Prevalence, Molecular typing and phylogenetic analysis of field isolates of equine piroplasmosis

Abstract

Theileria equi (T. equi) is an obligate intra- and extra-erythrocytic parasite that causes equine theileriosis (ET) in equids. Equine theileriosis is considered a notifiable disease of global significance, a major constraint to the international movement of horses, and endemic in many countries. This disease may be difficult to diagnose, as it can produce variable and nonspecific clinical signs. A cross-sectional study was designed for the molecular characterisation of T. equi and to investigate the associated risk factors of ET accompanied by its consequences on haematological and sero-biochemical parameters. A convenience sampling of 500 blood samples were collected from ET suspect horses from January to December 2017. PCR was performed on all blood samples targeting the 18S rRNA gene of T. equi followed by sequencing; 9% animals tested positive with confirmed sequences. The isolates of this study showed high homology with Cuban, Russian and Brazilian isolates of T. equi (accession numbers KY111762.2, MG551915.1 and KY952237.1, respectively). Based on multivariate analysis, the principal risk factors consisted of absence of dogs on the premises and presence of tick infestation. The haemato-biochemical parameters showed a decrease in granulocytes and erythrocytes, and an increase in lymphocytes, monocytes, mean corpuscular volume, mean corpuscular haemoglobin, mean platelet volume, glucose, phosphorus and aspartate aminotransferase in positive horses. This is the first study which identified ET in Punjab (Pakistan) using molecular techniques and risk factors together with the haemato-biochemical variations in horses. Ticks are major external parasites of horses that affect animal welfare and transmit many infections. Little is known about the epidemiology of ticks in horses in Pakistan. Keeping in view the significance of horses and its importance, a cross-sectional study was designed to investigate species distribution, seasonal dynamics and epidemiology of ticks infesting horses in Pakistan. By convenience sampling, 500 horses in two districts (Sargodha and Lahore) of Punjab were screened for the presence of ticks from January to December 2017. Tick samples were collected from horses and identified to species level. Data of temporospatial, host and husbandry practices-related risk factors were recorded in a separate questionnaire. Ticks representing six species were collected i.e. Hyalomma impeltatum (n=52), H. impressum (n=25), H. excavatum (n=9), H. anatolicum (n=3), H. scupense (n=3) and H. dromedarii (n=3). The sex ratio of collected ticks showed 63 (66.32%) male and 32 (33.68%) female. In both districts, predominant species in horses was H. impeltatum. All infested horses had more than one tick species. The overall proportion of tick infested horses was 7% (35/500), which was high in district Lahore (8.15%) than district Sargodha (5.99%). Summer, ≤3 body condition score, satisfactory nutritional status, same breed rearing system, presence of dogs and absence of birds at farms, and activity were important risk factors associated with high equine tick infestation. This is the first report regarding the presence of H. dromedarii in the horses of Punjab.