A novel second instar Gasterophilus excretory/secretory antigen-based ELISA for the diagnosis of gasterophilosis in grazing horses.

This research article presents the development of a new testing method, or ELISA, for diagnosing gasterophilosis, a parasitic disease, in grazing horses. The method uses excretory/secretory antigens from the second instar Gasterophilus. Experiments using the test were conducted on numerous horses over two years, alongside data collection on local weather and observations of the parasite during different stages of its life cycle.

Development of the ELISA

• The research team developed an enzyme-linked immunosorbent assay (ELISA), a commonly used immune system-based test for detecting specific proteins or antigens. This ELISA is unique as it uses excretory/secretory antigens from the second stage larva (instar) of Gasterophilus intestinalis and Gasterophilus nasalis.
• The aim was to discover a more effective means to diagnose gasterophilosis, a common and potentially dangerous parasitic infection in horses caused by bot flies of the genus Gasterophilus.

Field Experiments Using the Developed ELISA

• The tests were conducted in two separate field experiments between January 2007 and January 2009 on free-ranging horses in northwest Spain.
• The first-year experiment involved monthly blood samples from one collective herd of 25 horses.
• In the second-year, a larger survey was conducted on 398 different horses across the same area.

Data Collection and Analysis

• Researchers analyzed the blood samples using the developed ELISA, noting and comparing the horses’ immune response (IgG response) against the antigens.
• Climatic data were collected from local meteorological stations to establish any correlation between the prevalence of the disease and specific weather patterns.
• The team also investigated physical evidence of the disease, visually inspecting horses for eggs and checking feces for third instar larvae.

Results and Conclusion

• The resulting analysis indicated a significant fluctuation in the immune response against the antigens throughout the year. The IgG response decreased from January to July, gradually increased from August, and peaked in January.
• Observations showed that the Gasterophilus eggs appear on horses’ hair from June to September, and the larvae passed in feces from March to May.
• Based on these findings, the researchers recommend two treatments for gasterophilosis: curative treatment in the summer to eliminate first instar larvae and preventive treatment in autumn to suppress second instar larvae.
• The study concluded that the ELISA they developed is a feasible tool for diagnosing gasterophilosis in grazing horses. Furthermore, the results reveal vital information about the seasonal life cycle of Gasterophilus and how it affects gasterophilosis occurrence.