Control of lice on cattle with dursban

Extract

A number of spray formulations of organophosphorus insecticides that kill both nymphal and adult stages of lice on cattle are available to the farmer. To achieve high levels of control, two applications of these materials 14 to 17 days apart are recommended. The second application controls nymphs emerging from eggs already present at the first application and unaffected by it.     

The detection of anthelmintic resistance in nematodes of veterinary importance

Before revised World Association for the Advancement of Veterinary Parasitology (WAAVP) guidelines on the detection of anthelmintic resistance can be produced, validation of modified and new methods is required in laboratories in different parts of the world. There is a great need for improved methods of detection of anthelmintic resistance particularly for the detection of macrocyclic lactone resistance and for the detection of resistant nematodes in cattle. Therefore, revised and new methods are provided here for the detection of anthelmintic resistance in nematodes of ruminants, horses and pigs as a basis for discussion and with the purpose that they are evaluated internationally to establish whether they could in the future be recommended by the WAAVP. The interpretation of the faecal egg count reduction test has been modified and suggestions given on its use with persistent anthelmintics and continuous release devices. An egg hatch test for benzimidazole (BZ) resistance is described. A microagar larval development test for the detection of benzimidazole and levamisole resistance provides third stage larvae for the identification of resistant worms. The sensitivity of these two tests can be increased by using discriminating doses rather than LD(50) values. Details are given of a PCR based test for the analysis of benzimidazole resistance in strongyles of sheep and goats, horses and cattle. Although promising for ruminant trichostrongyles, quantitative determination of gene frequency using real time PCR requires further development before PCR tests will be used in the field. Apart from faecal egg count reduction tests there are currently no satisfactory tests for macrocylic lactone resistance despite the great importance of this subject. Except for treatment and slaughter trials there are no validated tests for fasciolicide resistance or for the detection of resistance in cestodes.     

Toxicity and tissue residue depletion of levamisole hydrochloride in young goats

Toxicity and tissue residue depletion studies were conducted in young goats, using an oral drench formulation of levamisole hydrochloride. In the target animal toxicity study, 3 groups of 5 goats each were given levamisole orally to provide approximately 11.88, 23.76, or 35.64 mg of levamisole HCl/kg/d for 3 consecutive days; a fourth group of 5 goats served as untreated controls. Blood samples were taken for analysis of levamisole 1 day prior to dosing and 1, 2, 3, 4, and 7 days following the third dose. At the 35.64-mg/kg dose, 2 of 5 goats responded with typical cholinergic signs of toxicosis on each of the 3 days of dosing. The times for the onset of clinical signs of toxicosis ranged from 18 to 63 minutes, with an average duration of 32 minutes. Administration of 23.76 mg of levamisole HCl/kg resulted in hyperactive behavior in 1 of 5 goats only on the first day of dosing; no abnormal behavior was observed in any of the 5 goats following the second or third dose of levamisole HCl at 23.76 mg/kg. Untoward effects were not seen in the 5 goats dosed at 11.88 mg of levamisole HCl/kg or in the controls during the 3-day dosing period or in the following 7-day observation period. Overall, the observed signs of toxicosis did not become more severe, affect more goats, or persist for a longer period on subsequent dosing days.(ABSTRACT TRUNCATED AT 250 WORDS)     

Estimating potato crisp colour variability using image analysis and a quick visual method

Summary Image analysis gave better precision than colorimetry in measuring the darkening caused by excess free sugar during crisping of potatoes. The image analyser was used to measure individual crisp Average Optical Density (AOD) values in order to examine the variability of AOD within and between tubers. It is unnecessary to measure more than one crisp per tuber when assessing breeding lines, although two crisps per tuber are recommended for quality control. Crisps from at least ten tubers should be measured. A ‘Quick Crisp’ method, in which single crisps from each of four tubers are judged against standard samples, is reported. Regression of results from this method on crisp reflectance percentage (Agtron score) gaveR ² of 0.967. However, the observer tended to overestimate at low values and underestimate at high values. Over several trials, the crossover point varied from 15 to 50 Agtron score units. Measurement of crisp colour variability for improving selection, management and purchasing decisions is discussed.     

Calibration and diagnostic accuracy of simple flotation, McMaster and FLOTAC for parasite egg counts in sheep

The present study was aimed at carrying out a calibration and a comparison of diagnostic accuracy of three faecal egg counts (FEC) techniques, simple flotation, McMaster and FLOTAC, in order to find the best flotation solution (FS) for Dicrocoelium dendriticum, Moniezia expansa and gastrointestinal (GI) strongyle eggs, and to evaluate the influence of faecal preservation methods combined with FS on egg counts. Simple flotation failed to give satisfactory results with any samples. Overall, FLOTAC resulted in similar or higher eggs per gram of faeces (EPG) and lower coefficient of variation (CV) than McMaster. The "gold standard" for D. dendriticum was obtained with FLOTAC when using FS7 (EPG=219, CV=3.9%) and FS8 (EPG=226, CV=5.2%) on fresh faeces. The "gold standard" for M. expansa was obtained with FLOTAC, using FS3 (EPG=122, CV=4.1%) on fresh faeces. The "gold standard" for GI strongyles was obtained with FLOTAC when using FS5 (EPG=320, CV=4%) and FS2 (EPG=298, CV=5%). As regard to faecal preservation methods, formalin 5% and 10% or freezing showed performance similar to fresh faeces for eggs of D. dendriticum and M. expansa. However, these methods of preservation were not as successful with GI strongyle eggs. Vacuum packing with storage at +4°C permitted storage of GI strongyle eggs for up to 21 days prior to counting. Where accurate egg counts are required in ovine samples the optimum method of counting is the use of FLOTAC. In addition, we suggest the use of two solutions that are easy and cheap to purchase and prepare, saturated sodium chloride (FS2) for nematoda and cestoda eggs and saturated zinc sulphate (FS7) for trematoda eggs and nematoda larvae.     

Recent advances in laboratory models for evaluation of helminth chemotherapy

Extensive research on nematodes of veterinary importance has resulted in new tests based on incubation of parasitic nematodes in culture media, with a variety of detection systems including visual observation, inhibition of aggregation, reduced secretion of acetylcholinesterase and electronic motility measurements. There has been a proliferation of tests to detect benzimidazole resistant nematodes including egg embryonation, egg hatch, larval motility, differences in esterases, and tubulin binding by labelled benzimidazoles. A simple larval development test, which detects resistance to all types of anthelmintics, is likely to become the preferred test for evaluation of resistance in nematodes of grazing animals. By contrast the relative unimportance of trematodes and cestodes from a commercial point of view has resulted in few recent developments in models for evaluating chemotherapy. But the emergence of drug resistant strains of both schistosomes and liver fluke indicates the need for simple tests to detect resistance.