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Title: Verification of post-chemotherapeutic clearance of theileria equi through concordance of nested PCR and immunoblot

item Wise, Lauren
item Kappmeyer, Lowell
item DASILVA, MARTA - Washington State University
item White, Stephen
item GRAUSE, J - Animal And Plant Health Inspection Service (APHIS)
item Knowles Jr, Donald

Submitted to: Ticks and Tick Borne Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/25/2017
Publication Date: 9/5/2017
Citation: Wise, L.N., Kappmeyer, L.S., Dasilva, M., White, S.N., Grause, J.F., Knowles Jr, D.P. 2017. Verification of post-chemotherapeutic clearance of theileria equi through concordance of nested PCR and immunoblot. Ticks and Tick Borne Diseases.

Interpretive Summary: Theileria equi is an exotic infection of horses. Recent detections of horses infected in the United States led to a search for methods to eliminate infection. Also needed was a method to confirm horses were cleared of T. equi infection. Described here is a method based on immunoblotting that shows a decline in antibodies to T. equi in horses successfully treated with a chemotherapeutic shown to eliminate infection.

Technical Abstract: Certain countries including the United States remain non-endemic for particular infectious diseases such as equine piroplasmosis through import restrictions and surveillance. Endemic regions often employ premunition as the primary method to control disease, however in non-endemic countries, chemosterilization combined with methods to confirm parasite elimination are required to maintain disease-free status. The ability of imidocarb diproprionate (ID) to clear persistent Theileria equi infection from infected horses has been shown through the inability of treated horses to transmit via blood transfer. However, the common lengthy persistence of anti-T. equi antibody causes regulatory tests such as cELISA or IFA to remain positive for extended periods. Persistence of positive testing creates challenges for regulatory veterinary medicine and international trade. Concordance between nested polymerase chain reaction (nPCR) targeting the ema1 gene and immunoblotting (IB) measuring declination in anti-EMA1 and anti-EMA2 antibody were used to verify clearance of T. equi from 179 ID-treated horses. These data support the use of IB to demonstrate declining anti-EMA1 and EMA2 titers in T. equi-infected horses subsequent to successful ID treatment. Such data provide concordant support to a negative nPCR and allow for a more timely determination of effective ID clearance of T. equi. The post ID treatment results indicate that while nPCR was consistently negative by 14'days and cELISA generally remained positive after 1'year, immunoblot was on average negative after 4 months and 100% in agreement with nPCR.