Roadmap for nematode control strategies

Environment is known to affect pasture infectivity, the distribution of nematode populations, and maintenance of refugia at pasture. To date, however, the pathways to use this knowledge effectively to enhance sustainable control are unclear.

What is the impact of climate and management especially in unusual years, e.g. prolonged grazing season, hot dry summers and cold winters, on worm transmission and burdens?
How large must environmental refugia be and how long should they persist in order to minimize selection for AR?
How can we improve the timing of treatment to not only enhance parasite control in the short term but also slow AR?
What are the main environmental factors affecting parasites in refugia under temperate and tropical conditions?
We lack knowledge on the movement and survival of GI nematode infective larvae under tropical conditions, particularly for heterogeneous vegetation (browse).
Can knowledge on environmental determinants of liver and rumen fluke be used to guide grazing to reduce disease risk?
Does AR carry a fitness cost to the parasite and how can this be exploited to develop strategies to lead to a reversion to susceptibility?
Are refugia-based strategies appropriate for all nematodes, e.g. fluke, and how do differing life cycles affect approaches?
Climate change is altering infection patterns, and empirical approaches to designing control strategies are of limited use when dealing with increasingly unpredictable transmission.

Build further on mathematical models of nematode epidemiology, including extension to predict refugia under varying environmental conditions and treatment strategies.
Integrate nematode management into grazing management at farm level, e.g. under precision grass management systems.

Better quantification of development and survival of nematode stages in the environment and intermediate hosts in different ecosystems and vegetation types.
User-friendly tools to deliver pasture-level risk assessments to the farmer in a form that permits appropriate action.

There is abundant experimental work to support predictive approaches to infection pressure for nematodes and trematodes, and sound model frameworks, but there are still important knowledge gaps. Models also need to be validated using stronger field data sets, applied to realistic farm management contexts, and translated more effectively into practical nematode control practices.
Empirical knowledge of the topographical and other environmental determinants of liver fluke risk within farms is sound but practical avoidance strategies are still not fully developed and certainly not widely applied, in favour of routine anthelmintic use.
Current knowledge of the genetic basis of AR limits attempts to generate accurate predictions of the impacts of environmental refugia on rate of development of resistance.