A Case Study in Recognizing a Foreign Animal Disease

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A Case Study in Recognizing a Foreign Animal
Disease

• Ann Predgen and Lauren Gnagey

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Foreign Animal Diseases

• Increasing threat
• Increased international trade
• Bioterrorism
• Diagnostics not 100
• accurate
• Often look like other
• diseases

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Vets and Foreign Animal Disease

• Dont always infect humans
• Little training in veterinary school
• Consolidation of livestock industry means rapid
  spread
• The vectors are already here!
• HUGE economic impact
• Trade restrictions
• Animal losses

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The Call

• 26 year old Quarter Horse mare
• History of heaves
• Lives out on pasture
• Sudden onset of heaves attack

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Presentation

• Respiratory distress
• Abdominal breathing

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Presentation

• Froth from nostrils
• Sudden collapse
• Rapid death

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Additional History

• No recent changes to management
• Up to date on vaccinations
• Try to keep pastures weeded
• Wet summer
• lots of flies, mosquitos, no-see-ums
• Neighbor has recently imported a mare

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Up at the Barn

• Depressed
• Febrile (104º )
• Colicky
• Facial Edema

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Supra/Periorbital Edema
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Differential Diagnoses

• Respiratory infection?
• Equine Viral Arteritis?
• Equine Encephalitis?
• Rodenticide or plant intoxication?
• Foreign Animal Disease????

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African Horse Sickness

• A non-contagious insect-borne orbivirus of equids
  
• Transmitted by Culicoides spp.
• Endemic in tropical regions of Africa
• Has occasionally migrated to other areas
• A List A foreign animal disease!!!

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What Do You Do???

• If you suspect a possibility of a foreign animal
  disease
• Call your State Veterinarian!!
• A FAD investigation will be launched.

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African Horse Sickness

• Pathogenesis
• Diagnosis
• Preventive Measures
• Public Health Considerations

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Subclinical Form

• Flu-like symptoms followed by recovery
• aka Horsesickness fever

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Clinical SignsPulmonary Form

• Fever
• Dyspnea
• Spasmodic coughing
• Dilated nostrils with foam exudate
• Redness of conjunctivae

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Clinical SignsCardiac Form

• Swelling of supraorbital fossa, eyelids, face,
  neck thorax, brisket and shoulders.
• Death usually within one week

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Clinical Signs Mixed Form

• Common
• Milder pulmonary signs followed by edema. Death
  from cardiac failure
• Sometimes subclinical cardiac form is followed by
  severe pulmonary form.

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Pathologic Lesions

• Depends on clinical presentation

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Pulmonary Form
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Pulmonary Form
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Cardiac Form Hydropericardium
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Cardiac Form Subcutaneous Edema
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Cardiac Form--Edema
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Petechial hemorrhages on serosal surface of
intestines
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Petechiae on diaphragm
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Histopathology edema in lung
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Diagnosis

• There is no pathognomonic lesion
• Collect blood and tissues
• Need laboratory confirmation
• Viral isolation and serology

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Preventive Measures
Disease may be introduced by donkeys or zebras
which are incubating the disease but not showing
clinical signs

• Disease may be

Incubator???
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Preventive Measures

60 Day Quarantine Period for Equids from Asia,
Africa, and the Mediterranean
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Control Steps in an Outbreak

• Stop movement of equines
• Stabling insect repellent
• Monitor rectal temperatures

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African Horse Sickness in Spain

• A zebra with subclinical AHS was imported into
  Spain in 1987
• Culicoides vector became infected and spread the
  disease

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Is AHS a public health risk?
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Back at the Farm

• FAD investigation launched
• Farms quarantined
• No animal movement
• Infected animals euthanized
• Heavy insect control measures
• Crisis hopefully averted!

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References

• Equine Medicine and Surgery, 5th ed., Colahan,
  et. al.
• The Gray Book, online at http//www.vet.uga.edu/vp
  p/gray_book/FAD/index.htm
• http//www.vet.uga.edu/vpp/fad/horse/conclus.htm
• http//www.aphis.usda.gov/vs/ep/fad_training/DEANS
  PRO/ahdindex.htm
• http//www.fao.org/WAICENT/FAOINFO/AGRICULT/AGA/AG
  AH/EMPRES/GEMP/resources/resources.html