Comparison of three in vitro techniques to estimate benzimidazole resistance in Haemonchus contortus of sheep

Three in vitro assays to detect benzimidazole resistance, namely, the egg-hatch assay, tubulin-binding assay, and a larval-development assay, were evaluated by estimating the level of benzimidazole resistance in three field isolates of Haemonchus contortus compared with a susceptible reference strain. Comparisons were also made with estimates of benzimidazole resistance of the three field strains obtained from an in vivo controlled anthelmintic efficacy test. All three in vitro tests showed similar, consistent results which also suggested greater sensitivity than the in vivo assay. These results indicate that selection of an in vitro technique to determine benzimidazole resistance should therefore be based on considerations other than precision, such as technical expertise, availability of equipment, cost and speed in which diagnosis is required.     

Matching spatial databases and quantitative models in land resource assessment

Abstract. Good land management needs information about land resources and the processes taking place in the landscape. In practical land evaluation this information is often expressed in terms of land qualities. The original survey data are stored in geographical information systems where they can be used to estimate the values of appropriate land qualities. Land qualities are complex attributes of land used in planning that may be derived from the original attributes through empirical threshold or regression models, or from process-based deterministic or stochastic simulation models. In order to improve estimates of the distribution of land qualities in space and time, and hence to improve planning decisions, the models require data with a much better spatial resolution than is usually available. The problems and dangers associated with the ad hoc linkage of simulation models and GIS are discussed. Particular attention needs to be paid to the problems of error propagation and costs and benefits when using models.     

Genomic variability among globally distributed isolates of equine arteritis virus.

Equine arteritis virus (EAV), a non-arthropod borne togavirus, has been shown to have a global distribution. To date, no major antigenic variation has been demonstrated between EAV isolates from different geographic origins. In this study, the genomic RNA of EAV isolates obtained from horses of different breeds in various countries around the world was oligonucleotide fingerprinted. Comparisons of these fingerprints were used to determine the extent of genomic variation among such isolates. Comparisons among isolates from North American horses revealed, for the most part, oligonucleotide homologies of less than 60%. Only 29 of the 98 comparisons revealed greater than 60% oligonucleotide homology. Nonetheless, several comparisons indicated a close epidemiologic relationship between isolates from horses of different breeds located in different states. Though all European isolates were of Standardbred origin and were from horses located in northern European countries, the majority had oligonucleotide homologies of less than 60%. Where oligonucleotide homology was apparent, it was, with one exception, greater than 70%. The two isolates from New Zealand had 93.2% oligonucleotide homology. This is indicative of an extremely close epidemiologic relationship. Comparisons between EAV isolates from around the world revealed oligonucleotide homologies between viruses from North America, Europe and New Zealand. In several instances, this homology was greater than 70% and in one case greater than 80%. No oligonucleotide homology was evident in comparisons involving the virus from South Africa. The high level of genomic conservation between certain EAV isolates of disparate geographic origins may reflect dissemination of the virus associated with the international movement of horses. The extent of genomic variation demonstrated between most of the EAV isolates used in this study confirms the need for further investigation of genomic heterogeneity among strains of this virus before techniques that rely upon nucleic acid hybridization can be effectively applied as diagnostic procedures.     

Toxic peripheral neuropathy with demyelination in Sprague-Dawley rats given CGS 21595--a 5-lipoxygenase inhibitor.

Male and female Sprague-Dawley rats were given CGS 21595, a pro-drug that is almost immediately metabolized to CGS 19213, a naphthoquinone that acts as a 5-lipoxygenase inhibitor. The compound was administered by gavage to five groups of Sprague-Dawley rats (group Nos. 1, 5, n = 30; group Nos. 2-4, n = 20) at daily doses of 0, 50, 150, 500, or 1,000 mg/kg for 13 weeks. Rats in the higher dose groups had a reduced weight gain, but significant neurologic signs were not observed. A peripheral neuropathy consisting predominantly of myelin destruction in the spinal nerve roots and sciatic nerves in male rats treated with greater than or equal to 150 mg/kg CGS 21595 and in female rats treated with greater than or equal to 50 mg/kg CGS 21595 for 13 weeks. This lesion was not fully reversible after a recovery period of 4 weeks. Lesions consisted of ballooning of myelin sheaths, infiltration by macrophages, demyelination, and occasional areas of remyelination. Axons were generally preserved, and the brain and spinal cord were not affected. Male and female rats in all treatment groups had cytoplasmic hyaline droplets in the proximal renal tubules. This change was reversible after 4 weeks and was not associated with any other adverse effects on the kidney.     

Leishmaniasis phytotherapy. Nature's leadership against an ancient disease.

The use of phytotherapy to treat human diseases has its roots in pre-historical times. Despite the modern advances achieved in the field of synthetic chemistry, the most efficient drugs available have their genesis directly or indirectly related with the vegetal kingdom. Indigenous communities have long used plant extracts to treat illnesses. Many of these extracts have shown effective action, with new bioactive compounds being extracted and screened every year. These extracts have also proven to be good sources of therapeutic agents to the treatment of Leishmaniasis. This work highlights some of these agents, while trying to emphasize the importance of plants as a source of new and powerful drugs against this widespread disease.     

Inland commercial fisheries management in France

The French fisheries management regime is based on public and private ownership of fishing waters associated with a complex multilevel management system. A total of 730 operational commercial inland fisheries were examined by analysis of thematic interviews and questionnaires. Commercial fishermen are beginning to understand the nature of their own activity and its relationship to the concept of sustainable management. Nevertheless, fishermen have to face two major problems: first, they are poorly represented on decision making bodies where anglers are dominant, and secondly their activities are governed by two separate ministries. Opportunities for future development may lie in decision making at the catchment level.     

Long-term variation in brown trout, Salmo trutta L., stocking success in a large lake: interplay between availability of suitable prey and size at release

Abstract –  Factors affecting long-term variation in brown trout, Salmo trutta L., stocking success were examined in a large lake, Lake Oulujärvi, in central Finland. Brown trout were stocked in spring (late May to early June) in 1974–1991 and in summer (late June to early July) in 1992–2001. The biomass of the vendace, Coregonus albula (L.), population (prey) at release time had the largest positive effect on stocking success within both periods: biomass of adult vendace in spring and both 0+ and adult vendace in summer. Increasing the size of stocked fish had a positive effect if the vendace available at release were only adults. The increasing trend of predator-catch-per-unit-effort (CPUE) [combined CPUE of northern pike Esox lucius L., burbot Lota lota (L.), and pike-perch Stizostedion lucioperca (L.)] through the study period and its negative effect on trout stocking success suggested an increasing effect of predation within the entire time series.     

Intramuscular and oral disposition of enrofloxacin in African grey parrots following single and multiple doses

The intramuscular (IM) and oral (PO) disposition of enrofloxacin, a new fluoroquinolone antimicrobial drug, were evaluated in African grey parrots. Peak enrofloxacin concentration, mean (+/- SEM), at 1 h following a 15-mg/kg IM dose was 3.87 (+/- 0.27) micrograms/ml and declined with a mean residence time of 3.05 h. Peak enrofloxacin plasma concentrations at 2 to 4 h following oral doses of 3, 15, and 30 mg/kg were 0.31 (+/- 0.11), 1.12 (+/- 0.11), and 1.69 (+/- 0.23) micrograms/ml, respectively, and declined with a mean residence time of 3.44-5.28 h. The relative bioavailability of the 15-mg/kg oral dose was 48%. An equipotent metabolite, ciprofloxacin, was detected in plasma at concentrations ranging from 3 to 78% of those of enrofloxacin. Enrofloxacin concentrations and area under the curve were significantly lower, the mean residence time significantly shorter and the ciprofloxacin/enrofloxacin ratios higher, following 10 days of oral treatment at 30 mg/kg every 12 h. Following 10 days of treatment, no significant biochemical changes were noted; however, polydipsia and polyuria occurred in treated birds, but resolved quickly upon discontinuation of enrofloxacin administration. These studies indicate that a rational starting dose for enrofloxacin in psittacines (7.5-30 mg/kg BID) should be higher than those in other domestic animals.     

Effect of heterogeneous digesta chemical composition on the accuracy of measurements of fiber flow in dairy cows.

The objective of the current study was to evaluate the effect of unrepresentative sampling of digesta particulate matter entering the omasal canal on the accuracy of fiber flow measurements. The experimental design comprised one period, one diet, and three cows as experimental units. Within each cow, the physical and chemical composition of digesta particulate matter was assessed at seven sites within the digestive tract. Three Finnish Ayshire dairy cows, equipped with ruminal and simple-T duodenal cannulas, in extended lactation were offered grass silage twice daily on an ad libitum basis. Digesta samples were collected from the rumen (dorsal and ventral sac), reticulum, omasal canal, omasum, duodenum, and rectum to determine particle size distribution in digesta, chemical composition of various particle size fractions, and distribution of two flow markers (Cr-labeled straw and indigestible NDF [INDF]) among particle size fractions. Digesta samples were wet-sieved using sieves of 2.50, 1.25, 0.630, 0.315, 0.160, and 0.080 mm. Particulate matter was analyzed for OM, NDF, and Cr concentrations, and INDF concentration was determined based on 12-d ruminal incubation. The particle size of digesta entering the omasal canal was larger compared with the omasum or the duodenum, suggesting that omasal canal samples were not representative of particle size distribution truly escaping the rumen. The concentration of potentially digestible NDF (PDNDF) decreased with decreasing particle size. The PDNDF concentration of particulate matter retained on all sieves was greatest in the rumen and gradually decreased along the digestive tract. From the reticulorumen to the omasum, the decrease was associated with decreased particle size, reflecting selective passage of particulate matter. In contrast, from the omasum to the duodenum and rectum, the PDNDF concentration decreased within each particle size fraction without effect on particle size, indicating a nonselective passage of particulate matter between these sites. Variation between particle size fractions was slightly greater for Cr concentration than for INDF concentration, indicating that unrepresentative sampling of particulate matter had a greater effect on Cr concentration compared with that of INDF. Owing to unrepresentative sampling, NDF entering the omasal canal was overestimated by 5% using INDF and underestimated by 7% using Cr as a particle phase marker. Of total NDF digestibility, proportionally 0.90, 0.07, and 0.03 occurred in the reticulorumen, omasum, and intestines, respectively. The current results indicate that, despite unrepresentative sampling of digesta particulate matter entering the omasal canal, the errors in determined NDF flow were small. The omasum may have a greater role in postruminal NDF digestion than the intestines.     

A field study on reproductive efficiency of mares maintained predominately on native pasture

A field study utilizing 145 mares of various age and breeding status was conducted to determine reproductive performance under native range conditions with only limited supplemental feeding. All mares had an average initial body condition score of 4.5 and a final score of 5.1 by the time breeding was completed and mares returned to pasture. Average foaling rate was 80%, and mares that had not conceived during the previous breeding season had a foaling rate of 94%, which was higher (P<.05) than 74% for lactating mares. Mares 16 years and older had a significantly lower foaling rate (P<.05) than younger mares. Old mares that were lactating at time of breeding had only a 37% foaling rate, which was less (P<.05) than for young lactating mares. The 94 mares bred by natural cover or artificial insemination that actually foaled required 1.43 cycles per conception. Lactating mares in the oldest age group required more cycles per conception (P<.05) than open mares, and these older, lactating mares also required more cycles per conception than younger mares with foals at side. Those mares diagnosed as pregnant or open at 45 days post breeding had a pregnancy rate of 97%. Average pregnancy loss for all mares was 7.7%. These data indicate that lactating mares in moderate body condition tended to skip a breeding season and that a body condition score of 5 was only marginally acceptable, especially in the case of lactating mares. Authors' address: Equine Science Program, Department of Animal Science, Texas Agricultural Extension Service, Texas A&M University, College Station, TX 77843. Technical Article Number 30023, Texas Agr. Exp. Sta.