Several years ago, a researcher working with sparrows at a rabbit farm on Maui fell ill. He was feverish and tired, then started getting sores on his skin. Doctors weren’t sure what it was and although he was never officially diagnosed, he responded to treatment for tularemia, a disease caused by bacteria carried by rabbits, rodents, and other animals.
Officially, tularemia has never been documented in Hawaiʻi. It’s difficult to culture the bacterium and handling it poses a significant infection risk to lab workers. “If not here, there is a real threat that tularemia could, at any time, be introduced into Hawaiʻi. It affects so many animal species, and once here, mosquitoes and other blood-sucking arthropods could spread it,“ says Fern Duvall, head of Maui’s Native Ecosystem Protection and Management program with the Department of Land and Natural Resources.
On the mainland, where tularemia is widely present, the disease is rare among people. They are exposed to the disease if they handle infected animals, or if bitten by ticks or another insect that fed on an infected animal. When bacteria come in contact with the skin, they cause ulcers that spread through the body, eventually reaching the lungs. If the bacteria is inhaled, the results can be deadly.
Occasionally, there are serious localized outbreaks of the disease. The summers of 2000-2001 saw nineteen cases of tularemia on Marthaʻs Vineyard, Massachusetts– one proved fatal. The Centers for Disease Control (CDC) came to investigate. An unusually high number (14 out of 19) were pneumonic (the bacteria had entered the lungs) and many involved landscapers. What the CDC suspected was that lawnmowers or other cutting tools struck the carcasses of dead, infected rabbits, the bacteria went airborne.
In 2015, there were outbreaks in Colorado, Wyoming, South Dakota, and Nebraska. The CDC theorized these outbreaks may have been triggered by increases in rabbit populations, which grew in response to more vegetation, caused by higher than normal rainfall.
Vegetation, rainfall, and landscapers are plentiful in Hawaiʻi – what we don’t have are populations of rabbits running wild–at least not yet.
According to state law, people can keep rabbits but they must be contained. If kept outside, rabbits must be in a cage off the ground. The penalties for noncompliance may reflect the seriousness of the threat: loss of your pet, fines, or even jail time.
Duvall says the natural predators of rabbits in Hawaiʻi–cats, rats, or mongoose–are unlikely to keep populations of wild rabbits in check. Rabbits evolved with a multitude of predators: weasels, coyote, bobcats, owls, hawks, snakes, foxes, and raccoons. To survive high mortality rates, they breed like, well, rabbits. The female (doe) can become pregnant with her first litter at 3 months of age, and again just a month later, within days of giving birth. One pair of rabbits can produce 100 kits (baby rabbits) per season, and up to 1,000 in a lifetime.
“We know they can become invasive,” explains Duvall. In 1989, six illegally released rabbits quickly became 100 at Hosmerʻs Grove in Haleakalā National Park. On Laysan, a small island in the Northwestern Hawaiian Islands, free-roaming rabbits ate the island bare in the early 1900s, likely causing the extinction of three bird species– Laysan miller bird, Laysan ʻapapane, and Laysan rail.
Beyond environmental impacts, rabbits running wild increase the risk of tularemia. “Rabbits are more often in contact with people,” explains Duvall. Whether as pets kept outdoors or released to the wild, more rabbits mean more rabbit-human interactions. Other pets can be affected: dogs, cats, and livestock can get tularemia from ticks or direct contact with an infected animal. Early treatment with antibiotics is critical.
You can help protect Hawaiʻi. If you have a pet rabbit, spay or neuter it. If you raise rabbits, keep them contained. If you see a rabbit running wild, report it. Call the Maui Invasive Species Committee at 573-6472 or report online through 643pest.org.
Lissa Strohecker is the public relations and education specialist for the Maui Invasive Species Committee. She holds a biological sciences degree from Montana State University. Kia’i Moku, “Guarding the Island,” is prepared by the Maui Invasive Species Committee to provide information on protecting the island from invasive plants and animals that can threaten the island’s environment, economy, and quality of life.
This article was originally published in the Maui News June 11th, 2017, as part of the Kia‘i Moku Column from the Maui Invasive Species Committee.
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