The person on the other end turned out to be the Emergency Department Registrar (certainly crazy for working Halloween in the ED…!)
“I’ve got a patient who has been bitten on their hand by a bat and I wondered what antibiotics we should start. We have guidelines for dog, cat and even human bites but nothing for bats.”
“Why would it be a vampire bat in the UK?” replied the Registrar, clearly not getting the joke (it had probably been a rough night in the ED).
“Sorry, bad joke” replied the Microbiologist trying to be a little more professional, “Have you thought about rabies?”
“Is this another joke?” demanded the Registrar, “they have been bitten in the UK... and the UK is rabies free!”
“Ummm, that is not exactly true” said the Microbiologist, “The UK and Ireland are classified as ‘no risk’ but within the PHE guidelines there is a caveat to this around bats”. He paused, “I know it’s Halloween but this isn’t a joke”, added the Microbiologist.
I have now discussed the same bat bite scenario 3 times in the last 6 months so you should pardon me for going a bit batty. But it is clear that many Doctors (and the general public) don’t realise that the UK is technically NOT rabies free… some of our bat population have rabies!
Rabies in the UK
Public Health England (PHE) stratifies countries by risk:
- No risk – no rabies in terrestrial (land dwelling) animals
- Low risk – rabies in wild animals
- High risk – rabies in domestic and wild animals
The UK and Ireland are technically classified as “no risk” but within the PHE guidelines there is a caveat to this around bats. Both countries are actually classified as “low risk” for bat bites. Bats in the UK and Ireland can carry bat rabies, a lyssavirus. There are currently sixteen classified species of lyssavirus. Lyssa was the Greek spirit of fury, rage AND rabies in animals… who knew that rabies had its own Greek goddess… weird!
Although bat bites are still considered “low risk” in the UK and Ireland, rabies (European Bat Lyssavirus type 2 or EBLV-2) has been found in 15,000 tests on bats since 1986 hence why the UK and Ireland are not considered “no risk” for bat bites.
Until relatively recently in the UK and Ireland, it was thought rabies was only to be found in Daubenton’s bats however this year it was found in another UK bat species, the Serotine bat. This Serotine bat was found dead in Dorset and on testing, by the Animal and Plant Health Agency, was identified as not only being a new carrier species of the rabies virus but in fact a carrier of another subspecies of Lyssavirus, European Bat Lyssavirus 1 (EBLV-1); previously the UK had only identified EBLV-2.
There have also been at least five other deaths but the rabies was acquired abroad.
- 2001 - There were 2 cases following dog bites, one in Nigeria and the other in the Philippines
- 2005 - Following a dog bite in Goa
- 2009 - From a scratch from a dog in South Africa
- 2012 - A woman died after returning to the UK having been bitten by a puppy in India.
None of these people had been vaccinated or received post-exposure prophylaxis (see below).
How does the rabies virus cause infection?
Rabies virus likes neuronal tissue and it spreads from the site of the bite along the motor and sensory nerves to the central nervous system where it then causes damage to the brain.
The incubation period depends on the site of the bite and the amount of saliva. It can be as little as a few days to as long as several years, but it is usually around 3-8 weeks.
The likelihood of acquiring infection increases if the bite is on the face or head (less distance for the virus to travel) as well as bites with lots of saliva inoculated into the wound. There is also much less time to do something to try and prevent infection occurring following a bite on the face and head, again because the virus has less distance to travel.
How does rabies present?
Rabies starts with a prodromal illness (early) with fever, chills, malaise, myalgias, weakness, fatigue, anorexia, sore throat, nausea, vomiting, headache, and occasionally photophobia lasting up to a week. Once symptoms occur there is an almost inevitable progression to encephalopathy and death. Survival is exceptionally rare.
Following the prodromal illness there are two clinical forms of rabies:
- Encephalitic “furious” rabies (80%) - fever, hydrophobia, aerophobia (pharyngeal spasm) and hyperactivity leading to paralysis, coma and death
- Paralytic “dumb” rabies (20%) – ascending flaccid paralysis from the site of the bite eventually leading to paralysis of the respiratory muscles and death
Hydrophobia is perhaps the most well-known symptom of rabies, occurring in 33-50% of cases. In hydrophobia the patient develops overwhelming terror of water due to involuntary pharyngeal muscle spasm which occurs when trying to drink; later even the sight or mention of water may trigger these spasms. Aerophobia occurs in about 9% of patients but rather than water it is the feeling of air that triggers the pharyngeal spasms; these can be so severe that they cause a respiratory arrest.
Agitation and aggressiveness occurs in 50% of patients, sometimes with visual hallucinations, hence the term “furious rabies”. They are often hyper-aroused with increased salivation, dilatation of pupils and “goose” flesh… all part of a heightened “fight, flight or fright” response.
How is rabies diagnosed?
The diagnosis of rabies is a super-specialised area of medicine involving collaboration between human and veterinary diagnostic services. In the UK rabies is a notifiable disease and anyone with possible rabies MUST be discussed with Public Health England. The patient should be transferred to the High Level Isolation Unit at the Royal Free Hospital in London for specialist care.
Diagnosis is based on a combination of tests including serum antibodies, skin biopsies, saliva and CSF testing for virus. The testing is usually undertaken by the Animal and Plant Health Agency based in Weybridge, Surrey… not far from where I am writing this in fact!
Can rabies be treated?
Unfortunately, the normal treatment of rabies is palliative, keeping the patient comfortable until they die. Aggressive “treatment” is attempted in young, previously fit and healthy patients who would be willing to live the rest of their life with severe neurological disabilities.
Aggressive treatment after developing symptoms involves rabies immunoglobulin, as well as vaccine, a combination of supportive care and the use of unlicensed experimental treatments, which may have some benefit. These include: Interferon alpha, Ribavirin, Amantadine and Favipravir (which has been shown to have some effect in animals).
There is no really effective way of treating rabies, and as of June 2017 there have been only 15 known survivors against a background rate of 60,000 cases a year worldwide! IF YOU DEVELOP CLINICAL RABIES YOU WILL PROBABLY DIE!
So given that you will die if you develop rabies it is much better to try and prevent it occurring in the first place!
Anyone travelling to a rabies high risk country should be vaccinated against rabies. Rabies vaccination is almost 100% effective at preventing rabies.
Many people decline rabies vaccination because they feel they are unlikely to be bitten by a rabid dog but remember it is not just dogs but any mammal that can transmit rabies and it does not need to be a bite, saliva and scratches also pose a risk.
Note: If you intend to visit a high risk country and have been advised that rabies vaccination is recommended declining it will also make your travel insurance invalid if you require treatment or post-exposure prophylaxis for rabies; you did not take adequate precautions to prevent the disease in the eyes of the insurance companies (I know because I have checked with a number of travel insurance companies!).
I once asked a Virologist what they would do if someone didn’t want to have the rabies vaccination before going to a high risk country and their response was “show them a video of someone with rabies”… so here is a patient with rabies [warning it is a distressing video!]
What if I’ve just been bitten!
If you are bitten by an animal on holiday or exposed to saliva or scratches then it is imperative that you seek medical help as soon as possible. Post-exposure prophylaxis with rabies immunoglobulin (RIg) and vaccination is still able to prevent the development of rabies in most people exposed. HOWEVER, it may not be easily available in the country you have travelled to, and having injections may expose you to other blood borne viruses such as Hepatitis B, C and HIV, and you will probably have to curtail your holiday and get back to the UK for further treatment.
Post-exposure prophylaxis is very good if given early enough with only 47 failures in 15 million cases by 1997, but it is not fool proof, and if it is not given quickly enough it doesn’t work at all. In addition, some people don’t realise they have been exposed as it is not just dog bites that lead to rabies, but saliva exposure from all terrestrial animals (any mammal can carry rabies not just dogs).
Another drawback to post-exposure immunoglobulin is that RIg costs £600 per 500 unit vial, and the dose is 20 units/kg, so for a 70kg patient this is three vials (1400 units) but given that most adults in the UK are overweight or obese this is more likely to be 4 vials. Then there is the need for 4 vaccines too!
This means that post-exposure prophylaxis with RIg and 4 doses of vaccine costs approx. £2,600; in a resource poor country you will either have to pay for this yourself (remember your travel insurance will be invalid) or it won’t be available at all. If it is available and “free” you are using £2,600 of medical resource from that country… you’ll have to decide for yourself on the ethics of not being vaccinated against having “free” post-exposure prophylaxis.
Even if you have been fully vaccinated you would still be given further doses of vaccine after an exposure BUT to my knowledge no one has ever developed rabies having been fully vaccinated before exposure (your travel insurance should cover this treatment).
In the UK post exposure prophylaxis should be discussed with the Rabies Immunoglobulin Service at Colindale in London on 0208 327 6204, or if urgent out of hours with the Colindale Duty Doctor 0208 200 4400. They will carry out a risk assessment based on country and type of exposure; they hold the stock of rabies immunoglobulin and will arrange to send it out if it is required. They offer a fantastic service which in my experience works flawlessly… they really are brilliant!
So our patient bitten by a bat was discussed with the Rabies Immunoglobulin Service in the morning who arranged to send out rabies immunoglobulin and advised 4 doses of rabies vaccine. Fortunately the patient remained well and didn’t develop the infection. The ED department produced local guidelines for bat bites including the telephone number for the Rabies Immunoglobulin Service… and the Microbiologist got a Halloween topic for his blog… everyone was happy.
So enjoy your trick or treating but do stay away from bats and other scary mammals… even those in fancy dress might pose a low risk!