Assessment of Theileria equi and Babesia caballi infections in equine populations in Egypt by molecular, serological and hematological approaches

Abstract

Background: Equine piroplasmosis (EP) caused by Theileria equi, Babesia caballi, or both, contributes to significant economic loss in the equine industry and remains uncontrolled in Egypt. This study focuses on surveying T. equi and B. caballi infections and hematological disorders in equine populations in Egypt.

Methods: Theileria equi and B. caballi infections were assessed in blood from 88 horses and 51 donkeys in Egypt using light microscopy, indirect immunofluorescent antibody test (IFAT), nested PCR (nPCR), and competitive-ELISA (cELISA) assays. PCR products were examined for specificity by DNA sequencing. Hematological alterations were evaluated using a standard cell counter.

Results: Microscopic analysis revealed EP infection in 11.4% and 17.8% of horses and donkeys respectively. IFAT detected 23.9% and 17.0% infection of T. equi and B. caballi, respectively, in horses, and 31.4% of T. equi and B. caballi in donkeys. T. equi cELISA detected 14.8% and 23.5% positive horses and donkeys, respectively, but the B. caballi RAP-1-based cELISA failed to detect any positives, a result hypothesized to be caused by sequence polymorphism found in the rap-1 genes. Nested-PCR analysis identified 36.4% and 43.1% positive horses and donkeys, respectively for T. equi and it also identified 19.3% and 15.7% positive horses and donkeys, respectively for B. caballi. The overall EP incidence found in the population under study was relatively high and comparable regardless of the diagnostic method used (56.8% using nPCR and 48.9% using IFAT). Hematologic analysis revealed macrocytic hypochromic anemia and thrombocytopenia in all piroplasma-infected horses.

Conclusions: The data confirm relatively high levels of EP, likely causing hematological abnormalities in equines in Egypt, and also suggest the need for an improved serological test to diagnose B. caballi infection in this region.

Keywords: Babesia; Competitive ELISA; Equine; Hemogram; IFAT; Nested PCR; Theileria.

Fig. 1

Alignments of the DNA a and predicted amino acid sequences b among Egyptian isolate termed 87-1 rap-1 (GenBank accession no. KR811096) and its equivalent region in the BC48 rap-1 reference gene sequence (GenBank accession no. AF092736)

Fig. 2

Alignments of the predicted amino acid sequences among the PCR amplicon derived from the reference gene sequence (GenBank accession no. AF092736), and two predicted RAP-1 amino acid sequences, termed 2-5 RAP-1 (GenBank accession number KR811097) and 1-1 RAP-1 (GenBank accession number KR811095), derived from Egyptian isolates of B. caballi