Guardians of the Herd: Molecular Surveillance of Tick Vectors Uncovers Theileriosis Perils in Large Ruminants

Theileria sp. (Piroplasmida: Theileriidae) is one of the most widely known infections transmitted by hard ticks (Acari: Ixodidae) and has been linked to significant economic losses across the globe. The study's main emphasis was theileriosis, a disease that is common in Pakistan and has an incidence ranging from 0.6% to 33%. Through DNA screening of the vector ticks and host blood, this study sought to determine the risk of tick-borne theileriosis in populations of buffalos (Bubalus bubalis) and cattle (Bos indicus) in Toba Tek Singh district of Punjab, Pakistan. Identified tick species include Hyalomma anatolicum (35.4%), Rhipicephalus (Boophilus) microplus (30.2%), and R. sanguineus (25%). Tick specimens were collected from animals and their respective microenvironments. PCR assays targeting Theileria annulata were used to investigate the infection in the DNA extracted from the collected blood samples from large ruminants and salivary glands (SGs) of the Hyalomma ticks. The 18S rRNA of T. annulata was amplified using specific primers. Positive T. annulata amplicons were sequenced and verified using BLAST analysis. Overall, 50% of SGs contained T. annulate DNA. Female ticks, and those collected from cattle and from riverine environments had significantly higher (p < 0.05) rates of Theileria infection in their acini. Overall prevalence of Theileria infection was 35.9% in blood collected from large ruminants. Cattle had a substantially greater frequency of bovine theileriosis (43.2%) than buffalos (28.7%). Age and sex of large ruminants were significantly positively associated (p < 0.05) with Theileria infection. Furthermore, compared to non-riverine cattle (35%) and buffalo (19.5%), riverine cattle (52.2%) and buffalo (36.2%) showed a considerably higher prevalence. The results of this study, which is the first in Pakistan to examine the blood of large ruminants and vectorial function of Ixodid ticks in the transmission of T. annulata along with associated risk factors, offer an important insight for risk assessment of Theileria infection in livestock using vectorial infectivity.

Molecular epidemiology of Theileria annulata infection of cattle in Layyah District, Pakistan

Theileria annulata is the cause of tropical theileriosis in cattle in Pakistan, where it has a significant impact on the cattle industry. Here we report the molecular detection and seasonal prevalence and blood parameters of T. annulata infection in crossbred, Holstein Frisian and Sahiwal breed in Layyah District in the Punjab. In total, 844 blood samples (cross = 244, Holstein Frisian = 300, Sahiwal breed = 300) collected in 2017 and 2018 were tested. Blood smear screening revealed 125/844 (15%) of cattle positive for Theileria species. PCR amplification of cytochrome b gene indicated an overall T. annulata prevalence of 21% (174/844). The highest prevalence was observed in autumn season (53%), followed by winter (20%), summer (14%) and spring (3%). Crossbred cattle were the most susceptible to T. annulata (28%) followed by Sahiwal (19%) and Holstein Frisian. Representative partial cytochrome b gene sequences of T. annulata revealed phylogenetic similarities with sequences submitted from India, Iran, China, Turkey and Spain. Small numbers of ticks, including Hyalomma anatolicum, Hyalomma excavatum, Rhipicephalus microplus, and Haemaphysalis punctata, were identified from cattle but none of them was found PCR positive for the presence of T. annulata. Analysis of the hematology data indicated that red blood cell, hemoglobin, mean cell hemoglobin, mean corpuscular hemoglobin, lymphocyte (%), monocyte (%) and platelet count were significantly altered in T. annulata-positive cattle of all three breeds. Screening of cattle by PCR for the detection of T. annulata is recommended for diagnosis and treatment.