You are not permitted to download, save or email this image. Visit image gallery to purchase the image.
Five breeding sites, all at the southern end of the peninsula, have been affected by the outbreak.
Wildlife vets from the New Zealand Wildlife Health Centre at Massey University met Doc staff, local vets, Yellow-eyed Penguin Trust members and a scientist from Penguin Place in Dunedin this week to discuss the latest outbreak.
At Boulder beach, more than 60% of the chicks showed signs of infection, 33 chicks died and several were missing -amounting to about 36% losses.
Chicks were also affected at Sandfly Bay and dead chicks were sent to the Massey centre in Palmerston North for postmortem examinations.
Avian diphtheria has hit the penguin chicks almost every second year since the first outbreak was noticed in 2002.
Doc ranger Mel Young was relieved the latest chick death toll had not, thus far, been as high as initially feared.
A "pretty scary situation" had arisen at Boulder beach several weeks ago because of the extensive infection there.
Intervention by providing antibiotics and rehydration fluids had since helped reduce chick losses, and the limited distribution of the infection was a positive feature, she said.
There had been a few early losses at other peninsula sites but most penguins survived the most critical period.
Breeding sites in the Catlins appeared unaffected and North Otago chicks seemed to be doing well, despite a few early losses.
It is believed the penguin chicks might have caught a virus and contracted the diphtheria as a secondary disease.
Doc's biodiversity assets programme manager for Coastal Otago, David Agnew, said the Dunedin meeting had heard that much information about the disease had been collected since 2002.
Analysis of this data had illustrated "the complex nature of the issue" and highlighted the benefit that more extensive research could bring "to solve the mystery of what's causing the disease", he said.
Penguin trust general manager Sue Murray said more funding was needed for studies to clarify exactly what was causing the disease problems every second year.
An application by Massey University for some state funding for a PhD student to study the diphtheria outbreak was unsuccessful last year, but other funding options were being considered.
Massey vet Kerri Morgan said a more extensive study would examine the wider influence of variables, such as weather and sea patterns, as they had not previously been considered.