At least five cases of gastro have been linked to Moo View Dairy's unpasteurised cow's milk, SA Health has warned.

Under South Australian law it is illegal to sell raw cow's milk.

SA Health said the Willunga Hill company's milk must be recalled.

The company's farmers, Mark and Helen Tyler, were fined more than $17,000 last year by a magistrate for selling unpasteurised milk contrary to the Food Act by setting up a share program in their dairy cows on their farm south of Adelaide.

Mr Tyler on Friday defended his company's raw milk product, saying they had only tried to "operate within the law".

"I don't believe that we've contravened the law," Mr Tyler said.

"We've clearly labelled the milk, that's all we can do [and] we specifically say that we can't sell it for human consumption."

SA Health director of public health Associate Professor Kevin Buckett said the sale of raw cow's milk for human consumption was illegal in Australia due to its high risk of contamination.

"We've confirmed at least five cases where people aged between three and 70 contracted gastrointestinal illness cause by the cryptosporidium parasite after consuming raw cow's milk products purchased from Moo View Dairy, and this number is likely to be higher," he said.

Associate Professor Buckett said the people did not require hospitalisation.

Associate Professor Kevin Buckett says the number of gastro cases was expected to rise. ( ABC News: Rebecca Opie )

"It is important to remember that raw cow's milk products should not be consumed as they can contain harmful bacteria such as E. coli, salmonella, campylobacter, and listeria, as well as cryptosporidium," he said.

Associate Professor Buckett warned that listeriosis was often fatal in immunocompromised people, and could cause fetal death if contracted by a pregnant woman.

"Pasteurisation is crucial because it kills dangerous pathogens without altering the flavour of milk or adversely affecting its nutritional value."

He called for people with the milk to throw it out.

The recalled products are sold in one-litre, two-litre and three-litre plastic bottles and labelled: The SA Government declares this RAW COW'S MILK NOT FIT FOR HUMAN CONSUMPTION.

Farmer describes case as 'circumstantial'

The dairy sells the milk online through their website.

Mr Tyler said SA Health had not provided him with any firm evidence to suggest his product had caused the gastro cases in question.

"All we have been told is that five people that have been diagnosed with [a gastro-causing virus] have said that they have drunk our milk in a period of time before they got sick," he said.

"There's no proof of any link and it appears that these cases were spread over a large period of time.

"[Gastro] is something that has been going around in the community so it's just circumstantial evidence that they've shown that there's five people but no link.

"It seems the weight of numbers over time has built a bit of a story."

A snapshot of the Moo View Dairy website. ( Moo View Dairy website )

The company's website said they wanted to keep working with authorities to prove "we can produce raw milk of a standard that has no greater risk than numerous other foods that are available".

"In our store you will have the opportunity to purchase raw cow's milk that is NOT FIT FOR HUMAN CONSUMPTION.