Prevention of Oedema Disease in Weaned Piglets by Vaccination

Starek M., G. Bi lkei : Prevention of Ooedema Disease in Weaned Piglets by Vaccination. Acta Vet. Brno 2004, 73: 225-227. In order to prove the effect of vaccination against postweaning oedema disease, a trial was performed in a large Croatian pig production unit, with high prevalence of postweaning oedema disease. The trial animals were either vaccinated (group one, n = 275) with a VT2e-toxoid vaccine at 1 week of age (with 12.5 μg inactivated VT2e toxin per pig), and at 3 weeks of age (with 25 μg inactivated VT2e toxin), or were placebo treated (group two, n = 274). Postweaning performance of piglets and serological status against VT2e toxin were evaluated. Vaccination significantly (p < 0.05) affected nursery weight gains (group 1: 302 ± 32 g; group 2: 276 ± 42 g). Mortality revealed significant (p < 0.01) differences between the vaccinated (group 1: 0.5%) and non-vaccinated pigs (group 2: 7.9%); fattening weight gain did not differ significantly (p > 0.05) between the groups (group 1:741 ± 42 g vs. group 2: 706 ± 44 g). There was a significant rise of serological OD values due to vaccination in the vaccinated animals (p < 0.01). Swine, Escherichia coli, weaning, mortality, weight gain Weaning has been recognised as one of the most stressful challenges of the piglet’s life (Shanks 1938). Postweaning Escherichia (E.) colicaused problems can be subcategorised into postweaning diarrhoea (PWD), oedema disease (ED), postweaning wasting (PWW) and haemorrhagic gastroenteritis (HGE) (Bölcskei et al. 1995). Ooedema disease has often been caused by haemolytic F18 pilus positive E. coli O139 that produce verotoxin 2e (VT2e, Moon et al. 1999). Verotoxigenic E. coli colonise the intestine via F18 pilus (Wilson and Francis 1986). A VT2e-toxoid vaccine was found to be effective against ED (Awad Masalmeh et al. 1989). The objective of the present study was to determine the effect of a VT2e–toxoid vaccine against ED under field conditions. Materials and Methods A trial was performed in the large Croatian pig production unit, with high losses due to postweaning ED. E. coli were serotyped for O139 by slide-agglutination tests in Vet Invest Zagreb (Croatia). Analysis of the isolates was performed in Vet Invest Zagreb (Croatia) by multiplex PCR assay for detecting genes for Shiga-like toxin type ll and fimbrial adhesins F18 ab, ac according to Bosworth and Casey (1997). Amplified products were electrophoresed in 2% agarose gel, stained with ethidium bromide, and examined under ultraviolet illumination. DNA fragment lengths were verified by a digested £-DNA standard run simultaneously. Control for DNA reference strains was included in each reaction. Test sensitivity (Se) was 95.2%; specificity (Sp) 90.5%. Seropositivity was monitored by an indirect ELISA that was used to detect specific anti-VT2e antibodies in serum obtained every sampling time from the same animals (30 pigs [identified by ear tags] in each group). VT2e-toxoid in pH 9.0 carbonate puffer was applied directly to ELISA plates at 4 °C overnight. The plates were incubated with 0.05% Tween 20, 1% bovine serum albumin in PSB-T-BSA for 1 hour. Serum samples were applied in 1:200 dilutions in PSB. Antibodies were detected with peroxidase-conjugated rabbit anti-swine immunoglobulins in PSB-T-BSA. Further processing took place according to Johansen et al. (1997). Colour was allowed to develop for 20 min. Optical density (OD) was measured at 490 nm minus 650 nm by dual wavelength endpoints. The effect of vaccination on the serum level of VT2e-specific antibodies was assessed by the rise in optical density (OD) values. An experimental toxoid vaccine was produced as described by MacLeod and Gyles (1991) and Johansen et al. (1997). ACTA VET. BRNO 2004, 73: 225-227 Address for correspondence: PhD. Dr. med. vet. G. Bilkei Bilkei Consulting Raubbühlstrasse 4 CH-8600 Dübendorf Switzerland Phone: + 41 1 820 02 26 E-mail:bilkei.consulting@gmx.com http://www.vfu.cz/acta-vet/actavet.htm

Weaning has been recognised as one of the most stressful challenges of the piglet's life (Shanks 1938).Postweaning Escherichia (E.) coli-caused problems can be subcategorised into postweaning diarrhoea (PWD), oedema disease (ED), postweaning wasting (PWW) and haemorrhagic gastroenteritis (HGE) (Bölcskei et al. 1995).Ooedema disease has often been caused by haemolytic F18 pilus positive E. coli O139 that produce verotoxin 2e (VT2e, Moon et al. 1999).Verotoxigenic E. coli colonise the intestine via F18 pilus (Wilson and Francis 1986).A VT2e-toxoid vaccine was found to be effective against ED (Awad Masalmeh et al. 1989).The objective of the present study was to determine the effect of a VT2e-toxoid vaccine against ED under field conditions.

Materials and Methods
A trial was performed in the large Croatian pig production unit, with high losses due to postweaning ED.E. coli were serotyped for O139 by slide-agglutination tests in Vet Invest Zagreb (Croatia).Analysis of the isolates was performed in Vet Invest Zagreb (Croatia) by multiplex PCR assay for detecting genes for Shiga-like toxin type ll and fimbrial adhesins F18 ab, ac according to Bosworth and Casey (1997).Amplified products were electrophoresed in 2% agarose gel, stained with ethidium bromide, and examined under ultraviolet illumination.DNA fragment lengths were verified by a digested £-DNA standard run simultaneously.Control for DNA reference strains was included in each reaction.Test sensitivity (Se) was 95.2%; specificity (Sp) 90.5%.Seropositivity was monitored by an indirect ELISA that was used to detect specific anti-VT2e antibodies in serum obtained every sampling time from the same animals (30 pigs [identified by ear tags] in each group).VT2e-toxoid in pH 9.0 carbonate puffer was applied directly to ELISA plates at 4 °C overnight.The plates were incubated with 0.05% Tween 20, 1% bovine serum albumin in PSB-T-BSA for 1 hour.Serum samples were applied in 1:200 dilutions in PSB.Antibodies were detected with peroxidase-conjugated rabbit anti-swine immunoglobulins in PSB-T-BSA.Further processing took place according to Johansen et al. (1997).Colour was allowed to develop for 20 min.Optical density (OD) was measured at 490 nm minus 650 nm by dual wavelength endpoints.The effect of vaccination on the serum level of VT2e-specific antibodies was assessed by the rise in optical density (OD) values.An experimental toxoid vaccine was produced as described by MacLeod and Gyles (1991) and Johansen et al. (1997).
Group 1, G1 (n = 275) piglets were intramuscularly vaccinated at 1 week of age with 12.5 µg and at 3 weeks of age with 25 µg of inactivated VT2e toxin.
GLMM (general linear mathematical model) and REML (reference manual) procedures of the statistical package of Genstat 5, Oxford, Clarendon and Fisher´s exact test were used to analyse data.For time aspects (such as the exact age of the piglets at the time of vaccination) and proportion of piglets dying for ED a logistic regression model was used.For ADG from weaning to the end of the nursery period a linear regression model was used.The effect of the sow (and the interaction between treatment and sow) and the effect of initial weight were included as random components, but had no significant influence on nursery weight gain (NADG), mortality due to ED (EDNM) and fattening weight gain (FADG).Weight gain in the finisher period was analysed by the model including weight at last weighing, treatment effect, age of the animal, the effect of age and the effect of weight at weaning, and the effect of group.The change in OD-values from first vaccination to the end of the nursery period was analysed by paired t-test.

Results and Discussion
Vaccination significantly (P < 0.05) affected NADG (G1: 302 ± 32 g; G2: 276 ± 42 g); mortality revealed significant (P < 0.01) differences between the vaccinated (G1: 0.5%) and non-vaccinated pigs (G2: 7.9%); FADG did not differ significantly (p > 0.05) between the groups (G1:741 ± 42 g vs. G2: 706 ± 44 g) (Table 1).There was a significant rise of serological OD values due to vaccination in G1 (p < 0.01) (Table 2).The control pigs seropositivity shows the infectious pressure due to VT2e bearing E. coli in this unit.There was no effect of vaccination on growth performance in the fattening period.This indicates that pigs whose growth rates are suppressed during the postweaning period are able to recover and gain satisfactorily during the fattening period.
In the present study we decided to define "death caused by oedema disease" only cases with growth of heamolytic E. coli O139 bearing pilus F18 and revealing the for ED typical gross pathological changes.The present results are consistent with the findings of Awad M asalmeh et al. (1988), Bosworth et al. (1996), Johansen et al. (1997), andK e n andBilkei (2003) and indicate that vaccination with purified VT2e-toxoid can successfully prevent ED caused piglet losses under field conditions in weaned pigs.