GAMMA-CAMERA SCINTIGRAPHY FOR DIRECT VISUALIZATION OF LARVAL MIGRATION LN STRONGYLOIDES STERCORALIS-INFECTED DOGS

Gamma camera scintigraphy of dogs infected with radiolabeled third-sta ge larvae of Strongyloides stercoralis was successful for visualizing larval migration in a live host. Ten-day-old pups were infected subcut aneously in a lateral inguinal site with 100,000 Se-75-selenomethionin e-labeled third-stage S. stercora lis and imaged serially using a clin ical gamma camera during the prepatent period. Radioactivity correspon ding to the larval inoculum was visualized at the infection site immed iately after injection. Radioactivity spread diffusely, corresponding to radial dispersal of larvae from the infection site. The majority of the radioactivity concentrated over or through the abdomen from 48 to 144 hr after infection. Larvae arrived in the small intestine in numb ers adequate for visualization beginning at 114 hr after infection. At no time was there concentration of radioactivity associated with the lungs of an infected pup. A control pup injected only with Se-75-selen ometkionine showed uniform activity diffusely throughout the entire bo dy at all times. We concluded that the majority of larvae moved to the gut by means other than the pulmonary route.