Morphological diversity of Trichuris spp. eggs observed during an anthelminthic drug trial in Yunnan, China, and relative performance of parasitologic diagnostic tools.

The presence of large Trichuris spp. eggs in human faecal samples is occasionally reported. Such eggs have been described as variant Trichuris trichiura or Trichuris vulpis eggs. Within the frame of a randomised controlled trial, faecal samples collected from 115 Bulang individuals from Yunnan, People's Republic of China were subjected to the Kato-Katz technique (fresh stool samples) and the FLOTAC and ether-concentration techniques (sodium acetate-acetic acid-formalin (SAF)-fixed stool samples). Large Trichuris spp. eggs were noted in faecal samples with a prevalence of 6.1% before and 21.7% after anthelminthic drug administration. The observed prevalence of standard-sized T. trichiura eggs was reduced from 93.0% to 87.0% after treatment. Considerably more cases of large Trichuris spp. eggs and slightly more cases with normal-sized T. trichiura eggs were identified by FLOTAC compared to the ether-concentration technique. No large Trichuris spp. eggs were observed on the Kato-Katz thick smears.