The Trouble with Bats

Since moving to Michigan I have had the good fortune of not once, but twice having a run in with a bat in my home. Bats are responsible for the most rabies deaths in the US: 7 out of 10 rabies deaths are attributable to bats, with other transmission routes from raccoons, foxes, and skunks.

Some deaths have occurred after no obvious bites from a bat – just after a bat was found in one’s home after being asleep. 

Rabid bats may be on the rise in Michigan – with twice as many rabid bats found in 2018 as in 2017. However, it’s important to note that animals are only tested when reported, so the increased findings of infected animals may not actually mean a greater rabies prevalence, but instead more diligent people submitting suspect animals.

Why is Rabies a Big Deal?

Rabies is a nearly ubiquitous disease, and is present on all continents except Antarctica, though over 95% of human deaths occur in Asia and Africa. Every year, more than 15 million people worldwide receive post-exposure vaccinations, which is estimated to prevent hundreds of thousands of rabies deaths annually.

The incubation period for rabies is typically 2–3 months but may vary from 1 week to 1 year. This means from the time of being bitten – one could wait months to see symptoms emerge, though death occurs very rapidly once symptoms present. Early symptoms of rabies are generic: fever, headache, weakness, but these symptoms quickly become more dangerous. There are two types of rabies:

• Furious rabies (the classic example) causes hyperactivity, excitable behaviour, hydrophobia (fear of water) and  aerophobia (fear of fresh air). Death occurs after a few days.
• Paralytic rabies accounts for about 20% of human cases. This form of rabies is less dramatic and slower, with muscles gradually becoming paralyzed, eventually resulting in a coma and death. This form of rabies is often misdiagnosed, contributing to under-reporting.

Once  symptoms occur, the disease is nearly always fatal. Once a rabies infection is established, there is no effective treatment.

Rare Survivors and the Milwaukee Protocol

Jeanna Giese is the first known survivor of rabies without any vaccination (and the only such survivor in the US). She did not receive rabies vaccinations because her parents did not know that contact with a bat could lead to rabies exposure. After being bitten by a sick bat at age 15, her parents cleaned her wounds and proceeded as usual. Three weeks later, she went to the hospital with severe neurological symptoms but had missed the window for vaccination, which must be given within 6 days of rabies exposure.

The doctors tried a never-before-attempted treatment, inducing a coma to give her immune system time to build up antibodies to the virus. This treatment is now known as the Milwaukee protocol. Because rabies kills by compromising the brain’s ability to regulate necessary functions: breathing, salivation and heartbeat, the doctors believed she might survive if they suppressed her brain function until her immune system had mounted a response to the virus.

Miraculously, she survived the treatment, though she retains lingering signs of her rabies disease, reduced physical strength and speech impediments.

Though the protocol has been used over 40 times now, she is the only one to have survived. The protocol is controversial, and why she lived, and the others died, is unknown. Though UptoDate reports 25 survivors of rabies, Giese is the only one who received no pre- or post-exposure vaccination.

My Experience with Bats and Student Housing

In the first home I lived in, my roommates and I were startled to see a bat hanging on our front door curtain rod in the middle of the day (see below). Bats are nocturnal creatures, so a bat sighting during daylight hours might mean  the bat is sick. From my schooling in infectious diseases, my mind jumped to rabies. Nonetheless, I did not know exactly what to do upon finding a bat in my home.

Given the fact that bats seem to be so common in Michigan, and especially in student housing where the house is old and landlords have little incentive to patch up holes and seal off roofs and attics, here is some information about what to do if you find a bat in your home. For UM students, Michigan University Health Services also has this website with information on how to catch and report a bat in your home.

Batter Up: What to Do if You Find A Bat

The Mayo Clinic says that because rabies is so fatal and vaccination is so effective, “even if you aren’t sure whether you’ve been bitten, seek medical attention. For instance, a bat that flies into your room while you’re sleeping may bite you without waking you. If you awaken to find a bat in your room, assume you’ve been bitten. Also, if you find a bat near a person who can’t report a bite, such as a small child or a person with a disability, assume that person has been bitten“.

The only way to avoid vaccination after such an exposure is if you can can catch the bat and have it sent to the health department for testing. This testing is provided seven days a week. The results take about 24 to 48 hours, and only if an animal tests positive for rabies would vaccinations be needed.

The CDC provides these instructions on how to trap a bat, though it may not always be easy or safe to do so. Use your best judgment:

Rabies Post Exposure Prophylaxis (PEP)

If you have never been vaccinated against rabies before:

You will receive a dose of human rabies immune globulin (HRIG) and rabies vaccine given on the day of the rabies exposure (with the amount of HRIG dosed according to your weight).

You will return three more times, on days 3, 7, and 14 for a dose of the rabies vaccine at each visit. The combination of HRIG and vaccine is recommended for both bite and non-bite exposures, regardless of the interval between exposure and initiation of treatment.

If you have been vaccinated against rabies before:

Schedule 1: Two vaccines are required: one dose of the vaccine on day 0 and one dose on day 3 .

Schedule 2: A “4-site” intradermal (ID) PEP . This consists of 4 injections of 0.1 mL equally distributed over left and right deltoids and thighs during a single visit.

The decision to use schedule 1 or 2 is left with the health care provider in consultation with the patient.

The Take-Away

All told, the rabies vaccination is not fun, but represents a major improvement from just decades ago when the vaccines were given through large gauge needles into the stomach.

Given the poor treatment options (1 in 40 survival with the Milwaukee protocol), there really is no other choice but to get vaccinated. The best wisdom I can impart is that if you are equipped to do so, trap that bat and get it tested! This will help aid reporting and prevalence of rabies as well as maybe saving four trips to the emergency room.