Organising, coordinating, implementing and monitoring oral fox vaccination campaigns against rabies

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In France, in 1968 following the first vulpine rabies cases in the North-East of country, the front advanced rapidly westwards and southwards. In 1971, nine departments, totalling an area of 25000 km² were infected. The laboratory was built in 1971 in the infected area to conduct rabies diagnosis on suspect and found dead animals.

In the 1970s, the laboratory extensively participated in scientific research work for developing oral vaccine baits to control the disease in fox population.

A number of experimental trials were undertaken to check efficacy and safety of vaccines before their marketing, in collaboration with other international groups involved in rabies activities. In 1986, the laboratory tested the first available methods of oral vaccination with baits (chicken head baits) deposited in the field by manual distribution. From 1990, the overall organisation of the oral vaccination campaigns has been centralised: the Anses-Nancy Laboratory for rabies and wildlife was requested by the national competent authority to organize and plan the oral vaccination of foxes and, in close cooperation with its delegates, to implement and evaluate the programmes.

From 1988 to 1998, year of the last recorded case of vulpine rabies in France, the laboratory planned the strategy and implemented oral vaccination campaigns in infected areas twice a year using helicopters. These campaigns were then prolonged until 2003 along Northern and Eastern borders and were performed once again in 2005.

Several field trials have been conducted to improve the efficiency of oral vaccination programme, particularly to promote cubs' coming into contact with baits and also to counterbalance the increase of the fox population.


 

Rabies surveillance and vaccination monitoring

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Based on the collection of animals found dead, road killed, suspect animals as well as all animals having contamined humans, the national surveillance network is organised as represented below :

• In case of human contamination (bite, scratch), animal cadavers are sent by the veterinary services to the Pasteur Institute.
• In all other cases, they are submitted by the veterinary services to Anses for rabies testing.
   

Rabies surveillance is the key element of rabies control and prevention programmes. It is based on laboratory investigations on samples taken from susceptible suspect animals to collect sufficient spatial and temporal descriptive data used to build the control programme.

The national network for animal rabies surveillance is centralised at Anses-Nancy laboratory for rabies and wildlife. The incidence of rabies in animals is currently assessed throughout all the country by undertaking diagnosis on suspect animals using the OIE and WHO reference tests, i.e. the fluorescent antibody test and the real time RT-PCR  (WHO, 2018; OIE, 2018). The positive cases are systematically investigated by sequencing to characterise the virus strains of isolated lyssaviruses, and also to study the circulating field isolates in the country.

The monitoring of the efficacy of oral vaccination programmes was conducted in vaccinated areas by:..

• Assessing bait uptake by testing the target species (foxes) in vaccinated areas for biomarker (tetracycline) occurrence and assessing age categories of foxes marked by tetracycline.
• Assessing rabies antibodies in target species in vaccinated areas: a cell virus neutralisaion method by using an ELISA previously validated for wildlife sample titration.

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Technical competences in rabies

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The laboratory currently uses the folowing laboratory methods (Table 1):

Table 1
Areas	Methods	Comments
Diagnostic	FAT RTCIT DRIT Conventional RT-PCR SYBR Green RT-PCR TaqMan RT-PCR
Serology	FAVN test Indirect ELISA Competitive ELSA	Used  on  animal  sera  and  animal immunoglobulins
Vaccine potency testing	NIH Pharmacopeia test TSA
Monitoring of vaccination programmes	Biomarker determination Age determination	Both on tooth samples
Virus titration	On cells On animals

 

 

The laboratory is experienced in the development, validation and standardisation of laboratory methods, mainly for diagnosis and serology, and regularly organises international workshops, inter-laboratory studies and proficiency tests.

 

The laboratory is enrolled in quality assurance (Table 2):

Table 2
Standard	Test	Accreditation body
NF EN ISO/IEC 17043	Organization of rabies serological proficiency test	COFRAC (since May 2017)
NF EN ISO/IEC 17025	FAT  (Lyssavirus antigen) and RTCIT (Lyssavirus)	COFRAC (since October 2012)
NF EN ISO/IEC 17025	Molecular Biology (Lysaviruses RNA detection)	COFRAC (since March 2020)
NF EN ISO/IEC 17025	Control of efficacy of live oral vaccines in wildlife	Mutual Joint Audit (EDQM) (since January 2012)
NF EN ISO/IEC 17025	Control of efficacy of inactivated rabies vaccines for veterinary and human use (challenge test and serological test)	Mutual Joint Audit (EDQM) (since March 2008)
NF EN ISO/IEC 17025	Rabies virus seroneutralisation test (FAVN test)	COFRAC (since February 2008)

 

 

The laboratory developped several methods (Table 3):

Table 3
Name of the test developed	Use	References
Straw sampling kit	Simplified technique dor the collection, storage and shipment of brain material from animals for rabies diagnosis	Barrat et al., 1986 - WHO, 1987 - WHO, 1996 -    WHO, 2018
Simplified test for potency testing of inactivated veterinary vaccines	Potency testing of vacines using one dilution of the vaccine	Aubert, 1982 - WHO, 1996 - European Pharmacopeia, 2014
FAVN (Fluorescent Antibody Virus Neutralization) test	Titration of seroneutralising rabies antibodies in human and animals blood samples	Cliquet et al., 1998 - WHO, 2018 - OIE, 2018
Indirect ELISA	Titration of rabies virus antibodies in wildlife samples for vaccination monitoring	Cliquet et al., 2000
Paper-based diagnosis for sample sending through normal postal means	Impregnation of rabies suspect brain tissue to allow safe and cost effective shipment of diagnosis samples	Picard Meyer et al., 2007
Paper-based technology to collect blood samples of wildlife	Impregnation of blood samples to allow simple collection and storage of field samples for further serological testing using ELISA	Wasniewski et al., 2014
Hemi-nested RT-PCR method	Specific determination of EBLV-1 Lyssavirus	Picard-Meyer et al., 2004

 

 

The laboratory is also organising proficiency tests (Table 4):

 

Table 4
Proficiency test	Since	Frequency
Dog and cat rabies serology	2000	Annual since 2009
Rabies diagnosis (FAT, RTCIT, RT-PCR, Real Time RT-PCR)	2002	Annual since 2009 Every two years since 2017
Tetracycline biomarker and age determination	2010	Every two years

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Research activities on rabies

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A the present time, the research work of the laboratory is mainly intended to increase knowledge on the pathogenicity of certain rabies viruses (those that infect European bats), to develop experimental models and to investigate the transmission of bat lyssaviruses to other bats and to non flying animals.

 

 

0 November 2014