Serodiagnosis of Fasciola gigantica Infection in Buffaloes with Native Cathepsin-L Proteases and Recombinant Cathepsin L1-D

Advances in diagnostic approaches to Fasciola infection in animals and humans: An overviews

Fasciolosis, caused by Fasciola hepatica and F. gigantica, is an impediment to the livestock industry’s expansion and has a massively negative socio-economic impact due to its widespread prevalence in livestock. It is a waterborne zoonosis affecting human populations in the countries where rural economies are associated with livestock rearing. Conventional diagnosis of Fasciola infection is done by detecting parasite eggs in the faeces of infected animals or by immunological methods. Accurate and quick immunodiagnosis of Fasciola infection in animals and humans is based on the detection of antibodies and specific antigens expressed in the prepatent stage of the parasite. Both molecular and serodiagnostic tests developed thus far have enhanced the reliability of Fasciola diagnosis in both man and animals but are not widely available in resource-poor nations. A pen-side diagnostic test based on a lateral flow assay or a DNA test like loop-mediated isothermal amplification (LAMP) would be simple, fast, and cost-effective, enabling clinicians to treat animals in a targeted manner and avoid the development of drug resistance to the limited flukicides. This review focuses on the recent advances made in the diagnosis of this parasite infection in animals and humans.

Development of a colloidal gold immunochromatographic strip for the rapid detection of antibodies against Fasciola gigantica in buffalo

Background

Fasciola gigantica, a tropical liver fluke, infects buffalo in Asian and African countries, causing significant economic losses and posing public health threats. The diagnostic of buffalo fascioliasis caused by F. gigantica is vital in fascioliasis control and preventation. The 22nd gel filtration chromatography fraction of F. gigantica Excretory-Secretory Products (FgESP), namely Fasciola 22 (F22), which was used as a diagnostic antigen in indirect ELISA, has demonstrated great potential for fascioliasis diagnosing. In the absence of rapid diagnostic methods, the use of a colloidal gold immunochromatographic strip based on F22 was applied to detect F. gigantica infection in buffalo.

Methods

In the present study, the 22nd gel filtration chromatography fraction of FgESP (F22) was used as an antigen to establish the colloidal gold-based immunochromatographic strip (ICS). The nitrocellulose membrane was incubated with F22 at the test line (T line) and goat anti-mouse secondary antibody at the control line (C line). The mouse anti-buffalo secondary antibody 2G7 conjugated to colloidal gold particles was used as the detection system for line visualization. The strip was assembled and developed by optimizing reaction conditions. The sensitivity, specificity, stability, and early diagnostic value of the strip were evaluated employing buffalo-derived sera.

Results

An immunochromatographic strip for the rapid detection of antibodies against F. gigantica-FgICS was developed. The strip demonstrated high sensitivity and specificity. Sensitivity tests confirmed positive results even when the positive reference serum was diluted 4,096 times. Except for one Schistosoma japonicum-positive serum that tested positive via FgICS, specificity tests confirmed no cross-reactivity with other positive sera of Schistosoma japonicum and Babesia bovis. The strip remained stable after storage at 4°C for up to 3 months. In infected buffalo, antibodies could be detected as early as 14–21 days post-infection. The detection of 17 positive sera yielded an 82.4% positive rate via FgICS vs. a 100.0% positive rate via ELISA based on FgESP. For FgICS, the 95% confidence interval of sensitivity was 84.8–95.4%, while specificity was 4.2–14.7%.

Conclusion

The immunochromatographic strip FgICS developed in this study provides a simple and rapid method of F. gigantica antibody detection and infected buffalo monitoring in the field.

Fasciolosis in India: An overview

Fasciolosis in ruminants is a relentless constraint in the livestock industry across the world. Immuno-prophylactic vaccines against fasciolosis may not come up in near future, rendering the control of this scourge with chemotherapy and snail population control. With the alarming threats of anti-fasciolid drug resistance reported from certain parts of the world; the control of fasciolosis should be directed towards the development of rapid and reliable diagnostic tools to execute the specific and discrete treatment. Understanding the epidemiology of Fasciola, its genomics and proteomics, host-parasite interplay, and advances in drug design research is vital for improving animal health that would ultimately succour to meet the ever-increasing demand for food. Due to possible differences in immune response depending on the species of the host and parasite, immuno-prophylactic studies in India should aim at achieving protective efficacy in buffalo against F. gigantica as workers from other countries concentrate primarily on vaccination of cattle and sheep against F. hepatica. This manuscript focused on the research that has been carried out in India for understanding the epidemiology, genetic diversity, immuno-diagnosis, and possible control measure in terms of immuno-prophylaxis and drug designing against tropical fasciolosis caused by Fasciola gigantica.