Primate reinfection with gastrointestinal parasites: behavioural and physiological predictors of parasite acquisition

Abstract

Infectious disease transmission is a cost of sociality in humans and other animals. Nevertheless, the mechanisms linking social behaviour to infection risk are poorly known. We conducted a field experiment to examine how host intrinsic traits, behaviour and physiology affect infection of nonhuman primates with gastrointestinal parasites. We measured rate to reinfection in a social group of red-capped mangabeys, Cercocebus torquatus, following chemotherapeutic treatment for parasite infections. By measuring behaviour, infection and glucocorticoid levels, we compared the relative effects of space sharing, directional contact and physiological stress on risk of acquiring new infections. We found that, within proximity networks, individuals that were central and well connected and that had a tendency to switch groups were at increased risk of infection with helminths. Protozoan infections, however, were acquired more uniformly across the population. In general, position in the social network and, in particular, space sharing appears to be more important than the immunosuppressive effects of physiological stress or host traits in determining risk of infection. Our results suggest that future studies of disease ecology within wildlife populations should focus on measures of network association in addition to individual host traits.

Changes in physiological stress and behaviour in semi-free-ranging red-capped mangabeys ( Cercocebus torquatus ) following antiparasitic treatment

“…Methodological details and assay validation are described in detail by Friant et al [25]. Interassay variation for the high pool was 18.3% and for the low pool was 22.2%, whereas intra-assay variation was 3.8% for the high pool and 7.9% for the low pool.…”

“…No immigration or emigration events took place, thereby limiting external changes in the social environment throughout the duration of the study. The population was provisioned three times daily, which lessened the effects of temporal variation in resource availability, but the animals still ate wild foods opportunistically and drank from a stream running through the enclosure [25]. Climate included a long wet season from April to November and a short dry season from November to March.…”

“…In June, the population was treated for parasites using orally administered metronidazole for protozoans, mebendazole for nematodes and praziquantel for cestodes and trematodes [25]. Faecal and behavioural sampling was conducted over three sampling periods: 30 days prior to treatment ( pre-treatment), and two 30-day post-treatment periods (post-treatment 1 and post-treatment 2).…”

“…One gram of faeces was taken from formalin-preserved samples and concentrated via faecal sedimentation for assessment of gastrointestinal parasites [25,36]. The entirety of the sediment was systematically examined at 10Â objective light magnification, and all helminth eggs and larvae and large protozoan trophozoites and cysts were counted.…”

“…Parasitic infection may inhibit an individual's ability to engage in energetically costly behaviours, such as challenging dominant individuals [23,24]. Furthermore, social contact and proximity can facilitate parasite transmission [25][26][27], such that animals may modify their behaviour directly to avoid infected conspecifics and reduce infection risk [28].…”