Could parasites destabilize mouse populations? The potential role of Pterygodermatites peromysci in the population dynamics of free-living mice, Peromyscus leucopus

Center for Infectious Disease Dynamics, Biology Department, 208 Mueller Laboratory, Pennsylvania State University, University Park, PA 16802, USA
International journal for parasitology (Impact Factor: 3.87). 09/2009; 39(11):1253-1262. DOI: 10.1016/j.ijpara.2009.02.025


Peromyscus leucopus populations exhibit unstable population dynamics. Mathematical models predict instability with chronic parasite infections that reduce host fecundity when the parasite distribution within the host population is close to random. We examined the role the nematode Pterygodermatites peromysci may play in influencing the dynamics of these mice. There were seven gastrointestinal worms infecting mice. Pterygodermatites peromysci was the most prevalent and varied seasonally from 12.3% in November to 36.0% in July. Prevalence was higher in adults (30.8%) than juveniles (4.6%) and there were no statistical differences in prevalence or intensity between the sexes. Overall the distribution was random; the relationship between log variance and log mean of P. peromysci intensity from 17 sites was not significantly different from unity. There were significant relationships between infection and breeding condition, suggesting parasites could be the cause of reduced female breeding. A generalized linear model found the likelihood of P. peromysci infection in adults increased with body mass, the presence of other helminths, and when hosts were in breeding condition. Likewise, the intensity of infection was positively related to co-infections and body mass. Pterygodermatites peromysci infection was associated with the presence of the oxyurid nematode Syphacia peromysci but co-infection was lower in females than males. Amongst females, co-infection was greater when breeding, particularly during lactation. The P. peromysci age-intensity relationship increased with age and rose to an asymptote as expected for a parasite with constant mortality and no acquired immunity. Overall, P. peromysci had a random distribution and was associated with reduced breeding; we discuss how these destabilizing processes may influence the dynamics of P. leucopus.

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    • "Endoparasites with indirect life cycles (i.e., requiring multiple host species, in contrast to direct life cycles involving one host species) spend part of their life cycle in invertebrate hosts. For example, Pterygodermatities peromysci, a common nematode endoparasite of the white-footed mouse (Peromyscus leucopus) in the eastern USA (Vandegrift and Hudson 2009, Grear et al. 2012), requires an arthropod intermediate host (camel crickets, Orthoptera) to complete its life cycle (Luong and Hudson 2012). Furthermore, although some ectoparasites, such as lice, are permanent, and do not leave hosts except to disperse, others, such as fleas and ticks, are intermittent parasites, which may spend substantial time off their hosts, and these free-living stages may be reduced by forest fire. "
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    • "We only included mice that were ! 15 g because juvenile mice are rarely infected with P. peromysci (Vandegrift & Hudson 2009), and the long development time of P. peromysci suggests that detection via faecal egg output would produce higher type II error compared to older mice. To test for differences between nonbreeding, breeding but nonpregnant and pregnant female mice, "
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