A growing degree-day model for determination of Fasciola hepatica infection risk in New Zealand with future predictions using climate change models
Loading...
Files
Date
28/05/2016
Open Access Location
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier
Rights
Abstract
Infections of ruminants with Fasciola hepatica are considered to be of regional importance
within New Zealand but there is very little recent information on its prevalence or severity
other than anecdotal reports. Generally they are considered to be of secondary importance
compared to gastrointestinal nematode infections. Utilizing data from Virtual Climate Stations
(n = 11491) distributed on a 5 km grid around New Zealand a growing degree-day model was
used to describe the risk of infection with liver fluke from 1972-2012 and then to apply the
predictions to estimate the risk of fluke infections within New Zealand for the years 2040 and
2090. The growing degree-day model was validated against the most recent survey of infection
within New Zealand in 1984. A strong positive linear relationship for 1984 between F. hepatica
prevalence in lambs and infection risk (p<0.001; R2 =0.71) was found indicating the model was
effective for New Zealand. A linear regression for risk values from 14 regions in New Zealand for
1972-2012 did not show any discernible change in risk of infection over this time period
(p>0.05). Post-hoc comparisons indicate the risk in Westland was found to be substantially
higher (p<0.05) than all other regions with Northland ranked second highest. Notable
predicted changes in F. hepatica infection risk in 2040 and 2090 were detected although they
did vary between different climate change scenarios. The highest average percentage changes
in infection risk were found in regions with low initial risk values such as Canterbury and Otago;
in these regions 2090 infection risk is expected to rise by an average of 186% and 184%,
respectively. Despite the already high levels of infection risk in Westland, values are expected
to rise by a further 76% by 2090. The model does show some areas with little change with
Taranaki predicted to experience only very minor increases in infection risk with average 2040
and 2090 predicted changes of 0% and 29%, respectively. Overall, these results suggest the
significance of F. hepatica in New Zealand farming systems is probably underestimated and that
this risk will generally increase with global warming following climate change.
Description
Keywords
Fasciola hepatica, Climate change, Growing degree-day model, New Zealand
Citation
VETERINARY PARASITOLOGY, 2016, 228 pp. 52 - 59