204 



THE TELOSPORASIDA AND THE CCXTCIDIA PROPER 



rate and severity of cecal coccidiosis. 

 Chicks which recovered following severe 

 infection made much poorer weight gains 

 than mildly affected ones. Mayhew(1932, 

 1932a, 1934) found that it took 10 weeks 

 to 6 months after recovery before in- 

 fected birds regained the weight they had 

 lost in comparison with uninfected con- 

 trols. He found, too, that pullets which 

 had been infected when 6 to 8 weeks old 

 laid 19.25% fewer eggs than the controls. 

 In addition, severely affected birds began 

 to lay 6 to 7 weeks later than the controls. 

 Davidson, Thompson and Morre (1936) 

 compared a group of chickens which was 

 passing oocysts with another group which 

 was not. Over a period of 11 months, the 

 positive group had a 12. 1% higher mor- 

 tality, while the negative group averaged 

 0. 44 pounds heavier than the positive one 

 and had a 15.2% higher egg production. 

 Bressler and Gordeuk (1951) found, in a 

 flock of Single Comb White Leghorn chick- 

 ens which had survived a mortality of 

 8. 3% due to cecal coccidiosis, that weight 

 gains were slightly less than in a "control" 

 group fed 0.0125% sulfaquinoxaline con- 

 tinuously which had not suffered an out- 

 break of the disease, but that neither egg 

 production nor hatchability were impaired. 



EIMERIA NECATRIX 

 JOHNSON, 1930 



Host : Chicken. 



Location: The first and second gen- 

 eration schizonts are found in the small 

 intestine and the third generation schizonts, 

 gametes and gametocytes in the ceca. 



Geographic Distribution : Worldwide. 



Prevalence : Common. 



Morphology : The oocysts are oblong 

 ovoid, 12 to 29 by 11 to 24/1 with a mean 

 of20byl7/i (Becker e/ aZ. , 1956). The 

 oocyst wall is smooth and colorless, with- 

 out a micropyle. An oocyst polar granule 

 is present. An oocyst residuum is absent. 

 The sporocysts are elongate ovoid, with 

 a Stieda body. A sporocyst residuum is 

 absent. The sporulation time is 2 days 



(18 hours at 29'' C according to Edgar, 

 1955). 



Life Cycle : Chickens become in- 

 fected by ingesting sporulated oocysts. 

 When the sporozoites emerge. Van Door- 

 ninck and Becker (1957) found that they 

 first enter the epithelial cells of the villi 

 in the small intestine, pass thru the 

 epithelium into the lamina propria or core 

 of the villus and migrate toward the mus- 

 cularis mucosae. Most of them are en- 

 gulfed by macrophages en route and are 

 transported by them to the epithelial cells 

 of the fundus. The macrophages invade 

 these cells and appear to disintegrate 

 during or after the invasion process, leav- 

 ing the sporozoites unharmed. These then 

 round up to form first generation schizonts. 



The remainder of the life cycle has 

 been studied by Johnson (1930) and Tyz- 

 zer, Theiler and Jones (1932). Both the 

 first and second generation schizonts are 

 found above the host cell nuclei in the 

 epithelial cells of the gland fundi. The 

 first generation merozoites are liberated 

 2. 5 to 3 days after infection and enter ad- 

 jacent epithelial cells. The second gen- 

 eration schizonts are relatively large, 

 measuring 39 to 66 by 33 to 54 fi with a 

 mean of 52 by 38 /n . Most of the second 

 generation merozoites are liberated 5 to 

 8 days after infection, but a few may still 

 be liberated as long as 23 days after in- 

 fection. They measure 8 to 11 by 1. 5 to 

 2. /J with a mean of 9 by 2 /ii . They pass 

 to the cecum, where they penetrate the 

 epithelial cells, coming to lie below the 

 host cell nuclei, and turn into third gen- 

 eration schizonts. Most of them are 

 found in the surface epithelium, but some 

 enter the glandular epithelium. Multiple 

 infections of a cell with 3 or 4 schizonts 

 may occur. These third generation schi- 

 zonts are relatively small and contain only 

 6 to 8 or a maximum of 16 third genera- 

 tion merozoites. It is not certain whether 

 there is more than one asexual generation 

 in the cecum. 



The third generation and some of the 

 second generation merozoites enter other 

 cecal epithelial cells and become macro- 

 gametes or microgametocytes. These 



