Jamshedpur: All the four tigers at Tata Steel Zoological Park are in the grip of a deadly tick-borne infection that killed a cub and an adolescent last week and is threatening to exterminate the entire big cat population at the country's only private zoo in the absence of drastic countermeasures.

Babesiosis, which claimed three-year-old Royal Bengal Tiger Ahana on Sunday and an unnamed seven-month-old on March 18, is a malaria-like disease caused by parasitic protozoa babesia that destroys red blood corpuscles to thrive.

After the twin deaths, the zoo authorities had fumigated the 37-hectare animal kingdom and administered prophylactic injections to the other big cats, but the infection seems far from contained.

While resident tiger couple Dona (Royal Bengal) and Kailash (white pigmented), and their two seven-month-old cubs are already infected, the vector-borne disease may not spare the five pure-bred African lions and four leopards, fear officials.

Tata zoo director Bipul Chakravarty said the situation was "dicey" and they were "keeping their fingers crossed". He said a team from Jusco's vector control wing had visited the zoo on Tuesday. "Fumigation and bleaching must continue, it said. But, no one can tell what will happen to the tigers," he said, adding that saving the lions and leopards could be a big challenge too.

Zoo vet Manik Palit echoed Chakravarty. "We are closely monitoring the health of the tigers, but it is difficult to say if they will survive," Palit said, stressing that the animals were currently off feed. "The cubs are not touching food at all."

This is not the first time Babesiosis has targeted the endangered Royal Bengal Tigers.

In 2006, four tigers had died within a span of 10 days at Bhagwan Birsa Biological Park in Ormanjhi, Ranchi, prompting the authorities to shift the remaining feline species to a rescue centre at Visakhapatnam.

Two years ago, nine lions succumbed to Babesiosis at the Etawah Safari Park in Uttar Pradesh, Chakravarty recalled.

On whether Tata zoo planned to quarantine the infected tigers or relocate the other big cats, the director said they had apprised the chief wildlife warden of the situation and sought his advice.