Prevalence, abundance and site distribution of equine small strongyles in Normandy, France.

This study examines the prevalence, abundance, and distribution of small strongyle infections in horses in Normandy, France. It found a high prevalence of these infections, with various species of the parasite showing particular preferences for different parts of the horse’s digestive system.

Methodology and Findings

• Forty-two horses in Normandy, France were inspected for small strongyle (a type of parasitic worm) infections after death. The study was carried out during the cooler months, from October to March.
• The examined horses that tested positive were found to have total small strongyle counts ranging from 234 to an astounding 90,247, with an average of around 11,297.
• A large portion (83%) of the cyathostome burdens – a subgroup of small strongyles – were found to be early third-stage larvae.
• The majority of these larvae were observed in the caecum (48%) and the ventral colon (40%) of the horses, while a smaller portion was located in the dorsal colon (12%).
• Adult cyathostomes were primarily encountered in the ventral colon (64%) and less frequently found in the dorsal colon (27%) and the caecum (9%).

Species Variation and Distribution

• Twenty distinct species of Cyathostominae, which is a subfamily of small strongyles, were identified.
• The ten most common species in order of their prevalence were: Cyathostomum coronatum, Cylicocyclus nassatus, Cylicocyclus insigne, Cyathostomum catinatum, Cylicostephanus goldi, Poteriostomum imparidentatum, Cyathostomum labiatum, Cylicocyclus ultrajectinus, Cylicostephanus calicatus and Cylicostephanus minutus. These ten species comprised 84% of the entire adult population observed.
• Of these, twelve species demonstrated a preference for the ventral colon, five favoured the dorsal colon, only one preferred the caecum, and two species were detected, in nearly equal numbers, in both the ventral and dorsal colons.

Extent of Infection and its Implications

• The count of Cyathostominae species encountered in each horse ranged from 1 to 12, with a median of 5 species. This variability suggests a wide range of potential combinations of species within a single host.
• Single species infections were found in 12.5% of the infected horses, while multiple species infections were more common, found in 87.5% of cases.
• The study indicated a positive correlation between the intensity of cyathostome infection and the diversity of species present, which was measured by both the number of different species and the Shannon index, a measure of diversity within a community.