Cystoisospora suis is the most pathogenic species of swine coccidia in suckling piglets. Affected animals show watery diarrhea and wasting which results in uneven weaning weights and economic losses for the farmer. In the case of C. suis only little information on the immunity and especially on the humoral immune response is available.
Currently it is not clear whether humoral factors, such as antibodies, play a role in the development of immunity against this protozoan parasite. Some studies are dealing with an involvement of antibodies in immunity against C. suis, while others suppose that cellular immunity is predominantly responsible for protection. Therefore, the aim of this study was to investigate antibodies specific for sporozoites and merozoites of C. suis in colostrum/milk of sows and in serum and jejunal mucus of infected and non-infected suckling piglets in their first four weeks of life.
A transfer of maternal antibodies specific for sporozoites and merozoites of C. suis to piglets could be demonstrated. These persisting antibodies in sows might have been acquired by previous natural transient infections or might be maintained by possible persisting extraintestinal stages. Maternal transfer of C. suis-specific antibodies did not provide protection against a clinical manifestation of cystoisosporosis in experimentally infected piglets. A first indication of an involvement of IgA in the immune response to the infection could be demonstrated. Whether this protective effect is direct or indirect with IgA serving as a marker for other protective immune mechanisms has to be further investigated. A supposed onset of endogenous antibody production in piglets at the age of 21-28 days might be based on a maturation of the adaptive immune system. It can be assumed that the necessary level of transferrable maternal factors providing protection in piglets affected by cystoisosporosis is not reached via naturally acquired infections of sows. It still has to be investigated whether a protection against cystoisosporosis could be achieved by an enhancement of maternal responses, such as immunization of sows before parturition.
In this setting, C. suis-specific antibodies might be useful markers for the expected clinical severity of porcine neonatal coccidiosis.
Furthermore, for the first time the complete life cycle of C. suis including sporulated oocysts sporadically was described. Antibody interactions with all developmental stages of C. suis can be studied now in vitro. In summary, functional analyses in combination with clinically applied research could help elucidating important mechanisms in the immune response to C. suis.
Cystoisosporosis / pig / antibody development / immunoglobulins