Studies on the immunogenicity of seven attenuated lines ofEimeriagiven as a mixture to chickens

Abstract

SUMMARYThe ability of attenuated lines of all the seven species of Eimeria which infect the chicken to provide protection against challenge with virulent strains was examined. The parasites were given as a mixture of all seven species to chickens kept on litter in floor pens, by spraying an aqueous suspension of oocysts on to the surface of food in troughs within the floor pens. Treated chickens were challenged 4 weeks later with virulent strains, and changes in weight gain and the presence of gross intestinal lesions were determined. When used in this way, as freshly passaged oocysts or after storage for 3 or 6 months, the consistently good protection afforded by the attenuated lines suggests that they could be applied in the control of coccidiosis in the field. INTRODUCTIONAttenuated lines of Eimeria spp., produced either by repeated selection for early development of oocysts (precocious lines) or by serial passage in embryonated eggs, have been described for each of the seven recognised species which parasitise the chicken. The immunogenicity of an egg-adapted (TA) line of E. tenella has been studied under simulated field conditions (e.g. Long and Millard, 1977) whilst the immunogenicity of each precocious line has been separately confirmed using chickens kept in wire-floored cages (see McDonald et al., 1982;McDonald and Ballingall, 1983; Shirley and Bellatti, 1984; Shirley et al., 1984;McDonald et al., 1986. However, before attenuated lines can be used for the vaccination of commercial poultry it is first necessary to examine, under laboratory conditions, the ability of the lines to immunise when given as a mixture of all seven species to chickens. This paper describes the results of experiments in which, for the first time, attenuated lines of all seven species were given in combination to chickens.

Control of poultry coccidiosis: changing trends

“…The most important feature of these attenuated lines is their reduced proliferative capacity resulting in less damage to the intestinal epithelium after one passage through the gut. Paracox Ò (precocious strains; Shirley and Millard 1986) and Livacox Ò (precocious: TA strains, Bedrnik, 1989) are the example of such attenuated vaccine and the performance was comparable to anticoccidial drugs (Williams et al 1999). …”

Coccidiosis in poultry: anticoccidial products, vaccines and other prevention strategies

“…remaining Eimeria spp. in Livacox Shirley and Millard 1986;Shirley et al 1995;Shirley and Bedrnik 1997). Precocity is characterized by a shortened endogenous life-cycle due to the fact that the number of generations of schizogony is decreased because last generations of schizogony disappear by selecting early oocysts.…”

“…As a consequence, the number of oocysts produced during infection is reduced. However, the immunizing potential is maintained (Jeffers 1975(Jeffers , 1986McDonald et al 1986;Shirley and Millard 1986).…”

Ionophore toxicity in chickens: A review of pathology and diagnosis

“…Immunity in chickens to Eimeria tenella can be achieved by giving them daily doses of between one and 20 infective oocysts daily (Joyner & Norton, 1973). Recently, work on live attenuated vaccines has achieved some success (Shirley & Millard, 1986;Shirley & Bellatti, 1988). Advances towards a genetically engineered vaccine have also been made (Ellis & Tomley, 1991).…”