african swine fever 2006 african swine fever texas a&m university texas a&m university...

African Swine Fever 2006African Swine Fever 2006

African Swine Fever African Swine Fever

Texas A&M University Texas A&M University

College of Veterinary MedicineCollege of Veterinary Medicine

Jeffrey Musser, DVM, PhD, DABVPJeffrey Musser, DVM, PhD, DABVP

Suzanne Burnham, DVMSuzanne Burnham, DVM


Special thanks to:Special thanks to:

M. van Vuuren, Dept. of Veterinary Tropical Diseases, Faculty of Veterinary Science University of Pretoria

Corrie Brown, DVM, PhD Department of Veterinary Pathology College of Veterinary Medicine University of Georgia

Tom McKenna, DVM, PhD USDA, “Swine Fevers” Colorado State FEAD Course Aug. 1-5, 2005

Plum Island Animal Disease Center, Kathy Appicelli, Photographer


African Swine FeverAfrican Swine Fever




is a tick-borne, contagious, is a tick-borne, contagious, febrile, systemic viral febrile, systemic viral disease of swinedisease of swine

http://www.iah.bbsrc.ac.uk/images/Asfvirus.gif



Highly contagious viral disease of domestic pigs Highly contagious viral disease of domestic pigs with up to 100% mortalitywith up to 100% mortalityPigs die as a result of a hemorrhagic feverPigs die as a result of a hemorrhagic fever


Some pigs may Some pigs may develop subacute or develop subacute or chronic forms of the chronic forms of the diseasedisease

Control depends on Control depends on the slaughter and the slaughter and destruction of all destruction of all infected and in-contact infected and in-contact pigspigs


There is no vaccine for There is no vaccine for



Disease reported present

Disease reported absent

Data unavailable or incomplete

African Swine FeverAfrican Swine Fever Is a serious transboundary animal disease Is a serious transboundary animal disease

with the potential for rapid international spreadwith the potential for rapid international spread

World Distribution in 2004



EtiologyEtiology

Host rangeHost range

Incubation Incubation

Clinical signsClinical signs

TransmissionTransmission

Diagnosis Diagnosis

Differential DiagnosisDifferential Diagnosis


Etiology Etiology

The ASF virus is theThe ASF virus is theonly member of the genus only member of the genus asfivirus in the family asfivirus in the family Asfarviridae*.Asfarviridae*.

Large (~ 200 nm) Large (~ 200 nm) lipoprotein-enveloped, lipoprotein-enveloped, icosahedral, icosahedral, double- stranded DNA virusdouble- stranded DNA virus

ASFV is the only DNA virus ASFV is the only DNA virus that can qualify as an that can qualify as an arbovirus. arbovirus.

* “ASFAR”AfricanSwineFeverAndRelated viruses


ASFV is a large, dsDNA, enveloped virus recently classified in the new family Asfarviridae

Rare example of a DNA arthropod-borne virus

The stability of the virus is a notable feature:

Infectivity is retained after 15 weeks in chilled meat, and for 5-6 months in processed hams

Etiology


Strain Virulence

Marked variations in virulence of isolates:

- Highly virulent - 10-100 % mortality by 7-10 days after exposure;

- Moderately virulent - Acute illness, a high % of pigs survive;

- Low virulence - Seroconversion only.


Environmental Persistence

Stable at pH 4-13Stable at pH 4-13

Survives at least:Survives at least:- 11 days in feces (room temp)- 11 days in feces (room temp)

- 1 month in soiled pig pens- 1 month in soiled pig pens

- 70 days in blood on wooden boards- 70 days in blood on wooden boards

- 15 weeks in putrefied blood - 15 weeks in putrefied blood

- 18 months in blood at 4- 18 months in blood at 4ooCC


Environmental Persistence

Survival in pork productsSurvival in pork products::

15 weeks in chilled meats15 weeks in chilled meats

300 days in cured hams (“Parma hams”)300 days in cured hams (“Parma hams”)

15 years in frozen carcasses15 years in frozen carcasses


Host RangeHost Range

Ornithodoros Ornithodoros ticks are believed to be ticks are believed to be the original hostthe original host



Soft ticksSoft ticks- - Ornithodorus erraticusOrnithodorus erraticus from ASF-infected from ASF-infected farms.farms.- - Ornithodorus porcinusOrnithodorus porcinus porcinus (moubata) porcinus (moubata) from from

warthog burrows. warthog burrows.- - OrnithodorusOrnithodorus ticks in Haiti, Dominican Republicticks in Haiti, Dominican Republic and California. and California.



ASFV is believed to be a tick virus with ASFV is believed to be a tick virus with domestic pigs and wild pigs as accidental domestic pigs and wild pigs as accidental hosts. hosts.



AfricanAfrican

Domestic pigsDomestic pigs



In Africa:In Africa:WarthogsWarthogs

Bush pigsBush pigs

Giant forest hogsGiant forest hogs

In EuropeIn Europe::

Wild pigsWild pigs

http://www.cruisersafaris.com/images/trophy/warthog_tf.jpg



European wild boarEuropean wild boar

African wild swineAfrican wild swine - Wart hog- Wart hog - Giant forest hog - Giant forest hog - Bush pig - Bush pig



NOTE –NOTE –Collared peccary Collared peccary notnot susceptible susceptible

White collared peccary “Javelina”


Incubation PeriodIncubation Period

Following intranasal-oral exposure, Following intranasal-oral exposure,

pigs develop fever and leukopenia pigs develop fever and leukopenia

in 48 to 72 hoursin 48 to 72 hours


Incubation PeriodIncubation Period

5 days or less after 5 days or less after infection by tick bite.infection by tick bite.

5-15 days after 5-15 days after contact with contact with ASFV-infectedASFV-infected

pigs. pigs.

..

Argasid tick bites on pig ear.



Morbidity:High morbidity — usually 100% in pigs that have contact with one another; 100% in naïve pigs

Mortality:Highly virulent isolates have about 100% mortalityModerately virulent isolates range from low percentage to 60-70%.


Morbidity and MortalityMorbidity and Mortality

Age Age

Pregnancy status Pregnancy status

Other diseases have effect Other diseases have effect


General Clinical SignsGeneral Clinical Signs

HOT, SICK, RED pigsHOT, SICK, RED pigs



In contrast to pigs with In contrast to pigs with hog cholera:hog cholera:– African Swine Fever pigs African Swine Fever pigs

do notdo not develop develop conjunctivitis or conjunctivitis or encephalitis encephalitis

– Despite high fever, ASF Despite high fever, ASF infected pigs stay in good infected pigs stay in good condition, whereas hog condition, whereas hog cholera infected pigs cholera infected pigs drastically lose weightdrastically lose weight


Some groups of pigs Some groups of pigs may develop diarrhea, may develop diarrhea, but it is not a direct but it is not a direct effect of the virus.effect of the virus. Pigs may also develop Pigs may also develop dark red to purple dark red to purple discoloration of skin on discoloration of skin on ears, tail, extremities, or ears, tail, extremities, or skin on hams. skin on hams. (This is a (This is a nonspecific sign also seen in other nonspecific sign also seen in other diseases)diseases)

http://www.spc.int/rahs/Manual/images/asf-03.jpg



AbortionAbortion

Occurs whether isolates are high, Occurs whether isolates are high, moderate or low in virulence.moderate or low in virulence.

- Fetuses may be anasarcous.- Fetuses may be anasarcous.

- May find petechiae in placenta, skin, and- May find petechiae in placenta, skin, and myocardium, and a mottled liver. myocardium, and a mottled liver.


Clinical SignsClinical Signs

Coagulopathy, abnormal clottingCoagulopathy, abnormal clotting

ThrombocytopeniaThrombocytopenia

HemorrhagesHemorrhages

Sudden death in peracuteSudden death in peracute

High fever, low appetite, huddling, shallow High fever, low appetite, huddling, shallow breathing, reluctant to movebreathing, reluctant to move


Clinical Signs Clinical Signs

These signs are influenced by the These signs are influenced by the virulence and the physiological state virulence and the physiological state (age, pregnancy status)(age, pregnancy status)

There are three categories:There are three categories:Highly Virulent IsolateHighly Virulent Isolate

Moderately Virulent IsolateModerately Virulent Isolate

Low-Virulent IsolateLow-Virulent Isolate


Clinical Signs: Clinical Signs: High and ModerateHigh and Moderate

Similar for first 4-6 DPI (days post infection)Similar for first 4-6 DPI (days post infection) After about 2 DPI, pigs develop:After about 2 DPI, pigs develop:

1. Fever of 105-1071. Fever of 105-107°F°F

2. Moderate anorexia 2. Moderate anorexia

3. Leukopenia 3. Leukopenia

After 4-6 DPI, differences related to different After 4-6 DPI, differences related to different isolates will be apparentisolates will be apparent


Clinical Signs: Clinical Signs: High and ModerateHigh and Moderate

.

White skinned pigs will

have erythematous skin.

If left alone, pigs will lie down


Clinical Signs: Clinical Signs: Highly VirulentHighly Virulent

Pigs eat and move lessPigs eat and move less

Most die between 7 and 10 Most die between 7 and 10 DPI.DPI.

It is not unusual to see It is not unusual to see

a pig walking and find a pig walking and find

it dead a short time laterit dead a short time laterhttp://www.defra.gov.uk/animalh/diseases/images/v2/asfn_8.jpg



PeracutePeracute - - Sudden deathSudden death

AcuteAcute- - Fever (105-Fever (105-107107ooF) – F) –

-Discolored skin -Discolored skin - Huddling- Huddling- Diarrhea /- Diarrhea / melena melena- Abortions- Abortions- Death- Death


Clincal Signs:Clincal Signs: Peracute or acute diseasePeracute or acute disease



HuddlingHuddling



Erythema of skin:


Clinical Signs:Clinical Signs:Acute/ PeracuteAcute/ Peracute


Clinical Signs: Clinical Signs: Moderately VirulentModerately Virulent

Infected pigs usually have high fever for 10 to Infected pigs usually have high fever for 10 to 12 DPI. Some mortality occurs at this time.12 DPI. Some mortality occurs at this time.

After 12 to 14 DPI, temperatures and After 12 to 14 DPI, temperatures and leukocyte count begins to return to normal leukocyte count begins to return to normal levels. levels.


Clinical Signs: Clinical Signs: Moderately VirulentModerately Virulent

Very young pigs may have high mortality rate Very young pigs may have high mortality rate and lesions similar to those caused by highly and lesions similar to those caused by highly virulent isolates virulent isolates


Clinical Signs: Clinical Signs: Moderately Virulent Moderately Virulent

Some pigs will die at 7 to 8 Some pigs will die at 7 to 8 DPI, frequently caused DPI, frequently caused by hemorrhage into the by hemorrhage into the stomachstomach

Underlying causes: ASF Underlying causes: ASF infection causes infection causes prolonged bleeding timeprolonged bleeding time


Clinical Signs: Clinical Signs: Low-VirulenceLow-Virulence

Other low-virulent isolates will cause pigs to Other low-virulent isolates will cause pigs to have low fever for 2 to 3 weeks, then develop have low fever for 2 to 3 weeks, then develop reddened areas of skin that become raised reddened areas of skin that become raised and necrotic. and necrotic.

Painless enlargements of joints may also Painless enlargements of joints may also appearappear

This form is chronic, and may reoccur. The This form is chronic, and may reoccur. The animal will eventually die during an acute animal will eventually die during an acute episode of the disease. episode of the disease.


Clinical Signs: Clinical Signs: Low-virulence Low-virulence

Many nonpregnant animals infected with low-Many nonpregnant animals infected with low-virulence isolates may seroconvert but not virulence isolates may seroconvert but not show other signs of infectionshow other signs of infection

Pregnant animals will abortPregnant animals will abort


Clinical Signs:Clinical Signs:ChronicChronic

Transient / recurrent feverTransient / recurrent fever

Stunting / emaciationStunting / emaciation

PneumoniaPneumonia

Skin ulcersSkin ulcers


Gross LesionsGross LesionsHighly Virulent VirusHighly Virulent Virus

Peracute deaths Peracute deaths - - Lesions may be poorly Lesions may be poorly developeddeveloped

Animals that die 7 or Animals that die 7 or more DPI more DPI - - Classic lesions likely. Classic lesions likely.



Three lesions most consistent with ASF Three lesions most consistent with ASF infection: infection:

1. Greatly enlarged dark red to black friable spleen1. Greatly enlarged dark red to black friable spleen

2. Enlarged hemorrhagic gastrohepatic lymph 2. Enlarged hemorrhagic gastrohepatic lymph nodes nodes

3. Enlarged hemorrhagic renal lymph nodes 3. Enlarged hemorrhagic renal lymph nodes


Post-mortem examPost-mortem exam


LesionsLesions

Swollen necrotic spleen

Hemorrhagic gastro-hepatic lymph nodes


LesionsLesions

Large, necrotic Large, necrotic spleenspleen


LesionsLesions


Paracortical hemorrhage in gastrohepatic lymph node.Paracortical hemorrhage in gastrohepatic lymph node.

LesionsLesions


LesionsLesions


Gastrohepatic & Renal LN’sGastrohepatic & Renal LN’s


Renal cortical petechiae and ecchymoses


LesionsLesions


Lesions:Lesions:Peracute/AcutePeracute/Acute


Lesions


Lesions - AcuteLesions - Acute



Other lesions are more variable: Other lesions are more variable: Dark red to purple areas of Dark red to purple areas of skin on ears, feet, and tail. skin on ears, feet, and tail.

Petechial hemorrhages on Petechial hemorrhages on serosal surfacesserosal surfaces

Renal cortical petechial / Renal cortical petechial / ecchymotic hemorrhages ecchymotic hemorrhages

Perirenal edema Perirenal edema

Edema of the gall bladder Edema of the gall bladder

Swollen liver Swollen liver

Pulmonary edema Pulmonary edema


LesionsLesions


Gross LesionsGross LesionsModerately Virulent VirusModerately Virulent Virus

From 8-12 DPI From 8-12 DPI - - Gross lesions are similar whether pigs are Gross lesions are similar whether pigs are infected with a moderately virulent or highly infected with a moderately virulent or highly virulent ASFV. virulent ASFV.

The main difference between these two The main difference between these two types of isolates:types of isolates:- - Splenomegaly is still present,Splenomegaly is still present,- More normal color and is not friable. - More normal color and is not friable.


Chronic ASF: Chronic ASF: Necrotic skin lesionsNecrotic skin lesions

Raised reddened areas with central areas of necrosis

Raised reddened area behind the ear.


Gross LesionsGross LesionsLow Virulent VirusLow Virulent Virus

The most common The most common lesions in chronic ASFlesions in chronic ASF::

-Necrotic skin lesions -Necrotic skin lesions

-Consolidated lung -Consolidated lung lobules lobules

-Generalized -Generalized lymphadenopathy lymphadenopathy

-Swollen joints-Swollen joints

-Pericarditis-Pericarditis


Epidemiology:Epidemiology:Sylvatic cycle in AfricaSylvatic cycle in Africa

Infected Argasid ticks in warthog Infected Argasid ticks in warthog burrowsburrowstransmit virus to young warthogs. transmit virus to young warthogs. - Pigs remain infected for life.- Pigs remain infected for life.- Transtadial, transovarial, sexual - Transtadial, transovarial, sexual transmission.transmission.

Pigs can be raised successfully in Pigs can be raised successfully in confinement with double fencing, confinement with double fencing, proper isolation, and sanitary proper isolation, and sanitary procedures.procedures.


Epidemiology:Epidemiology:Epidemic cycleEpidemic cycle

Introduction into domestic swine by Introduction into domestic swine by feedingfeedinggarbage / swill contaminated with pork garbage / swill contaminated with pork scraps.scraps.Blood contaminated sourcesBlood contaminated sources

Direct contact and fomitesDirect contact and fomites - People- People - Vehicles - Vehicles - Equipment - Equipment - Feed - Feed



Transmission by contact and ticksTransmission by contact and ticks


Provided by Dr Tom McKenna, USDA APHIS IS



http://vein.library.usyd.edu.au/links/exoticdiseases/exoimages/Trd276.jpg

The soft tick has The soft tick has been proven a been proven a vectorvector

Primary Method:Primary Method:– Feeding of uncooked Feeding of uncooked

garbage containing garbage containing African Swine Fever African Swine Fever infected pork scraps infected pork scraps to pigs.to pigs.



Wild suids in Africa are carriers of the virusWild suids in Africa are carriers of the virusAcquire the virus from Acquire the virus from Ornithodoros moubataOrnithodoros moubata that invade that invade warthog burrowswarthog burrowsYoung warthogs become infected as neonates and retain Young warthogs become infected as neonates and retain high viral titres for up to about 3 weekshigh viral titres for up to about 3 weeksWhere ASF becomes endemic in domestic pigs, the virus Where ASF becomes endemic in domestic pigs, the virus is maintained by carrier pigsis maintained by carrier pigs



Warthog burrowWarthog burrow



Ingestion Ingestion Tonsil Tonsil Local LNs Local LNs Viremia Viremia

Virus in excretions and secretions, blood.Virus in excretions and secretions, blood.

Carrier pigs incriminated in maintaining Carrier pigs incriminated in maintaining

infection in herds.infection in herds.

Pigs with mild forms of ASF may shed virus Pigs with mild forms of ASF may shed virus

for ~ 30 days.for ~ 30 days.

Bites of infected ticks.Bites of infected ticks.



Once a pig is infected, the disease Once a pig is infected, the disease spreads by:spreads by:– Direct contact Direct contact – Contaminated people, vehicles, feedContaminated people, vehicles, feed

– Carrier pigs Carrier pigs – EquipmentEquipment


DiagnosisDiagnosis

African Swine Fever should always be African Swine Fever should always be suspected where there are febrile pigs suspected where there are febrile pigs

Necropsy findings include:Necropsy findings include:– Greatly enlarged spleen, dark red to black in Greatly enlarged spleen, dark red to black in

color, friable spleencolor, friable spleen– Very enlarged, hemorrhagic gastrohepatic Very enlarged, hemorrhagic gastrohepatic

lymph nodeslymph nodes– Very enlarged, hemorrhagic renal lymph Very enlarged, hemorrhagic renal lymph

nodesnodes


DiagnosisDiagnosis

Hog Cholera vs. African Swine FeverHog Cholera vs. African Swine Fever– Hog cholera infected pigs become depressed Hog cholera infected pigs become depressed

and lose weight, whereas ASF infected pigs and lose weight, whereas ASF infected pigs have neither symptoms have neither symptoms

– Hog cholera is also characterized by a foul-Hog cholera is also characterized by a foul-smelling diarrhea smelling diarrhea


DiagnosisDiagnosisLaboratory SpecimensLaboratory Specimens

Serum / clotted bloodSerum / clotted blood

EDTA, heparin bloodEDTA, heparin blood

Lymph nodesLymph nodes

SpleenSpleen

TonsilTonsil

LungLung

LiverLiver

KidneyKidney


DiagnosisDiagnosisLaboratory DiagnosisLaboratory Diagnosis

Virus isolationVirus isolation

- Haemadsorption test (HAD) of - Haemadsorption test (HAD) of leukocyte cultures. leukocyte cultures.- Haemadsorption autorosette- Haemadsorption autorosette test of PBLs of suspect pigs. test of PBLs of suspect pigs.

Pig inoculationPig inoculation

- Requires inoculation of naïve- Requires inoculation of naïve and CSF-vaccinated pigs. and CSF-vaccinated pigs.- Not recommended with newer- Not recommended with newer tests available. tests available.


DiagnosisDiagnosisLaboratory DiagnosisLaboratory Diagnosis

Virus antigen detectionVirus antigen detection- Direct fluorescent antibody - Direct fluorescent antibody test (DFAT) test (DFAT)

Virus genome detectionVirus genome detection- Polymerase Chain Reaction - Polymerase Chain Reaction (PCR) (PCR) - - PCR-based sequencing method which PCR-based sequencing method which permits detection and characterization of permits detection and characterization of ASFV variants. ASFV variants.- Useful for molecular epidemiological- Useful for molecular epidemiological clarification of ASFV clarification of ASFV

Bastos, Penrith, Cruciere, et al. Arch Virol. 2003 148(4):693-706. Genotyping field strains of African swine fever virus by partial p72 gene characterisation.


DiagnosisDiagnosisField DiagnosisField Diagnosis

Peracute and Acute InfectionPeracute and Acute Infection

3 Classic Lesions:3 Classic Lesions:1. Large dark friable spleen1. Large dark friable spleen2. Large hemorrhagic gastrohepatic LNs2. Large hemorrhagic gastrohepatic LNs3. Large hemorrhagic renal LNs3. Large hemorrhagic renal LNs

Renal petechiae, serosal hemorrhagesRenal petechiae, serosal hemorrhages


Differential DiagnosisDifferential Diagnosis

Classical Swine FeverClassical Swine Fever

SalmonellosisSalmonellosis

ErysipelasErysipelas

EperythrozoonosisEperythrozoonosis

SepticemiasSepticemiasPorcine Reproductive and Respiratory Porcine Reproductive and Respiratory Syndrome (PRRS)Syndrome (PRRS)

Porcine Dermatitis and Nephropathy Porcine Dermatitis and Nephropathy Syndrome (PDNS)Syndrome (PDNS)


African Swine Fever - African Swine Fever - BibliographyBibliography

““African Swine Fever." African Swine Fever." OIE OIE . 22 Apr. 2002. 12 July 2005. <. 22 Apr. 2002. 12 July 2005. <

http://www.oie.int/eng/maladies/fiches/a_A120.htmhttp://www.oie.int/eng/maladies/fiches/a_A120.htm >. >.

Keeping America Free From Foreign Animal DiseasesKeeping America Free From Foreign Animal Diseases. Vol. 2. . Vol. 2.

African Swine Disease. USDA, 1997. African Swine Disease. USDA, 1997. Tom McKenna, DVM PhD, USDA APHISTom McKenna, DVM PhD, USDA APHIS, “African Swine Fever” , “African Swine Fever”

CSU Foreign Animal Disease Training Course, Aug 1-5, 2005.CSU Foreign Animal Disease Training Course, Aug 1-5, 2005.Moritz van Vuuren, Department of Veterinary Tropical Diseases,

Faculty of Veterinary Science, University of Pretoria, “African Swine Fever”

W.A. Geering, A.J. Foreman and M.J. Nunn, W.A. Geering, A.J. Foreman and M.J. Nunn, Exotic Diseases of Exotic Diseases of AnimalsAnimals, 1995 Australian Govt Publishing Service, Canberra; , 1995 Australian Govt Publishing Service, Canberra; p.218- 224. Plus picture web sites (below pictures) p.218- 224. Plus picture web sites (below pictures)


Image AcknowledgementsImage Acknowledgements

Watermarks key:

“CB UGA” are images provided by Dr Corrie Brown of the University of Georgia, Department of Pathology

“KAW” images were taken by Dr Kenneth A. Waldrup

“KOOS” denotes images provided by Professor Koos Coetzer of the University of Pretoria Dept of Tropical Veterinary Medicine

“LLogan” images were taken by Dr Linda Logan on her travels

“MVV” denotes those images provided by Professor Moritz van Vuuren of the University of Pretoria Dept of Tropical Veterinary Medicine

“SUZ” images were taken by Dr Suzanne Burnham

“USDA” images have mostly come from photos taken during the Plum Island FADD courses by Kathy Appicelli and Liz Clark


AcknowledgementsAcknowledgementsSpecial thanks to Special thanks to Linda Logan, DVM PhD, Linda Logan, DVM PhD, USDAUSDATom McKenna, DVM USDATom McKenna, DVM USDACorrie Brown, DVM PhD, U of Georgia, Dept Corrie Brown, DVM PhD, U of Georgia, Dept

Path.Path.Ken Waldrup, DVM PhDKen Waldrup, DVM PhDKathy Appicelli, photographer, PIADCKathy Appicelli, photographer, PIADCMortiz van Vuuren, U of Pretoria, Dept Vet MedMortiz van Vuuren, U of Pretoria, Dept Vet MedRobin Sewell, DVM Robin Sewell, DVM Kelsey Pohler- Research Assistant Kelsey Pohler- Research Assistant

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