犬のサルモネラに関する研究 [in Japanese] Studies on Salmonella in Dogs [in Japanese]
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With the progress of studies on salmonellosis in man and animals, healthy animals have been subjected to inspection for possibility of retaining Salmonella organisms. In the case of dogs, though increasing attention was not payed to salmonellosis, the inspection of Salmonella organisms was carried out in various places and it has been confirmed that dogs possess the Salmonella organisms very often. There are numerous reports referring to the incidence of Salmonella in dogs; in contrast, there have been relatively few studies on the host-parasite relationship and epidemiological significance of the infection. The objects of this study are in the first to know the incidence of Salmonella among dogs in Osaka prefecture and in the second to examine the susceptibility of dogs to Samonella organisms. Taking into consideration the necessity to know the incidence of Salmonella at intervals of time, this inspection was conducted between 1954 and 1960 in apparently healthy stray dogs. In order to study susceptibility of dogs, clinical, bacteriological and serological studies were conducted on the orally inoculated dogs with Sal. typhi murium which was isolated most frequently in this inspection. From the results of these experimental studies, the phenomena of natural infection in stray dogs were discussed. 1. On the distribution of Salmonella among dogs in Osaka prefecture. Materials were mainly collected from mesenteric lymph nodes. Of all 1341 dogs examined, 196 strains of Salmonella were isolated from 188 dogs (14.02%). These strains were divided into 16 serological types. Sal. typhi murium was most frequently isolated, and Sal. potsdam and Sal. thompson fell into next rank. Sal. enteritidis, Sal. give, Sal. newington and Sal. senftenberg were also isolated, but other serotypes were only transiently isolated. Sal. saint paul isolated in 1957, Sal. lomita and Sal. tennessee isolated in 1959 were the serotypes isolated for the first time from both man and animals in our country. 2. The susceptibility of dogs to Salmonella In the laboratory experiment, 60 to 90 days old dogs were orally inoculated with Sal. typhi murium at a rate of 2mg/kg of bodyweight and thorough examinations were made of the re-isolated organisms from excrements, clinical signs, the antibody against the inoculated organisms and distribution of inoculated organisms in various tissues. As a result, there were individually different responses, by which dogs were divided into three groups. In the first group, inoculated organisms disappeared from feces in less than two weeks, dogs manifested no clinical symptoms suggestive of salmonellosis, and the sera of these dogs did not agglutinate the organisms in dilution of 1:10. At autopsy, the lesions were not found and inoculated organisms were not re-isolated. The dogs which fell into this category were predominant. In the second group, it was estimated that the increase in inoculated organisms might take place in the body. These dogs manifested slight clinical symptoms at this time, and then their sera agglutinated inoculated organisms in dilution of 1:40 or more. In the third group, dogs had been weakened at the beginning of the experiment because of infestation by the dog ticks (Haemaphysalis campanulata). These dogs died of septicemia caused by inoculated organisms a few days later. On careful examination of characters of re-isolated Salmonella, it was found that there was increasing tendency for inoculated smooth (S) form organisms to dissociate toward rough (R) form by a series of steps, which resulted in the appearance of intermediate (SR) form which was intermediate between typical S and R both in colony type and virulence. As described above, the agglutinin response of the most dogs to ingestion of Sal. typhi murium was not noticed. In the next step of examination, the demonstration of antibody was attempted by means of indirect bacterial hemagglutination instead of conventional agglutination test. As a result, increase in hemagglutinin titers was observed in all subjects following administration of smaller numbers of viable organisms (Sal. typhi murium) than those in the above experiment. It was also found that the hemagglutinin titers increased for 2 or 5 weeks, then the titers declined, and during increasing period the inoculated organisms were detected in various parts of body such as mesenteric lymph node, tonsils, mandibular lymph nodes, liver, feces and others, while the organisms were not detected during declining period. Subsequently, the examination of possible relation between possession of Salmonella organisms and hemagglutinin titers was conducted on the subjects involving 203 stray dogs. From the results together with the laboratory experiment above-mentioned, it may be concluded that ingested organisms immediately get into mesenteric lymph node and appearance of antibody follows, but that the organisms gradually disappear after 2 or 5 weeks, and that this process takes place repeatedly. As to the infectivity of Salmonella in dogs, though the organisms are endowed with invasiveness, the multiplication of organisms is feeble in the body. At all events, the evidence in which the antibody response takes place suggests that the host-parasite relationship is not saprophytic but of latent infection. If there is no primary factor which produces harmfull effects on barriers within the body, dogs may not fall ill.
- Bulletin of the University of Osaka Prefecture. Ser. B, Agriculture and biology
Bulletin of the University of Osaka Prefecture. Ser. B, Agriculture and biology (18), 73-94, 1966-03-31
University of Osaka Prefecture