Western lowland gorillas Lope and Ozala at Twycross Zoo.

Age-related degeneration could play a part

A Europe-wide study is hoping to find out why great apes such as chimpanzees and gorillas suffer from heart disease.

The Ape Heart Project is being led by Twycross Zoo in collaboration with the University of Nottingam. Dr Victoria Strong is the first of several doctoral students to begin work on the 10-year study. She aims to pinpoint the most common type of heart disease affecting primates and why they develop it.

"At the moment we're unsure why great apes in human care develop heart disease," she explained. "We also have yet to find out whether their wild counterparts are affected to the same degree."

Dr Strong believes the answer could be age-related degeneration, as primates in zoos tend to live longer than their wild counterparts, as they are not facing threats such as predation, poaching and infectious diseases.

Coronary heart disease (ischaemic heart disease) is the most common cause of death in humans, both in the UK and worldwide. In people, it is linked to lifestyle factors such as poor diet and a sedentary habits. But researchers do not currently believe these lifestyle factors explain the mortality of primates in captivity.

Dr Strong said: "In humans we commonly see the build-up of fatty deposits that causes atherosclerosis, which is caused by eating badly and exercising rarely, but so far this is not what we are seeing in apes.

"In the apes we are observing the death of the cardiac muscle, which is then replaced by scar tissue. At present we do not know what might be causing heart tissue degeneration, but we are looking into the role that genetics, nutrition and even viruses might play."

So far, the Ape Heart Project has carried out a retrospective mortality review across all great ape collections in European zoos over an 11-year period, ending in 2014. Researchers found heart disease to be a major cause of death in adult chimps, bonobos and gorillas. The results are expected to be similar for orang-utans when data analysis is complete.

Researchers are receiving the hearts of great apes that die in zoos and sanctuaries worldwide and detailed pathology is being carried out to determine if heart disease was the cause of death. The team are working alongside Professor Mary Sheppard, a human cardiac pathologist and sudden cardiac death specialist at George's University in London.

Dr Strong is working with veterinary pathologist Dr Kerstin Baiker and has produced a protocol to standardise cardiac post-mortem examinations and sample collecting, after the project highlighted major differences in approaches used by European zoos. Guidelines have also been produced by the project to improve heart screening in European Zoos, helping them to identify heart disease while there is still time for treatment.

Image © Lucy Ray