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How will public and animal health interventions drive life-history evolution in parasitic nematodes?

  • PENELOPE A. LYNCH (a1) (a2), UWE GRIMM (a1) and ANDREW F. READ (a2) (a3)


Infection caused by parasitic nematodes of humans and livestock can have significant health and economic costs. Treatments aimed at alleviating these costs, such as chemotherapy and vaccination, alter parasite survival and reproduction, the main selective pressures shaping life-history traits such as age to maturity, size and fecundity. Most authors have argued that the life-history evolution prompted by animal and public health programmes would be clinically beneficial, generating smaller, less fecund worms, and several mathematical models support this view. However, using mathematical models of long-lasting interventions, such as vaccination, and regularly repeated short interventions, such as drenching, we show here that the expected outcome actually depends on how mortality rates vary as a function of worm size and developmental status. Interventions which change mortality functions can exert selection pressure to either shorten or extend the time to maturity, and thus increase or decrease worm fecundity and size. The evolutionary trajectory depends critically on the details of the mortality functions with and without the intervention. Earlier optimism that health interventions would always prompt the evolution of smaller, less fecund and hence clinically less damaging worms is premature.


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Anderson, R. M. and May, R. M. (1985). Helminth infections of humans: mathematical models, population dynamics and control. Advances in Parasitology 24, 1101.
Bell, R. G., Adams, L. S. and Gerb, J. (1981). Strongyloides ratti: dissociation of the rat's protective immunity into systemic and intestinal components. Experimental Parasitology 52, 386395.
Conover, D. O., Arnott, S. A., Walsh, M. R. and Munch, S. B. (2005). Darwinian fishery science: lessons from the Atlantic silverside (Menidia menidia). Canadian Journal of Fisheries and Aquatic Sciences 62, 730737.
Crook, M. and Viney, M. E. (2005). The effect of non-immune stresses on the development of Strongyloides ratti. Parasitology 131, 383392.
Gemmill, A. W., Skorping, A. and Read, A. F. (1999). Optimal timing of first reproduction in parasitic nematodes. Journal of Evolutionary Biology 12, 11481156.
Guinnee, M. A., Gemmill, A. W., Chan, B. H. K., Viney, M. E. and Read, A. F. (2003). Host immune status affects maturation time in two nematode species – but not as predicted by simple life-history model. Parasitology 127, 507512.
Leignel, V. and Cabaret, J. (2001). Massive use of chemotherapy influences life traits of parasitic nematodes in domestic ruminants. Functional Ecology 15, 569574.
Medley, G. F. (1994). Chemotherapy. In Parasitic and Infectious Diseases: Epidemiology and Ecology (eds. Scott, M. E. and Smith, G.), pp. 141157. Academic Press, San Diego.
Morand, S. (1996). Life-history traits in parasitic nematodes: a comparative approach for the search of invariants. Functional Ecology 10, 210218.
Morand, S. and Poulin, R. (2000). Optimal time to patency in parasitic nematodes: host mortality matters. Ecology Letters 186190.
Morand, S. and Sorci, G. (1998). Determinants of life-history evolution in nematodes. Parasitology Today 14, 193196.
Paterson, S. and Barber, R. (2007). Experimental evolution of parasite life-history traits in Strongyloides ratti (Nematoda). Proceedings of the Royal Society B-Biological Sciences 274, 14671474.
Poulin, R. (1998). Evolutionary Ecology of Parasites. From Individuals to Communities. Chapman and Hall, London.
Read, A. F. and Skorping, A. (1995). Causes and consequences of life history variation in parasitic nematodes. In Ecology and Transmission Strategies of Entomopathogenic Nematodes (eds. Griffin, C. T., Gwynn, R. L. and Masson, J. P.), pp. 5868. European Commisson, Brussels.
Roff, D. A. (1992). The Evolution of Life Histories. Theory and Analysis. Chapman and Hall, New York.
Skorping, A. and Read, A. F. (1998). Drugs and parasites: global experiments in life history evolution? Ecology Letters 1, 1012.
Skorping, A., Read, A. F. and Keymer, A. E. (1991). Life history covariation in intestinal nematodes of mammals. Oikos 60, 365372.
Sorci, G., Skarstein, F., Morand, S. and Hugot, J. P. (2003). Correlated evolution between host immunity and parasite life histories in primates and oxyurid parasites. Proceedings of the Royal Society Series B-Biological Sciences 270, 24812484.
Stear, M. J., Strain, S. and Bishop, S. C. (1999). How lambs control infection with Ostertagia circumcincta. Veterinary Immunology and Immunopathology 72, 213218.
Stearns, S. C. (1992). The Evolution of Life Histories. Oxford University Press, Oxford.
Viney, M. E., Steer, M. D. and Wilkes, C. P. (2006). The reversibility of constraints on size and fecundity in the parasitic nematode Strongyloides ratti. Parasitology 133, 477483.
Wilkes, C. P., Thompson, F. J., Gardner, M. P., Paterson, S. and Viney, M. E. (2004). The effect of the host immune response on the parasitic nematode Strongyloides ratti. Parasitology 128, 661669.


How will public and animal health interventions drive life-history evolution in parasitic nematodes?

  • PENELOPE A. LYNCH (a1) (a2), UWE GRIMM (a1) and ANDREW F. READ (a2) (a3)


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