European Bat Lyssaviruses in the United Kingdom: Focus on Changing Epidemiology and Detection Methods

Aminu Shittu.Department of Public Health and Animal Production,

Faculty of Veterinary Medicine,Usmanu Danfodiyo University,

Sokoto.

Overview• Introduction• Distribution • The Rhabdoviridae family• Importance of EBLVs• Diagnostic tests• Diagnosis• Past and current situations in the UK• Surveillance and control in the UK• Future strategies• Control scenarios• Conclusions/recommendations

Introduction

• BATS– Kingdom: Animalia– Phylum: Chordata– Class: Mammalia (20%)– Infraclass: Eutheria– Superorder: Laurasiatheria– Order: Chiroptera– Distribution: worldwide– Habitat: caves, old buildings,

trees

Distribution

The geographical distribution of Eptesicus serotinus in Europe

• First description in the Hebrew Talmud

• Various Arabic writings

• Rabies• Lagos – bat• Makola• Duvenhage• European Bat Lyssavirus type 1 (EBLV – 1)• European Bat Lyssavirus type 2 (EBLV – 2)• Australian Bat Lyssavirus (ABL)

The Rhabdovirus family

European Bat Lyssaviruses

• EBLVs in Europe – 1954• Genetics – N &/or G genes• EBLV – 1

• 2 lineages 1a & 1b• Majority in E. serotinus

• EBLV – 2• First isolated in 1984 from human biologist• Isolated in 1986 in M. daubentonii and M.

dasycneme

Virus Genotype Geographical origin Original Host Secondary Host

Classical Rabies virus (RABV)

1 Worldwide* Dog, Fox, Cat, Wolf, Skunk, Racoon, Mongoose, American bat

Mammals, Man

Lagos Bat Virus (LBV) 2 Nigeria Frugivorous bat Cat, Dog

Mokola Virus (MOKV) 3 Nigeria Shrews, Rodents Cat, Dog, Man

Duvenhage Virus(DUVV) 4 South Africa, Zimbabwe

Insectivorous bat Man (1971)

European Bat Lyssavirus 1a/1b (EBLV-1a/EBLV-1b)

5 Denmark, Germany, Netherlands, Poland, Russia, Slovakia, France, Spain

Insectivorous bat (esp. E. serotinus)

Man (1985)

European Bat Lyssavirus 2a/2b (EBLV- 2a/EBLV-2b)

6 Netherlands, UK, Finland, Switzerland

Insectivorous bat (Myotis daubentonii, Myotis dasycneme)

Man (1986, 2002)

Australian Bat Lyssavirus (ABLV)

7 Australia, Philippines Insectivorous bat (S. flaviventris), Frugivorous bats (genus Pteropus)

Man (1996)

Aravan (ARAV) Unclassified Southern Kyrgyzstan Insectivorous bat (M. blythii)

Unknown

Khujand (KHUV) Unclassified Northern Tajistan Insectivorous bat (M. mystacinus)

Unknown

West Caucasian Bat Virus (WCBV)

Unclassified Caucasus Insectivorous bat (Miniopterus schriebersii)

Unknown

Irkut Virus (IRKV) Unclassified Eastern Siberia Insectivorous bat (Murina leucogaster)

Unknown

Lyssavirus classification, with geographical origin, original and secondary host species

The importance of EBLV rabies

• Bat rabies is an emerging zoonosis

• Public health threat• High risk groups:

– Bat handlers– Cavers– Researchers– Wildlife officers– Veterinarians

The importance of EBLV rabies (2)

•Rabies is a zoonotic disease which is invariably fatal in all humans that are not vaccinated and do not get post-exposure treatment

•5 cases of human exposure in Europe so far including a fatal case in Scotland (2002)

•Spillover of EBLV-1/EBLV-2 into humans, sheep, stone marten and domestic cats has been reported (see Harris et al. 2006).

•EBLV is endemic in some European countries’ bat population and the possibility of infected bats coming to the UK cannot be ruled out.

•Likelihood of impact

Diagnostic tests

• Direct fluorescent antibody test (dFA)

(Standard test for rabies)• RT-PCR• Other tests Electron Microscopy (EM) Histopathology Immunoperoxidase staining Virus Isolation

Test Specimen required Test detects Time taken to ob-tain result

Fluorescent antibody test

fresh brain Virus antigen 4 hours

RT-PCR virus or tissue virus genome 1-2 days

Histopathology formalin-fixed brain characteristic le-sions

2 days

Immunoperoxidase staining

formalin-fixed brain Virus antigen 2 days

Virus isolation using mouseneuroblastoma cells

fresh brain Live virus 3 days

Rabies Diagnosis (1)

Direct Fluorescent Antibody Test (DFAT)• Detection of virus nucleocapsid protein infected tissues

Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) • Can be used to detect presence of pan-lyssavirus in saliva or oropharyngeal samples (specific primers can be used detect specific EBLV)

Rabies Tissue Culture Inoculation Test (RTCIT)• Homogenised suspension of suspect tissue (brain or saliva) is inoculated into tissue culture for isolation of virus

Rabies diagnosis (2)

Mouse Inoculation Test• Inoculation of homogenised suspect tissue into cerebellum of 48h old mice for later virus isolation

Modified Fluorescent Antibody Virus NeutralisationTest (mFAVN)• Can be used on pooled saliva or blood samples for detection of antibodies to EBLV

Histopathology• Detection of negri bodies in brain tissue

Vaccination

Human Animals

Two rabies vaccines licensed for use in the UK (Aventis Pasteur, Rabipur)

Oral route (Live vaccine)

Animals Rabies vaccines(Only inactivated rabies vaccines are li-censed for use in the UK)

Past and current situation of EBLV-1 in the UK

EBLV-1 seroprevalence in bats:

• 1 serotine bat in the South of England (2005)

• 1 serotine bat in Scotland (2007)

Past and current situation of EBLV-2 in the UK

EBLV-2 seroprevalence in bats:

• The seroprevalence in Daubenton’s bats in

England and Scotland is estimated at 2% (95%

confidence interval 1 to 5%)

• 8 infections with EBLV-2 confirmed in

Daubenton’s bats

Surveillance of bat Lyssaviruses

• Sample submission: members of public and bat conservation groups

• Sick, injured or suspect cases, captive bats

• Testing animals and humans bitten by suspect bat

Strengths and weaknesses of surveillance

• Bias due to location and bat conservationist activity

• Not a representative sample

• Sensitivity – only method by which EBLVs detected in the UK

The control of EBLVs in the UK

Current strategies:• The public• Bat handlers

Current control strategies• Health education• Raising awareness

Public:No bat handlingIf pet is bitten: advice on potential risk and report any suspicious signs to the local vet.

Bat handlers:• If bitten seek medical advice• Prevent direct contact - gloves • Pre-exposure vaccination and Post-exposure

treatment

Stokesay Castle example• Follow up possible

human contacts• Advise to receive post

exposure treatment • Public access to second

floor was not allowed• Signs informing visitors

about the bats• Staff checking for bats

before opening

But does the classical rabies vaccine protect humans against EBLV?

Genotype 1: classical rabiesGenotype 5: EBLV1Genotype 6: EBLV2

Future Strategies

• Legislation changes• Compulsory vaccination of bat handlers• Wild bats: cannot control their movement,

vaccinate using RAORAL V-RG• Quarantine bats coming in ships from other

countries• Prevent colony establishment in certain

buildings (e.g. schools, hospitals)• Preventive immunization of populations living in

highly endemic areas

Control Scenarios

Translocation of Wild bat colony

• Geographic translocation of bats could potentially spread EBLV

• Natural, accidental or deliberate means

• Protracted incubation period allows survival of the virus

• Bats undergo hibernation to extend survival

• What could be done;-Consult bat conservationists-If suspect EBLV should be tested-If positive should be killed-If negative would have to be housed

Identified in Novel Bat Species

• Currently in only two species found in the UK

• Testing finds antibodies/antigen in naive species;

-Surveillance will expand-Communicate to bat conservationists

and public

Infected bats in public places

• Infected bat found which roosts in public area;

-Random sampling of roost

-Slaughter not an option

-Possibly move population??

-Warn public and protect staff

4.EBLV found in bats away from public

• As negligible risk to humans – continued

surveillance:

– Collection of excreta for virus detection and

serology

– Marking of sampled bats

– Collection and testing of dead/sick bats

4.EBLV found in bats away from public

• If clinical disease detected:

– Epidemiological data: destruction of bat

colony ineffective

• disturbs metacolony

• may cause dispersion of infected animals.

– Enhanced surveillance.

5.EBLV found in carnivores• Transmission of lyssaviruses from bats to terrestrial

mammals and humans rare, none so far in UK BUT

– EBLV1 demonstrated in sheep in Denmark

– Lyssaviruses isolated in cattle/foxes in Canada.

5.EBLV found in carnivores

• If infected bat preyed upon by foxes or cats• FOXES

• CATS • POSITIVE -> PTS BUT difficult to detect until showing CS or seen attack

• PREVENTION : cats indoors during high risk periods i.e. summer & evenings where bats resident.

• EDUCATION

• Very difficult!• Oral baits: BUT classical rabies oral vaccine not

protective against EBLV1• Culling near urban areas?

6. EBLV clinical disease in humans

• In highly unlikely event of outbreak in humans:

– Pre & post exposure vaccination

– EDUCATION

– Signs/barriers near colonies: prevent

access & direct bat movements

– Bat-proofing buildings

– Vaccinating/culling bats?

Conclusions/recommendations

• EBLVs can cause fatal infections in humans• Bats can excrete EBLV in saliva but amounts

are unknown• Public health risk of EBLV in bats cannot be

ignored but is hard to assess• Active and passive surveillance• Improved detection methods• Translocation factors