234 



THE TELOSPORASIDA AND THE COCCIDIA PROPER 



Fig. 30. Sporulated oocyst of Eimeria lab- 

 beana of the pigeon. X 1700. 

 (From Nieschulz, 1935) 



16 to 22 11 (usually 19 to 21 by 17. 5 to 20 fi ) 

 with a mean of 20 by 19 ji. On the other 

 hand, Duncan (1959), in a study of infec- 

 tions in more than 300 pigeons, measured 

 a large but unspecified number of oocysts 

 at various times during the patent period 

 and found that the overall range was 14. 5 

 to 24 by 13 to 22. 5 (i with an overall mean 

 of 19 by 11 IX . However, smaller oocysts 

 appeared early in the infection in 13 birds, 

 and in 10 of them they increased in size to 

 approximately the overall average by the 

 end of the patent period. These small 

 oocyst strains averaged 15 to 18 by 14 to 

 17ji. It would appear, therefore, that £. 

 columbarum is a synonym of E. labbeaiia. 



Life Cycle : Nieschulz (1925a) des- 

 cribed the endogenous stages and also gave 

 one of the few descriptions extant of early 

 sporogony in the coccidia. Soon after the 

 macrogametes are fertilized and the 

 oocysts are formed, the zygote contracts 

 into a ball within the oocyst wall. A fer- 

 tilization spindle then forms; it is a clear 

 band which passes thru the center of the 

 sporont and forms extensions which reach 

 to the oocyst wall. This band then dis- 

 appears and the sporont rounds up again, 

 but a refractile granule is left in the 

 oocyst. Altho Nieschulz did not recognize 

 it as such, this was undoubtedly reduction 

 division with the throwing off of a polar 

 granule. Four prominences form on the 

 sporont, which then divides to form 4 

 spherical sporoblasts. These become 

 rather triangular or elongate ovoid, and 

 a clear area appears at the pointed end 

 (pyramid stage). The sporoblasts round 

 up again, and finally elongate to form 

 elongate ovoid, pointed sporocysts in 



which the sporozoites develop. The spor- 

 ulation time is 4 days or less (Duncan, 

 1959a). 



After the sporulated oocysts are in- 

 gested, the sporozoites are released and 

 invade the epithelial cells of the intestine. 

 They round up and grow into mature schi- 

 zonts in 3 days. Each schizont produces 

 about 15 to 20 merozoites, often leaving a 

 residual body. The merozoites are some- 

 what crescent-shaped, pointed at the ends, 

 and 5. 5 to 9 /J. long. There is a second 

 generation of schizonts which Nieschulz 

 thought might be extracellular. These are 

 elongate, up to 18 by 5 ^i, and form up to 

 16 merozoites. 



The microgametocytes form a large 

 number of biflagellate microgametes about 

 2>\i long with flagella 10/i long. The ma- 

 crogametes have a row of large plastic 

 granules around their periphery. Nieschulz 

 figured what was probably a fertilized ma- 

 crogamete in which a microgamete nucleus 

 was approaching the macrogamete nucleus 

 in a clear pathway thru the cytoplasm. 

 After fertilization, the plastic granules 

 coalesce to form the oocyst wall. Oocysts 

 first appear in the feces 6 days after in- 

 fection. 



Pathogenesis : E. labbeatia is 

 slightly to markedly pathogenic, depending 

 in part upon the age of the birds (Levi, 

 1957). Adults are fairly resistant, altho 

 fatal infections have been seen. The birds 

 become weak and emaciated, eat little but 

 drink a great deal, and have a greenish 

 diarrhea. The heaviest losses occur 

 among squabs in the nest. A high percent- 

 age of the squabs may die, and those which 

 recover are often somewhat stunted. 



The principal gross lesion is inflam- 

 mation thruout the intestinal tract. 



Diagnosis : Diagnosis depends on 

 recognizing the oocysts and other stages in 

 the intestine in association with the signs 

 and lesions of the disease. 



Treatment : According to Lindsay 

 (cited by Levi, 1957), sulfaquinoxaline is 

 effective against E. labbeana. 



