SAFETY OF A BIVALENT BTV-4/BTV-8 INACTIVATED VACCINE IN PREGNANT AND LACTATING CATTLE

Galleau S.1 - Hamers C.1 – Blosse A.1 – Bolon A. 2Blanchet M.1 - Duboeuf M.1 – Goutebroze S.1

1 Merial S.A.S. – 69007 Lyon, France2 Independent Investigator, c/o MERIAL

IntroductionBluetongue (BT) is an infectious OIE listed disease of wild and domestic ruminants. Recent Bluetongue virus serotype 8 (BTV-8) outbreaks in Northern Europe have seriously affected cattle and sheep industries. To control BT epizooty, several countries have implemented large-scale compulsory vaccination campaigns in ruminant populations, including a large number of pregnant and/or lactating animals. The present study assessed the safety of an overdosed vaccine from the BTVPUR ALSAP® range (Merial S.A.S) administered to pregnant dairy cows, through monitoring of reproductive performances and milk production in field conditions.

® : BTVPUR ALSAP is a registered trademark of Merial in the European Union and Elsewhere.

This product can be used ONLY under governmental direction.

Material & Methods

Study design:

Field study conducted in a BTV-free dairy farm located in the French Prealps (department of Ain).

Inclusion of 96 pregnant dairy cows allocated to 2 groups according to their age and their pregnancy stage:

G1 (n=48) : vaccinated twice at a 4-week interval (D0/D28) with a BTV-4 / BTV-8 inactivated and overformulated vaccine (1 mL; SC route)

G0 (n=48) : controls injected with placebo (physiological saline) in the same conditions as for G1

Monitoring:

Animals were monitored by the farmers (blinded procedure) as follows:

- Individual clinical observation and daily recording of rectal temperature during 4 days following each injection

- Monitoring of pregnancy and health status of the offsprings until 15 days of age

- Recording of the monthly milk yield (official milk production control) before vaccination and during the 4 subsequent months

ConclusionThe results of the study demonstrated the safety in pregnant and lactating cows of the administration of an overformulated BTV-4 /BTV-8 inactivated vaccine through:

• a very limited and transient temperature increase following the first vaccine injection,• an absence of treatment-related general reaction,• an absence of impairment of the reproductive performance whatever the stage of pregnancy,• an absence of impairment of the milk production in lactating cows.

Results

Clinical monitoring

No treatment-related general reaction was observed after each vaccination.

After the first injection, vaccinates presented a slightly higher rectal temperature than controls (+0.4°C in G1 vs +0.2°C in G0; p=0.042, Student t-test).

After the second injection, no difference between the treatment groups was observed (p=0.534, Student t-test).

Figure 1 : Evolution of mean rectal temperature following each injection

Calving data

The number of calvings and abortions/stillbirth were similar between the treatment groups whatever the stage (trimester) of pregnancy at first vaccination. In both groups, causes of abortion could not be evidenced.

Among the born alive calves, few deaths occurred before 15 days of age (4 in G0 and 3 in G1) but none was related to the treatment.

In total, the number of cows which delivered a live calf were identical in the two treatment groups (p=0.714, Fisher’s exact test).

Figure 2 : Number of gestation fulfilled and abortions/stillbirth, according to the pregnancy stage at first injection

Milk yield

The 2 treatment groups were homogeneous for their stage of lactation. The milk yield was equivalent in both treatment groups before vaccination (March; p=0.849, Mann-Whitney W test) and during the 4 subsequent months (Sum April-July; p=0.673, Student t-test) .

Figure 3 : Monthly milk yield recorded before vaccination (March) and during the 4 subsequent months (April-July).

38.2

38.4

38.6

38.8

D0 D1 D2 D3 D4 D28 D29 D30 D31 D32

Day of protocol

Mean r

ect

al te

mpera

ture

(°C

)

G0 (placebo)

G1 (vaccinates)

First injection

Second injection

15

19

8

15

18

9

3

0 0

4

1

00

2

4

6

8

10

12

14

16

18

20

First injection during the 1sttrimester o f pregnancy

First injection during the 2ndtrimester o f pregnancy

First injection during the 3rdtrimester of pregnancy

No.

of

cow

s

Abortions in G1 (vaccinates)

Pregancy fulfilled in G0 (placebo)

Pregancy fulfilled in G1 (vaccinates)

Abortions in G0 (placebo)

MarchApril

MayJune

July

0

5

10

15

20

25

30

Milk

yie

ld (

kg)

G1 (vaccinates)

G0 (placebo)2 nd1 st

2 nd

1 st