Abstract Book of EAVLD2012 - eavld congress 2012

S1 - P - 33
APPLICATION OF A HERD PROGRAMME BASED ON CONTROL MEASURES AND LABORATORY
MONITORING TO ERADICATE A LEPTOSPIRA OUTBREAK IN A LARGE DAIRY CATTLE HERD
M.T. Scicluna, G. Manna, F. Rosone, A. Caprioli, R. Frontoso, , G.L. Autorino
Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana, 00178 Roma Italia
Leptospira serovar hardjo, management, laboratory diagnosis
Introduction
In Italy, the application of severe sanitary measures, including
animal movement restriction are mandatory on the diagnosis of
Leptospira infection and are lifted only after the removal of all
seropositive animals. In the attempt of reducing economic losses
deriving from these actions, a herd control programme was
applied in a dairy intensive farm, in which the infection had been
diagnosed, based on the combination of preventive, treatment
and biosecurity measures, aiming at the sterilization of carriers
and prevention of new cases of infection (1,2,3,4). The primary
objective was to accelerate the control/eradication of the infection
which was evaluated by monitoring the absence of its circulation
with the aid of serological and molecular techniques and not as
requested by the Italian Regulation, through the sole removal of
the seropositive animals. Following is the description of the
supplementary measures adopted and the actions applied for the
assessment of the efficacy of the control protocol.
Materials & methods
Following the notification of leptospira diagnosis, an extensive
serological investigation was undertaken in the farm of 600
producing cows, to verify if the infection was actively circulating:
the random sampling scheme (Table 1) adopted, allowed the
estimation of a prevalence of at least 50%, with a standard error
of 10% and a confidence interval of 95%. The serological method
used was the microagglutination test (MAT) described in the OIE
manual, employing the serovar hardjo. A sample was considered
positive when presenting a titre > to 1/100 (6).
The supplementary control plan applied on the farm was based
on the following points:
- preventive measures, based on vaccination to limit new cases
contributing to the further spread of leptospirosis. The vaccine
employed, produced by the Istituto Zooprofillatico Sperimentale
of Umbria and Marche, contained serovar hardjo and was
administered as prescribed to all animals.
- antibiotic treatment was adopted to sterilize carrier animals and
eliminate primary source of infection. Two different antibiotics
were chosen for economical and management reasons. (1,6) The
more economical, Penistrep ®, 25mg/kg b.w., was for 3
consecutive days used in animals managed individually. To avoid
any impact of treatment on the sale of milk, antibiotics were
administered when the producing animals were dried off.
Treatment was conducted so as to ensure that all animals of the
same group received it all together, to avoid infection of
seronegative subjects, after the disappearance of the effect of
treatment. These animals received a single dose of 20 mg/kg
b.w., of Duphaciclina 300 LA®.
- Biosecurity measures aimed at further limiting the presence of
leptospira in the environment, consisted in: isolation of the
different units and their drinking systems in relation to whether
these had undergone antibiotic treatment and complete
vaccination; exclusive use of artificial insemination; systematic
draining of paddocks to avoid water and urine stagnation;
confinement, feeding and milking last of untreated animals.
On conclusion of the control plan, actions were set up to verify its
efficacy. These consisted in the microbiological examination of
272 urine samples of the animals in the different productive units,
using the same sampling scheme described for the
serosurveillance. These were examined in a SYBR Green Real
Time PCR, specific for pathogenic Leptospira (7). Advantage of
this test is that it can identify the carrier state even in a
serologically positive animal and compared to the microbiological
isolation, is fast and highly specific. Although reaction inhibition
could occur due to the type of sample, using the test at herd
level, increases the sensitivity of the method.
In addition, a serological control was carried out on 50 animals
born after the conclusion of the programme, used also as
seronegative sentinels, placed in the productive units for the
detection of an active circulation. The number of sentinel animals
examined aimed to reveal an infection prevalence of 5% (IC
95%). These animals were retested at the end of their in-contact
period, of two months, ensuring exposure, incubation period and
also the production of a detectable serological response.
Results & discussion
The results of the serosurvey (table 1) demonstrate that
leptospira infection was actively circulating in the farm. The
supplementary measures adopted were considered as successful
on the basis of the interruption of the leptospira infection in the
different production units, as indicated by the negative results
obtained for the urine samples and the seronegativity of the
sentinels after their in-contact period with serological positive
animals. Further evidence of the efficiency of the control
programme was also the seronegativity of all animals born after
the conclusion of the adoption of these measures.
The adoption of such a herd control programme would be of
benefit for both the farmers as well as the Veterinary Authorities,
in that they would have more instruments for the control of this
infection.
Table 1. Sample scheme for serological survey.
Productive Consistency Examined Positive N° of
Unit
(positive)
animals
(Titres)
Heifers 60 34 (5) 5 1(1/100)
1(1/200)
3(1/400)
Pregnant
Heifers
160 54 (38) 38 27 (1/100)
3(1/400)
8(1/200)
Dry cows 140 51 (37) 37 29(1/100) 73
8(1/200)
Primipare 120 48 (26) 26 26 (1/100) 54
Pluripare 160 60 (35) 35 34(1/100) 58
1(1/200)
Fresh 50 33 (12) 12 10(1/100) 36
Lactating
cows
2(1/200)
Problem 80 44 (25) 25 25 (1/100) 57
animals
Sick bay 20 17 (7) 7 7 (1/100) 41
References
1. Bolin CA, Alt DP. 2001. Am J Vet Res. 62(7):995-1000
2. Cortese VS, et al., 2007. Vet Ther. 8(3):201-8
3. Little TW, et al., 1992. Vet Rec. 1;131(5):90-2
4. Little TW, et al., 1992. Vet Rec. 24;131(17):383-6
5. Levett PN Clin. Microbiol. Rev. 2001 Apr.,: 296–32
6. Alt DP, et al.,2001.J Am Vet Med Assoc.1;219(5):636-9
7. Ahmed A, et. al. 2009. PLoS One 4: Vol 4, Issue 9:1-8
Estimted
prevalence %
15
70