Age‐related effects of chronic hantavirus infection on female host fecundity

Abstract

Summary1. Pathogens often cause detrimental effects to their hosts and, consequently, may influence host population dynamics that may, in turn, feed back to pathogen transmission dynamics. Understanding fitness effects of pathogens upon animal host populations can help to predict the risks that zoonotic pathogens pose to humans. 2. Here we determine whether chronic infection by Puumala hantavirus (PUUV) affects important fitness-related traits, namely the probability of breeding, reproductive effort and mother and offspring condition, in the bank vole (Myodes glareolus). Using 9 years empirical data in a PUUV endemic area in Central Finland, we found differences between reproductive characteristics of PUUV-infected and uninfected female bank voles. 3. Young infected females had a significantly higher, and old individuals lower, likelihood of reproducing than uninfected animals during the middle of the breeding season. The implication is that PUUV infection may have long-term deleterious effects that are observed at old age, while in young individuals, the infection may enhance breeding probability by directing resources towards current breeding. 4. Moreover, PUUV infection was related with the mother's body condition. Infected mothers were in poorer condition than uninfected mothers in the early breeding season, but were in better condition than uninfected mothers during the middle of the breeding season. Offspring body condition was positively associated with mother's body condition, which, in turn, was related to the PUUV infection status of the mother. 5. Our findings indicate that chronic infection may affect the reproduction of female hosts, but the effect is dependent on the host age. The effect of chronic hantavirus infection was small and density-independent and hence unlikely to contribute to the cyclic population dynamics of the host. However, the effects on a female's reproductive output might affect the abundance of young susceptible individuals in the population and hence influence the transmission and persistence of the pathogen. Although experimental and long-term capture-mark-recapture studies are required to further clarify the fitness effects of hantavirus infection and their consequences for pathogen dynamics, this study shows that the infection may have complex effects that are dependent on the age of the individual and the time of the breeding season.

No measurable adverse effects of Lassa, Morogoro and Gairo arenaviruses on their rodent reservoir host in natural conditions

“…Such complex relationships between parasite infection and host fitness were indeed observed in other rodent-borne diseases. For example, infection of Puumala hantavirus in bank voles ( Myodes glareolus ) was initially assumed to be asymptomatic [51–53] but recent long-term field studies observed negative effects on the survival probability and an equivocal impact on the fecundity of females [36, 54, 55]. An important difference between Old World arenaviruses and hantaviruses, however, is that the latter causes persistent infections in their reservoir hosts [56], while the former infects their hosts mainly acutely [29, 43].…”

“…This might be likely, as it has been shown that LCMV can severely disrupt hormonal regulation in laboratory mice [25, 65, 66]. Similarly, Kallio et al [36] suggest that infection with Puumala hantavirus enhances breeding in young female bank voles, but not in old ones.…”

“…Therefore, if one wants to investigate the effect of infection on an age-dependent host variable (e.g. body mass, head-body length or sexual maturity), the effect of age should be disentangled from that of the variable [36]. …”

Preliminary insights into the genetics of bank vole tolerance to Puumala hantavirus in Sweden

“…The bank vole, Myodes glareolus, is the specific reservoir host of the hantavirus Puumala (PUUV), the causative agent of nephropathia epidemica (NE) in humans (Brummer-Korvenkotio, Henttonen, & Vaheri, 1982). In M. glareolus, PUUV infections are chronic (Hardestam et al, 2008;Voutilainen et al., 2015) and mainly asymptomatic (Bernshtein et al, 1999), although small negative effects on the fitness of the host have been reported (Kallio et al, 2007;Kallio, Helle, Koskela, Mappes, & Vapalahti, 2015;Tersago, Crespin, Verhagen, & Leirs, 2012). The tolerance of rodents to hantavirus infections has mostly been examined by comparing the immune response between reservoir and non reservoir hosts (see for reviews Easterbrook & Klein, 2008, Schountz & Prescott, 2014.…”

Intergenerational fitness effects of the early life environment in a wild rodent

“…This is in contrast with laboratory rats (Pinheiro, Salvucci, Aguila, & Mandarim‐de‐Lacerda, ), where protein restriction increased F2's mass at birth and decreased male F2 adult body mass. While we did not find intergenerational effects due to protein restriction, we might have overlooked other phenotypic traits, such as pathogen susceptibility (Monaghan, ), which can affect fitness‐related traits in F2 besides winter survival, for example reproduction (Hakkarainen et al, ; Kallio, Helle, Koskela, Mappes, & Vapalahti, ; Mills, ). We propose that a protein‐restricted early life impacts bank vole phenotype, but it is of little consequence to fitness in natural settings.…”