Specific-pathogen-free (SPF) chicks infected with infectious bursal disease (IBDV) virus at one day of age or midway (7 days) through a two-week immunization program for Eimeria tenella showed significantly less (P less than or equal to 0.05) protection against coccidal challenge as measured by lesion scores than chicks given IBDV after 14 days of coccidial immunization. The chicks showed complete protection to later coccidial challenge administered on Day 21. Bursae were markedly smaller from IBDV-infected chicks than from uninfected controls, and pathological changes were extensive. Virus-neutralization tests demonstrated that titers to IBD were higher in chicks exposed to the virus than in unexposed controls.

Monensin at 60, 80, or 100 ppm in feed reduced mortality and lesion scores while protecting against weight loss of turkeys infected with the major pathogenic species: Eimeria adenoides, E. meleagrimitis, and E. gallopavonis. With single and mixed infections in battery-cage experiments, the death rate of unmedicated turkey poults was 33-75%. Weight gains were significantly (P is less than or equal to 0.05) better with 100 ppm monensin than 60 ppm, as were also lesion scores. Under floor-pen conditions there were no significant differences among monensin treatments. Moisture content of the litter was significantly lower in all monensin-medicated pens (40%, compared with 52% moisture in pens of unmedicated controls).

Coccidial life-cytle stages were detected in the bursa of Fabricius of broiler chickens inoculated with Eimeria tenella, whether or not the chickens had previously been infected with infectious bursal disease virus (IBDV). Chickens infected only with E. tenella had developing parasites in the lining epithelium, whereas chickens with both infections had gametocytes also in the epithelial cells surrounding numerous degenerating bursal cysts.

The ultrastructural appearance of first-generation schizonts of Eimeria adenoeides was markedly altered in turkey poults fed 0.0125% amprolium-medicated feed. When compared with development seen in unmedicated control birds 48-72 hr postinoculation (PI), most of the schizonts present in the medicated birds were fragmented, contained enlarged nuclei, had swollen endoplasmic reticulum and Golgi apparatus, and showed no budding of merozoites. Other schizonts were almost completely degenerated and contained pyknotic nuclei, dense cytoplasm, and large intracytoplasmic vacuoles containing membrane whorls or lipid droplets. A few mature schizonts were seen in the medicated poults, and these did not appear to differ ultrastructurally from those seen in unmedicated control birds. Ultrastructurally normal second-generation schizonts and the sexual stages were also seen in small numbers in the medicated turkey poults 72-120 hr PI. Mature sexual stages were seen much earlier in medicated turkeys--at 96 hr PI--than in the unmedicated poults.