THE TELOSPORASIDA AND THE COCCIDIA PROPER 



203 



6-week-old chicks. Gardiner (1955) found 

 that 200, 000 oocysts were required to pro- 

 duce mortality in 1- to 2-week-old chicks, 

 while 50,000 to 100,000 oocysts produced 

 mortality in older birds. 



Cecal coccidiosis is an acute disease 

 characterized by diarrhea and massive 

 cecal hemorrhage. The first signs appear 

 when the second generation schizonts be- 

 gin to enlarge and produce leakage of 

 blood into the ceca. Blood first appears 

 in the droppings 4 days after infection. 

 At this time the birds appear listless. 

 They may become droopy and inactive, 

 and eat little, altho they still drink. The 

 greatest amount of hemorrhage occurs on 

 the 5th and 6th days after infection. It 

 then declines, and oocysts appear in the 

 feces 7 days after infection if the birds 

 live that long. The oocysts increase to a 

 peak on the 8th or 9th day and then drop 

 off very rapidly. Very few are still being 

 shed by the 11th day. A few oocysts may 

 be found for several months. 



Coccidiosis is self-limiting, and if 

 the birds survive to the 8th or 9th day 

 after infection, they generally recover. 



The lesions of cecal coccidiosis de- 

 pend upon the stage of the disease. They 

 have been described by Tyzzer (1929), 

 Tyzzer, Theiler and Jones (1932) and 

 Mayhew (1937). On the fourth day after 

 infection, hemorrhage is present thruout 

 the cecal mucosa. On the fifth day, the 

 cecum is filled with large amounts of un- 

 clotted or only partly clotted blood. This 

 increases on the sixth day. Cecal cores 

 of fibrinous and necrotic material begin 

 to form on the 7th day. They adhere 

 tightly to the mucosa at first, but soon 

 come loose and lie free in the lumen. 



About 7 days after infection, the wall 

 of the cecum changes color from red to 

 mottled reddish or milky white due to the 

 formation of oocysts. It is greatly thick- 

 ened. The cecal core, which was at first 

 reddish, becomes yellowish or whitish. 

 If it is small enough, it may be passed in- 

 tact in the feces, but usually it is broken 

 up into small pieces. In a few days the 

 cecum becomes normal in appearance or 



at most slightly enlarged and thickened. 

 Occasionally the cecum may rupture or 

 adhesions may form. 



About the 4th day, when the second 

 generation schizonts are developing, the 

 lamina propria becomes infiltrated with 

 eosinophiles, there is marked congestion, 

 and the cecal wall is thickened. The 

 epithelium may be torn and coccidia, blood 

 and tissue cells may be released into the 

 lumen in areas where there are large 

 numbers of parasites. On the 5th day, 

 when the second generation merozoites 

 are released, their host cells are ruptured 

 and there is extensive epithelial sloughing. 

 The sloughed material and cecal contents 

 consolidate to form the cecal core, which 

 loosens from the wall as the epithelium is 

 regenerated. 



Epithelial regeneration is complete in 

 light infections, but in severe ones it may 

 not be. There is a marked inflammatory 

 reaction, with extensive lymphoid and 

 plasma cell infiltration, and there may be 

 some giant cells. Connective tissue is in- 

 creased. The epithelium may not be re- 

 placed between the glands, and cysts 

 formed by constriction of the glands during 

 the inflammatory stage may persist. 



The loss of blood into the ceca causes 

 anemia. Using the microhematocrit tech- 

 nic, Joyner and Davies (1960) found that 

 the packed red cell volume decreased 

 markedly beginning 5 days after experi- 

 mental infection. From an original level 

 of 26 to 29% it decreased to 18% and 14%, 

 respectively, 7 days after infection with 

 2000 and 10,000 oocysts. It had returned 

 to normal 5 days later. 



Natt (1959) found that E. tenella 

 causes marked changes in the leucocyte 

 picture. He observed lymphopenia and 

 heterophilia on the 5th day, and eosino- 

 philia on the 10th day after infection. A 

 marked leucocytosis began on the 7th day 

 and persisted thru the recovery phase. 



Birds which recover from coccidiosis 

 may suffer ill effects for some time or 

 even permanently. Gardiner (1954) found 

 an inverse correlation between growth 



