New in vitro drug assay system to fight coccidiosis in poultry
Researchers funded by Australian Research Council and the Phibro Animal Health Corporation have taken the first steps in identifying new drug targets to protect chickens against Eimeria parasite, one of the most important pathogens of commercial poultry.
Researchers at the University of Technology, Sydney have developed a new in vitro drug assay system to be able to study potential new targets found in the sexual (gametocyte) stages of the Eimeria parasite which causes the disease coccidiosis. The world-wide cost of coccidiosis control exceeded 1 billion US dollars in 2012 making Eimeria spp. the most important parasite of the commercial poultry industry globally. Current control strategies include antimicrobial drugs or vaccines derived from live parasites. Both of these approaches are becoming harder to implement due to widespread drug resistance and the high cost and lower efficacy of live vaccines.
The current research focused on the gametocyte cytoskeleton based on its central role in transporting material to the cell surface membrane where the hardy oocyst wall is built encasing the transmissible form of the parasite, the oocyst. Results showed that when targeted by anti-cytoskeletal drugs, the parasite’s ability to complete oocyst wall formation was abolished and so this targeted approach shows promise as the basis for a new transmission control strategy.
The protein actin, identified in the study entitled ‘F-actin distribution and function during sexual development in Eimeria maxima‘ published in the journal Parasitology was found to play a crucial role in the early stages of oocyst wall biosynthesis and development. It is highly expressed in gametocytes, and binds to specialised vesicles called wall forming bodies (WFBs). These WFBs carry the building blocks (i.e. tyrosine rich Gam56 and Gam82 glycoproteins, neutral lipids, and β glucans, amongst others) of the multi-layered oocyst wall, giving rise to an impervious, highly resilient oocyst.
Until recently, the mechanisms by which the WFBs are synthesized and transported to the surface were largely unknown. With the current work to set up an in vitro gametocyte culture system together with 3D high-resolution imaging technologies, these researchers have produced a much more detailed picture of how developing Eimeria oocysts synthesise the wall forming bodies and transport their cargo to the forming oocyst wall. This is a great example of how studies on the fundamental biology of the encystation process of the Eimeria parasite can potentially lead to the development of new, urgently needed strategies in the fight against coccidiosis.