Bluetongue 2008–2009: Unusual Cases

Abstract

Orbivirus diagnosis in an endemic country presents many diag­nostic complexities. Endemicity is further complicated by mul­tiple serotypes and related viruses which may be cross-reactive in some tests or else be clinically indistinguishable. Some of the cases of either bluetongue (BT) or epizootic haemorrhagic disease (EHD) of the 2008 and 2009 summer seasons are pre­sented to illustrate the challenges. Selection focused on two bovines and three alpacas for which no final diagnoses had been made or confirmed. The two heifers were young, geographi­cally distant but similar in clinical presentation with dysphagia and oesophageal dilations. BTV-6 and 16 were recovered from what were considered to be EHD cases, and no final conclusion was made. The three alpacas formed a geographical cluster, although they were resident on different farms. Two were local and one had been recently imported. In clinical presentation, all three differed and two remained unresolved with no isolate or polymerase chain reaction (PCR) result. The last case, an acute death with severe lung oedema, yielded twin isolates of BTV and EHDV, respectively. Final serotype identification, causal relationship and diagnosis are still pending. These cases amply illustrate the concept that arboviral endemicity can result in a diagnostic dilemma.