Multiple Hosts and Lyme Disease
Posted by ajcann on May 16, 2008
Pathogenic microbes are emerging and re-emerging at an alarming rate. Of the 175 emerging infectious diseases of humans, 132 are zoonotic, residing in wildlife reservoir species and occasionally transmitted to humans either directly or via an intermediate vector. Zoonotic pathogens are not specialists on any single species, they can infect humans and at least one non-human animal. A robust understanding of the transmission cycle in nature that governs the distribution and abundance of pathogens, and thus contact with humans, is essential for the effective control of emerging infectious diseases. This paper investigates the degree to which the zoonotic pathogen that causes Lyme disease, Borrelia burgdorferi, is maintained and amplified by multiple reservoir host species.
Conspicuous impacts of inconspicuous hosts on the Lyme disease epidemic
Proc Biol Sci. 2008 275: 227-235
Emerging zoonotic pathogens are a constant threat to human health throughout the world. Control strategies to protect public health regularly fail, due in part to the tendency to focus on a single host species assumed to be the primary reservoir for a pathogen. Here, we present evidence that a diverse set of species can play an important role in determining disease risk to humans using Lyme disease as a model. Host-targeted public health strategies to control the Lyme disease epidemic in North America have focused on interrupting Borrelia burgdorferi transmission between blacklegged ticks and the putative dominant reservoir species, white-footed mice. However, B. burgdorferi infects more than a dozen vertebrate species, any of which could transmit the pathogen to feeding ticks and increase the density of infected ticks and Lyme disease risk. Using genetic and ecological data, we demonstrate that mice are neither the primary host for ticks nor the primary reservoir for B. burgdorferi, feeding 10% of all ticks and 25% of B. burgdorferi-infected ticks. Inconspicuous shrews feed 35% of all ticks and 55% of infected ticks. Because several important host species influence Lyme disease risk, interventions directed at a multiple host species will be required to control this epidemic.
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