![]() Communities with a high proportion of poor-quality hosts would then be expected to produce smaller populations of vectors. by the composition of the host community. Whenever host species differ strongly in host quality, the abundance of a generalist vector could be limited by the relative availabilities of the species comprising the host community-i.e. If some host species that are abundantly parasitized in nature are of sufficiently low quality that they strongly reduce tick fitness compared with other hosts, then those poor quality hosts might act as ecological traps ( Robertson & Hutto 2006). Variation in host quality appears to be caused by differences in either host-immune response ( Randolph 1979) or host grooming ( Ostfeld & Lewis 1999 Shaw et al. And Randolph (1979) showed that Ixodes tranguliceps ticks that fed on Apodemus sylvaticus were more likely to become engorged than were ticks that fed on laboratory mice when the hosts were repeatedly reinfested with ticks. scapularis ticks that fed on raccoons had significantly shorter pre-oviposition periods than did ticks that fed on dogs. Previous studies have documented that host quality does vary. However, host species might also differ substantially in their quality as a host, here defined as the probability that a vector attempting a blood meal from that host successfully feeds and survives. Host species can differ dramatically in their quality as a reservoir, that is, in their probability of infecting a feeding vector with a specific pathogen ( Ostfeld & Keesing 2000 for review Komar et al. For these species, vector survival and abundance might depend most strongly on the community of host species upon which they feed. ![]() However, most vectors of zoonotic pathogens are host- and habitat-generalists, that is, they feed on a variety of host species and occupy different habitat types ( Ostfeld & Keesing 2000 Molyneux 2003). fleas on prairie dogs Gage & Kosoy 2005) or breeding sites (e.g. Alternatively, abundance of vectors that are host- or habitat-specialists can be regulated by the availability of specific hosts (e.g. For example, long-term population dynamics of blacklegged ticks ( Ixodes scapularis) in New York, USA were not associated with temperature (growing degree-days) or precipitation parameters ( Ostfeld et al. 2008), in many other cases climate fails to explain vector abundance or disease incidence ( Reiter 2001 Schulze & Jordan 2005 Ostfeld et al. However, despite some clear cases in which climate regulates vector abundance ( Alto & Juliano 2001 Afrane et al. by altering vegetation type and structure. by desiccation, freezing or overheating, or indirectly, e.g. Climate can regulate the abundance of arthropod vectors directly, e.g. The abundance of vectors can be determined by climate-driven population performance ( Fish 1993 Randolph 1993 Martens et al. Vector abundance is a key determinant of risk of exposure to the pathogens that vectors transmit ( Ginsberg 1993 Antonovics et al. As a consequence, understanding variation in exposure risk to vector-borne diseases, and managing environments to reduce this risk, are important goals. ![]() Vector-borne diseases also inflict heavy tolls on crops, livestock and wildlife ( Daszak et al. Worldwide, more than 1.3 million people die each year of infectious diseases transmitted by a vector, such as a mosquito, sand fly or tick ( World Health Organization 2004). By simulating the removal of hosts from intact communities using empirical models, we show that the loss of biodiversity may exacerbate disease risk by increasing both vector numbers and vector infection rates with a zoonotic pathogen. These results indicate that the abundance of tick vectors can be regulated by the identity of the hosts upon which these vectors feed. Given natural tick burdens we document on these hosts, we show that some hosts can kill thousands of ticks per hectare. opossums, squirrels) that are abundantly parasitized in nature kill 83–96% of the ticks that attempt to attach and feed, while other species are more permissive of tick feeding. By subjecting field-caught hosts to parasitism by larval blacklegged ticks, we found that some host species (e.g. In this study we tested whether blacklegged ticks, the vectors of Lyme disease, granulocytic anaplasmosis and babesiosis can be regulated by the species of vertebrate hosts on which they obligately feed. Vectors of infectious diseases are generally thought to be regulated by abiotic conditions such as climate or the availability of specific hosts or habitats.
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