Factors of Parasitic Virulence
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. It has been assumed that parasite-host interactions inevitably evolve toward lower virulence. This is contradicted by studies in which virulence is conserved or increases over time. A model which encompasses the variability of parasite-host interactions by synthesizing spatial (transmission) and temporal (evolutionary) factors is examined. Lenski and May (1994) and Antia et al. (1993) predict the modulation of virulence in parasite-host systems by integrating evolutionary and transmissibility factors. Why do certain parasites exhibit high levels of virulence within their host populations while others exhibit low virulence? The two prime factors most frequently cited (Esch and Fernandez 1993, Toft et
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Some common words found in the essay are:
Esch Fernandez, Sin Nombre, MODULATION Herre's, , Cheney Hibler, Keymer Read, HIV Gibbons, Rabies Lyssavirus, Read Harvey, VIRULENCE Incongruent, host density, et al, parasitic virulence, esch fernandez, esch fernandez 1993, fernandez 1993, lenski 1994, host population, host mortality, et al 1993, level virulence, antia et, antia et al, toft et al, et al 1995,
Approximate Word count = 3081
Approximate Pages = 12 (250 words per page double spaced)
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