GALLE: A stomach bug has laid low two star New Zealand cricketers during the ongoing first Test against Sri Lanka, an official said on Friday.

Batsman Jesse Ryder and wicket-keeper Brendon McCullum woke up sick on Friday morning and were confined to their hotel rooms as the fourth day's play began at the Galle International Stadium.

"They are very sick and I am not sure if, and at what stage, they will take part in this Test," Black Caps manager David Currie told reporters.

The immediate concern for the tourists was finding a reserve wicket-keeper for the rest of the Test since Ryder had been nominated to don the gloves if McCullum got injured.

"There was no one else in the playing XI who could keep wickets and we requested the Sri Lankans if we could call up reserve wicket-keeper Reece Young as a special case," said Currie.

"The Sri Lankans kindly agreed to our request and we are very grateful to them."

Rules do not allow anyone outside the playing XI from keeping wickets.

New Zealand will take the field in Sri Lanka's second innings with Young as wicket-keeper, but it was uncertain if McCullum and Ryder will be able to bat a second time.

Currie said five other players -- Jacob Oram, Jeetan Patel, captain Daniel Vettori, Tim McIntosh and Chris Martin -- had suffered stomach bugs since the Test started on Tuesday.