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251.
Sugarcane yellow leaf virus, the causal agent of yellow leaf, is transmitted from plant to plant by aphids. Understanding and evaluating the epidemic risks due to spread of yellow leaf by aphids is an important feature for sugarcane production. Four distinct sugarcane trials were set up with disease-free plants to study the relationship between spread of yellow leaf, the vector dynamics and environmental conditions that may favour yellow leaf epidemics. The study was performed by surveys of vector populations and determination of plant infections. Sugarcane cultivar SP71-6163, highly susceptible to yellow leaf, was analyzed spatially at different dates in all four trials and compared to commercial cultivars in two of the four trials. These surveys allowed us to identify a correlation between the aphid dynamics in the field and yellow leaf progress. Additionally, a negative correlation was found between rainfall during the first weeks after transferring sugarcane plants to the field and aphid dispersal within the field. This later result revealed an impact of rainfall on aphid invasion and subsequent plant infection by SCYLV. If aphids are the key factor for disease spread, plant response varied also according to cultivar resistance with high variation depending on rain conditions.  相似文献   
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253.
This phase II, randomized, open-label field trial was designed to evaluate and compare the safety and efficacy of four treatment durations (10, 20, 28 or 40 days) with marbofloxacin administered orally at the dosage of 2mg/kg once a day for canine visceral leishmaniosis. Twenty-four dogs naturally infected with visceral leishmaniosis and without biochemical disorder evidences of renal insufficiency, were recruited by two Greek veterinarian clinics. They were also randomly assigned to one of the four treatment duration groups, and have been clinically, haematologically, biochemically and parasitologically followed-up regularly for 9 months. Efficacy was achieved for 5/6 dogs treated for 28 days, 4/6 dogs treated for 10 or 20 days and for 3/6 dogs treated for 40 days. Moreover, efficacy was reached more quickly (58.4 days) in dogs treated for 28 days. Improvement of clinical signs tended to be better and faster in the 28 days treatment group too. After 9 months of follow-up, a total of three cases could be considered as relapsing (two dogs treated for 40 days and one dog treated for 28 days). There was a significant reduction in amastigotes density in macrophages after 3 months in the four groups when compared with the parasite density at inclusion. No adverse effects were noticed during this 9 months study. Results obtained with marbofloxacin at the dosage of 2mg/kg once a day for 28 days seem encouraging and may offer a safe alternative for treating canine visceral leishmaniosis.  相似文献   
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