Generating super-shedders: co-infection increases bacterial load and egg production of a gastrointestinal helminth

Lass, Sandra; Hudson, Peter J.; Thakar, Juilee; Saric, Jasmina; Harvill, Eric; Albert, Réka; Perkins, Sarah E.

A cubic smoothing spline was fitted to the course of infection in the random models, which allowed potential nonlinear relationships between single and co-infection growth and establishment to be assessed. Likelihood ratio tests were used to compare the random model (shedding over time) in each analysis. A likelihood ratio test showed the spline was significant ( p , 0.05). As such, helminth egg shedding was significantly increased in co-infected compared with single-infected mice over the duration of the in vivo experiment ( p , 0.05). The period of egg shedding was not significantly different between single and co-infected hosts (negative binomial GLM: d.f. ¼ 1, p ¼ 0.056; figure 5a), although this was marginal at the 5 per cent level. One single-infected individual shed helminth eggs for 320 days while all other single-infected individuals shed eggs on average for 79 + 9 days (mean + s.e.; figure 5b ). This individual could be considered a 'super-shedder', although it is worth noting that super-shedding was not due to the presence of a secondary infection as these individuals were infected with a helminth-only.