Bats are popularly associated with creepiness. Whether on Halloween cards or in haunted houses, they symbolize all that is dark and Gothic. It can’t just be because they are nocturnal fliers, since we don’t feel the same way about owls. Whatever spurs these fears may be irrational, but there are real reasons to worry about bats.
As we’ve explained before, it’s not really bats’ fault they spread disease.
But they do, and the diseases they pass on are the stuff of nightmares.
In the middle of the largest outbreak of all time, you probably don’t need to be reminded of Ebola. You may also be familiar with its awful symptoms. It starts with a high fever and other non-specific indications such as fatigue and muscle and joint pain. However, these usually turn to vomiting, diarrhea and abdominal pain. Blood is less likely to clot and both internal and external bleeding can be common, including into the whites of the eyes.
Hopefully, you’re also aware that Ebola is not airborne. Nor is it transmissible before people know they are sick, unlike many cold viruses. To catch it, you need direct contact with the blood or bodily fluids of someone who is already showing symptoms.
We don’t know whether the first human infected in an epidemic normally catches the disease directly from a bat, or via other susceptible species such as chimpanzees or duikers. However, we are becoming confident that bats represent the reservoir in which the Ebola virus survives between outbreaks.
That doesn’t mean you need to fear the flying foxes or microbat hanging in a nearby tree, however. Only bats living in tropical Africa have been found to carry Ebola.
Centers for Diseas Control
Marburg virus Marburg marburgvirus (also known as Lake Victoria virus) is a bit like Ebola, but has more of a record of spreading in developed countries. It is named after one of the German towns where the first recorded cases occurred. The direct source of infection were grivets, a type of monkey from the area around the Nile, but the grivets probably caught it from bats.
In 2009, the virus was isolated in Egyptian fruit bats known as rousettes (Rousettus aegyptiacus) who didn’t even have the decency to get sick themselves.The bats were the likely source of and outbreak among Ugandan miners working nearby.
Marburg has a fatality rate that can reach 90%, compared to 50-70% for the current round of Ebola. The fever, vomitting, headaches and diarrhea are similar, leading to death from multiple organ dysfunction, which is every bit as as bad as it sounds. Oh yes, and those with the disease also can become aggressive.
Say “rabies carrier” and people probably think of suddenly savage dogs. Any warm blooded animal can fall prey to this particular disease, which leads to inflammation of the brain, but bats are the main threat to those living in the Americas and Europe, as it has proven that it’s a lot harder to vaccinate a wild population that can fly.
The perception that dogs are to blame isn’t untrue, most cases worldwide are from dog bites. Since more people die from rabies in an average year than have been killed by Ebola up to the time of writing this, it’s a pretty big deal.
Having the virus slowly spread through your peripheral nerves until it reaches the brain and spinal cord, usually after 1 to 3 months of terror, is no picnic either. Having so much pain when swallowing that you will refuse water even when desperately thirsty is a worry as well, although in 30% of cases, people instead become slowly paralyzed from the site where they were bitten before falling into a coma.
Vaccines are available, but the $40-$50 it costs to vaccinate those who have been bitten is out of reach for much of the population where the virus is most common. A combination of rising incomes and philanthropic money is expected to make progress against dogs as a vector in the near future, which will mean we’ll be back to bats as the main problem.
These two closely related diseases are both triggered by Henipaviruses. The main difference between them is location, with Nipah seen in south and southeast Asia, while Hendra affects north-eastern Australia.
There are no known cases of humans catching the Hendra virus directly from bats, or from other humans. Instead, horses get infected, possibly from eating grass bats have urinated on. The bodily fluids of an infected horse can transmit the virus to humans. This has occurred three times, resulting in one death from respiratory and kidney failure.
The Nipah virus has been responsible for almost 300 deaths since 1999 with species such as pigs catching the virus from flying foxes, probably as a result of piggeries being extending into forest areas where the bats live. The pigs respiritory systems are affected, and once the disease reaches humans, seizures, vomiting and blurred vision are common. Roughly 60% of victims fall into comas and can become dependent on artificial ventilators. The death rate was around 40% in the original outbreak in Malaysia, but has subsequently reached as high as 90% in Bangladesh and India. While all cases appear to be traceable back to bats, much of it spread through person-to-person contact.
Though SARS symptoms aren’t as scary as other diseases and the number of SARS deaths has been below that of Ebola, and far below rabies, the fact that these viruses can be transmitted from human to human through the air make a potential pandemic much more threatening.
In 2003, the world held its breath (in some cases literally) as 774 people died and 8000 were infected with the SARS coronavirus. Patients suffered fever, sore throats, coughs and lethagy, making the condition very hard to tell from influenza, or even a bad rhinovirus. Some people also suffered viral pneumonia or secondary infections, again like flu. Survivors, however, often seem to have long term afflictions such as osteoporosis and major depressive disorder.
The only effective treatments are drugs to reduce the fever and breathing assistance, and we still don’t have a vaccine. Most of those infected in 2003 were in Hong Kong, but should an outbreak start somewhere with a weaker health care system, the disease could run riot.
Once again it is doubtful that humans caught SARS directly from bats. Instead passage may have been through susceptible animals such as masked palm civets (Paguma larvata) sold for food in Chinese markets. However, bats are considered the most likely reservoir.
Frightening as the possibility of a SARS return is, health authorities were able to stop the outbreak, which was quite widespread. The fact that it’s also transmitted far more easily between humans than the diseases above suggests our Ebola fears may be overblown.
Save The Bats
The discovery that bats transmit these diseases has led to huge culls of bat populations. This can backfire, and be ecologically disastrous as some bat species are essential pollinators, while others help control insect populations responsible for more common diseases. So we thought we would try to make you love them a bit with this video of what bats look like if you turn a video of them roosting upside down and add music.
One thing not to be overly worried about, however, is vampire bats. The idea of a blood sucking parasite may sound terrifying and this skeleton probably doesn’t help.
However, aside from the risk of contracting rabies, vampire bats are actually pretty harmless. They don’t even suck blood, although making a small wound and lapping at the blood that flows may not sound much better.
Two of the three vampire bat species prefer birds to mammals, and even the common vampire bat takes such a small amount of blood you’re unlikely to notice (which is kind of the point). Moreover the anticoagulant in the saliva of bat species Desmodus rotundus is currently being studied as a possible anti-stroke medication.
Vampire bats are also rather nice to each other. Young are adopted by colonies if something has happened to their mother, and males without a family are allowed to snuggle for warmth when temperatures drop. If a vampire bat doesn’t manage to find food for a night, others will regurgitate part of their meal to keep it alive.
Maybe you should offer to act like a vampire bat to anyone coming trick or treating. The truth might be more horrifying than fiction.
Wonder Of Science