Apr 08

Online forecast map warns sheep farmers about risk of nematodirosis in lambs

Example Nematodirus forecast map

Example Nematodirus forecast map

With spring fast approaching the parasite Nematodirus is a deadly threat to the lives of lambing flocks.  An online risk forecast could help UK sheep farmers assess the risk of outbreaks of the parasite in their lambs and take action before it is too late.  The forecast maps will be updated daily to track changes in risk throughout the spring and early summer and include treatment and management advice.

The online risk forecast has been developed by SCOPS (Sustainable Control of Parasites in Sheep) and researchers at the University of Bristol’s School of Veterinary Sciences* to predict when Nematodirus eggs will hatch and when outbreaks are likely to happen.

­­­­­­­­­­­­­­­­­­­­­­­­­­­­­Nematodirus battus hatched - Jan van DijkNematodirosis, caused by the gutworm Nematodirus battus, is a deadly disease affecting young lambs. Eggs deposited on pasture by lambs the previous year hatch together in spring, triggered by a period of chilling over winter followed by warmer weather. Young lambs take in large numbers of larvae as they graze, which damage their gut leading to foetid black diarrhoea (black scour) and death.

Predicting when outbreaks might happen is becoming increasingly difficult due to variation in spring temperatures from year to year. Farmers can no longer rely on a standard timetable of treatments to avoid disease. As the damage is done by the larvae, faecal egg counts are of little use in detecting and controlling Nematodirus in young lambs.

The forecast takes advantage of the temperature-driven synchronised hatching of the Nematodirus larvae and uses weather data from 140 weather stations provided by the Met Office and Forecast.io. The interactive Google map allows farmers and advisers to select the nearest or most representative weather station and provides advice on how to relate the predicted risk to their particular farm and treatment options.

Cases of ­­­­­­­­­­­­­­­­­­­­­­­­­­­­­nematodirosis and eggs detected in routine faecal worm egg counts will also be mapped anonymously as they arise to improve the forecasts and SCOPS are asking farmers, advisors and diagnostic labs to contribute to these records by emailing researcher Dr Hannah Rose at the University of Bristol’s Vet School.

Dr Rose said: “In previous years 64 per cent of farmers and advisors surveyed changed the timing or extent of treatment – or advised treatment – after consulting the forecast, which has been running since 2013, and 93 per cent felt that their approach to control of this parasite had changed as a result of the forecast.”

UK Government funding provided by the Biotechnology and Biological Sciences Research Council has enabled further development of the forecast and it is hoped that even more farmers will benefit in 2016.

*The forecast is the culmination of the work of a number of BAVP members:
Dr Eric Morgan – University of Bristol
Dr Hannah Rose – Univeristy of Bristol
Dr Jan van Dijk – University of Liverpool (previously University of Bristol)
Owen Gethings – Harper Adams University (previously University of Bristol)

Relevant publications:

OWEN J. GETHINGS, HANNAH ROSE, SIÂN MITCHELL, JAN VAN DIJK and ERIC R. MORGAN (2015). Asynchrony in host and parasite phenology may decrease disease risk in livestock under climate warming: Nematodirus battus in lambs as a case study. Parasitology, 142, pp 1306-1317. doi:10.1017/S0031182015000633.

J. van DIJK and E. R. MORGAN (2008). The influence of temperature on the development, hatching and survival of Nematodirus battus larvae. Parasitology, 135, pp 269-283. doi:10.1017/S0031182007003812.

J. van DIJK and E. R. MORGAN (2010). Variation in the hatching behaviour of Nematodirus battus: Polymorphic bet hedging?. International journal for parasitology, 40(6), 675-681. doi:10.1016/j.ijpara.2009.11.002