The loss of three-year-old Hari Hi Way and two-year-old Bala Hi Way takes the toll of fatalities among young elephants at Chester Zoo to five in six years.
Animal rights campaigners said the figure was “alarming” and called for an end to the breeding of elephants in captivity.
For a number of years campaigners have pointed out that Elephant Endotheliotropic Herpesvirus (EEHV) – identified in all the victims – is more common in elephants held in confined spaces.
But UK zoo experts have pointed out that EEHV hits the animals both in the wild and in confinement, while the causes are unknown.Keepers at Chester Zoo, which prides itself on its Asian Elephant Conservation Programme, are said to be devastated by the latest deaths.
The death of Hari Hi Way, a bull Asian elephant, came just six weeks after that of female Bala Hi Way.
The zoo was still mourning the deaths of two-year-olds Raman and Jamilah and three-year-old Nayan Hi Way.
Chris Draper, of the Born Free Foundation, said: “This virus that kills elephants is predominant in the captive herd. It has a long history of causing mortality. If you keep breeding elephants, you run a high risk of them dying between the ages of two and five.
“It is a moot point whether the virus is found in the wild. But even if that’s the case, it seems to have a far greater impact in captivity.”
A Chester Zoo spokesman said: “The exact cause of Hari’s death will be determined by a post-mortem examination. However, as with Bala, we can confirm he tested positive for EEHV, a fast-moving virus which affects both wild and captive elephants between the ages of two and five.
“There is currently no vaccine against EEHV, although research is ongoing.
“Chester Zoo’s veterinary staff carry out daily blood testing of the elephant herd and, as soon as the first traces of EEHV were detected in both Bala and then Hari, the teams began early treatment using anti-viral medication. Sadly, despite the early intervention and rapid response of the teams, the treatments were unsuccessful.”