An eco‐epidemiological modeling approach to investigate dilution effect in two different tick‐borne pathosystems

Disease (re)emergence appears to be driven by biodiversity decline and environmental change. As a result, it is increasingly important to study host-pathogen interactions within the context of their ecology and evolution. The dilution effect is the concept that higher biodiversity decreases pathogen transmission. It has been observed especially in zoonotic vector-borne pathosystems, yet evidence against it has been found. In particular, it is still debated how the community (dis)assembly assumptions and the degree of generalism of vectors and pathogens affect the direction of the biodiversity-pathogen transmission relationship. The aim of this study was to use empirical data and mechanistic models to investigate dilution mechanisms in two rodent-tick-pathogen systems differing in their vector degree of generalism. A community was assembled to include ecological interactions that expand from purely additive to purely substitutive. Such systems are excellent candidates to analyze the link between vector ecology, community (dis)assembly dynamics, and pathogen transmission. To base our mechanistic models on empirical data, rodent live-trapping, including tick sampling, was conducted in Wales across two seasons for three consecutive years. We have developed a deterministic single-vector, multi-host compartmental model that includes ecological relationships with non-host species, uniquely integrating theoretical and observational approaches. To describe pathogen transmission across a gradient of community diversity, the model was populated with parameters describing five different scenarios differing in ecological complexity; each based around one of the pathosystems: Ixodes ricinus (generalist tick) - Borrelia burgdorferi and I. trianguliceps (small mammals specialist tick) - Babesia microti. The results suggested that community composition and inter-specific dynamics affected pathogen transmission with different dilution outcomes depending on the vector degree of generalism. The model provides evidence that dilution and amplification effects are not mutually exclusive in the same community, but depend on vector ecology and the epidemiological output considered (i.e. the “risk” of interest). In our scenarios, more functionally diverse communities resulted in fewer infectious rodents, supporting the dilution effect. In the pathosystem with generalist vector we identified a hump shaped relationship between diversity and infections in hosts, while for that characterized by specialist tick, this relationship was more complex and more dependent upon specific parameter values

Living in Islands of Forests: Feeding Ecology of Alouatta palliata in Forest Fragments at La Suerte Biological Field Station, Costa Rica

Facets of habitat quality which allow species persistence in forest fragments are an important aspect for primate conservation. Mantled howler monkeys (A. palliata) seem to be tolerant of habitat fragmentation, though the limits of this flexibility are not yet clear. In some areas, howler monkey densities in small, primary forest fragments are among the highest ever recorded for the species. We hypothesize that if high density is also determined by habitat carrying capacity; primaryvegetation should provide higher quality resources. Alternatively, if density is just the consequence of crowding, this would decrease the quality of the diet compared to that of monkeys living in non-crowded forests. To test these hypotheses, we studiedfour howler monkey groups at La Suerte Biological Field Station, North-eastern Costa Rica. Two groups occurred in a small primary forest with high howler density, while two groups lived in a large secondary forest with lower density. We collected behavioural data via a 5-min Focal Animal Sampling to estimate activity, habitat use and diet. Food samples were also collected and then analyzed to evaluate their nutritional contents. Moreover, we registered GPS coordinates and estimated home-ranges and mean inter-location distances. Our results show that primary forest food samples contained a significantly lower amount of fiber and a higher protein/fiber ratio than samples from the secondary habitat. Also, primary forest groups used larger feeding trees and moved substantially less than secondary forest groups. Our results support the hypothesis that the primary forest provides higher quality resources than the secondary habitat and, as a possible consequence, howler monkeys living in the latter have to move more to meet their energy requirements

Maderas Rainforest Conservancy: A One Health approach to conservation

Maderas Rainforest Conservancy (MRC) was incorporated as a conservation nonprofit organization in 2008, and manages two sites where biological field courses have been offered since the 1990s: La Suerte Biological Research Station in Costa Rica, and Ometepe Biological Research Station in Nicaragua. MRC employs a One Health approach to conservation education, and can serve as a model for other biological field sites. The Nicaraguan Molina family, who owns the sites, partnered with primatologist Paul Garber in 1994 to develop a primate field course aimed at introducing university students to field research. Through using their land to further conservation education and research, the Molina family has preserved the forest and engaged the local communities near their sites. Eight graduate theses and 46 refereed publications have been completed since 2010 based on research undertaken at MRC sites. While primate field courses have been offered at least once annually since 1994 and remain popular, a range of other ecological courses are now additionally offered. MRC operates from a One Health perspective, engaging in forest restoration and ecological monitoring projects, and has gradually expanded community outreach initiatives. MRC now conducts regular medical and veterinary missions in the communities surrounding the research stations which provide health care to local people and limit the population growth of domestic animals, thereby increasing the survival of wild animals. MRC is also active in ESL-teaching and conservation education, and funds Proyecto Jade, which empowers local women to make and sell organic jewelry. Through these programs, MRC works to help the local communities live more sustainably with the environment around them. MRC\u27s support of research, commitment to education, medical and veterinary missions, and outreach initiatives to the local community all work together for the well-being of both the people and the environment, thus exemplifying the One Health perspective