Evaluation of Oral Bait Vaccine Efficacy Against Classical Swine Fever in Village Backyard Pig Farms in Bhutan

Abstract

Control and eradication of classical swine fever (CSF) in countries with a high proportion of backyard holdings is a challenge. Conventional attenuated Chinese C-strain vaccines, though safe and effective, are difficult to use in backyard farms due to various practical reasons. The aim of this study was to evaluate the efficacy of the CSF oral bait vaccine in village backyard pig farms and to assess the farmers' knowledge on CSF and motivation on using oral vaccines. The pigs were fed the bait by the farmers themselves; one bait was given on day 0, followed by second bait on the next day. Seventy-three per cent (140 of 193 pigs) of vaccinated pigs had either a slight (2-fold-3-fold; 60 pigs) or significant (at least 4-fold; 80 pigs) increase of the antibody titre against CSFV. A significant increase of the antibody titres was mainly observed in pigs with no pre-vaccination titre (OR = 12, 95% CI = 4-40). The number of pigs with protective antibody titres (≥40) rose from 47 (24%) to 115 (60%) following vaccination. Only 30% of the farmers claimed to be familiar with CSF, although clinical signs they mentioned were rather unspecific and could relate to many other pig diseases. Most of the farmers claimed to be motivated to use oral vaccines if made available. The oral vaccine could be a substitute for the conventional attenuated CSF vaccines in areas where it is logistically difficult for veterinarians to visit. It may therefore be a useful tool to combat endemic CSF disease in regions where the disease continues to have a serious impact on the backyard farmers who depend on pig farming for their sustenance and livelihoods.

Investigations of selected pathogens among village pigs in Central Papua, Indonesia

“…While failure due to poor technique cannot be discounted, false reporting of the vaccination status of an individual animal by farmers might cause these seemingly negative results in vaccinated animals. In another study, similar levels of seroconversion were reported when an injectable preparation of a Chinese vaccine strain was used (Malo 2011) or when oral preparations were used for village pigs (Milicevic et al 2013, Monger et al 2015. Further study is warranted to assess the efficacy of the Chinese vaccine strain in village pigs.…”

Classical Swine Fever—An Updated Review

“…In addition, these vaccines were also adapted to a bait format for oral immunization of wild boar [6,215,216] and were recently explored for the vaccination of domestic pigs under backyard conditions [217,218,219]. While these vaccines usually have outstanding virtues in terms of onset, spectrum and duration of immunity [158,220,221,222,223], the main drawback is the lack of a serological marker concept [160] that would allow differentiation of field virus infected from vaccinated animals (DIVA concept).…”

A bread‐based lyophilized C‐strain CSF virus vaccine as an oral vaccine in pigs

“…The uptake of oral vaccine bait is one of the factors influencing the success rate of oral immunization (Monger et al, ). To ensure the success rate of vaccine uptake, different strategies were utilized, such as providing the vaccine along with banana or rice bran or administering directly hand to mouth (Porntrakulpipat et al, ).…”

“…The price of oral vaccine is relatively high compared to vaccines for parenteral application (Monger et al, ). This fact makes oral vaccines less attractive to the relevant authorities despite the fact that inefficient parenteral vaccination campaigns with the described constraints tend to fail to reach appropriate herd immunity and should therefore not be considered cost efficient.…”

“…However, the recommended route for vaccination is via intramuscular injection, which requires a veterinarian or trained para‐veterinarian. In many developing countries, a shortage of veterinarians or trained para‐veterinarians, combined with a pig population kept mostly in small‐scale production systems often situated in remote areas, hampers the efficiency of disease control (Monger, Stegeman, Dukpa, Gurung, & Loeffen, ). One possibility to overcome these problems is to provide the vaccine in a form that the farmers can use themselves.…”