CLINICAL PRESENTATION OF EXPERIMENTALLY-INDUCED RABIES IN HORSES

Twelve naive and nine test-vaccinated horses which developed clinical signs of rabies as a result of the required protocol of a vaccine tria l were prospectively observed. Nineteen of the 21 cases were confirmed positive for rabies infection of the brain by fluorescent antibody te st. The two horses with negative results had ganglioneuritis of the tr igeminal ganglion or lymphocytic perivascular cuffing in the brain ste m in addition to clinical signs. Average incubation period was 12.3 da ys and average morbidity was 5.5 days. Naive animals had significantly shorter incubation and morbidity periods (P < 0.05). Muzzle tremors w ere the most frequently observed (81 %) and most common initial sign. Other common signs were pharyngeal spasm or pharyngeal paresis (71 %), ataxia or paresis (71 %), lethargy or somnolence (71 %). The furious form was manifested in 43 % of rabid horses and some of these furious animals initially manifested the dumb form. The paralytic form was not observed. Histopathology was characteristic for rabies. The results o f this trial do nor reflect on the efficacy of commercially licensed e quine rabies vaccines.