Daycare centres for dogs are stepping up precautions against a potentially deadly bacterial infection that can affect both animals and humans.

It comes after the Agri-Food and Veterinary Authority (AVA) announced yesterday that there have been 18 suspected cases of leptospirosis reported since the start of this year, after just two cases last year and none in 2014.

Twelve cases reported between June 27 and July 14 were associated with the Sunny Heights centre in Bukit Timah.

It has since been issued an isolation order, prohibiting any dogs from entering or leaving the premises during the investigation without AVA's authorisation.

Of the 18 suspected cases, seven dogs have died, including five from Sunny Heights. The disease is primarily spread by rodents.

According to the Ministry of Health, 14 human cases have been reported so far this year, including one involving a family dog which had stayed at Sunny Heights.

About 20 to 30 human cases of leptospirosis a year were reported between 2012 and last year.

Only one of the 18 suspected cases involving dogs has tested positive for the disease so far, though a negative laboratory test result may not indicate that an animal is not infected, the AVA said.

An inspection of Sunny Heights and its vicinity did not detect any signs of rat activity and environmental samples have been taken for testing. Samples of blood from the 16 to 18 dogs quarantined in the centre have also been drawn for testing.

Dogs that died had symptoms of disease, say owners

Sunny Heights owner Derrick Tan was informed of the first case at the end of June, and stopped receiving dogs at the centre on July 4 as a precautionary measure after informing clients of the suspected case. Its pool was also drained and the centre disinfected, said Mr Tan, who is also the founder of welfare group Voices for Animals.

Three dog owners whose pets frequented the daycare centre said their dogs had died between June and July of symptoms similar to leptospirosis, though only one case was confirmed through a blood test.

Lawyer Stefanie Yuen Thio's eight-year-old golden retriever Joe was diagnosed with leptospirosis on July 1, and died the day after.

"My dogs are fully vaccinated, including for lepto, so we didn't imagine that this would be the issue," said Ms Yuen Thio, 46. "I called the daycare centre and they said they would tell the other owners immediately. They were concerned, solicitous and responsible."

Project manager Robert Baan, who has been taking his three dogs to Sunny Heights for years, said that his two west highland terriers each died within three days in June and July. Both had symptoms of leptospirosis, including vomiting and liver and kidney issues, though a test for one of the dogs came back negative for the disease.

"To me, the blood results don't say anything because there are so many strains but the symptoms are clear," said the 48-year-old.

Ms Valerie Heng, 50, said her border collie was treated by a vet for leptospirosis and died on July 14.

"Whatever is done now cannot bring him back. But if there is negligence on the part of Sunny, they should be upfront and claim responsibility", she said.

Other daycare centres have stepped up measures to prevent the spread of the disease.

The Wagington's managing director, Ms Estelle Tayler, said: "We have always asked for vaccination status when dogs come for boarding and daycare, but now we are checking for swimming as well."

Mr Hurb Leung, 35, owner of Up For Paws, a daycare and boarding centre in Bukit Timah, said a newsletter was sent to clients last week urging them to exercise caution when taking dogs out after he read social media posts about the rise in cases. Some have said that they will not take their dogs to the centre temporarily out of caution.

Mr Leung added: "I hope this doesn't get out of hand."

In 2012, a foreign worker's death here was linked to leptospirosis.