The Biological Characteristics Of A Native Strain Of E.brunetti And Its Precocious Line

The biological characteristics of Tangyin strain of Eimeria brunetti isolated in Tangyin County, Henan province, China and its precocious line were studied.Oocysts of Tangyin strain of E.brunetti averaged 29.2×22.5μ with a minimum sporulation time of 21 hours and the minimum prepatent period of this strain was 119 hours. The pathogenicity of Tangyin strain was higher than all Eimeria species in chicken but E. tenella and E.necatrix.The signs of the chickens given 200,000 or 20,000 oocysts / bird first appeared on the 4th day PI (post infection). Dark brown liquid feces tinged with blood were passed by the chickens. Birds were not eating and their feathers were ruffled. Death occurred on 5th and 6th day PI. The mortality rates of chickens given 20,000 and 200,000 oocysts / bird were 3% and 6% respectively. Weight gains of chickens given 2,000 oocysts were much lower than and significantly different from those of control groups. Typical lesions were observed mainly in the lower intestine some inches above the ceca, the narrow tubular portion of ceca and the rectum. The middle and lower small intestine had pin point lesions and the lumen contained shreds of salmon colored materials which might represent the sloughed mucosa. The tubular or dilated portion of ceca plugged with dehydrated normal contents in combination the dry clotted blood. By day 7 or 8, the surviving birds began eating and gradually recovered to the normal state. The immunogenicity of this species is probably the strongest among the Eimeria species in chickens. Results showed that chickens inoculated with 200 sporulated oocysts were completely protected against heavy challenge with 200,000 oocysts / bird. Tangyin strain of E.brunetti was sensitive to robenidine, clopidol, slight resistant to maduramycin, nicarbazin, strong resistant to amproliun, zoalene, diclazuril and salinomycin.A precocious line of Tangyin strain of E.brunetti was obtained by selection for early development of oocysts (Jeffers, 1975). The reduction of the prepatent period from 119 to 90 hours was achieved over 16 serial passages. The oocysts averaged 22.9×19.0μ were smaller than those of parent strain. The precocious line was much less pathogenic than the parent strain judged by mortality and weight gains, but its immunogenicity was reduced to some degree. Histological studies showed that the endogenous development of the precocious line and the parent strain were similar during the first 72 hours of the infection. The nearly mature oocysts were seen at 84 hours in the intestinal tissue of chickens given the precocious line while the early oocysts were not found until 114 hours for the parent strain. The trait of early development of the precocious line was kept stable after 5 relaxed passages (no selection pressure).