Disseminated demyelinating encephalomyelitis occurs not infrequently as a sequel to, or during convalescence from, clinically apparent infection with a number of different viruses, and rarely after vaccination against smallpox, rabies, and other viral diseases. A similar pathological picture characterizes several neurological maladies, for example, multiple and diffuse sclerosis, Schilder's disease, leucoencephalitis, neuromyelitis optica, and a score of other encephalitides, each regarded by the one who first named it as a nosological entity. Several investigators, however, hold that several or all the latter demyelinating affections belong in the same groups of essentially similar histopathological processes (Ferraro (1); Putnam (2); Roizin, Helfand, and Moore (3); and others).Although the problem of the etiology of the demyelinating diseases has been studied during the past century and considerable experimental research has been carried on, there is still no solution. A new impetus, nevertheless, has been the successful experimental production in laboratory animals of neurological syndromes accompanied by histopathological changes in the central nervous system similar to those found in the acute demyelinating affections.The earliest reports of successes were those in 1933-35 of Rivers, Sprunt, and Berry (4) and Rivers and Schwentker (5) who injected monkeys repeatedly over a period of months with brain tissue obtained from apparently normal rabbits. The first paper recorded that of eight animals receiving 14 to 93 intramuscular injections thrice weekly, two reacted with demyelinating encephalomyelitis, one after the 52nd and the other after the 84th inoculation. The second report showed that of eight monkeys similarly treated 46 to 85 times, seven gave positive results. This finding was promptly confirmed by Ferraro and Jervis (6) who introduced rabbit brain into monkeys 29 to 103 times over a period of 112 to 405 days; the animals first showed neurological signs after 3 to 13 months. Ferraro (1) in 1944, concluded that the reaction in the nervous system is of an allergic nature--a view which found active support so that commonly the experimental disease, and occasionally the human acute demyellnating 213 on

INTRODUCTION of concurrent research projects or study facilities of the Division of Veterinary Surveys for selected zoonoses were Medicine, Walter Reed Army Institute of conducted on small wild mammals, ex-Research (WRAIR). These included cluding rodents, located in an undevelop-leptospirosis, listeriosis, rickettsiosis, viral ed forest and swamp area of Aberdeen infections, toxoplasmosis, and filariasis. Proving Grounds, Maryland. Diseases Findings of this extensive study are selected for study were within the scope summarized in this report.

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The spontaneous degeneration of primary dog kidney tissue cultures (DKTC) by infectious canine hepatitis virus (ICH) has been described by Simonyi( 1 ) . In April 1963, a spontaneous cytopathic effect (CPE) , markedly different from that produced by ICH virus, appeared in primary DKTC derived from puppies approximately 2 weeks of age. From these cultures, a transmissible filterable agent was recovered which had many characteristics similar to those recently described for agents isolated from fetal and neonatal puppies( 2-4). This report presents information on the isolation and characterization of this agent as a member of the herpes group of viruses. In addition, serological evidence of its Occurrence in mature dogs is presented.Materials and methods. Tissue cultures. Primary kidney cell cultures of dog, mouse, pig, rat, cow, hamster, horse, and cat and primary embryo cell cultures of mouse, rat, and chicken were prepared from trypsinized cell suspensions. These cells were propagated as monolayers in nutrient fluid consisting of Hanks' balanced salt solution supplemented with 10% heat-inactivated calf serum and 0.5 % lactalbumin hydrolysate. Eagle's minimum essential medium, containing 2 % fetal bovine serum, was used as maintenance medium for the primary cell cultures as well as the following cell strains and lines: L929, human embryonic diploid brain, human embryonic diploid kidney, HeLa and AV-3.t All media contained 100 U of penicillin and 100 pg streptomycin per ml.Plaque formation was tested by inoculat-* Present address: Veterinary Medicine Dept., U.S.