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Studies on the Causative Agent of ^|^ldquo;Hyuganetsu^|^rdquo; Disease

1973; Volume: 47; Issue: 12 Linguagem: Inglês

10.11150/kansenshogakuzasshi1970.47.474

1884-569X

Takeo Fukuda, Tohoru SASAHARA, Tadatoshi KITAO,

Mosquito-borne diseases and control

Hyuganetsu disease was caused by ingestion of raw gray mullet, indicating an endoparasite-born rickettsios is.Attempts were made to isolate causative rickettsia from the parasites of the fish. Metacercaria of Stellantchasmus falcatus, homogenized or untreated, were inoculated into mice via peritoneal or oral routes. The mice were autopsied after 14 days and 30 days, respectively, and thereafter blind passages were done every 14 days with spleen homogenate. Four strains of rickettsia-like organisms were isolated by the former procedure and 6 by the latter.These rickettsia-like isolates were studied for its characteristics comparing with Rickettsia sennetsu. They shared common morphological, biological and antigenic properties on the one hand such as:1. They were visualized by Macchiavello staining of lymph node cells of infected mice; coccoid and pleomorphic.2. They were unfiltrable through Chamberland L3 filters.3. They were sensitive to heat treatments (50°C, 10 minutes), formalin (0.1%, 3 hours), phenol (0.5%, 3 hours) and ether (10%, 30 minutes).4. They were sensitive to antibiotics.5. The isolates were positive for direct immunofluorescence test with labelled anti-Rickettsia sennetsu antibody or for indirect method with convalescent patient serum of “Hyuganetsu” disease and labelled anti-human-γ-globulin antibody, and Rickettsia sennetsu was also positive for indirect method using convalescent mice serums infected with the isolates and labelled anti-mouse-γ-globulin antibody.However, the pathogenicity and some other characteristics distinguished them from Rickettsia sennetsu on the other:1. They did not kill mice while Rickettsia sennetsu did in 14 days.2. Autopsy of the infected mice revealed no viscous exudate in the peritoneal cavity.3. Mice immunized with the isolates acquired only a little cross immunity against Rickettsia sennetsu infection.The possibility that the metacercaria of Stellantchasmus falcatus may carry Rickettsia sennetsu as well as the rickettsia-like organism is not inconceivable in the light of the fact that Nanophyetus salmincola, the vecter of salmon disease complex in dogs, can be concurrently infected with Neorickettsia helminthoeca and Elokomin fluke fever agent.