Physiologic and systemic acute phase inflammatory responses in young horses repeatedly infected with cyathostomins and Strongylus vulgaris.

This research investigates the inflammatory response in horses infected with specific types of parasites: the Strongylus vulgaris and cyathostomin larvae. Various inflammatory markers’ changes in blood samples were studied to understand whether these parasites cause an overall body reaction, revealing a potential link between certain blood protein concentrations and the presence of these parasites.

Research Set-Up

• The study involved 28 horses assigned randomly to receive either an antiparasitic drug (pyrantel tartrate) or a placebo in their food. An important factor to note here is that the horses were exposed intentionally to the parasites to monitor their physiological response and the effectiveness of the treatment.
• This exposure lasted for 24 weeks with daily cyathostomin larvae and weekly Strongylus vulgaris larvae administrations, starting from the fifth week. The study was designed to replicate the infections naturally occurring in horses.

Data Collection

• Biweekly fecal and blood samples were collected to check for parasite egg counts and measure various indicators of inflammation in the blood, respectively. The inflammation markers included proteins such as serum amyloid A (SAA), haptoglobin (Hp), albumin, globulin, and iron (Fe), as well as albumin/globulin (A/G) ratio.
• At the end of the study, the horses were euthanized, and additional samples were taken from their intestines to count the number of parasites and parasite larvae.

Key Findings

• Strongyle burdens (the number of these parasites in a horse’s system), were found to be significantly associated with variations of haptoglobin (Hp), iron (Fe), and albumin/globulin (A/G) ratio.
• In the group of male horses receiving the antiparasitic treatment, there was a significant increase in serum albumin, a protein that often decreases in response to systemic inflammation.
• No association was found between the larval S. vulgaris and the iron levels in the blood. However, a negative correlation was observed between the cyathostomin burdens and iron levels, indicating more parasites could be linked with lowered iron availability in the blood.
• There was also a significant difference in the A/G ratio between the two treatment groups. Differences in Hp and Fe were also noticed at specific time points of measurement.
• Serum amyloid A (SAA) concentration, another key marker of inflammation, remained low throughout the study, indicating these parasites might not cause a systemic acute phase reaction by this specific marker.

Conclusions

• This study suggests that infections with the parasites S. vulgaris and cyathostomins can cause changes in haptoglobin, iron, and serum protein levels, but not in that of the systemic inflammation marker SAA. These changes indicate that the immune system does react, though mildly, to the presence of these parasites.