Abstract:

Blood samples were collected from 537 domestic dogs in Wenxian County and Diebu County of Gansu Province, where canine visceral leishmaniasis were endemic, and from 37 domestic dogs from Tianzhu County of Gansu Province, the non-endemic area. Blood examination was carried out using three immunochromatographic test strips including human rk39 strip, canine rk39 strip and circulating antigen (CA) strip in parallel to assess the sensitivity and specificity of the methods, and using PCR assay as the standard to compare with. The results showed that among the total 574 dog blood samples, 221 samples were tested Leishmania positive by PCR with the positive rate of 38.5% (221/574). Examining the 221 positive samples with CA strip, the human rk39 strip and canine rk39 strip, the sensitivity was found of 90.0% (199/221), 65.2% (144/221) and 64.3% (142/221), respectively, all of which significantly differed from that of PCR method (χ² = 141.76, 20.31, and 17.96, P < 0.05). The specificity of CA test strip and the two rk39 test strips in testing the blood samples of 316 dogs without Leishmania infection from the endemic areas was 95.3% (301/316), 99.7% (315/316) and 99.4% (314/316), respectively, all of which significantly differed from that of the standard (χ² = 258.85, 312.01, and 308.05, P < 0.05). The positive-result coincidence rate of the CA strip and the canine and human rk39 strips with PCR in dogs with symptoms from the endemic areas was 88.5% (23/26), 88.5% (23/26) and 84.6% (22/26), respectively, all of which significantly differed from that of the PCR method (χ² = 23.22, 23.22, and 20.50, P < 0.05). The positive-result coincidence rate of CA test strip and the canine and human rk39 test strips with PCR in dogs without symptoms in the endemic areas was 91.8% (179/195), 62.1% (121/195) and 61.5% (120/195), respectively, all of which significantly differed from that of the PCR method (χ² = 136.25, 11.33, and 10.39, P < 0.05). Area under the curve (AUC) analysis was used to assess the method accuracy, showing the AUC value of all the 3 methods was above 0.8. The kappa consistency coefficient was 0.671-0.857, indicating that all of the three test strips are applicable for preliminary screening of Leishmania-infected dogs. The CA test strip is superior to the two rk39 test strips and could be a good method for screening Leishmania-infected dogs in endemic areas.

Key words: Leishmania, Immunochromatographic strip, Dog, Performance evaluation, Gansu Province