Molecular Epidemiology of Theileria annulata in Cattle from Two Districts in Punjab (Pakistan)

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 investigation of bovine tropical theileriosis outbreak in an organized dairy cattle farm in Madhya Pradesh, India

The present study aimed to investigate an outbreak of Theileria annulata (T. annulata) infection in an organized dairy cattle farm in Madhya Pradesh, India, using clinical and molecular techniques. Following the deaths of two crossbred cattle in March 2021, 43 blood samples were collected from infected and apparently healthy animals and examined by blood smear and polymerase chain reaction (PCR) techniques. The blood smear examination showed that 23.25% of samples were positive for Theileria organisms, while conventional PCR targeting the 18S ribosomal RNA (18S rRNA) and T. annulata merozoite surface antigen-1 (TAMS-1) genes revealed that 32.55% of samples were positive for T. annulata. PCR targeting cytochrome b (Cytb) gene showed 46.51% of samples were positive for T. annulata. Haematological analysis confirmed clinical signs of infection in affected animals, which were treated with buparvaquone @ 2.5 mg/kg body weight intramuscularly along with supportive medicine. Two 18S rRNA gene amplicons were sequenced and analysed in a phylogenetic tree and haplotype network with 54 Indian and 38 foreign sequences. The phylogenetic tree revealed two groups with a high posterior probability and bootstrap value, while the haplotype network revealed 35 haplotypes, with haplotype 1 (H1) being the most abundant and several single haplotypes clustering around it, indicating fast and widespread expansion. Genetic diversity indices and neutrality tests confirmed that the population was expanding. These studies highlight the significance of prompt and precise diagnosis and management of T. annulata outbreaks and provide insights into its evolutionary history and population dynamics of T. annulata in India, which could aid improving disease preventive and control strategies.

Simultaneous molecular detection of Anaplasma marginale and Theileria annulata in cattle blood samples collected from Pakistan-Afghanistan boarder region

Theileria annulata (T. annulata) and Anaplasma marginale (A. marginale) are among the most extensively reported tick borne pathogens and are associated with huge economic losses worldwide. A total of 298 cattle blood samples were screened to report the presence of these two pathogens. The samples were collected from apparently healthy cattle (Achai, n = 155, Jersy, n = 88 and crossbred, n = 55) in Bajaur district of Khyber Pakhtunkhwa (KPK) during June and July of 2022. A total of 31 out of 298 cattle (10.4%) were found infected with T. annulata as PCR amplified a 156 base pair fragment from Tams-1 gene of T. annulata from their blood. While 16/298 animals (5.4%) were found infected with A. marginale as they amplified a 382 base pair fragment specific for msp5 gene of this bacterium. Three animals (1%) were found co infected. Cattle susceptibility to T. annulata infection was significantly higher than A. marginale infection (P < 0.001). Phylogenetic analysis revealed that Pakistani isolates of both detected pathogen clustered together and were closely related isolates from worldwide countries. Prevalence of T. annulata varied significantly among the sampling sites (P = 0.05) while no such association was observed for A. marginale among the tested cattle. Epidemiological data analysis revealed that none of the studied risk factors was found associated either with the prevalence of T. annulata or A. marginale (P > 0.05) among enrolled cattle. In conclusion, our study has revealed a relatively higher prevalence of T. annulata than A. marginale in cattle from the Bajaur district in KPK. This information is important for improving the productivity of the livestock sector, which is one of the main sources of income in the country. It is recommended that this data be taken into account for the development and implementation of effective tick control programs, as well as for the improvement of livestock management practices to prevent and manage TBDs in Pakistan.

Prevalence and Risk Factors Associated with Theileria annulata Infection in Two Bovine Portuguese Autochthonous Breeds

Tropical Bovine Theileriosis is an important tick-borne disease. This study aims to assess the occurrence of Theileria annulata infection in two indigenous Portuguese cattle breeds. A total of 843 blood samples collected from animals of Alentejana (n = 420) and Mertolenga (n = 423) breeds were analyzed. The detection of Theileria annulata was determined by amplification of a fragment of the merozoite-pyroplasm surface antigen gene with 319 base pairs (bp). The prevalence found (10.8%) is lower than that reported in previous studies (21.3%). A statistically significant difference was found for positivity between breeds (p < 0.05). There is also a higher probability of older animals being positive compared to younger ones (p < 0.05). The region where Mertolenga animals are located is shown to have a significant impact on positivity (p < 0.05). Thus, the development of sustainable T. annulata control strategies and their implementation, adapted to the epidemiological conditions of higher risk, will be extremely important.

Molecular epidemiology, associated risk factors, and phylogeny of Theileria annulata infecting buffaloes and cattle from different agro-climatic regions of Punjab, Pakistan

Background

Tropical theileriosis is the most prevalent hemoprotozoan disease in Pakistan.

Aims

The study aimed to investigate the epidemiology and evolutionary relationship of Theileria annulata in bovines in diverse agro-climatic regions of Punjab, Pakistan.

Methods

800 blood specimens were collected from asymptomatic cattle (n=480) and buffaloes (n=320) using a multistage sampling method from Sargodha (n=400) and Multan (n=400) districts. The samples were assessed for blood smear microscopy and cytochrome b gene based PCR. Twenty samples were collected from each union council of each district.

Results

The overall prevalence of T. annulata infection in bovines was 9% and 17.13% as determined by blood smear analysis and PCR, respectively. The disease positivity in cattle and buffaloes was respectively 10.21% and 20.42% by blood smear screening and 7.19%, 12.19% by PCR. The overall PCR based prevalence in the Sargodha and Multan districts was 19% and 15.25%, respectively. Absence of rural poultry, tick infestation, and a history of tick-borne diseases had significant effect in cattle. Tick infestation and age were the main statistically significant disease determinants in buffaloes. The evolutionary analysis of the cytochrome b gene showed that the Pakistani isolate infecting buffalo was related to those from Iran, India, Egypt, and Sudan. The isolate from cattle was genetically close to those from Pakistan, India, Iran, Iraq, and Turkey.

Conclusion

It can be concluded that biotic and abiotic factors contribute to disease occurrence. The current study will help to devise control strategies to prevent substantial economic losses.

An insight into misidentification of the small-subunit ribosomal RNA (18S rRNA) gene sequences of Theileria spp. as Theileria annulata

BACKGROUND

There had been isolated reports of the presence of novel Theileria annulata genotypes based on the 18S rRNA gene sequence data from India, Pakistan and Saudi Arabia; but, these studies were restricted to limited field samples. Additionally, no comparative study has been conducted on all the isolates of this parasite from different countries whose sequences are available in the nucleotide databases. Therefore, we aimed to study the genetic diversity of T. annulata based on all available nearly complete 18S rRNA gene sequences in the GenBank™. Out of a total of 312 gene sequences of T. annulata available in the NCBI database, only 70 nearly complete sequences (> 1527 bp) were used for multiple sequence alignment.

RESULTS

The maximum likelihood tree obtained using TN93 + G + I model manifested two major clades. All the valid host-cell transforming Theileria species clustered in one clade. The T. annulata designated sequences occupying this clade clustered together, excluding two isolates (DQ287944 and EU083799), and represented the true T. annulata sequences (n = 54). DQ287944 and EU083799 exhibited close association with Theileria lestoquardi. In addition, 14 Indian sequences formed a large monophyletic group with published Theileria orientalis sequences. The broad range of sequence identity (95.8-100%) of T. annulata designated sequences indicated the presence of different Theileria spp. A closer analysis revealed the presence of three Theileria spp., namely, T. annulata, T. orientalis, and two isolates (DQ287944 and EU083799) closely related to T. lestoquardi. The true T. annulata sequences manifested 98.8-100% nucleotide identity within them. EU083799 and 14 misidentified Indian T. annulata sequences exhibited the highest similarity with T. lestoquardi (98.6-98.8%) and T. orientalis (98.0-99.9%) in comparison with the other Theileria spp. of domestic and wild ruminants.

CONCLUSION

In the course of analyzing the genetic diversity of T. annulata, we identified the nearly complete 18S rRNA gene sequences of other Theileria spp. that have not only been misidentified as T. annulata in the GenBank™, but are also published as T. annulata. Moreover, a high level of sequence conservation was noticed in the 18S rRNA gene of true T. annulata and T. orientalis sequences.

Seasonal survey, risk factor's analysis and genotyping of Theileria annulata infecting cattle in Punjab province, Pakistan

Theileriosis is one of the most frequently reported tick borne diseases in tropical and subtropical regions and leads to annual economic losses, such as the reduced dairy products and increased casualties. Tropical theileriosis is caused by Theileria annulata and the present study was designed to improve our knowledge of Theileria annulata infection in Pakistani cattle. In order to assess the prevalence of Theileria annulata on cattle from Multan district in the Punjab province (Pakistan) according to seasons and other risk factors, a total of 1020 blood samples (340 samples each from cross, Holstein Frisian and Sahiwal breed) were collected between 2020 and 2022. Based on Tams-1 partial sequence amplification, the overall T. annulata prevalence was estimated at 11.3% (115/1020). The highest prevalence was observed in autumn season (14.1%), followed by winter (12.9%), summer (11.4%) and spring (6.7%) season. Sahiwal cattle were most susceptible to T. annulata infection (13.2%) followed by Crossbred (11.8%) and Holstein Frisian (8.8%). Epidemiological factor analysis revealed that female cattle, cattle rose with other dairy animals at farm, tick infested cattle, and cattle raised with dogs infested with ticks were associated with the prevalence of T. annulata. White blood cells, lymphocyte (%), Monocyte (%) hemoglobin, mean cell hemoglobin, mean corpuscular hemoglobin concentration, and platelet count were significantly affected blood parameters in T. annulata positive cattle of all three breeds. Representative partial Tams-1 sequences of four Pakistani T. annulata isolates revealed a single genotype genetically close to those infecting cattle from neighboring countries like Iran, Turkey and Egypt. Longitudinal survey and phylogenetic positioning of T. annulata is recommended for epidemiological correlation, diagnosis and treatment of theileriosis in such an agricultural region of Pakistan.