FMD Vaccination of Pig Breeders Designed to Give Newborn Piglets Adequate Immunity After Birth

Abstract

Recurrent incursions of Foot and Mouth Disease (FMD) strains cause several outbreaks in Israel on yearly basis, almost all of them occurring in ruminants; however, in 2015 and 2022 pig farms were also involved and Type O strain was confirmed in the outbreaks. Vaccination against FMD is compulsory for pigs in Israel, but only in breeders as routine vaccination. Furthermore, only a single vaccination per year is performed. The 2022 outbreak presented the occasion to verify if a single vaccination/year/breeder may be considered protective against FMD. Vaccinated sows and their suckling piglets were serologically tested on the eve of the outbreak and 5 months later. Results indicated that breeders vaccinated once a year only, presented with low/non-protective immunity against FMD virus on the eve of the outbreak. Furthermore, a single booster vaccination in course of outbreak, but much overdue from the last routine vaccination, also did not induce a protective immunity in sows. Likewise, Maternally Derived Antibody (MDA) levels in their piglets, which depended on the antibody titer of the sow, were very low and not protective. Repeated breeders’ vaccinations during pregnancy are  recommended in the literature and by the World Animal Health Organization (OIE), in order to achieve a population coverage >80% with a viral neutralization titer (VNT) of at least ≥1:32,
≥1.5 Log10.

Keywords: FMD; Vaccination; Sows; Piglets; Antibodies; Protection

Introduction

strains cause several outbreaks on yearly basis in Israel. (1) Most of outbreaks occur in ruminants but in 2015 and 2022 pig farms were also involved (2). Vaccination against FMD is mandatory in Israel. While the vaccination protocol is well defined in ruminants, it is less precise in pigs where a single mass/blanket vaccination of breeders only, once a year, in autumn/winter is recommended (2, 3). Last vaccination course, before 2022 outbreak, was implemented between December 2021 and January 2022; a double-oil  emulsion, inactivated FMD vaccine was used, which contains the strains O-Manisa, O-3039, O-Israel 85, O-Pan-Asia 2, A-Iran 05, A-GVII 2015 (Aftopor, Boehringer Ingelheim AH, UK Ltd, Pirbright GU24 0NQ, UK), 2 ml/head, single dose in breeders.
In April 21st 2022, a FMD outbreak occurred in farrow to finish pig units located in the Northern Region of Israel, caused by a FMD virus O, Topotype ME-SA Strain PanAsia-2ANT-10 (4), named O/Tubas 21, after the name of the town, Tubas, in the Palestinian Authority (PA) territories, where the strain was firstly isolated on December 2021. The last time this FMD lineage appeared in Israel, was in the years 2011-2012 (5). As in 2015, the outbreak clinically developed mainly in the farrowing unit, with high mortality in suckling piglets. The event was unexpected, affecting offspring from breeders which had received their yearly booster just a few months before (January 2022). A booster between April 4th and 22nd 2022, was carried on account of the above mentioned FMD outbreak, which spread to Israel in ruminants in February 2022, and later on affected also pig farms due to uncontrolled movements of ruminants (beef cattle) in the Ibblin area, Northern District of Israel, where 23 pig farms are located. It was decided to investigate immediately, following the appearance of the very first clinical signs, whether there was any vaccination efficacy problem or failure in the application of the vaccination protocol.
While a description of clinical signs induced by FMD virus in pigs has been already  presented (6), the purpose of this communication is to present and discuss the results obtained from the serological investigations performed and to possibly correlate with the vaccination protocol in place in pig farms in Israel.

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