Abstract
Hoiho/yellow-eyed penguins (Megadyptes antipodes) are classified as an endangered species, forecast to become extinct on mainland New Zealand in one to two decades. Respiratory distress syndrome (RDS) is a newly emerged disease that has resulted in mortality for up to 30% of the hatched chicks per season with a >90% mortality rate for affected chicks. A recently identified virus called yellow-eyed penguin gyrovirus (YEP-GV) is strongly associated with RDS in young chicks. Chicken Anaemia Virus (CAV) is a closely related gyrovirus with an approved vaccine that is administered to hens prior to laying to prevent chick mortality. To determine if the CAV vaccine could provide cross-protection against YEP-GV, an in vitro neutralisation assay was developed to determine if sera from vaccinated hens could neutralise YEP-GV. If cross-reactivity was observed, it may be possible to repurpose the CAV vaccine to protect hoiho chicks from YEP-GV. As a newly discovered virus in the Anelloviridae family, YEP-GV, has been challenging to grow in culture and also visualise on electron microscopy in diseased tissue. This study trialled different in vitro virus propagation methods including using stem cells from recently hatched hoiho eggs, primary hoiho bone marrow cells and the MDCC-MSB1 chicken cell line. Primary bone marrow cells harvested from yellow-eyed penguins that were euthanised due to unsurvivable health conditions were successfully cultured in vitro for the first time. Bone marrow cultures were maintained for up to 14 days, and these may provide a suitable foundation for further diagnostic and therapeutic assays. Productive YEP-GV propagation using the MDCC-MSB1 chicken cell line; and attempts to purify virus-like particles (VLPs) produced after inoculating MDCC-MSB1 chicken cells with YEP-GV were unsuccessful, as determined by PCR, Nanopore sequencing and liquid chromatography mass spectrometry (LC-MS). Finally, testing of historic samples for YEP-GV in egg samples indicated that this virus may be vertically transmitted and is generally widespread within hoiho. Investigations into the characteristics of this highly fatal emergent virus and developing potential preventative measures are essential for preserving the population of the rarest penguins in the world.