Implementation of a vaccine against Shigatoxin 2e in a piglet producing farm with problems of Oedema disease: case study

Case history

A 600 sow farm (breed: Topigs) in the Netherlands had massive problems with ED in
the nursery for over a year. The farm is a single site facility with the farrowing
barn separated from the nursery. The farrowing rhythm is one-week. Cross fostering
is carried out until the age of 3 days but is kept to a minimum in order to avoid
the transmission of Streptococcus suis. Sows are vaccinated against Parvovirus, Swine Erysipelas, Swine Influenza and Colibacillosis
in neonatal piglets. Weaning takes place at an age of 25–26 days when the piglets
weigh approximately 7.5 kg. After weaning, the piglets are transferred to the nursery.
The nursery is run all in – all out by compartment. Each age group has one compartment
and age groups are not mixed. Space and feeding requirements are met according to
law. Water is supplied via drinking nipples ad libitum. Nursery period ends at the
age of 11 – 11.5 weeks.

Within the period between 01.10.2011 and 30.09.2012 the mortality in the nursery was
at 7.7% with a confirmed mortality due to ED of 5.9%. Implemented measures like low
crude protein content of 160 g/kg in the feed as well as the metaphylactic treatment
of each weaned week group with Colistin sulphate for the first 10 days in nursery
did not have any valuable impact on reduction of mortality. The diagnosis of ED had
been made based on the clinical examination of affected piglets as well as the results
of necropsies and microbiological analysis.

Study description

For the study a total of 17977 piglets were included and vaccinated within the period
from 02.10.2012 to 24.09.2013. Inclusion criteria were: a weight of more than 800
grams, no clinical signs of an illness and the clear assignment to a specific sow.
Piglets that did not meet these criteria were not vaccinated and the number of their
respective ear tags was registered.

The piglets were vaccinated intramuscularly at the base of the ear with a dose of
one millilitre containing a genetically modified and recombinantly produced Stx2e
(trade name ECOPORC SHIGA) at the average age of four days. One dose of the vaccine
(1 ml) contains???3.2 × 106 ELISA units of recombinant Stx2e. The adjuvant is aluminium
hydroxide. At the same time, the piglets were ear tagged with different coloured tags
for each week group, as well as being injected with iron (other side of the neck),
the tails were docked and male piglets were castrated.

Every day during the nursery period, the farmer observed whether the piglets showed
any clinical signs of ED (Oedema of the eyelids and subcutis of the face; nervous
disorders like ataxia, paralysis of limbs, tonic-clonic convulsions) and controlled
the general appearance of the piglets. When piglets showed signs of illness, a clinical
diagnosis was made whether or not the occurring clinical symptoms were related to
Oedema disease. In case of losses for which the farmer was not able to define a reason
these piglets were sent for pathological examination to examine the definite cause
of death. This included special investigations concerning the appearance of Oedema
disease, like PCR-testing of the isolated E. coli strains regarding factors of pathogenicity and histopathological examination of e.g.
the brain. In order to assure the presence of EDEC despite vaccination rectal swabs
were taken from vaccinated 7 weeks old animals by the herd attending veterinarian
at the end of the study. No changes were made regarding the content of crude protein
in the feed during the study in order to maintain equality of the requirements for
comparison.

Observed and compared data were the Overall mortality (expressed as the mean percentage
of all dead piglets during nursery period per weaned piglets on monthly basis without
regard to the reason of death), the metaphylactic use of colistin sulphate (defined
as DDD animal colistin sulphate/month) and the general use of antimicrobials (defined
as Mean DDD animal/month) within the period of one year prior to vaccination and one
year with vaccination. Additionally, the mean body weight at sale of the total of
pigs sold in the defined period was calculated via software (Pigmanager) and compared
to the previous period with unvaccinated animals. The vaccination was performed by
the herd attending veterinarian. The observations and recording of the data were carried
out by the farmer, following training in the study protocol and was supervised by
the herd attending veterinarian. Statistical analyses were performed by SPSS 15.0
for Windows (SPSS Inc., Chicago, Illinois, USA). Analyses performed included the Mann–Whitney-U-test.

Ethical approval for this study was granted by our company IDT, in line with requirements
in Germany for studies involving animals. The proper authorities in the Netherlands
were also notified prior to the start of the study, and granted all required approvals.

Results

The mean Overall mortality of 7.7% prior to vaccination was significantly reduced
to 1.3% after vaccination (p??0.001, Mann–Whitney-U-test, two-tailed, asymptotic,
see Table 1).

Table 1. Overall mortality during nursery period

One piglet of the 11^th vaccination group was classified as “death due to Oedema disease”, but only by default.
When this piglet died, it was failed to be submitted to necropsy and subsequent analysis.
Thus because the cause of death could not be determined, it was decided to classify
its death as due to Oedema disease. In two animals clinical signs associated with
ED (recumbence with tonic-clonic convulsions) were observed after weaning. After the
piglets had died pathological examinations as well as microbiological analyses were
carried out. Streptococcus suis was determined to be the cause of the clinical signs. The analysis for Stx2e producing
E. coli of rectal swabs taken from 7 weeks old pigs at the end of the study showed that the
pathogen was still present on the farm despite vaccination.

The metaphylactic use of colistin sulphate was stopped after the 9^th weaned group of vaccinated animals, because until then no more deaths due to ED had
occurred. It was not implemented anymore during the study period. The defined daily
dose per animal (Mean DDD animal/month) for all antimicrobials was reduced from a
mean of 1.050 in the year 2012 to a mean of 0.215 in the year 2013 (p??0.001, Mann–Whitney-U-test,
two-tailed, asymptotic, see Table 2).

Table 2. Defined daily dose per animal (DDDanimal) per month

The sum of the Mean DDD animal/month for the year 2012 was 12.6. This was reduced
to 2.6 for the year 2013. The mean body weight of the sold groups was higher after
vaccination (25.252 kg vs. 25.618 kg respectively), but this difference was not statistically
significant.