Why do some parasites kill the host they depend upon while others coexist with their host? Two prime factors determine parasitic virulence: the manner in which the parasite is transmitted, and the evolutionary history of the parasite and its host. Parasites which have colonized a new host species tend to be more virulent than parasites which have coevolved with their hosts. Parasites which are transmitted horizontally tend to be more virulent than those transmitted vertically. …showed first 75 words of 2936 total…

…showed last 75 words of 2936 total…and Host Behaviour. Barnard, C. J. and Behnke, J. M. Eds. Taylor & Francis. London. Read, A. F. and Harvey, P. H. 1993. The evolution of virulence. Nature. 362:500-501. Toft, C. A. and Aeschlimann, A. 1991. Introduction: Coexistence or Conflict? pp. 1-12 In Parasite-Host Associations: Coexistence or Conflict? Oxford University Press. Oxford. Wise, L. A. (1990) Small Animal Medical Nursing pp. 226-261 In Clinical Textbook for Veterinary Technicians, Second Edition. McCurnin, D. M. Ed. W. B. Saunders Company. Philadelphia.