common infectious diseases in laboratory rats and mice
DESCRIPTION
COMMON INFECTIOUS DISEASES IN LABORATORY RATS AND MICE. What’s common?. Helicobacter spp. – 15% C. bovis – 3% Pneumocystis carinii – 2% Pinworms – Mouse – 0.3% Rat – 1.3% Mites – 0.1% (mice only). MHV – 2% Parvoviruses Mouse – 2% Rat – 4% EDIM – 0.7% Norovirus ~30% RRV – 7%. - PowerPoint PPT PresentationTRANSCRIPT
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COMMON INFECTIOUS DISEASES IN LABORATORY RATS AND MICE
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What’s common?
•MHV – 2%
•Parvoviruses
•Mouse – 2%
•Rat – 4%
•EDIM – 0.7%
•Norovirus ~30%
•RRV – 7%
•Helicobacter Helicobacter spp. – spp. – 15%15%
•C. bovis – 3%C. bovis – 3%
•Pneumocystis carinii – Pneumocystis carinii – 2%2%
•Pinworms – Pinworms – Mouse – 0.3%Mouse – 0.3%Rat – 1.3%Rat – 1.3%
•Mites – 0.1% (mice Mites – 0.1% (mice only) only)
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What’s common in mice?Agent Assay # tested # pos. % pos.
Parv NS-1 ELISA 445,255 8,481 1.9048%
MPV ELISA 457,062 8,974 1.9634%
MVM ELISA 458,931 1,789 0.3898%
MHV ELISA 441,098 7,949 1.8021%
EDIM ELISA 364,793 2,459 0.6741%
GDVII ELISA 342,312 991 0.2895%
MPUL ELISA 352,563 32 0.0091%
REO ELISA 338,054 43 0.0127%
SENDAI ELISA 361,118 10 0.0028%
PVM ELISA 353,043 12 0.0034%
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What’s common in rats?
Agent Assay # tested # pos. % pos.
RPV ELISA 73,289 1,324 1.8065%
H-1 ELISA 67,594 1,128 1.6688%
KRV ELISA 73,400 1,136 1.5477%
RMV ELISA 29,110 437 1.5012%
GDVII ELISA 28,203 264 0.9361%
SDAV ELISA 68,445 159 0.2323%
MPUL ELISA 67,951 127 0.1869%
M pulmonis Culture 3,558 2 0.0562%
PVM ELISA 66,450 98 0.1475%
SENDAI ELISA 67,193 16 0.0238%
REO ELISA 61,016 5 0.0082%
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Mouse Hepatitis Virus(MHV)
Coronavirus, ss RNA, envelopedVery high evolutionary capacity (innumerable
strains)Prevalence moderateVirus types grouped as enterotropic
(intestinal) or polytropic (multiple tissue) – most field strains are enterotropic
Clinical signs very rare in immunocompetent mice after weaning
Wasting syndrome in many immunodeficient mice
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MHV
As enveloped virus – does not persist in environment. Probably not infective after 48 hrs.
Short-term transfer by fomites (sleeves, equipment, bedding)
Highly contagious and can spread rapidly
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Enterotropic MHV
Strains: D, RI, Y, G, myriad others .Most wild type strains are enterotropicClinical signs and gross lesions rare in
immunocompetent adult micePrimary replication:
GI tract, especially distal ileum, cecum, ascending colonSecondary sites - uncommonClearance mediated by B cells
Not cleared in μMT mice (anecdotally also in many GM lines)
Dissemination prevented by T cellsDisseminates in TCR βδ- , IFN-γ - , RAG1, athymic nude
mice
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Research Impact of MHV
Prolonged immunologic effects:NK cells, T-cells, B-cellsInfects monocytes, macrophages, bone marrow dendritic cellsDelayed allogeneic graft rejection
Alters course of concurrent infections, such as Helicobacter hepaticus
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MHV Detection
Serology
Excellent cross-reaction among strains
MFIA or ELISA, with IFA for confirmation
Seroconversion within 2 weeks (often one week)
Histopathology
Lesions should by confirmed by IHC, PCR or serology
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MHV Diagnosis
PCR
Sequencing of PCR product (nucleocapsid gene) for epidemiology
Fecal Shedding (quarantine, immunodeficient mice)
Environmental
Confirmation of serology by PCR of mesenteric lymph nodes
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CONTROL OF MHVImmunocompetent mice self-cure
Enveloped virus: not stable in environment, easy to disinfect
Can eliminate from immunocompetent colonies by not breeding and no new mice for 6-8 weeks (test 1st)
Infection persists in immunodeficient mice
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Are you Are you gettinggetting mixed signals on mixed signals on
parvoviruses?parvoviruses?
Parvoviruses
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Parvoviruses in Mice
ssDNA, non-enveloped
Virus remains active in environment
Resistant to desiccation and many (non-oxidizing) disinfectants
Fairly common
Generally no clinical signs
Cause persistent infection – no self-cure
Need actively dividing cells to replicate
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Parvoviruses of Mice
Mice Minute Virus (MMV or MVM) Multiple strains (i, p, c, m), MMVm is most prevalent and is persistent. Others are
culture-adapted strains.MMVm reported to cause stunting, low reproduction and early deaths in NOD μ-chain KO
mice .
Experimentally, caused hronic progressive infection in scid mice.
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Research Effects of MMV
Cell culture Can infect many mouse cell lines, as well as some rat
embryo lines and transformed human cells (324K, EL-4)
ImmunityIn vitro reduction of T-cell response by MMVi and in
vivo late reduction of cytotoxic memory cells by MMVp
CytoskeletonIn vitro (A9 cells) dysregulation of gelsolin (↑) and
WASP (↓) by MMVp
Tumor studiesMMVp is oncotropic and oncolytic in some human
tumors (hemangiosarcoma) and mouse tumors
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Parvoviruses of Mice
Mouse Parvovirus (MPV-1, MPV-2, MPV-3, MPV-4) Prevalence higher than MMVCauses persistent infectionNo anatomic lesions, even in scid miceDifferent strains not very cross-reactive by ELISA,
MFIA
C57BL/6 mice and congenic strains partially resistant to infection
C57BL/6 mice require 10-100x infective doseDBA/2 only slightly better
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Research Effects of MPV
MPV-1a (cell culture adapted) modulates immune response (McKisic et al, 1996)
Suppression of T cell response in vitroCD8+ T lymphocyte clones lose function and viability
Cytokine- and antigen-induced T cell proliferation in vitro suppressed after exposure to MPV-1a
Potentiates allograft rejection in vivo
GEM expressing B19 NS1 have altered immune system and high fetal mortality resembling non-immune hydrops fetalis
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Detection of Parvoviruses
Serology – Usually best for screeningMFIA or ELISA - Traditional or recombinant antigens
Use panel of antigens for each serotype, plus the generic NS-1 antigenMice - MMV, MPV-1, MPV-2, and NS-1
Rats - RV, H-1, RPV, RMV and NS-1
IFA – Good follow-up assay for positive/equivocal MFIA/ELISA
Be careful with MPV serology of C57BL/6 mice!
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Detection of Mouse Parvoviruses
PCR
Can be strain-specific (VP2) or generic (NS-1)
Mesenteric LN stay positive indefinitely
Pooled fecal samples to detect shedding (Beware of fecal inhibitors of PCR)
Biologicals and cell cultures
Environmental swabs
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Detection of Mouse Parvoviruses
Many Challenges (sentinel parvovirus)
Some strains partially resistant (C57BL/6, DBA/2)
Not all mice may seroconvert to all antigens (NS-1)
May have very low prevalence in IVC and filter-top caging (hard to sort out from false positives)
Seroconversion generally within 7 days, but may be slow in adults exposed to low infectious dose
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Control of Parvoviruses
Can not “burn out” because infection is persistentCan only eliminate by rederivation
If caesarian section, must carefully test offspring and foster dams. Primaparous dams more likely to be
viremic.Reported as detected from sperm and pre-implantation
embryosNo envelope, so it stays active in environment
Must thoroughly disinfect environment, materials and equipment with oxidizing agent (Clidox, ozone, etc.)
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Exclusion of Parvoviruses
Consider sources of research animals:Vendors, GM animals, immunodeficient
Wild rodentsBiological materialsRisk from personnel handling infected rodents (pets, snake food)Fomites (Feed, bedding, water, used/shared equipment etc.)
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NorovirusesType virus is Norwalk virus, “cruise ship
virus”Non-enveloped, RNA
Cause >90% nonbacterial epidemic gastroenteritis worldwide, 23M cases/yr in
US (per CDC)
Cruise ships, institutions, military
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Noroviruses
MNV
Genetically distinct (genogroup V) from human noroviruses (I, II, IV), zoonotic spread unlikely
No evidence of clinical disease or lesions in immunocompetent mice
No noroviruses yet reported in other lab rodents
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MNV-1
No disease in immunocompetent mice
High mortality in RAG (-/-) STAT (-/-)double KO mice, with disseminated infection and encephalitis and pneumonia
Encephalitis only with IC inoculation
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MNV
Many variants isolated at this point, > 50 at CRL
MNV widespread in lab mouse research facilities
No clinical disease reported in natural infections
Most major vendors (including CRL) reporting all colonies negative for MNV by serology
and/or PCR
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MNV
Research interference unknown, but:MNV-1 was detected in macrophage-like cells in vivo and grew in vitro in
dendritic cells and macrophages. Growth was inhibited by the interferon αβ receptor and by STAT-1 (Wobus et al., 2004)
Possible macrophage aggregates in RAG livers
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MNV
Diagnosis:MFIA/ELISA – recombinant capsid protein self-assembles into VLP. Good cross-
reaction among variants
PCR – Virus shed in feces for long periods, should persist in environment. PCR must be properly designed to be able to detect multiple strains .
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MNV
Management
Virus probably present in mice for a long time (so no hurry)
Nonpathogenic
Widely distributed
Numerous strains
Noroviruses should not cross placenta, so c-section or ET rederivation should be successful
Must consider environmental decontamination