The New York Times, July 30, 2015
We humans can drive species toward extinction by hunting them or destroying their habitat. But we can also threaten them in a more subtle but no less dangerous way: by making them sick.
In the early 1900s, humans introduced malaria-spreading mosquitoes to Hawaii, and many native bird species were decimated. More recently, a fungus introduced to the United States from Europe has proved lethal to several species of bats.
Now, scientists and wildlife managers are struggling to prevent the next infectious disaster.
A recently discovered fungus is killing salamanders in Europe. It is likely spread by the pet trade and could soon arrive in North America, home to about half of all salamander species.
For months, biologists have been calling for a halt to the trade in pet salamanders so they can mount a defense against the fungus. But federal officials have yet to take action.
“You would think there would be something in place,” said Vance T. Vredenburg, a biologist at San Francisco State University. “We really need a government agency at some level to take action and do something.”
Dr. Vredenburg and his colleagues have already seen what a fungal infection can do to amphibians. In the 1990s, they discovered that Batrachochytrium dendrobatidis (Bd for short) was wiping out entire populations of frogs. Humans have spread Bd around the world, and now it threatens hundreds of species with extinction.
“People really didn’t believe that something could happen that was so bad,” Dr. Vredenburg said. “I really don’t want to see that happen again.”
In 2013, unfortunately, scientists in the Netherlands discovered that a related species of fungus, called Batrachochytrium salamandrivorans, or Bsal, was killing fire salamanders. Since then, they have also found it in Belgium and Britain.
Having seen what Bd could do, researchers scrambled to understand Bsal better. Three species of Asian salamanders that are popular as pets can carry the fungus without getting sick, they found. It is likely that the pet trade is spreading Bsal to wild salamanders in Europe, which have not developed resistance to the disease.
Researchers in North America have been looking for Bsal, and so far have not found any trace of it. But based on a study of North American salamanders, published Thursday in the journal Science, Dr. Vredenburg and his colleagues predict that some regions of the continent are at high risk of an outbreak.
“It shows a terrible picture,” Dr. Vredenburg said.
The pet trade brings huge numbers of salamanders into the United States. Fish and Wildlife Service records show that about 780,000 salamanders were imported from 2010 to 2014. Dr. Vredenburg and his colleagues found that 98 percent of the imported animals were native to Asia.
In Asia, Bsal-carrying salamanders tend to live in cool, moist climates. Dr. Vredenburg and his colleagues identified several regions in North America with the same conditions where the fungus should grow well. Some of these regions are home to a high diversity of salamanders.
The scientists identified three regions as particularly hospitable to Bsal: the Southeast, the Pacific Northwest and Sierra Nevadas, and the highlands of central Mexico.
Dr. Vredenburg sees an additional threat to salamanders in these areas: Some regional cities, such as San Francisco and Atlanta, are arrival points for imported salamanders.
Because Bsal was discovered only two years ago, scientists still have a lot to learn about it. The fungus may grow in a wider range of conditions than currently known, for example. Discovering new host species in Asia could help scientists better predict where else Bsal could thrive in North America.
Karen R. Lips, a biologist at the University of Maryland, agrees with Dr. Vredenburg that the United States should ban imported pet salamanders, at least until scientists can figure out the scale of the Bsal threat and come up with a plan for blocking it.
It might become possible, for example, to test imported salamanders for Bsal and disinfect animals carrying the fungus. “The longer we can keep things out, the better chance we’ll have of putting a plan in place,” Dr. Lips said.
The Pet Industry Joint Advisory Council supports a temporary halt in salamander imports. “A moratorium on importation of Bsal-susceptible salamanders should be put into place until such time as effective testing and treatment regimens have been developed,” Robert Likins, the council’s director of governmental affairs, wrote in an email.
The Fish and Wildlife Service can stop the import of “injurious wildlife” under a law known as the Lacey Act. This spring, the service announced that it would evaluate pet salamanders for their risk of introducing Bsal. That process is inching along.
“The act does not include a provision to list injurious species on an emergency basis,” said Laury Marshall Parramore, a spokeswoman for the service.
Priya Nanjappa of the Association of Fish and Wildlife Agencies said that the Bsal experience showed how badly we need new laws allowing the government to respond effectively to emerging wildlife diseases.
“It’s demonstrating that even when we have the foresight, we’re still stumbling,” she said.
Copyright 2015 The New York Times Company. Reprinted with permission.