Although Dr. Broughton left last spring to join the faculty at the Washington State University College of Veterinary Medicine, he sent me one last photo from his NDSU VDL collection to share.

This image is from the abdomen of a 24-year-old horse. Within the abdominal cavity is a free-standing parasitic worm.

What is this parasitic worm and how is it transmitted? Setaria – a parasitic filarid nematode that is transmitted via mosquito bites. Some species of Setaria can cause blindness in equids.


In addition to the intra-abdominal nematode, this horse also had bots (fly larvae) along the margo plicatus of the stomach. Gasterophilus nasalis and G. intestinal are common in horses that are not adequately dewormed. G. nasalis larvae are swallowed after hatching in the nares of the horse. They reside in the glandular (distal) portion of the stomach. G. intestinalis eggs are laid along the distal limbs before migrating to the oral cavity. G. intestinal larva are also swallowed and colonize the stratified (proximal) portion of the stomach. Both larval species are passed in the feces, where they can pupate and develop into flies.

Mystery photo: Setaria
BONUS IMAGE: Gasterophilus nasalis