Disease in yellow-eyed penguins / hoiho
Penguins are susceptible to a range of infectious and parasitic diseases. Birds can be more susceptible to disease if they are stressed (environmentally or nutritionally) and their immune system is suppressed.
Avian diphtheria is the most common disease which affects young chicks in some seasons. Bacterial plaques form in the mouth and can be inhaled, causing aspiration pneumonia, or result in a blockage which prevents feeding and causes dehydration. Chicks which survive have reduced growth rates and often fledge in poor condition.
Disease has the potential to become a bigger issue in the future as the climate warms, and as human disturbance and stress on the penguin population increases.