[Biological and parasitic variations in horses infested and reinfested by Trichinella spiralis].

This research paper discusses a study aimed at understanding the response of horses to infection and reinfection with the parasite Trichinella spiralis. The researchers infected seven mares with the parasite and observed changes in their serology, biochemistry, parasitology and histopathology to assess the course of infection.

Experimentation Procedure

• The research involved experimentation on seven mares that were infected with 20,000 Trichinella spiralis larvae. Out of these seven horses, two were reinfected with the same amount of larvae 22 weeks later.
• The health and behavior of the horses were monitored closely. The researchers examined the horses’ serology, biochemistry, parasitology, and histopathology.

First Infection

• Observations post-infection revealed that with the onset of infection, there was a considerable increase in specific antibody titers in the horses. The increase peaked between 5-10 weeks post-infection then began to decline over time.
• The activity of an enzyme called Aldolase was noted to increase during the first infection. This enzyme is often implicated in various infectious diseases, with elevated levels potentially indicating muscle tissue damage caused by the parasite.
• The highest parasite burden was seen 20 weeks post-infection, where the number of larvae ranged from 24-145 per gram of tissue, depending on their location within the host animal. By the 52nd week post-infection, the numbers had significantly reduced to an almost negligible amount (0.4-5 larvae per gram).

Reinfection

• On reinfection, there was only a slight rise in the mares’ antibody levels. Additionally, it’s noted that the Aldolase activity appeared unchanged in the reinfected horses, suggesting a possible immunity or altered response to the second invasion of parasites.
• Interestingly, the number of parasites found in reinfected horses was comparable to that of horses infected only once at 28 weeks post-infection but saw a significant drop in parasite count at 40 weeks post-infection.
• Around 6 weeks after the reinfection, the researchers noticed large inflammatory granulomas surrounding the larvae. This may have been due to the horses’ heightened immune response, possibly aided by the initial infection, effectively rejecting the reinfecting parasites more aggressively.

Conclusion

• The study shows that horses are prone to Trichinella spiralis infection. However, the fast-fading specific antibodies make it challenging to diagnose infection using typical serological methods.
• Most critically, the research proposes that reinfection might assist horses in eliminating the larvae more rapidly, suggesting some memory response in the horse’s immune system, like is seen in other species.