First report of equine Setaria digitata (von Linstow 1906) infestation in Malaysia.

This study reports for the first time a horse in Malaysia infested with the parasite, Setaria digitata. The infestation was identified after the horse was treated for corneal opacity and a worm-like organism was found in its eye which was confirmed as the S. digitata parasite through morphological and genetic analysis.

Background of the Study

• The study set out to investigate an unusual case of a horse presenting with corneal opacity and eye discharge.
• The horse was an 8-year-old Thoroughbred cross mare in Malaysia, and its infestation by the Setaria digitata parasite is the first recorded instance in the country.
• Setaria digitata is a parasite often seen in domestic animals like cattle, causing a condition known as setariasis.

Methodology

• Initially, the horse was treated with Terramycin eye ointment for the corneal opacity. After partial clearing of the opacity, a moving worm-like creature was seen in the eye’s anterior chamber.
• The parasite was surgically removed and examined under a light microscope, which revealed that it was a 5th stage larva of S. digitata.
• Molecular methods were used to confirm the species of the worm. The 12S rRNA gene was PCR-amplified and the purified amplicon was directly sequenced.
• Phylogenetic analyses were carried out to further identify the isolated roundworm.

Findings

• The isolated roundworm showed 100% sequence similarity with the previously identified S. digitata in the NCBI GenBank database (Accession no.: KY284626.1).
• This provided undisputable evidence that the parasitic worm in the horse’s eye was indeed Setaria digitata, marking the first confirmed case of equine ocular setariasis by S. digitata in Malaysia.

Implications

• The findings of the study prove that S. digitata can be a cause of ocular infection in horses.
• It indicates the presence of this parasite in Malaysia, which might have implications for domestic animals’ health in the nation.