Attenuation of Eimeria mivati (= mitis) by selection for precocious development

Area of Science:

• Veterinary Parasitology
• Coccidiosis Research
• Poultry Health

Background:

• Eimeria mivati causes coccidiosis in chickens, impacting poultry health and productivity.
• Attenuating Eimeria strains is a common strategy for developing anticoccidial vaccines.

Purpose of the Study:

• To investigate the characteristics of an Eimeria mivati strain selected for early oocyst development.
• To compare the pathogenicity, immunogenicity, and reproductive potential of this precocious strain with an egg-adapted attenuated line.

Main Methods:

• Serial passage of the Houghton (H) strain of Eimeria mivati in chickens to select for early oocyst development.
• Inoculation of chickens with the selected precocious strain and an egg-adapted attenuated strain.
• Assessment of pathogenicity (weight loss), reproductive potential (oocyst production), and immunogenicity (protection against challenge).

Main Results:

• The precocious E. mivati strain exhibited a >20-hour reduction in pre-patent period compared to the H strain.
• The precocious parasite was less pathogenic and had reduced reproductive potential but still induced protection against challenge.
• Both the precocious and egg-adapted strains were immunogenic, with neither causing significant weight loss in inoculated chickens.

Conclusions:

• Selection for early oocyst development is a viable method for attenuating Eimeria mivati.
• The resulting precocious strain demonstrates reduced pathogenicity and significant immunogenicity, making it a potential candidate for anticoccidial vaccines.
• Further research into the mechanisms of attenuation and protective immunity is warranted.