THE TELOSPORASIDA AND THE COCCIDIA PROPER 



209 



3294, respectively, in chicks 3, 7, 14, 

 21, 28 and 42 days old, while with an in- 

 oculum of 80,000 oocysts it was 9, 31 and 

 169, respectively in chicks 7, 14 and 21 

 days old. 



Pathogenesis : E. maxima is slightly 

 to moderately pathogenic. Tyzzer (1929), 

 Brackett and Bliznick (1950), Scholtyseck 

 (1959) and Long (1959) studied its effects 

 on chickens. The asexual stages cause 

 relatively little damage, the most serious 

 effects being due to the sexual stages. 

 Brackett and Bliznick (1950) observed a 

 mortality of 35% in one group of young 

 chicks infected with 500,000 oocysts each, 

 but there were no deaths in another group. 

 The survivors lost some weight and then 

 gained less than the controls for a time, 

 but infection with 100, 000 oocysts had no 

 significant effect on weight gains. Long 

 (1959) observed no deaths in a group of 

 6-week-old chicks infected with 500, 000 

 oocysts each or in three 17-day-old chicks 

 infected with 1 million oocysts each, altho 

 diarrhea was present and the infected 

 birds gained less than the controls. Im- 

 munity is quickly produced. 



Berg, Hamilton and Bearse (1951) 

 found that inoculation of White Leghorn 

 laying pullets with 8000 oocysts each pro- 

 duced a mild infection and temporary 

 cessation of egg-laying. 



The principal lesions are hemorrhages 

 in the small intestine. The intestinal 

 muscles lose their tone, and the intestine 

 becomes flaccid and dilated, with a some- 

 what thickened wall. Short, fine, hair- 

 like hemorrhages in the intestinal wall are 

 sometimes present. There is a catarrhal 

 enteritis and the intestinal contents are 

 viscid and mucoid, greyish, brownish, 

 orange or pinkish, occasionally but not 

 usually with flecks of blood. 



Birds which recover soon return to 

 normal. 



EIMERIA MITIS 

 TYZZER, 1929 



Host: Chicken. 



Location : Anterior small intestine, 

 occasionally middle and lower small intes- 

 tine or even tubular part of ceca. 



Geographic Distribution : Worldwide. 



Prevalence : Common. 



Morphology : The oocysts are sub- 

 spherical, smooth, colorless, 10 to 21 by 

 9 to 18|u with a mean of 16 by 13 /i . A 

 micropyle is absent. An oocyst polar 

 granule is present. An oocyst residuum 

 is absent. The sporocysts are ovoid, 10 

 by 6(1, with a Stieda body, but without a 

 sporocyst residuum. The sporulation time 

 is 2 days. Edgar (1955) found some infec- 

 tive oocysts as early as 18 hours at 29° C. 



Life Cycle : The life cycle of this 

 species has been studied by Tyzzer (1929) 

 and Joyner (1958), the latter using a strain 

 derived from a single oocyst. The endo- 

 genous stages occur in the epithelial cells 

 of the villi and occasionally in the glands. 

 They lie against the host cell nuclei, and 

 below them more often than above accord- 

 ing to Tyzzer. However, Joyner stated 

 that the schizonts are nearly always super- 

 ficial; he illustrated the sexual stages as 

 below the host cell nuclei. The schizonts 

 produce 6 to 24 or rarely 30 merozoites, 

 but the number of schizont generations is 

 not known. The merozoites are crescent- 

 shaped, with blunt ends, and measure 

 about 5 by 1 . 5 /i . 



The microgametocytes are about 9 to 

 14 jj, long and the macrogametes are some- 

 what larger. In contrast to most other 

 coccidian species, in which development 

 following a single inoculum is quite syn- 

 chronous, both asexual and sexual stages 

 occur together. The prepatent period is 

 4 to 5 days, and the patent period 10 days 

 (Joyner, 1958). 



Joyner (1958) found that chicks in- 

 fected with 1000 oocysts produced 61, 709 

 oocysts per oocyst fed, while chicks fed 

 100,000 oocysts produced 2253 oocysts per 

 oocyst fed. 



Pathogenesis : This species is 

 slightly pathogenic, but is unlikely to be 



