RESUMEN
The acaricidal effect of 14 strains of Metarhizium anisopliae sensu lato isolated from soil of livestock farms in the Mexican tropics was evaluated against larvae and engorged females, and during the laying and hatching of eggs of Rhipicephalus microplus (Ixodida: Ixodidae). For each fungal strain, the larvae mortality percentage was evaluated through a larval immersion test, while the reproductive efficiency indices in engorged females were measured using adult immersion tests at a dose of 1 × 108 conidia/ml. All strains of M. anisopliae (s.l.) proved to be highly effective against R. microplus larvae (66-100%) and engorged females (100%). The strains also showed a good effect in inhibiting egg laying (16.45-56.38%) and a moderate effect in decreasing egg hatching (5.24-32.68%). Two strains demonstrated to be effective against all development phases of R. microplus in an integrated manner.
Asunto(s)
Metarhizium , Rhipicephalus , Animales , Femenino , Rhipicephalus/microbiología , Ganado , Larva/microbiología , Control Biológico de Vectores , ReproducciónRESUMEN
This is the first study to empirically evaluate the mortality of Amblyomma mixtum larvae caused by native entomopathogenic fungi (EPF) from cattle farm soils and the impact of the physicochemical conditions of those soils on the ability of EPF to kill ticks. The efficacy of 25 EPF strains isolated from cattle farms soils in Veracruz, Mexico, against A. mixtum ticks was evaluated using a larval immersion test. Physicochemical analyses of the soils where the EPF were isolated were carried out, and the results were correlated with the obtained mortality. The MaV25 strain showed a mortality of 36.55% (P < 0.05), followed by MaV57 with 27.30%, MaV08 with 26.21%, and MaV31 with 24.32% (P < 0.05). Nitrogen and potassium are nutritional components of soils that seem to be associated with mortality caused by the evaluated fungal strains. This is the first study in Mexico where the effect of EPF against A. mixtum is evaluated and also is the first study in the world that uses native strains from livestock soils against larvae of this tick. It is necessary to determine the virulence characteristics of EPF on A. mixtum to improve knowledge of fungus-tick interactions (Metarhizium anisopliae-A. mixtum).
Asunto(s)
Beauveria , Garrapatas , Bovinos , Animales , Granjas , Amblyomma , Control Biológico de Vectores/métodos , México , Larva/microbiología , SueloRESUMEN
Polyphenolic compounds (PCs) have been proposed as one of the most bioactive group of secondary metabolites occurring in nature and have been associated to anthelmintic (AH)-like activity of plants against cattle nematodes. However, little is known regarding their synergetic / antagonistic interactions. This study assessed the in vitro AH-like activity of commercial PCs: quercetin, caffeic acid, rutin and coumarin, and their combinations against the egg hatching and larval exsheathment of Cooperia punctata; one of the most prevalent nematodes affecting grazing cattle in tropical regions. The molecules selected for the in vitro analysis were identified as bioactive phytochemicals of plants through bio-guided fractionation in previous studies. To estimate mean effective concentrations (EC50) five increasing concentrations were used for both Egg hatching inhibition assay (EHIA) and larval exsheathment inhibition assay (LEIA) (0.6-9.8 mg mL-1 and 0.15-2.4 mg mL-1, respectively). From the four molecules, only rutin did not affect egg hatching; while quercetin, showed no bioactivity against eggs or larvae (P > 0.766 and P > 0.621, respectively). Best-fit EC50 estimated through the EHIA was considered for PCs classification as bioactive (coumarin and caffeic acid) and non-bioactive (quercetin and rutin). Phytochemical interactions were subsequently assessed combining bioactive:non-bioactive PCs (8:2 ratio), and the nature of their interaction was classified using the fractional inhibitory concentration index (FICindex). Combinations had a highly synergistic interaction against larval exsheathment (FICindex < 0.5) except for coumarin:rutin against egg hatching (FICindex> 0.5). Quercetin and rutin acted as PCs AH-like activity enhancers, reducing EC50 of bioactive molecules in a range of 43%-64% and 68%-83% for EHIA and LEIA, respectively. A linear relationship between low molecular weight of molecules and ovicidal activity was observed; where, molecules with lower molecular weight displayed better-fit EC50 for ovicidal activity. Furthermore, coumarin and caffeic acid bioactivity against free-living stages of C. punctata makes them suitable candidates as markers for anthelmintic-like activity in bioactive forages. Combinations used through this investigation showed a potent anthelmintic-like activity against free-living forms of C. punctata, representing a first step towards the identification of promising alternatives for nematode control.
Asunto(s)
Nematodos/efectos de los fármacos , Polifenoles/farmacología , Animales , Antihelmínticos , Larva/efectos de los fármacos , Estructura Molecular , Óvulo/efectos de los fármacos , Polifenoles/químicaRESUMEN
The acaricidal effects of 55 strains of Metarhizium anisopliae (Metschnikoff) Sorokin, 1883 (Hypocreales: Clavicipitaceae) isolated from paddocks of cattle farms were evaluated in two Rhipicephalus microplus (Canestrini 1887) (Ixodida: Ixodidae) populations, of which one was multi-resistant and one was susceptible to chemical acaricides. Percentage mortality and reproductive efficiency indices in R. microplus were evaluated by adult immersion tests at a dose of 1 × 108 conidia/mL for each fungal strain. Some strains were selected to calculate lethal concentrations to kill 50% (LC50 ) and 99% (LC99 ) of engorged ticks. Strains MaV22, MaV26 and MaV55 induced 100% mortality in R. microplus on day 14. Strains MaV05, MaV09 and MaV22 caused mortality of >90% from day 12 onward in both tick populations. The most effective acaricidal fungal strain, MaV55, inhibited egg laying by 54.86 and 55.86% in acaricide-resistant and -susceptible R. microplus populations, respectively. None of the fungal strains had statistically significant effects on larval hatching. In conclusion, nine strains of M. anisopliae demonstrated high acaricidal effects against R. microplus and reduced its egg laying. No differences in acaricidal effects were observed between the two populations of ticks tested.
Asunto(s)
Enfermedades de los Bovinos/prevención & control , Metarhizium/fisiología , Control Biológico de Vectores , Rhipicephalus/microbiología , Infestaciones por Garrapatas/veterinaria , Animales , Bovinos , Enfermedades de los Bovinos/parasitología , Femenino , Larva/crecimiento & desarrollo , Larva/microbiología , Masculino , Metarhizium/genética , México , Rhipicephalus/crecimiento & desarrollo , Rhipicephalus/fisiología , Control de Ácaros y Garrapatas , Infestaciones por Garrapatas/parasitología , Infestaciones por Garrapatas/prevención & controlRESUMEN
This study reports the percentage of cattle farms with ivermectin (IVM) resistant gastrointestinal nematodes (GINs) in Veracruz, Mexico, and identifies the GIN genera involved in the resistances. It also describes management practices of anthelmintic (AH) use on the surveyed farms. Twenty-one farms were assessed by means of the faecal egg count reduction test using the McMaster technique. Only two farms had GIN populations susceptible to IVM (9.5%). The proportion of farms with IVM resistant GIN was 71.4% (15/21). Seven of these farms had less than 80% egg count reductions. Haemonchus and Cooperia were the genera most commonly found in the resistant populations, followed by Oesophagostomum. Inappropriate AH treatment practices were identified from the completed questionnaires. Further management practices such as selective treatment and quarantine treatments are proposed to further reduce the spread of IVM resistance between farms.
Asunto(s)
Enfermedades de los Bovinos/parasitología , Resistencia a Medicamentos , Enfermedades Gastrointestinales/veterinaria , Ivermectina/farmacología , Nematodos/efectos de los fármacos , Infecciones por Nematodos/veterinaria , Animales , Antihelmínticos/farmacología , Bovinos , Enfermedades de los Bovinos/epidemiología , Recolección de Datos , Enfermedades Gastrointestinales/epidemiología , Enfermedades Gastrointestinales/parasitología , México/epidemiología , Infecciones por Nematodos/epidemiología , Infecciones por Nematodos/parasitología , Encuestas y CuestionariosRESUMEN
Sheep have been suggested to use their senses to perceive plant properties and associate their intake with consequences after ingestion. However, sheep with browsing experience do not seem to select against tannin-rich browsing materials in cafeteria trials. Thus, the objective of the present study was to evaluate the relationship between the chemical composition, selectivity index (SI), preference and intake rate (IR) of tannin-containing forage trees offered to sheep in cafeteria experiments. Four trees were selected for their condensed tannin content and their varying biological activities. Havardia albicans (high biological activity), Leucaena leucocephala (medium biological activity), Acacia gaumeri (low biological activity) and Brosimum alicastrum (very low biological activity) were used in this study. Ten hair sheep (23.7kg±1.43LW) with eight months of browsing experience in native vegetation were used in this study. Polyethylene glycol (PEG 3600MW) was administered to five sheep during all experiments. In experiment 1, fresh foliage from all trees was offered ad libitum for 4h. In experiment 2, B. alicastrum was withdrawn and the preference was determined again. The forage preference in experiment 1 was A. gaumeri (14.77gDM/kgLW)>B. alicastrum (11.77gDM/kgLW)>H. albicans (3.71gDM/kgLW)=L. leucocephala (1.87gDM/kgLW) (P<0.05). The preference in experiment 2 was A. gaumeri>H. albicans=L. leucocephala. PEG administration had no effect on the preference or IR. The intake rate seemed to have been affected by the plant density. Moreover, fiber compounds were found to be better predictors of DM intake than polyphenolic compounds at levels typically found in the evaluated forages. It was concluded that tannins and PEG did not modify the preferences of sheep in cafeteria trials. Thus, tannins are not involved in the preference regulation of animals with browsing experience.
Asunto(s)
Alimentación Animal , Ingestión de Alimentos/fisiología , Conducta Alimentaria/fisiología , Preferencias Alimentarias , Ovinos/fisiología , Taninos/metabolismo , Animales , Conducta de Elección/efectos de los fármacos , Femenino , Polietilenglicoles/farmacología , Ovinos/psicología , Taninos/antagonistas & inhibidores , Taninos/químicaRESUMEN
The objectives of the present study were: (1) to report the percentage of cattle farms with gastrointestinal nematodes (GINs) resistant to levamisole in Veracruz, Mexico, (2) to identify the genera of GINs involved in resistance, and (3) to identify factors associated with these resistances. The faecal egg count reduction test (McMaster technique) was used to detect the presence of resistant GINs. A questionnaire was given to owners to understand the history of anthelmintic use. The percentage of cattle farms with GINs resistant to levamisole was 36.4% (4/11). The percentage of faecal egg count reduction on resistant farms was 91%, 82%, 42% and 88%. A similar number of cattle farms (4/11) were identified as potentially having levamisole resistance. Only three farms had GIN populations susceptible to levamisole. Cooperia spp. was the genus most commonly found to be resistant, followed by Haemonchus spp., Ostertagia spp. and Oesophagostomum spp. No factors were identified that influenced the presence of GIN resistance. However, there were identified inappropriate anthelmintic practices in cattle farms that should be improved. None of the farmers weighed their animals in order to dose them correctly with anthelmintics. Six cattle farms (54.5%) applied anthelmintics to new arriving animals. This is the first report of levamisole resistant GINs in Mexico. Improving the use of anthelmintics and measures of quarantine for infected cattle will help control the spread of resistance.
Asunto(s)
Antihelmínticos/uso terapéutico , Enfermedades de los Bovinos/epidemiología , Resistencia a Medicamentos , Levamisol/uso terapéutico , Trichostrongyloidea/efectos de los fármacos , Tricostrongiloidiasis/veterinaria , Animales , Bovinos , Enfermedades de los Bovinos/tratamiento farmacológico , Enfermedades de los Bovinos/parasitología , Heces/parasitología , Tracto Gastrointestinal/parasitología , Haemonchus/efectos de los fármacos , Haemonchus/aislamiento & purificación , México/epidemiología , Ostertagia/efectos de los fármacos , Ostertagia/aislamiento & purificación , Recuento de Huevos de Parásitos/veterinaria , Trichostrongyloidea/aislamiento & purificación , Tricostrongiloidiasis/tratamiento farmacológico , Tricostrongiloidiasis/epidemiología , Tricostrongiloidiasis/parasitologíaRESUMEN
The objectives of the present study were: (i) to identify the frequency of cattle farms with a cohabitation of Amblyomma cajennense and Rhipicephalus microplus, (ii) to determine the status of susceptibility or resistance to acaricides used in Veracruz, Mexico, on A. cajennense populations and (iii) to identify factors associated with A. cajennense resistant to acaricides. Fifty farms were visited to determine the presence of ticks (A. cajennense and R. microplus) and to collect engorged A. cajennense individuals. From these, 24 A. cajennense populations were evaluated in resistance bioassays using discriminating doses of acaricides. The acaricides tested were organophosphates (chlorpiriphos, coumaphos and diazinon), pyrethroids (flumethrin, deltamethrin and cypermethrin), amidines (amitraz) and fipronil (a broad spectrum N-phenylpyrazole insecticide). A. cajennense infesting bovines were identified in 86% (43/50) of the farms visited, and 100% of the farms sampled (43/43) had cohabitation between R. microplus and A. cajennense. Of the farm owners or managers surveyed, 87.5% could not distinguish the morphological difference between tick genera. Populations of A. cajennense were 100%, 91.7% and 12.5% resistant to diazinon, coumaphos and chlorpyriphos (organophosphates), respectively, and 12.5% to amitraz, as were those susceptible to flumethrin and fipronil. In conclusions, populations of A. cajennense showed a high frequency of resistance to the organophosphates tested and to amitraz. Factors associated with the resistance to acaricides in A. cajennense were not identified.
Asunto(s)
Acaricidas/farmacología , Resistencia a los Insecticidas , Ixodidae/efectos de los fármacos , Infestaciones por Garrapatas/veterinaria , Crianza de Animales Domésticos , Animales , Bovinos , Enfermedades de los Bovinos/epidemiología , Enfermedades de los Bovinos/parasitología , Recolección de Datos , Humanos , México/epidemiología , Factores de Riesgo , Encuestas y Cuestionarios , Infestaciones por Garrapatas/epidemiología , Infestaciones por Garrapatas/parasitología , Clima TropicalRESUMEN
The objectives of the present study were to (1) determine the status of resistance or susceptibility to ivermectin (IVM) in Rhipicephalus microplus tick populations in Veracruz, Mexico, (2) determine the level of resistance (resistance ratios [RR] and lethal concentrations for 50% [LC(50)] and 99% [LC(99)]) mortality in each R. microplus population, and (3) identify factors associated with resistance. Populations of R. microplus were sampled from 53 cattle farms to evaluate their resistance using the larval immersion test. Mortality data were subjected to probit analysis to calculate LC(50) and LC(99). Resistance ratios were calculated in relation to a susceptible reference strain. A logistic regression model was used to evaluate the relation between resistance and possible associated factors. Thirteen tick populations were susceptible to ivermectin, eighteen had incipient resistance and twenty-two had significant resistance. RR(50) of the susceptible tick populations varied from 0.59 to 1.07. The populations that showed the highest level of resistance were: ANTE (RR(50)=8.21; RR(99)=46.0), PALO (RR(50)=6.25; RR(99)=35.47), P.VIE (RR(50)=5.89; RR(99)=180.3), AURO (RR(50)=5.36; RR(99)=13.82 and CEDR (RR(50)=4.11; RR(99)=26.47). Cattle farms that used macrocyclic lactones ≥ 4 times per year were more likely to develop R. microplus resistant to ivermectin (OR=13.0; p=0.0028). In conclusion, more than two-thirds of the farms sampled in Veracruz, Mexico, showed some level of ivermectin-resistant R. microplus populations and the number of ML applications per year is factor associated with the resistance of R. microplus to IVM.
Asunto(s)
Acaricidas/farmacología , Enfermedades de los Bovinos/parasitología , Resistencia a Medicamentos , Ivermectina/farmacología , Rhipicephalus/efectos de los fármacos , Infestaciones por Garrapatas/veterinaria , Animales , Antiparasitarios/farmacología , Bioensayo , Bovinos , Enfermedades de los Bovinos/epidemiología , Enfermedades de los Bovinos/prevención & control , Femenino , Genotipo , Lactonas/farmacología , Dosificación Letal Mediana , Modelos Logísticos , Compuestos Macrocíclicos/farmacología , México/epidemiología , Infestaciones por Garrapatas/epidemiología , Infestaciones por Garrapatas/parasitología , Infestaciones por Garrapatas/prevención & controlRESUMEN
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.
Asunto(s)
Acaricidas/farmacología , Enfermedades de los Bovinos/parasitología , Ivermectina/farmacología , Rhipicephalus/efectos de los fármacos , Infestaciones por Garrapatas/veterinaria , Crianza de Animales Domésticos , Animales , Bovinos , Enfermedades de los Bovinos/epidemiología , Femenino , Resistencia a los Insecticidas , Larva/efectos de los fármacos , Larva/crecimiento & desarrollo , México/epidemiología , Organofosfatos/farmacología , Pruebas de Sensibilidad Parasitaria/veterinaria , Piretrinas/farmacología , Rhipicephalus/crecimiento & desarrollo , Control de Ácaros y Garrapatas , Infestaciones por Garrapatas/epidemiología , Infestaciones por Garrapatas/parasitología , Infestaciones por Garrapatas/prevención & control , Toluidinas/farmacologíaRESUMEN
The present trial aimed at comparing the sensitivity of two in vitro methods, i.e. the larval migration inhibition assay (LMIA) and the larval exsheathment inhibition assay (LEIA), to evaluate the anthelmintic (AH) properties of tannin-rich plant extracts against Haemonchus contortus infective larvae. The two assays were applied on the same batch of H. contortus infective larvae exposed to water/acetonic extracts obtained from four tropical plants with different tannin contents: Acacia gaumeri, Brosimum alicastrum, Havardia albicans and Leucaena leucocephala. Increasing concentrations (0, 75, 150, 300, 600, 1200 µg/ml PBS) of lyophilized extracts were used in both in vitro assays. A general lineal model test was used to determine the dose-effect in the LMIA or the difference in the percentage of exsheathed larvae between the respective control and treated groups. The LMIA showed a dose-dependent AH effect for H. albicans (P<0.001) and A. gaumeri (P<0.05), but not for L. leucocephala and B. alicastrum. In contrast, the exsheathment process was significantly affected by all doses of H. albicans and A. gaumeri extracts and a significant dose-dependent effect was found for B. alicastrum and L. leucocephala. Calculation of lethal dose (LD) was possible with LEIA using B. alicastrum and L. leucocephala but not with H. albicans and A. gaumeri as the lowest tested concentration was achieving more than 50% inhibition. Calculation of LD with the LMIA results was not feasible. These results suggest that tannin-rich plant extracts are more potent inhibitors of the exsheathment of H. contortus L(3) larvae than their motility. This information underlines the difference of sensitivity between methodological procedures to evaluate the AH properties of plant extracts on the same nematode stage.
Asunto(s)
Haemonchus/efectos de los fármacos , Extractos Vegetales/farmacología , Taninos/química , Animales , Relación Dosis-Respuesta a Droga , Larva/efectos de los fármacos , Dosificación Letal Mediana , Locomoción/efectos de los fármacos , Extractos Vegetales/química , Sensibilidad y EspecificidadRESUMEN
The objectives of this study were to evaluate the in vitro acaricidal effects of lyophilized extracts of four tannin rich plants (Acacia pennatula, Piscidia piscipula, Leucaena leucocephala and Lysiloma latisiliquum) against diverse stages of Rhipicephalus (Boophilus) microplus, and to asses whether tannins were involved in the acaricidal effect using polyethylene glycol (PEG) to block tannins. Larval immersion (LIT) and adult immersion (AIT) tests were used to evaluate the acaricidal effect of each of the lyophilized extracts against larval and adult stages of R. microplus respectively. Larvae and adult ticks were exposed to increasing concentrations of each plant extract (0, 1200, 2400, 4800, 9600 and 19,200 µg ml(-1)) for 10 min. Larval mortality was recorded at 48 h post-incubation. Adult mortality was recorded daily over 14 days, at which point their reproductive efficiency was evaluated. PEG was added to the extracts to verify whether tannins were involved in the acaricidal effect. The effect on egg laying inhibition and larval mortality was analyzed using the GLM procedure in SAS. A Kruskal-Wallis test was used to assess the effect of PEG on LIT results. Calculation of the lethal concentration 50 (LC50) was performed using a probit analysis. All extracts reduced the viability of R. microplus larval stages (P<0.001), and viability was restored with the addition of PEG suggesting an important role of tannins in the acaricidal effect (P<0.001). The LC50 values of L. latisiliquum and P. piscipula plant extracts were 6.402 and 2.466 µg ml(-1). None of the tannin-rich plant extracts affected adult mortality (P>0.05). Lysiloma latisiliquum extract inhibited egg hatching of R. microplus (P<0.01). Tannin-rich plant extracts from A. pennatula, P. piscipula, L. leucocephala and L. latisiliquum showed potential acaricidal activity. Further in vivo studies are needed to confirm this finding.
Asunto(s)
Acaricidas/farmacología , Extractos Vegetales/química , Extractos Vegetales/farmacología , Rhipicephalus/efectos de los fármacos , Taninos/química , Taninos/farmacología , Acaricidas/administración & dosificación , Acaricidas/química , Animales , Relación Dosis-Respuesta a Droga , Liofilización , Larva/efectos de los fármacos , Extractos Vegetales/administración & dosificación , Plantas/química , Rhipicephalus/clasificación , Taninos/administración & dosificaciónRESUMEN
The effect of residual calf suckling on sub-clinical (SM) and clinical mastitis (CM) in dual-purpose cows was assessed. Prevalence, incidence rate, and relative risk were determined from 30 cows allocated to two treatments: (i) residual calf suckling once after milking (RCS) and, (ii) no residual calf suckling (NRCS). The overall prevalence of SM and CM, at cow and at quarter levels was higher in NRCS cows (P<0.05). The incidence rate of CM for NCRS and RCS cows was 53 cases per 10,000 animal-days at risk, and eight cases per 10,000 animal-days at risk, respectively. Cows that did not suckle their calves after milking were 6.59 (3.15-13.93) times more likely to develop CM than cows which did suckle after milking. In both experimental groups, coagulase-negative staphylococci were the most frequently isolated pathogens, followed by Staphylococcus aureus and Pseudomonas aeruginosa. Eliminating the practice of residual calf suckling presents a high risk for development of mastitis in dual-purpose cows.
Asunto(s)
Mastitis Bovina/epidemiología , Animales , Animales Lactantes , Bovinos , Femenino , Incidencia , Mastitis Bovina/etiología , Mastitis Bovina/microbiología , México/epidemiología , Prevalencia , Infecciones por Pseudomonas/epidemiología , Infecciones por Pseudomonas/microbiología , Infecciones por Pseudomonas/veterinaria , Factores de Riesgo , Infecciones Estafilocócicas/epidemiología , Infecciones Estafilocócicas/microbiología , Infecciones Estafilocócicas/veterinariaRESUMEN
As for some temperate forage, some tropical tanniniferous plants (TTP) from browsing might represent an alternative to chemical anthelmintic. The anthelmintic effect of four TTP (Acacia pennatula, Lysiloma latisiliquum, Piscidia piscipula, Leucaena leucocephala) on Haemonchus contortus was measured using two in vitro assays. First, the effects of increasing concentrations of lyophilized extracts (150, 300, 600, 1200 microg/ml PBS) were tested on H. contortus larvae (L(3)) using the larval migration inhibition (LMI) test. An inhibitor of tannin, polyvinyl polypyrrolidone (PVPP), was used to verify whether tannins were responsible for the AH effect. Secondly, the effects of extracts on larval exsheathment were examined. Larvae (L(3)) were in contact with extracts (1200 microg/ml) for 3h, and then were exposed to an artificial exsheathment procedure with observations of the process at 10 min intervals. A general lineal model (GLM) test was used to determine the dose effect in the LMI test and the difference of the percentage of exsheathed larvae between the control and the treatment groups. A Kruskal Wallis test was used to determine the effect of PVPP on LMI results. The LMI test showed a dose-dependent anthelmintic effect for A. pennatula, L. latisiliquum and L. leucocephala (P<0.01), which disappeared after PVPP addition, confirming the role of tannins. No effect was found for P. piscipula on H. contortus in the LMI test. However, all four plant extracts interfered with the process of L(3) exsheathment which might be involved as a mechanism of action of tannins on H. contortus larvae. A. pennatula, L. latisiliquum and L. leucocephala could be used as an anthelmintic for the control of H. contortus after confirmation based on in vivo studies.
Asunto(s)
Antihelmínticos/farmacología , Hemoncosis/veterinaria , Haemonchus/efectos de los fármacos , Fitoterapia/veterinaria , Extractos Vegetales/farmacología , Taninos/farmacología , Acacia/química , Animales , Relación Dosis-Respuesta a Droga , Fabaceae/química , Hemoncosis/tratamiento farmacológico , Larva , Modelos Lineales , Povidona/análogos & derivados , Povidona/farmacología , Taninos/antagonistas & inhibidores , Factores de TiempoRESUMEN
The anthelmintic (AH) effect of Acacia pennatula, Leucaena leucocephala, Lisyloma latisiliquum and Piscidia piscipula was evaluated in the infective larvae (L(3)) of Trichostrongylus colubriformis. Different concentrations of lyophilized extracts were tested using the larval migration inhibition (LMI) test. An inhibitor of tannins (the polyvinyl polypyrrolidone [PVPP]) was used to verify whether these compounds were responsible for the AH effects. Then, the effect of extracts on larval exsheathment was examined by observing the exsheathment process at 10-min intervals for 70 min. The LMI test showed a dose-dependant AH effect for A. pennatula, L. leucocephala and L. latisiliquum (P<0.01), but not for P. piscipula. The restoration of L(3) migration to values similar to those of controls after the addition of PVPP, indicates that tannins are involved in AH effects. Trichostrongylus colubriformis exsheathment was partially or totally blocked by the four plants extracts. Tropical tanniniferous plants evaluated in the current study may have potential as AH for the control of T. colubriformis if in vivo investigations indicate useful effects.
Asunto(s)
Antihelmínticos/farmacología , Extractos Vegetales/farmacología , Trichostrongylus/efectos de los fármacos , Trichostrongylus/fisiología , Animales , Antihelmínticos/química , Relación Dosis-Respuesta a Droga , Larva/efectos de los fármacos , Larva/fisiología , Extractos Vegetales/química , Hojas de la Planta/química , Factores de Tiempo , Clima TropicalRESUMEN
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.
Asunto(s)
Enfermedades de los Bovinos/parasitología , Ixodidae/microbiología , Metarhizium/fisiología , Infestaciones por Garrapatas/veterinaria , Animales , Bovinos , Enfermedades de los Bovinos/epidemiología , Enfermedades de los Bovinos/prevención & control , México/epidemiología , Control Biológico de Vectores/métodos , Infestaciones por Garrapatas/epidemiología , Infestaciones por Garrapatas/parasitología , Infestaciones por Garrapatas/prevención & control , Clima TropicalRESUMEN
Southern cattle tick, Boophilus microplus, control in the Mexican tropics is based on the application by spray, dip or pour-on of acaricides. In Mexico the first report of ticks resistant to amitraz was reported in 2002. Amitraz resistance affecting the cattle industry of Yucatan State, Mexico, has not been investigated. A cross-sectional study was carried out in order to investigate the possible association between management risk factors and the prevalence of B. microplus ticks resistant to amitraz in Yucatan, Mexico. Ninety-eight cattle farms were randomly selected and a sample of 20-30 engorged B. microplus females was collected from at least 10 cattle from each farm. Collected ticks were taken to the laboratory where the larval progeny were obtained. The modified larval immersion test was used to detect ticks resistant to amitraz. A discriminating dose of 0.0002% amitraz was used. A questionnaire was applied on each collaborating farm. For the statistical analysis a 2x2 contingency table was used to identify potential risk factors. The prevalence of farms with B. microplus resistant to amitraz was 19.40%. However, even though tick resistance to amitraz is a present problem there was no evidence that it was associated with the risk factors analyzed in this survey.
Asunto(s)
Enfermedades de los Bovinos/prevención & control , Resistencia a los Insecticidas , Insecticidas/uso terapéutico , Ixodidae/efectos de los fármacos , Infestaciones por Garrapatas/veterinaria , Toluidinas/uso terapéutico , Crianza de Animales Domésticos/métodos , Animales , Bovinos , Estudios Transversales , Femenino , México , Pruebas de Sensibilidad Parasitaria , Prevalencia , Factores de Riesgo , Infestaciones por Garrapatas/tratamiento farmacológico , Infestaciones por Garrapatas/prevención & control , Resultado del TratamientoRESUMEN
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.
Asunto(s)
Vectores Arácnidos/efectos de los fármacos , Resistencia a los Insecticidas , Insecticidas/farmacología , Ixodidae , Control de Ácaros y Garrapatas/métodos , Animales , Bovinos , Enfermedades de los Bovinos/tratamiento farmacológico , Enfermedades de los Bovinos/parasitología , Femenino , Ixodidae/efectos de los fármacos , México/epidemiología , Organofosfatos/farmacología , Prevalencia , Piretrinas/farmacología , Factores de Riesgo , Infestaciones por Garrapatas/tratamiento farmacológico , Infestaciones por Garrapatas/veterinariaRESUMEN
The efficacy of 0.5% moxidectin pour-on in cows with naturally acquired nematode infections was evaluated. The study was carried out in a ranch in Veracruz, Mexico. Four groups of 15 cows were randomly allocated. Animals in the treated group received 0.5% moxidectin pour-on at a dose of 0.5 mg/kg body weight on a single occasion. The other two groups remained as untreated controls. Fecal samples from all cattle were taken on days 0 (pre-treatment), 7, 14, 28 and 60 (post-treatment, PT). Fecal egg-counts were determined using a modified McMaster technique and fecal cultures were performed to identify gastrointestinal nematodes infected larvae (L(3)). Treatment with moxidectin was associated with a significant reduction in fecal trichostrongyle egg-counts compared with the controls; efficacy was 100% at 28 days PT. Haemonchus spp. and Strongyloides spp. were the two genera identified from coprocultures.