Gastrointestinal helminths of ponies in Louisiana: a comparison of species currently prevalent with those present 20 years ago.

The study investigated the changes in gastrointestinal parasites affecting ponies in Louisiana over a period of 20 years, specifically evaluating whether the use of anti-parasitic drugs and overall infection pressure has impacted parasite diversity.

Research Objective

• The study aimed to understand if the diversity of gastrointestinal parasites in ponies from Louisiana has changed over two decades. A significant portion of this study is dedicated to figuring out how the use of macrocyclic lactone (ML) parasiticides – a type of anti-parasitic medication – and increased exposure to parasites has affected parasite species diversity.

Methods

• The research was conducted by comparing two surveys, one from 20 years ago, and a recent survey conducted from 1989 to 2000. The test subjects were 117 ponies with minimal exposure to anti-parasitic drugs.
• These ponies were necropsied (an autopsy for animals) to recover and identify the parasites.

Findings

• A total of 26 cyathostome (small strongyle) species and 8 strongyle species were found. Furthermore, three new species, not previously detected in the area, were identified, namely: Cylicostephanus asymetricus, C. bidentatus (both small strongyles), and Oesophagodontus robustus (a large strongyle).
• While all previously identified species were still apparent, both the prevalence and intensity of infections for almost all large and small strongyle species were observed to be significantly reduced.
• The prevalences and intensities of Oxyuris equi (pinworm) adults and larvae saw a decrease, while the prevalence of Parascaris equorum (ascarid) remained stable.
• Paranoplocephala mamillana, a type of tapeworm, was a new addition to the list. Meanwhile, Anoplocephala perfoliata remained the most common tapeworm, with the same level of intensity but slightly higher prevalence. Anoplocephala magna was found less frequently than in the earlier period.
• Overall, the diversity of species mostly remained unchanged.

Deductions

• The decrease in prevalence and intensity of most parasites is unexplained, with suggestions that it may be due to the use of broad-spectrum ML anthelmintics, changes in the equine population or the use of different techniques to identify parasites.