Spotted fever group rickettsiae in Dermacentor variabilis from Cape Cod, Massachusetts.

Spotted fever group (SFG) rickettsiae were identified by indirect immunofluorescent antibody tests in 1.1% of 6,956 specimens of Dermacentor variabilis collected on Cape Cod, Massachusetts. Forty-one of 45 rickettsial isolates were serotyped as Rickettsia montana, one as Rickettsia rickettsii, and three were unidentified. Studies of canines and humans with clinical evidence of spotted fever, and of healthy dogs with antibody to SFG rickettsiae, indicated that exposure of the canine population to R. montana was common but that R. montana was not involved in the etiology of spotted fever.

Natural infection of dogs on Cape Cod with Rickettsia rickettsii.

Four isolates of rickettsiae from sick dogs on Cape Cod, Mass., were serologically identical to isolates of Rickettsia rickettsii from human patients with Rocky Mountain spotted fever. The antigenic analysis used the indirect fluorescent-antibody test and antisera prepared in mice to each of the isolates and to reference strains of R. rickettsii and Rickettsia montana. Serological responses of infected dogs were specific for R. rickettsii, although antibodies to R. montana were also detected in the sera of most of the canines.

An indirect immunofluorescent test for human antibodies to tetanus toxoid using an insoluble toxoid as antigen.

An indirect fluorescent antibody (FA) test for detection of human antibodies to tetanus toxoid is described using an ethylchloroformate-prepared polymer of tetanus toxoid as the particulate slide test antigen. Titres of the FA test were compared with those obtained with the toxin neutralization (TN) test in mice. No antisera were FA-positive at less than 0-0025 AU/ml. Positive correlation of the FA test with the TN test was 50% between 0-0025 and 0-01 antitoxin units/ml (AU/ml) and 100% between 0-02 and 160 AU/ml. In general, an increase in FA titres correlated with an increase in TN titres beginning at about 0-08-0-16 AU/ml.