Howarth became her country’s youngest Paralympian at the age of 13 when she competed in swimming at London 2012.

The following year, she was crowned world champion after winning the women’s 200 metres medley SM7 event in Montreal.

Howarth went on to compete at the Rio 2016 Paralympics, where she claimed the 200m medley SM7 gold medal and 50m butterfly S7 bronze.

Not satisfied with conquering Para swimming at global level, Howarth set herself a new challenge and in 2017 began her journey in Para cycling.

Less than one year after starting the sport, she competed at her first International Cycling Union Para-cycling Track World Championships in Rio de Janeiro.

In December 2018, Howarth broke the C4 flying 200m sprint world record at the Southland Track Cycling Championships in Invercargill.

Her time of 12.95sec took 0.248 off the previous record set by New Zealand Paralympian Kate Horan in February 2016.

"From the time I first set my sights on Paralympic success, I have worked hard and sacrificed a lot to achieve my goals," said Howarth, who was born with a bilateral upper limb deficiency.

"Para sport has provided me with amazing opportunities to be the best I can be across both Para swimming and Para cycling.

"I hope that many disabled New Zealanders get to experience what I have, like travelling around the world and making lifelong friendships while achieving goals.

"I feel as if I have achieved what I aspired to do and I am proud of that.

"The decision to retire has not come easily, however.

"Due to my auto immune disease, my body is no longer letting me continue to perform at the highest level. 

"I have always known there is much more to life than sport and I’m now ready to move on and develop my life in other areas. 

"I recently started a retail job that I am really enjoying and looking forward to see where that may lead in the future."

Howarth started swimming competitively aged seven before making her international Para swimming debut as a 12-year-old. 

She was inspired to one day win a Paralympic gold medal following a school visit from Athens 2004 Olympic cycling champion Sarah Ulmer.

"From the time Nikita was identified in Taranaki at the 2009 Independence Games as a nine-year-old, it was evident she had what it took to become a Paralympic champion," said Malcolm Humm, the high-performance director at Paralympics New Zealand (PNZ).

"Her swimming ability was obvious in all four strokes and she had a high desire to be the best in the world. 

"From the time she entered the PNZ Para swimming high-performance programme in 2011 she was a pleasure to work with – always committed, hardworking and she demonstrated a desperate desire to win. 

"Having won gold and bronze medals at the Rio 2016 Paralympic Games, Nikita transitioned into the PNZ Para cycling programme where she displayed the same qualities in terms of her motivation to perform at the highest level.

"She was a quick learner and relished the Para cycling environment culminating in her breaking the women’s C4 flying 200m sprint world record at the Southland Champs in December 2018. 

"We look forward to continuing to work with Nikita to identify ways in which she can continue to be involved in the Paralympic family. 

"We wish her all the best for the future."

Howarth was a key member of the New Zealand team that produced performances at Rio 2016 to make it the country’s most successful Paralympic Games. 

The team secured 21 medals – nine gold, five silver and seven bronze – across 12 individual podium finishers.

New Zealand ranked 13th on the medal table.

The team also defended its title of number one in the world for medals won per capita during London 2012.