PCR monitoring of parasitemia during drug treatment for canine Chagas disease.

Abstract

To date, there is no clear standard to monitor drug treatment for canine Chagas disease. We used 2 real-time PCR (rtPCR) assays targeting Trypanosoma cruzi kinetoplast DNA (kDNA) and nuclear satellite DNA (nDNA) to detect T. cruzi in canine whole blood. Samples were collected randomly from 131 untreated dogs with unknown T. cruzi infection status in Texas. The kDNA-based rtPCR was slightly more sensitive (diagnostic sensitivity of kDNA = 49% vs. nDNA = 44%; p = 0.5732) but slightly less specific (diagnostic specificity of kDNA = 96% vs. nDNA = 97%; p > 0.9999) than the nDNA-based rtPCR. However, the differences in sensitivity and specificity between the nDNA- and kDNA-based rtPCR assays were not statistically significant. Using the nDNA- and kDNA-based qualitative rtPCR assays to monitor parasitemia from 137 itraconazole- and amiodarone-treated cases with nDNA- and kDNA-based PCR-positive baselines showed that the PCR positive rate decreased to 0% in 30 d. Using kDNA-based quantitative rtPCR to monitor normalized T. cruzi DNA copies in 4 representative dogs demonstrated that drug treatment could reduce parasite loads within 7-30 d. The kDNA-based qualitative rtPCR may be used for routine parasitemia screening of drug-treated Chagas-positive dogs, whereas nDNA-based qualitative rtPCR may be used for confirmation.