DIETHYLCARBAMAZINE-INDUCED DIROFILARIA-IMMITIS LARVAL DEATH, AS INDICATED BY IMMUNOGLOBULIN-E CONCENTRATION, IN DOGS WITH CONCURRENT ANCYLOSTOMA-CANINUM INFECTION

Immunoglobulin E is produced in response to parasitic nematodes that u ndergo blood and tissue migrations. Results of our previous studies in dicated that IgE and IgG respond to Dirofilaria immitis in experimenta lly infected dogs. To determine the association between treatment with the larvicide, diethylcarbamazine (DEC), and antibody responses and t o examine the potential influence of infection with a nonfilarid intes tinal nematode on isotype-specific immune responses, we monitored, by use of isotype-specific ELISA, separate IgE and IgG responses against D immitis in 4 groups (A-D) of 8 dogs experimentally coinfected with D immitis and Ancylostoma caninum. AU dogs were monitored from 2 weeks before inoculation with D immitis, through postinoculation (PI) week 2 0. Group-B dogs received a daily regimen of 6.6 mg of DEC/kg of body w eight. Group-C dogs received 4.95 mg of oxibendazole/kg daily. Group-D dogs received Dec and oxibendazole, equivalent to the daily doses giv en to dogs of groups B and C. All dogs given oxibendazole had no A can inum at necropsy. Of the groups receiving Dec, 3 group-B dogs each had 1 to 2 D immitis at necropsy. When results of chronologic IgE determi nation for all groups were statistically compared, only groups B and C had significant (P = 0.0148 and P << 0.00005, respectively) increases in IgE values. Group-C dogs had the highest IgE values from PI week 1 0 until the end of the study, whereas IgG values were statistically id entical to those of group-A dogs. Group-B dogs given only Dec and havi ng the least number of D immitis of all groups, had IgE values that pe aked at PI week 6; values were significantly (P = 0.0002) higher than those for all other groups. In Group-B dogs, IgG values increased sign ificantly (P << 0.00005) only at PI week 20 and were significantly (P << 0.00005) decreased after PI week 6, compared with values for all ot her groups. Group D containing 6 dogs infected with 1 to 18 D immitis found at necropsy had IgE values between those of group-B dogs and tho se of non-DEC-treated groups at PI week 6. There was no difference in IgG values between 3 groups at PI week 6, and IgE values were found to be a better correlator than were IgG values to the number of D immiti s larvae killed in the tissues during this period. AU differences in I gG and IgE values not only correlated with treatment status and number of D immitis adults found at necropsy, but also with the developmenta l stage of D immitis commonly present in the groups at each time point and the number of adult D immitis found at necropsy.