DISEASES AND PARASITES AFFECTING poultry

Coccidiosis of Chickens and Turkeys

EVERETT E. WEHR AND MARION M. FARR.

COCCIDIOSIS costs poultry raisers millions of dollars each year because of the unthriftiness, poor utilization of feed, loss of weight, and death of infected birds.

Coccidiosis is caused by coccidia, which are microscopic protozoan parasites. coccidia of poultry are nearly always host specific each species is so adjusted to a life within the body of one kind of bird that it may not survive very long in another.

The coccidia that affect chickens and turkeys follow a similar course of development. They develop within the cells that line the wall of the intestine and cecal pouches. In their resistant stage as oocysts they are discharged into the cavity of the intestine and pass Out with the droppings.

Before they can infect birds, the oocysts must develop, or sporulate. When the weather is warm and the oocysts remain moist, development is completed in about 1 to 3 days. Oocysts have tough shells. They can withstand cold and dryness and have been known to survive on soil and elsewhere for many months.

Poultry get coccidiosis by swallowing the sporulated oocysts with feed and water that have become contaminated with the oocysts of infected birds. The droppings are spread from place to place by the birds themselves and by mice, cats, dogs, flies, and other insects. Persons that care for poultry may carry the oocysts on their hands, feet, and clothing. Dirty sacks and crates and contaminated litter may also be responsible for the spread of coccidiosis.

Not every bird that swallows infective oocysts develops symptoms of coccidiosis. Some birds may pick up just enough oocysts to produce a light infection, which may cause them little or no discomfort.

Repeated light infections may cause the bird to build up a resistance to the particular species involved. Resistant birds may then pick up large numbers of the same species of oocysts without serious effects. Once a bird becomes immune or resistant to one or more species of coccidia, it may remain resistant to them for several months.

Two types of coccidiosis occur in chickens. In one, the infection is limited primarily to the blind pouches, or ceca. It is known as cecal coccidiosis. In the other, the parasites attack the part of the intestine between the gizzard and the opening of the ceca--the ceca may or may not be involved. This type is known as intestinal coccidiosis.

In cecal coccidiosis, the parasites enter the cells lining the walls of the ceca, multiply rapidly, and destroy them. Severe bleeding and death may be the result. Bloody droppings are an important sign of cecal coccidiosis. This disorder is caused by only one species of coccidia, Eimeria tenella. It occurs mostly in chickens less than 2 months old. Chickens of any age may get it, however. It strikes suddenly. Sometimes the poultryman is taken completely by surprise.

The following is a typical picture of an outbreak of cecal coccidiosis: Yesterday the birds appeared healthy eating, drinking, and chasing each other around the pen. Today some or many are dead. Others are visibly sick, while still others are eating and drinking and are apparently healthy. Bloody droppings are seen on the ground or litter.

THE SEVEN SPECIES of coccidia that cause intestinal coccidiosis occur mainly in the small intestine occasionally in the large intestine or bowel and ceca. They give rise to a serious but usually less acute condition than occurs in cecal coccidiosis. This type may affect chickens of any age, but serious losses occur oftenest in young pullets.

Economic losses to the poultryman from intestinal coccidiosis are due primarily to the slowness with which many of the birds recover. The laying flocks may be unprofitable for several weeks.

Intestinal coccidiosis frequently appears soon after pullets are confined to the laying houses. Generally only a few birds are affected at first, but more develop symptoms from day to day until many are affected. Deaths occur mostly after several days to 2 or 3 weeks, but some die in the early stages. Many of the affected birds gradually regain their appetite, become stronger, and recover.

Loss of appetite, loss of weight, weakness, and an abnormal drop in egg production in pullets are some of the first indications of intestinal coccidiosis. The droppings may be watery or slimy, and greenish or brownish, or may consist almost entirely of bloody mucus.

The small intestine of a bird that has a severe case of intestinal coccidiosis may be greatly distended and have tiny white and red spots on the lining, which are visible on the outer wall (Eimeria necatrix); thickened intestinal walls, with numerous transverse white bars or streaks, which are visible from the outside as well as the inside and are particularly abundant in the intestinal loop or duodenum (E. acervulina): distended intestine, with walls thickened and filled with thick, greenish or brownish mucus (E. maxima); short, red streaks arranged in a ladderlike fashion in the lower part of the intestine and a cheeselike material in the narrow, tubular portion of the cecum (E. brunetti).

Three other species (E. praecox, E. mitis, and E. hagani) occur in the intestinal tract of chickens but are not known to be associated with any pronounced visible changes in the wall of the intestine.

TURKEYS harbor seven species of coccidia. One of them, Eimeria meleagridis, develops in the ceca. Three others, E. innocua, E. meleagrimitis, and E. subrotunda, develop in the intestine. The remaining, ones, E. adenoeides, E. dispersa, and E. gallopavonis, occur in the ceca and intestine.

The species that are most important apparently are E. adenoeides and E. meleagrimitis.

The symptoms of coccidiosis in turkeys are not distinctive or specific.

None of the species causes severe hemorrhage, such as occurs in severe cecal coccidiosis of chickens.

Affected poults eat very little, lose weight, and stand huddled together with drooping wings and ruffled feathers. They may discharge cylindrical fecal pellets or fluid droppings containing small amounts of blood, blood flecks, or plugs of mucus.

The injuries produced in the intestine and ceca of turkeys tell little about the species of coccidia present. All, except E. innocua and E. subrotunda, produce inflammation of the intestinal tract, with a whitish discharge. The intestine may be swollen, the walls thickened, and the lining congested with blood or whitened. The intestine may contain large amounts of fluid, white or green mucus, or a cheesy material. Small strands of clotted blood may occur in the droppings. The ceca may be distended with granular, creamy material or with a cheesy plug. The walls may be slightly thickened. Rows of bloody spots or petechial hemorrhages may occur on the lining.

SEVERAL IMPORTANT FACTS have been discovered in studies on coccidiosis of poultry: coccidia are present wherever Poultry is raised. Repeated light infections help the bird build up a resistance to the species it harbors, but not against the others. The severity of the disease depends largely on the number of oocysts swallowed. Young birds are usually affected more severely than older ones. The infection generally lasts only a short time, provided reinfection is prevented. Sick birds recover slowly, if at all, when treated. Resistant birds, although healthy, shed oocysts and thus serve as sources of infection, which may overwhelm others.

THE BEST WAY to control coccidiosis of poultry is to prevent severe infections, and the best way to do that is to develop resistance to the disease.

Birds that recover from a light infection become resistant to coccidiosis. Experimentally repeated light infections confer a stronger resistance than a single infection, whether it be light or heavy.

Farm-raised flocks generally suffer less from coccidiosis than flocks raised under crowded conditions. Because of the space over which farm birds can range, their chances of picking up heavy or fatal doses of coccidia are less great the droppings are scattered over a wide area and the sun and wind dry them quickly, so that the oocysts are destroyed.