This condition causes progressive degeneration of the nerve cells that control muscles. There is no known cause for MND, and no cure. Most people with motor neurone disease live just a few years beyond diagnosis.
The diagnosis had a massive impact on Gavin and his family, says Shayne.
"We have a son and daughter-in-law and a 4-year-old grandson. This has been huge for us. With MND you don't know how fast or slowly it's going to progress. There are different categories and everyone is different. Gavin is affected all down his left side, and his speech and swallowing have been affected."
Gavin has had to leave his job with PFP Fertilisers, and while he can still drive and is able to walk short distances, his speech is difficult to understand and he can no longer eat solid food.
This weekend's Walk 2 D'Feat MND will help raise awareness of the disease and its effects, Shayne says.
"When Gav speaks it can sound like he's drunk. It's worse when he's tired. He has a card to show people that explains his speech. When we go to a cafe or out for a meal he has to have his food pureed.
"People need to understand and make allowances, be aware. There are a lot more people with MND than ever before, and Hawke's Bay has a very high percentage of cases."
Shayne says being in CHB has made them feel like the "luckiest people in the world" since Gavin's diagnosis.
"The support in this community and from nurses, occupational and speech therapists and our medical team has made us feel very fortunate and humbled. It is marvellous how they are looking after us."
Shayne says the family are taking every day as it comes.
"We don't know how Gav will be in another month. He gets tired, he's had to learn how to slow down, how to accept help."
Gavin is taking part in an international research programme through Auckland University, looking at possible genetic causes for MND.
"As a family we are very proud of him. I call him a legend, he's amazing. We call our grandson 'Poppa's medicine' as he always makes Gavin laugh. We're all standing by each other, making the most of life as everybody should. We've learned if you see an opportunity, take it. If it's a beautiful day, get out in it."
• Walk 2 D'Feet MND starts from Napier Sailing Club at Ahuriri at 9am on Sunday, November 10. $15 to register, pre-registration required. To register go to mndwalk.org.nz