Recently, a high prevalence of infection by the liver fluke Amphimerus spp. has been documented
in the Chachi Amerindians of Ecuador. For diagnosis, no studies exist that compare
the sensitivity of different coproparasitological detection techniques. The present study compares
the Kato-Katz technique with three other coproparasitological methods for detecting
eggs of Amphimerus in stools, as well as determines the prevalence of infection in Chachi
residents in a Tropical rain forest area in the northwest coast of Ecuador.
A total of 105 samples, utilizing the Kato-Katz technique (KK), the spontaneous sedimentation
technique in tube (SSTT), the formalin-ether concentration technique (FEC), and direct
smear microscopy (DM), were examined. Combining the four methods (fixed ªgoldº standard),
38 samples were positive with a prevalence of infection of 36.2%. The sensitivities of
individual methods were 71%, 58%, 50% and 3% for KK, SSTT, FEC, and DM respectively.
Our results indicated that KK alone had the best performance, detecting 27 (71%) of the 38
positive samples. The combination of KK and SSTT detected amphimeriasis in 36 (95%)
samples, and KK and FEC in 31 (82%) samples.
DM showed the lowest sensitivity, which raises concern for its value, because it is the standard
technique for stool examination for detection of parasites in both public and private
laboratories in Ecuador. SSTT alone detected eggs in 22 samples (58%) and would be recommended
for field studies because of its simplicity. Performing two techniques on a single
sample enhances the detection of Amphimerus infection. Its sensitivity is relative to a fixed ªgoldº standard, determined as the combined results of the four techniques performed. This
study confirms the high prevalence of human infection by Amphimerus in the indigenous
Chachi group where the first human cases were described.
Calvopina M, Romero-Alvarez D, Diaz F,
Cevallos W, Sugiyama H (2018) A comparison of
Kato-Katz technique to three other methods for
diagnosis of Amphimerus spp. liver fluke infection
and the prevalence of infection in Chachi
Amerindians of Ecuador. PLoS ONE 13(10):