Development of an efficient antitick natural formulation for the control of acaricide-resistant ticks on livestock.

Animal production has a key role in global economic development and food security. Ticks, specifically Rhipicephalus microplus cause substantial economic and health impacts on more than eighty percent of the world cattle population. Though synthetic acaricides play a major role in tick management, their injudicious usage has caused environmental pollution and also promote the establishment of multi-acaricide resistant tick populations which is a matter of great concern. To provide an effective tool for controlling these resistant ticks, the present work was aimed to develop safe and inexpensive antitick natural formulations. Our bioprospection studies of Ageratum conyzoides plant established it as a species potentially having strong acaricidal activity due to the presence of potent acaricidal phyto-chemicals. To develop a suitable antitick natural formulation, 41 samples/fractions/formulations were prepared from the dry powder of the whole aerial part of the A. conyzoides plant using different techniques and delivery matrices. The strongest antitick effect was recorded for formulation ACF6, which demonstrated 87 ± 6% mean mortality with 57 % inhibition of oviposition in treated female ticks. Ticks treated with the ACF6 formulation showed a significant (p < 0.001) reduction in cuticular protein (1.238 ± 0.01 mg/mL) as compared to control ticks (2.928 ± 0.01 mg/mL) but no significant difference in chitin content of treated ticks and control ticks was observed. The formulation was found safe in a rat model as no significant differences in biochemical and haematological parameters among treated and control rats were noted. Histopathological studies indicated no sign of hepatocellular necrosis and no significant changes in the weights of liver and spleen was recorded. The overall in vivo efficacy of the formulation was 85 % for experimentally infested cattle with direct mortality of more than 80 % within 96 h post-application. The lethal effect of the formulation was in the form of drying and dead ticks 1-2 d after application. The developed formulation has the potential to be adopted as an alternative tick control measure in an ecofriendly manner.

Characterization of acaricide resistance in Rhipicephalus microplus populations infesting cattle in northeastern India and assessment of local plant extracts for tick management.

In the present study, the tick isolates were collected from Assam state, of northeastern region (NER) and characterized using in vitro bioassay, biochemical and molecular assays. Comparing LC50 value of susceptible IVRI-I and larvae of field isolates, revealed that RF against deltamethrin was highest for Morigaon (MGN = 21.8) and lowest for Sonitpur (SNP = 3.3) isolate. The RF against cypermethrin was highest for Nagaon (NGO = 5.0) and lowest for Barpeta (BPT = 1.2) isolate. Against coumaphos, the highest RF of 4.5 was calculated for BPT (4.5) and lowest for NGO (1.3) isolate. While using adults based assay, highest RF of 24.68 against deltamethrin and lowest RF of 4.96 was determined for MGN and SNP isolate, respectively. In contrast to the results obtained using larvae, against cypermethrin, highest RF was recorded for Kamrup Metropolitan (KMP) while it was NGO isolate using larvae. In case of coumaphos, both larvae and adults of BPT isolate were also highly resistant and lowest RF was detected in SNP (2.30) isolate. All the isolates were susceptible to ivermectin. A significant correlation (p < 0.01) between deltamethrin resistance and higher expression of glutathioneS-transferase was observed while no correlation with esterase and monooxygenase enzymes activity was noted. For the development of possible ecofriendly control measure, different accessions of Argemone mexicana and Datura metel plant species were collected, extracted and screened against adult ticks. Two accessions, NEA-03 and NED-06 collected from Amlighat and Diphu (East Karbi Anglong) were more than 90 % effective. Further dose response study of these accessions determined the LC50 values of 4.86 and 3.96 %, respectively.The resistance status of the collected tick isolates was compared with the data generated from other regions having higher livestock population and possibility of exploitation of identified plant species for the development of natural antitick product is discussed.

Comparative impact of coumaphos, amitraz and plant extract of Ageratum conyzoides on the oogenesis of Rhipicephalus microplus.

The present experiment was conducted to evaluate and compare the impact of Ageratum conyzoides plant extract (ACE) with routinely used synthetic acaricides i.e., amitraz and coumaphos on the oogenesis of engorged adult females of Rhipicephalus microplus tick. On the day of dropping from the host, panoistic ovary of R. microplus appeared white in colour, horseshoe shaped, hollow tubular organ with immature oocytes predominantly in dorsal groove. Different developmental stages of oocytes (I-V) proceed simultaneously and asynchronously. Oocytes showed gradual increase in size, deep brown colored with accumulation of eggs in oviduct during 24-72 hours of development.At LC90 concentration a highly significant (p < 0.001) cessation of egg laying after exposure to amitraz and ACE while significant reduction (p < 0.01) of egg laying in coumaphos treated ticks was observed. Upon dissection of treated ticks, uterus and oviduct packed with eggs, which failed to pass out was observed. The histo-architectural alterations including presence of extensive vacuolation, alteration of oocyte morphology, deformation of chorion and disorganization of yolk granules were observed in the treated ovaries. Histochemically, low level of storage or synthesis of essential elements viz., proteins, polysaccharides and lipids in treated oocytes responsible for reduction of fertility and inhibition of progress of vitellogenesis was observed.