COSEATIBO

Co-evolution and implications of vector adaptation: A case study on seabird ticks and Borrelia

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 Obiettivo del progetto (Objective)

'Many emerging infectious diseases and novel agricultural pests are attributed to the adaptation and spread of parasitic organisms to new hosts, but almost nothing is known about the characteristics of parasites with this potential and the implications of this shift for interacting organisms. In vector organisms, those that exploit a host to which they will transmit a microparasite, the evolution of host-associated divergence may be of particular importance, especially for the evolution of the microparasites they carry. However, little work has been done on parasite adaptation involving multispecific interactions. Ticks are second only to mosquitoes in their global importance as disease vectors and they transmit numerous pathogens of medical and veterinary interest. These “vertebrate host-tick-micropathogen” systems therefore represent pertinent models to examine the evolution and implications of vector adaptation. In this scientific context, we aim to answer; 1) How readily ticks adapt to their host environments? 2) How does divergence in the vector affect the distribution of micropathogens? 3) What is the relative importance of the arthropod vector versus the vertebrate host in the evolution and epidemiology of vector-borne diseases? These questions will be addressed using two complimentary systems: the seabird ticks Ixodes uriae vector of Borrelia burgdorferi s.l., the pathogen responsible for human Lyme disease and Ornithodoros maritimus, and potential vector of relapsing fever Borrelia. Although the epidemiologies of both Lyme disease and relapsing fever have been widely studied in terrestrial ecosystems, the prevalence and spatial distribution of the associated bacteria in the marine ecosystem have been largely neglected. This project will shed light on the nature of host-associated adaptation in vectors and the influence of spatial structure on this process and will help determine the relative importance of vectors in the evolution of their micropathogens.'

Introduzione (Teaser)

Many emerging infectious diseases and agricultural pest are believed to be the result of parasites adapting to new hosts. Therefore, greater understanding is needed about parasites with this ability and the impact on interacting organisms.

Descrizione progetto (Article)

Organisms, such as ticks, which transmit parasitic organisms to a host, are known as 'vectors'. The Coseatibo project has investigated host specialisation in vectors to understand how these creatures influence disease transmission, spread, and the evolution of the parasite.

Researchers have studied two sorts of ticks found in sea birds that can transmit pathogens through their bite. The bacteria are of the genus Borrelia, which cause Lyme disease and relapsing fever in humans. The Coseatibo initiative will therefore provide valuable information about the role of seabirds in the large-scale spread of such disease.

Scientists have found that the genetic diversity of the tropical seabird tick (Ornithodoros capensis) is greater than expected. The technique used enabled several similar species to be identified within a single location. Results showed that at the local level host specialisation may play an important role in the diversification of tick species.

Project partners have sought to answer a number of questions, including how readily ticks adapt to their host environments. Researchers have also studied the importance of the tick vector compared to the host in the evolution and spread of vector-borne diseases.

Genetic diversity and population structure of marine Borrelia bacteria have also been studied in different seabirds in a range of geographic locations. This has enabled researchers to gain a better understanding of the pathogen?s diversity, evolution and interaction with terrestrial disease systems.

Findings by the Coseatibo project have provided scientists with a better understanding of the co-evolution of tick vectors and their pathogens in seabirds. This will provide valuable information regarding the spread of Lyme disease and relapsing fever through a route that previously has not been widely documented.