Comparison of direct and indirect methods to maximise the detection of Babesia caballi and Theileria equi infections in Central Southern Italy.

This research investigates and compares different diagnostic methods for equine piroplasmosis, a tick-borne disease in horses and donkeys caused by the pathogens Babesia caballi and Theileria equi. The authors examined 1,300 blood samples, using enzyme-linked immunosorbent assay (ELISA), immunofluorescent antibody test (IFAT), various Polymerase Chain Reaction (PCR) assays, and blood smear microscopy. They concluded that a combination of PCR and ELISA or IFAT was ideal for diagnosis, due to differences in their detection limits and abilities to identify early infections.

Methodology

• The researchers collected 1300 blood samples from both symptomatic and asymptomatic equines in Central-Southern Italy between 2012 and 2014.
• These samples were analyzed using four different methods – ELISA, IFAT, PCR (one commercial and one from literature), and blood smear microscopic examination.
• To establish the most sensitive technique, the researchers verified statistical differences in proportions of positive results for each parasite and group (asymptomatic and symptomatic) among the methods using the Z-test.
• The researchers also evaluated the concordance between each pair of methods for each parasite and within the groups.
• Finally, they assessed the detection of suspect samples across four hypothetical diagnostic algorithms using serological and biomolecular assays.

Findings

• The study discovered that the commercial ELISA had a lower capability of detecting B. caballi compared to biomolecular methods and IFAT across all groups.
• The commercial PCR tests were less effective in detecting the pathogen in asymptomatic animals. This led to the conclusion that versions of PCR from literature and IFAT are best for combined diagnosis.
• For T. equi detection, IFAT was more reliable than ELISA, despite good performance from the latter. Interestingly, some samples were found positive only by ELISA and PCR, suggesting the need for simultaneous use of methods.

Implications

• The results imply that host-parasite interaction, amino-acid/genetic diversity, and differences in detection limits among the assays could explain the differences in results among the diagnostic methods.
• The authors recommend using ELISA in combination with PCR, highlighting the necessity to include PCR in laboratory diagnosis to maximise detection of early infections and support the evaluation of pharmacological treatment.