Asfarviridae Flashcards
Describe African swine fever (ASF).
OIE List A Disease
1. Etiology
-sole member of family Asfarviridae
-only known DNA arbovirus
2. Host
-all breeds & types of dom pig & euro wild boar
-inapparent inf in warthogs, bush pigs, giant forest hogs = reservoirs
3. Geographic distribution
-endemic in most of sub Saharan Africa & island of Sardinia (Italy)
*recent outbreak in east Europe & Russia & virus cont to spread in Russian federation
Describe ASF virus stability.
-survive 30d in pens & chilled carcass
-resistant to wide range of pH & putrefaction
-viable for long periods in blood, feces, tissue (uncooked or undercooked pork)
-multiply in vectors
Describe ASF & hemadsorption (HAD).
-virus doesn’t hemagglutinate
-pig erythrocyte adhere to surface of pig monocyte or inf macs
-hemadsorption (HAD) = attributed to virus specific protein that appears on plasma membrane of inf cells during late inf
Describe ASF transmission.
-biological vector: soft ticks (ornithodoros sp, specifically o. Moubata in Africa) ***
-virus rep in tick -> trans stadial, transovarial, & sexual transmission (M-to-F)
-inf ticks live for several yrs & transmit virus to pig during each blood meal
Describe the sylvatic cycle of ASF.
-between warthogs & soft ticks
-asymp inf in wild pigs
-after primary inf young wild pigs develop viremia w high virus titer to inf ticks
-older wild pig persistently inf but rarely develop viremia
Describe the domestic cycle of ASF.
In domestic swine from:
-bite of inf tick
-direct contact w inf animal (oronasal spread)
-indirect contact on fomites
-virus spread to new area when pig fed uncooked scraps that have inf pork
-aerosol
-mech transmission thru biting flies
*all body fluid & tissues contain lg amounts of inf virus
*pigs survive inf become carriers & shed virus in secretions & excretions
Describe the pathogenesis of ASF.
*effects of ASF primarily hemorrhage & apoptosis
*leukopenia, lymphopenia, thrombocytopenia
1. Apoptosis of host cells
-p54 protein (encoded by virus) induces apoptosis
-ASF inf macs release cytokines & apoptotic mediators
-apoptosis of lymphocytes & mononuclear phagocytic cells
2. Mechanism related to hemorrhages
-vascular damage from degen of vascular endothelium
-DIC
-inf & necrosis of megakaryocytes
-activation & destruction of monocytes & macs
-thrombocytopenia & coagulation defect lead to -> edema, infarction, exudation, hemorrhage in organ & tissues
Describe the clinical signs of ASF.
- Peracute
-pigs die suddenly - Acute
-fever
-cyanosis skin blotching on ears, tail, lower leg, hams*
>white skinned pigs the ears, tail, legs, underside are deeply flushed & have bluish tinge
-respiratory distress
-diarrhea = mucoid -> bloody
-abortion = first event seen in outbreak
-death - Chronic
-emaciation & stunting
-swollen joints
-ulcers & red or raised necrotic skin foci (cutaneous lesion)
-pneumonia
*enlarged friable spleen [blackberry jam spleen]
Describe ASF immunity.
-inf pigs make virus specific antibodies but sera from inf pigs dont neutralize virus -> humoral IR doesnt have protection
-vaccine developments unsuccessful
Describe ASF prevention.
-pig farmers & field personnel be aware of ASF & recog & know what to do if they sus ASF
-pigs kept in well constructed pig sties under hygienic condition w controlled entry to piggery
-movement of pig inside country & esp across international border controlled
-pigs shouldn’t be fed swill that have pig remains -> should be boiled for 30min & cooled before feeding
Describe what to do when theres an ASF outbreak.
NOTIFY AUTHORITY (ANIMAL HEALTH DEP)
-inf & sus inf farms = quarantine
-no movement of pigs or prod of pig origin
-all inf & in contact pig = slaughtered
-carcass burnt or buried deep on site
-vehicles disinf when entering & leaving farms
-personnel ensure shoes, clothes, equipment = disinf between farms
