Bluetongue virus serotype 8-associated hydranencephaly in two calves in south-eastern England

Tissues for BTV detection and histopathology were collected immediately after euthanasia for calf 1 and during full postmortem examination on the day after death for calf 2; tissues fixed in formalin were processed routinely for histological examination; the presence of haemosiderin and mineralisation were analysed in selected sections using Perl's Prussian blue and von Kossa methods, respectively. What factors lead to severe damage to the CNS with such consistent pathology in some fetuses but not others infected at a similar stage of gestation is a matter for speculation; the infective dose of virus, the severity of clinical disease in the mothers, the precise timing of transplacental infection, a genetic predisposition, or intercurrent disease are among possible explanations.