In today's landscape of zoonotic pathogen outbreaks, the dilution effect theory, i.e., the theory that greater biodiversity can help curb pathogen transmission among wildlife, has gained significant attention. However, the positive link between animal diversity and pathogen richness urges us to apply this concept with caution. It is crucial to explore how conservation biology can safeguard human health by preventing the emergence of zoonotic diseases. By investigating the implications of conservation strategies on animal communities and pathogen transmission as well as the adaptive capabilities of pathogens, we propose that biodiversity conservation based on small reserves can effectively reduce pathogen spread in wildlife, provided certain measurable conditions are met. Given the urgent need to tackle both zoonoses disease emergence and biodiversity loss, these interventions should be prioritized and implemented without delay.

Concerns about the prospect of a global pandemic have been triggered many times during the last two decades. These have been realized through the current COVID-19 pandemic, due to a new coronavirus SARS-CoV2, which has impacted almost every country on Earth. Here, we show how considering the pandemic through the lenses of the evolutionary ecology of pathogens can help better understand the root causes and devise solutions to prevent the emergence of future pandemics. We call for better integration of these approaches into transdisciplinary research and invite scientists working on the evolutionary ecology of pathogens to contribute to a more “solution-oriented” agenda with practical applications, emulating similar movements in the field of economics in recent decades.

Despite important implications for biological conservation and public health, the potential generality of a prophylactic effect of biodiversity on zoonotic pathogen transmission (e.g., dilution effect) remains hotly debated, potentially because existing studies focus on different kinds of analyses as well as different spatial scales. Here, we test if changing the spatial scale of analysis can affect the detection of a relationship between hantavirus infection prevalence and rodent species richness throughout the World. We found that these relationships are always negative, whatever the spatial scale. Nevertheless, the dilution effect magnitude decreases if larger spatial scales are considered. These results, which remain consistent for all regions, highlight that the dilution effect should be a general phenomenon for hantaviruses, but that its detection can be hampered by the spatial scale considered. Finally, we discuss the mechanisms that can hinder the observation of a dilution effect and the necessity to consider other host-pathogen systems.

The apicomplexan parasite Toxoplasma gondii has been found in more than 350 species of homoeothermic vertebrates in diverse climates and geographic areas. In most animals, T. gondii produces mild or asymptomatic infection. However, acute and hyperacute toxoplasmosis is associated with high mortality rates observed in Neotropical primates (NP) in captivity. NP are distributed in 20 countries across the Americas, and although infection has been reported in certain countries and species, toxoplasmosis in the wild and its impact on NP population survival is unknown. Differences among species in exposure rates and disease susceptibility may be due in part to differences in host behavior and ecology. Costa Rica has four species of NP, howler (Alouatta palliata), spider (Ateles geoffroyi), capuchin (Cebus imitator), and squirrel monkeys (Saimiri oerstedii). Here we report for the first time NP exposure to T. gondii using a modified agglutination test (MAT) in 245 serum samples of NP (198 wild and 47 from captivity) from Costa Rica. Associations of serostatus with environmental (forest cover, annual mean temperature), anthropogenic (human population density), and biological (sex) variables in howler and capuchin monkeys were evaluated. The seroprevalence among wild NP was 11.6% (23/198), compared with 60% (28/47) in captive monkeys, with significant differences between species (P <0.05), suggesting behavior and ecology influences. In general, antibody titers were low for wild NP (<128) and high for captive NP (>8192), suggesting higher exposure due to management factors and increased life span in captivity. Seropositivity in howler monkeys was positively related to forest cover and inversely related to annual rainfall. For capuchins, annual rainfall was inversely related to seropositivity. Surveillance of T. gondii in NP in captivity and in the wild is required to understand drivers of the infection and develop novel strategies to protect them.