Climate change and livestock parasites: integrated management of sheep blowfly strike in a warmer environment

Abstract

The incidence of parasite-mediated livestock disease is the result of a complex interaction of factors such as parasite and host abundance, host susceptibility, climate and, critically, farmer husbandry and intervention strategies, all of which change seasonally in space and time. Given the complexity of the interacting factors, the effects of environment changes on disease incidence are hard to predict, as accordingly are the optimal husbandry responses required to ameliorate any effects. Here a model system is used to explore these issues. Cutaneous myiasis (blowfly strike) is common disease of livestock and would be expected to be highly sensitive to even small changes in climate; it provides a good model for highlighting the problems inherent in attempting to predict the effect of climate change on livestock disease incidence. For this, a stochastic simulation model is used to examine the changes in the seasonal incidence of ovine cutaneous myiasis on farms in the United Kingdom and the likely effects of changes in husbandry and control strategies. The simulations show that the range of elevated temperatures predicted by current climate change scenarios result in an elongated blowfly season with earlier spring emergence and a higher cumulative incidence of strike. Overall, higher temperatures increased strike incidence disproportionately in ewes in early summer, but had relatively less direct effect on the pattern of lamb strike incidence; a 1 3 1C increase in average temperature approximately doubles the cumulative incidence of strike in lambs but results in four times more strikes in ewes. A range of strike management options is examined and the models show that changes in husbandry practices are also likely to have an important effect in reducing early season ewe strike incidences. The simulations suggest that integrated changes in husbandry practices are likely to be able to manage expected increases in strike, given the range of climate changes currently predicted.

Climate‐driven changes to the spatio‐temporal distribution of the parasitic nematode, Haemonchus contortus, in sheep in Europe

“…This was more pronounced under RCP8.5 than RCP2.6. The emergence of a bimodal pattern of seasonal infection pressure appears to be a consistent prediction for GINs in temperate and Arctic regions under various scenarios of climate change; a similar pattern was predicted for the GINs H. contortus , Teladorsagia circumcincta and Ostertagia ostertagi infecting ruminants in England (Rose et al ., ), and O. gruehneri infecting caribou in North America (Molnár et al ., ), as well as other parasitic helminths in northern Europe ( Fasciola hepatica ; Caminade et al ., ) and invertebrate ectoparasites in Great Britain ( Lucilia sericata ; Rose & Wall, ; Wall & Ellse, ). This ‘summer dip’ in infection pressure may play a role in moderating the impact of climate change in northern Europe (Rose et al ., ).…”

“…Some recent progress has been made in estimating the impact of climate change on management factors relevant to the epidemiology of gastrointestinal helminths like H. contortus , such as grazing season length (Phelan et al ., ). However, this remains a knowledge gap that can largely only be addressed by evaluation of comparative management scenarios (Morgan & Wall, ; Wall & Ellse, ).…”

Geographic distribution of livestock products in China- an application of spatial autocorrelation analysis

“…This limitation could be reduced by investments in transportation, communication and irrigation infrastructures (Schmidhuber and Tubiello, 2007). It is also worth to mention that global change will affect many of the environmental factors underpinning livestock industry in the future (Wall and Ellse, 2011). Thus, we are aware of the complex interactions among the underlying factors of livestock products distribution, which can not always be represented by a single model (Nahuelhual et al, 2012), such as logistic regression model (Wint et al, 2002;Gilbert et al, 2005).…”

Climate Change/Global Warming and Its Impacts on Parasitology/ Entomology

“…Warmer temperatures can also lead to shifts in temperature optima [42][43][44], and the exact evolutionary trajectory of host-parasite systems in a warmer world may depend sensitively upon underlying genetic correlation structures and interactions between host genotypes, parasite genotypes, and the environment [38,41,45,46] Consequently, the "longr-term response of the physiology of host-parasite systems to global warming becomes difficult to predict." Predators can inhibit epidemics by selectively culling sick hosts and/or by maintaining host densities below levels required for parasites to persist [46][47][48][49][50][51] Hall et al [52] argued that global warming does not necessarily mean that disease prevalence will increase in all systems. Morgan and Wall [53] have reemphasized many of the salient points earlier raised by Hall et al [52] and further elucidated the complex nature of global warming.…”