IThis has happened to me dozens of times: I’m riding a wave and out of the corner of my eye I see something dark rising up from below. Cape Town is a great white shark hotspot, so it’s hard not to assume the worst. But my fears are quickly allayed when it becomes clear I’m sharing the wave with a Cape fur seal. Sometimes the seal gets so close I can see the foam on its baleen.
Now nine seals have tested positive for rabies — the first large-scale outbreak of the disease in a marine mammal anywhere in the world — and people like me are monitoring the waters along this 400-mile (600-kilometer) coastline for another reason.
“I was surfing the other day and this seal showed up in the lineup. [of surfers] “The sun itself is what’s wanted,” said Greg Oelofs, coastal management manager for Cape Town Council. “Usually surfers would be there enjoying the company, but now everyone’s paddling at full speed trying to get away.”
last month, Within minutes, one seal had bitten several surfers. Another seal swam ashore with horrific facial wounds that could only have been inflicted by an extremely aggressive animal. Following these attacks, authorities decided to euthanize the four and send their bodies for rabies testing.
Three of the four tested positive, and the number of infected people has since risen to nine.
Scientists at the University of Pretoria are sequencing the virus to determine when and where rabies entered the seal population, which is endemic in much of the southern wildlife. Africa (For example, the jackal) However, most of these animals do not live close to humans.
The seals’ behavior began to change several years ago: Oelofs and his team noticed a significant increase in seal aggression in Cape Town in late 2021, following intermittent reports of seals attacking humans.
To understand this highly unusual behavior, they Marine scientists at local research institute SeaSearchworking with animal welfare organisation the SPCA to capture and test the animals.
The researchers considered the possibility that rabies might be the cause, but the only recorded case of rabies in a seal, in 1980 on the Norwegian archipelago of Svalbard, suggested this was highly unlikely.
Oelofse stresses that the rise in cases is not a sign of a rapid spread of the disease. “We are retrospectively testing animals that have been euthanized,” he says. “We’ve been very fortunate that SeaSearch has been able to collect and store 120 brains over the past two and a half years.”
By examining these brains, we can get a better idea of when rabies first appeared in the population and how widespread it may have been. We will continue to test animals suspected of having rabies.
On Cape Town’s beaches, the message is clear to swimmers and surfers like me: Anyone who has been bitten by a seal, no matter how long ago, should seek immediate medical attention. The incubation period for rabies can last from one week to two years.It usually takes a few months.
But the reported evidence Oelofse has seen is reassuring. “I think there are a fair number of people who have been bitten by rabid seals, but thankfully no humans have been infected yet,” he says. “We don’t know why. Maybe the infection rate is low. Maybe salt water in the mouth reduces the viral load?”
An estimated 2 million Cape fur seals live in colonies stretching from southern Angola to Algoa Bay on the east coast of South Africa. Dr. Greg Hoffmeyer“Seals spend days or weeks at sea, migrating long distances and only coming ashore occasionally on islands to rest and mate,” said marine biologist David Schneider of the University of California, San Diego, who has studied seals for 32 years.
But in offshore colonies, the seals live in close proximity to each other and fights are frequent, and rabies can spread quickly among seals because it is mainly transmitted through saliva.
Meanwhile, lifeguards and shark spotters have been instructed to close beaches if aggressive seals are sighted, and the public is urged to report any unusual seal behaviour, keep dogs on a lead at all times, and stay away from harbour seals which have become habituated to humans.
It’s understandable that you might panic and want to rush away from the seal, but it’s not entirely justified, Oelofse says. “If the seal starts acting strangely or aggressive, move well away and call authorities,” he says. “A relaxed seal is unlikely to pose a threat.”
The message seems to be getting through: yesterday while we were surfing a seal came up to us on a backline and rolled around on the surface like an oversized Labrador. No one around panicked and after a while the seal swam away from us.
Oelofse stressed that authorities are taking a proactive approach because “there are no global ‘best practices’ to follow.”
“We really want to know the transfer rate. [of the disease]”Rabies could become endemic among seals or be transmitted to other coastal mammals such as the Cape clawless otter,” he said, expressing concern that rabies could become endemic among seals or be transmitted to other coastal mammals such as the Cape clawless otter.
“We’re also very concerned about how it will affect the seals,” he says, “and we really don’t want people to get rabies.”
