How Host Population Dynamics Translate into Time-Lagged Prevalence: An Investigation of Sin Nombre Virus in Deer Mice

Abstract

Human cases of hantavirus pulmonary syndrome caused by Sin Nombre virus are the endpoint of complex ecological cascade from weather conditions, population dynamics of deer mice, to prevalence of SNV in deer mice. Using population trajectories from the literature and mathematical modeling, we analyze the time lag between deer mouse population peaks and peaks in SNV antibody prevalence in deer mice. Because the virus is not transmitted vertically, rapid population growth can lead initially to reduced prevalence, but the resulting higher population size may later increase contact rates and generate increased prevalence. Incorporating these factors, the predicted time lag ranges from 0 to 18 months, and takes on larger values when host population size varies with a longer period or higher amplitude, when mean prevalence is low and when transmission is frequency-dependent. Population size variation due to variation in birth rates rather than death rates also increases the lag. Predicting future human outbreaks of hantavirus pulmonary syndrome may require taking these effects into account.

Hantavirus infections in fluctuating host populations: the role of maternal antibodies

“…Similar results have also been reported from other hantavirushost systems (Calisher et al 1999(Calisher et al , 2005Douglass et al 2001). A high influx of newborns during the breeding season may decrease hantavirus prevalence, and this 'juvenile dilution effect' has been proposed to be the mechanism through which the expected positive relationship between prevalence and abundance is lacking or delayed Davis et al 2005;Adler et al 2008).…”

“…During the breeding season, there was naturally an influx of young uninfected individuals. The decrease in hantavirus prevalence over a breeding season has generally been attributed to this influx Davis et al 2005;Adler et al 2008), and the seasonal variation in PUUV prevalence observed here and previously (Verhagen et al 1986;Escutenaire et al 2000;Sauvage et al 2002) may in part be caused by such a juvenile dilution effect . But it may often not be the whole story.…”

“…But it may often not be the whole story. Ultimately, increasing the host (especially susceptible host) density should facilitate transmission and increase infection prevalence Adler et al 2008). However, this increase may be substantially delayed if maternally protected individuals are prevalent in the host population, since this will delay the influx of susceptible individuals into Predictions are based on the best selected GLMM and are made in (a) for an individual with a body mass of 10 g and at fixed past and current bank vole abundances (both approximately 55 individuals, natural log-transformed value ¼ 4), and in (b) and (c) for an individual with a body mass of 20 g. GLMMs do not allow reliable confidence intervals to be applied to these curves, but standard errors for the model parameter estimates for (a-c) are given in table 1, table 3 and in the text, respectively.…”

“…Mills et al 1999;McCallum et al 2001;Begon et al 2002;Hudson et al 2002;Lloyd-Smith et al 2005), but this expectation is not always borne out. Davis et al (2005) and Adler et al (2008) have recently reviewed studies on the relationship between the prevalence of rodent-borne diseases and host abundance. For example, studies on hantaviruses (genus Hantavirus, family Bunyaviridae), carried by specific rodent or insectivore hosts and causing several human diseases in Eurasia and the Americas (Vaheri et al 2008), have shown great variation in this relationship.…”

Daily Movements and Microhabitat Selection of Hantavirus Reservoirs and Other Sigmodontinae Rodent Species that Inhabit a Protected Natural Area of Argentina

“…However, the density-dependent relationship is not completely clear due to confounding effects that occur during periods of rapid population growth. During periods of rapid population growth, the lack of vertical transmission leads to a dilution of susceptible rodents and reduced prevalence Adler et al 2008).…”