African Horse Sickness African Horse Sickness
Texas A&M University Texas A&M University College of Veterinary MedicineCollege of Veterinary Medicine
JeffreyJeffrey Musser,Musser, DVM,DVM, PhD,PhD, DABVPDABVP SuzanneSuzanne Burnham,Burnham, DVMDVM 20062006 Special thanks for materials Special thanks for materials borrowed with permission borrowed with permission from presentations by:from presentations by:
Dr Corrie Brown, Dr Corrie Brown, ““African Horse SicknessAfrican Horse Sickness ”” CSU Foreign Animal Disease Training Course, CSU Foreign Animal Disease Training Course, College of Veterinary Medicine and Biomedical College of Veterinary Medicine and Biomedical Sciences, August 1Sciences, August 1 --5, 2005. 5, 2005. Professor Alan Guthrie, Department of Professor Alan Guthrie, Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, “African Horse Sickness” presented at the FEAD course in Knoxville, Tenn. 2005. ImagesImages
Pathological lesion images marked Pathological lesion images marked ““USDAUSDA ”” were taken by staff photographers were taken by staff photographers at the Plum Island Animal Disease Center at the Plum Island Animal Disease Center lab and were presented by Dr Corrie lab and were presented by Dr Corrie BrownBrown Images of symptoms marked Images of symptoms marked ““GuthrieGuthrie ”” were presented in Tennessee by Dr Alan were presented in Tennessee by Dr Alan GuthrieGuthrie African Horse SicknessAfrican Horse Sickness
EtiologyEtiology Host rangeHost range Incubation Incubation Clinical signsClinical signs TransmissionTransmission Diagnosis Diagnosis Differential DiagnosisDifferential Diagnosis
African Horse Sickness African Horse SicknessAfrican Horse Sickness
African horse sickness (AHS) is African horse sickness (AHS) is an infectious but an infectious but noncontagious, insectnoncontagious, insect --borne borne viral disease affecting all viral disease affecting all species of equids. species of equids.
It is transmitted in the field by It is transmitted in the field by at least two species of at least two species of CulicoidesCulicoides ..
African Horse Sickness African Horse Sickness is an OIE reportable diseaseAfrican Horse Sickness is an OIE reportable disease. . African Horse Sickness If you hear hoof beats, look for horses….
www.hedweb.com/animalag/horsesw.htm
African Horse Sickness But don’t forget to look for zebras too
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http://www.singerhuette.at/Afrika/Serengeti%202%202003.htm
African Horse Sickness African Horse Sickness in the World in 2004. OIE
http://www.oie.int/eng/info/en_presdistribgeo.htm
Disease reported present
Disease reported absent Data unavailable or incomplete African Horse Sickness EtiologyEtiology
African Horse Sickness is caused by an African Horse Sickness is caused by an OrbivirusOrbivirus of the family of the family ReoviridaeReoviridae
ViscerotropicViscerotropic virusvirus
Family: Family: ReoviridaeReoviridae , Genus: , Genus: OrbivirusOrbivirus
Nine different serotypes of the virus Nine different serotypes of the virus have been describedhave been described
African Horse Sickness SerotypesSerotypes $OOVHURW\SHVRI$+6$OOVHURW\SHVRI$+6 YLUXVRFFXULQHDVWHUQYLUXVRFFXULQHDVWHUQ DQGVRXWKHUQ$IULFD WKLVDQGVRXWKHUQ$IULFD WKLV GLVWULEXWLRQUHIOHFWVWKHGLVWULEXWLRQUHIOHFWVWKH JHRJUDSKLFSDWWHUQRIJHRJUDSKLFSDWWHUQRI ]HEUDZKLFKF\FOHWKH]HEUDZKLFKF\FOHWKH YLUXVDV\PSWRPDWLFDOO\YLUXVDV\PSWRPDWLFDOO\ DQGSUREDEO\VHUYHDVDDQGSUREDEO\VHUYHDVD UHVHUYRLUIRUWKHYLUXVUHVHUYRLUIRUWKHYLUXV
African Horse Sickness SerotypesSerotypes
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African Horse Sickness Virus CharacteristicsVirus Characteristics
The virus can be inactivated by:
repeated freezing and thawing
by treatment with acetic acid (at pH of 6.3 or lower), remaining for 2 weeks at 37°C, or being placed for 5 minutes at 70°C.
African Horse Sickness Host RangeHost Range
In order of decreasing severity of In order of decreasing severity of disease:disease:
HorsesHorses MulesMules DonkeysDonkeys ZebrasZebras
African Horse Sickness Approximately 70Approximately 70 --95 percent of all horses 95 percent of all horses developing the disease will die developing the disease will die
African Horse Sickness yet the mortality percentage for yet the mortality percentage for mules is only about 50 percent mules is only about 50 percent and for donkeys only 10 percent.and for donkeys only 10 percent.
African Horse Sickness Role of ZebrasRole of Zebras
AHS virus overAHS virus over -- winters in zebras winters in zebras in Kruger in Kruger National Park, National Park, from where it from where it spreads spreads westwards and westwards and southwards southwards Image courtesy of Dr Corrie Brown every year. every year. African Horse Sickness ZebrasZebras
AHS remains AHS remains endemic in zebra endemic in zebra populations across populations across South AfricaSouth Africa
They harbor the virus They harbor the virus and are often the and are often the source of sudden source of sudden outbreaks in Africaoutbreaks in Africa
African Horse Sickness Host Range Host Range
Dogs can also become infected by Dogs can also become infected by eating infected meat.eating infected meat.
19871987 --90 outbreak in Spain:90 outbreak in Spain: Dogs that did not consume infected Dogs that did not consume infected meat were found to be meat were found to be seropositiveseropositive , , suggesting infection by arthropod suggesting infection by arthropod bites. bites.
African Horse Sickness Host RangeHost Range
There is no evidence that humans can be There is no evidence that humans can be infected by field strains of the disease. infected by field strains of the disease. However, intranasal exposure to However, intranasal exposure to neurotrophicneurotrophic vaccine strains has caused vaccine strains has caused encephalitis and retinitis in humans.encephalitis and retinitis in humans.
African Horse Sickness IncubationIncubation
In experiments, African Horse Sickness In experiments, African Horse Sickness usually has a 5 to 7 day incubation usually has a 5 to 7 day incubation period.period.
In natural infections, circumstantial In natural infections, circumstantial evidence indicates that the incubation evidence indicates that the incubation period is from 7 to 14 days. period is from 7 to 14 days.
African Horse Sickness Clinical SignsClinical Signs
Infected horses remain viremic for Infected horses remain viremic for approximately 18 days, although the fever approximately 18 days, although the fever may be present for another 4 to 8 days, if may be present for another 4 to 8 days, if the animal should live that long. Despite the animal should live that long. Despite their reduced mortality, the viremic stage their reduced mortality, the viremic stage in donkeys may last for up to 28 days. in donkeys may last for up to 28 days. Zebras appear to be very similar to Zebras appear to be very similar to donkeys in this regard.donkeys in this regard.
African Horse Sickness Clinical SignsClinical Signs
First Sign:First Sign:
Fever of 102Fever of 102 °°FF to to 106106 °°F, F,
(38.9(38.9 °°C C -- 41.141.1 °°C)C)
African Horse Sickness Clinical SignsClinical Signs
Most Common SignMost Common Sign
Congestion of Congestion of the conjunctivaethe conjunctivae
Severity of Severity of congestion is congestion is good indication good indication of severity of of severity of
infectioninfection African Horse Sickness Clinical SignsClinical Signs
Lower Eyelid ConjunctivitisLower Eyelid Conjunctivitis
African Horse Sickness Clinical SignsClinical Signs After initial signs, the disease can progress in one of four ways:
Peripheral (Cardiac) called “Dikkop” in S. Africa
Central (Pulmonary) called “Dunkop” in S. Africa Mixed Form (Acute) Mixed Form (Fever)
African Horse Sickness Clinical Signs: Clinical Signs: PulmonaryPulmonary Fever up to 104Fever up to 104 °°FF to 106to 106 °°FF Increasingly more Increasingly more rapid respiration rapid respiration and abdominal and abdominal expirationexpiration Respiratory rate may reach 60 -70 per minute http://www.vet.ed.ac.uk/animalpain/Pages/images/Optimised Coughing and Coughing and %20Images/optphotos/EQsweating.jpg SweatingSweating
African Horse Sickness Clinical Signs: PulmonaryClinical Signs: Pulmonary
Horse may appear Horse may appear colicky (getting up colicky (getting up and down, and and down, and rolling)rolling) As pulmonary As pulmonary distress increases:distress increases:
Animal stands with forelegs apart
Head extended
Nostrils dilated
African Horse Sickness Clinical Signs: PulmonaryClinical Signs: Pulmonary
Once foam Once foam appears appears in nostrils, in nostrils, death death follows rapidly.follows rapidly.
Animal may drink and eat, even in terminal stages.Animal may drink and eat, even in terminal stages.
African Horse Sickness Clinical Signs: PulmonaryClinical Signs: Pulmonary
Photo courtesy of Plum Island African Horse Sickness In my few encounters with the disease, I was In my few encounters with the disease, I was struck by the extreme struck by the extreme respiratory distress including froth pouring from trespiratory distress including froth pouring from the he nostrils, nostrils, extensive hydrothorax and extensive hydrothorax and hydropericaridiumhydropericaridium , , supraorbitalsupraorbital edema and a edema and a gelatinous infiltration of subcutaneous tissue and gelatinous infiltration of subcutaneous tissue and intermuscularintermuscular fascialfascial planes along the planes along the ligamentumligamentum nuchaenuchae and and muscles of the muscles of the shoulder. shoulder. Dr Botlhe Modisane 2006
African Horse Sickness In 2004, South Africa reported 196 outbreaks In 2004, South Africa reported 196 outbreaks resulting in 335 cases resulting in 335 cases and 166 deaths. The case fatality rate was even and 166 deaths. The case fatality rate was even higher in 2003, with higher in 2003, with 89 outbreaks resulting in 510 cases and 441 89 outbreaks resulting in 510 cases and 441 deaths. Prior to this deaths. Prior to this outbreak, the Western Cape province had been outbreak, the Western Cape province had been declared an AHSdeclared an AHS --free free zone from which horses could be exported. zone from which horses could be exported. -- Mod.PCMod.PC ]]
African Horse Sickness Clinical Signs: CardiacClinical Signs: Cardiac
Incubation is usually longer (7Incubation is usually longer (7 --14 days)14 days)
Fever of 102Fever of 102 --106106 °°F usually lasts 3F usually lasts 3 --6 6 daysdays
African Horse Sickness Clinical Signs: Cardiac Clinical Signs: Cardiac
At the end of the febrile At the end of the febrile period, marked period, marked swelling of the head swelling of the head and neck may occurand neck may occur
African Horse Sickness Clinical Signs: Cardiac Clinical Signs: Cardiac
Classic areas for swelling Classic areas for swelling are:are: Supraorbital fossa Conjunctiva Lips, cheeks, tongue Intermandibular space Laryngeal area Neck, brisket, ventral thorax
African Horse Sickness http://www.spc.int/rahs/Manual/images/AfrHorsSick-09.jpg Clinical Signs: CardiacClinical Signs: Cardiac
PeriPeri --orbital swellingorbital swelling
African Horse Sickness Clinical Signs: CardiacClinical Signs: Cardiac
No edema of the lower parts of the legs No edema of the lower parts of the legs occursoccurs Petechial hemorrhages on the ventral Petechial hemorrhages on the ventral surface of the tongue and in conjunctiva surface of the tongue and in conjunctiva may occurmay occur As edema progresses, there may be As edema progresses, there may be restlessness and signs of abdominal pain restlessness and signs of abdominal pain and pulmonary edemaand pulmonary edema
African Horse Sickness Clinical Signs: CardiacClinical Signs: Cardiac
Finally, Finally, animal animal becomes becomes prostrate, prostrate, and diesand dies Again, Again, animal may animal may eat and eat and drink, even in drink, even in terminalterminal http://www.usyd.edu.au/su/rirdc/articles/disease/ahs.jpg stagesstages
African Horse Sickness Clinical Signs: CardiacClinical Signs: Cardiac
http://www.vet.uga.edu/vpp/IVM/ENG/Modes/definition03.htm
African Horse Sickness Recovery: CardiacRecovery: Cardiac
If the disease is not fatal, the edema If the disease is not fatal, the edema will subside over 3 to 8 days.will subside over 3 to 8 days.
African Horse Sickness Clinical Signs: Mixed Form Clinical Signs: Mixed Form (acute)(acute)
Mixture of pulmonary and cardiac Mixture of pulmonary and cardiac formsforms
Signs of one may be predominateSigns of one may be predominate
The mixed form is more The mixed form is more frequently seen at necropsyfrequently seen at necropsy
African Horse Sickness Clinical Signs: Mixed Form Clinical Signs: Mixed Form (acute)(acute)
http://www.vet.uga.edu/vpp/IVM/ENG/Horse/index.htm
African Horse Sickness Clinical Signs: Clinical Signs: Mixed Form (fever)Mixed Form (fever)
Mildest formMildest form Can be Can be subclinicalsubclinical or inapparentor inapparent Occurs in zebras, donkeys, and horses with Occurs in zebras, donkeys, and horses with heterologousheterologous immunity.immunity. Fever is usually intermittentFever is usually intermittent ——usually normal usually normal temperature in the morning, but is febrile in temperature in the morning, but is febrile in the afternoonthe afternoon Fever may reach 104Fever may reach 104 °°F in 1 or 2 daysF in 1 or 2 days
African Horse Sickness Clinical Signs: Clinical Signs: Mixed Form (fever)Mixed Form (fever) Other Clinical Signs: Increased respiratory rate Mild conjunctival congestion Accelerated pulse Loss of appetite is rare and mild
After 1 or 2 days, there is a rapid recovery
African Horse Sickness Morbidity is dependant upon exposure
Mortality varies with serotype and strain; mortality in naïve horses can be high
African Horse Sickness Post Mortem LesionsPost Mortem Lesions
African Horse Sickness Sudden Death
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African Horse Sickness Pulmonary EdemaPulmonary Edema
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African Horse Sickness Myocardial necrosis
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African Horse Sickness LesionsLesions
African Horse Sickness LesionsLesions
African Horse Sickness LesionsLesions
African Horse Sickness LesionsLesions
African Horse Sickness TransmissionTransmission
http://www.iah.bbsrc.ac.uk/images/Culicoides.jpg
African Horse Sickness TransmissionTransmission
AHSvAHSv is spread primarily by is spread primarily by CulicoidesCulicoides (ex: biting flies and mosquitoes) by (ex: biting flies and mosquitoes) by transfer of bloodtransfer of blood –– CulicoidesCulicoides are biological vectors because are biological vectors because the disease can replicate in the midgethe disease can replicate in the midge –– In U.S., In U.S., CulicoidesCulicoides that can transmit that can transmit bluetongue virus most likely can transmit bluetongue virus most likely can transmit African Horse SicknessAfrican Horse Sickness –– CulicoidesCulicoides are most active at sunset and are most active at sunset and about sunriseabout sunrise African Horse Sickness TransmissionTransmission
African Horse Sickness is African Horse Sickness is nonnon --contagiouscontagious , , but the horse is an amplifier of AHS virus but the horse is an amplifier of AHS virus and source of virus for arthropods. and source of virus for arthropods.
Arthropods other than Arthropods other than CulicoidesCulicoides may may spread the virus as mechanical vectors spread the virus as mechanical vectors
African Horse Sickness Other VectorsOther Vectors
AedesAedes aegyptiaegypti Anopheles Anopheles sephensisephensi CulexCulex PipiensPipiens HyalommaHyalomma dromedariidromedarii RipicephalusRipicephalus sanguineussanguineus
African Horse Sickness This particular virus favors warmer This particular virus favors warmer conditions, when it has a preferred vector conditions, when it has a preferred vector available. It may move best in moist, mild available. It may move best in moist, mild conditions and travel long distances on the conditions and travel long distances on the windwind --borne vectors.borne vectors.
African Horse Sickness DiagnosisDiagnosis
AHS is difficult to pinpoint in early febrile AHS is difficult to pinpoint in early febrile stagesstages
Suspect the disease during the season Suspect the disease during the season when there are insect vectorswhen there are insect vectors
African Horse Sickness DiagnosisDiagnosis
Suspect when horses develop the Suspect when horses develop the following:following: –– FeverFever –– DyspneaDyspnea –– Edema of the Edema of the supraorbitalsupraorbital fossafossa –– Subcutaneous edema of head/neck areasSubcutaneous edema of head/neck areas –– Pulmonary edemaPulmonary edema –– DeathDeath
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African Horse Sickness Differential DiagnosisDifferential Diagnosis
Anthrax Anthrax BotulismBotulism Equine infectious anemia Equine infectious anemia Equine viral Equine viral arteritisarteritis High doses of High doses of pyrrolizidinepyrrolizidine alkaloidsalkaloids TrypanosomosisTrypanosomosis Equine Equine encephalosisencephalosis Piroplasmosis Piroplasmosis PurpuraPurpura haemorrhagicahaemorrhagica
African Horse Sickness ControlControl
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African Horse Sickness Vaccine in South AfricaVaccine in South Africa
African Horse Sickness DiseaseDisease –– Economic Economic ImpactImpact Horse study reveals Horse study reveals almost $40 billion almost $40 billion impact on U.S. impact on U.S. economyeconomy
Staff Reports, Oroville Mercury -Register July 23, 2005
African Horse Sickness Donkeys and Mules are a growing segment of the equine industry
African Horse Sickness DiseaseDisease –– Economic ImpactEconomic Impact
The horse industry in the United The horse industry in the United States contributes $39 billion in States contributes $39 billion in direct economic impact to the U.S. direct economic impact to the U.S. economy and supports 1.4 million economy and supports 1.4 million jobs on a fulljobs on a full --time basis, according time basis, according to a new study released today by the to a new study released today by the American Horse Council (AHC). American Horse Council (AHC).
African Horse Sickness DiseaseDisease –– Economic ImpactEconomic Impact
When indirect and induced spending When indirect and induced spending are included, the industry's are included, the industry's economic impact reaches $102 economic impact reaches $102 billion. billion.
African Horse Sickness DiseaseDisease –– Economic ImpactEconomic Impact
The study also estimates the horse The study also estimates the horse population in this country has population in this country has reached 9.2 million.reached 9.2 million.
African Horse Sickness World Distribution of DiseaseWorld Distribution of Disease
http://www.vet.uga.edu/vpp/IVM/ENG/Horse/vector.ht m African Horse Sickness African Horse Sickness African Horse Sickness African Horse SicknessAfrican Horse Sickness -- ReferencesReferences
1) "African Horse Sickness." OIE . 22 Apr. 2002. 12 July 2005
2) Barnard, B. J. H. (1998). Epidemiology of African Horse Sickness and the Role of the Zebra in South Africa. African Horse Sickness . P. S. Mellor, et al. Vienna, Austria, Springer - Verlag : 13 -19.
3) Corrie Brown “Pathology of Foreign Animal Diseases: African Horse Sickness ”
African Horse Sickness ReferencesReferences
4) Foreign Animal Diseases (1992). United States Animal Health Association. Cummings Corporation and Carter Printing Company, Richmond, VA.
5) Geering , W. A., Forman, A. J., and Nunn, M. J. (1995) Exotic Diseases of Animals: a field guide for Australian veterinarians . Australian Government Publishing Service, Canberra.
6) Keeping America Free From Foreign Animal Diseases . Vol. 1. African Horse Sickness. USDA, 1997.
7) Good Emergency Management Practice. Plum Island 2002 CD -3
African Horse Sickness ReferencesReferences
8. Professor Alan Guthrie, U of Pretoria Dept of Tropical Vet Med, “African Horse Sickness ” FEAD course Tenn , Aug 1 -5, 2005. ( ppt and video) 9. Corrie Brown, DVM PhD University of Georgia, Dept of Pathology “African Horse Sickness ” PowerPoint presentation
African Horse Sickness AcknowledgementsAcknowledgements
Special thanks to:Special thanks to: Jeffrey Musser, DVM PhD, DABVPJeffrey Musser, DVM PhD, DABVP Linda Logan, DVM PhD, Linda Logan, DVM PhD, Ken Waldrup, DVM PhDKen Waldrup, DVM PhD Corrie Brown, DVM PhDCorrie Brown, DVM PhD Robin Sewell, DVM Robin Sewell, DVM Kelsey PohlerKelsey Pohler -- Research Assistant Research Assistant TitaTita Burnham Burnham –– Student AssistantStudent Assistant
African Horse Sickness