The Public Health Ministry has sent 23 botulism antitoxin doses to Phayao's Phu Sang district after 33 villagers developed symptoms similar to the parasitic illness.

Another 30 doses ordered from the United States will arrive today, caretaker Public Health Minister Pinij Charusombat said yesterday.

Villagers from Tambon Chiang Raeng were admitted to Chiang Kham Hospital on Friday after eating barking-deer meat and complaining of stomach ache, nausea, vomiting, dizziness, blurred vision, breathing difficulties, stiffness of the tongue and eyelid droopiness.

The ministry will also send a six-member team from Nan Hospital with experience of treating botulism to help Chiang Kham staff, added Pinij, who said there had been no reports of any deaths among the patients.

Meanwhile, Dr Prat Boonyawongwirot, permanent secretary for public health, said 40 epidemic experts sent to investigate the case reported that 33 people - out of 192 who had eaten half-cooked barking-deer meat on June 27 to 28 - were hospitalised.

Doctors later discharged 25 patients, leaving eight in hospital - four of them severely ill with symptoms similar to those that affected 163 people in the outbreak of botulism in Nan province on March 14.

 The eight patients received the antitoxin on Friday. Doctors took their blood samples for tests at Chiang Mai's medical science centre. Deer meat was sent for testing for bacterial contamination.

Medical teams searched for more sick villagers in Tambon Chiang Raeng but no more cases were found.

Doctors have campaigned for villagers to eat cooked food and refrain from any kind of raw food.

The Nan outbreak of botulism, a rare and serious paralytic illness, happened after people ate contaminated fermented bamboo roots at a merit-marking ceremony.

The incident prompted authorities to import the botulism antitoxin for the first time.

The botulism strain found in the Nan incident was said to be so deadly that a mere 0.5 milligram synthesised into a biological weapon could kill up to 500,000 people.