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General procedures in virology

General procedures in virology. Lab 1. Rationale for Specific Diagnosis. Diseases in which the management of the animal or its prognosis is influenced by the diagnosis Certification of freedom from specific infections Artificial insemination, embryo transfer, and blood transfusion Zoonoses

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General procedures in virology

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  1. General procedures in virology Lab 1

  2. Rationale for Specific Diagnosis • Diseases in which the management of the animal or its prognosis is influenced by the diagnosis • Certification of freedom from specific infections • Artificial insemination, embryo transfer, and blood transfusion • Zoonoses • Epidemiologic and economic awareness • Test and removal programs • Prevention of new, emerging, and re-emerging viral diseases of animals

  3. Equipment required for collection of virus samples • (A) Sterile forceps, scissors, and scalpels. • (B) Selection of sterile swabs. • (C) Vials containing virus transport medium (with antibiotics) for collection of samples for virus isolation or identification. • (D) Bottles for collection of faeces, blood, and othersamples that do not require virus transport medium. • (E) Bottles containing formalin for tissues to be examined by histology. • (F) Blood collection equipment without additive for serum, with anticoagulant for virus isolation. • (G) Notebook and equipment for labelling specimens. • (H) Swabs and sterile containers for bacteriological investigation. • (J) Cool box. • (K) Heavy-duty plastic bags for post-mortem material.

  4. Specimens Appropriate for Laboratory Diagnosis • Respiratory: Nasal or throat swab; nasopharyngeal aspirate • Enteric: Faeces • Genital: Genital swab • Eye: Conjunctival swab • Skin: Vesicle swab or scraping; biopsy of solid lesion • Central nervous system: Cerebrospinal fluid • Systemic infections: blood leukocytes (buffy coat)

  5. Sample collection • The best timing for collecting the sample is as soon as possible after the animal first develops clinical signs because virus is usually present in maximum amount at about this time then falls away. • The portal of entry and the primary site of viral replication should be sampled. • Immediately after collection a plain cotton swab should be kept in a small screw-capped container containing virus transport medium. • Specimens intended for virus isolation must always be kept cold. • If specimens are being shipped or processed later, they should be kept in dry ice. • Specimens are properly labelled and submission form is filled.

  6. Initial Processing in the Laboratory • For inoculation into cell culture, swabs are shaken in fluid medium, faeces are dispersed in fluid medium, and tissue specimens are homogenized in a high-speed blender. • Cell debris and bacteria are deposited by low speed centrifugation, after which the supernatant is usually passed through a 0.45μm syringe-top membrane filter to remove remaining non-viral contaminating organisms. • Some of the original sample and of the filtrate is retained at 4°C or frozen at -70°C at least until virus isolation attempts are completed. • The filtrate is inoculated into cell cultures and/or sometimes into chick embryos or newborn mice. • Clinical specimens processed in this way are generally suitable for detection of viral antigens/DNA/RNA by in vitro tests

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