Population biology of helminth infections of veterinary importance and its relevance to control
This chapter examines how mathematical models can be helpful in the design and evaluation of control programs directed against the debilitating and sometimes fatal diseases that arise when domestic ruminants are infected with helminth parasites. The models comprise hypotheses about the natural processes which control and regulate parasite abundance. The empirical description of regulatory processes is described in detail since these processes act in such a way as to confine parasite population density between certain bounds and so tend to work in opposition to disease control strategies.
It is demonstrated that models can rank strategies in order of efficacy — at least in parasitological terms — but currently give no good indication of how much better one strategy might be than another in terms of the things that most interest the farmer: the net return on his investment in parasite control, and the risk associated with that investment. It is argued that the proper use of the models described here is not to replace anthelmintic field trials but rather as tools to guide our thinking, a means of refining judgments about the strategies most likely to work, and a framework for the development of new methods of disease control. Models should reduce the number of field trials required to evaluate the possible permutations of some new strategy because we will already have some very good idea of which will work best.
KeywordsPopulation Biology Helminth Infection Parasite Burden Helminth Parasite Parasite Abundance
Unable to display preview. Download preview PDF.
- Anderson, N., J. Abrmour, R. M. Eadie, W. F. H. Jarrett, F. N. Jennings, J. S. D. Ritchie, and G. M. Urquhart. 1966. Experimental Ostertagia ostertagi infections in calves: results of single infection with five graded dose levels of larvae. American Journal of Veterinary Research 27:1259–1265.Google Scholar
- Armour, J. and C. P. Ogbourne. 1982. Bovine Ostertagiasis: a review and annotated bibliography. Miscellaneous publication No. 4., Commonwealth Institute of Parasitology.Google Scholar
- Barger, LA. (1982) Helminth parasites and animal production. In, Biology and Control of Endoparasites. (ed. by L. E. A. Symons, A. D. Donald, J. K. Dineen) Academic Press, Sydney, pp 133–156.Google Scholar
- Cole, H. H. and M. Ronning. 1974. Animal Agriculture. W. H. Freeman and Co., San Francisco.Google Scholar
- Gaafar, S. M. (ed.). 1983. Morantel Sustained Release Bolus. Special Issue of Veterinary Parasitology 12: 215–362.Google Scholar
- Gettinby, G. and W. P. Gardiner. 1980. Disease incidence forecasts by means of climatic data. Biometeorology 7: 87–103.Google Scholar
- Grenfell, B. T. and G. Smith. 1983. Population biology and control of ostertagiasis in first year grazing calves. Proceedings of the Society for Veterinary Epidemiology and Preventive Medicine (Southampton 12–13 April, 1983) pp 70–77.Google Scholar
- Hawkins, CD. and R. S. Morris. 1978. Depression of productivity in sheep infected with Fasciola hepatica. Veterinary Parasitology 4: 341–351.Google Scholar
- Hope-Cawdery, M. J., G. Gettinby, and J. N. R. Grainger. 1978. Mathematical models for predicting the prevalence of liver fluke disease and its control from biological and meteorological data. In. Weather and Parasitic Animal Disease. W.H.O. Technical Note No. 159. (ed. T. E. Gibson), 21–39.Google Scholar
- Michel, J. F. 1963. the phenomenon of host resistance and the course of infection of Ostertagia ostertagi in calves. Parasitology 53:63–84.Google Scholar
- Ollerenshaw, C. B. 1974. Forecasting liver fluke disease. In. The effects of Meteorological Factors upon Parasites. Symposium of the British Society for Parasitology Vol. 12. (ed. A. R. Taylor, and R. Muller) Blackwell Scientific Publications.Google Scholar
- Over, H. J. and J. Dijkstra. 1975. Infection rhythm in fascioliasis, In Facts and Reflections II (Lelystad Workshop on Fascioliasis) (ed. H. J. Over and J. Armour).Google Scholar
- Ross, J. G. 1967. An epidemiological study of fascioliasis in sheep. Veterinary Record 80: 214–217.Google Scholar
- Wilson, R. A., G. Smith, and M. R. Thomas. 1982. Fascioliasis. In, Population Dynamics of Infectious Diseases: Theory and Applications (ed. by R. M. Anderson). Chapman and Hall, London, pp. 262–304.Google Scholar