The gapeworm (Syngamus trachea) is a round red worm that attach to the trachea (windpipe) of birds and causes the disease referred to as “gapes”. The term describes the open-mouth breathing characteristic of gapeworm-infected birds. Heavily infected birds usually emit a grunting sound because of the difficulty in breathing and many die from suffocation. The worms can easily block the trachea, so they are particularly harmful to young birds.
The gapeworm is sometimes designated as the “red-worm”; or “forked-worm” because of its red color and because the male and female are joined in permanent copulation. They appear like the letter Y. The female is the larger of the two and is one-fourth to one inch in length. The male gapeworm may attain a length of one-fourth inch. Both sexes attach to the lining of the trachea with their mouthparts. Sufficient numbers may accumulate in the trachea to hinder air passage.
The life cycle of the gapeworm is similar to that of the cecal worm; the parasite can be transmitted when birds eat embryonated worm eggs or earthworms containing the gapeworm larvae. The female worm lays eggs in the trachea, the eggs are coughed up, swallowed, and pass out in the droppings. Within eight to fourteen days the eggs embryonate and are infective when eaten by birds or earthworms. The earthworm, snails and slugs serve as primary intermediate hosts for the gapeworm. Gapeworms in infected earthworms remain viable for four and a half years while those in snails and slugs remain infective for one year. After being consumed by the bird, gapeworm larvae hatch in the intestine and migrate from the intestine to the trachea and lungs.
Gapeworms infect chickens, turkeys, guinea fowl, pheasants, chukar partridge, and probably other birds. Young birds reared on soil of infected range pens are at high risk (pen-raised game birds). Some control or reduction in infection density (worms/bird) is achieved by alternating the use of range pens every other year and/or using a pen for only one brood each year. Tilling the soil in the pens at the end of the growing season helps to reduce the residual infection. Treating the soil to eliminate earthworms, snails and slugs is possible but the cost is usually prohibitive.
Gapeworms are best prevented by administering a wormer at fifteen to thirty day intervals or including a drug at low levels continuously beginning fifteen days after birds are placed in the infected pens. One drug that is effective for eliminating gapeworms is fenbendazole, however, its use is not presently approved for use in birds by the Food and Drug Administration.