Prevalence of Theileria equi and Babesia caballi Infection in Horses from Northern Italy

Introduction

B abesia caballi and Theileria equi are the causative agents of equine piroplasmosis, an important tick-borne disease of horses in many areas of the world. Most prevalence studies carried out in Italy have focused on regions of southern and central Italy (Khoury et al. 1994, Torina et al. 2007, Passamonti et al. 2010). Only one published study has reported infection prevalence in northern Italy. Moretti et al. (2010) evaluated 188 horses from the regions of Emilia-Romagna and Friuli-Venezia-Giulia and reported that ∼50% Emilia-Romagna–78% Friuli-Venezia-Giulia of examined horses were seropositive to one or both parasites and conclude that there is an increasing trend of infection in these areas. The authors also recommended two diagnostic techniques, serology and polymerase chain reaction (PCR), for the detection of animals with a latent infection. Here, the authors evaluated infection status for T. equi and B. caballi of 294 horses living in a mountainous area of northeastern Italy, by indirect immunofluorescent antibody test and PCR.

Materials and Methods

Results and Discussion

Figure 1 summarizes the results of this preliminary study on the prevalence of equine piroplasmosis in a relatively limited area of northern Italy. Serological prevalence was 8.5% in the horses tested: 8.2% of the animals were positive for circulating antibodies against T. equi, whereas 0.3% were positive for anti–B. caballi antibodies. No dual infections were observed. Of those horses with positive serology to T. equi, 33% were also positive in PCR, whereas none of the seropositive horses for B. caballi was positive in PCR. No significant correlation between sex or age was found for infection status. None of the horses examined showed clinical signs of disease. However, positive PCR results indicate that at least T. equi is actively circulating in the area.

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FIG. 1.

Results of serology and polymerase chain reaction in horses tested for equine piroplasmosis in a rural area of northern Italy.

Infection prevalence is markedly lower than that reported in Moretti et al. (2010) for the Emilia-Romagna region. This may be due to a difference in geographic features: Moretti et al. studied predominantly low-lying plains, whereas the present study was carried out in a mountainous climatic zone. It may also be due to differences in vector populations. Little is known concerning the presence of efficient tick reservoirs/vectors in this area. Rhipicephalus bursa and Rhipicephalus turanicus have both been reported (Iori et al. 2005), whereas preliminary results of dragging in the study area during the summer of 2010 have shown a predominance of Ixodes ricinus (data not shown). Iori et al. (2010) have recently reported I. ricinus as a possible vector for T. equi, with infection prevalence in this species of ∼5%. Further, the complex mechanisms of preimmunity and maternal transfer of antibodies may explain the lack of clinically manifest disease in horses in this area.