Lecture 1 - DNA and RNA Viruses

What is the structure of virus is the Herpesvirus?

Doublestranded DNA and enveloped

What advantage does an envelope offer a virus?

Improved entry into host cell

What disadvantage does an envelope offer a virus?

Makes it less durable to survive in the environment

How does herpesvirus spread?

Respiratory secrections, nose to nose contact, aerosols over short distances

Where does herpesvirus replicate in a horse?

nasal and respiratory epithelium as well as endothelial cells

What are some clinical signs of herpesvirus in horses?

vasculitis of the CNS, vascular damage that can lead to thrombosis, focal areas of ischemia necrosis in CNS

What allows the herpesvirus to remain hidden for long periods of time?

latency

What diagnostic clues help us conclude an infection is herpesvirus?

PCR tests from nasal swabs or whole blood and intranuclear inclusions

Describe the structure of parvovirus?

Small, single strand DNA virus, non enveloped

What advantages are there to not having a lipid envelope?

more durability to the environment

What cells does parvovirus target for spread in the body?

mucosal surfaces, where it then spreads via lymphocytes

How do we diagnose parvovirus?

PCR, snap test, virus isolation or serology (hemagglutination inhibition test, not used much anymore)

What does parvovirus do?

Damages the gut by destroying intestinal crypts and epithelium

Why is contact time for disinfectant important for parvovirus?

Non-enveloped viruses are very durable

What is the structure of papilloma virus?

Circular, double stranded DNA, non enveloped

What does papilloma virus do?

Targets basal epithelial cells, stimulates cellular proliferation which creates papillomas

What is a potential consequence of papilloma virus in cows?

Interaction with some plants can cause cancerous neoplasia

What is the structure of poxvirus?

large, complex doublestranded DNA

What is unique about pox virus?

Most DNA viruses replicate in teh nucleus, pox virus replicates in the cytoplasm

What is especially important when dealing with pox virus? Why?

PPE, it is zoonotic

What are diagnostic clues for pox virus?

Cytoplasmic inclusions, characteristic skin lesions, zoonotic

Virus characteristics

small, simple, obligate parasties

How do viruses replicate?

Viruses use host cell machinery to replciate vis DNA or RNA

Characteristics of DNA viruses

Low mutation rates and relatively more durable when compared to RNA

Characteristics of RNA viruses

RNA is less durable and has higher mutation rates

Integrates into human genome

Retrovirus

Has many hosts, symptoms range from enteric, respiratory and neurologic (or a combination of some),

Coronavirus

HPAI is one example, influenza as a whole infects wide ranges of species, ssRNA, negative sense

Orthomyxovirus

enveloped, helical, single stranded, negative sense RNA, bullet shaped

Rhabdovirus

A retrovirus that presents with fever, anorexia, non healing wounds and skin, gi or respiratory signs

FeLV

Three immune responses to FeLV

abortive (good), regressive (moderate) and progressive (poor)

Which strain of FeLV is horizontally infectious?

Strain A

What ability allows rapid mutation in FeLV?

Recombination

What can eventually become FIP? Why?

Feline enteric coronavirus, through mutation that allows the virus to leave enterocytes

What are the two types of FIP?

Effusive (bloated belly) or non-effusive (swollen eyes)

Total reassortment of genome creating a new virus

antigenic shift

accumulation of mutations over time, eventually evolving into a new virus

antigenic drift

Requirements for antigenic shift

sympatry, ecology, coinfection, packaging, replication compatibility, fitness

Rabies is apart of what genus?

Lyssavirus

What is a predominant reservoir host for rabies in the US?

Skunks

Common transmission of rabies

Bite, mucuous membrane or broken skin exposure

Hallmark sign of rabies in pathology

Negri bodies in neurons