Prevalence of carrier state theileriosis in lactating cows

Comparative evaluation of diagnostic methods for detection of Theileria spp. in cows

Theileriosis is a hemoprotozoan illness of cattle in tropical regions that poses a severe economic loss to dairy farmers in the form of production loss and mortality. We designed and optimized a multiplex real-time PCR by using Taq-Man® probe for detection and quantification of Theileria orientalis and Theileria annulata simultaneously by targeting 18 s rRna and MPSP (surface merozoite protein) genes, respectively. Fifty-five EDTA blood samples from clinically Theileria-suspected cows of three Theileria-endemic districts of Odisha were processed using acridine dye based fluorescent microscopy, Giemsa staining, and PCR. PCR revealed T. annulata and T. orientalis in 11/42 (26.11%) and 24/42 (57.14%) cases, respectively. Mixed infection due to both the Theileria spp. was recorded in 7/42 (16.66%). On comparison with gold standard test (PCR), the accuracy, sensitivity, and specificity were 92.72, 95.12, and 85.71% for Giemsa staining and 96.36, 97.56, and 92.85% for acridine orange dye. Multiplex real time PCR using Taq-Man probe detected two species of T. annulata and T. orientalis simultaneously. Acridine dye based fluorescent microscopy is comparatively easy and rapid method in detection of Thelieria spp.

A Multi-copy Nucleic Acid-Based Diagnostic Test for Bovine Tropical Theileriosis

BACKGROUND

Bovine tropical theileriosis (BTT) is a haemoprotozoan tick-borne disease that implicates huge losses to livestock in terms of considerable mortality and morbidity in tropical and subtropical regions of the globe. Currently available diagnostic methods have less specificity and sensitivity towards the detection of Theileria species. Therefore, an attempt was made to diagnose Theileria annulata by targeting a multi-copy gene, viz. mitochondrially encoded cytochrome b (MT-CYB) gene via polymerase chain reaction (PCR) in different agro-zones of India.

METHODS AND RESULTS

129 cattle blood samples were collected from major livestock rearing regions of India and processed for both molecular and microscopic techniques. Screening of Giemsa-stained thin blood smears was able to detect 14 samples (10.85%) as positive for T. annulata. However, the MT-CYB gene-based PCR assay detected 107 samples (82.94%) positive for T. annulata out of 129 samples. Furthermore, the MT-CYB gene-based PCR assay was standardized in terms of its sensitivity and specificity. Specificity of PCR assay was evaluated against other common haemoprotozoan parasites of tropical countries viz. Babesia bigemina, Anaplasma marginale and Trypanosoma evansi. The multi-copy MT-CYB gene-based PCR assay provided an optimum level of sensitivity (up to the level of 10 femtogram) and high specificity. Haematological examination (Hb, PCV and TLC) of 113 samples revealed significantly (p < 0.05) decreased Hb and PCV levels in positive animals in comparison with the control group of healthy animals. However, the control group had significantly higher (p < 0.001) TLC levels than the positive group.

CONCLUSION

The MT-CYB gene-based PCR assay was found to be highly sensitive that can accurately detect the occurrence of T. annulata infection in carrier animals which are potential infection sources to healthier populations in naive demographic locations through infected ticks.

Theileriosis prevalence status in cattle and buffaloes in India established by systematic review and meta-analysis

The present study on theileriosis prevalence in cattle and buffaloes of India was reckoned by systematic review and meta-analysis. The studies on theileriosis prevalence reported during the period 1984-2019, were collected by using online databases, and offline literature and meta-analyses was done in R-Software. The theileriosis prevalence was 20% [95% level, CI 16-25%, PI 2-74%], obtained by using 70,688 samples. The increasing trend of theileriosis prevalence was observed in the recent period [2011-19] when compared to past years. A higher theileriosis prevalence in the Central zone [24%] than in other zones was observed. The state-wise analysis revealed a higher prevalence in Puducherry and Assam. The method-wise breakdown revealed a higher prevalence by serology for India [39%] in comparison to other methods. Host species-wise scrutiny indicated a higher prevalence in cattle [22%] than buffaloes [14%]. Theileriosis was caused by Theileria (T.) annulata [21%], T. orientalis [16%], and T. species [17%] in India. The theileriosis prevalence established by systematic review and meta-analysis in the present study forms the first report from India to the best of our knowledge. It also documents a valuable literature resource on theileriosis prevalence studies in India. This study helps in identifying the theileriosis high-risk zones and states in India. It will help the policymakers and various stakeholders in decision making and wisely using the scarce resources available in implementing preventive strategies effectively. Further, theileriosis prevention can be employed by adopting effective therapeutic measures and vector control strategies, which will augment the profits to dairy farmers in India.

Theileria orientalis outbreak in an organized cattle breeding farm

Theileriosis is an important tick borne disease of cattle caused by a haemoprotozoan of genus Theileria. Clinical bovine theileriosis is mainly caused by T. annulata or T. parva but the clinical disease due to T. orientalis is rare. T. orientalis mainly infect RBCs and causes "Oriental theileriosis" or Theileria-associated bovine anaemia in cattle and other livestock species. Two genotypes of T. orientalis (Chitose and Ikeda) are reported to cause severe disease in some countries. In this report, a spontaneous outbreak of Oriental theileriosis was studied in an organized Holstein-Friesian cattle breeding farm situated in the south-eastern Himalayan ranges of Himachal Pradesh State of India. Animal blood and tick samples were tested using cytological and PCR techniques. The disease episode occurred in a protracted manner spanning over 10 to 12 months and association of T. orientalis was confirmed in 93.3% of the blood and 21.7% of Rhipicephalus microplus (tick) samples. No other tick borne pathogen was detected except Anaplasma marginale in two blood samples. Haematological profiling of infected cattle showed characteristic indicators of anaemia like haemoblobin, RBC count, haematocrit value and mean corpuscular volume at either lower than normal or near the lower normal range. The prevailing persistent anaemic changes led to more severe clinical manifestations like abortion and joint inflammation. The detected T. orientalis strains and ticks species were further confirmed by nucleotide sequence analysis of 18S rRNA and 16S rRNA genes. Phylogenetically, T. orientalis strains showed clustering with other reported strains of T. orientalis from the surrounding regions. This first report of clinical Oriental theileriosis from India emphasises the importance of T. orientalis as an emerging tick borne pathogen and role of widely prevalent ticks species in disease transmission and their impact on livestock production.

Evaluation of sporozoite and macroschizont antigen (Spm2) of Theileria annulata for its diagnostic potential

Theileria are tick-borne apicomplexan parasites, which mainly infect ruminants in tropical and subtropical regions of the world. The present study was directed to investigate the serological methods for the diagnosis of theileriosis in crossbred cattle. Blood samples (n = 176) were collected from the regional cattle populations of Bihar state situated at the Gangetic plains of India. Microscopic examination of blood smears from the cattle revealed the presence of tick-borne infectious organisms (Theileria and Anaplasma) in the region. PCR-based detection of Tams1 (Theileria annulata merozoite surface antigen) gene and the sequencing of 18S rRNA amplicon from the blood samples confirmed T. annulata as the primary causative agent of theileriosis in cattle of the Bihar region. Similarly, the amplification of the msp5 gene confirmed Anaplasma marginale infection. For the large-scale epidemiological investigation, sporozoite and macroschizont (spm2) partial gene from T. annulata was cloned in pET-28a (+) vector and overexpressed in E. coli BL21 cells. Overexpressed recombinant-Spm2 (43 kDa) was purified by Ni-NTA affinity chromatography and was used for immunodetection of theileriosis in cattle serum samples. Sequence analysis of the cloned partial spm2 gene in this study showed multiple SNPs (single nucleotide polymorphisms) in T. annulata. Recombinant-Spm2 antigen was explicitly recognised by the immunoglobulins (IgG) of the cattle naturally infected with Theileria. Further, an indirect enzyme-linked immunosorbent assay (ELISA) was developed using partial r-Spm2 antigen that exhibited high sensitivity (100 %) and specificity (90.9 %). Thus, this study suggests that partial r-Spm2 can be used as a diagnostic antigen for seroepidemiological studies of T. annulata infection in crossbred cattle.

Determining Theileria annulata parasitemia through qPCR in lactating cows of Odisha, - a theileriosis-endemic region of India

Study was undertaken in a theileriosis-endemic region of India during May 2018 to April 2019 among milch cows. Blood samples collected from apparently healthy (n = 65) and Theileria-suspect cows (n = 65) were screened against T. annulata and T. orientalis infection by SYBR Green‒based real time PCR using primers designed from the isolates of study area. Cows having single infection with T. annulata with/without clinical signs of inappetence, low milk yield, pale mucous membranes, fever, enlarged prescapular lymph node, soil licking, panting, coughing, salivation and lachrymation were subjected to further investigation where parasitaemia and piroplasms per 1000 erythrocytes ranged from 1.6 × 10⁷ to 1.2 × 10⁸ parasites/mL of blood and 3-24 piroplasms in moderate group (16/65), 4.4 × 10⁸ to 6.9 × 10⁹ parasites/mL of blood and >88 piroplasms in severe group (30/65) and 1.6 × 10⁴ to 5.5 × 10⁶ parasites/mL of blood and 0-1 piroplasms in asymptomatic or carriers (17/65), respectively. Study unfolded significant difference in T. annulata parasitaemia among apparently healthy and ill cows. Phylogenetic analysis of our T. annulata isolates (NCBI accession numbers MN098316, MN098317 and MN098318) exhibited maximum similarity with the isolates detected in other parts of India.

Molecular epidemiology, risk factors and hematological evaluation of asymptomatic Theileria annulata infected cattle in Odisha, India

BACKGROUND

Theileria annulata is a tick-borne apicomplexan parasite that affects bovine and causes severe economic losses. Aims: Our study aimed to determine the molecular prevalence of T. annulata infection in asymptomatic carrier cattle in Odisha, India, to study the association of potential risk factors with theileriosis, and to investigate the effect of the parasite infection on hematological parameters in naturally affected animals.

METHODS

A total of 226 cattle blood samples were collected from seven districts of Odisha, India. Molecular diagnoses of tropical theileriosis by polymerase chain reaction (PCR), cloning, sequencing, and phylogenetic analysis of isolated parasites were performed. Potential risk factors were investigated by univariable and multivariable logistic regression statistical analysis. Hematological parameters were compared between positive and negative animals.

RESULTS

All animals included in our study were clinically normal, however, 54.86% (124/226) of examined animals were positive by PCR for T. annulata. The multivariable logistic regression showed that contact with other cattle from different herds during grazing (P<0.0001; OR: 12.75; 95% CI: 5.21-31.21), previous history of clinical signs (P=0.002; OR: 3.31; 95% CI: 1.53-6.31), and frequency of a ectoparasiticides application pre year (P<0.0001; OR: 9.22; 95% CI: 3.03-28.09) were the potential risk factors for the occurrence of tropical theileriosis. Nucleotide sequence identity data demonstrated that T. annulata strain (MN818858) Odisha shared homology of 99.6%, 99.49%, and 99.36% with Uttar Pradesh, India (MF346035), Bahrain (AF214797), and Hyderabad, India (MK034702), respectively.

CONCLUSION

This is the first study to gain insight into the molecular epidemiology, risk factors, phylogeny, and hematological analysis of asymptomatic T. annulata infected cattle from India.