Recently hit by injury and illness, swimmer Karin Prinsloo heads into the national championships in Durban today undercooked but determined to get the times she needs for the world championships. The gala at the Kings Park pool, from today until Saturday, also serves as the trials for the world championships in Kazan, Russia, in August.Prinsloo, SA's top female swimmer, was first hit by a back spasm so painful that she was forced to go to hospital.Then she was struck by tonsillitis, a recurring problem since before the Commonwealth Games last year."I'm having my tonsils removed next week," said Prinsloo, 25."Injuries I can't prevent, but tonsillitis I can."Prinsloo admitted she was not in shape, but added: "I'm not negative. I know I can't expect much but I'm still going to go for the qualifying times."Her quest starts in the 400m freestyle this morning, although she rates the 200m freestyle as her best event. She qualified for the 2012 Olympics in the 200m backstroke.National coach Graham Hill said there were several promising female swimmers, but said the focus for them this year would be international junior competitions.Prinsloo is potentially the only one capable of qualifying for Russia.She delivered her best international performance at a gala in Perth early last year when she beat Australian Olympic medallist Bronte Barratt in the 200m freestyle. Prinsloo was supposed to have been a contender at the Commonwealth Games, but she fell ill before the competition started.She said: "I'm just going to go out and try my hardest. Hopefully that will be enough."..