths in January of 1996. The animals ranged in age from 10 days to 6 months. The only clinical signs seen were slight depression and, in some cases, diarrhea. The animals had been housed in groups of 3. The colony was maintained under PI care. Initial management changes included:
1) Individually housing all hamsters except those with nursing litters.
2) Wearing latex gloves when changing cages.
3) Disinfecting gloves with Cidex wipes between cages.
4) Restricting access to the colony. (The researcher also had an MHV positive
mouse colony next door to the hamster room).
Freshly dead animals were submitted for necropsy. The first submission, a 6 month old male born in the colony, had a number of lesions. Sections of pancreas contained multifocal, coalescing areas of necrosis with minimal inflammatory cell infiltrate. Some of the remaining nuclei were filled with material suggestive of inclusion bodies. There were also areas of mild necrosis in the liver with mixed inflammatory cell infiltration. Additionally, the portal triads contained lymphocytes and plasma cells. Sections of both adrenal glands had multifocal areas of mild necrosis with predominantly neutrophilic infiltrate. Again, intranuclear inclusions - eosinophilic to amphophilic, were present in some areas. Areas of the kidney showed multifocal coalescing degeneration and necrosis of tubular epithelium. Hyaline and granular casts were present in many tubular lumens. Sections of skeletal muscle contained myofiber swelling and vacuolation. The pathologist comments suggested a viral etiology - especially a herpes virus. Bacteriologic examination of the tissues: Staphylococcus aureus, alpha hemolytic Streptococcus and Pasteurella species in low to moderate numbers.
An additional animal was submitted for evaluation - a 5 month old female. On histopathology, this animal appeared to have a multifocal acute ulcerative enterocolitis. Pasteurella species were isolated from the small intestine. Electron microscopy of sections of small intestine were negative for virus. At this time a serum sample from a male hamster related to this 5 month old female, was sent to Charles River Laboratories for serology. Results were negative for all routinely monitored hamster viruses. In the meantime, EM was done on sections of adrenal gland from the initial submission, the 6 month old male. There appeared to be virus-like particles in those sections. Attempts were also made to culture virus from tissue samples from the index case on BHK-21 cells. There were no isolates.
Samples - tissue and serum - were sent to Dr. Abigail Smith at Yale University. She tested the sera for LCMV, Hantaan virus, Seoul virus, mouse parvovirus, adenovirus, MHV, rat parvovirus, Theiler's VII and encephalomyocarditis virus. Attempts to isolate virus were made using BHK21 (baby hamster kidney) cells, C6 (rat glial) cells, Vero (African green monkey kidney) cells and Vero, clone E6, cells. Tissue samples were negative for LCMV, Morbillivirus, rabies, herpes simplex, paramyxovirus (Sendai), poxvirus, murine parvovirus, reovirus and cytomegalovirus. Two more hamsters from the colony - females appearing depressed - were submitted for necropsy. One female appeared to have lung consolidation suggestive of pneumonia. On histopathology from both animals, there was a disseminated necrotizing hepatitis. There was margination of nuclear chromatin and nuclear "vacuoles", suggestive of sequelae to a viral infection. There were also abnormal hepatocytes that appeared to contain amyloid like material. Additionally, there was a generalized lymphoid hyperplasia in many tissues. Renal lesions included proximal tubular necrosis and glomerulopathy with amyloid like deposits. The adrenal cortical tissue was necrotic with amyloid-like material present. A cardiomyopathy (occasional plump eosinophilic fibers) and some nuclear rowing and centralization of skeletal muscle were also noted. Unfortunately, the untimely death of the researcher resulted in euthanasia of the entire colony. Serum and liver tissue from these animals are available, along with embedded tissues from the first cases for recuts.
Diagnostic Exercise: Interstitial Pneumonia in Viral and Mycoplasmal Antibody-Free Sprague Dawley Rats
by Patricia L. Farrar, DVM, MS, Dipl. ACLAM, Department of Comparative
Medicine, Saint Louis University Health Sciences Center
and Marie LaRegina, DVM, MS, Dipl. ACLAM, Division of Comparative Medicine,
Washington University School of Medicine, St. Louis, Missouri
History: In the summer of 1996, pulmonary lesions were observed in asymptomatic young adult (180-220 gram) Sprague Dawley rats which were being used for the collection of pulmonary type II alveolar cells. Animals were obtained from a single facility of a commercial vendor, and kept for less than 2 weeks prior to terminal use. These rats were housed in open cages in a positive pressure cubicle in a small barrier unit located within a conventional research animal facility. Subsequently, in the fall and winter of 1996-1997, similar pulmonary lesions were sporadically observed in incoming vendor rats and in asymptomatic adult project and sentinel rats housed throughout the animal facility in a variety of husbandry conditions.
All rats housed within the animal facility were obtained from the same commercial vendor. Breeding sentinel rats were housed in open cages on the bottom row of each rack of animals throughout the facility. Dirty bedding from random cages was placed into the sentinel cages at every changing period, and a comprehensive health evaluation of the sentinel animals, consisting of serologic, microbiologic, parasitologic, and histopathologic evaluation, was completed at least biannually. Sentinel and project rats had been and have remained negative for all known adventitious viral, mycoplasmal, and bacterial pulmonary pathogens since lesions were first observed in the summer of 1996.
Pathology: Gross pulmonary lesions were observed in asymptomatic adult rats at necropsy. Scattered to multifocal, randomly distributed, variably sized, slightly raised, gray nodules were found throughout all lung lobes. Multiple pinpoint white foci were also unevenly distributed throughout the lungs. Microscopically, pulmonary lesions consisted of granulomatous alveolar and interstitial infiltrates, usually perivascular in location, which varied in severity. Mild lesions consisted of perivascular mononuclear cell infiltrates, adjacent to mild alveolar luminal and septal accumulations of activated macrophages, lymphocytes and scattered neutrophils (figures 1-2). In more extensive lesions, granulomatous infiltrate and necrotic debris filled the alveolar lumens, the alveolar septa were thickened with inflammatory cell infiltrates, and sporadic mild bronchiolitis was found (figures 3-4). Rarely, consolidation with obliteration of alveolar walls due to accumulation of inflammatory cells and debris occurred. Type II pneumocyte hyperplasia and occasional giant cells were observed in the more extensive lesions (figure 5). No significant histopathologic abnormalities were observed in other organs examined, including the trachea, Harderian glands, salivary glands, gastrointestinal tract, kidney, urinary bladder, heart and liver.
Diagnostic Evaluation: No bacterial, fungal or protozoal microorganisms were found in lung sections stained with Giemsa, periodic acid-Schiff, Gomori's methenamine silver, Masson's trichrome, tissue gram, acid fast, or a Dieterle silver stain. Examination of lung sections under polarizing light failed to reveal the presence of birefringent material in affected airways.
Extensive microbiologic culturing of lungs from affected animals failed to reveal the presence of common bacterial or fungal pathogens. Pulmonary samples were cultured for Paecilomyces spp., using a two step cultivation technique,1 and were negative. Serologic screening of sera from affected project and sentinel rats revealed no titers against Sendai virus, Mycoplasma spp., rat coronavirus, Kilham rat virus, parainfluenza 3 virus, or pneumonia virus of mice. Polymerase chain reaction testing of lung sections from two affected animals for the presence of Pneumocystis carinii was inconclusive, with one animal testing positive, and the other negative. Electron microscopic analysis of pulmonary tissue sections failed to reveal the presence of microorganisms in the lung. Viral isolation from affected lungs, using Rhesus monkey kidney, HEp-2, human embryonic lung fibroblast, and human neonatal kidney cell lines was attempted, with negative results for the presence of hemagglutinating, syncytial forming, or cytopathic viruses.
Extensive epidemiologic evaluation of lesion occurrence in animals revealed no apparent correlation with specific housing arrangements. Pulmonary lesions were sporadically observed in project and sentinel animals housed in open cages and in microisolator cages, in both negative and positive pressure rooms, on a variety of beddings, including corn cob, hardwood chips, and pressed paper product. Additionally, sera from a few affected animals was submitted for a hypersensitivity pneumonitis screen to look for precipitating antibodies against a panel of 10 common fungal allergens (thermophilic organisms), and was negative.
Age and vendor room of origin were variables which appeared to have some correlation with lesion occurrence. Lesions were most often observed in young adult (2-5 month old) animals of both sexes. Extensive histopathologic evaluation of weanling 3-week old sentinel and older adult rats have failed to reveal the presence of similar pulmonary lesions. Affected animals were obtained from a few select facilities of a major commercial vendor. Animals obtained from one facility of the same vendor have remained free of pulmonary lesions to date.
Questions: What is the histopathologic diagnosis for the lung lesions illustrated in figures 1-5? Based on histopathologic appearance and epidemiologic pattern, what are your differential diagnoses for the pulmonary lesions (i.e. infectious, toxic, allergic, metabolic)? What further diagnostic testing should be undertaken to rule in/out your differentials? If an infectious etiology is suspected, what class(es) of agents should be considered?
Discussion: The histopathologic diagnosis is mild to moderate, multifocal, granulomatous (nonsuppurative) interstitial pneumonia, with perivascular mononuclear cell aggregates and type II pneumocyte hyperplasia. Although the lesions are nonspecific in nature, differential diagnoses should include hypersensitivity (allergic) pneumonitis, viral pneumonia, and toxic damage.
Hypersensitivity pneumonitis is an acute or chronic reaction to inhaled allergens, such as thermophilic fungi, molds, and certain proteins, which can result in a patchy interstitial pneumonia in man2 and other animals.3 In man, lesions are composed primarily of lymphocytes, plasma cells, and macrophages and they are usually peribronchiolar in distribution. Naturally occurring hypersensitivy pneumonitis in animals has been reported in cattle and horses, where a lymphocytic and plasmacytic bronchitis and bronchiolitis predominates.
Toxic causes of interstitial pneumonia which have been reported to occur in animals include inhaled chemicals, inorganic dusts, ingested toxins or precursors, and endogenous metabolic/toxic conditions such as uremia, endotoxic shock, and disseminated intravascular coagulation.3 Histopathologic pattern of pulmonary response to toxins vary widely, depending on species affected and specific toxin present.
Historically, pneumonia in rats has been associated with mono- or dual infections with infectious agents such as Sendai virus, rat coronavirus, pneumonia virus of mice, Mycoplasma pneumoniae, Streptococcus pneumoniae, Corynebacterium kutscheri, Klebsiella pneumoniae, Pneumocystis carinii, and cilia-associated respiratory (CAR) bacillus.4-9 Aerogenously transmitted viruses, such as Sendai virus, are capable of causing bronchointerstitial pneumonia in many rodent species. Infection with Mycoplasma pulmonis, alone or in combination with other bacterial and/or viral agents, causes chronic bronchopneumonia in rats, characterized by lower and upper airway involvement and hyperplasia of bronchial-associated lymphoid tissue. Interstitial pneumonia without significant small airway (bronchiolar) involvement has rarely been reported in rats, but lesions similar to those observed here have been described in rats infected with pneumotropic strains of rat coronavirus4-6 and pneumonia virus of mice.7,9 Several incompletely characterized agents have also been associated with pneumonia in laboratory and/or wild rats, including enzootic bronchiectasis agent, gray lung virus, and wild rat pneumonia agent.5 A recently published abstract10 reports the appearance of granulomatous lung lesions, similar to those described here, in specific pathogen-free breeding colonies of laboratory rats. The authors reported that inoculation of mammalian cell cultures with tissues from affected rats produced cytopathic effects, and that sera from affected animals tested positive via an immunofluorescence assay with infected mammalian cell cultures, suggesting a novel virus in lung tissues of affected rats. The pulmonary lesions described in this report, although nonspecific in nature, are most suggestive of a hematogenously distributed viral infection, due to their perivascular distribution and lack of upper airway involvement.
Acknowledgements
The authors would like to thank the following individuals for their assistance
in the diagnostic evaluation of clinical specimens: Darryl Thake, Sanford
Feldman, Bruce Williams, Jeffery Dodds and William Shek.
Bibliography:
1. Fungus Paecilomyces: a new agent in laboratory animals. Kunstry I, Jelinek
F, Bitzenhofer U, et al. Laboratory Animals, 31:45-51, 1997.
2. Immunologic Lung Disease. In: Surgical Pathology of Non-neoplastic Lung
Disease, 2nd edition. Katzenstein AA and Askin FB, Eds. W.B. Saunders Co.
3. The Respiratory System. In: Pathology of Domestic Animals, Vol. 2. Jubb
KVF, Kennedy PC, and Palmer N, Eds., Academic Press, 1985.
4. Lung. In: Pathology of the Fischer Rat. Boorman GA, Eustis SL, Elwell
MR, et al, Eds. Academic Press, 1990.
5. Viral Diseases. Jacoby RO, Bhatt PN and Jonas AM. In: The Laboratory
Rat, Vol. 1. Baker HJ, Lindsey JR, & Weisbroth SH, Eds. Academic Press,
NY, 1979.
6. Rat Coronavirus Infection, Lung, Rat. Brownstein DG. In: Monographs on
Pathology of Laboratory Animals, Respiratory System. Jones TC, Mohr U, Hunt
RD, Eds. Springer-Verlag, 1985.
7. Pneumonia Virus of Mice Infection, Lung, Mouse and Rat. Brownstein DG.
In: Monographs on Pathology of Laboratory Animals, Respiratory System. Jones
TC, Mohr U, Hunt RD, Eds. Springer-Verlag, 1985.
8. Respiratory System. In: Infectious Diseases of Mice and Rats. Committee
on Infectious Diseases of Mice and Rats, ILAR, National Academy Press, 1991.
9. Rat. In: Pathology of Laboratory Rodents and Rabbits. Percy DH and Barthold
SW, Eds. Iowa State University Press, 1993.
10. Idiopathic Lung Lesions in Rats: Search for an Etiologic Agent. Riley
L, Purdy G, Dodds J, et al. Contemp. Topics in Lab. Anim. Sci.,36 (4), 1997.
Figures:
See the ACLAD Web Site for digitized images of these
pathology slides at…..
Figure 1. Lung, rat. H&E stain, 100X. Perivascular accumulation of mononuclear cells, adjacent to foci of mild alveolitis.
Figure 2. Lung, rat. H&E stain, 400X. Mild alveolitis, characterized by foamy macrophage and lymphocyte accumulations in the alveolar lumen, and alveolar septal thickening with inflammatory cells.
Figure 3. Lung, rat. H&E stain, 40X. Low power view of a subpleural foci of nonsuppurative interstitial pneumonia.
Figure 4. Lung, rat. H&E stain, 100X. Higher power view, showing extensive nonsuppurative interstitial pneumonia, with diffuse alveolar septal thickening and inflammatory cells in nearly all alveolar spaces.
Figure 5. Lung, rat. Toluidine blue stain, epoxy embedding, 200X. Thin section showing perivascular mononuclear cell aggregate adjacent to mild foci of granulomatous alveolitis. Note several alveoli contain increased numbers of alveolar type II cells (type II hyperplasia).
Rat parvovirus-1 (RPV-1): The prototype for a new rodent parvovirus serogroup.
by Lisa J. Ball-Goodrich, Stuart E. Leland, Elizabeth A. Johnson, Frank
X. Paturzo, and Robert O. Jacoby.
Section of Comparative Medicine, Yale University School of Medicine, New
Haven, CT
A newly recognized parvovirus of laboratory rats, designated RPV-1a, was found to be antigenically distinct. It was cloned, sequenced, and compared with the University of Massachusetts strain of rat virus (RV-Umass) and other autonomous parvoviruses. RPV-1a VP2 identity with these viruses never exceeded 65%, thus explaining its antigenic divergence. In addition, RPV-1a had reduced amino acid identity in NS coding regions (82%), reflecting phylogenetic divergence from rodent parvovirus. RPV-1a infection in rats had a predilection for endothelium and lymphoid tissues as previously reported for RV. Also like RV infection, infectious RPV-1a was isolated three weeks after inoculation of infant rats, suggesting that it may cause persistent infection. By contrast, RPV-1a was enterotropic, a characteristic previously associated with parvovirus infections of mice rather than rats. RPV-1a also differed from RV in that infection was non-pathogenic for infant rats under conditions where RV infection causes high morbidity and mortality. Thus, RPV-1a is the prototype virus of an antigenically, genetically, and biologically distinct rodent parvovirus serogroup.
Retrospective incidence of diagnostic syndromes in a scid mouse barrier colony (1993-1996)
by David Knudsen DVM, (Scotts Valley CA)
and Alison Pohl MS, MT(ASCP) (Palo Alto CA)
Successful use of C.B17 scid/scid (SCID) mice in long-term xenotransplantation
studies requires a high level of precaution and stringent barrier procedures.
Often as long 6 to 8 months, these studies present a challenge to the animal
care facility in maintaining the health and stability of animals with such
a profound immunologic defect. A major factor in this risk is the length
of experiment; increased time can also increase the possibility of contaminating
events. A restricted access barrier facility has been used to breed and
maintain a closed colony of SCID mice established in 1988. In this report,
diagnostic case records from this colony for the period July 1993 through
December 1996 are surveyed, and monthly case incidence rates are determined
for each diagnosis or infectious agent based on the number of diagnoses
made per month per 1000 mice.
Ongoing health surveillance programs were initiated in January 1993 and
continue to the present. Throughout this period, health surveillance has
emphasized the regular, complete examination of dedicated sentinel animals
including microbiology, serology, and histopathology of target tissues.
Additionally, pathologic evaluations are performed on all mice found sick
or dead in the colony. In addition to standard examinations, screening exams
for specific infectious agents such as Pneumocystis carinii 1 are also done
on SCID retired breeders and new animals planned for barrier introduction.
Finally, comprehensive environmental microbiologic surveillance of facilities,
equipment, sterilization and disinfection procedures, and automatic watering
is performed on a frequent schedule.
Most lymphoproliferative disease (LPD) noted in our colony during this
study was the classically described and common thymic tumor of SCID mice
2, featuring thymic enlargement and effacement by proliferating lymphocytic
cells with vascular spread to other viscera. About 5% of cases in our colony
have no thymic involvement but include hepatic and splenic infiltration;
these cases could reflect "normal" background cases of lymphoma
found in C.B17 mice. More rarely, human lymphoproliferative disease originating
in a human xenograft such as thymus was observed in less than 1% of cases.
The case incidence rate for LPD (table 1) has stayed quite stable in our
colony, with a low peak in incidence during 1995.
Plaque-like skin lesions were noted in association with LPD diagnosis
in some cases, which progressed toward skin ulceration and failure to heal
skin wounds. If sampled before ulceration develops, a narrow band of lymphocytic
infiltration could be seen beneath the basement membrane of the epidermis,
consistent with epitheliotropic lymphoma in other species 3. Case incidence
rates (table 1) for this syndrome decreased slightly after its first recognition,
as colony managers developed procedures for recognition and control.
An epizootic of skin lesions without associated LPD and progressing to
septicemia was first diagnosed in April 1994, as our colony was affected
by a virulent strain of Staphylococcus aureus which resulted in high morbidity
and moderate mortality within breeding and post-surgical groups, as has
been described for other immunodeficient mouse strains 4. Skin lesions featured
single or multiple coalescing foci of partial alopecia overlying mild to
moderate dermatitis. Inflamed zones either ulcerated quickly or did not
advance due to the severity and rapid advancement of other lesions. Other
characteristic lesions noted during the outbreak included perivascular and
peribronchiolar edema as well as intra-alveolar hemorrhage in the lung,
random piecemeal necrosis of hepatocytes, and intestinal ileus. The syndrome
was attributed to bacterial exotoxicosis following moderate stress at weaning,
surgery, and experimental manipulation. Control was effected by culling
of carrier breeding stock and therapeutic antibiotics for post-surgical
animals. Since the initial outbreak, the case incidence has dropped considerably,
although the isolate is still rarely encountered during sentinel examinations.
Fetal tissue used in engraftment studies (SCID-hu mice) is generally
contaminated at receipt with flora typical of human vaginal and epidermal
sites 5. Some of this flora, including ß-Streptococcus, E. coli, Staphylococcus
aureus, and Candida albicans can have serious health implications to the
host mouse following transplant. Depending with the pathogen, a variety
of syndromes were associated with contaminated transplants, including abscessation
at the surgical site, regional lymphadenopathy, peritonitis, septic emboli
leading to acute visceral inflammation, and septic shock. Inclusion of bacteriocidal
concentrations of antibiotics in shipping media during the procurement process,
plus penicillin treatment of tissues after receipt to suppress streptococci,
helped in reducing case incidence rates (table 1) of this syndrome over
the final 2 years.
Rectal prolapse was typically seen in group-housed male mice older than
4 months of age, although isolated cases were also observed in females and
younger males. While this syndrome has been classically associated with
helminth or protozoal infections 6, and the chronic inflammatory insult
and irritation they bring about, no pathogens or parasites have been detected
either in prolapse cases or in the colony as a whole. We hypothesize that
the syndrome may be related to hypertension in our colony, since a significant
number of male mice with rectal prolapse also had arterial medial hypertrophy
of the renal corticomedullary junction and intestinal submucosa, and a mild
cardiac ventricular hypertrophy. Case incidence of this syndrome (table
1) was very stable, arguing for a genetic basis in the colony. This colony
is free of recently described opportunistic pathogens such as Helicobacter
spp. which have been associated with rectal prolapse in normal mice. More
recently, and after the reporting period for this study, an increased number
of rectal prolapse cases within a group of SCID mice from an external supplier
has been associated with chronic Giardia muris infection.
Non-lymphoid tumors were noted in this SCID colony at a frequency typical
of closed mouse colonies without respect to the SCID trait. Over the 42
month period surveyed, mainly tumors of glandular tissues were observed.
These tumors of epithelial origin included: mammary adenocarcinoma (7 cases),
salivary adenocarcinoma (5), salivary cystadenoma (4), bronchiogenic adenoma
(4), and vaginal squamous cell carcinoma (1). Tumors of connective or multiple
tissue origin included: rhabdomyosarcoma (2), ocular leiomyoma (1), and
teratoma (1).
Cases of a novel neurologic syndrome were first recognized in 1994 associated
with posterior paresis, urinary and fecal incontinence, and inconsistent
proprioceptive deficits. Affected groups of animals had received tissue
from single fetal donors, and were clustered tightly; there was no transmission
between cagemates during infectious trials. Histologic examination revealed
severe diffuse demyelinization of ascending and descending tracts in the
thoracic and lumbar spinal cord, minimal to mild mononuclear cell participation
in the lesion, and prominent cytomegaly of oligodendrogliocytes within dorsal
root ganglia. Occasional foci of myelomalacia and hemorrhage were noted
within cranial white matter of acute cases. Amphiphilic, "ground-glass"
intranuclear inclusion bodies were present in some oligodendrogliocytes.
Due to the similarity of this lesion 7 to human progressive multifocal
leukoencephalopathy (PML), one possible etiologic agent of this syndrome
is a polyomavirus similar or identical to JC virus, the causative agent
of PML in immunosuppressed human patients. The incidence in SCID mice is
completely dependent on the use of a presumably infectious human tissue
sample for implantation. Because clusters of cases are associated with transplantation
with tissues from a single human donor, our hypothesis is that the associated
donor is viremic for JC or another polyomavirus at the time of tissues collection,
although attempts at viral isolation from the donor tissue have been futile
to this point. Another cause of SCID mouse spinal demyelinization, focal
spinal canal infiltration by lymphoproliferative cell populations, must
be differentiated from this syndrome.
Bibliography:
1. Walzer PW, Kim CK, Linke MJ, et al. Outbreaks of Pneumocystis carinii
pneumonia in colonies of immunodeficient mice. Infection and Immunity 1989;57:62-70
2. Dorshkind K. The severe combined immunodeficient (SCID) mouse. In Immunological
Disorders in Mice (Rihova B, Vetvicka V, eds.). CRC Press, Boca Raton, 1991;
pp. 1-21.
3. Lymphocytic tumors. In Veterinary Dermatopathology (Gross TL, Ihrke PJ,
Walder EJ). Mosby Yearbook, St. Louis, 1992; pp. 474-84.
4. Bradfield JF, Wagner JE, Boivin GP. Epizootic fatal dermatitis in athymic
nude mice due to Staphylococcus xylosus. Laboratory Animal Science 1993;43:111-3.
5. Pohl AD, Nicholas SL, Knudsen DEB. Bacterial and fungal contaminants
of human fetal tissue collected for research purposes. Transplantation (in
review).
6. Digestive system. In Infectious Diseases of Mice and Rats. National Academy
Press, Washington, 1991; pp. 85-163.
7. Infectious disease. In Fundamentals of Neuropathology (Okazaki H). Igaku-Shoin,
Tokyo, 1989; pp. 115-48.
Table 1: Case incidence rates for common diagnoses, closed SCID mouse colony (1993 - 1996) 1993 * 1994 1995 1996 Average monthly census, SCID colony 3971 8647 12283 8960 1) Lymphoproliferative disease - thymic center (LPD) Average number of diagnoses per month 6.2 12.6 23.1 12.7 Case incidence rate ** 1.56 1.46 1.88 1.42 2) Epitheliotropic lymphoma Average number of diagnoses per month ND † 1.4 0.9 0.8 Case incidence rate 0.16 0.07 0.09 3) Staphylococcal septicemia Average number of diagnoses per month 0 6.3 0.5 0.2 Case incidence rate 0.73 0.04 0.02 4) Contaminated human graft Average number of diagnoses per month 2.2 7.8 4.9 2.1 Case incidence rate 0.55 0.9 0.4 0.23 5) Prolapsed rectum Average number of diagnoses per month ND † 1.3 1.7 1.3 Case incidence rate 0.15 0.14 0.15 6) Non-lymphoid tumors Average number of diagnoses per month 0.8 0.9 1.3 0.6 Case incidence rate 0.20 0.10 0.11 0.07 7) Demyelinization syndrome Average number of diagnoses per month 0 1.5 1.2 1.5 Case incidence rate 0.17 0.10 0.17 * In 1993, only 6 months were considered (July through December) ** Case incidence rate = number of positive diagnoses / month / 1000 mice † ND = not determined; surveillance for this syndrome was not performed in 1993
Update on the Quality Assurance Program for Diagnostic Laboratories
by Karen Sokol
The Rockefeller University, New York, NY
The Quality Assurance Program (QAP), coordinated by the Rockefeller
University's, Laboratory Animal Research Center's Diagnostic Laboratory,
began in 1981 to provide a forum of communication for quality control
issues in the laboratory animal diagnostic arena. Participating
laboratories register annually and receive unknown samples on a quarterly
basis which includes two bacteriologic specimens (animal pathogens and
environmental samples) and one serologic specimen (only for mice and rats).
Results (including bacteriologic identification/antibiotic sensitivities
and serologic screens) are returned to the Rockefeller University for
tabulation, and data analyses with results summaries and discussion are
subsequently forwarded to the participants.
Currently, we have on our membership roster 28 participating laboratories
in the United States and 3 in Europe. One of our QAP participants in
Europe, Dr. Werner Nicklas, in Heidelberg Germany, receives our QAP
microbiologic samples and distributes them to approximately 20 additional
laboratories throughout Europe.
We think that the program has provided an important avenue of exchange
among our various diagnostic facilities. We feel that this exchange has
aided all of us in working toward a common goal in maintaining high
standards in diagnostics, and, ultimately, ensuring the proper care of our
research animals. We hope that the success of the past and the continued
interest from our current membership will help attract additional
laboratories to choose to be a part of this cooperative effort.
If you would like to receive a registration form for the 1998 membership,
please contact Dr. Karen Sokol at The Rockefeller University, Laboratory
Animal Research Center, 1230 York Ave. Box 2, New York, NY 10021,
Telephone: (212) 327-8534, FAX (212) 327-8536
E-mail: sokolk@rockvax.rockefeller.edu
ACLAD membership dues support ACLAD-sponsored programs at the National AALAS meeting
and underwrite the cost of reproducing and mailing the ACLAD Newsletter.
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