Equine viral resp infection contin

Question 1

Equine Viral Arteritis

• what happens
• virus genome
• why notifiable?

Answer 1

EVA
NOTIFIABLE!!!!
•	Arteritis - inflammation of arteries
•	Ateriviridae - Enveloped single stranded RNA virus
Why Notifiable: causes abortion in mares

Question 2

How does a horse get equine viral arteritis?

Answer 2

IN brood mares
o Carried by asymptomatic carrier stallions and mares bred in last 14 days
o Pass in semen during covering
o Because of abortogenic effects
o Both stallions and mares are tested for EVA before bred
o Causes arteritis – vascular inflammation of endothelium, damaging placenta

Question 3

African Horse sickness

Answer 3

• Not seen in UK
Spread by midges
• Insect borne (Arbovirus) virus
o Culicoides imicola  midges that don’t currently occur in Europe
o Control of AHS, concentrates on midge control
• Dog / Zebra /Elephant reservoir hosts which are asymptomatic
• 8 major strains
o Antigenically distinct
• 42 sub strains which produce different degrees of disease
o Some antigenic cross over

Question 4

PAthogenesis African horse sickness

Answer 4

• Vasculitis: the main damaging effect of AHS
o Severe vascular endothelial damage
• Respiratory / cardiovascular systems
• Leakage of protein rich fluid into interstitium
• Prominent oedema as endothelial leaks fluid – this is the most devastating part
o Lungs
o Thorax
o Pericardium
o Head

Question 5

Different types of african horse sickness

Answer 5

1.	Pulmonary Form – most fatal
•	Rapidly fatal (1 – 4 days)
2.	Cardiac Form
•	Course 2 – 5 days
3.	Mixed form
•	Rapid death usually
4.	Horse Sickness Fever
•	Mild “flu-like” syndrome

Question 6

Talk about pulmonary form of African Horse Sickness

Answer 6

• Febrile (severe)
• Pulmonary oedema in all areas – overloaded with fluid
o Particularly pulmonary oedema – alveolar fill with fluid, no longer able to exchange gas with blood hypoxemic
o Cough
o Profuse nasal discharge (serous or serum-like) with postural flow
- sweating
- cyanosis as can’t exchange gas
- recumbent
- death (less than 4 hrs to 4 days)
- good appetite until dies

Question 7

What is the characteristic sign of african horse sickness, pulmonary form

Answer 7

(most severe)
• Characteristic sign = pink froth at nose (also seen end stage cardiac failure and also during acute and severe URT obstruction. E.g. foreign body or larynx paralysed e.g. liver disease or mass = so much negative pressure across lungs to draw air into lungs, sucks fluid out of blood causing PO

Question 8

Talk about african horse sickness cardiac form

Answer 8

• Insidious onset with persistent fever
• Oedema of head and neck (Dikop)
• Congested mucous membranes (petechiation)
• Mild colic – oedema around intestine
• Dysphagia (pharyngeal / esophageal paralysis)
• Hydropericardium (cardiac tamponade)
• Slow death (>50%)
• Some cases survive but take a long time to recover (>1 year)
• Appetite remains good!
• Pericardial effusion of fluid leaking out of vessels
• Oedematous of conjunctiva (pink bit on eye below) Bulging supraorbital fossa

Question 9

Talk about african horse sickness, mixed form

Answer 9

•	Various combinations
o	cardiac and pulmonary forms
•	Rapid deterioration
o	Few milder cases
o	Horse Sickness Fever like syndrome
•	Death common