Ecology ofBorrelia burgdorferi sensu latoin Europe: transmission dynamics in multi-host systems, influence of molecular processes and effects of climate change

Abstract

The analysis of different multi-host systems suggests that even hosts that are not capable of transmitting Borrelia burgdorferi sensu lato (s.l.) to the tick vector, Ixodes ricinus, or that are secondary reservoirs for these agents contribute to the intensity of transmission and to the overall risk of Lyme borreliosis, through the process of vector augmentation and pathogen amplification. On the other hand, above certain threshold densities, or in the presence of competition with primary reservoir hosts or low attachment rate of ticks to reservoir hosts, incompetent or less competent hosts may reduce transmission through dilution. The transmission of B. burgdorferi s.l. is affected by molecular processes at the tick-host interface including mechanisms for the protection of spirochaetes against the host's immune response. Molecular biology also increasingly provides important identification tools for the study of tick-borne disease agents. Ixodes ricinus and B. burgdorferi s.l. are expanding their geographical range to northern latitudes and to higher altitudes through the effects of climate change on host populations and on tick development, survival and seasonal activity. The integration of quantitative ecology with molecular methodology is central to a better understanding of the factors that determine the main components of Lyme borreliosis eco-epidemiology and should result in more accurate predictions of the effects of climate change on the circulation of pathogens in nature.

The wild life of tick-borne pathogens

“…To our knowledge, this review is the first to quantify the relative importance of host species for the different stages of I. ricinus, and our calculations support the widely held idea that small rodents are the most important hosts in feeding larval I. ricinus, that birds and rodents feed most of the nymphs, and that ungulates are the main hosts for adult I. ricinus 36,62 . We found that rodents and thrushes contribute most to the pool of B. burgdorferi infected nymphs.…”

“…Both in Europe and in North America, I. ricinus and I. scapularis populations have spread and increased in density in recent decades, most probably due to a multitude of man-made changes to the environment, which has resulted in an increase in Lyme disease incidence 49,61 . Lyme disease risk is determined by multiple biological, environmental and societal factors 8,62,63 . These can be split into two distinct groups, 1) factors determining the number of questing Ixodes ticks infected with B. burgdorferi, and 2) factors determining the level of human exposure to ticks 39 .…”

“…Although there have been several studies carried out on particular sites 72 or on various classes of vertebrates 73 , and some descriptive reviews have been published 62,74,75 , there is no quantitative review that integrates data on a host assemblage comprising a wide range of vertebrate species. Here, we used a data driven approach to quantify the contribution of various vertebrate host species to feeding I. ricinus ticks, and transmitting B. burgdorferi to feeding larvae, to infer a mechanism that could support the apparent increase in Lyme borreliosis incidence in Europe.…”

Prevalencia de Borrelia burgdorferi sensu lato en roedores sinantrópicos de dos comunidades rurales de Yucatán, México

“…El mantenimiento de B. burgdorferi s.l., así como de otros agentes patógenos zoonóticos transmitidos por garrapatas, depende de la abundancia de los reservorios y vectores competentes, y de la interacción entre huésped y vector, por lo cual la relación entre garrapatas del género Ixodes, la espiroqueta y los mamíferos huésped ha sido objeto de numerosos estudios (12,13). En Europa y Estados Unidos se han detectado muchas especies de mamíferos como reservorios competentes, pero a los roedores se los ha implicado como los principales reservorios naturales de B. burgdorferi s.l.…”

Study of the Protein Complex, Pore Diameter, and Pore-forming Activity of the Borrelia burgdorferi P13 Porin

“…lack genes involved in the biosynthesis of amino acids, fatty acids, and nucleotides pointing to the need of getting additional nutrients from their different hosts (8). These molecules must be taken up from the vertebrate hosts including birds or the invertebrate tick vector (9,10). The first step in nutrient uptake in Gram-negative bacteria is accomplished by porins.…”