202 



THE TELOSPORASIDA AND THE COCCIDIA PROPER 



and kept dry. Manure should be removed 

 frequently. The animals should be han- 

 dled as little as possible, and care should 

 be taken not to contaminate either the 

 animals themselves or their food, utensils 

 or equipment. In addition, the rabbitry 

 should be kept as free as possible of in- 

 sects, rodents and other pests. 



EIMERIA TEN ELLA 

 (RAILLIET AND LUCET, 1891) 

 FANTHAM, 1909 



Synonyms : Eimeria avium, Coccid- 

 ium teiiellion, Coccidiu»i globosum, 

 Eimeria bracheti. 



Host : Chicken. 



Location: Ceca. 



Geographic Distribution : Worldwide. 



Prevalence : Very common. 



Morphology : The oocysts are broadly 

 ovoid, smooth, 14 to 31 by 9 to 25 ^t with 

 a mean of 22. 9 by 19. 1 p. . A micropyle is 

 absent. An oocyst polar granule is pres- 

 ent. An oocyst residuum is absent. The 

 sporocysts are ovoid, without a sporocyst 

 residuum. 



The sporulation time is 1 to 2 days. 

 Edgar (1954) found that the minimum spor- 

 ulation time is 18 hours at 29° C, 21 hours 

 at 26. 5 to 28 and 24 hours at 20, 24 and 

 32 . Maximum sporulation was reached 

 in 22 to 24 hours at 29 , the optimum 

 temperature. Some sporulation took place 

 at 41 ° . When the oocysts were kept at 8° 

 they failed to sporulate in 8 weeks and 

 most were killed, so that only a few spor- 

 ulated when they were subsequently held 

 at 28°. 



Life Cycle : The life cycle of E. 

 tenella has already been described as an 

 example of coccidian life cycles (p. 160). 



Pathogenesis : This is the most 

 pathogenic of the chicken coccidia and is 

 responsible for heavy losses. Together 

 with the other species, it was estimated 



by the USDA (1954) to cause an annual loss 

 of $38, 229, 000 in the United States due to 

 death and disease alone. To this should be 

 added the cost of the medicated feeds which 

 are generally fed to poultry, and various 

 labor and other costs entailed by disease 

 outbreaks. 



Cecal coccidiosis is found most fre- 

 quently in young birds. Chicks are most 

 susceptible at 4 weeks of age, while chicks 

 1 to 2 weeks old are more resistant (Gardi- 

 ner, 1955). However, day-old chicks can 

 be infected (Gordeuk, Bressler & Glantz, 

 1951). Older birds develop immunity as 

 the result of exposure. 



Coccidiosis due to E. tenella may vary 

 in severity from an inapparent infection to 

 an acute, highly fatal disease, depending 

 upon the infective dose of oocysts. The 

 pathogenicity of different strains of E. 

 tenella varies, and it is affected also by 

 the breed and age of the chickens and their 

 state of nutrition. Thus, Jankiewicz and 

 Scofield (1934) found that less than 150 

 sporulated oocysts produced no signs, 150 

 to 500 oocysts produced slight hemorrhagic 

 diarrhea, 1000 to 3000 oocysts produced 

 moderate hemorrhage and a few deaths, 

 3000 to 5000 oocysts produced marked 

 hemorrhage and moderate mortality, and 

 more than 5000 oocysts produced severe 

 hemorrhage and high mortality. However, 

 Horton-Smith(1949) found that infections 

 with 15,000 oocysts caused no mortality 

 in week-old birds, 30,000 oocysts caused 

 32% mortality and 60, 000 oocysts caused 

 45% mortality. Swales (1944) found that 

 in 6-week-old chickens 15,000 oocysts 

 caused 40% mortality, 30,000 oocysts 

 caused 44%i moi'tality and 200, 000 oocysts 

 caused 80% mortality, while in 4. 5-week- 

 old chicks 120,000 oocysts caused 90% 

 mortality and in 12-week-old chicks 

 100,000 oocysts caused 50'( mortality. 

 Waletzky and Hughes (1949) found that in 

 one experiment 20.000 oocysts produced 

 18-'; mortality and 100. 000 oocysts 36%. 

 mortality in 4-weck-old chicks, while in 

 other experiments 50, 000 oocysts produced 

 45*'( mortality in 7-week-old chicks, 

 100,000 oocysts produced 67'r mortality in 

 4- to 5-week-old chicks and 500,000 

 oocysts produced 48% mortality in 3- to 



