All warm-blooded animals can contract rabies, particularly mammals. A viral disease of the central nervous system, rabies is spread between animals, including humans, when saliva containing the virus enters an opening in the skin. This is typically achieved through the bite of a rabid animal, but transmission can also occur when infected saliva enters through mucous membranes or a break in the skin.
There are various factors that determine the potential of different species to transmit rabies. There are also unique considerations pertaining to bats as potential transmitters of the disease.
High-risk animals for rabies
Some animals are considered “reservoirs” for rabies and have a higher risk for transmitting the virus. Rabies reservoirs are animals in which the virus typically lives. Rabies infection in a species other than the reservoir species for a particular rabies variant (type) is considered “spillover.” Examples of spillover would be a raccoon infected with a fox variant of rabies virus, a skunk infected with a bat variant or a cat infected with a skunk variant.
In the United States and Puerto Rico in 2014, there were 6,033 confirmed cases of rabies in animals and one case in a human, according to the Centers for Disease Control and Prevention (CDC). Approximately 93 percent of the animal rabies cases were in wildlife.
September 28 is World Rabies Day (#WorldRabiesDay), intended to raise awareness of rabies and encourage people to vaccinate their pets. Learn more about it on the website of the Global Alliance for Rabies Control.
Podcast with Elsevier author
Pamela Wilson, who co-wrote this story, was interviewed about rabies on the Outbreak News This Week Radio Show in in Tampa, Florida. Listen to a recording of that interview here.
Some species are more prevalently rabid in certain geographical locations than in other areas. For instance, in Puerto Rico, the mongoose is the primary reservoir for rabies. In Canada during 2014, the leading species for rabies cases were bats, skunks and Arctic foxes. In the US that year, raccoons ruled as the most common rabid species, particularly on the east coast, followed by bats and skunks.
In Texas, bats and skunks are usually the primary reservoirs. Although Texas does not have the raccoon variant of rabies virus that is prevalent on the east coast, state law still defines raccoons as high-risk animals along with bats, skunks, foxes and coyotes.
Behaviors behind the faces
When many people visualize a rabid animal, they picture the foaming-at-the-mouth movie images of Cujo. However, the most typical signs of rabies are unexplained paralysis and a change in behavior. For instance, a normally playful puppy may become shy and withdrawn, a friendly cat may become very aggressive, and a nocturnal animal may be out during the day. There is a plethora of other clinical behaviors that a rabid animal may exhibit, such as not eating, eating strange (non-food) objects, pawing at the mouth, appearing to be choking, having difficulty swallowing, chewing at the site of the bite, having seizures and exhibiting hypersensitivities to touch or sound.
The following anecdotes are simple observations that were made while reviewing historical case investigation reports. They are not based on research, nor do they have supporting statistics; they are merely reflections of behavioral tendencies of different species that were laboratory-confirmed as having rabies. For instance:
- Foxes may become quite aggressive, such as repeatedly biting truck tires or jumping on hunters’ legs and biting them.
- Skunks may display more insidious behavior. There were multiple reports of rabid skunks attacking litters of puppies or kittens that were unfortunately housed outside; the skunks in these cases were sometimes found chewing on the heads of the young animals. As for their spray – no need to worry; the rabies virus is not transmitted through the spray.
- Bats might be downed and fluttering on the ground. Unfortunately, people are often tempted to pick them up and handle them with bare hands, leading to the need to get rabies post-exposure prophylaxis (PEP). In one case, two people were playing catch with a downed bat they found while waiting at a bus stop. A much wiser person reported the incident, which led to the bat that was abandoned by these individuals after they boarded the bus being tested for rabies. After the bat was laboratory-confirmed to be rabid, a media campaign had to be initiated to find the two persons who had ill-advisedly chosen to play a game with a sick animal. Then there was the teacher who passed a downed bat in a bucket around the classroom while encouraging all of the students to touch it. Subsequently, the bat tested positive for rabies, with the aftermath including interviews with all the students to determine if they had any contact with the bat that could be considered a potential exposure. Just touching a rabid animal does not constitute an exposure to rabies, but infected saliva contacting a break in the skin or a mucous membrane does. Additionally, bat bites are very small, leaving a mark about the size of a hypodermic needle, and can be easily overlooked.
- There was a person who believed in sharing a beer with a horse long before Willie Nelson sang about beer for his horses. When the person’s horse developed rabies, which could be transmitted by infected saliva from the rabid animal contacting the mucous membrane of the mouth, this person was singing a tune to a horse of a different color when faced with the need for PEP.
- Sometimes being in the wrong place at the wrong time can lead to a rabies exposure. A person crawling under a mobile home got nipped in the buttocks by a skunk that was later laboratory-confirmed to be rabid. Rabid skunks also have reportedly gained access to a house through a dog or cat door.
Low-risk animals for rabies
Low-risk animals for transmitting rabies include rabbits, opossums and armadillos, mice, rats, squirrels, nutria, shrews, prairie dogs, beavers, gophers and other rodents, according to Texas state law. If they are caged-raised animals, they are considered to be very low risk. These animals have a good potential of not surviving an attack by a rabid animal. However, that is not the case all of the time; last year, Texas had a rabid rabbit that reportedly was attacked in its outdoor hutch by a skunk about five weeks prior to its death.
Again, the human-behavior element can compound problems pertaining to exposure worries involving low-risk animals, especially cute animals who have learned to interact with people. It is not uncommon for some animals, such as squirrels and chipmunks, to appear tame and too friendly due to people feeding them. They become trusting of people and get positive reinforcement for doing so via the reward of food, so friendliness and tameness could be considered typical behavior for these animals. It’s best not to feed wildlife because it modifies their diet, which could be detrimental to their health; encourages them to trust people, which could also be detrimental to their health; and increases the chances for an unfortunate encounter, such as the person accidentally being bitten while hand-feeding the animal. Even though chipmunks and squirrels are considered to be low-risk animals for rabies, such an exposure then opens the door for speculation on possible rabies exposure, which would need to be discussed with a physician. Enjoy the wonderful, amazing world of wildlife, but resist trying to hand-feed these animals even though they may be irresistibly adorable.
Dogs, cats and domestic ferrets
Dogs, cats and domestic ferrets have a special grouping in the world of rabies.If they bite or otherwise expose someone to rabies, they can be observed for 10 days. If they are alive 10 days after the bite incident, they could not have transmitted rabies in their saliva at the time of the bite. That doesn’t mean that they couldn’t be incubating rabies; it just means that the disease wouldn’t have progressed to where the virus had traveled to the salivary glands. Due to their close contact and interactions with people, many states, including Texas, require by law that dogs and cats be vaccinated against rabies.
Vaccination is also highly recommended for domestic ferrets. Since domestic animals could be exposed to rabies by infected wild animals and then carry the virus into the home setting, vaccinating these domestic animals is one of the best ways to protect you, your family, and your pets against rabies.
Those “other” animals
Animals that are neither high risk nor low risk for transmitting rabies fall into a general “other” category. This includes animals ranging from livestock to monkeys, lions, tigers, and bears. There is a misconception that horses, cattle, and various other livestock cannot or do not typically get rabies. These animals should be vaccinated against rabies given their close association with people. In Texas, vaccination is highly recommend for wolf-dog hybrids and livestock. Among livestock species, vaccination of equines and others that have frequent contact with people is strongly advised.
The human face of rabies
Usually there is an average of two to three human cases of rabies per year in the United States. The case mentioned previously in 2014 was found to be due to a bat variant of rabies virus, although a specific exposure to a bat was not reported. This is a typical case scenario for human rabies in the US; a prevailing percentage of indigenous human rabies cases are due to bat variants of rabies virus. In over half of these cases, there was no known bite; in some of these cases, there wasn’t even any known contact with a bat. Most human rabies deaths in the US are due to exposure to rabid bats often because the bite wound is so small that the person may not know they were bitten and therefore does not seek medical attention and PEP.
It’s difficult to assess the annual number of human rabies deaths worldwide due to underreporting in developing countries, particularly Asian and African countries; however, it is estimated to be in the tens of thousands, possibly more than 55,000. These cases are primarily attributed to exposure to rabid dogs; the CDC states that exposure to rabid dogs is still the cause of over 90 percent of human exposures to rabies and 99 percent of human deaths worldwide. The availability of rabies biologicals for humans and animals has reduced this type of rabies transmission in other areas of the world. The price of biologicals and healthcare resources for humans and vaccination programs for animals can be cost-prohibitive for developing countries.
Is there a vaccine for humans?
As with certain domestic animals, rabies pre-exposure vaccinations are also available for humans. Pre-exposure vaccinations are given for several reasons. First, they may provide protection to people with unapparent exposures to rabies. Second, they may protect people whose post-exposure therapy is delayed. This is particularly important for people at risk of being exposed in countries where the rabies biologicals are difficult to obtain. Finally, although these vaccinations do not eliminate the need for additional vaccinations after a rabies exposure, they reduce the amount of treatment needed compared to PEP for a person who has not received the pre-exposure vaccinations.
The rabies pre-exposure vaccination regimen consists of three vaccinations given over a period of three to four weeks. Examples of people at higher risk for being exposed to rabies who should consider getting the pre-exposure vaccinations include rabies research lab workers, rabies biologics production workers, veterinarians and staff, veterinary students, animal control personnel, pest management professionals and wildlife workers. Travelers visiting foreign areas with enzootic rabies should also consider getting pre-exposure vaccinations.
Special attributes of bats
Bat bites are not always visible. Therefore, in situations in which a bat is physically present and there is a possibility of an unapparent exposure, the bat should be captured and submitted to a rabies laboratory for testing. If rabies cannot be ruled out by laboratory testing, people with a reasonable probability of an exposure may be recommended for PEP, and domestic animals may be recommended to either get booster vaccinations and confinement or euthanasia. Scenarios that may indicate a reasonable probability of exposure to rabies include:
- A child touches a live or dead bat.
- An adult touches a bat without seeing the part of the body that was touched.
- A bat flies into a person and touches bare skin.
- A person steps on a bat with bare feet.
- A person awakens to find a bat in the same room.
- A bat is found near an infant, toddler or a person who is sensory or mentally challenged.
- A person puts their hand in firewood, brush, a crevice or a dark space (e.g., a closet), then sees a bat close to that hand.
What to do if you find a bat
In general, if you find an injured, sick or dead bat, do not touch it. If you need assistance, contact your local animal control agency or local health department. Your local animal control agency should be able to send a trained officer to capture the bat.
If you are unable to reach anyone for assistance, recommendations for bat capture are as follows:
- Remove any children or pets from the room.
- Wear gloves preferably made of pliable, thick leather (never handle a bat with bare hands).
- Don’t let the bat touch bare skin.
- Confine the bat to one room by closing the windows and doors.
- Turn on the lights if the room is dark.
- Wait for the bat to land.
- Cover the bat with a coffee can or similar container.
- Slide a piece of cardboard under the can that has the bat trapped.
- Tape the cardboard directly to the can.
If any possible contact between the bat and a person or domestic animal has occurred, including the bat-specific exposure scenarios listed above:
- Do not release the bat.
- Contact your local animal control agency or law enforcement agency to arrange for immediate submission of the bat for rabies testing. If none of these entities are available, a veterinarian can assist with the specimen submission.
If you are certain no contact between the bat and a person or domestic animal has occurred:
- Take the container outside immediately.
- Release the bat, preferably at night and away from populated areas.
When capturing a bat, avoid striking it if at all possible. Physical trauma can damage the brain and make it impossible to conduct rabies laboratory tests.
Although there is a compassionate desire to release a bat, be sure all the scenarios under “Special attributes of bats” have been evaluated before doing so. By not eliminating all of these possible exposure situations before releasing a bat, a person might have to receive PEP unnecessarily; if the bat was available for testing and confirmed to be negative for rabies, PEP would not be needed. One of the authors had a family member who awoke to find a bat in a nearby magazine rack. When the police department arrived on the scene, they assisted by capturing the bat and releasing it into the night. When the scenario was relayed to the author the following day, the family member received the unfortunate recommendation that, since the bat was unavailable for testing, PEP should be initiated. The local health department agreed with this plan of action.
Even if a bat is dead, do not handle it with bare hands. Place it in a plastic bag without touching it; use a shovel or pick it up with a gloved hand. If it needs to be submitted for testing due to possible exposure and there will be a delay in submitting the animal to a rabies laboratory, keep the body cool in the refrigerator or ice cooler; do not freeze it. This will increase the chances of getting either a confirmatory positive or negative report from the laboratory. If you do happen to freeze it or don’t keep it cool and decomposition has started, still submit it to the laboratory for testing. The laboratorians are sometimes able to weave their magic and salvage enough of the specimen to effectively perform testing. In one historic case, a bat was found in a child’s bedroom. The parents buried the bat in the yard. When tragically the child died of rabies, health officials were able to exhume the bat, test it, and determine that the bat had rabies. However, it’s definitely best to not take chances on having a compromised specimen by keeping it in good condition for testing purposes.
Your rabies questions answered
In the authors’ previous story for Elsevier Connect, many readers wrote in with questions about rabies, most of which were answered by the authors. You can read the comments and responses here. However, the authors warn you to seek immediate medical attention if you think you may have been exposed to rabies.
Before excluding bat populations, check your state laws. For example, Texas has a state law that prohibits hunting, selling and purchasing bats. However, bats can be removed or hunted if the bat is inside or on a building occupied by people. Naturally, there are some exemptions to this law, such as an animal control officer, a peace officer, or a health official who captures a bat that the officer or official considers injured or diseased; a person who transports a bat for the purpose of laboratory testing if the bat has exposed or potentially exposed humans or domestic animals to rabies; or a person who is licensed to provide pest control services.
Texas is proud of its bat populations, including being host to the world’s largest bat colony at Bracken Cave near San Antonio and the world’s largest urban bat colony at the Ann W. Richards Congress Avenue Bridge in Austin. However, if bats in a building become problematic, they can be sealed out by using materials such as expanding foam, insulation and wire mesh to fill in any openings with a diameter larger than 3/8 inch. A one-way exit tube should be provided for 7 to 10 days after applying sealant. For larger areas, use not more than ¼-inch polypropylene mesh or hardware cloth. Apply sealing at night after the bats have exited for their nightly journey in search of food. Also, avoid sealing openings if there is a potential for there to be baby bats left behind while the adults went to feed. You can check with a professional bat excluder, bat conservation facility or a local parks and wildlife office for dates and times in your area to avoid when attempting to seal out bats. Some environments may also be conducive for bat houses to be erected as alternative roosts.
Keep in mind that bats fill a valuable ecologic niche, including insect control and seed dispersal, so make a concerted effort to deal with them in a humane and protective manner.
Rabies prevention tips
There are many things you can do to avoid being bitten and potentially exposed to rabies. For example:
- Avoid approaching strange animals.
- Do not handle downed bats.
- Report bites to the proper officials (for example, the local rabies control authority, animal control officer, game warden or local health department employee). For children, a teacher or parent is a good reporting resource. Provide a description of the animal, if possible.
- Do not feed wildlife.
- Do not handle sick, injured or dead animals.
- Vaccinate your pets and livestock against rabies, particularly those in close contact with humans.
- Teach children how to correctly behave around an animal to avoid being bitten (for example, in addition to the above tips, teach them to not pull the animal’s ears or tail, tease the animal, bother the animal while it’s sleeping or eating, run past the animal, move toward an unfamiliar animal, or try to play with the mother’s offspring).
If bitten, immediately wash the wound with soap and water, plus an iodine-based antiseptic, if available. Consult with a physician as soon as possible to determine whether PEP is warranted. The physician will also determine if antibiotics and/or a tetanus shot are necessary.
Source: New York State Department of Health, Management of Bat-Related Incidents in Homes
Student gone “batty” at university
By Prof. Rodney E. Rohde, PhD
In October 2015, I got an email from a concerned professor in the Texas State University Department of Biology: a student found a bat on campus and brought it inside the building in hopes of saving it. Only after the professor accepted the bat to deliver it to a wildlife faculty member for speciation and care did anyone think to be concerned about the rabies risk to the student (or others). Of course, the student was long gone at this time.
I was contacted due to my background in public health zoonosis and rabies diagnostics. Yes, it was a Friday around 4 p.m.
My first step was to inquire about the student. Was she a biology major? Was she even a student at our university? Had she been exposed to the bat via a bite, scratch or saliva? Unfortunately, no one had interviewed her.
I immediately contacted the university’s Risk Management team and the director of the Student Health Center. This started a chain of public announcements and emails to the entire university population and local press to try to find the student. While this was being done, I worked with my colleague Pam Wilson at the Texas Department of State Health Services (DSHS) and their rabies-proficient laboratory staff to get the bat submitted to the rabies laboratory as soon as possible; we also contacted the DSHS Regional Zoonosis Control office to tap into their wealth of contacts and resources for the area.
The DSHS rabies laboratory professionals and I advised the biology department on how to send the bat with a rush status for testing.
As often happens when someone finds a “downed/sick” bat, it turned out to be positive for rabies. And to make matters more interesting, it was a weekend when many students were not around.
Fortunately, the student was found. The health center director contacted me with information about her. She had handled the bat with bare hands. She didn’t believe she was bitten or scratched but was not completely sure. She was referred to a local emergency room for evaluation, and the physician there believed the case warranted enough risk to begin post-exposure rabies treatment. The student agreed to begin the treatment protocol, despite her understandable fear of the process.
At this point, our team – which had expanded to include the university police department, the VP of Student Affairs and local animal control officers – followed up with the appropriate areas of the university to review what had taken place and make recommendations for policy improvement. I created an educational case scenario for our state Texas Association for Clinical Laboratory Science conference, which I shared with the university and later presented at a conference of the American Society for Clinical Laboratory Science. The main point of the presentation is to educate others in the campus community and larger community in general about the benefits and risks of bats.
At our university, we get thousands of new students every year who are not familiar with our bat issues and locations of possible bat habitats on campus. We have started an ongoing bat and rabies education program, including prominent signage around campus. We plan to send mass emails from the Environmental Health Safety and Risk Management and the Student Health Center, as well as sending messages to mobile devices and posting on social media.
Fortunately, this case had a good outcome. This is not always the case with bat exposures because of the reasons mentioned in the article with respect to “missing” the exposure from not feeling a bite, or simply not understanding the risk associated with handling wildlife.
It’s important, and ironic, to remember that the student took the bat to a biologist – and that the response was not unusual.
For those who love animals or work with them, the immediate response is often to “save the bat.” But, the most important thing to remember is the risk to anyone who handles a bat – and the importance of saving the bat for laboratory rabies-confirmation testing. The situation underscores our critical need for public health education on bats and their rabies risks.
- Pamela J. Wilson, LVT, MEd, and Rodney E. Rohde, PhD: “8 things you may not know about rabies – but should” Elsevier Connect (September 2015)
- CDC rabies information
- Bat Conservation International
- Global Alliance for Rabies Control (GARC)
- GARC’s Bats and Rabies video
- New York State Department of Health: Management of Bat-Related Incidents in Homes
- Texas Department of State Health Services, Zoonosis Control Branch’s Rabies Prevention in Texas
- Epidemiology of rabies in bats in Texas (2001-2010)
- Bat Projects of British Columbia: Excluding Bats from a Building
Main photo of red fox ©istock.com/sduben