Keynote Message

The cardiopulmonary nematode of dogs, Angiostrongylus vasorum, has apparently spread rapidly through Europe in the past couple of decades. This pattern has been partly driven by increased awareness of the parasite, new diagnostic tools, and investment in large prospective studies. Longitudinal studies in foxes on Great Britain, however, show that spread is real and not concocted, and anecdotal data elsewhere in Europe also suggest genuine spread. Climate seems to be a strong influence on observed global distribution, with exclusion from areas too cold in winter or too dry in summer. In Europe, it could be that the parasite is gradually expanding into its climatic envelope, and/or that the envelope is expanding as a result of global warming. This session will address climatic and other factors that might influence the spread of A. vasorum through Europe. Increasing urban fox populations in the wake of successful elimination of rabies, accelerating dog movements, and changes in communities of gastropod mollusc intermediate hosts are all hypothetically linked to range expansion and higher prevalence in endemic areas. Observed patchiness in distribution might be explained by mode of spread, or unequal sampling effort. Progress has been made in understanding the core climatic drivers of parasite transmission, but these are strongly modified by host factors; for example, recent data suggest that infection of snails drives changes in behaviour that subsequently alter parasite development rate. Integrating climatic and host drivers of transmission and spread provides a significant scientific challenge, which will take time to provide definitive answers. Forces leading to the emergence of A. vasorum could also vary locally, so a unified explanation might not be possible. Nevertheless, some general patterns are apparent and should guide practitioner strategies for managing the disease.

Key References

1.  Morgan ER, Jefferies R, Krajewski M, et al. Canine pulmonary angiostrongylosis: the influence of climate on parasite distribution. Parasitology International. 2009;58:406–410. DOI: 10.1016/j.parint.2009.08.003.

2.  Morgan E, Shaw S. Angiostrongylus vasorum infection in dogs: continuing spread and developments in diagnosis and treatment. Journal of Small Animal Practice. 2010;51:616–621. DOI: 10.1111/j.1748-5827.2010.01000.x

3.  Morgan ER.Canine pulmonary angiostrongylosis: can a worm change its spots? Veterinary Record. 2014;175:116–117.

4.  Taylor CS, Gato RG, Learmount J, et al. Increased prevalence and geographic spread of the cardiopulmonary nematode Angiostrongylus vasorum in fox populations in Great Britain. Parasitology. 2015;142:1190–1195. DOI: 10.1017/S0031182015000463.

5.  Aziz NAA, Daly E, Allen S, et al. Distribution of Angiostrongylus vasorum and its gastropod intermediate hosts along the rural- urban gradient in two cities in the United Kingdom, using real-time PCR. Parasites and Vectors. 2016;9:56. DOI: 10.1186/s13071-016-1338-3.