Presentation on theme: "Dept. of Medical Microbiology University of Sulaimani Sulaimani, KRG 24 th February, 2015."— Presentation transcript:
Dept. of Medical Microbiology University of Sulaimani Sulaimani, KRG 24 th February, 2015
Introduction of virology Introduction of virology Laboratory diagnosis of viral infection Laboratory diagnosis of viral infection Specimen collection and transport Specimen collection and transport Diagnostic Technique (rapid test) Diagnostic Technique (rapid test)
Virology: Study of viruses Viruses: are obligatory intracellular parasites. It is composed of nucleic acid surrounded by a protein shell and/or a lipid layer.
Why are viruses important to vet? Viruses cause disease in animals of economic and/or welfare importance. Animal viruses may pose risk to human health (zoonosis). Can act as important models for human disease.
Virus particles can only be observed by an electron microscope 20nm- 400nm Spherical Rod-shaped Brick-shaped Tadpole-shaped Bullet-shaped Filament - Virus particles exhibit 3 types of capsid symmetry: 1.helical - tubular: (eg. measles) 2.icosahedral - cubic; enveloped (e.g. herpes) or not enveloped (eg. adenovirus) 3.complex - (e.g. vaccinia)
Laboratory Diagnosis of Viral Infections Includes: Specimen collection Transport specimen Specimen processing and inoculation in system of living cell Virus identification Note: Normal viral microflora doesn’t exist!
1. Specimen collection Rules or Principle of successful viral sampling 1.At the correct time (stage of infection) 2.From the correct site (site of infection) 3.In the correct way 4.In the adequate volume (for all tests needed) 5.In the proper containers (sterile and chemically clean) 6.Correctly labelled (name, date, type of specimen) and with (age, sex, epidemiological data – vaccinations, etc.)
2. Transport specimen During transport specimen should be: 1.protected from breaking 2.protected from light 3.At adequate temperature: -48 hrs at +4°C (refrigerator, wet ice) -more than 48 hrs at -70°C (dry ice) NOTE// must not be frozen at -20°C!
Transport specimen * Viral Transport Media (VTM): (VTM) contains: -buffer (adequate pH) -saline (adequate ion concentration) - proteins (albumin or gelatine) - antibiotics and fungicides (VTM) is used to: Preserve viral infectivity within the specimen Prevent specimen from drying Stop the growth of bacteria and fungi * MEM, Hank’s solution, Stuart’s * EDTA, Sodium citrate, heparin for (blood).....
Common types of Specimen Collection Specimen is taken from the viral lesion by: Swab from the lesion Aspiration from vesicles o Both placed in a(container with VTM)
Swabs For diagnosis of viral infections; Swabs should be: made of rayon Should not be made of cotton or calcium alginate Swab’s shaft should be: made of plastics or metal Should not be made of wood Swab from the lesion with rotation & place in (test-tube with VTM)
Tissue Biopsy or Autopsy Tissue samples collection: (Tissue Biopsy or Autopsy) 1.Sterile instruments should be used. 2.Collect 3 x 5 mm and placed in tube with VTM Storage In the refrigerator (2 – 6.0° C) for up to one week. Can be stored frozen (≤ -70.0 ° C) indefinitely.
Blood (Serum) sample Whole Blood (serum) Collected by venipuncture or venal catheter (5-7 ml) Place in a sterile tube (with EDTA, Sodium- citrate or heparin) Allow 15 minutes to clot to form. By Centrifuge (serum) Or by storing the whole blood sample, overnight in the refrigerator (2– 6.0° C). (plasma) Urine, CSF, or other fluids can be used for diagnosis of viral infection Note// Sputum is not useful for viral detection
Diagnostic Techniques Rapid Test (Line immunoassay) A typical test strip consists of: 1.Sample pad - an adsorbent pad to test sample is applied. 2.Conjugate or reagent pad – antibodies specific to the target analyte conjugated to colored particles 3.Reaction membrane – cellulose acetate membrane--- a test line and a control line 4.Wick or waste pad– absorbent pad ----- draw the sample ---by capillary action and collect it