Document 0267
 DOCN  M95B0267
 TI    The population dynamics of vertically and horizontally transmitted
       parasites.
 DT    9511
 AU    Lipsitch M; Nowak MA; Ebert D; May RM; Department ofZoology, University
       of Oxford, U.K.
 SO    Proc R Soc Lond B Biol Sci. 1995 Jun 22;260(1359):321-7. Unique
       Identifier : AIDSLINE MED/95357368
 AB    We analyse a model of the transmission dynamics of a parasite
       transmitted both vertically and horizontally. The basic reproductive
       ratio (R0) of the parasite is shown to be a sum of horizontal and
       vertical components. We derive expressions for the equilibrium
       prevalence of infection for a mixture of horizontal and vertical
       transmission; prevalence can reach 100% if transmission is sufficiently
       high. At the endemic equilibrium, if prevalence is high, most
       transmission will in general be vertical, but horizontal transmission
       rates must be high to reach and stably maintain such an equilibrium.
       Surprisingly, for such parasites the highest equilibrium rates of
       vertical transmission are observed when horizontal transmission is very
       effective. We discuss the implications for assessing the importance of
       horizontal v. vertical transmission from field data, and we suggest some
       implications for the evolution of virulence.
 DE    Animal  *Disease Transmission, Horizontal  *Disease Transmission,
       Vertical  Human  HIV Infections/EPIDEMIOLOGY/TRANSMISSION  HTLV-I
       Infections/EPIDEMIOLOGY/TRANSMISSION  Mathematics  *Models, Statistical
       Parasitic Diseases/EPIDEMIOLOGY/*TRANSMISSION  *Population Dynamics
       Prevalence  Support, Non-U.S. Gov't  Virus
       Diseases/EPIDEMIOLOGY/*TRANSMISSION  JOURNAL ARTICLE

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