STUDIES ON TICKS AND HAEMOPARASITES OF CATTLE IN INDO-BHUTAN BORDER DISTRICTS OF ASSAM
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Date
2017-07
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College of Veterinary Science, Assam Agricultural University, Khanapara, Guwahati-781022
Abstract
Ticks and tick-borne blood parasitic diseases are recognized as a major constraint to livestock production causing clinical and subclinical parasitism and greatly hamper the health of animals worldwide including India. The present study was carried out to record the tick infestation and tick-borne blood parasitic diseases (haemoprotozoal and haemorickettsial) in crossbred and indigenous cattle of four Indo-Bhutan border districts of Assam, viz. Kokrajhar, Chirang, Baksa and Udalguri for one calendar year from April 2016 to March 2017.
A total of 533 cattle were examined of which 266 (49.90%) were found infested either with Rhipicephalus (Boophilus) microplus (23.45%) or Haemaphysalis bispinosa (15.75%) or with both the ticks (mixed infestation) (10.69%). Crossbred cattle were found having higher prevalence of tick (53.50%) compared to the indigenous (49.34%) which was statistically non-significant. Tick infestation was the highest in adult cattle of > 3 years of age (56.61%) and the lowest in calves of < 1 year of age (41.74%) while in young cattle of 1- 3 years it was 52.89 %. Higher prevalence of tick infestation was recorded in female cattle (53.57%) than the males (44.80%). Also, tick infestation was recorded higher in indigenous cattle which were free ranged (49.34%) than that of the stall fed crossbred cattle (41.55%). According to the distribution of ticks on different body parts of cattle, infestation was observed highest in inguinal region including udder and scrotum (82.70%) followed by neck (71.42%) and lowest seen in back region (22.55%).
Prevalence of haemoparasites determined by microscopic examination of Giemsa stained blood smear followed by confirmation in Polymerase Chain Reaction (PCR) revealed presence of three species, Theileria orientalis (62.85%), Babesia bigemina (1.87%) and Anaplasma marginale (2.62%) with an overall 67.35% haemoparasite prevalence. However, no case of Babesia bovis, Theileria annulata and Trypanosoma evansi was detected during this study by microscopy and PCR. Haemoparasite infection was higher in crossbreds (77.92 %) than the indigenous animals (65.57 %). Adult cattle > 3 years age were found more susceptible to blood parasitic diseases (80.42%) than young (68.11%) and calves (54.85%). Females had higher prevalence (74.02%) compared to the male animal (58.22%).
PCR amplified parasite DNA of T. orientalis, B. bigemina, A. marginale showed clear band at 776 bp, 1124 bp and 160 bp respectively.
Demonstration of T. orientalis DNA in the eggs laid by female engorged R (B). microplus obtained from T. orientalis positive case suggested the tick species as the vector of the parasite and transmitting it transovarially to the subsequent generations.
Screening of 100 sera samples by Indirect ELISA revealed presence of Trypanosoma evansi antibodies in 7 samples with O.D value of 0.45.
Phylogenetic analysis of MPSP gene of Theileria orientalis isolate revealed 99.00% similarity with the isolate reported from Thailand and Myanmar. Anaplasma marginale isolate in the present study bear 93.46% similarity with isolates reported from USA and Mexico while the Babesia bigemina isolate has been found to be very distinct molecular type in terms of 18S rRNA gene. The high level of unrelatedness could be due to lack of interaction between the present isolate reported and other isolates.
Quantification of Babesia bigemina organisms by Real Time PCR (RT-PCR) revealed presence of 8.01 x 1011 DNA copies µl-1 of B. bigemina.
Haematological estimation in both crossbred and indigenous cattle infected with haemoparasites revealed anaemia in terms of lowered Hb and PCV values.
This study fairly suggests that R. (B). microplus and H. bispinosa infestation are highly endemic and the blood parasitic diseases, Oriental theileriosis, babesiosis and anaplasmosis are prevalent in subclinical state in cattle in the study areas.