Poxviruses Flashcards
What is smallpox caused by?
- Variola major (an Orthopoxvirus)
What is the mortality rate of smallpox?
- 30%
What are survivors of poxvirus left with?
- scarring
- blindness
- joint issues
When did Dr. Edward Jenner form the first vaccine and how?
- 1796
- noticed milk maids were not getting small pox
- the cows had blisters on their udders
- he took some of the blisters and injected it into a child
- child was immune
When was the last known case of smallpox? and when was it declared eradictaed by WHO?
- last known- somalia 1977
- eradicated- 1980
What are the features of the pox virus? label
- ds DNA virus
- complex structure
- large genome- encodes lots of proteins
- enveloped
Why is it an advantage that poxvirus species share many genetic and antigenic features?
- if you find a vaccine for one, can use for other species (cross protection)
How do poxviruses replicate within cells?
- replicates in the cytoplasm in viral factories (vacuoles in the cell)- work happily with all of their own enzymes. will then expel virions from the cell
What happens if you remove the nucleus?
- the virus can still replicate but the virions cant mature to become infective
Using cell machinery, the poxvirus produces proteins which:
- inhibit host innate immune responses
- blocks internal cell signalling, and prevents cell sending messages to say help
- switches off host complement cascade (reduces inflam)
- steal some of the host cell membrane to hide itself, so can leave cell and infect others unnoticed
- stops cell undergoing apoptosis
How does transmission of poxvirus occur?
- contacts of infectious material with broken skin (not intact skin)
- some species also via aerosol, or mechanical (insects)
Poxviruses are epitheliotrophic. What does this mean?
- infect keratinocytes of skin (sometimes mucosae)
- some poxvirus infections can become systemic
What happens to a cell when it is infected?
- it balloons and will then pop
Label
- inclusion body and cell ballooning
What are these arrows pointing to?
Put these in order (order of pox lesions)
- f
- b
- d
- c
- a
- e
Which animals dont really get poxviruses?
- dogs
- horses
What are the general clinical signs of poxviruses?
- skin lesions most common (vesicles, nodules)
- fever
- lymoh node enlargment
- sometimes systemic (resp/ GIT infection)
Where does Monkeypox normally occur?
- central and W Africa
What are the clinical signs of monkeypox?
- pox skin lesions
- flu like symptons in humans
What is the mortality rate of monkeypox and from which animal is it normally transmitted?
- 1-10% (milder)
- transmitted from animals (rodents primary source, sometimes primates)
What is Cowpox? Which animals act as a reservoir?
- only rarely affects cows (pustules on teats)
- wild rodents act as reservoir
What happens when a cat gets cowpox?
- usually from rodents
- pox skin lesions
- can affect liver/ lungs
- can be fatal (rare)
What is Vaccinia?
- closely related to Variola (smallpox) and cowpox
- used as vaccines during smallpox eradication campaign
- name derived from vacca
- natural host species unknown
What was the original purpose of Myxomatosis? Why is there a difference between infection in S.America and Europe?
- was introduced as a form of number control in rabbits
- natural hosts are rabbits in S.America and Cali, causing benign cutaneous swelling
- European infection
- swelling of head/ anogenital regions
- blepharoconjunctivitus develops
- transmitted by mosquitos/ fleas
- Why?
- virus has co-evolved to not kill host in America
What is Orf?
- poxvirus
- worldwide
- sheep/ goats
- contagious pustular dermatitis
- cutaneous disease
- pox lesions on mouth and lips
- persists in scab material in environment
WHat does this sheep have?
- orf
What are the 3 capripoviruses (CPPV) and what are their mortalities?
What CPPVs are found in these areas?
How can you diagnose poxvirus?
- samplying fluid from vesicles provides a lot of virus to test for (10^7 particles per ml/fluid)
- can then test using;
- PCR + sequencing
- electron microscopy
- ELISA
How do you control poxviruses?
- vaccines
- isolation
- good hygiene
- parasite control (lice, swinepox)
Why was smallpox eradicated?
- no reservoirs in other species
- no carrier states
- no re-infection
- vaccine is nearly 100% effective
- vaccine is robust
- smallpox easy to recognise
- global effort
Why is monkeypox more difficult to eradicate?
- has reservoirs in other species
