1/2. encephalitis and chorioretinitis associated with neurotropic African horsesickness virus infection in laboratory workers. Part I. Clinical and neurological observations.Four laboratory workers from the same vaccine-packing facility developed at different times over an 8-year period an illness characterised by encephalitis (in 3 workers) and uveochorioretinitis (in 4). Low complement fixation titres were detected in all 4 patients to African horsesickness (AHS) virus and enzyme immunoassay and plaque reduction neutralising tests were positive, the latter against both serotypes 1 and 6. Five of 15 laboratory workers from the same facility who were healthy on clinical and ophthalmological examination showed positive plaque reduction neutralising tests but none to both serotypes 1 and 6. It is postulated that the encephalitis with the predominant temporal lobe involvement was caused by an airborne transnasal route of infection of the neurotropic AHS virus released in dried powder form, secondary to the accidental breaking of vaccine bottles. This is possibly the first report of subclinical and probable clinical neurotropic AHS infection in man. ( info) |
2/2. encephalitis and chorioretinitis associated with neurotropic African horsesickness virus infection in laboratory workers. Part II. Ophthalmological findings.Four laboratory workers developed uveitis-chorioretinitis, associated with encephalitis in 3 cases. The retinitis was characterised by haemorrhages and areas of retinal oedema, most marked over the posterior polar regions, and was associated with exudative retinal detachments. The lesions progressed over weeks and showed a severe retinal arterial vasculopathy with arteriolar narrowing, ghost vessel formation and the development of optic atrophy. The picture in 2 of the patients resembled that of the acute retinal necrosis syndrome (ARN). antibodies to African horsesickness (AHS) virus were detected. The serology for AHS virus was positive in all 4 patients as well as in 5 of 15 laboratory workers from the same facility who were clinically and ophthalmologically normal. This is to our knowledge the first description of subclinical and probable clinical neurotropic AHS virus infection in man. AHS is a hitherto-unrecognised possible cause of viral retinitis and the ARN syndrome. ( info) |