Rhabdoviridae family tree

Bats and Rabies

Horseshoe bat
Horseshoe Bat

One of the most common misconceptions of bats is that they all carry diseases that can be fatal to humans. This is a misconception that scientists, bat ecologists and bat carers have been trying to change for years. Bats have endlessly been persecuted for rabies, a virus that is detrimental to human and mammal populations over the world.  While it is true that bats can carry the disease, all mammals can spread the virus – not just bats!

What is Rabies?

Rhabdoviridae family tree
Rhabdoviridae family tree. Those viruses which are covered in this article are coloured in red.

Rabies is part of the virus family ‘Rhabdoviridae’. Within Rhabdoviridae is a group of viruses called Lyssavirus, of which there are sixteen known types. In Europe, there are three types of Lyssavirus:

  • Rabies Virus (RABV)
  • European Bat Lyssavirus 1 (EBL-1)
  • European Bat Lyssavirus 2 (EBL-2)

Rabies (RABV) is the most commonly known viral disease. However, all of the Lyssaviruses can lead to rabies-like encephalitis (inflammation of the brain, caused by infection or an allergic reaction).

Rabies (RABV) is a virus that effects the central nervous system of mammals. There is no cure for this virus; you can only prevent it from infecting you using vaccinations. It is transmitted through salvia or via an opening in the skin, such as through bites or scratches.

Rabies kills its victims by attacking the brain – it compromises the victim’s ability to regulate their breathing, heartbeat and salivation. Essentially, the bitten person will drown in their own spit or blood, or they will not be able to breathe due to muscle spasms in the diaphragm. In some cases, they die from heart arrhythmia.

There are two different clinical signs of rabies:

  • The angry form, the form most associated with the virus where the victim will be agitated, have hyperactivity and hypersalivation; and the
  • The paralytic form where the victim will seem weak and slowly have gradual paralysis.

It is zoonotic – meaning that it can easily spread from animals to humans. Human-to-human transmission through bites is very rare, but it can spread (again very rarely!) through infected organs being transplanted inside of another body. Human infection is almost always fatal without the pre-vaccinations and, even with these vaccinations, booster rabies vaccinations must be administered straight away after exposure to the virus.

99% of rabies cases worldwide are due to dogs infected with the classical rabies virus (RABV) biting humans. The classical rabies virus is the strain that occurs in an urban environment, dogs are the main reservoir host. The other strains of rabies viruses are part of the group associated with the sylvatic or wildlife cycle. Meaning that the virus occurs predominantly within wildlife hosts and has a far more complex cycle, as the behaviour of the host, the ecology of the species and its environment can all effect the virus.

Evolution of the Rabies Virus

Lyssaviruses (including classical rabies) are a diverse group of viruses with sixteen classified species of Lyssavirus found worldwide, including islands such as Australia and New Zealand (although both of these countries have never encountered the classical rabies virus (RABV)). Through phylogenetic studies, it is thought that the original hosts of the lyssaviruses were bats and that the viruses originated from Africa.

However, the evolution of bats predates the evolution of the lyssaviruses, so some scientists disagree with the theory of their co-evolution. The classical rabies virus (RABV) has evolved to have a variety of carriers (only mammals) which makes this virus deadly, due to a higher risk of transmission. However, many countries (including the UK) are (classical) rabies (RABV) free.

The other species of Lyssaviruses have specific species hosts which means the spread of those viruses is limited to those hosts.

But this also means that no country is Lyssavirus free – all countries may have a form of Lyssavirus within their mammal populations.

Rabies and European Bat Lyssaviruses 1 & 2

Serotine bat
Serotine

Bats can contract two species of Lyssavirius: European Bat Lyssavirus (EBLV) 1 and 2.  In Europe, there have been over 750 total recorded cases of Lyssavirus in bats, with over 95% of these being EBLV-1.

European Bat Lyssavirus 2 (EBLV-2) has been assumed to have always been present but at a very low prevalence in Daubenton’s bats in the UK. There have been two cases of EBLV-2 being transmitted to humans both of whom died from the virus. EBLV-2 attacked the host much in the same way the Rabies virus (RABV) does.

EBLV-1 and EBLV-2 are both strains of the rabies virus that are adapted to their bat hosts, so humans catching the virus has been documented but is extremely rare. The infection of EBLV viruses in other animals is very rare too; however, two cats in France were found with the virus. This was one of the only cases where rabies has been spread from bats to cats – this is astounding considering the numbers of bats that cats catch each year!

Classical rabies (RABV) may not be fatal to bats like it is in humans, scientists have considered the fact that bats may simply be carriers of the RABV virus. Further studies are needed to fully understand these viruses.

 

The UK and Rabies

The UK has been officially rabies-free since 1902. It was not bat’s that health experts were concerned with when it came to the spread of rabies. It was our domestic dogs and wild foxes! However, the disease returned in 1918 when people tried to smuggle in infected dogs. This caused a six-month quarantine system to be put in place on all animals being brought into the country – this system is still in use today! All cats and dogs are required to be vaccinated against rabies if they are to leave and then return to the UK.

The UK became rabies-free through oral vaccinations. Foxes and feral dogs were the main transmitters of the disease in the UK, so a vaccination was produced and inserted in baits which were spread countrywide across the countryside to tempt the animals to eat them. This method, plus the strict quarantine rules we have today, are why the UK is currently rabies-free.

However, UK bats have been found to carry European Bat Lyssavirus. The Animal and Plant Health Agency has tested over 15,000 bats in the UK since 1986 for EBLV and less than 0.2% (<30) have tested positive for the virus. These bats have all be sent in by bat carers, ecologists or the public. Since 1977, there have only been five EBLV related deaths in the UK and it was always due to handling wild bats without suitable protection.

The presence of EBLV in our bat populations does not affect the rabies-free status that the UK holds as this only relates to the typical ‘classical’ rabies virus.

UK Bats and EBLV

In 2002, one person in Scotland contracted rabies-like symptoms from a Daubenton’s bat, which was infected with European Bat Lyssavirus 2. Two more European bats were identified as having the disease the following year. Since this occurrence, the Bat Conservation Trust have made it their priority to monitor rabies in UK bat populations, as well as enforcing the rule preventing the public from handling bats. Those handling and working with bats must wear protective gloves and be vaccinated against rabies.

In 2018, a dead serotine bat in Dorset was found to have contracted European Bat Lyssavirus 1. This form has never been found in the UK before and research is still being conducted on how this virus arrived here. It is suspected that either: the bat contracted the disease from another species of migrating bat; or that the bat may have contracted the disease in France and migrated to England from France.

There is still an incredibly low risk of contraction of rabies. Only those who handle bats, or work with bats on a regular basis, have any risk of contracting the virus.

Survivors of Rabies

Jenna Giese-Frassetto - the only person to survive Rabies
Rabies survivor

There are only five documented cases of people surviving without having the preventative rabies vaccination beforehand.

One of which was an eight-year-old girl in the US who picked up a rabid bat outside her home. Once bitten, the doctors attempted to give her all the vaccinations that would have saved her life had she had them beforehand. They then decided to induce a coma for seven days, to shut the brain off so that her body would have enough time to produce the antibodies needed to fight the virus off. When they woke her up from the induced coma, she had to learn to speak, read, walk and write again. She also had slight physical side-effects from both the coma and the virus. However, she survived rabies and is more or less completely back to health, and living a normal life. She is the only person to have survived with doctors utilising this method of inducing a coma. They tried this method again on a 33-year-old man, however, it failed.

Worldwide and Rabies

The deadliest species of Lyssavirus is classical rabies (RABV) virus has caused countless deaths worldwide. The main (classical) rabies-free jurisdictions are:

  • Most of Europe
  • Australia
  • New Zealand
  • Singapore
  • Fiji
  • Guam
  • Hawaii
  • Japan
  • Taiwan/ROC

These countries are free of classical rabies (the most severe form of lyssavirus), but not from all lyssaviruses.

Countries within the following continents still have classical rabies:

  • Africa
  • Asia
  • India
  • Indonesia
  • Central and South America
  • North America
Rabies map

VaccinationIf you have the rabies vaccination, the risk of getting rabies is very low. It is important for people who plan to work closely with mammals in affected countries to get the vaccination. If you are not vaccinated then it is advised to not go near any stray dogs or cats or any isolated places where you cannot get to the nearest hospital easily. However, your GP would always advise you to have the vaccination to be safe. The rabies vaccination protects against all the species of Lyssavirus.

It is not just bats!

Dogs can carry rabies tooYou are more likely to contract rabies from pets than you are from wildlife. We are constantly exposed to our pets in our own homes whereas wildlife avoids us as much as they can. If pets contract rabies from feral dogs, cats or wildlife, then it is likely to be those animals that then pass on the virus to humans. In fact, dogs are the principal host in most countries. Worldwide there are estimated 59,000 deaths every year due to classical rabies (RABV) and the most affected countries are Asia and Africa (95% of rabies cases occur in Africa and Asia). This is mainly because of the high population of feral dogs, and because of the Asian pet boom.

Do not Panic! You cannot get RABV in the UK!

Classical rabies (RABV) is not an issue in the UK. For any country that you decide to travel to that has mammals with rabies, you are required to be vaccinated against the virus. It is only a risk if you plan to handle wild or stray animals. If you don’t plan to, then admire the animals from a distance and enjoy your holiday!

Bats

 

 If you enjoyed reading this, why not click here to read our other Wildlife Disease articles:

Bird Flu: Should we be Worried?   Deadly Bird Feeders

References

  1. http://www.who.int/rabies/about/en/
  2. https://www.elsevier.com/connect/8-things-you-may-not-know-about-rabies-but-should
  3. https://www.scientificamerican.com/article/jeanna-giese-rabies-survivor/
  4. https://en.wikipedia.org/wiki/Prevalence_of_rabies
  5. https://www.nbcnews.com/healthmain/can-people-survive-rabies-some-vampire-bat-victims-may-have-918714
  6. http://www.pulsetoday.co.uk/news/clinical-news/phe-issues-national-warning-to-gps-after-rabid-bat-found-in-uk/20037614.article
  7. https://www.theguardian.com/society/2012/may/23/rabies-case-confirmed-in-uk
  8. http://www.bats.org.uk/pages/-bats_and_rabies-1099.html
  9. https://www.wormsandgermsblog.com/2009/02/articles/diseases/rabies/european-bat-lyssavirus-in-cats/
  10. https://www.pettravel.com/passports_rabies_countries.cfm
  11. https://www.healthlinkbc.ca/health-topics/zr1043
  12. Johnson et al., 2011. Pathology Associated with a Human Case of Rabies in the United Kingdom Caused by European Bat Lyssavirus Type-2. Intervirology 55(5):391-4.)
  13. http://www.bristol.ac.uk/biology/research/behaviour/batlab/members/harris.s.html
  14. http://www.jeannagiese.com/my-personal-story.html
  15. http://www.who.int/rabies/about/home_symptoms/en/
  16. http://www.cfsph.iastate.edu/Factsheets/pdfs/rabies.pdf
  17. http://www.who.int/rabies/epidemiology/en/

Author: Ashley Dale