Evaluation of four coproscopic techniques for detection of small trematode eggs in dog faeces

The study was conducted to evaluate copro-diagnostic techniques for detection of small trematode eggs in dogs. FLOTAC, a novel flotation technique, and DBL, a sieving and sedimentation technique developed at the former Danish Bilharziasis Laboratory (DBL), were compared using 53 subsamples from four copro-positive dogs. Moreover, a modified version of the DBL technique and the Kato-Katz (KK) thick smear were later compared using faecal samples from 21 dogs. The four techniques were pair-wise compared regarding sensitivity, infection intensity and practical applicability. For the former two techniques, egg recovery subsequent to storage and reproducibility were also compared. The DBL technique detected all 53 subsamples positive for small trematode eggs. Based on 17 subsamples, mean infection intensity of 47±49 eggs per gram of faeces (EPG) was detected by the technique. Due to large amount of sediment, examination of a single subsample required an average of 3 hours. The FLOTAC technique was found less sensitive (82%) than the DBL technique and recovered significantly less eggs (4±6 EPG). Both sensitivity and intensity were further reduced following storage. As the FLOTAC technique requires specialised equipment, safety disposal and personal protective equipment, it was found less suited than the DBL technique for a basic laboratory. Additionally, poor reproducibilities were found for both the DBL and FLOTAC techniques (30±15% and 38±33%, respectively). Based on the 21 faecal samples, the modified version of the DBL technique was found more sensitive (85%) than the KK technique (68%), whereas egg counts were significantly higher for the latter (23±26 EPG vs. 482±909 EPG). By modifying the DBL technique, it was possible to diminish the retained sediment and examination time to a maximum of an hour, which was also the time required by the KK technique, although the latter was faster and more easily processed. Based on the results obtained in this study, none of the techniques evaluated were found applicable in their current form for detection of small trematode eggs in faeces from dogs in Vietnam.