I cannot find any information on there website or instructions indicating that Virkon will kill Coccidiosis. Virkon is effective on viruses,bacteria and fungi. Coccidiosis is parasitic,and Virkon will not kill parasites. As for claim to kill Marek's,i personally believe this is misleading and i am sceptical on this claim. Birds infected with Marek's can be carriers and shedders for life,therefore virus will always be around.