Immunization in Rats Against Trichinella Spiralis

Abstract

Attempts were made to immunize 35 white rats against Trichinella spiralis by way of the mouth.

These rats were formed into 3 groups, fed respectively on (1) trichina antiserum, (2) well-ground dehydrated trichina powder and (3) consecutive feedings of increasing doses of infested meat. A fourth group of 12 rats were injected intraperitoneally with varying amounts of Coca's alkaline suspension of trichina powder, as another possible method of protection against otherwise lethal doses of trichinous meat. Simultaneously, a series of normal rats were used as controls. A total white blood count and differential were made in each of the 47 rats every second day, and symptoms were observed and recorded.

In Group One, each 3-month-old rat was fed from 6 to 9 cc. of rabbit antiserum (titer 1–10,000) and convalescent serum from trichinous hogs (negative titer) 24 hours before feeding them with the infested meat. Neither serum gave protection; rats died as early as the sixth and as late as the sixtieth day after infestation, all, including the normal serum controls, suffering from severe symptoms. No rat that died before the twentieth day after infestation showed an eosinophilic increase; 2 that lived for 60 days showed an eosinophilic count of 11% and 14%, which occurred on the thirty-second and the thirty-fourth day, respectively. Muscle larvae were found only in those rats that died after the twentieth day of infestation.

In Group Two, rats 3½ monts old were fed with the fine dehydrated trichina powder over a period of 4 days before and for 20 days after feeding them with trichinous meat, which gave no protection. A lethal dose (5 gm. of meat with an average of 5 worms per low power field) was given to each rat, producing in each severe symptoms and death before the forty-fourth day.