Lien Luong

My research interests include the ecology of infectious diseases and the evolutionary ecology of parasite-host interactions.

I am currently working on a gastrointestinal nematode(Pterygodermatites peromysci) that infects the white-footed mouse (Peromyscus leucopus). The parasite has a complex life-cycle, requiring passage through an intermediate host, a camel cricket, for transmission. I use a combination of field and laboratory experiments to investigate questions such as:

• What key hosts are responsible for transmission?
• How does intrinsic variation between individual hosts affect parasite transmission dynamics?
  
• Do interactions between microparasites and macroparasites influence host susceptibility and infectiousness?
• What factors are driving spatial and temporal variation in parasite transmission?
• What factors constrain parasite establishment, and what are the consequences for parasite distribution in a host population?
  
• How does host foraging ecology influence the transmission of trophically-transmitted parasites?
  

Influence of host characteristics on parasite transmission

We examined the importance of host sex on the transmission of a trophically transmitted parasite (P. peromysci) where there is no obvious sex bias in infection. In a field study, we experimentally reduced infection levels in either male or female white-footed mice (P. leucopus) on independent trapping grids with an anthelmintic and recorded the subsequent infection levels in the intermediate host, the camel cricket (Ceuthophilus pallidipes). We found that the intensity of infection in crickets was higher on the grids where females were treated compared to the grids where males were treated. These findings indicate that male hosts contribute disproportionately more infective stages to the environment and may therefore be responsible for the majority of parasite transmission even when there is no discernable sex biased infection.

Identifying the "super-shedder": heterogeneities in host infectiousness

A majority of parasite transmission can be attributed to a small portion of infected hosts in a population, such that individuals or specific groups of individuals serve as the primary shedders of the infectious stage. A common assumption in many studies is that heavily infected individuals are responsible for much of the transmission, but this may not be the case. Intrinsic differences between individual host in susceptibility and/or exposure can lead to significant variation in the shedding rate of infectious stages. Interactions with other parasites and pathogens can also influence parasite infectiousness, either directly via density-dependent competition or indirectly through a host-mediated process(es) involving the immune response.