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1.
The efficacy of Metarhizium anisopliae on the control of Boophilus microplus in cattle infested naturally in the Mexican tropics was evaluated. The study was carried out on a ranch in Veracruz, Mexico. Twenty steers were randomly allocated into two groups of 10 cattle. Animals were naturally infested with B. microplus. Animals in the treated group were sprayed with M. anisopliae (strain Ma34) at a concentration of 1x10(8)conidia/ml every 15 days (four treatments). The other group remained as untreated control. Standard engorged female ticks were recorded on days 0, 1, 3, 5, 7 and 14 post-treatment. From the second application treatment (day 7) to the end of the experiment, animals in the treated group had lower tick infestation (P<0.05) with an efficacy of 40.0-91.2%. The results demonstrate the efficacy of repeated treatment with M. anisopiae (Ma34 strain) to control natural infestation of engorged female B. microplus on cattle in the Mexican tropics.  相似文献   

2.
A study was conducted in cattle experimentally infested with Psoroptes ovis to compare the prophylactic control against P. ovis provided by a long-acting injectable formulation of ivermectin to that of a commercially available injectable formulation of doramectin. Thirty Holstein steers were used. Animals were allocated by restricted randomization based on Day 0 body weight, forming six replicates of five animals each. Within each replicate, one animal was randomly allocated to one of the following treatment groups, with ivermectin and doramectin administered subcutaneously where indicated: (1) untreated controls; (2) ivermectin long-acting injectable (LAI) 630 mcg/kg, 56 days before challenge; (3) ivermectin LAI 630 mcg/kg, 42 days before challenge; (4) ivermectin LAI 630 mcg/kg, 35 days before challenge; or (5) doramectin 200 mcg/kg, 35 days before challenge. Animals were housed in individual pens 1 week prior to treatment. All animals were experimentally infested with P. ovis mites in the area between the shoulders, on the same day. Live mites were counted in scrapings from mange lesions at 2 sites on each animal 14, 21 and 28 days after challenge. Live mites were found in 33, 67 and 83% of the untreated controls on each respective evaluation. No P. ovis mites were found in steers treated with ivermectin LAI. Those animals showed lower (P < 0.05) mite counts than untreated controls on evaluations conducted 21 and 28 days after challenge. These results indicate that the ivermectin long-acting injectable formulation prevents induced infestations by P. ovis for at least 56 days after treatment. Doramectin injectable formulation, used at 200 mcg/kg, did not have a prophylactic effect 35 days after treatment.  相似文献   

3.
The efficacy of ivermectin, administered in a sustained release formulation by intraruminal pumps at approximate daily dose rates of 20, 40 and 60 micrograms/kg, was evaluated in 16 cattle against induced infestations of 3 strains of adult Amblyomma hebraeum. Engorged female ticks were mass-measured and incubated, and reproductive data recorded. There was an increase in mortality of male and female ticks compared to that of controls with increasing daily dose of ivermectin, and a decrease in the number of ticks engorging. Ticks fed on ivermectin-treated cattle had a smaller mass when engorged and laid smaller egg masses, both absolutely and as a proportion of engorged mass. Index of reproduction was reduced 100% at 60 micrograms/kg/day, greater than 99% at 40 micrograms/kg/day and 96% at 20 micrograms/kg/day. Differences occurred between the 3 strains of A. hebraeum used in the study, especially with regard to engorged mass and reproductive variables. Practical implications of the application of sustained release ivermectin for the control of A. hebraeum, specifically with reference to heartwater (Cowdria ruminantium), are discussed.  相似文献   

4.
Fifteen controlled field trials were conducted to evaluate the efficacy against gastrointestinal nematodes and safety of ivermectin when applied topically to cattle in Australia. Three hundred and fifty-one cattle received ivermectin, and 88 were untreated controls. The trials were conducted in 3 States and included a variety of cattle breeds and environmental conditions. Faecal samples were collected before treatment and 11 to 14 days after treatment for nematode egg counts. Data from these trials show that under Australian conditions, ivermectin applied along the mid line of the back from the withers to the sacral region at a dose rate of 500 mcg/kg body weight, effectively controlled gastrointestinal nematode infections, and did not produce unacceptable adverse reactions in the animals.  相似文献   

5.
SUMMARY Stall and field trials with cattle infested with various acaricide-resistant strains of cattle tick, have demonstrated the potential of ivermectin as a systemic tickicide. A dosage of 200 μg/kg, administered subcutaneously to animals naturally infested in the field, gave satisfactory tick control for 21 days, after an initial lag period of 2 days immediately following treatment, during which significant numbers of ticks survived. Daily subcutaneous treatments, administered so as to simulate slow release, indicated that a dosage of 15 μg/skg/day should give complete tick control if the chemical could be released continuously from a subcutaneous implant. The potency of ivermectin, assessed by in vitro tests against engorged adults, suggests that the tickicidal activity could be associated with the parent compound per se rather than a metabolite.  相似文献   

6.
The efficacy of topically administered ivermectin against Chorioptes bovis and Sarcoptes scabiei var bovis on cattle was evaluated in five studies involving a total of 68 cattle. Treatment with ivermectin solution at a dose rate of 500 micrograms/kg bodyweight topically once was fully effective against C bovis and S scabiei when applied to healthy skin. Efficacy against S scabiei was impaired when the formulation was applied over areas of severe lesions caused by this parasite, presumably due to reduced absorption of ivermectin.  相似文献   

7.
Three field trials were conducted over 12 months to assess the pathogenicity of Metarhizium anisopliae to parasitic stages of Rhipicephalus (Boophilus) microplus on dairy heifers under different environmental conditions. Two isolates were selected based on their high optimal growth temperature (30 degrees C), good spore production characteristics and ability to quickly kill adult engorged ticks in the laboratory. Spores were formulated in an oil emulsion and applied using a motor driven spray unit. Surface temperatures of selected animals were monitored, as were the ambient temperature and relative humidity. Unengorged ticks sampled from each animal immediately after treatment were incubated in the laboratory to assess the efficacy of the formulation and application. Egg production by engorged ticks collected in the first 3 days after treatment was monitored. Side counts of standard adult female ticks were conducted daily, before and after treatment to assess the performance of the fungus against all tick stages on the animals. In each trial the formulation rapidly caused 100% mortality in unengorged ticks that were removed from cattle and cultured in the laboratory. A significant reduction in egg production was recorded for engorged ticks collected in the 3 days post-treatment. However, there was little effect of the formulation on the survival of ticks on cattle, indicating that there is an interaction between the environment of the ticks on the cattle and the biopesticide, which reduces its efficacy against ticks.  相似文献   

8.
Leaves of Palicourea marcgravii were extracted successively with hexane, ethyl acetate and ethanol in order to evaluate their acaricidal activity on larvae and adult stages of the cattle tick Rhipicephalus (Boophilus) microplus. The ethyl acetate extract showed the highest bioactivity of the tested extracts, which contained 0.12% monofluoroacetic acid. On engorged female, the ethyl acetate extract showed a lethal concentration 50% - LC(50)=30.08 mg ml(-1), inhibitory concentration 50% - IC(50)=5.79 mg ml(-1) and lethal time 50% - LT(50)=4.72 days; 100% reproduction was controlled at concentrations of 50 mg ml(-1) and on larvae the ethyl acetate extract showed a LC(50)=2.46 mg ml(-1). No alkaloids were detected in any of the extracts. This is the first report on the acaricidal activity of P. marcgravii extracts against R. microplus as well as the acaricidal properties of a plant species containing monofluoroacetic acid.  相似文献   

9.
We document the presence of a Rhipicephalus microplus tick population resistant to acaricides (organophosphates (OP), synthetic pyrethroids (SP), amitraz) and macrocyclic lactones (ML) (ivermectin). Engorged females of R. microplus were collected from a cattle farm in Veracruz, Mexico, to evaluate acaricide and ivermectin resistance. The modified larval packet test (LPT) was used to detect OP (chlorpiriphos and diazinon) and SP (flumethrin, deltamethrin and cypermethrin) resistance and the larval immersion test (LIT) to detect resistance to amitraz and ivermectin. Both, LPT and LIT were performed twice at different times with different collected samples. Mortality data with ivermectin were subjected to probit analysis to obtain lethal concentrations and resistance ratios (RR) using an ivermectin-susceptible strain (Deutch) as a reference. The R. microplus population showed resistance to all acaricides tested, with different mortalities at the discriminate dose: chlorpiriphos (1%), diazinon (24.2%), flumethrin (92.8%), deltamethrin (94.2%), cypermethrin (98.0%) and amitraz (1.5%). The studied tick population also showed resistance to ivermectin with a resistance ratio at 99% of 9.58 and 6.52 in the first and second evaluation, respectively. We report for the first time a R. microplus population in Mexico with different levels of resistance to OP, SP, amidines (Am) and ivermectin. The uncontrolled use of these products in the study area may promote the complete failure of tick control within a short period of time.  相似文献   

10.
The therapeutic efficacies of ivermectin (subcutaneous injection) and eprinomectin (topical treatment) given at two different dosage levels to goats naturally infested with Amblyomma parvum were assessed. Treatments included subcutaneous injection of ivermectin at 0.2 and 0.4mg/kg and extra-label pour-on administration of eprinomectin at 0.5 and 1mg/kgb.w. Ivermectin and eprinomectin failed to control Amblyomma parvum on goats. Treatment with ivermectin resulted in a low number of engorged female ticks in relation to untreated control goats and, at the highest dose rate (0.4mg/kg), the female engorgement weights were significantly lower and the pre-oviposition period significantly longer than those observed in ticks recovered from untreated control goats. The tick efficacy assessment was complemented in a separate group of tick-free goats with a pharmacokinetic characterization of eprinomectin (topically administered at 0.5, 1.0 and 1.5mg/kg) and ivermectin (subcutaneous treatment given at (0.2 and 0.4mg/kg) in goats. Heparinized blood samples were taken between 0 and 21 days post-treatment. Higher and more persistent drug plasma concentrations were recovered after the subcutaneous treatment with ivermectin compared to those obtained for eprinomectin topically administered. The understanding of the relationship among the pattern of drug absorption, the kinetic disposition and the resultant clinical efficacy is relevant to improve the poor performance observed for ivermectin and eprinomectin against A. parvum on goats.  相似文献   

11.
The efficacy of ivermectin delivered by an orally administered prototype sustained-release bolus over approximately 90 days was evaluated against natural infestations of five African tick species. Twenty cattle, allocated by restricted randomization based on counts of standard Boophilus decoloratus, were allocated to two groups and were either given an ivermectin bolus or designated as non-medicated controls. All cattle grazed a single pasture of native grasses for 20-40 days before treatment and until trial termination. Starting on Days 27, 40, 68 and 82 after bolus administration, four replicates were confined to individual tick-collection stanchions for 4 to 5-day periods. Ticks recovered from these cattle were counted by species, sex, and stage and degree of repletion; engorged females were weighed and incubated to determine the number which oviposited. For the other replicates, half-body counts of adult ticks (classified by species, sex and degree of repletion by females) were made at 1- and 2-week intervals through Day 90. Among replicates confined to stanchions periodically, fewer (P less than 0.05) engorged adult female B. decoloratus, Hyalomma spp., Rhipicephalus appendiculatus and Rhipicephalus evertsi evertsi were collected from bolus-treated cattle than from controls. Numbers of engorged adult female Amblyomma hebraeum were reduced, but differences were not statistically significant (P greater than 0.10). Among cattle maintained continuously on pasture, tick numbers were reduced on the ivermectin-treated groups. A significant (P less than 0.05) treatment by linear time effect was seen for all adult ticks counted except R. appendiculatus. A significant (P less than 0.05) treatment by quadratic time effect was seen for A. hebraeum, B. decoloratus and R. evertsi evertsi, and overall treatment differences were significantly different (P less than 0.05) for these species. The differences tended to increase with time. Except for Boophilus, reductions in tick numbers on treated animals relative to controls were not readily apparent. There were no adverse reactions attributable to ivermectin treatment or the presence of the bolus. Each treated animal retained its bolus throughout the trial, based on metal detection.  相似文献   

12.
The pharmacokinetic behaviour of ivermectin was investigated in adult llamas (Lama glama) by using high performance liquid chromatography with a lower limit of quantification of 2 ng/ml to measure its concentration in serum. Llamas were treated with one of three commercial formulations (injectable, pour-on or oral paste) at dosages recommended by the manufacturer, or with an experimental injectable sustained-release formulation. In five llamas given 1 per cent ivermectin subcutaneously at 200 microg/kg, the median peak serum concentration (Cmax) was 3 ng/ml and the area under the serum concentration-time curve (AUC) was 13.5 ng x day/ml. In six llamas treated topically with 0.5 per cent ivermedin pour-on at 500 microg/kg, Cmax was 2.5 ng/ml or less and the AUC was 7.75 ng x day/ml or less. In seven llamas with measurable concentrations of ivermedin, the median times to peak serum concentration (tmax) were six days after subcutaneous injection and seven days after treatment with the pour-on formulation. In six llamas, the serum concentration of ivermectin remained less than 2 ng/ml for 124 hours after treatment with a 1.87 per cent oral paste at 200 microg/kg. In five llamas treated subcutaneously with 25 per cent ivermectin sustained-release microspheres at 1500 microg/kg, the median Cmax was 5 ng/ml and the median AUC was 224 ng x day/ml.  相似文献   

13.
Three synthetic peptides (SBm4912, SBm7462 and SBm19733), derived from the Bm86 glycoprotein from Boophilus microplus gut, were constructed and used to immunize cattle from a tick-free area. The immunized animals received three subcutaneous doses of the peptides, with saponin as adjuvant, at 30-day intervals. The immune response was evaluated by IgG elicited against the peptides by the detection of anti-Bm86 specific antibodies in situ and by Western blotting analysis. After tick challenge, reduction in the number, weight and oviposition capacity of engorged females was observed in the tick population that had fed on immunized animals. The results pointed a high efficacy (81.05%) for the SBm7462 synthetic peptide in relation to the others (p<0.01), demonstrating the efficiency of the immune response elicited by synthetic peptides to control the cattle tick B. microplus.  相似文献   

14.
Dermatobia hominis, the tropical warble fly, is one of the most important ectoparasites of cattle in Latin America. The results of five trials conducted in Paraguay, Brazil and Colombia showed that ivermectin administered subcutaneously at a dose level of 200 mcg/kg body weight was highly effective against the three larval stages of D. hominis in cattle.  相似文献   

15.
The bovine spirochete, Borrelia theileri, was detected in Giemsastained blood smears from a splenectomized calf 17 days after exposure to a laboratory colony of the tropical cattle tick, Boophilus microplus. Spirochetes were detected in the hemolymph and ovary of all engorged female ticks examined, indicating a high infection rate in this tick colony. Spirochetes were detected in a 2nd splenectomized calf 15 days after exposure to the larval offspring of ticks from the 1st calf. The only observable effect of infection in the 2 calves was a maximum rectal temperature increase to 40.2 C, which coincided with the first detectable parasitemia. The tick colony did not have any adverse effects, despite extensive multiplication of spirochetes in their tissues.  相似文献   

16.
Ivermectin, either as an injectable or topical formulation, is used widely to control parasites in New Zealand cattle. These formulations have been well documented as having high efficacy against the major nematode species which infect tattle(1)(2)(3)(4), although the efficacy against adult Cooperia oncophora is reported to be 95%(5). This is considered to be one of the doselimiting species. There have been two reports of lower than expected efficacy of the topical formulation against Cooperia spp. in cattle. In a slaughter trial, Bisset et al. (6) found that ivermectin applied topically at the recommended dose rate of 500 𝛍g/kg failed to achieve a statistically significant reduction in the burden of Cooperia spp. worms compared with untreated calves. The geometric mean of adult Cooperia spp. worms present in the treated calves was 5788 compared with 7524 present in the untreated calves. This reduced efficacy was not attributed to acquired anthelmintic resistance because ivermectin had not been used on the farm previously. In Australia, Eagleson and Allertonc(7) found in controlled field trials that ivermectin applied topically at 500 𝛍g/kg ranged in efficiency in reducing faecal egg counts from 80.7% to 100% ; four out of 13 trials achieving less than 90% and a further four were in the range of 90–95% reduction. Larvae obtained from the faeces of ivermectin-treated cattle on days 11–14 after treatment were predominantly Cooperia spp.  相似文献   

17.
The present work aimed to evaluate the endectocide activity of a new injectable long-action formulation, containing ivermectin (IVM) and abamectin (ABA). In each one of the four experiments performed, the following groups were formed: group I: 2.25% IVM (450 microg/kg)+1.25% ABA (250 microg/kg), group II: 3.15% IVM (630 microg/kg) and group III: control. Eighteen bovine naturally infected by gastrointestinal nematoda were selected for anthelmintic evaluation and necropsied on posttreatment day (PTD) 14 to estimate the total parasitic burden. For the Rhipicephalus (Boophilus) microplus field trial, 30 bovine were selected by means of counts of semi-engorged R. (B.) microplus and the therapeutic and residual efficacy evaluated by tick counts on PTDs 1, 3, 7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84 and 91. In the stall test, 15 calves were artificially infested with 5000 R. (B.) microplus (Mozzo strain) larvae three times a week and daily collections of all the engorged female ticks detached from each calf were performed until the PTD 80. Forty bovine naturally infected with Dermatobia hominis larvae were selected and the number of larvae was counted by visual and tactile inspection on PTDs 3, 7, 14, 28, 35, 49, 63, 77, 91 and 105. In this trial, a formulation containing 1% doramectin (200 microg/kg) was also used. IVM+ABA formulation and 3.15% IVM eliminated four of the eight species of nematode identified. The anthelmintic efficacy of the avermectins association against Haemonchus placei, Cooperia spatulata and C. punctata was 89.64%, 98.84% and 97.69%, while 3.15% IVM achieved 30.98%, 84.79% and 75.56%, respectively. The two formulations evaluated showed reduced acaricide action on the PTD 1 and 3, reaching high efficacy percentages from PTD 14 onward. The IVM+ABA showed efficacy above 95% in the period between PTDs 21 and 49. In the stall test, it observed no difference (P>0.05) between the two formulations regarding the R. (B.) microplus counts during the entire evaluation period. IVM+ABA reduced the number of ticks from the PTD 1 to 77 (P<0.05) and 3.15% IVM reduced (P<0.05) the tick number from PTD 4 up to PTD 80. The three endectocides showed no difference (P>0.05) regarding the number of D. hominis larvae and prevented this parasite reestablishment until PTD 105. These results indicate that the IVM+ABA association showed higher anthelmintic activity and similar efficacy against arthropods to the formulation containing 3.15% IVM.  相似文献   

18.
As in most parts of the world where the cattle tick Boophilus microplus is established, resistance of ticks to acaricides occurs in New Caledonia. In order to implement laboratory resistance tests on larvae, engorged females collected in suspected farms are necessary. Investigations on the detachment schedule of the engorged females were conducted to explain certain field situations such as the lack or scarcity of engorged females on highly infested cattle driven from the pasture to the pen in the morning. Three experiments on Charolais steers naturally infested on pastures showed that: (1) engorged female burdens at sunrise are similar whether the steers spend the night in pasture or in a pen; (2) compared with steers maintained in a pen, morning detachment of females increases when the steers stay on the pasture or move from the pasture to the pen; (3) detachment rhythm of engorged females on steers staying the morning in a pen, is not influenced by feeding activity or exposition of steers to sun; (4) detachment occurs earlier for females attached on anatomical sites exposed to sun, and earlier from these sites for the steers in pasture or walking than for steers in a pen.  相似文献   

19.
The purpose of this study was to determine the effect of amitraz selection pressure on the development of resistance in field populations of Boophilus microplus in the Mexican tropics. Three farms (FA(1), FA(2) and FA(3)) in Yucatan, Mexico, were selected in this study. Amitraz was applied as a whole body sprays to all cattle on each farm for tick control once monthly for 15 months. From each farm, 20-30 B. microplus engorged females were collected every 3 months. The modified larval immersion test was used to test susceptibility of B. microplus to amitraz. Larvae were exposed to serial dilutions of amitraz. Probit analysis was used to determine lethal dose at 50% mortality and associated 95% confidence limits. The resistance factors found in the three farms during the 15 months of amitraz selection pressure were FA(1) (1, 2, 4, 4 and 13), FA(2) (1, 6, 23, 21 and 22) and FA(3) (2, 13, 2, 6 and 6). It is concluded that amitraz selection pressure on field populations of B. microplus increased the resistance level in all populations studied in the Mexican tropics.  相似文献   

20.
A cross-sectional study was carried out in order to investigate the association between management risk factors and the prevalence of organophosphate (OP) and synthetic pyrethroid (SP) resistance in Boophilus microplus ticks in Yucatan State, Mexico. Ninety-eight cattle ranches were randomly selected and a sample of 20-30 engorged female B. microplus ticks was collected at each. The modified larvae packet test was used to detect OP and SP tick resistance. A questionnaire was administered on each ranch. For risk factors, four reference types of response were used: Tuxpan (resistant to coumaphos, chlorfenvinphos and diazinon), Parkhurst (resistant to flumethrin, deltamethrin and cypermethrin), Lamington (resistant to flumethrin in absence of deltamethrin and cypermethrin) and Marmor (resistant to flumethrin and cypermethrin in absence of flumethrin). A primary screening was performed using 2 x 2 contingency tables of exposure variables. All variables with p < or = 0.20 were analyzed by a logistic regression. The prevalence of B. microplus resistance to OP and SP groups were 83.70% and 66.32%, respectively. The prevalence for a single chemical compound was: diazinon (80.60%), coumaphos (45.90%), chlorfenvinphos (35.70%), flumethrin (63.28%), deltamethrin (61.22%), and cypermethrin (59.18%). The prevalence type of response was: Tuxpan (34.16%), Parkhurst (58.16%), Lamington (4.08%), and Marmor (4.08%). The use of a different tick control program was the risk management factor associated with the Parkhurst type of response. It is concluded that the prevalence of cattle ranches with B. microplus resistant to OPs and SPs in Yucatan, Mexico, is a current problem, and a treatment interval of > or =6 times/year and use of a tick control program (macrocyclic lactones and pasture burn) different from standard recommended programs are risk factors associated with the Parkhurst type of response.  相似文献   

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