The Right Tool for the Job: Detection of Soil-Transmitted Helminths in Areas Co-endemic for Other Helminths

Abstract

BackgroundDue to the recent increased use of the McMaster (MM) fecal egg counting method for assessing benzimidazole drug efficacy for treating soil-transmitted helminth (STH) infections, the aim of the current study was to determine the operational value of including the MM method alongside the Kato-Katz (KK) fecal thick smear to increase the diagnostic sensitivity when STHs are co-endemic with trematode helminths (e.g., Schistosoma mansoni).MethodsA cross-sectional study was conducted in school-aged children aged 4-18 years in the northeastern region of the State of Minas Gerais (Brazil), where Necator americanus, Ascaris lumbricoides, Trichuris trichiura, and S. mansoni are co-endemic. One fecal sample from each participant was collected and transported to the field laboratory for analysis. Coprological diagnosis was performed on each fecal sample by three different methods: Formalin-Ether Sedimentation (FES), KK and the MM technique. The diagnostic sensitivity and negative predictive value (NPV) of each technique was calculated using the combination of all three techniques as the composite standard. In order to determine the agreement between the three techniques Fleiss´ kappa was used. Both the Cure Rate (CR) and the Fecal Egg Count Reduction (FECR) were calculated using the two quantification techniques (i.e., the MM and KK).ResultsFecal samples from 1260 children were analyzed. The KK had higher diagnostic sensitivity than the MM for the detection of both A. lumbricoides (KK 97.3%, MM 69.5%) and hookworm (KK 95.1%, MM 80.8%). The CR of a single dose of mebendazole varied significantly between the KK and MM for both A. lumbricoides (p = 0.016) and hookworm (p = 0.000), with lower rates obtained with the KK. On the other hand, the FECR was very similar between both techniques for both A. lumbricoides and hookworm.ConclusionThe MM did not add any diagnostic value over the KK in areas where both STHs and trematodes were co-endemic. The lower sensitivity of the MM would have an important impact on the administration of selective school-based treatment in this area since if only the MM were used, 36 (13.9%) children diagnosed with A. lumbricoides would have gone untreated.

Hygienic Behaviors and Risks for Ascariasis among College Students in Kabul, Afghanistan

“…We also focused on university students, who as an age group are at high risk for infection, but who are likely to be economically privileged compared with young adults who are not attending university. Additionally, ascertainment of ascariasis was through microscopy, other methods such as the Kato-Katz technique and polymerase chain reaction are more sensitive and have higher negative predictive value, 20 and we cannot discount the possibility of miscategorizing other parasitic infections as ascariasis. The Kato-Katz stain was not available at KMU during the study period.…”

Kato-Katz and Lumbreras rapid sedimentation test to evaluate helminth prevalence in the setting of a school-based deworming program

“…20 However, as we demonstrated, the sensitivity of one Kato-Katz test is noticeable low when the burden of STH infections is low. 10 In addition, the loss in sensitivity when performing a single test compared to performing three tests was more for the KatoKatz than for the Lumbreras test in our low burden setting.…”

Assessing stool quantities generated by three specific Kato-Katz thick smear templates employed in different settings

“…The Kato-Katz technique is recommended for quantitative diagnosis in epidemiological surveys, drug efficacy trials and sentinel surveillance of helminthiases control programmes [ 11 , 28 ]. Its application has a several decade long history [ 29 – 32 ], but the validity of the 41.7 mg of stool that reportedly fit into the widely distributed standard plastic templates and the recommended multiplication factor of 24 has, to our knowledge, yet to be assessed. Here, we investigated the comparability of the average amount of faeces generated by three Kato-Katz templates from two providers to derive evidence for their application with the recommended standard multiplication factor of 24 to calculate EPG.…”