9/10: Viruses Flashcards
Infectious challenges (24 cards)
what is a virus?
small infectious agent that only replicates inside the living cell of another organism
how large is a virus in comparison to a bacterium?
1/100th of a bacterium
whta is another name for avian influenza?
bird flu
what is avian influenza caused by?
> 130 subtypes of nfluenza A virus in wild birds
name types of avian influenza
- highly pathogenic avian influenza (HPAI)
- low pathogenic avian influenza (LPAI)
-> LPAI subtypes include H5 and H7, which have the ability to mutate to HPAI after circulation in poultry population
which type of AI do wild birds carry vs domestic poultry?
wild birds: carry low pathogenis virus
domestic poultry: more susceptible to HPAI; H5N1
how is AI introduced to poultry farms by wild birds?
- direct contact
- biological secretions such as faeces
- contaminated water + feed
how is AI spread within + between farms?
- direct contact
- contaminated equipment, vehicles, people
- faeces
- air transmission over shorter distances
- bird markets
what are clinical signs of AI in birds?
- swollen head
- dullness
- low egg production
- loss of appetite
- sudden death
what are mild symptoms of AI in humans?
- fever
- sore throat
- cough
- headache
- muscle pain and aching
what are sever symptoms of AI in humans?
- high fever
- chest infection
- respiratory failure
- multi-organ failure
- death
how does AI attack the host?
- virus enters and replicates
- travels to lungs + triggers immune system
- cytokines sent to attack virus
-> cause deadly inflammation: blood and fluid leak into air sacs - host “drowns” in its own blood
-> virus tricks immune system
how to prevent a pandemic caused by AI?
- problem must be stopped at a farm and animal level
- assistance to less resourced countries:
-> improve vet services
-> implement control strategies, e.g. culling + vaccination
-> increase bio-security through hygiene
how is H5N1 surveyed?
WHO monitors human cases; world org. for animal health (OIE) + FAO collect reports on bird + other animal outbreaks
what are methods of control of AI?
eradication; UK animals must be slaughtered; movement controls and strict sanitary measures must be adopted; vaccination programmes used in some programmes
what are advantages of vaccination against AI in birds?
- stops use of more unethical measures
- greater stocking densities w short life cycles
- protects against infectious diseases
- economic benefits due to less losses
what are disadvantages of against AI in birds?
- difficult to distinguish between vaccinated + infected and vaccinated + non-infected animals
- vaccinated animals cant be exported
- loss of disease-free status
- vaccinated animals are still carriers
what are antiviral drugs humans can take against AI? what are potential disadvantages?
- Oseltamivir (Tamiflu)
- zanamivir (relenza)
-> used for prevention + treatment - H5N1 can be resistant to tamiflu
- only a small amount can be produced
- most effective when take within 48h of symptoms
what is foot and mouth disease?
- acute infectious disease caused by a virus
- affects all cloven-hoofed animals, e.g. cattle, pigs, and sheep
what are clinical signs of FMD?
fever, dullness, shivering, slavering (excessive saliva), anxiety, loss of appetite, loss of condition, reduced milk yield, tenderness of feet, lameness, blisters
where is FMD present?
largest quantity of the virus in blister fluid, also present in saliva, milk, dung
how is FMD spread? directly/indirectly
direct: contact w infected animals
indirect: contamination w lorries, clothing, feed, water or containers
what are means of control of FMD?
- infected herds/flocks slaughtered within 24h
- contiguous cull: any animals in contact w carriers are slaughtered
-> issues: not enough man-power, little expertise for identification
why did the epidemic cost the UK Treasury £8 billion?
cost of
- compensation
- disease eradication
- employment of vets and army?
- loss of tourists and other industries?
