Comparison of Nutrient Agar Plate Culture and Formalin-Ethyl Acetate Concentration Methods in Diagnosis of Human Trichostrongyliasis

Trichostrongylus spp. are common parasites of herbivorous animals and trichostrongyliasis is an important zoonotic disease in Iran, especially in northern Iran. Routine laboratory methods for diagnosis of these infections are direct smear and formalin-ethyl acetate techniques. There is no enough evidence about the sensitivity of nutrient agar plate culture for detection of Trichostrongylus spp infections. The objective of this study was to compare the nutrient agar plate culture and the formalin-ethyl acetate sedimentation techniques for laboratory diagnosis of human trichostrongyliasis in an endemic area of northern Iran. A total of 1553 fresh stool samples were collected from residents of 31 villages within the Fouman district in Guilan province during 2015–2016. All samples were examined using nutrient agar plate culture and formalin- ethyl acetate concentration techniques for detection of Trichostrongylus spp. infections. Overall, 71 cases were diagnosed with Trichostrongylus spp. by at least one of the methods. Considering parasitological results as the diagnostic gold standard, the sensitivity and specificity of nutrient agar plate culture were 90.1% and 100%, respectively. Also, the sensitivity and specificity of the formalin ethyl acetate concentration method were 95.8% and 100%, respectively. According to the results of this study, the formalin ethyl acetate method is more sensitive than nutrient agar plate culture in the diagnosis of human trichostrongyliasis, especially in humid climate regions such as North of Iran.