The bulk milk represents a cost effective matrix to monitor the serological status of the infection within dairy herds (Reber et al. 2012). Many infectious diseases, such as Bovine Infectious Rhinotracheitis (IBR), are object of voluntary or compulsory eradication programmes based on the individual serological test of receptive animals (2004/558/CE). When a marker vaccination is in place, the possibility to monitor the seroconversion in milk samples, requires a gE ELISA able to detect specific antibodies with an appropriate sensitivity and specificity (Van Oirschot J.T, 1999). Despite the low level of IgG in bulk milk samples as well as the reduced sensitivity of gE blocking ELISA applied to this matrix (Schroeder et al. 2012), a new diagnostic tool is now available. Eradikit® Bulk Milk Surveillance Kit plus (Eradikit®BMSK plus, In3diagnostic Italy) consisting in a sequential precipitation of IgG and others milk proteins, followed by a gE indirect ELISA, seems a promising tool for IBR surveillance of vaccinated herds. In this study the method was applied in a heterogeneous sample set of dairy herds (297) of Cuneo province, in comparison with the individual serum assay. Individual milk samples were collected from 70,000 lactating cows by the breeders association (APA) and used, before milk parameters determination, to make pooled milk of a sample size up to 40 animals. Each pooled milk was subjected to sequential precipitations according to the user protocol and the final enriched fractions were tested in gE indirect ELISA. In three different test sessions (2200 pools), 140 classified positive farms and 157 recognized gE negative herds were monitored over twelve months, calculating the field sensitivity of the method. All farms classified as gE negative by the official gE LXX Convegno S.I.S.Vet. XVI Convegno S.I.C.V. - XIV Convegno S.I.R.A. XIII Convegno A.I.P.Vet. - XIII Giornata studio So.Fi.Vet. - III Convegno R.N.I.V. blocking ELISA scored negative to Eradikit® Bulk Milk Surveillance Kit plus (specificity: 100%, 95%CI: 97.7%-100%). In a single herd a recent viral circulation was demonstrated by the gE blocking ELISA in individual serum assay, confirming the bulk milk results . This result support the use of the bulk milk for the early detection of viral circulation. Among the positive farms enrolled in this study, all but 2 with a herd-prevalence higher than 2.5% were tested as positive, while under the 2.5 % the positive farms remained negative. The field sensitivity of the method seems adequate for surveillance purposes in gE negative farms and suitable to detect viral circulation at prevalence level higher than 2.5%. Since data about the identification tag of lactating cows are available, this information will be used in order to evaluate the infection prevalence in the milk pool and, consequently, the diagnostic sensitivity of the method. In case of a seroprevalence lower than 2.5% or in presence of old whole-virus vaccinated cows, Eradikit® BMSK-plus could be used for eradication purposes reducing the pool sizes to detect a weak positive sample diluted in negative milks.

Evaluation of a new diagnostic tool for IBR surveillance in dairy herds: a field study in Cuneo province

MURATORE, ELVIRA;COLITTI, BARBARA;IOTTI, BRYAN;NOGAROL, Chiara;BERTOLOTTI, Luigi;PROFITI, Margherita;ROSATI, Sergio
2016-01-01

Abstract

The bulk milk represents a cost effective matrix to monitor the serological status of the infection within dairy herds (Reber et al. 2012). Many infectious diseases, such as Bovine Infectious Rhinotracheitis (IBR), are object of voluntary or compulsory eradication programmes based on the individual serological test of receptive animals (2004/558/CE). When a marker vaccination is in place, the possibility to monitor the seroconversion in milk samples, requires a gE ELISA able to detect specific antibodies with an appropriate sensitivity and specificity (Van Oirschot J.T, 1999). Despite the low level of IgG in bulk milk samples as well as the reduced sensitivity of gE blocking ELISA applied to this matrix (Schroeder et al. 2012), a new diagnostic tool is now available. Eradikit® Bulk Milk Surveillance Kit plus (Eradikit®BMSK plus, In3diagnostic Italy) consisting in a sequential precipitation of IgG and others milk proteins, followed by a gE indirect ELISA, seems a promising tool for IBR surveillance of vaccinated herds. In this study the method was applied in a heterogeneous sample set of dairy herds (297) of Cuneo province, in comparison with the individual serum assay. Individual milk samples were collected from 70,000 lactating cows by the breeders association (APA) and used, before milk parameters determination, to make pooled milk of a sample size up to 40 animals. Each pooled milk was subjected to sequential precipitations according to the user protocol and the final enriched fractions were tested in gE indirect ELISA. In three different test sessions (2200 pools), 140 classified positive farms and 157 recognized gE negative herds were monitored over twelve months, calculating the field sensitivity of the method. All farms classified as gE negative by the official gE LXX Convegno S.I.S.Vet. XVI Convegno S.I.C.V. - XIV Convegno S.I.R.A. XIII Convegno A.I.P.Vet. - XIII Giornata studio So.Fi.Vet. - III Convegno R.N.I.V. blocking ELISA scored negative to Eradikit® Bulk Milk Surveillance Kit plus (specificity: 100%, 95%CI: 97.7%-100%). In a single herd a recent viral circulation was demonstrated by the gE blocking ELISA in individual serum assay, confirming the bulk milk results . This result support the use of the bulk milk for the early detection of viral circulation. Among the positive farms enrolled in this study, all but 2 with a herd-prevalence higher than 2.5% were tested as positive, while under the 2.5 % the positive farms remained negative. The field sensitivity of the method seems adequate for surveillance purposes in gE negative farms and suitable to detect viral circulation at prevalence level higher than 2.5%. Since data about the identification tag of lactating cows are available, this information will be used in order to evaluate the infection prevalence in the milk pool and, consequently, the diagnostic sensitivity of the method. In case of a seroprevalence lower than 2.5% or in presence of old whole-virus vaccinated cows, Eradikit® BMSK-plus could be used for eradication purposes reducing the pool sizes to detect a weak positive sample diluted in negative milks.
LXX Congresso Nazionale SisVet
Università degli studi di Palermo
13-16 giugno 2016
ATTI LXX Congresso Nazionale SisVet
Safood s.r.l
309
310
978-88-909092-8-3
IBR, gE ELISA, pooled milk
Muratore, Elvira; Barbara, Colitti; Iotti, Bryan; Careddu, Maria Elena; Nogarol, Chiara; Bertolotti, Luigi; Profiti, Margherita; Ponzo, Andreino; Facelli, Roberto; Rosati, Sergio
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/1625078
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