IMMUNOLOGICAL PROTECTION AGAINST CANINE HEARTWORM INFECTION

This study was conducted to evaluate protective efficiency of three di fferent protocols for vaccination in canine heartworm infection. To ev aluate the three protocols of immunization, dogs were separately immun ized with living larvae; 1) immunization with gamma-attenuated infecti ve larvae, 2) with 50 mu g/kg ivermectin-abbreviation, and 3) with che mical abbreviation plus Freund's complete adjuvant (FCA). Each group w as composed of two dogs. All dogs used for this study were subcutaneou sly challenged with 100 intact third-stage larvae (L3) various days af ter the last immunization, and the worms in the pulmonary arteries and the right ventricle of the heart were recovered 17 to 25 weeks post-i nfection. The numbers and the sexes of the worms were determined. A me an of 38 worms was burdened in the group immunized with irradiated L3, 36 worms in the chemically-abbreviated group, but 15.5 worms in the g roup with chemical abbreviation plus FCA. The percentages of the prote ction in the former two groups were nearly 50%, but 72.3% in the group with ivermectin plus FCA. The adjuvant enhanced the protective immuni ty against L3 challenge. Obvious eosinophilia was observed in both imm unized and control dogs except for two dogs. There was no correlation between the suppression of eosinophilia and the protective immunity in the present study.