William Cevallos1,3, Manuel Calvopiña2, Victoria Nipáz1, Belén Vicente-Santiago3, Julio López-Albán3, Pedro Fernández-Soto3, Ángel Guevara1,+, Antonio Muro3
1Universidad Central del Ecuador, Centro de Biomedicina, Carrera de Medicina, Quito, Ecuador
2Universidad de Las Américas, Quito, Ecuador
3Universidad de Salamanca, Faculty of Pharmacy, Tropical Disease Research Centre, Group e-INTRO, Salamanca, Spain
BACKGROUND Amphimerus spp. is a liver fluke that infects humans and domestic animals. It is highly prevalent in some Ecuadorian communities. Currently, diagnosis is based on the microscopic observation of eggs in faeces, but this has variable sensitivity. More sensitive methods are needed for diagnostic testing.
OBJECTIVE The main objective of this work was to develop an enzyme-linked immunosorbent assay (ELISA) using crude antigens from Amphimerus spp. adult worms to detect anti-Amphimerus IgG in human sera.
METHODS Crude somatic antigens were obtained from adult Amphimerus spp. worms. Human sera from 119 patients were tested: 48 from individuals with a confirmed Amphimerus spp. infection, 78 from non-infected Ecuadorians living in the endemic region, 60 from persons living in non-endemic areas (20 Ecuadorians, 20 Europeans, and 20 Africans), and 33 who had other parasitic and non-parasitic infections.
PRINCIPAL FINDINGS Results were analysed using the receiver-operator characteristic (ROC) curve analysis with an area under curve (AUC) value of 0.967. The accuracy of the ELISA was high. The sensitivity was 85.0% [95% confidence interval (CI): 80.3-89.7%] and the specificity was 71.0% (95% CI: 65.2-76.8%). Some cross reactivity was detected against Paragonimus mexicanus, Fasciola hepatica, Schistosomiasis, Taenia solium, Strongyloides stercoralis, Mansonella spp., and Vampirolepis nana.
MAIN CONCLUSIONS We have developed the first ELISA technique that detects anti-Amphimerus IgG in human sera with good sensitivity, repeatability and reproducibility. However, more specific antigens are needed to further enhance performance of this assay. Regardless, this ELISA test could be useful for early diagnosis and prompt treatment of human Amphimerus spp. infections.
Financial support: DGIP-Universidad Central del Ecuador (CUP 91750000.0000.37 4072). It was also funded in part by IBSAL-CIETUS, Spain (DTS16/00207, PI16/01784).
Received 20 September 2016
Accepted 24 January 2017