Risk of rabies introduction by non commercial movement of pets
1 / 19

Risk of rabies introduction by non-commercial movement of pets - PowerPoint PPT Presentation

  • Uploaded on

Risk of rabies introduction by non-commercial movement of pets. P. Have, L. Alban, L.T. Berndtsson, F. Cliquet, P. Hostnik, S.C. Rodeia and M. Sanaa.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'Risk of rabies introduction by non-commercial movement of pets' - tadeo

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Risk of rabies introduction by non commercial movement of pets

Risk of rabies introduction by non-commercial movement of pets

P. Have, L. Alban, L.T. Berndtsson, F. Cliquet, P. Hostnik, S.C. Rodeia and M. Sanaa

The EFSA Journal (2006) 436 1-54, ”Assessment of the risk of rabies introduction into the UK, Ireland, Sweden, Malta, as a consequence of abandoning the serological test measuring protective antibodies to rabies”

Current legislation
Current legislation pets

  • Regulation (EC) No 998/2003

    • valid anti-rabies vaccination

    • waiting time of at least 21 days (COM 2005/91/EC)

    • derogations for UK, Ireland, Sweden and Malta to maintain serological test

    • review of derogations at the end of transitory period of 5 years following receipt of a scientific opinion of EFSA

Efsa mandate
EFSA mandate pets

  • Commission requested EFSA to issue a scientific opinion on the risk assessment of rabies introduction into Ireland, the UK, Sweden and Malta, as a consequence of abandoning the serological test for antibody titration for rabies

Mandate cont
Mandate cont’ pets

  • To what extent the abandoning of the individual serological test for neutralising rabies-antibodies titration could be envisagedwithout increasing the risk

  • If the need to maintain the serological test is scientifically justified, what is the regime to be considered as giving equivalent assurance

Approach pets

  • Quantitative risk assessment based on

    • prevalence of rabies in the country of origin in pets

    • distribution of incubation periods of rabies

    • efficiency of establishing protective immunity by vaccination

    • specificity of the neutralization test for rabies (RFFIT or FAVN)

    • length of the waiting period

Model parameters
Model parameters pets

Prevalence (P)

  • estimated from annual incidence data by assuming a mean incubation time of 38 days

  • pet population size estimated from 1.0 dog and 1.1 cats per 10 people

    P = incidence*38/(population at risk*365)

Model parameters1
Model parameters pets

Incubation period

  • distribution of incubation periods

    • Dogs: 1 week to several months

    • Cats: 9 days to 6 months

  • described by a log-normal distribution with mean 38 days

Model parameters2
Model parameters pets

Efficiency of vaccination (Ev)

  • assessed indirectly by measuring the antibody response

  • measured after first, single vaccination

  • absence of antibodies not always associated with loss of protection

  • interval between vaccination and testing major determinant

  • Ev of 98% used tentatively in this study

Model parameters3
Model parameters pets

Test specificity (Sp)

  • determines whether truly antibody-negative individuals are correctly assigned as such or whether some individuals are classified as false positive

  • FAVN test more specific than RFFIT

  • a tentative value of 99% is used here

Model parameters4
Model parameters pets

  • Length of waiting period (t)

    • Measured from time of vaccination

    • t will determine the residual prevalence Pa of animals incubating rabies due to pre-vaccination exposure

Model description prevalence a and b
Model description petsPrevalence A and B

  • prevalence Pa of animals already incubating rabies will gradually decrease as a result of developing clinical disease

    Pa = P * f(t)

  • prevalence Pb of animals infected after the time of vaccination will gradually replace Pa

    Pb = P * (1- f(t))

Model description risk a and b

Type A risk pets

Type B risk with vaccination

Type B risk with vaccination and serology

Ra = P * f(t) = Pa

Rb = (1 - Ev) * Pb

Rb = (1 – Sp) * (1 - Ev) * Pb

Model descriptionRisk A and B

Model description total risk
Model description petsTotal risk

  • Total risk Rtot that an animal incubates rabies at time t after vaccination and serological testing is given by the sum of Ra and Rb:

    Rtot = P * f(t) + (1 – Sp) * (1 - Ev) * Pb or

    Rtot = P * (f(t) + (1 – Sp) * (1 - Ev) * (1- f(t))) or

    Rtot = P * (1 – (Ev + Sp - Ev * Sp )*(1- f(t))

Model description modelling f t
Model description petsmodelling f(t)

  • Sample an incubation period (ip) from the lognormal distribution

  • Sample an interval between infection time and vaccination (int) from a uniform distribution between 0 and 365 days prior to vaccination

  • F(t) calculated from positive values of ip-int

  • 100.000 iterations

Model description non linear least squares estimate of f t
Model description petsnon-linear least squares estimate of f(t)

  • f(t) = exp(-0.0313*t)

Rtot = P * (1 – (Ev + Sp - Ev * Sp )*(1- exp(-0.0313*t))