Detection of antibodies to Toxoplasma gondii in oral fluid from pigs

CAMPERO, L.M.; SCHOTT, F.; GOTTSTEIN, B.; SIDLER, X.; BASSO, W.

Berlin

Congreso; 5th INTERNATIONAL MEETING on APICOMPLEXAN PARASITES in FARM ANIMALS; 2019

T.gondii infected pigs play a major role as a source of infection for humans. Detection of high-risk herds is essential to implement control measures and reduce seropositivity at the farm level. Oral fluid (OF) has been successfully used for detection of pathogens and antibodies in pigs and can be easily collected by hanging a cotton rope on the box for the animals to chew. The aim of this study was to detect antibodies against T. gondii in OF from pigs by immunoblot (IB) and to state if this method could replace standard serology. OF from experimentally infected sows (n=8) and naïve sows (n=3) (serial samples), and from group-housed fatteners (n= 42 groups, 1 sample/group) were analysed for IgG and IgA against T. gondii-SAG1 (P30) by IB. As standard of comparison, parallel collected serum samples from each animal were tested for anti-T. gondii IgG by ELISA. Specific IgG was detected in serum of all inoculated sows since 2 or 3 wpi; in 3.4 to 13% of the pigs in 11 groups and in 91 and 92% of the fatteners in 2 groups. The remaining 29 groups contained 100% of seronegative pigs. Inoculated sows showed positive IB results (IgG and IgA) at most time points from 1.5 to 4 wpi; however, at later time points positive results were intermittent. Interestingly, consecutive daily samplings (4 days) at 13 or 30 wpi showed inconsistent results. OF from groups with 91 and 92% of seropositive pigs yielded positive IB results (IgG and IgA). Naïve sows and fattener groups with ≤13% of seropositive pigs gave negative IB results. OF does not seem to be a robust matrix for detection of T. gondii antibodies. Variable sensitivity may depend on time after infection, % of seropositive animals/group and timely variations of antibody concentration in OF. Therefore, although OF may be used in epidemiological studies at the farm level, it is not equivalent to serum. In case of negative IB results on OF, a serological examination should be performed to rule out contact of swine with T. gondii.