Evaluation of an Experimental Irradiated Oocyst Vaccine to Protect Broiler Chicks Against Avian Coccidiosis

Abstract

The current study investigates the use of irradiated oocysts to protect broiler chicks, raised on litter, from infection with multiple species of Eimeria. In order to determine the optimum radiation dose for each Eimeria species, 1-day-old chicks were immunized with oocysts of Eimeria maxima, Eimeria acervulina, or Eimeria tenella exposed to gamma radiation ranging from 0-500 Gy. The litter oocyst counts at 7 days postimmunization, and the effect on weight gain following a challenge infection, decreased with an optimum dose between 150-200 Gy. Based on this finding, broiler chicks were immunized with a mixture of E. maxima, E. acervulina, and E tenella that had been exposed to 150 or 200 Gy. This resulted in more than a 100-fold reduction in litter oocyst counts and significant protection from a challenge infection, as measured by improved weight gain and feed conversion ratio (FCR). Immunization of birds with oocysts receiving 200 Gy was less effective in providing protection from a challenge infection. An additional formulation of vaccines containing two different oocyst doses of the three species that had been irradiated with 150 Gy were evaluated in their ability to attenuate oocyst output and convey protection to challenge. Results were similar with both high and low numbers of irradiated oocysts. Immunized chicks shed less oocysts at 7 days postimmunization and were protected from negative effects of challenge infection as measured by FCR, changes in weight gain, lesion scores, and measurement of body composition. However, the level of protection was somewhat less than that achieved by immunization with nonirradiated oocysts. The overall conclusion is that an irradiated oocyst vaccine developed in this study can effectively protect chicks that are raised on litter from challenge infection with multiple species of Eimeria, comparable to vaccines with virulent or precocious strains.

Chicken Coccidiosis: From the Parasite Lifecycle to Control of the Disease

“…The goal of attenuation is to decrease the pathogenicity of the parasite and therefore, its deleterious effects on the host. Several methods of attenuation have been used, including, selection for precociousness (124), irradiation (125), chemical treatment (126) and serial passage in chicken embryos (127). Precocious lines of Eimeria are characterized by a shortened endogenous life cycle due to the elimination of one or more schizogonies, leading to less damage to the intestinal tract and decreased production of oocysts.…”

Immunological and histopathological evaluation of Eimeria tenella oocysts Egyptian local isolate vaccine and its comparative efficacy with a commercial live vaccine

“…Vaccines have been used in poultry industry for more than 50 years, primarily in broiler breeder and replacement layer flocks (Chapman et al, 2002). Different types of vaccines have been made to immunize chicken against coccidiosis throughout the world by using low doses of sporulated oocysts (Shafiya et al, 2017), irradiated sporulated oocysts (Raymond et al, 2014), sporozoites (Garg et al, 1999), merozoites, recombinant merozoite antigen (Jenkins, 1998), recombinant refractile body antigen (Kopko et al, 2000) and sonicated oocyst (Akhtar et al, 2001;Kadhim, 2014). Generally, vaccination against Eimeria spp.…”

Expression of host defense peptides in the intestine of Eimeria-challenged chickens

“…Precocious strains show attenuated virulence but can still induce immunity. One drawback to the use of precocious strains is the additional labor and time required for numerous rounds of selection through naïve birds (Sharman et al, 2010;Chapman, 2014;Fetterer et al, 2014). There are 2 major types of anticoccidial drugs: coccidiostats and coccidiocidals.…”