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 trial were prospectively observed. Nineteen of the 21 cases were confirmed positive for rabies infection of the brain by fluorescent antibody test. The two horses with negative results had ganglioneuritis of the trigeminal ganglion or lymphocytic perivascular cuffing in the brain stem in addition to clinical signs. Average incubation period was 12.3 days and average morbidity was 5.5 days. Naive animals had significantly shorter incubation and morbidity periods (P < 0.05). Muzzle tremors were 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 characteristics for rabies. The results of this trial do not reflect on the efficacy of commercially licensed equine rabies vaccines.

Clinical features of experimentally induced rabies in cattle and sheep.

A total of 20 cattle and five sheep out of a larger group of animals that were experimentally challenged with virus as part of the required protocol for a vaccine trial developed clinical signs of rabies. All five sheep and 18 of the cattle tested positive for rabies in a direct fluorescent antibody (FA) test. The remaining two cattle had suspicious FA results. Prospective observations are reported in this study. In the diseased cattle, the average incubation period was 15.1 days and the average morbidity period was 3.7 days. Of those, the naive cattle had significantly shorter incubation and morbidity periods than the test-vaccinated cattle. Major clinical signs included excessive salivation (100%), behavioural change (100%), muzzle tremors (80%), vocalization (bellowing; 70%), aggression, hyperaesthesia and/or hyperexcitability (70%), and pharyngeal paresis/paralysis (60%). The furious form of rabies was seen in 70% of the cattle. In the diseased sheep, the average incubation period was 10.0 days and the average morbidity period was 3.25 days. Major clinical signs included muzzle and/or head tremors (80%), aggressiveness, hyperexcitability, and/or hyperaesthesia (80%), trismus (60%), salivation (60%), vocalization (60%) and recumbency (40%). The furious form of rabies manifested in 80% of the sheep. Current rabies vaccines on the market contain higher effective doses than that utilized for the test vaccine and the results of this study do not reflect in any way on commercially available ruminant rabies vaccines.

Cerebrospinal fluid collection in rats: modification of a previous technique.

Modification of a previously published technique for cerebrospinal fluid collection in rats is described. This technique uses general anesthesia, a supporting platform to flex the head-neck junction, a surgical approach to the dorsal atlanto-occipital region, and a micromanipulator to hold and control the approach of the collection needle. Critical steps for success of the procedure are correct positioning, avoiding premature incision of the subarachnoid space, and alignment of the collection needle with the midline and longitudinal axis of the head. The authors had a 95% success rate in obtaining > 0.1 ml of cerebrospinal fluid, using this technique.