Factors of Parasitic Virulence ABSTRACT wherefore do about parasites kill the array they opine upon while others coexist with their host? Two prime factors determine parasitic sourness: the climate in which the parasite is transmitted, and the developmentary narrative of the parasite and its host. Parasites which have settled a new host species flow to be more(prenominal) irate than parasites which have coevolved with their hosts. Parasites which be transmitted horizontally melt down to be more acetous than those transmitted vertically. It has been assumed that parasite-host interactions inescapably evolve toward lower tartness. This is contradicted by studies in which severity is conserve or increases over time. A model which encompasses the disagreement 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 malignity in parasi te-host systems by integrating evolutionary and transmissibility factors. INTRODUCTION Why do certain(prenominal) parasites bear witness 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 al. 1991) are evolutionary history and mode of transmission. In harmoniously evolved parasite-host associations are characterized by high virulence, while congruent evolution may result in reduced virulence (Toft et al. 1991).
Parasites transmitted vertically (from parent to offspring) tend to be little virule nt than parasites transmitted horizontally (! between unrelated individuals of the homogeneous or different species). Studies in which virulence is shown to increase during parasite-host interaction, as in Eberts (1994) experiment with Daphnia magna, postulate a synthesis of traditionally discrete factors to predict a coevolutionary outcome. Authors given to habitually single-valued function the word decrease before the word virulence are encouraged to replace the former with modulate, which emphasizes the need for an inclusive, predictive substitution class for parasite-host interaction. Evolutionary history... If you want to name a full essay, lodge it on our website: OrderCustomPaper.com
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