Signs of an increase in bovine TB across camelids, swine and domestic animals could strengthen the case for a badger cull, agricultural experts have predicted.

Latest figures released by the Department of the Environment, Food and Rural Affairs (Defra) appear to show only 28 alpacas, along with a handful of pigs, cats and dogs, have died after being infected with the disease in the first six months of this year.

But those in the industry say the statistics are "misleading", due to the way the data is collected. They have now called on Defra to tighten up bovine TB (bTB) controls for non-bovine species in England, and argue in favour of an organised cull of badgers – the creature many farmers state is at the centre of spreading the disease.

Members of an alpaca TB support group have reported the loss of 155 animals to the disease between them in the first seven months of this year, in heavy contradiction to Defra's record of 28 alpaca deaths.

Dianne Summers, welfare officer of the Cornwall Alpaca and Llama Group, said many herds have been infected in the Westcountry, an area where any future badger cull is likely to be tested due to the species' density.

Miss Summers, from Redruth, said: "Defra's figures are misleading to say the least.

"Defra is reporting 28 alpaca deaths, yet I have been contacted by someone who has lost 37 of their 52-strong herd to bTB. I am also aware of 35 herds under restriction at the moment – last year there were 11. Action needs to be taken."

Alpacas can fetch anywhere from £4,000 to up to £20,000 each for stud males. However, if an alpaca herd is found to be infected with bTB, it can be placed under restriction preventing them from being sold or studded out.

Miss Summers said this threat to an alpaca farmer's income has meant some refuse to let inspectors onto their land – something the alpaca owner is legally obliged to do.

She is campaigning for bTB controls on camelids in England to put on the same footing as those applying to cattle, including routine testing.

Ian Johnson, spokesman for the NFU South West, supported Miss Summers' calls for action and said he agreed the figures could support the argument for a badger cull. He added: "I think it is clearly a very undesirable situation to have any kind of disease running rampant or undetected, trying to control one part of it with a draconian regime of restricted movement and almost constant testing.

"What is the point if at the same time, we have a creature which is a carrier of the disease but not subject to any restrictions or controls? It is like trying to wipe out MRSA from hospitals by only cleaning half the wards.

"The bTB deaths are increasing. We are hearing about cats, pigs and even sheep getting infected, so understandably people are talking about the impact this will have on a badger cull."

According to Defra, the reason for the bTB statistics discrepancy is because the numbers only cover those animals where a culture or postmortem shows a positive result. Once bTB has been confirmed in herds of non-bovine species, subsequent animals that test positive to the skin or blood tests may not be examined, Defra said.

National Beef Association TB chairman Bill Harper, also stated the true number of bTB deaths was likely to be higher than Defra's figures suggested. He said: "I can see the camelid position contributing towards firmer TB control measures.

"It does seem to be very prevalent amid the species – they are very susceptible to contracting it because of the openness of their lungs.

"I appreciate there is a big worry with them, and increased cases involving pigs, sheep and cats, for example."

A Defra spokesman told the WMN it was working to update how the figures are reported to give a clearer picture of the number of non-cattle affected by bTB.

The spokesman added: "TB in animals costs Britain tens of millions of pounds a year, and the Government is committed to reducing its impact.

"We will be publishing a consultation on measures to tackle bovine TB later this year, and will publish plans for a full package of measures in the spring."