RESUMO
The population dynamics of Rhipicephalus microplus (Ixodida: Ixodidae) in northwest Argentina was analysed to support the design of strategic methods for its control. Both parasitic and non-parasitic phases were studied. The seasonal activity of R. microplus in its parasitic phase was characterized by three peaks in abundance: the first in mid-late spring; the second in summer, and the third in autumn. The non-parasitic phase of R. microplus was characterized by a long total non-parasitic period observed after exposures of females from mid-summer to early autumn, a short total non-parasitic period observed after exposures of females from late winter to late spring, a short period of larval longevity in early and mid-summer, and no hatch of the eggs produced by females exposed in mid- and late autumn and winter. Treatments of cattle administered during the period from late winter to late spring will act on small cohorts of R. microplus, preventing the emergence of larger generations in summer and autumn. A 17-week spelling period starting in late spring and early summer will be necessary to achieve optimal control of R. microplus free-living larvae. If spelling begins in mid- or late summer or in autumn, the required period will be 26-27 weeks.
Assuntos
Doenças dos Bovinos/prevenção & controle , Rhipicephalus/fisiologia , Controle de Ácaros e Carrapatos/métodos , Infestações por Carrapato/veterinária , Animais , Argentina , Bovinos , Doenças dos Bovinos/parasitologia , Larva/crescimento & desenvolvimento , Larva/fisiologia , Dinâmica Populacional , Rhipicephalus/crescimento & desenvolvimento , Estações do Ano , Infestações por Carrapato/parasitologia , Infestações por Carrapato/prevenção & controleRESUMO
The main goal of the current work was to develop and validate an in vitro fluke egg hatch test, as a method for the detection of albendazole (ABZ) resistance in the liver fluke, Fasciola hepatica. Fluke eggs (200/ml, n= 5) from six different isolates were used in the current experimental work. They were obtained from different geographical locations and named Cullompton (UK), CEDIVE (Chascomus, Argentina), INTA-Bariloche (Bariloche, Argentina), Rubino (Uruguay), Cajamarca (Perú) and Río Chico (Catamarca, Argentina). The fluke eggs were incubated (25 °C) for a 12-h period in the presence of either ABZ or its sulphoxide metabolite (ABZ.SO) (5, 0.5 or 0.05 nmol/ml). Untreated eggs were incubated as a control. Incubated eggs (with or without drug present) were kept in darkness at 25 °C for 15 days. Afterwards, the trematode eggs were exposed to daylight over a 2-h period. Hatched and unhatched eggs were evaluated using an optical microscope, and the ovicidal activity was assessed for each fluke isolate. A very low ovicidal activity ( ≤ 13.4%) was observed in the ABZ-resistant CEDIVE isolate for both ABZ and ABZ.SO. Conversely, in the INTA-Bariloche and Río Chico isolates, which are suspected to be susceptible to ABZ, ovicidal activities ≥ 70.3% were observed after incubation with ABZ at the lowest concentration tested (0.05 nmol/ml). This finding correlates with that previously described for the ABZ-susceptible Cullompton. Finally, the Cajamarca and Rubino isolates behaved as ABZ resistant, since no ovicidal activity was observed after eggs were incubated with ABZ at 0.5 nmol/ml. Considering the specific results obtained for each isolate under assessment, the egg hatch test described here may be a suitable method for detection of ABZ resistance in F. hepatica.
Assuntos
Albendazol/farmacologia , Anti-Helmínticos/farmacologia , Resistência a Medicamentos , Fasciola hepatica/efeitos dos fármacos , Zigoto/efeitos dos fármacos , Animais , Fasciola hepatica/fisiologia , Testes de Sensibilidade Parasitária/métodos , Coelhos , América do Sul , Temperatura , Fatores de Tempo , Reino Unido , Zigoto/fisiologiaRESUMO
Cyst echinococcosis (CE) is a zoonotic disease caused by the larval stage of the Echinococcus granulosus helminth parasite. The work reported here aimed to compare the efficacy of albendazole (ABZ) and flubendazole (FLBZ) against CE in naturally infected sheep. Additionally, their comparative pharmacokinetic behaviour and the assessment of serum liver enzymes activities were studied. Twelve (12) naturally infected sheep were allocated to the following experimental groups: unmedicated control group, FLBZ-treated and ABZ-treated. Treatments were orally performed every 48 h, over 55 days at dose rate of 10 (FLBZ) and 8.5 (ABZ) mg/kg (equimolar dose rates). The efficacy of the drug treatments was based on protoscoleces' vitality/viability. The kinetic disposition assessment included the Initial and Final Kinetic Studies which implicated the collection of blood samples after both the first and the last drug administration. Blood samples were processed to measure drug concentrations by HPLC. The protoscoleces' vitality observed in the untreated control group (98%) was significantly reduced in the presence of both ABZ and FLBZ. 90% of mice inoculated with protoscoleces in the control group developed hydatid cysts in their peritoneal cavity (viability study). However, only 25% (FLBZ) and 33% (ABZ) of mice inoculated with protoscoleces recovered from treated sheep, developed hydatid cysts in their abdominal cavity. Reduced FLBZ (R-FLBZ) was the main metabolite recovered in the bloodstream after oral administration of FLBZ to sheep. Low plasma concentrations of FLBZ parent drug were measured up to 48 h post-administration. ABZ was not detected in plasma at any time post-treatment, being its metabolites ABZ sulphoxide (ABZSO) and ABZ sulphone (ABZSO2) recovered in plasma. Hepatotoxicity due to the continued treatment with either ABZ or FLBZ was not observed. A 3-fold increase ethoxyresorufin O-deethylase activity, a cytochrome P450 1A (CYP1A)-dependent enzyme reaction, was observed in liver microsomes obtained from sheep receiving ABZ, compared to those of the unmedicated and FLBZ-treated animals. In conclusion, FLBZ is an available anthelmintic which may be developed into an effective and safe drug for the human CE treatment. Despite the low plasma concentrations measured by FLBZ/R-FLBZ, an important reduction in protoscoleces' vitality was observed in cysts located in sheep liver. Modern pharmaceutical technology may help to greatly improve FLBZ systemic exposure improving its efficacy against CE.