STUDIES ON PSEUDORABIES (INFECTIOUS BULBAR PARALYSIS, MAD ITCH : III. THE DISEASE IN THE RHESUS MONKEY, MACACA MULATTA.

In the monkey (M. mulatto) the virus of pseudorabies, pantropic in the rabbit, behaves as a strict neurotrope. Infection, usually fatal, readily follows intracerebral and intracisternal inoculation of rabbit virus, and often intrasciatic inoculation; the symptomatology of the ensuing disease is described. In a limited number of experiments no infection resulted from intradermal, intramuscular or intravenous inoculation. Nerve and glial cells are primarily attacked by the virus, but no cytological or other evidence of susceptibility of non-nervous tissue or of growth of virus outside the nervous system was obtained. Certain cortical areas, of which the principal are the pyriform area, cornu Ammonis, island of Reil, lower lip of the Sylvian fissure and basal surface of the frontal lobe, are affected far more severely than are other parts of the nervous axis; the reasons for this elective distribution of the most severe lesions, seen alike after intracerebral and intrasciatic inoculation and analogous perhaps to that in poliomyelitis and louping-ill, are not obvious. Other areas of the nervous system are relatively insusceptible to the action of the virus. Cases showing clinically only a febrile reaction without definite nervous symptoms may later exhibit marked residual lesions at the sites of election. The blood and cerebrospinal fluid play no apparent rôle in disseminating the virus, which, after intrasciatic inoculation, spreads upwards by the nervous path. Some suggestion was received from the experiments that in monkeys possessed of immunity to B virus (Sabin and Wright, 1934) pseudorabic infection is less likely to prove fatal than in animals not so immune, but the observations made were insufficiently numerous to be of statistical value. The sera of 6 out of 26 monkeys were found to contain antibodies neutralising B virus; these 6 monkeys were all included in one batch of 7 received at one time from the dealer.