Modelling hantavirus in fluctuating populations of bank voles: the role of indirect transmission on virus persistence

Abstract

Summary 1.Using field data published in the literature, we investigated pathogen dynamics and conditions of persistence in a mathematical model of the bank vole ( Clethrionomys glareolus )-Puumala hantavirus system. The host population is assumed to have a 3-year periodic cycle. The duration of very low host density is critical for virus transmission and survival. 2. Field epidemiological data strongly suggested a transmission of the hantavirus by the contaminated environment. We thus studied whether this 'indirect' transmission affected the virus persistence in the host population. 3. The model assumptions were derived from the following conditions found in the literature: (1) there is no additional mortality nor fecundity loss due to the virus in infected hosts, thus the cyclic demographical pattern is not due to the virus; (2) no remission has been observed, thus we did not consider the existence of recovered individuals; (3) adult females are territorial and juveniles disperse to find a new territory and reach sexual maturity. A fragmented landscape was assumed to occur: individuals can live in favourable or unfavourable patches. 4. The model was a compartmental model; the population was structured into susceptible or infectious individuals. We considered two age classes, juveniles and adults, and two sites (populations) connected by juvenile dispersal. 5. Model dynamics accurately predicted the cyclic trend in disease prevalence as observed in epidemiological studies. They also showed that indirect transmission significantly increased the probability for the virus to persist during the low-density period of the host population. More precisely, even a low survival rate of the virus outside the host was sufficient to decrease extinction risk of the infection by stochastic events. 6. Elasticity analysis showed a high robustness of the model to changes in the parameters of indirect transmission but a high sensitivity to changes in adult density.

Different mechanisms of transmission of the microsporidium Octosporea bayeri: a cocktail of solutions for the problem of parasite permanence

“…Frequent periods of low host density may thus select for an increase in spore longevity. A similar scenario has been recently modelled for the Hantavirus-Vole system (Sauvage et al 2003). Their theoretical results confirm the argument above : by adding survival outside the host, the permanence and prevalence of the pathogen in the population increased.…”

Evolution of microparasites in spatially and genetically structured host populations: The example of RHDV infecting rabbits

“…Long infectious period with low levels of both transmissibility and virulence can be one such strategy. Alternative mechanisms of extension of the pathogen infectivity period beyond host infection are frequently observed in the field, as exemplified by the parvovirus infecting cats (Berthier et al, 2000) or the hantavirus infecting voles (Kallio et al, 2006;Sauvage et al, 2003) that can remain infectious in the ground. Myxoma virus, another virus infecting rabbits, provides another interesting example.…”

Accumulation of point mutations and reassortment of genomic RNA segments are involved in the microevolution of Puumala hantavirus in a bank vole (Myodes glareolus) population

“…In rodent populations, hantaviruses are transmitted horizontally, either through direct contact or via infectious aerosols generated by contaminated host urine, faeces and saliva (Gavrilovskaya et al, 1990;Bernshtein et al, 1999). The indirect mode of transmission and virus survival outside the host increase the chances for the virus to persist in the host population (Sauvage et al, 2003;Kallio et al, 2006a). The transfer of antibodies from an infected mother to its progeny provides them with a temporary immunity against the infection that lasts up to 3.5 months (Gavrilovskaya et al, 1990;Bernshtein et al, 1999;Kallio et al, 2006b).…”