introduction to african swine fever...1 introduction to african swine fever daniel beltran alcrudo...
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Introduction to African swine fever
Daniel Beltran Alcrudo
Animal Health OfficerRegional Office for Europe and Central AsiaFAO
Key features
• High lethality
• Huge losses (livelihoods, production, trade)
• Very difficult to control once established
• Spreads through infected meat
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There are no vaccine or a treatment against ASF
• In Africa, ASF naturally circulates in wild suids that show no clinical signs.
• Domestic pigs of all ages and gender
• Feral pigs and wild boar equally susceptible
• Humans are NOT susceptible
• Ornithodoros ticks are the other true reservoir
The host
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The virus• A unique, enveloped, cytoplasmic, double-
stranded DNA arbovirus
• Resistant virus to a wide range of T and PH
• Resistant in meat and the environment
One serotype, but > 20
genotypes with
numerous subgroups
Variability of a segment
in a single gene used
for phylogenetic
purposes. Nothing to
do with the virulence
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ITEM ASF SURVIVALSmoked meat 30 daysSalted meat 182 daysDried meat 300 days
ITEM ASF SURVIVALChilled meat 110 daysSkin/Fat (even dried) 300 daysFrozen meat 1,000 days
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However... ITEM ASFV SURVIVAL TIMECooked meat (minimum of 30 minutes at 70oC) 0 daysCanned meat 0 days
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Obvious implications for the
epidemiology and disease control
Stable in carcases (dead
animals) for 3-5 weeks
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ITEM ASF SURVIVALBlood >90 daysFeces at room temperature 11 daysPutrified blood 15 weeksContaminated pig pens 1 month
How to destroy ASF virus?
Heat (70°C, 30 min)
Sunlight
Appropriate disinfectants for ASF:
• 2% caustic soda (sodium hydrate)
• Detergents and phenol substitutes
• Sodium or calcium hypochlorite (2-3%)
• Iodine compounds
Cleaning before disinfection!
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Clinical presentation
• Clinical signs highly variable– Depending on virus virulence, breed, route of exposure, infectious dose
– Sometimes only fever and death, or unspecific signs
– Presentation in the field not identical to experimental cases
• Within-herd spread may vary greatly
How do pigs/wild boar get infected?
• Direct contact with sick animals or infected blood
• Mating
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How do pigs/wild boar get infected?
• Feeding on garbage (scavenging/free-roaming)
• Swill feeding
• Scavenging on carcasses
How do pigs get infected?
• Soft ticks (Ornithodoros)
• Other mechanical vectors?
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How do pigs get infected?
• Contaminated fomites (vehicles, clothes,…). Infected fodder?
How do pigs get infected?
• Iatrogenic
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How do pigs NOT get infected?
• Aerosol
• Water, i.e. lakes or rivers
• Mechanical vectors (?)
IT IS ALL ABOUT HUMAN BEHAVIOUR!
Direct contact (free-range pigs)
Scavenging carrion/waste
Manure and other fomites
Direct contact
Scavenging carrion/waste
Fomites
Direct contact (including transport
for management purposes)
Scavenging carrion
Swill Feeding
Direct contact (free-range pigs)
Scavenging carrion/waste
Through hunters (?)
2-3
weeks
Sylvatic Cycle Domestic Cycle Wild Boar Cycle
Infected tick
drops from the
warthog
In the burrow
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The importance of pig and pork value chains
• High within-country variability
• High seasonality
• Highly dynamic in response to the markets, e.g. an ASF epidemic
• Many unknowns
BUT UNDERSTANDING THEM WELL IS KEY FOR PREVENTION
Key epidemiological characteristics
• Despite what textbooks say, ASF is not a highly contagious disease – BUT it is highly lethal
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FMD
Prevalence: 100%
Mortality: 2%
Lethality: 2%
Contagiousity: +++
CSF
P: 50%
M: 25%
L: 50%
Contagiousity: ++
ASF
P: 10%
M: 9%
L: 90%
Contagiousity: +
100 infected; 2 dead
50 infected; 25 dead10 infected; 9 dead
Infected dead
Slide by K. Depner
Key epidemiological characteristics
• Despite what textbooks say, ASF is not a highly contagious disease
• ASF usually presents itself in waves
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The 4 phases of a transmissible disease
Epidemic
EndemicIntroduction
Invasion
Fade out
Slide by K. Depner
Key epidemiological characteristics
• Despite what textbooks say, ASF is not a highly contagious disease
• ASF usually presents itself in waves
• Strong seasonality
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Unpredictable behavior as ASF spreadsASF Africa• 1910s-Today• Multiple genotypes• Sylvatic cycle• Tick-Pig cycle• Mostly domestic
cycle (as waves)
ASF in Iberian Peninsula• 1960s-90s• Genotype I• Pig cycle• Tick-Free range pigs
challenging• Finally controlled
ASF jumps (Europe & Caribbean)• 1960s-1980s• Genotype I• Domestic cycle• Fast control
(sometimes extreme measures)
ASF in Sardinia• 1970s-Today• Genotype I• Domestic cycle,
(illegal free-range)• Spill-over in wild
boar
ASF in ex-USSR- 2007-Today- Genotype II- Pig cycle- Spill over in wild
boar, sometimes for long periods
ASF in Baltics & Central Europe- 2012-Today- Endemic in wild
boar- Slow spread- Sporadic outbreaks
in pigs
ASF in Romania- 2018- Genotype II- Bushfire-like spread
in pigs- Few wild boar
affected
China- 2018- Genotype II- Only domestic
pigs??
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Clinical presentation
Peracute ASF Acute ASF Subacute ASF Chronic ASF
Fever High High Moderate Irregular or absent
Thrombocytopenia Absent Absent or slight (late) Transient Absent
Skin Erythema Erythema Erythema Necrotic areas
Lymph nodes -Gastrohepatic and renal with marbled
aspect
The majority of lymph nodes resemble a blood
clotSwollen
Spleen - Hyperaemic splenomegaly
Partial hyperaemic splenomegaly or focal
infarctionEnlarged with normal
colour
Kidney -Petechial
haemorrhages, mainly in cortex
Petechial haemorrhages in
cortex, medulla and pelvis; peri-renal
oedema
-
Lung - Severe alveolar oedema - Pleuritis and
pneumonia
Gall bladder - Petechial haemorrhages Wall oedema -
Heart -Haemorrhages in epicardium and endocardium
Haemorrhages in epicardium and endocardium;
hydropericardiumFibrinous pericarditis
Tonsils - - - Necrotic foci
Reproductive alteration - - Abortion Abortion
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Clinical signs
• Generally characterized by the sudden death of pigs
• All ages and both genders may be affected
• Wild boar shows the same clinical signs
Peracute
– high fever (41-42 °C)
– loss of appetite and inactivity
– Sudden death within 1-3 days before any clinical sign.
– Often, no apparent clinical signs nor lesions in organs
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Acute (1)
• After 4-7 days incubation period (seldom, up to 14 days)
• Fever of 40-42 °C
• Lack of appetite
• Increased respiratory rate.
• Death within 6-9 days for highly virulent strains, or 11-15 days for moderately virulent isolates.
• Lethality up to 90-100 %
• Ocular and nasal discharge;
• Sleepy and weak, lie down and huddle
• Carcasses in good body condition
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Acute (2)
• Infected pigs may show one or several of the following signs:
– constipation or diarrhoea, which may progress to bloody
– vomiting
– abortion at all stages of pregnancy;
– haemorrhagic lesions, reddening, cyanosis…
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Cyanosis (bluing) at the tips of ears.
Necrotic lesions on skin of the abdomen, neck and ears
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Bloody froth from the nose and mouth
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Acute form in wild boar – Clinical signs
• Same signs in wild boar and feral pigs.
• Colour changes and haemorrhages in the skin easily missed in due to darker skin and thick hair.
• The same applies to dark-skinned pig breeds.
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Acute form – Mot typical post-mortem findings
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Haemorrhagic and enlarged gastrohepatic and renal lymph
nodes. Non-diseased tissue is a healthy white/pink colour
without inflammation.
Spleen often enlarged, friable (fragile) and shows signs of infarction (dark area).
Healthy spleens are uniformly coloured (red-brown) and textured.
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Kidneys with notable petechiation on the cortex.
Healthy renal tissue is a uniformly coloured light brown without any surface
irregularities.
Bloody froth from the nose/mouth and a discharge from the eyes
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Haemorraghic heart
Haemorraghic bladder
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Haemorraghic stomach
Haemorraghic
intestines
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Haemorraghic liver (and other
serosal surfaces)
Pulmonary oedema and consolidation of lung tissue
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Excess fluid around
the heart and in body
cavities.
How about post-mortem findings in wild boar?
Exactly the same!
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Haemorrhagic gastrohepatic lymph node
Haemorrhagic kidney
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Petechiation on the kidney’s cortex
Spleen enlarged
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CSF
Erysipelas
PDNS
Salmonellosis
ErysipelasPRRS
Thanks for your attention