Roundworms

J. L. GARDINER.

MANY kinds of roundworms attack poultry. Two or three of them occur in all parts of the country and are troublemakers everywhere. Several others occasionally cause severe losses. A roundworm that gets out of hand has a great potential for harm.

The digestive tract of the host is the habitat favored by most poultry roundworms, but some roundworms attack the eyes, air sacs, thoracic and abdominal cavities, and the windpipe. Among those that favor the digestive tract are specialists that prefer such an unlikely organ as the gizzard for their base of operations.

Roundworms do damage in two ways: By a direct attack on the tissues of the host, which serve them as food, and by the elimination of toxic substances into the host's system.

Satisfactory treatments have been worked out for some kinds of roundworms, such as the gapeworm, cecal worm, and large intestinal roundworm, but no drugs have been found that will deal adequately with most of the roundworm parasites of poultry. Prevention is better than cure.

Taking first things first: The location of the poultry runs should be chosen with sanitation in mind. The ideal spot is a gently sloping piece of land with sandy or gravelly soil and the best possible drainage.

It is wise to rotate the runs. The four-yard system is perhaps the most satisfactory. The ground assigned to one kind of fowl (chicken, turkey, or whatever it may be) is divided into four equal lots by cross-fencing. The poultry house is placed in the center, with a door opening into each lot. The birds are rotated from one lot to an-other and are left not more than 3 months at a time in any one lot. After the birds have been removed from a lot, it may be plowed and planted to some green crop, plowed and left fallow, or simply left undisturbed. Of these alternatives, the first is probably the best.

Proper disposal of droppings and removal of trash that might afford shelter and breeding places for insects and other invertebrates that are intermediate hosts are important in good poultry management.

Another important precept to follow is never to raise young and old birds, or different kinds of birds, on the same piece of ground. Grown chickens, turkeys, and guinea fowl can carry gape-worms without any visible ill effects, but young chicks or poults that are allowed to run with them may become infected, with serious consequences.

Another example of the inadvisability of raising different kinds of poultry together: Blackhead occurs in chickens of all ages, along with its carrier, the cecal worm. It happens frequently that the chickens do not suffer enough ill effects for the poultryman or farmer to be aware that the disease is present among them, but turkeys that are put in the same lot with the chickens will contract blackhead from their associates and the owner will not be left long in doubt that blackhead is present in the turkeys.

THE LARGE INTESTINAL ROUNDWORM, Ascaridia galli, is the roundworm best known to poultry raisers. It is common and large enough to be seen easily. Primarily a parasite of chickens, it is found in the intestines, sometimes in numbers great enough to block the passage.

As are most parasites, this worm is a much more serious problem with young birds than with older ones. Large numbers in young chicks sometimes kill them. In lesser numbers, it stunts the growth and prevents proper bone development. In grown chickens its presence may cause a drop in laying.

This roundworm occasionally wanders up the oviduct and becomes entrapped in the egg as it forms.

The large intestinal roundworm has no intermediate host. Its eggs pass out in the droppings of its host and continue to incubate while lying about on the ground. The eggs reach the infective stage in 15 to 20 days when weather conditions are favorable. They are then ready to hatch if a chicken (or possibly a turkey, duck, or goose) swallows them.

The egg having been swallowed by an acceptable host, the young worm that emerges from it spends the first 10 to 20 days of its active life burrowing in the inner surface of the host's intestinal wall, where it damages the glands. It then emerges from the intestinal wall and from that time on lives within the intestinal passage.

Preventive measures against the large intestinal roundworm include general sanitation, rotation of runs, and keeping young birds off the ground where older birds were kept.

This is one species of roundworm for which treatment has been developed. Nicotine sulfate (in combination with Fuller's earth), tetrachlorethylene, piperazine compounds, and carbon tetrachloride are effective.

SEVERAL RELATED SPECIES of ascarids, as this group of roundworms is called, occur in other kinds of domestic poultry, but none is considered to be of great importance. The guinea fowl, pigeon, and turkey each has its own particular ascarid, which lives in the small intestine of its respective host.

The small intestine is the base of operations for a few other roundworm parasites of poultry. The threadworm, or pigeon capillarid, Capillaria obsignata, a slender, colorless worm about one-half inch long when mature, occurs in pigeons, chickens, and occasionally in turkeys. Large numbers of threadworms can cause a considerable loss in weight; the birds may die from the damage done to the intestines, if the infestation is especially severe.

Like the large intestinal roundworm, the threadworm has a direct life history. Its eggs are passed out by one bird and swallowed by another without going through a stage of development inside some invertebrate intermediary.

No satisfactory treatment for thread-worms is known. The only method of combating them is by sanitation.

A related species, the hairworm, Capillaria caudinflata, looks like the threadworm. It infests chickens and turkeys and may seriously affect their health.

Pigeons are parasitized by an intestinal roundworm, Ornithostrongylus quadriradiatus, which has no common name. It apparently does its damage by sucking the blood of its host. It has no intermediate host, but its eggs, after being passed from the pigeon, hatch on the ground. The young larvae, rather than the eggs, are picked up by the next host.

The ceca, or blind guts (the two little pouches that grow out of the sides of the intestines of many birds), are the seat of infestation of several kinds of roundworms.

The most important is the cecal worm, Heterakis gallinarum, which parasitizes chickens, turkeys, and guinea fowl. In large numbers, it may cause a serious inflammation of the ceca, but the main reason for concern about it is not for the direct damage it may do. More serious is that it is a carrier of the organism that causes blackhead in turkeys. Because chickens, which are little affected by blackhead, are favorite hosts for cecal worms, they and turkeys should not be turned loose in the same runs.

The cecal worm, which is small and hard to see, has a life history like that of the large intestinal roundworm. Its eggs pass to the ground in the droppings of one host and are swallowed by another host, in which they hatch and in which the larvae grow to maturity. Earthworms often swallow the eggs. The eggs are not digested by the earthworm and do not hatch within it; they just stay in its alimentary canal. Should an earthworm that has swallowed cecal worm eggs be eaten by a chicken or other suitable host, the eggs hatch and the young worms continue to develop.

Sanitation measures and rotation of runs are important in keeping down the numbers of cecal worms.

Phenothiazine is effective in ridding birds of cecal worms.

The ceca of chickens and turkeys harbor the strongyloid, Strongyloides avium, a very small species of roundworm. It may seriously endanger its host's health, especially if the host happens to be a young chicken. The activities of the strongyloid thicken the walls of the ceca. Bloody diarrhea is sometimes a symptom of its presence. A host that survives the acute stage of this illness may continue to harbor the parasite with no more apparent bad effects. The strongyloid can mature and reproduce in the soil, without a host.