Ovine toxoplasmosis: Indirect immunofluorescence for milk samples as a diagnostic tool

Toxoplasmosis in sheep causes severe economic losses to farmers and it is a major public health problem. Consumption of ovine products, like milk, is growing worldwide and techniques that allow a snapshot on possibly infected herds are important. Indirect immunofluorescence assay (IFA) is a simple, safe, inexpensive, and sensitive test commonly used to diagnose toxoplasmosis. Tachyzoites of Toxoplasma gondii have been detected in milk of several intermediate hosts, including sheep. Thus, the aim of this study was to develop and to standardize an indirect immunofluorescence assay for milk samples (individually collected or from bulk tanks) of sheep naturally infected by T. gondii. Our experimental design was composed of 40 dairy sheep divided in 4 groups (A-D) with 10 animals each. Blood and milk samples were collected individually (40 samples). Milk samples were pooled by group and another milk sample was collected from the bulk tank. The search for anti-T. gondii in sera samples and milk was performed through IFA. We found 18 blood samples positives (45%) for T. gondii with titers ranging from 1:16 to 1:128, while only 10 (25%) milk samples were positives for toxoplasmosis, both using the IFA test. IFA test was able to detect positive samples for Toxoplasmosis either when pooled or bulk tank milk samples were used. Thus, we concluded that IFA technique can be used to quickly identify T. gondii infected herds and it presents a good correlation among results from blood and milk samples when the assay was performed individually.