THE TELOSPORASIDA AND THE COCCIDIA PROPER 



205 



also lie below the host cell nuclei. Micro- 

 gametes develop from the microgameto- 

 cytes, fertilization takes place, and 

 oocysts form and are released. The pre- 

 patent period is 7 days, and the patent 

 period is about 12 days. 



Brackett and Bliznick (1952a) reported 

 that the number of oocysts produced by E. 

 necatrix per oocyst fed ranged from 1 5 in 

 a group of chicks infected with 35,000 

 oocysts each to 58,000 in another group in 

 which the infective dose was 50 oocysts. 



Pathogenesis : Next to E. teiiella, 

 this is the most pathogenic and important 

 species of chicken coccidium. Indeed, 

 with the decrease in importance of E. 

 tenella due to the use of coccidiostatic 

 drugs, E. necatrix has come to the fore 

 in many areas as the cause of more losses 

 than E. tenella. 



E. necatrix is often said to cause a 

 more chronic type of coccidiosis than E. 

 tenella. This is not because it runs a 

 longer course, but because it produces so 

 much scar tissue in the small intestine 

 that its effects are more lasting. 



The pathogenesis of E. necatrix has 

 been studied especially by Tyzzer, Theiler 

 and Jones (1932). The principal lesions 

 are in the small intestine, the middle 

 third of which is most seriously affected. 

 Small, white, opaque foci are found here 

 by the fourth day after infection. They 

 are composed of second generation schi- 

 zonts developing deep in the mucosa. 

 They are so deep that they can be seen 

 thru the serosa but not from the mucosal 

 surface of the intestine. They are seldom 

 more than a millimeter in diameter, but 

 may coalesce and thus appear larger. 

 Severe hemorrhage may appear on the 

 5th or 6th days. The small intestine may 

 be markedly swollen and filled with clotted 

 or unclotted blood. Its wall is greatly 

 thickened, dull red, and many petechial 

 hemorrhages appear in the white, opaque 

 foci which by now contain second genera- 

 tion merozoites. The gut wall may lose 

 contractility, become friable and even 

 appear gangrenous. The epithelium may 

 slough, and by the end of the 6th day a 



network of fibrin containing mononuclear 

 cells appears in the destroyed areas. 

 This is later replaced by connective tissue, 

 and permanent scarring results which in- 

 terferes with intestinal absorption. 



There is less anemia than in E. 

 tenella infections. Using the microhema- 

 tocrit technic, Joyner and Davies (1960) 

 found that the packed red cell volume de- 

 creased from 28% to 23% seven days after 

 experimental infection with 20, 000 oocysts, 

 and to 25%) after infection with 10, 000 

 oocysts, but that there was no significant 

 decrease after infection with 1000 oocysts. 

 The hematocrit levels had not returned to 

 the original level 12 days after infection. 



The ceca are not seriously affected. 

 They may be contracted and their contents 

 may be dehydrated. 



Death usually occurs 5 to 7 days after 

 infection. Many of the birds which recover 

 remain unthrifty and emaciated. The 

 after-effects of this type of coccidiosis are 

 often so long- lasting that it is not worth- 

 while to keep birds which have recovered 

 from severe attacks. 



Brackett and Bliznick (1950, 1952) 

 found that inoculation with 25,000 to 

 50,000 oocysts (a relatively small number) 

 caused a high degree of mortality in young 

 chickens. Following inoculation with equal 

 numbers of oocysts, young birds are more 

 severely affected than older ones, but if 

 the inocula are calculated on a weight basis, 

 older birds may be more severely affected 

 than younger ones. In 3-week-old chicks, 

 25, 000 oocysts caused a mortality of 87%, 

 while in 4-week-old chicks, 18,000, 37,000, 

 75,000 and 150,000 oocysts caused mor- 

 talities of 8, 75, 85 and 61%, respectively. 



EIMERIA BRUNETTI 

 LEVINE, 1942 



Host : Chicken. 



Location : First generation schizonts 

 occur thruout the small intestine. Second 

 generation schizonts, gametes and gameto- 

 cytes occur in the posterior small intes- 

 tine, rectum, ceca and cloaca. 



