Viral skin disease Flashcards
What properties of the skin help prevent infection by viruses?
- dense layer of keratin (physical barrier)
- low pH, presence of fatty acids (hostile environment)
- innate and adaptive immunity
What are the disadvantages of skin if the viruses can overcome the barrier?
- rapidly dividing cells
- lots of blood vessels and lymphatics
- nerves
How do viruses overcome the barrier?
- trauma/ abrasions (e.g. poxviruses)
- arthropods
- as mechanical vectors (e.g. equine infectious anaemia)
- or true arboviruses (e.g. Bluetongue virus)
- animal bites (rabies)
- iatrogenic (e.g. eartags)
Describe the mechanism in which a virus (e.g. FMDV) shows clinical signs in the skin
- skin: invasion, multiplication
- regional lymph node, multiplication
- blood stream: primary viremia
- spleen and liver: multiplication, necrosis
- blood stream: secondary viremia
- skin: focal infection, multiplication
How is rabies spread?
- spread through neurons, moves from peripheral NS to CNS
What is this?
What are the properties of papillomaviruses?
- small
- non enveloped
- not easily disinfected by organic detergents
- survives low pH and high temps
- ds DNA - genome is infectious
How does the papillomavirus form a wart?
- needs actively dividing cells in basal squamous epithelial layer
- leads to virus induced hyperplasia
- virus shed with keratinocytes
What is a wart?
- benign neoplasms that usually regress spontaneously
How do some specific papillomaviruses progress to malignancy?
- virus genome is integrated into the host DNA
- thus the host cell is transformed (malignant transformation)
- site of integration is random
- viral oncogenes (E6 and E7) remain intact, and interact with cellular proteins such as tumour suppressor gene p53
Give examples of papillomaviruses that progress to malignancy
- bovine papillomavirus 4
- bovine papillomavirus 7
What species are warts most common in?
- cattle
How are warts normally transmitted in cattle?
- by fomites e.g. headcollars
How many types of wart are recognised in cattle?
- 10
How do the warts form in cattle?
- hyperplasia and hyperkeratinisation 4-6 wks after exposure
- raised plaques
- proliferating epidermis
- pedunculated masses
- usually regress spontaneously 1-6 months
- in combo with Bracken fern, they can cause carcinoma in alimentary and urinary tracts (enzootic haematuria)
What is the most common skin tumour in horses and at what age is it most common?
- sarcoids
- most common in horses under 4
Where are sarcoids mostly found and why are they a problem?
- head, ventral abdomen, limbs
- locally aggressive but not malignant
What virus are sarcoids associated with?
- bovine papillomavirus types 1/2
- BUT - unaffected horses can also have BPV DNA in the skin
What papillomas are mostly found in young dogs? When do they regress?
- oral papillomas in young dogs
- regress - 8 weeks
- progressio to squamous cell carcinoma rarely
What diagnostic techniques can be used?
- PCR - used to detect papillomavirus DNA and determine what virus is involved
- immunohistochemistry (presence of virus in lesion)
- histopathology
What are some treatment options for warts?
- autogenous vaccination
- surgical debulking
- sarcoids:
- surgery, radiation, topical drugs
- immunotherapy (BCG, anti-BPV vaccines)
What disease causes mortality in young captive psittacine birds?
- budgerigar fledging disease
- associated with French molt
