Avoidance of bacterial and viral threat is affected by infection status in a terrestrial snail.

Parasites and infections are one of the major costs associated with group living and high host density. Although infection threat can influence the behavior of both uninfected and infected individuals, investigations have focused on the responses of uninfected individuals. Here we describe the effects on, and response to, terrestrial snails, Cepaea nemoralis, treated with either a bacterial or viral pathogenic stimulus. Brief exposure of untreated (uninfected) snails to the mucus associated chemical cues of snails acutely treated with either the bacterial cell wall component, lipopolysaccharide (LPS), or the viral mimetic, polyinosinic:polycytidylic acid (Poly I:C), elicited active behavioral avoidance and antinociceptive responses (decreased sensitivity to noxious stimuli). Treated (infected) snails also avoided and displayed antinociceptive responses to the chemical cues of snails with either a simulated bacterial or viral infection; however, each according to their own treatment (infection) status. LPS (bacterial) treated snails avoided the cues of Poly I:C (viral), but not LPS, treated conspecifics, whereas Poly I:C treated snails primarily avoided the mucus associated cues of LPS, but not Poly I:C, treated individuals. These findings show that chemical mediated behavioral avoidance of bacterial and viral threat is affected by both the nature of the infection threat and the infection status of the individual.