獸醫傳染病學題庫下載題庫

Background: Pneumonia virus of mice (PVM) is anvirus affecting the respiratory tracts of rats andnmice. It is a ssRNA virus of the familynParamyxoviridae.n

Transmission: PVM is transmitted via aerosol andncontact exposure to the respiratory tract.nSusceptibility is strain dependent and can benincreased by a variety of local and systemicnstressors.n

Clinical Signs: In immunocompetent rats andnmice, the infections are short-lived, withoutnclinical signs. No pathologic lesions have beennreported in naturally infected rats and mice. Noncarrier state develops.nIn immunocompromised mice, such asnathym...

Background: Pneumonia virus of mice (PVM) is anvirus affecting the respiratory tracts of rats andnmice. It is a ssRNA virus of the familynParamyxoviridae.n

Transmission: PVM is transmitted via aerosol andncontact exposure to the respiratory tract.nSusceptibility is strain dependent and can benincreased by a variety of local and systemicnstressors.n

Clinical Signs: In immunocompetent rats andnmice, the infections are short-lived, withoutnclinical signs. No pathologic lesions have beennreported in naturally infected rats and mice. Noncarrier state develops.nIn immunocompromised mice, such asnathymic nudes, chronic pneumonia with wastingnoccurs. This infection is fatal.nMild rhinitis and interstitial pneumonia hasnbeen reported after experimental infections ofnimmunocompetent mice. Persistent interstitialnpneumonia was reported in experimentallyninfected athymic nude mice.n

Diagnosis: Diagnosis is usually based onnserology, via ELISA or IFA or both.nEffects on Research: PVM infections in immunocompromisednmice, such as athymic nudes, arenfatal and should be avoided.nIn immunocompetent mice, PVM can alternthe pulmonary architecture and induce a strong,nmeasurable immunological response. This canninterfere with immunological and toxicologicalnstudies and measurements of pulmonary cellnkinetics and metabolism.n

Prevention: To prevent this disease, obtainnreplacement stocks from sources that are knownnto be free of disease. Tumor lines should benassessed for infection using MAP tests or othernappropriate tests.nStrict traffic patterns should be established tonensure that virus is not introduced into colonies ofnimmunocompromised animals. Personnelnworking with infected animals should not enternrooms that contain naïve or immunocompromisednanimals.nAll animals should be placed in microisolatorncaging environments that are handled with thenaid of a laminar flow hood using sterilentechniques during handling and observation ofnthe animals.n

Eradication: The most effective way to eradicatenSV infections is to cull the colony and obtainnclean replacement stock. However, this is notnalways a feasible option when working withnvaluable mice.nCaesarian rederivation or embryo transferncan be used to produce offspring that have notnbeen exposed to the virus. Repeated serologicalnevaluations should be performed prior tonreintroduction of the mice into a naïve population.nA breeding moratorium of at least 8 weeksncan also be used to prevent the spread of thenvirus from young weanling animals to youngernnaïve animals. The animals should be housed innmicroisolator caging and handled with standardnmicroisolator techniques. This method requiresnrepeated serologic testing and strict adherence tona zero-tolerance for breeding policy. It isnimportant to note that transgenic and knockoutnmice often have altered immune systems thatnmay allow them to sustain the infection for longernperiods of time or to develop a carrier state. It isnalso unclear if immunocompromised micendevelop a persistent infection. In these cases, thenbreeding moratorium would not be thenappropriate means of eradication.