Altered patterns of helminth parasitic disease in Scottish livestock – a role for climate change?

The study of the potential impacts of climate change on animal health and welfare is in its infancy and urgently needs to gather momentum. This presentation aims to provide a general overview of the current state of affairs, drawing on available information from a Scottish perspective. There is a now a broad consensus amongst scientists that the global climate is changing. All available predictions would indicate that, over the next decade, the weather in the UK will feature greater extremes of climatic conditions, with a general trend towards drier, warmer summers and milder, wetter winters. These changes will obviously impact on the health and welfare of farmed animals, both directly and indirectly. For example, we may anticipate having to protect animals from heat stress and dehydration or provide adequate shelter in more adverse weather conditions. Similarly, there may be indirect effects on livestock through availability of feed supply or a change in forage available for grazing, for example. However, where a changing climate is likely to have most impact is in the transmission and epidemiology of livestock disease. There has been much publicity surrounding the incursion of “exotic” diseases such as Bluetongue and West Nile virus and the spread of vector-borne disease such as Lyme disease and tick-borne encephalitis. However, endemic diseases have been largely ignored. Endemic infectious organisms likely to be strongly influenced by changes in the weather are the parasitic helminths, the causative agents of such diseases as parasitic gastroenteritis (PGE) and liver fluke disease. The larval stages of these parasites develop and survive at pasture and, in some cases, in an intermediate host for a considerable amount of time before being ingested by a host. If climate change alters the ability of some of these larval stages to over-winter on pasture, or survive arrested within the host, the epidemiology of these parasites may be altered accordingly and unexpected, ‘unseasonal’, clinical disease may be witnessed.