The role of seabirds of the Iles Eparses as reservoirs and disseminators of parasites and pathogens

Abstract

The role of birds as reservoirs and disseminators of parasites and pathogens has received much attention over the past several years due their high vagility. Seabirds are particularly interesting hosts in this respect. In addition to incredible long-distance movements during migration, foraging and prospecting, these birds are long-lived, site faithful and breed in dense aggregations in specific colony locations. These different characteristics can favor both the local maintenance and large-scale transmission of parasites and pathogens. The Iles Eparses provide breeding and feeding grounds for a large portion of seabird biodiversity, with over 3 million breeding pairs of at least 13 species. Breeding colonies on these islands are relatively undisturbed by human activities and represent natural metapopulations in which seabird population dynamics, movement and dispersal can be studied in relation to that of circulating parasites and pathogens. In this review, we summarize previous knowledge and recently-acquired data on the parasites and pathogens found in association with seabirds of the Iles Eparses. These studies have revealed the presence of a rich diversity of infectious agents (viruses, bacteria and parasites) carried by the birds and/or their local ectoparasites (ticks and louse flies). Many of these agents are widespread and found in other ecosystems confirming a role for seabirds in their large scale dissemination and maintenance. The heterogeneous distribution of parasites and infectious agents among islands and seabird species suggest that relatively independent metacommunities of interacting species may exist within the western Indian Ocean. In this context, we discuss how the patterns and determinants of seabird movements may alter parasite and pathogen circulation. We conclude by outlining key aspects for future research given the baseline data now available and current concerns in eco-epidemiology and biodiversity conservation.

Mesoscale spatiotemporal variability in a complex host-parasite system influenced by intermediate host body size

“…Contrarily, ectoparasites, which can be removed by hosts, can show different patterns of prevalence and aggregation. In such systems, the smaller or younger hosts accumulate greater parasite burdens than older hosts, as a likely consequence of higher susceptibility to infections of the former than the latter ( McCoy et al, 2016 ). Therefore, significant relationships between parasite exposure and prevalence, in addition with size-dependent patterns of stochasticity in parasite load could be observed in other complex host-parasite systems, at least those involving endoparasites that accumulate over host’ ontogeny.…”

“…However, extreme aggregation in host populations with low prevalence, such that a very small proportion of hosts carry a high parasite burden, might reduce the ability of the parasite to regulate the host population ( Anderson & May, 1978 ). Variations in “extrinsic” factors such as exposure to infective stages of parasites (hereafter referred to as “parasite exposure”) can generate parasite aggregation across hosts ( McCoy et al, 2016 ). However, “intrinsic” host-population factors, such as age and body-size structure, can significantly influence the links between variation in parasite exposure and aggregation ( Anderson & May, 1978 ).…”

“…In these interactions, parasite infective stages are trophically transmitted between definitive and intermediate hosts, so that variations in the abundance of the former imply significant variations in parasite exposure of the latter ( Latham & Poulin, 2003 ; Smith, 2007 ). For example, local increments in the abundance of migratory birds have been linked to increases in the prevalence of infectious diseases in intermediate hosts ( Altizer, Bartel & Han, 2011 ; McCoy et al, 2016 ). In addition, increases in seagull abundances can be followed by concomitant increments in per capita parasite loads in the intermediate host populations ( Latham & Poulin, 2003 ; Smith, 2007 ).…”

Parasites of seabirds: A survey of effects and ecological implications

“…Important to note is that the colonial nature of some species of birds may also make them more vulnerable to higher levels of parasites and pathogens as compared with birds that breed in isolation because of the contact between individuals at bird colonies (e.g. Boulinier et al, 2001Boulinier et al, , 2016McCoy et al, 2016). For example, in some cliff-nesting seabird species where there is little to no vegetation cover individuals may literally be covered in the faeces of those nesting above them (Fig.…”

Evaluating Functional Dispersal in a Nest Ectoparasite and Its Eco-Epidemiological Implications

“…Outside breeding, L. michahellis remains gregarious, concentrating around ports, harbors, and dumps (31). Because of its longevity, nest site fidelity, and seasonal breeding (22), the presence of this bird in the colony area is highly predictable for nest parasites like O. maritimus (32).…”