[Experimental equine fascioliasis: evolution of serologic, enzymatic and parasitic parameters].

This study explores the impact of different levels of Fasciola hepatica infection in horses to understand the development of specific antibodies, changes in enzymatic levels and egg production of the parasite. The research findings show the limits of fecal examination for diagnosing the infection and different levels of antibodies production based on the ELISA, counter-electrophoresis, and passive hemagglutination assay.

Research Methodology

• The researchers infected eight horses with varying quantities of Fasciola hepatica metacercariae (larvae), with three horses receiving 100 larvae, four horses 1,000 larvae, and one horse 5,000 larvae.
• After 38 weeks, the researchers reinfected six of the horses with an additional 1,000 larvae each. This allows them to study the response of the horses to reinfection.

Expression of Specific Antibodies

• The study found that antibodies against Fasciola hepatica showed up in the horses’ blood three to six weeks after initial infection.
• The peak presence of these specific antibodies was observed 10 to 17 weeks after infection.
• Horses infected with higher counts of larvae (1,000 or more) proved to have greater rates of antibody presence as shown by different tests: 17.6% by counter-electrophoresis, 49.2% by ELISA, and 75.6% by passive hemagglutination. This indicates the level of antibody production may be proportional to the severity of the infection.

Effect on Enzymatic Levels

• Plasma glutamate dehydrogenase and gamma-glutamyltransferase levels increased significantly between three and five months post-infection, but only in the horses infected with the largest numbers of larvae. These enzymes are often used as markers of liver damage, indicating the impact of the infection.

Observed Parasite Eggs

• Interestingly, the researchers only observed Fasciola hepatica eggs in the feces of two out of the eight infected horses, and this occurred 14 and 15 weeks post infection.
• This observation suggests the presence of parasite eggs in the feces is not a reliable indicator of infection, which highlights the need for other diagnostic methods like antibody and enzyme level testing.