Quantitative xenodiagnosis of theileria annulata under different cattle management systems
Abstract
Blood smears and ticks were collected from three large organized dairy farms, six commercial dairy farms, nine small holder dairy production units and twelve Gaushalas located at Hisar and surrounding areas in Haryana, India. These ticks were examined for the presence of Theileria annulata by using methyl-green pyronin staining method and blood smears were examined for the presence of T. annulata piroplasms and any other haemoprotozoan parasite using Giemsa staining method. Epidemiological variables related to host, vector and environment were also observed under different cattle management systems. A total of 3816 ticks were collected and identified from the four different cattle management systems. Out of that 1280 ticks were Hyalomma anatolicum anatolicum, 2455 were Boophilus microplus and 81 were Ornithodoros savigniyi. A total of 1200 H. a. anatolicum ticks (211 males and 989 females) were screened for the presence of Theileria. In large organized dairy farms 11.9 %, in commercial dairy farms 7.14 %, in small holder dairy production units 5.32 % and in Gaushalas 5.38 % ticks were positive for Theileria. Frequency distribution of Theileria positive acini per positive tick
showed that the higher frequency was much more in small holder dairy production units when compared to other systems as more than 25 positive acini per positive tick were seen only in small holder dairy production units. Theileria prevalence in Hyalomma ticks was highest in large organized dairy farms and lowest in small holder dairy units and Gaushalas while Theileria intensity was lowest in large organized farms and highest in small holder dairy units. The lesser intensity and higher prevalence of T. annulata in Hyalomma ticks is epidemiologically a good situation as it leads to premunity in the population whereas higher intensity and lower prevalence leads to more clinical cases of theileriosis. Thus, small holder dairy units are at a greater risk of theileriosis than organized farms. The overall prevalence of Theileria organisms in cattle was estimated to be 48.89 % by blood smear examination that included large organized dairy farms 50.76 %, commercial dairy farms 48.03 %, small holder dairy production units 59 % and Gaushalas 39.16 %. Per cent parasitaemia was highest in small holder dairy unit 0.08% followed by commercial farms 0.03% and lowest in large organized dairy farms 0.02% and Gaushalas 0.02%. The lower parasitaemia of T. annulata in cattle is epidemiologically a good situation as it shows premune status of the animals. All the four different cattle management systems were mainly infested with Boophilus microplus and Hyalomma anatolicum anatolicum of which B. microplus was more abundant. Prevalence and abundance of Theileria in ticks and prevalence of Theileria in cattle was significantly higher in mixed (cross bred and indigenous) cattle populations maintained on the same premises than the indigenous cattle population alone or cross bred cattle population alone. Intensity and abundance of Theileria in ticks and prevalence of Theileria in cattle was significantly higher in cattle of mixed feeding (stall feeding and grazing) than that of stall feeding alone. Intensity and abundance of T. annulata in ticks was significantly lower in the dairies where acaricide use was regular.