Rabid bat cases coincide with beginning of fall migration
- Elizabeth Larson
- Posted On
In the video above, bats catch insects drawn to the lights at Lucerne Harbor Park in Lucerne, Calif., on Wednesday, September 13, 2017. Video by Elizabeth Larson/Lake County News.
LAKE COUNTY, Calif. – Lake County’s public health officer confirmed that another bat has tested positive for rabies, requiring treatment for the individual who came in contact with it, a situation that coincides with the annual seasonal southern migration of the region’s bat population.
Dr. Karen Tait said the bat was found in Kelseyville on Tuesday, and that the individual who came in contact with it was a juvenile.
Dave McQueen, superintendent of the Kelseyville Unified School District, told Lake County News that the juvenile is a freshman at Kelseyville High School.
The Tuesday case is the second reported over the past two weeks by county health officials.
A bat found in Lucerne tested positive for rabies, resulting in several people who had come in contact with the dying animal requiring treatment, as Lake County News has reported.
“We don’t always test bats. We test them if there’s human exposure and if the condition of the bat is fresh enough that it will be a good specimen,” said Tait, adding, “If we tested more we might find more.”
Tait said the Kelseyville Unified School District contacted Public Health about the bat.
She said Lake County Animal Care and Control Director Bill Davidson has been working closely with her staff to assist with collecting and transporting rabies specimens to the Sonoma County Public Health Laboratory for testing.
In this latest case, the bat was collected, went straight to the lab and they had results by the end of the day, Tait said.
Getting the specimens to the lab as soon as possible is critical, as Tait said it can help rule out rabies. If testing can’t be used, it obligates anyone who came in contact with suspect animals to go through treatment.
Tait said in both of the recent cases involving rabies-positive bats, the animals were acting sick.
In the Kelseyville case, the teen handled the bat, which was enough for Tait’s office to recommend treatment for rabies as it’s important to err on the side of caution.
“You don’t want to be wrong on this,” she said, explaining that rabies is almost 100-percent fatal, yet it’s also 100-percent preventable.
If Public Health knows a person has been exposed to rabies, Tait said the agency will track them through recommending treatment and checking with them to make sure they completed it.
“We get a lot of bite reports of animals that most likely were not rabies” but aren’t available for quarantine or testing, she said. “The majority of animals are not rabid, especially domestic animals.”
Tait added, “My concern is around the animals that are allowed to run free and allowed to interface with wildlife.”
She also emphasized the importance of vaccinating dogs and cats, including feral cats.
“The danger there is if the cat or dog becomes rabid, then they can expose people,” she said. “There is an underappreciation of that risk.”
“Any animal that licks itself to groom itself, if they’re rabid, the rabies virus is in the saliva,” she said.
So if a person handles such an animal and has a break in their skin, they could be exposed to rabies without even having been bitten, Tait explained.
Bats can also leave inapparent bites and scratches, which is why people who find bats flying around in their bedroom may have been inadvertently exposed while they were sleeping, she said.
Tait said that any mammal can get rabies, but the risk is lower with some than with others. That’s the case with opossums, which have cooler body temperatures that have resulted in them rarely getting the disease.
Rabies has no set incubation period, and the onset can range from days to months. Tait said that, usually after 10 days of observation, a domestic animal can be ruled not rabid.
More information about rabies can be found at https://www.cdc.gov/rabies/index.html.
A numbers game
The California Department of Public Health, or CDPH, reported that rabies is found in all 58 of the state’s counties.
In an October report, CDPH said bats have been the most frequently reported rabid animal in California from 2000 to 2015.
“As in previous years, most rabid bats were detected in the late summer and early autumn – a time when juvenile bats are leaving the roosts for the first time and adult bats are initiating pre-winter migration or search for winter roosts and hibernacula,” the report stated.
Tait said that bat rabies is in the environment and it’s important for the public to be aware.
“It’s just a little unusual that we’ve had two positive tests within a fairly short period of time,” she said.
However, Rachael Long, a Woodland-based University of California Agriculture and Natural Resources advisor who studies bats, explained that the recent rabies cases overlap with the beginning of the bat migration season referenced in the state report.
Long gave a presentation in Lake County in April to the Redbud Audubon Society about bats.
“We do have 26 species of bat in California, which is phenomenal,” she told Lake County News this week.
The most common bats in this part of California are the Mexican free-tailed bats, which have large colonies ranging into the hundreds of thousands at the Vic Fazio Wildlife Refuge between Davis and Sacramento; and the less-imaginatively named little brown bats and big brown bats, Long said.
While some bat species do hibernate in caves, those three species don’t, she said.
It’s the hibernating bat species that are hit by white nose syndrome, which hasn’t made it to this area yet, said Long.
The syndrome, which needs cool, humid conditions and thrives at 45 degrees, attacks them while they’re hibernating. Long said it grows on their wings and muzzles, and causes them to burn too much fat tissue so they can’t survive through the wintertime.
While white nose syndrome isn’t here yet, Long added, “We are going to get it because it’s really spreading like wildfire everywhere.”
Bats are primarily migratory, like swallows. “They depend on insects for their food source,” Long said, and as a lot of them don’t hibernate, they have to feed all year long.
She said they migrate north in the spring – through this area and the coast around April – when it warms up and there are a lot of insects.
They always go back to where they were born. “They have these incredible homing instincts, just like the salmon,” she said.
They have one pup per year, and it usually takes six to eight weeks to raise the pups and for them to learn to fly, Long explained.
Around the start of September, bats start to head south for the winter, and Long said they can migrate in the thousands from as far north as Canada to Southern California, Mexico and Central America.
Like birds, “They congregate and then they really start to move,” she said.
Due to those sheer numbers, Long said it’s during the migratory months that there are more bat-human encounters.
As they’re traveling, “They have to rest along the way,” said Long, and they sometimes rest in places where they truly don’t belong or where they’re noticed.
“The reason that we’re picking up more bats now, it’s just their migration,” she said.
Whereas mothers and young tend to stay together, juvenile male bats are more independent, and as a result they tend to have the hardest time during the migration. They’re often alone and don’t know where they are, Long said.
The level of rabies in bats “is really a numbers game,” said Long; more bats with rabies are being seen because more bats are migrating.
Rabies is endemic in bats, with usually about one in 1,000 infected, Long said. Thus, if you have 20,000 bats migrating through an area, 20 of them might have rabies, so it’s not really a rabies outbreak but an issue of increased population.
She encourages people who see bats in an area where they’re unlikely to be in contact with humans to simply leave them alone. At this time of year, especially, they’re flying thousands of miles and are tired, and so they may be resting during a break in their travels.
Long said people often think they have to call their local animal control agency when they see a bat that may be perfectly healthy. “That drives me crazy.”
Bats that have rabies are easy to distinguish, said Long, as they usually are so sick they’re paralyzed. If you come across such an animal, it should be tested.
That’s why it’s important to leave wildlife alone and especially to not handle bats with bare hands, Long said.
Like Tait, she encourages people to vaccinate their pets to protect them from rabies.
While Long and Tait urge precautions around bats, they also reminds people of how good and beneficial they are, despite the bad perception many people have about them.
“They’re such an important part of the ecosystem,” said Tait.
A 2011 study in the journal Science estimated that bats provide more than $23 billion per year in pest control to farmers.
Long said they’re agile and have wings built for incredibly fast flight and aerial maneuvers, with striated muscles that allow them to expand and contract their wings, which are the focus of special study.
“They’re just so amazing,” she said.
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