COCCIDIOSIS is a serious disease in newborn piglets caused by the parasite Cystoisospora suis. It exclusively infects pigs and often causes severe diarrhea in suckling piglets.
(Editor's Note: According to the Merck Veterinary Manual, cystoisospora is a new genus name that has been proposed for coccidia — eimeria and isospora — but has not gained wide acceptance.)
Parasitologists Lukas Schwarz and colleagues at the University of Veterinary Medicine-Vienna (Vetmeduni) in Austria have developed a new strategy for protecting the piglets. They infected sows with the pathogen during pregnancy. Antibodies against C. suis and other immune cells produced by the mother were transferred to the piglets through the milk, protecting them against serious infections.
The results were published in the scientific journal Veterinary Parasitology.
Vetmeduni said these findings prompted the researchers at the Institute for Parasitology to look for a way to increase the level of these antibodies in sows. The ultimate goal was to provide the piglets with as many antibodies as possible via their mother's milk during the first few days of life.
The idea paid off. Piglets from infected sows suffered less from the infection than piglets from non-infected sows. Overall, offspring from immunized sows had less severe diarrhea or no diarrhea at all, and piglets that became ill recovered faster and excreted fewer parasites compared to those from non-immunized sows.
"An infection with C. suis causes serious gastrointestinal disease in piglets. The infection is completely asymptomatic in adult pigs," Schwarz explained.
To stimulate antibody production against C. suis in sows, the researchers exposed pregnant sows to infectious stages (oocysts) of the parasite two weeks before parturition. Oocysts at the primarily infectious stage stick to the floor and other objects in the farrowing barns. Piglets ingest them, and the parasite colonizes the gut, attacking the mucous membrane. The parasites multiply in the pig's body before being excreted, and the cycle starts again.
C. suis can survive in pig barns for a number of months and is very hard to kill. This leaves farmers facing the likelihood of new infections. Sows also ingest the parasite, but due to resistance that increases with age, they are not affected by this coccidian parasite.
High concentrations of antibodies against the parasites are passed on to the piglets in the first few hours of life through their mother's milk, where they enter the blood stream and the intestines of the newborns who cannot yet produce their own antibodies. These maternal antibodies protect the piglets from infections in the first few weeks of life. The higher the concentration of antibodies in the sow's milk, the better protected her offspring are.
Piglets with milder symptoms showed higher concentrations of immunoglobulin A (IgA) in their blood. These immunoglobulins are not just in the bloodstream but also are on the surface of the mucous membranes, where they serve as a defense against pathogens. Researchers found equally high levels of IgA in the blood of the infected sows.
"To date, it has been assumed that immunoglobulins do not play a role in the course of swine coccidiosis. Our results provide the first indications that immunoglobulins could actually be quite important. Additional studies are required to identify the exact role played by the antibodies," Schwarz said.
The researchers found particularly high concentrations of IgA in colostrum. This form of "milk vaccination" might serve as a basis for developing an immunization strategy to prevent swine coccidiosis, Vetmeduni said.
"There are some effective medications for swine coccidiosis, but we would like to use the piglet's immune response to stop it in its tracks before the infection even gets started," Schwarz concluded.