Pilot field trial of the EG95 vaccine against ovine cystic echinococcosis in Rio Negro, Argentina: humoral response to the vaccination

EDMUNDO LARRIEU; GUILLERMO MUJICA; THELMA VERONICA POGGIO; KATHERINA VIZCAYCHIPI; ROBERTO LAMBERTI

Bucarest

Congreso; ? XXVIth World Congress on Echinococcosis - Cystic and Alveolar Echinococcosis: Old Diseases - New Challenges In conjunction with the IInd National Conference of chinococcosis; 2015

International Association of EchinococcosisRomanian Association of Hydatidology?Carol Davila? University of Medicine and Pharmacy?Colentina? Clinical HospitalTHE

Cystic echinococcosis is endemic in the Rio Negro province of Argentina and, for this reason; a control program using praziquantel in dogs was developed from 1980. The transmis¬sion rate to humans and sheep has decreased significantly, however transmission persists. In 2009 the vaccination of sheep with EG95 was incorporated in some areas of the prov¬ince. The objective of the study was to evaluate the humoral responses to the vaccine EG95. Lambs received two vaccina¬tions with the EG95 vaccine followed by a single booster injec¬tion when the animals were 1-1.5 years of age. Blood samples from vaccinated animals were obtained for determination of antibody titles against EG95 protein. Anti-EG95 responses were determined as described by Heath and Koolaard, 2012. Blood samples were centrifuged to obtain serum and samples were maintained at 5°C before prior to being stored at -20°C. Responses were evaluated from a total of 189 animals (sheep of different ages that were all bled in 2014, no vaccinated, old sheep for control area, lamb with first doses only just before second dose, lamb with second doses just before the third doses, sheep with the three doses one year after doses 3, sheep with three doses two year after doses 3, sheep with three doses three years after doses 3, sheep with three doses four years after doses 3). Responses after the third vaccination at 1-1.5 year of age induce an increase in titer greater than seen following two immunizations. In the third and fourth years of the study there was a decrease in the level of antibody response coinciding with the period following eruption of the Puyehue volcano in Chile. The study shows the dispersion range of the individual values of the samples in the first group vaccinated from which only 1 had a titer less that the average of the animals without vaccination. Humoral response to immunization, under field conditions, has proved consistent with experimental studies, increasing with the application of the second dose and then peaking reinforcement year. The lower optical density values were observed in two cohorts of vaccinated animals suffering greater nutritional difficulties, although the differences were not significant. Key words: echinococcosis, vaccine EG95, sheep, antibodies