Download Quantification of transmission of FMDV strain Asia-1 Turkey among vaccinated and non-vaccinated lambs

Quantification of transmission of FMDV strain Asia-1 Turkey among vaccinated
and non-vaccinated lambs
P.L. Eblé1, K. Orsel2, A. Dekker1
Results
Introduction
Non-vaccinated groups
! inoculated lambs: all infectious after inoculation
! contact lambs: two groups two, one group one and three groups none infected
Vaccinated groups
! inoculated lambs: four groups two, two groups one infectious after inoculation
! contact lambs: none infected
! Quantified transmission parameters of FMDV are needed for epidemic models
used for control and surveillance.
! For sheep, limited quantified information on transmission of FMDV available
while especially in sheep an FMDV
infection can remain unnoticed and
thus an infection with FMDV can
spread in the meantime.
Virus isolation of OPF samples: Table 1
Transmission parameters: Table 2
Table 2: Estimates of transmission parameters in FMDV (Asia-1) infected groups of lambs,
as estimated using the daily data of the virus isolation of oropharyngeal swab samples and
the final size method
Groups
Non-vaccinated
Vaccinated -14dpi
Transmission rate (day-1) Infectious period (days) Reproduction ratio Reproduction ratio (final size)
beta
95%CI
T
95%CI
R
95%CI
R
95%CI
0.07
0.03-0.17
52
22- 125
3.8
0.66-22
1.14
0.3-3.3
n.a .
n.a.
32
13- 76
n.a .
n.a.
0
0-0.8
Materials and Methods
Quantification of transmission of FMDV strain Asia-1 Turkey in lambs
Transmission experiment using an SIR model
12 groups of four lambs (2 inoculated + 2 contacts)
! six groups non-vaccinated
! six groups vaccinated (FMDV Asia-1 Shamir) at two weeks before inoculation
Inoculation with FMDV Asia-1 Turkey 11/2000
Oropharyngeal swabs collected daily until 21dpi
Quantified transmission parameters:
! Reproduction ratio R with final size (total number of contact infections) and
results of ß and T
! Infectious period T (survival analysis, using virus isolation results of OPF)
! Transmission rate ß (GLM, using virus isolation results of OPF)
Conclusions
! R (final size) in non-vaccinated lambs infected with FMDV Asia-1 Turkey
11/2000 is close to 1 which means that mostly minor outbreaks can
be expected.
! Vaccination with a commonly used Asia-1 Shamir strain reduced R significantly,
which confirms the potential of vaccination as important intervention tool
during an outbreak.
! The expected duration of virus shedding of the infectious non-vaccinated and
vaccinated lambs is long. Whether or not this is strain dependent remains to
be investigated.
Table 1: Results of virus isolation of OPF swabs
Vaccinated group
Non-vaccinated group
C
C
I
I
0
-
1
3.1
2
2.9
3.8
3
4.0
2.3
4
2.8
1.8
5
0.7
2.1
1.9
6
b
1.9
1.6
7
2.4
-
8
1.9
-
days post inoculation
9
10
11
12
0.7
1.6
1.2
0.9
1.0
C
C
I
I
-
2.9
2.3
2.1
3.4
2.0
2.7
2.3
1.9
1.9
2.6
2.0
3.0
2.7
2.9
2.3
2.5
2.8
2.9
1.9
1.4
3.1
2.7
1.8
1.0
1.2
1.2
0.9
0.4
1.1
1.9
2.2
0.4
2.1
2.1
2.2
1.7
2.2
2.4
2.0
1.9
0.7
2.0
1.6
1.5
0.7
2.3
2.6
1.7
1.8
2.0
2.1
2.1
1.8
0.7
1.8
1.9
1.9
1.2
1.9
2.1
1.0
1.9
2.3
1.7
1.7
1.5
+
+
+
+
C
C
I
I
-
2.5
-
2.3
2.4
1.8
1.4
1.2
-
1.4
1.4
-
C
C
I
I
-
0.4
2.4
3.2
3.2
3.5
2.1
3.8
2.3
3.5
2.2
2.0
2.2
1.2
2.2
1.6
2.4
1.9
1.9
0.9
2.1
2.1
2.1
2.5
2.1
2.7
2.7
2.8
1.9
2.2
1.7
3.2
2.3
2.4
2.1
2.1
1.9
2.2
1.7
0.4
-
1.2
1.1
+
+
C
C
I
I
-
2.3
1.9
2.9
3.0
1.4
1.8
1.8
1.5
2.7
1.4
C
C
I
I
-
2.7
2.0
4.1
2.2
3.6
2.5
2.0
2.2
2.2
2.1
2.3
1.7
3.0
1.0
3.7
1.5
2.9
1.0
-
2.1
-
1.9
1.7
0.4
1.5
0.7
1.4
1.4
2.2
1.1
1.8
1.2
1.8
0.4
1.8
0.9
1.9
1.9
0.4
0.7
2.3
1.0
1.4
+
+
+
C
C
I
I
-
1.6
1.9
0.4
-
2.2
1.8
2.2
1.9
0.4
1.9
2.1
2.1
-
0.9
-
1.4
-
C
C
I
I
-
4.0
2.4
5.0
-
2.8
-
2.0
-
2.0
-
1.8
1.9
1.8
1.7
2.2
-
2.2
-
-
1.9
-
3.0
-
2.2
-
2.2
-
2.0
-
2.6
-
2.2
-
1.7
-
2.2
-
2.1
-
1.7
-
+
+
C
C
I
I
-
2.1
-
-
2.1
3.8
2.1
4.5
1.2
0.7
-
1.1
2.2
0.7
C
C
I
I
-
2.2
3.2
1.4
3.5
2.2
3.0
2.4
1.4
1.9
2.3
0.4
-
1.7
0.9
-
-
1.9
0.9
0.4
1.7
0.7
2.4
-
0.7
0.4
+
+
C
C
I
I
-
0.9
2.0
1.2
2.1
1.8
-
2.0
2.9
2.4
1.7
1.9
1.9
2.8
2.1
2.2
1.5
a
a
13
2.1
2.2
14
2.1
1.7
15
1.6
2.2
16
1.2
1.2
17
2.0
1.4
18
1.8
0.4
19
1.7
2.0
20
0.7
21
0.7
0.9
Infected
+
+
+
+
C
C
I
I
0
-
1
2.1
2.2
2
3.1
3
2.7
4
1.2
5
-
6
-
7
-
8
-
9
-
days post inoculation
10
11
12
0.7
-
13
1.9
14
1.9
15
1.5
16
1.5
17
1.3
18
1.2
19
0.9
20
0.4
21
0.9
Infected
+
+
2.2
0.7
2.2
-
1.4
-
1.0
1.0
-
1.2
+
2.2
>
2.0
1.8
1.5
1.4
1.3
1.7
-
-
-
+
-
-
1.4
-
1.9
-
2.1
-
1.4
-
1.9
-
-
1.6
-
1.2
-
0.4
-
0.9
-
+
+
1.7
1.8
1.7
1.0
2.2
2.6
0.7
1.4
1.9
2.1
2.1
1.4
2.0
-
-
-
+
+
2.3
1.2
2.2
1.9
1.9
0.9
2.1
2.1
2.2
1.6
1.2
1.6
1.2
0.4
1.5
-
2.1
1.0
1.0
0.7
1.4
1.2
-
0.9
1.3
+
+
contact or inoculated lamb
log titre of VI of OPF samples, -: no virus was detected, the period that was considered as infectious is marked in grey
b 10
Acknowledgements
The authors wish to thank the laboratory assistants and staff of the animal isolation unit that participated in the described research for their assistance. This work was supported financially
by the European Union (FMD ImproCon SSPE-CT-2003-503603, EPIZONE NoE FOOD-CT-2006-016236) and the Ministry of Agriculture, Nature and Food Quality of The Netherlands.
1
Central Veterinary Institute of Wageningen UR (CVI),
Laboratory Vesicular Diseases, Department of Mammalian Virology
P.O. Box 65, 8200 AB Lelystad, The Netherlands
tel: +31 320 238680
e-mail: [email protected]
elbe1 05-2008
2
Faculty of Veterinary Medicine,
University of Calgary
3330 Hospital Drive NW, Calgary,
Alberta, T2N 4N1
Canada