Longitudinal study of Toxoplasma gondii antibodies in female lambs from Paraiba State, Brazil

Abstract

Toxoplasmosis is a worldwide zoonosis that affects man and homeothermic animals, caused by the protozoan Toxoplasma gondii. This parasite is responsible for congenital diseases, miscarriage and stillbirth in some species, such as sheep. Although outbreaks of abortion are considered important, descriptions of these outbreaks in ewes in Brazil are rare, even though infection is highly prevalent, and isolates are very virulent. Studies have shown a strong association between the presence of antibodies against the parasite in mothers and a low occurrence of reproductive problems by T. gondii during pregnancy. The objective of the study was to evaluate the occurrence of T. gondii infection in sheep from the semi-arid region of Paraiba State, Brazil, and to determine if these animals acquire the infection in the first year of life, before the beginning of the reproductive phase. This was done by monitoring the dynamics of anti-T. gondii antibodies by indirect fluorescence antibody test (IFAT >= 64) in animal serum from birth to 12 months of age, obtained once a month. Fifty-six crossbreed females and their 61 offspring, belonging to seven semi-intensive farms (representative of the region's farms) were evaluated. Of the 61 lambs studied, 55.7% (34/61) (IC 95% 44.9%-71.4%) were antibody negative at the end of 12 months, as only presumed colostrum antibodies were detected in these animals or they remained negative throughout the study. The remaining 44.3% (27/61) (IC 95% 28.6%-55.1%) were either presenting high antibody titres since the first examination (5/27; 18.5%), or became seropositive in the first year of life (22/27; 81.5%). Antibody titres ranged from 64 to 65,356 and the variables analysed (presence of cats, type of water supplied, type of flock, sanitary management and existence of sewage within the property) were not associated with the seroconversion of the lambs. The study concludes that about half of the ewes were seronegative at the age of one year, the time of their first gestation and, probably, they are more susceptible to reproductive problems caused by this coccidia.