Search

1. Results of cross agglutination-lysis and cross agglutinin-absorption studies indicate that the etiologic agent of Fort Bragg Fever is closely related to the other members of the leptospiral serogroup autumnalis. 2. Agglutinin-absorption studies with all members of the serogroup autumnalisreveal that the agglutinins responsible for strain specificity are not completely removed when absorbed with any of the other strains. 3. Classification of these leptospiral strains on the basis of a modified adoption of Wolff's scheme(5) designates autumnalisAkiyami A as the “incomplete” biotype of the Fort Bragg isolate and discloses L. autumnalisA Rach-mat, in addition to L. bangkinang, as a heterologous serotype member of the autumnalis group. 4. The Fort Bragg isolate is therefore designated as L. autumnalis, Fort Bragg.

The results of agglutinationlysis, absorption, and animal protection tests indicate that the strains of bovine leptospira of American origin designated as New Jersey C164 and New York A are indistinguishable from L. pomona.These findings stress the need for reclassification of the American strains. They also indicate that L. pomonaor an antigenically indistinguishable organism is present in North America.

A soluble, specific complement-fixing antigen, or antigen complex, was demonstrated in the organism-free culture liquor of each leptospiral strain studied. The antigenic material is heat stable and nonprotein in nature. The antigens are present in amounts which make feasible their employment in serological investigations of the leptospiroses.

Eight strains of leptospirae were examined by electron microscopy. NO morphological differences were fcound between strains. All strains possessed an axial filament. Diameter of the strains was approximately 0.1 μ, lengths varied from 6 to more than 15 μ.

A transmissible agent (MHG) with biological and physical properties similar to the viruses of the enterovirus group has been isolated from pooled tissues of 3 white rats, Sprague-Dawley strain, obtained from the Walter Reed Army Institute of Research animal colony. The agent produced fatal infections in both suckling rats and suckling mice when inoculated intracranially. A high incidence of complement-fixing antibodies against the new virus was found in adult human sera. The relationship of this virus to disease in man or animal has not been ascertained.

A transmissible agent was recovered from primary DKTC which developed a spontaneous CPE. Characterization and serological studies of the virus indicated that the virus was a new member of the herpes virus group.

A method for the preparation of macroscopic leptospiral agglutinating antigens is described. Antigens of this type have been prepared from 9 leptospiral serotypes. Cross reaction patterns are essentially comparable to those observed in the agglutination-lysis technic. Antigens so prepared are sensitive, specific, and stable under protracted periods of storage, and produce easily discernible reactions in the presence of antibodies.

Evidence has been brought forward to indicate that Columbia SK, Columbia MM, Mengo encephalomyelitis and encephalomyocarditis viruses agglutinate sheep red cells. It is therefore possible to identify these viruses by means of hemagglutination and to measure the antibody content of antisera. Since the viruses show characteristic spontaneous elution or dispersion from the erythrocytes, the method can be used for purposes of selective adsorption of the viruses without loss of their hemagglutinative activity. Moreover, the uniformity of the hemagglutination reaction shown by the 4 viruses and the cross-inhibition that exists among them supports the findings of Warren and Smadel6and of Dick7that these viruses are similar in many repects and are of the same group.Seventeen other neurotropic viruses were tested for their capacity to agglutinate characteristically erythrvcytes deriving from sheep, man (group O), chicken, horse, hamster, dog, cat and guinea pig; these tests failed.Another phenomenon that was observed is the nonspecific agglutination of dog, cat and guinea pig erythrocytes by normal or virusinfected mouse brains. With respect to agglutination of hamster cells, an inhibitor of agglutination is present not only in suspensions of normal mouse brain but also in normal serum and antiserum against the neurotropic viruses.The fact that neurotropic viruses are often used in the form of mouse brain suspensions renders it important therefore for investigators to use proper controls for the variable of the test and, in addition, to identify positive reactions by specific means.

Japanese encephalitis virus in 20% suspensions of infected chick-embryo tissues may be partially purified by adsorption of inert material on particles of Attaclay SF, a naturally-occurring sorptive clay of exceedingly small pore diameter. Removal of about 75% of the nitrogen content of a crude virus suspension may be accomplished without a prohibitive loss of infectivity.

Serological and cultural studies for leptospirosis were conducted on 37 opossums trapped at a military reservation at Aberdeen, Md. Five of the 37 animals were serologically positive. Questionable reactions were seen in serums from 9 other animals. Two isolates were obtained and identified as Leptospira ballumand L. icterohaemorrhagiae, respectively. L. icterohaemorrhagiaein an opossum had not heretofore been reported. The antigenic interrelationships among the “complete” and “incomplete” bio-types of L. icterohaemorrhagiaeand L. mankarso, disclosed in the serologic studies, differed from previously reported findings.

The tissues of chick embryos dead or dying following infection with the virus of Japanese encephalitis are significantly lower than normal in pentose concentration but no significant differences in desoxyribonucleic acid concentration were demonstrated. The factors responsible for the decrease in pentose have not been elucidated.

Two-day-old chicks uniformly developed leptospiremia persisting for at least 5 days following intraperitoneal inoculation of leptospires. No clinically detected illness resulted from this infection nor was there constant significant serologically demonstrable antibody response. Employment of chicks for recovery of leptospires form materials contaminated with other microorganisms and hence unsuitable for direct culture is suggested.

The production in monkeys of acute disseminated encephalomyelitis accompanied by demyelination following injection of brain tissue, first achieved by Rivers. Sprunt and Berry.1was not only confirmed by others, but similar lesions were later obtained with various preparations in rabbits and guinea pigs. The experimental disease has not hitherto been induced in mice. It would appear that if mice so convenient for experimental work could be shown to be susceptible, a step forward might be made. As the following results will show, it is believed that this has been accomplished.

In a search for wildlife carriers of L. pomona, various species of mammals were trapped in an endemic area of bovine leptospirosis. Direct dark-ground microscopic examinations of urine or bladder saline washings disclosed the presence of leptospires in 10 of the 37 house mice examined. Leptospiral cultural isolates were obtained from 9 of these 10 house mice. The recovery of leptospires from 6 additional house mice and from 1 of 2 opossums emphasizes the importance of cultural methods in any survey for leptospirosis. All isolates, serologically typed on the basis of a cross agglutinationlysis pattern, employing 18 type leptospiral immune rabbit serums, belonged to the serotype L. ballum. The failure to detect L. pomona in the rodent and other wild life population in an endemic area of bovine leptospirosis affords ancillary evidence that the natural hosts of L. pomonaleptospirosis are to be found primarily in the livestock population. To the authors' knowledge, this is the first report of leptospirosis in the opossum.