The performance of Fas2-ELISA for the diagnosis of Fasciola hepatica infection in children living in areas of high endemicity for fascioliasis in the Peruvian Andes is analyzed. Fas2-ELISA is based on the detection of circulating IgG antibodies elicited in infected individuals against a F. hepatica antigen termed Fas2. The study was conducted in three Andean localities, Huertas-Julcan in Junin, Asillo in Puno, and Cajamarca, with a total population of 634 children in an age range 1 to 16 years old. Child fascioliasis prevalence was 21.1% in Huertas-Julcan, 25.4% in Asillo, and 24% in Cajamarca, estimated by coprological inspection. The seroprevalence of F. hepatica infection, determined by Fas2-ELISA, was 27.8% in Huertas-Julcan, 44.6% in Asillo, and 29.1% in Cajamarca. The overall sensitivity of Fas2-ELISA was 92.4%, the specificity 83.6%, and the negative predictive value 97.2%. No association between OD₄₅₀ Fas2-ELISA and infection intensity measured by egg counting was observed. Results show that Fas2-ELISA is a highly sensitive immunodiagnostic test for the detection of F. hepatica infection in children living in human fascioliasis endemic areas.

Emergence of human fascioliasis prompted a worldwide control initiative including a pilot study in a few countries. Two hyperendemic areas were chosen: Huacullani, Northern Altiplano, Bolivia, representing the Altiplanic transmission pattern with high prevalences and intensities; Cajamarca valley, Peru, representing the valley pattern with high prevalences but low intensities. Coprological sample collection, transport and study procedures were analyzed to improve individual diagnosis and subsequent treatments and surveillance activities. Therefore, a coproantigen-detection technique (MM3-COPRO ELISA) was evaluated, using classical techniques for egg detection for comparison. A total of 436 and 362 stool samples from schoolchildren of Huacullani and Cajamarca, respectively, were used. Positive samples from Huacullani were 24.77% using the MM3-COPRO technique, and 21.56% using Kato-Katz. Positive samples from Cajamarca were 11.05% using MM3-COPRO, and 5.24% using rapid sedimentation and Kato-Katz. In Huacullani, using Kato-Katz as gold standard, sensitivity and specificity were 94.68% and 98.48%, respectively, and using Kato-Katz and COPRO-ELISA test together, they were 95.68% and 100%. In Cajamarca, using rapid sedimentation and Kato-Katz together, results were 94.73% and 93.58%, and using rapid sedimentation, Kato-Katz and copro-ELISA together, they were 97.56% and 100%, respectively. There was no correlation between coproantigen detection by optical density (OD) and infection intensity by eggs per gram of feces (epg) in Cajamarca low burden cases (<400 epg), nor in Huacullani high burden cases (≥400 epg), although there was in Huacullani low burden cases (<400 epg). Six cases of egg emission appeared negative by MM3-COPRO, including one with a high egg count (1248 epg). The coproantigen-detection test allows for high sensitivity and specificity, fast large mass screening capacity, detection in the chronic phase, early detection of treatment failure or reinfection in post-treated subjects, and usefulness in surveillance programs. However, this technique falls short when evaluating the fluke burden on its own. A coproantigen-detection technique (MM3-COPRO ELISA) was evaluated in 436 and 362 schoolchildren of Huacullani, Bolivia, and Cajamarca valley, Peru, respectively. Classical techniques for egg detection were used for comparison. In Huacullani, using Kato-Katz as gold standard, sensitivity and specificity were 94.68% and 98.48%, respectively, and using Kato-Katz and COPRO-ELISA test together, they were 95.68% and 100%, respectively. In Cajamarca, using rapid sedimentation and Kato-Katz together, these results were 94.73% and 93.58%, respectively, and using rapid sedimentation, Kato-Katz and copro-ELISA together, results were 97.56% and 100%, respectively. There was no correlation between coproantigen detection by optical density (OD) and infection intensity by eggs per gram of feces (epg) in Cajamarca low burden cases (<400 epg), nor in Huacullani high burden cases (≥400 epg), although there was in Huacullani low burden cases (<400 epg). Six cases of egg emission appeared negative by MM3-COPRO, including one with a high egg count (1248 epg). The coproantigen-detection test allows for high sensitivity and specificity, fast large mass screening capacity, detection in the chronic phase, early detection of treatment failure or reinfection in post-treated subjects, and usefulness for surveillance programs. However, this technique falls short when evaluating the fluke burden on its own.

We conducted a case-control study to clarify the risk factors for human fascioliasis in the Northern Peruvian Altiplano. Cases (n=61) were individuals who were diagnosed as having chronic fascioliasis by faecal and/or serologic (Fas2-ELISA) studies. Controls (n=61) had negative serologic and coprological results for Fasciola hepatica. We identified an association between fascioliasis and four variables (40 analysed): the habit of drinking alfalfa juice (OR=4.5; 95% CI 1.8-11.1; P<0.001); familiarity with aquatic plants (OR=4.3; 95% CI 1.8-10.6; P<0.001); dog ownership (OR=5; 95% CI 1.7-15.1; P=0.002); and raising more than five sheep (OR=0.3; 95% CI 0.1-0.8; P=0.01). According to clinical presentation and laboratory studies, dizzy spells (P=0.01), history of jaundice (P=0.01), peripheral eosinophilia (P=0.005) and Ascaris lumbricoides in stools (P=0.001) were associated with fascioliasis. The principal exposure factor for F. hepatica infection was drinking alfalfa juice. In conclusion, we suggest that human fascioliasis in Peru should be suspected in patients from livestock-rearing areas, who present with recurrent episodes of jaundice and who have a history of consumption of alfalfa juice or aquatic plants, or who have eosinophilia.

The immunodiagnosis of human infections with Fasciola hepatica using purified parasite cysteine proteinases as antigens is reported in this paper. IgG enzyme-linked immunosorbent assays (ELISAs) with 2 cysteine proteinases of 26 kDa (Fas1) and 25 kDa (Fas2), obtained from the regurgitated material of adult worms, were evaluated with serum samples from 38 patients infected with F. hepatica, from 54 patients with other parasitic infections and from 46 healthy volunteers. The diagnostic sensitivities for detection of F. hepatica infection at a serum dilution of 1 in 500 were 89% and 95% with Fas1 and Fas2 respectively. The specificity of the ELISAs was 98% for Fas1 and 100% for Fas2. IgG ELISA with Fas2 is a highly sensitive and specific assay for the immunodiagnosis of human fascioliasis.

Fasciola hepatica is the causative agent of fasciolosis in Peru; the disease is an important public health problem by the high prevalence of the human infection affecting mainly children and a major veterinary problem by the high rates of infected livestock. The human disease is endemic in the Sierra and the Coast but sporadic in the Amazonia, and reported in 18 Departments, while the animal infection in 21 of 24 Departments of Peru. Transmission occurs in Andean rural populations engaged in agriculture, but recently an increasing number of people became infected in the cities. The epidemiological situation in Peru includes i) Departments with non-autochtonous cases, where infection occurs by consumption of contaminated vegetables brought from endemic areas or infection is acquired by visit to endemic areas; ii) Departments with hypoendemic and mesoendemic villages, where transmission occurs by ingest of contaminated vegetables and prevalence ≤10%; and iii) Departments with hyper-endemic villages with human prevalence >10 %, with an intense transmission by consumption of contaminated vegetables. The disease affects bovine, sheep, goat, swine, equine, South American camelids, rabbits and guinea pigs. The negative impact of fasciolosis in the livestock economy is not lesser than US$ 50 million per year, estimation based on the prevalence and the number of condemned livers in the abattoirs. It is difficult to estimate the economic impact of this infection in the human health due to its status of neglected disease, but fasciolosis is hyper-endemic in the poorest Andean areas of Peru where the situation has to be recognized as a public health emergency.

Fasciola hepatica adult worm cysteine proteinases were active-site, affinity radio-labeled with benzyloxicarbonyl-L-tyrosine-L-alanine diazomethylketone (Z-Tyr125I-Ala-CHN2). Sera from patients with fascioliasis and from rabbits experimentally infected with F. hepatica immunoprecipitated the radiolabeled parasite cysteine proteinases in immunoelectrophoresis assays. Two purified antigens were identified as part of the complex mosaic of antigens immunoprecipitated by the sera of infected patients. These antigens (Fas1 and Fas2) have been shown to be an important part of the Fharc2 precipitin band used for serologic diagnosis in humans and cattle. They showed cysteine proteinase activity with different proteolytic specificities and partial identity in double immunodiffusion assays. The results obtained in this work show that the Fas1 and Fas2 antigens are sensitive and specific antigens for diagnosis of this serious helminthic disease in humans and other susceptible hosts.