Lasse Ruokolainen

Social behaviour and gut microbiota in red‐bellied lemurs (Eulemur rubriventer): In search of the role of immunity in the evolution of sociality

Vertebrate gut microbiota form a key component of immunity and a dynamic link between an individual and the ecosystem. Microbiota might play a role in social systems as well, because microbes are transmitted during social contact and can affect host behaviour. Combining methods from behavioural and molecular research, we describe the relationship between social dynamics and gut microbiota of a group-living cooperative species of primate, the red-bellied lemur (Eulemur rubriventer). Specifically, we ask whether patterns of social contact (group membership, group size, position in social network, individual sociality) are associated with patterns of gut microbial composition (diversity and similarity) between individuals and across time. Red-bellied lemurs were found to have gut microbiota with slight temporal fluctuations and strong social group-specific composition. Contrary to expectations, individual sociality was negatively associated with gut microbial diversity. However, position within the social network predicted gut microbial composition. These results emphasize the role of the social environment in determining the microbiota of adult animals. Since social transmission of gut microbiota has the potential to enhance immunity, microbiota might have played an escalating role in the evolution of sociality.

Urban environment predisposes dogs and their owners to allergic symptoms

Our companion-animals, dogs, suffer increasingly from non-communicable diseases, analogous to those common in humans, such as allergic manifestations. In humans, living in rural environments is associated with lower risk of allergic diseases. Our aim was to explore whether a similar pattern can be found in dogs, using a nation-wide survey in Finland (n = 5722). We characterised the land-use around dog’s home at the time of birth as well as around its current home, and described several lifestyle factors. The severity of owner-reported allergic symptoms in dogs was estimated with a comprehensive set of questions, developed by experts of canine dermatology. Also, the prevalence of diagnosed allergies in dog owners was recorded. The results indicate that allergic symptoms are more prevalent in urban environments both in dog owners and in dogs (accounting the effect of dog breed). Several factors related to rural living, such as bigger family size and regular contact with farm animals and other pets, were also protective against allergic symptoms in dogs. Interestingly, allergic dogs were more likely to have allergic owners than healthy dogs were. Therefore, we suggest that the mutual presence of allergic symptoms in both species indicates common underlying causal factors of allergic diseases.

Spatial disease dynamics of free-living pathogens under pathogen predation

The epidemiological dynamics of potentially free-living pathogens are often studied with respect to a specific pathogen species (e.g., cholera) and most studies concentrate only on host-pathogen interactions. Here we show that metacommunity-level interactions can alter conventional spatial disease dynamics. We introduce a pathogen eating consumer species and investigate a deterministic epidemiological model of two habitat patches, where both patches can be occupied by hosts, pathogens, and consumers of free-living pathogens. An isolated habitat patch shows periodic disease outbreaks in the host population, arising from cyclic consumer-pathogen dynamics. On the other hand, consumer dispersal between the patches generate asymmetric disease prevalence, such that the host population in one patch stays disease-free, while disease outbreaks occur in the other patch. Such asymmetry can also arise with host dispersal, where infected hosts carry pathogens to the other patch. This indirect movement of pathogens causes also a counter-intuitive effect: decreasing morbidity in a focal patch under increasing pathogen immigration. Our results underline that community-level interactions influence disease dynamics and consistent spatial asymmetry can arise also in spatially homogeneous systems.

Landscape structure and ecology influence the spread of a bat fungal disease

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Population Dynamics, Invasion, and Biological Control of Environmentally Growing Opportunistic Pathogens

In this chapter, we analyze environmentally growing opportunistic diseases, which are a growing threat to human health, food production, and wildlife. The traditional treatment methods for opportunist diseases often fail because environmentally growing opportunist pathogens can utilize outside-host environmental resources for growth and can reside indefinitely in the environmental reservoirs. Moreover, environmental growth may promote high virulence because the trade-off between virulence and transmission can be weak or absent. Moreover, as multicellular organisms are a relatively rich resource compared to the surrounding environment, transition from free-living organism into an opportunist pathogen is a potential pathway through which novel, obligate pathogens emerge. We show that the environmental growth strategy can profoundly change the epidemiological dynamics because the pathogen faces environmental variability and outside-host food web interactions such as competition, predation, and parasitism. The contrasting evolutionary challenges between the outside-host environment and host immune responses likely play an important role in the epidemiological dynamics. Understanding the conditions that promote or hinder the spread of already existing, as well as the invasion of novel, environmentally growing opportunistic diseases is the key for controlling this class of infectious diseases. This chapter aims to give the reader a view on the studies made so far regarding environmentally growing opportunist diseases and present ideas on how the outside-host abiotic and biotic environment could be utilized in pathogen control.