Examination and Comparison of Infectious Bronchitis Virus and Coccidia Vaccines and Vaccination Methods
Albanese, Grace Ashby
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Of the myriad of diseases affecting commercial chickens, infectious bronchitis and coccidiosis cause the most significant economic losses. Vaccination for both of these pathogens, infectious bronchitis virus (IBV) and Eimeria spp., occurs at the hatchery using mass application strategies. IBV vaccines are live attenuated viruses, delivering serotype-specific immunity. The Arkansas IBV serotype is the most frequently detected serotype in the field, so vaccination to protect against disease from this type is commonplace. The current vaccine, ArkDPI, is not efficacious, and an alternative Ark-type vaccine is needed. Ark99, once a commercial IBV vaccine strain, was passaged once in embryonating chicken eggs to produce the ArkGA vaccine candidate. After 60 passages in embryos, the ArkGA vaccine was highly attenuated and provided good protection against Ark-type challenge when vaccinating broiler chickens, and is a suitable alternative to the ArkDPI vaccine. Like IBV, Eimeria spp. vaccines are often applied in the hatchery by mass vaccination methods. Vaccines may be applied using an aqueous spray, or a gel applicator bar may be used, although this technique is newer and not yet validated versus the traditional spray method. Vaccination using both a highly viscous and less viscous gel, applied by bar, was compared with liquid spray. Oocyst shedding differed slightly between vaccinated groups, although all groups were equally protected from E. maxima challenge, indicating that all the vaccine applications tested are effective. In addition to coccidiosis vaccine application, oocyst species used in vaccines are critical, because coccidia produces only species-specific immunity in chickens. An Eimeria type, E. mivati, has been contested as a species since its discovery, although it is included in a commercially licensed vaccine. Many claims suggest that E. mivati is a variant of E. mitis. Next generation Illumina sequencing was used to compare the mitochondrial cytochrome C oxidase subunit I gene sequences of samples containing E. mivati with known Eimeria sequences. None of the E. mivati samples contained sequence that matched with E. mivati in GenBank, although all matched with E. mitis. This data provides further evidence that E. mivati is likely a variant of E. mitis, although further genome examination is needed.