Factors of Parasitic Virulence.

Factors of Parasitic Virulence ABSTRACT wherefore do some(a) parasites kill the troops they opine upon while others coexist with their host? Two prime factors determine parasitic sourness: the modality in which the parasite is transmitted, and the developmentary write up of the parasite and its host. Parasites which have annex a new host species flow to be more(prenominal) irate than parasites which have coevolved with their hosts. Parasites which be transmitted horizontally turn tail to be more acetous than those transmitted vertically. It has been assumed that parasite-host interactions necessarily evolve toward lower tartness. This is contradicted by studies in which moroseness 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 severity in paras ite-host systems by integrating evolutionary and transmissibility factors. INTRODUCTION Why do certain(prenominal) parasites bear witness high levels of virulence at heart their host populations while others exhibit low virulence? The devil prime factors most frequently cited (Esch and Fernandez 1993, Toft et al. 1991) are evolutionary history and mode of transmission. In congruously 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 slight vi rulent than parasites transmitted horizontal! ly (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 procedure the word decrease before the word virulence are encouraged to replace the former with modulate, which emphasizes the need for an inclusive, predictive image for parasite-host interaction. Evolutionary history... If you want to name a full essay, ordering it on our website: OrderCustomPaper.com

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