Anthelmintic resistance in the field: Changes in resistance status of parasitic populations in response to anthelmintic treatment

Changes in anthelmintic resistance in nematode parasites were monitored in sheep grazing on 2 separate farms, but with the same anthelmintic treatment program, over 16 years. High levels of benzimidazole resistance emerged in Ostertagia and Trichostrongylus spp populations on both farms following 9 years of continuous use of this class of drug. Subsequently, variations in the levels of resistance occurred for the same species between farms and between species on the same farm. A change to levamisole for 2 years resulted in a significant reversion towards benzimidazole susceptibility, but a concomitant rise in levamisole resistance, in Ostertagia on one farm. However, benzimidazole resistance increased rapidly following the re-introduction of oxfendazole into the anthelmintic treatment program. Results from both farms illustrate the pitfalls of using one anthelmintic class for an extended period and provide indirect support for the alternation of anthelmintic classes at approximately yearly intervals.     

Detection of reserpine in horses by high-performance liquid chromatography

SUMMARY A high-performance liquid chromatography (HPLC) assay was developed for the detection of reserpine. The assay was used to monitor the plasma concentrations of the drug given intramuscularly on one or two occasions to five horses. The blood concentrations of reserpine varied quite considerably between horses given the same dose of the drug. However, on average, reserpine could be detected consistently, and quantified, for 48 h after a single dose of 2.5 mg, and for a similar period after the second of two 2.5 mg doses given 13 d apart. Because of the apparently large variability in the pharmacokinetics of reserpine in horses, exact times cannot be given beyond which the drug will no longer be detectable in the plasma. However, following two doses of 2.5 mg reserpine given 13 d apart, at least 7 d must elapse after the second dose before there is no drug detectable in the plasma of most horses.     

Beobachtungen zu einer Schlaffsuchterkrankung der Fichtengespinstblattwespe,Lyda hypotrophica Htg. (Cephaleia abietis L.) im Latenzstadium und während der Fraßperiode in den Kronen

Zusammenfassung Beobachtungen von Kalamit?ten der FichtengespinstblattwespeLyda hypotrophica Htg. (Cephaleia abietis L.) in den letℨten beiden Jahrzehnten in ?sterreich ergaben unter den biotischen Faktoren des Umweltwiderstandes auch das Aufscheinen einer Kernpolyedrose, die vor allem das Fettgewebe, teilweise aber auch das Mitteldarmgewebe ergriff. Die Bedeutung der Erkrankung lag vor allem in den nun erstmalig festgestellten epidemischen Ausbrüchen w?hrend der Fra?periode der Afterraupen in den Kronen. Es wurden dadurch Fra? sch?den weitgehend gemildert und das Abbaumen zahlreicherer vollentwickelter Larven zu den B?den verhindiert. Die reduzierende Wirkung der Erkrankung auf die Latenzlarven in den B?den war von geringerer Bedeutung; sie lag nach vorgenommenen Probegrabungen zwischen 0 und 27%.

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Summary Observations on an atony disease of the false spruce webworm,Lyda hypotrophica Htg. (Cephaleia abietis L.) in the stage of latency and during its feeding period in tree crowns. Observations on outbreaks of the false spruce webwormLyda hypertrophica Htg. (Cephaleia abietis L.) during the last two decades in Austria revealed, among biotic factors of environmental resistance, the occurrence of a nuclear polyhedrosis attacking mainly the fatty tissue but partly also the mesenteric tissue. The importance of the disease consisted chiefly in epidemie outbreaks during the larvae's (pseudo-caterpillars') feeding period in the tree-crowns. Damages by the larvae's feeding were greatly reduced by this way, and the descent of numerous larvae from trees to the ground prevented. The reducing effect of the disease on larvae in the stage of latency (diapausis) in soils was of less importance varying between 0% and 27% in sample diggings.

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Résumé Observations sur une atonie de Lyda Hypotrophica Htg. (Cephaleia abietis L.)en diapause et pendant la periode de pature dans les cimes d'arbres. Les observations sur des gradations deLyda hypertrophica Htg. (Cephaleia abietis L.) pendant les deux dernières décennies en Autriche ont révélé, parmi les facteurs biotique de la résistance ambiante, l'apparition d'une polyédrose nucléaire attaquant avant tout le tissu adipeux, mais encore en partie le tissu mésentérique. L'importance de la maladie consistait avant tout en irruptions épidémiques pendant le période de pature des larves (pseudochenilles) dans les cimes d'arbres. Les dégata par pature en furent considérablement modérés et la descente par terre de nombreuses larves vivant sur les arbres fut empêchée. L'éffet réduisant de la maladie sur les larves en diapause dans les sols était de moindre importance, avec une variation entre 0% et 27% dans les déterrements d'échantillonnage.

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Резюме Наблюдения на заб олевании от атони и слового пилильщика — ткач а (Lyda hypotrophica Htg. [Cephaleia abietis L.]) в диапаузе и в п ериод поедания в к ронах. Доцент Др. Эльза Ян Наблюдения на гра дациях слового пи лильщикаткача Lyda hypertrophica Htg. (Cephaleia abietis L.) в последние два де сятиетия в Австри и показали между биотически ми факторами отпо ра внешной среды и появление ядрового полиэдр оза, поражавлиего прежде всего жирн ую ткань, но частич но и средне кишечную т кань (mesenteron). Значение заболевания сост ояло прежде всего в эпидемических в спышках во время п ериода поедания личинок (ложных гу сениц) в кронах. Так им образом повреж дения от поедания были значительно умерены, а спуску м ногочисленных ли чинок от деревьев на землю было поставлено п репяствие. Уменьшительное д ействие заболева ния на личинок в ди апаузе в почвах бы ло более незначит ельно, колебаясь по испо лненным пробным в ыкопаниям между 0 и 27%.

     

Determining the Influence of Water Deficiency on NPK Stress Discrimination in Maize using Spectral and Spatial Information

A necessary pre-requisite for variable rate application of plant nutrients to manage inputs in a site-specific manner is a technique to detect nutrient stresses in plants in real-time. Spectral reflectance of plant canopy may provide a non-destructive and rapid technique to detect nutrient and water stress in plants. In this study, we investigated the effect of water on nutrient stress discrimination (nitrogen, N; phosphorus, P; and potassium, K) based on the visible and near infrared reflectance of maize leaves grown under controlled greenhouse conditions. The analysis of the spectral data indicated that it was challenging to detect the nutrient deficiencies if the plant water status was unknown. However, if a priori knowledge of water stress existed, such as a well-watered situation, the ability to discriminate nutrient stress improved significantly. The analysis of whole plant behaviour (i.e., mean reflectance data from all leaves within a plant) versus leaves located at a specific location within a plant indicated that knowledge of spatial location of leaves within a plant helped to identify N and P stress and NPK as a multi-stress condition more clearly.     

Inheritance and linkage analysis of resistance to zucchini yellow mosaic virus, watermelon mosaic virus, papaya ringspot virus and powdery mildew in melon

A melon (Cucumis melo L.) breeding line derived from PI 414723 is resistant to three potyviruses,watermelon mosaic virus (WMV), zucchini yellow mosaic virus (ZYMV), papaya ringspot virus (PRSV), and to powdery mildew (PM). The inheritance and linkage relationships of these four resistances were studied in a segregating F2 population and derived F3 families from a cross between cultivar Top Mark and the resistant breeding line. Dominant monogenic inheritance of all four resistances was observed. We report that line 414723-4S3, which was initially selected as a source of ZYMV and WMV resistance, is also a source of dominant monogenic resistances to PRSV and PM race 1. We also report on genetic linkage (significant departure from independent segregation, χ² = 58.1, p≪ 0.0001) between resistance to WMV and ZYMV. The map distance between these loci was estimated to be 7.5 cm. The genes for resistance to PM and PRSV segregated independently from each other, and from ZYMV and WMV resistance. This revised version was published online in July 2006 with corrections to the Cover Date.