PARIS (Reuters) - Australia's triathletes have Blake Prestonbeen taking medicines to combat E.coli for a month, the team doctor said on Monday after they took precautions ahead of the event amid concerns over pollution levels in the river Seine.

The triathlon team of Luke Willian, Matthew Hauser, Natalie van Coevorden and Sophie Linn had earlier finished 12th in the mixed relay where the swimming leg was in the river Seine.

The four athletes also took part in last week's men's and women's individual triathlon events. The men's event was postponed due to pollution levels in the Seine.

"We started by administering a medication that's good against E.coli, which is the main bacteria in this water, a month ago," Carolyn Broderick told reporters.

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"After the race, we've also been using prophylactic antibiotics and we're using skin washes, ear washes, eye washes. So we're trying to account for everywhere that may get infected essentially and similarly for our marathon swimmers."

Four Australians are on the entry list for open water swimming -- Nick Sloman, Kyle Lee, Moesha Johnson and Chelsea Gubecka.

Belgium withdrew from the team event after Claire Michel, who took part in the women's individual triathlon on Wednesday, fell ill. The Belgian Olympic Committee, however, did not elaborate on her illness.

"I'm not exactly sure what other teams are doing," Broderick added. "But we've been in touch with infectious diseases experts and we've got good opinions prior to coming into that to try and minimize the risk."

The marathon swimming events over 10-km will be held on Thursday (women's) and Friday (men's).

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