Be aware of bloodworm in horses: DNA detection method

DNA technology is causing a revolution in every area of the sciences at the present time, and also by diagnosing gastrointestinal parasites in horses.

A Danish Ph.D. student from the University of Copenhagen has developed a new diagnostic method to detect equine bloodworms, Strongylus vulgaris.

The bloodworm has its name because of the extensive migrations in the blood vessels of the horse. After being ingested during grazing, the larvae occupy the blood stream for nearly four months, causing severe reactions, and leading to "thrombo-embolic colic", a disease syndrome distinguished by manifestations of severe pain.

The condition has very poor prognosis, and the horse death is frequently the result.

Bloodworm eggs are morphologically similar from the majority of parasite eggs in horse faeces, and after two weeks of coproculture and microscopic identification of the larvae, a definitive diagnosis of bloodworm infection can be reached. This procedure is time-consuming and requires substancial skills from the microscopist who identifies the bloodworm larvae.

"Nowadays, we recommend minimal deworming to prevent further development of anthelmintic resistance as much as possible. At many horse establishments in Denmark, people deworm twice yearly or less, and the choice of treatment is based on faecal examination", says Dr. Martin Krarup Nielsen, DVM from the University of Copenhagen.

"The coproculture method is labour-intensive and not fully reliable, and as a consequence, some horses are being under-treated, while others are over-treated".

Dr. Nielsen spent part of his study at the American University of Georgia, and used the real-time polymerase chain reaction (PCR) technique to develop his assay to detect bloodworm DNA in faecal samples. The assay can detect a single bloodworm egg among thousands of parasite eggs in a sample, and it can define the quantity bloodworm eggs. The instrumentation can analyze 96 samples at the time, and the entire procedure can be completed within a working day.

"We now have a powerful and reliable diagnostic tool for monitoring the bloodworm of horses, which will be of benefit for horses world-wide", asseverates Dr. Nielsen.

He will present his work at international conferences in Washington DC, USA and Ghent, Belgium during 2007.

"Detection and semi-quantification of Strongylus vulgaris DNA in equine faeces by real-time quantitative PCR"
Martin K. Nielsen et al - Department of Large Animal Sciences, Faculty of Life Sciences, University of Copenhagen, Denmark
Published in the International Journal for Parasitology