[Show abstract][Hide abstract] ABSTRACT: Monitoring acaricide resistance and understanding the underlying mechanisms are critically important in developing strategies for resistance management and tick control. Eighteen isolates of Rhipicephalus (Boophilus) microplus collected from four agro-climatic regions of India were characterized and the resistant data were correlated with bioassay results, esterase enzyme activities and with the presence/absence of point mutation in the para-sodium channel gene. The adult immersion test was standardized to assess the level of resistance and resistant factors (RF) in the range of 1.2 to 95.7 were detected. Out of eighteen isolates, three were categorized as susceptible (RF<1.4), five isolates at level I (RF= 1.5- <5), eight at level II (RF=5.1- <25), and one isolate each at level III (RF= 26 -<40) and level IV (RF= >41). The esterase enzyme ratio and survival % of tick isolates was observed significantly (p<0.001) correlated with correlation coefficient (r) in α- and β-esterase activity. The correlation of determination (R(2)) for α- and β-esterase activity indicated that 73.3 and 55.3% data points of field isolates were very close to the correlation lines. For detection of point mutation, three sites (mutation in domain IIS6, T2134A mutation in domain IIIS6 and C190A mutation in domain IIS4-5 linker) of sodium channel gene were amplified and sequenced. Comparative sequence analysis identified a cytosine (C) to adenine (A) nucleotide substitution (CTC to ATC) at position 190 in domain II S4-5 linker region of para-sodium channel gene in six isolates and in reference deltamethrin resistant IVRI-IV line. The occurrence of mutation in the tick isolates having high resistance factor suggested that target site insensitivity and enhanced esterase activity is the possible mechanism of resistance to deltamethrin in the Indian isolates of R.(B.) microplus. These results also concluded that the mutation site in Indian tick isolates is similar to Australian and Brazilian tick isolates while it is different in tick isolates from Mexico and North America. This is the first report of occurrence of mutation in para-sodium channel gene of deltamethrin resistant Indian isolates of R.(B.) microplus.
[Show abstract][Hide abstract] ABSTRACT: A cross sectional study was conducted to assess the prevalence of synthetic pyrethroids (SP) resistance in Rhipicephalus (Boophilus) microplus in India. Twenty-seven areas located in six agro-climatic regions were selected for the collection of engorged ticks using two stage stratified sampling procedure. Adult immersion test (AIT) and larval packet test (LPT) were optimized using laboratory reared susceptible line of R.(B.) microplus (IVRI-I) for determination of 95% lethal concentration (LC(95)) of deltamethrin (29.6 ppm in AIT and 35.5 ppm in LPT) and cypermethrin (349.1 ppm in AIT and 350.7 ppm in LPT). The AIT with a discriminating dose (2 × LC(95)) was used to detect deltamethrin and cypermethrin resistance in the field isolates of R.(B.) microplus. On the basis of the data generated on three variables viz., mortality, egg masses and reproductive index, the resistance level was categorized as I, II, III and IV. The overall prevalence of SP-resistant R.(B.) microplus among the sampled farms was 66.6% (18/27). Out of these 18 areas, resistance to deltamethrin at level I was detected in 08 areas (resistance factor=2.0-4.9), at level II in 09 areas (RF=5.2-11.8), at level III in 01 area (RF=34.9) and at level IV in 01 area (RF=95.7). The resistance to cypermethrin was detected in 16 areas and level of resistance was detected at level I in 10 areas (RF=2.06-4.64) and at level II in 06 areas (RF=5.13-9.88). The middle-gangetic and trans-gangetic plains revealed higher density of resistant ticks where intensive cross bred cattle population are reared and the SP compounds are commonly used. The data generated on acaricide resistant status in ticks will help in formulating tick control strategy for the country.
[Show abstract][Hide abstract] ABSTRACT: extraction of active components of plants/herbs. However, organic solvent may cause toxic effects on their own and can interact with pesticides to alter their toxicity (Stratton and Corke 1981). Comparative study on toxicity of organic solvents was reported on fish, aquatic invertebrates and on insects (Stratton 1989, Tadros et al. 1994, Gorb et al. 2000). Although the effect of different solvents on R. (B.) microplus of Brazilian strain was studied (Chagas et al. 2003, Goncalves et al. 2007), it is imperative to test the effect of these solvents on laboratory reared acaricide susceptible homogenous colony of R. (B.) microplus. Hence, the present experiment was conducted to identify the suitable solvents to be used in preparation of antitick herbal formulations. MATERIALS AND METHODS
The Indian journal of animal sciences 02/2012; 74(3-82(2)). · 0.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The resistance status of Rhipicephalus (Boophilus) microplus to "Diazinon" was evaluated in 20 locations situated at various agro-climatic regions of India. Adult immersion test (AIT) was optimized using laboratory reared acaricide susceptible IVRI-I strain of R. (B.) microplus and minimum effective concentration of Diazinon was determined as 635.2 ppm. The discriminating dose (DD) was worked out as 1270.4 ppm and was tested on female ticks collected from organized and unorganized farms located at different agro-climatic regions of India. On the basis of the data generated on three variables viz., mortality, egg masses and reproductive index, the resistance level was categorized as I, II, III and IV. The average resistance factor (RF) of 6.1 (level II) was recorded in the ticks collected from the northern sub-temperate trans-gangetic plains while high average RF values of 26.65 (level III) was recorded in the ticks collected from tropical middle-gangetic plains. The tropical middle gangetic plain has a very high density of animal populations where farmers use Diazinon for tick control, for agricultural practices and for mosquito control. Due to the continuous use of OP compounds the environmental load of Diazinon has become high in the area. This is the first experimental data generated on Diazinon resistant status in ticks of India.
[Show abstract][Hide abstract] ABSTRACT: Hyper variable segment of mitochondrial 16S rDNA from different stages of laboratory reared, disease free and
acaricide susceptible Hyalomma anatolicum and Rhipicephalus (Boophilus) microplus were partially amplified, sequenced
and analyzed with the aid of the GenBank database. Thirty conserved genus specific nucleotide change were observed
in Hyalommid and Boophilid ticks. These conserved sequences were sufficient to identify embryonic stages of the
ticks. These conserved sequences at the genus level could act as biomarker for identification of ticks during
epidemiological studies of tick borne diseases, transmitted by Hyalommid and Rhipicephalid ticks.
The Indian journal of animal sciences 01/2011; 18(12-81(12)):1204-1207. · 0.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To develop a environment friendly control measure against cattle tick, Rhipicephalus (Boophilus) microplus, medicinally important plants were identified and extracts were prepared. Twelve 95% ethanolic, thirteen 50% hydroethanolic and nine hot water extracts were prepared and tested against laboratory reared homogenous colony of R. (B.) microplus. Amongst the 34 extracts, 26 extracts showed no mortality within 72 h of application while 12.0 ± 4.9% to 35.0 ± 9.6% mortality of treated ticks was recorded in other extracts. Of the effective extracts, the extract prepared from rhizome of Acorus calamus proved highly efficacious and 100% final mortality within 14 DPT was recorded. The LC85 value of the extract was determined as 11.26. In vivo experiments confirmed the efficacy of the extract up to 42%, and repeat application was required after 7 DPT. The extract was found safe and no reaction was observed when animals were treated with 50% of the concentration, which was five times of the concentration used for in vivo studies. The possibility of using the extract for the control of cattle tick is discussed.
Parasitology Research 10/2010; 108(2):361-70. · 2.85 Impact Factor