Endemic human fasciolosis in the Bolivian Altiplano.

Fasciolosis, caused by trematodes of the genus Fasciola, is an emerging disease of humans. One of the highest levels of human fasciolosis hepatica is found amongst the indigenous Aymaran people of the Northern Bolivian Altiplano. A meta-analysis of epidemiological surveys from 38 communities in the region demonstrates that fasciolosis has been endemic in the region since at least 1984 and is a zoonosis of rural communities. Human and bovine fasciolosis is associated with the communities lying in the plain from Lake Titicaca to La Paz, predominantly in the Los Andes province. In Los Andes incidences of up to 67% of population cohorts were found, and prevalence is age-related with the highest infection rate in children aged 8-11 years.

Short report: Diagnosis of human fascioliasis: detection of anti-cathepsin L antibodies in blood samples collected on filter paper.

We have developed an ELISA for the diagnosis of human fascioliasis based on the detection of IgG4 antibodies to Fasciola hepatica cathepsin LI cysteine protease. Use of this assay in the Bolivian Altiplano, a region with a high prevalence of the disease, was hampered by the reluctance of the indigenous population to provide blood. To overcome this problem, we have investigated the method of collecting small quantities of blood from the finger onto filter paper, followed by the elution of antibodies for use in the diagnostic assay. Serum samples and blood samples collected onto filter paper were obtained from 57 individuals living in the village of Cutusuma in 1987 and from 11 individuals in Chijipata in 1996. Analysis of the IgG4-ELISA results revealed that there is highly significant linear relationship (P < 0.001) between the two methods of sampling. Most importantly, a reliable diagnosis was made with the blood-filter samples from Cutusuma, which had been stored for 10 years at 40 degrees C. While some deterioration of the blood-filter samples from Cutusuma had occurred over the 10-year storage period, no deterioration occurred with the Chijipata samples, which were stored for one year. Therefore, the method of collecting blood onto filter paper should prove useful for large-scale epidemiologic studies on human fascioliasis in the Bolivian Altiplano and in other regions where this disease is prevalent.

Immunodiagnosis of Fasciola hepatica infection (fascioliasis) in a human population in the Bolivian Altiplano using purified cathepsin L cysteine proteinase.

Cathepsin L1 (CL1), an immunogenic cysteine proteinase secreted by juvenile and adult Fasciola hepatica, was assessed for its potential as a diagnostic agent for the serologic detection of human fascioliasis. Using ELISAs, we compared the ability of liver fluke homogenates (LFH), excretory/secretory (ES) products, and CL1 to discriminate between seropositive (infected) and seronegative (noninfected) individuals within a population of 95 patients from the Bolivian Altiplano. A high prevalence of human fascioliasis has been reported in this region. The division between the seropositive and seronegative individuals was poorly defined when LFH was used as the antigen. A greater discrimination between these populations was achieved with both ES and CL1. A K-means cluster analysis using the combined ES and CL1 ELISA data identified a cluster of seropositive individuals. Cathepsin L1 detected a subset (20) of these seropositive individuals while ES detected all 26; however, ES detected nine additional individuals that were in the seronegative cluster. The ratio of the mean absorbance readings between seropositive and seronegative individuals was markedly improved by using conjugated second antibodies to IgG4, the predominant isotype elicited by infection. In these IgG4-ELISAs, CL1 again identified fewer individuals as seropositive than did ES, but improved the discrimination between the seropositive and seronegative individuals and thus provided a more conclusive diagnosis. Sera obtained from patients infected with schistosomiasis mansoni, cysticercosis, hydatidosis, and Chagas' disease were negative in these assays, which demonstrated the specificity of the IgG4-ELISA for detecting fascioliasis. Twenty of the 95 patients (21%) were seropositive for fascioliasis by the CL1 IgG4-ELISA, confirming the earlier reports of the high prevalence of disease in this region. A standardized diagnostic test for human fascioliasis, based on an ELISA that detects IgG4 responses to CL1, could be available to all diagnostic centers if sufficient quantities of recombinant CL1 can be produced.