Introduction

Bovine tropical theileriosis is a protozoan disease caused by blood protozoa Theileria annulata and it is transmitted by tick Hyalomma anatolicum anatolicum. It causes significant economic losses in large parts of Asia as reported by Hasanpour et al. (2013). It is mainly seen in cattle, sheep and goat as well as in wild and captive ungulates as reported by Radostits et al. (2007). This intracellular infection inflicts economic burden on cattle breeders in terms of mortality and morbidity as well as expenses spent on prophylactic measures against disease and treatment as reported by Durrani et al. (2008).

8. annulata has a haploid nuclear genome and is estimated to be 8.35 Mb. The genome is arranged in four chromosomes within which coding regions are predicted to be 3,792 as reported by Pain et al. (2005). Theileria annulata was described in Transcaucasian cattle in 1904 and was first named Piroplasma annulatum. It was reclassified as T. annulata after identification of schizont stage in its life-cycle as reported by Weir (2006).

Lloyd (1983) reported higher infection rate in female animals as compared to male animals. It might be due to the higher level of prolactin and progesterone hormones in female animals which make them more susceptible to any infection. Sutherst et al. (1983) reported higher prevalence in female cattle than male cattle. It might be attributed to the fact that the milch animals have higher hormonal stress, carry more ticks and thus were at higher risk of exposure to the infection. Tuli et al. (2015) reported that female animals were at higher risk of infection (30.57 per cent) as compared to male counterparts (23.11 per cent) at 5 per cent level of significance. Further within the three groups’ viz., cross-bred cattle, indigenous cattle and buffaloes, the prevalence of T. annulata was higher in females than males. Among the female population, the prevalence of infection was significantly higher (P<0.001) in cross-bred cattle followed by in indigenous cattle and buffaloes. Least prevalence was recorded in the calves between 6 months and 1 year of age (least risk of 0.32). Thus, the study was conducted to determine the sex related prevalence of Theileria annulata infection in cattle-calves in Bikaner, Rajasthan.

Materials and Methods

One hundred cattle-calves out of which 58 female and 42 male cattle-calves were screened for Theileria annulata infection during October-2015 to September-2016 brought to Teaching Veterinary Clinical Complex, College of Veterinary and Animal Science, Bikaner for treatment. A total of 100 blood samples were collected in ethylene diamine tetra acetic acid (EDTA @ 1 mg/ml) vacutainer from cattle-calves and genomic DNA were extracted using QIAamp® DNA blood mini kit (QIAGEN, GmbH, Germany) as per procedure. Aliquots of extracted DNA were kept at -20°C and subjected for nPCR.

Results and Discussion

By nPCR, 41 out of which 15 male and 26 female cattle-calves were found positive for Theileria annulata infection which produced 372-bp amplicon on 1% agarose gel.  The sex related prevalence of Theileria annulata infection in cattle-calves by nPCR is presented in Table 1 and Fig. 1.

Table 1: Sex related prevalence of Theileria annulata infection in cattle-calves

Fig. 1: Bar diagram showing sex related prevalence of Theileria annulata infection in cattle-calves

Prevalence of Theileria annulata infection was higher in female cattle-calves (44.83 per cent) as compared to male cattle-calves (35.71 per cent). Similar findings were also reported by Tuli et al. (2015). Higher prevalence in female may be attributed to the fact that the milch animals have higher hormonal stress, carry more ticks and thus are at higher risk of exposure to the infection as reported by Sutherst et al. (1983) or may be due to higher number of female cattle-calves were examined as compared to  male cattle-calves.  In India alone, tropical theileriosis is a major health problem for ten million exotic and cross-bred cattle with an expected economic loss of US$ 800 million per annum (Wilkie et al., 1998). More than half of the cost was accounted for by sub-clinical infection. In views of these facts regarding huge losses and increasing trend of bovine tropical theileriosis in cattle calves, the present investigation has been undertaken but this field require much more attention in respect of prevention and control of Theileria annulata infection.

Conclusion

Theileria annulata causes huge morbidity and mortality in cattle-calves. By nested polymerase chain reaction, it can be diagnosed more accurately. It is concluded that female cattle-calves are more susceptible than male cattle-calves for Theileria annulata infection.

Acknowledgements

The author is highly thankful to the Dr. S. K. Kashyap, Professor and Head, Department of Microbiology and Biotechnology and Dr. G.C. Gahlot, Professor and Head, Department of Animal Genetics and Breeding, College of Veterinary and Animal Science, Bikaner, Rajasthan for providing necessary facilities to carry out the present investigation. This study is financially supported by the Rajasthan University of Veterinary and Animal Science, Bikaner, Rajasthan.

Conflict of Interest

The author declares that he has no conflict of interest.

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