1A multi-species model to assess the impact of refugia on worm control and anthelmintic resistance in sheep grazing systems. RJ ObjectiveDevelop a computer simulation model that uses daily meteorological data and farm management practices to predict populations of Trichostrongylus colubriformis, Haemonchus contortus and Teladorsagia (Ostertagia) circumcincta and the evolution of anthelmintic resistance within a sheep flock. Use the model to explore if increased refugia, provided by leaving some adult sheep untreated, would delay development of anthelmintic resistance without compromising nematode control. ProceduresCompare model predictions with field observations from a breeding flock in Armidale, NSW. Simulate the impact of leaving 1-10% of adult sheep untreated in diverse sheep grazing systems. ResultsPredicted populations of T. colubriformis and T. circumcincta were less than those observed in the field. Attributed to nutritional stress experienced by sheep during drought, and not accounted for by the model. Observed variation in faecal egg count explained by the model (R 2 ) for these species was 40-50%. H. contortus populations and R 2 were both low.Leaving some sheep untreated worked best in situations where animals were already grazing or were moved on to pastures with low populations of infective larvae. In these cases anthelmintic resistance was delayed and nematode control was maintained when 1-4% of adult stock remained untreated. ConclusionsIn general, the model predicted that leaving more than 4% of adults untreated did not sufficiently delay the development of anthelmintic resistance to justify the increased 2 production risk from such a strategy. The choice of a drug rotation strategy had an equal or larger impact on nematode control, and selection for resistance, than leaving 1-10% of adults untreated. The multi-species model described here allows for these phenomena and estimates host mortalities and inappetence based on the total worm populations. To determine the utility of the model, worm populations were monitored in flocks of breeding ewes and weaners that were managed under typical grazing systems in north-eastern Australia. Daily meteorological and management records were kept so that worm populations could be predicted using the multispecies model. Keywords 3In this simulation study, the model was used to: a) estimate the consequences of leaving a proportion of adult stock untreated (as a source of refugia) on the development of anthelmintic resistance and effectiveness of parasite control; b) determine how best to use a new anthelmintic class (amino-acetonitrile derivatives (AAD), represented by monepantel; Zolvix ® , Novartis Animal Health Inc., Switzerland) to control gastro-intestinal nematodes while minimising selection for drug resistance; and c) examine these issues in four environments to determine if there are common principles that can be applied and/or how they need to be modified to suit local environments. The aim was to fully explore the interaction between the fundamen...
It is normal for hosts to be co-infected by parasites. Interactions among co-infecting species can have profound consequences, including changing parasite transmission dynamics, altering disease severity and confounding attempts at parasite control. Despite the importance of co-infection, there is currently no way to predict how different parasite species may interact with one another, nor the consequences of those interactions. Here, we demonstrate a method that enables such prediction by identifying two nematode parasite groups based on taxonomy and characteristics of the parasitological niche. From an understanding of the interactions between the two defined groups in one host system (wild rabbits), we predict how two different nematode species, from the same defined groups, will interact in co-infections in a different host system (sheep), and then we test this experimentally. We show that, as predicted, in co-infections, the blood-feeding nematode Haemonchus contortus suppresses aspects of the sheep immune response, thereby facilitating the establishment and/or survival of the nematode Trichostrongylus colubriformis; and that the T. colubriformis-induced immune response negatively affects H. contortus. This work is, to our knowledge, the first to use empirical data from one host system to successfully predict the specific outcome of a different co-infection in a second host species. The study therefore takes the first step in defining a practical framework for predicting interspecific parasite interactions in other animal systems.
Multiple reaction monitoring (MRM) mass spectrometry may be regarded as the gold standard methodology for quantitative mass spectrometry and has been adopted for the analysis of small molecules especially within the pharmaceutical industry. It can also be applied to the analysis of peptides and proteins and to the measurement of the basic building blocks of proteins, amino acids. Here, we describe the application of MRM mass spectrometry to the measurement of hydroxyproline after acid hydrolysis of various animal tissues. We show that the measurement of hydroxyproline provides an accurate and reliable estimate of the collagen content of such tissues and may be a useful indicator of meat tenderness.
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