Envenoming following bites by the Balkan adder Vipera berus bosniensis – First documented case series from Bulgaria

We report the first detailed accounts of bites by the Balkan adder, Vipera berus bosniensis from Bulgaria. Documentation of bites by this subspecies is very rare in the literature and most available accounts are from the northern limit of its distribution. V. berus bosniensis is considered to possess neurotoxic venom but little evidence has hitherto been available to support this supposition. In this case series symptoms typical of adder bites developed including oedema, nausea, dizziness, lymphangitis, vomiting, and diarrhoea together with aberrant symptoms such as diplopia and ptosis that confirm the presence of neurotoxic venom in Balkan adders. In addition, unusual and atypical symptoms of adder bites such as painless bites and muscle cramps appeared. The inadequate treatment in hospital and the remote habitats in which this species is encountered are potential sources of complication.