Bluetongue Fact Sheet for Veterinarians

Background

• Bluetongue is a vector-borne viral disease caused by an orbivirus.
• Endemic in many areas of the world including the United States; currently not found in Canada except for periodic incursions in the Okanagan Valley of British Columbia associated with windborne vectors.
• Most ruminants are susceptible to infection but clinically important disease is largely restricted to sheep. Cattle are the reservoir and amplifying hosts.

• Reportable disease under the Federal Health of Animals Regulations that require that all cases be reported to the Canadian Food Inspection Agency (CFIA).
• The current potential for bluetongue to spread in Canada is poor and limited both seasonally and geographically. However, climatic change has the potential to change bluetongue distribution patterns.
• Important means of transmission is biologically through midge bites (Culicoides sp.).
• A closely related orbivirus causes Epizootic Hemorrhagic Disease (EHD) in deer.
• Bluetongue poses no risk to human health.

• http://www.iah.bbsrc.ac.uk/bluetongue/
• In cattle, usually clinically unapparent but some strains may affect cattle.
• In sheep, usually an acute disease with fever; death may occur in up to 70% of cases. Clinically unapparent infection is possible in sheep also.
• Excessive salivation and nasal discharge; can be bloody.
• Swelling of the lips, tongue, and lower jaw.
• Widespread hemorrhage of the oral and nasal tissue.
• Ulceration of the buccal cavity, tongue and dental pad.
• Cyanosis of the tongue ("bluetongue") can be seen but absence does not rule out the disease.
• Coronitis with lameness.
• Emaciation due to a sore mouth and reduced feed intake.
• Fetal resorption, abortions, birth of “dummy” lambs.
• Can see profuse diarrhea, vomiting and aspiration pneumonia.
• Recovered sheep may show “wool break” three – four weeks after the fever.

• http://www.defra.gov.uk/animalh/diseases/notifiable/bluetongue/photo.htm
• Facial and head edema, exudate on skin, crusty nasal discharge.
• Coronary band inflammation as severe as to lead to sloughing of the hoof.
• Oral petecchia progressing to grey necrotic debris over erosions/ulcers.
• Upper respiratory mucosal cyanosis, edema and hemorrhage.
• Hemorrhage at the base of pulmonary artery is close to pathognomonic; absence does not rule out bluetongue.
• Endocardial petecchiation, focal myocardial necrosis.
• Enlarged spleen and lymph nodes.
• Newborn lambs with hydrencephaly.
• Lesions in cattle, if seen, localize to skin with dry, crusty exudate over cervical and thoracic skin, oral vesicles to ulcers, nasal erosions with crusty exudate and coronitis.
• Deer with EHD show very widespread petecchial to ecchymotic hemorrhage throughout the body.

• Whole blood: collect in as many anticoagulants as you have, at least EDTA and heparin.
• Serum.
• Fresh tissues: collect those rich in blood or hematopoietic tissues including lung, liver, spleen, lymph nodes, and bone marrow. Sample size of 3 – 4 cm³ for each tissue is sufficient. Ship chilled at 4^oC.
• Formalin fixed tissues: collect same ones as for fresh. Sample size of 1 – 2 cm² x 0.5 cm thick. Ensure formalin:tissue ratio = 10:1.
• Oral and mucocutaneous lesions: collect fresh and fixed samples.
• Diagnostic tests for bluetongue done at CFIA Winnipeg Laboratory.

• Grazing on orofacial irritants, e.g. stinging nettles
• Pneumonia
• Actinobacillosis
• Malignant Catarrhal Fever
• Infestation by Oestrus ovis
• Photosensitization
• Vesiculoulcerative diseases: Foot and Mouth Disease, Vesicular Stomatitis, Sheep Pox, Contagious Ecthyma (orf)
• Peste de petits ruminants, Rinderpest

• If bluetongue is suspected, the CFIA must be notified through your nearest district office. Provincial authorities may also be contacted, through the Office of the Chief Provincial Veterinarian.
• For further information see: http://www.inspection.gc.ca/english/anima/heasan/disemala/blufie/blufiee.shtml. This website includes decontamination procedures that can be used in your clinic. The virus survives very poorly outside a vector or host but good biosafety and disinfection procedures should always be followed.