18 - Laboratory diagnosis of viral infections

Question 1

Give the pathway of viral infection

Answer 1

viruses obligatory cell parasites → cell damage (oncogenecity) → pathogen viruses → viral disease →← orphan viruses

Question 2

What is a prequisite of defense of viral infections

Answer 2

• Fast diagnosis
• Specific diagnosis

Question 3

In which cases is there need of specific laboratories?

Answer 3

1. Regulations of rules
   
   • Foot and mouth disease
   • African swine flu
   • BSE
2. Suspected zoonosis
   
   • Rabies
3. Eradication and control of free status
   
   • Leucosis (cattle)
   • IBR (cattle herpes)
4. Certifications:
   
   • Free status
   • Species pathogen free herd (SPF)
   • Transport
   • Competitions
5. Clinical signs, pathological findings are not sufficient to establish the diagnosis
6. Herd diagnosis: endemic viruses present in the herd

Question 4

Give the methods of laboratory diagnosis

Answer 4

• Direct virus demonstration:
  
  • Whole virus (isolation)
  • Its components (proteins, nucleic acis)
• Indirect process (virus serology)
  
  • Antibody detection from the infected animals

Question 5

What is the aim of laboratory diagnostics?

Answer 5

• To find:
  
  • The type of sample
  • Amount of sample
  • Shipping

Question 6

Aspects of the sample collection and transport

Answer 6

1. Sample type and timing of sampling
2. Unambiguous mark
3. Letter of basic information = accompanying letter
4. Period and circumstances of the sample’s shipping to a diagnostic institiute

Question 7

What should the accompanying letter include?

Answer 7

• A suitable case history together with the sample(s) NB!
• Name, address and contact details of the submitting veterinarian
• Name, address and contact detalis of the owner of the animal
• Personal data of the animal, of which the samples were taken:
  
  • Identification number or name of the individual animal
  • Age
  • Sex
  • Brief relevant vaccination history
• Case history at the individual animal level:
  
  • Time of disease onset
  • Symptoms
  • Course of the disease
• Case history at the herd level:
  
  • Time of disease onset in the herd
  • Symptoms
  • Course of the diesase
• Kind of submitted sample material:
  
  • Swab (conjuctival, nasal, pharyngeal, faecal…)
  • Blood (EDTA, heparinized, serum)
  • Organs: liver, spleen, lung, kidney
    
    • Depending on the suspected disease: heart, intesines, brain, placenta
• Suspected disease / request for lab testing

Question 8

What should the diagnostic labratory inform customers about?

Answer 8

• Each laboratory offering diagnostic services must anyhow have prepared a list, which must be available both as hardcopy and electronically on the website of the institution, displaying
• Diagnostic investigations done in this lab
• Type of test
• Price
• Kind of samples which should be taken and submitted to the lab
• Best way of submitting the samples to the lab
• Expected time frame of the investigation
• Propper interpretation of the results

Question 9

Sampling for virological investigation

Give the types of sampling for virological investigation

Answer 9

• Depending on the suspected disease, thus a propper case history is crucal

1. Direct method (in early phase):
   
   • _​_Corpse, organ, tissue (cadaver)
   • Secretion:
     
     • Ventricle (thorax)
     • Organ (udder)
   • Blood anticoagulat treated (leucocyte separation)
2. Indirect method (generally in late phase):
   
   • _​_Blood coagulated, serum
   • Milk, liquor
   • Ventricle and organ secretion

• Herd diagnosis: statistical sample collection
• Individual diagnosis: paired sera (in early and late phase)

Question 10

Sampling for virological investigation

Give the categorization in case the suspected pathogen is not completely clear

Answer 10

1. Respiratory symptoms​
2. gastroenteric symptomos
3. Neurological symptoms
4. Vesicular and skin disease
5. Abortion

1. Respiratory symptoms:

• Animal alive:
  
  • Conjuctival- and nasal swabs (some cases also pharyngeal swabs)
  • EDTA-blood
• Animal dead:
  
  • Lung
  • Liver
  • Spleen
  • Kidney

2. Gastroenteric symptoms:

• Animal alive:
  
  • Faeces or faecal swabs
  • (EDTA-blood)
• Animal dead:
  
  • Intestine
  • In addition: lung, liver, spleen, kidney

3. Neurological symptoms:

• Animal alive:
  
  • EDTA-blood
  • Conjuctival- and nasal swabs
  • (Cerebrospinal fluid)
• Animal dead:
  
  • Different parts of the brain and spinal cord
  • In addition: lung, liver, spleen, kidney

4. Vesicular and skin diseases:

• Vesicular fluid, vesicular wall (epithelial)
• Biopsia, swab
• Removed lesions (papilloma, sarcoid)

5. Abortion:

• fetus or organs
• Placenta, amniotic sac
• Blood of the dam

Question 11

Shipping

Answer 11

• As fast as possible: courier or personally, NEVER BY MAIL!
• Arrivial within 24 hours (depends on the type of sample)
• Temperature: usually +4ºC (ice cooler)
• Appropriate wrapping
• Accurate address