1. Vector Borne Zoonotic Dis. 2019 Jan 8. doi: 10.1089/vbz.2018.2339. [Epub ahead of
The following study investigates louse parasitism of black-tailed prairie dogs (Cynomys ludovicianus (Ord, Rodentia: Sciuridae)) on 20 plots at 13 colonies in the short-grass prairie of New Mexico, USA, June-August, 2011-2012. Among 124 lice collected from 537 prairie dogs during 1,207 sampling events in which anesthetized animals were combed for ectoparasites, all of the lice were identified as Linognathoides cynomyis (Kim, Phthiraptera: Polyplacidae). Data were analyzed under an information-theoretic approach to identify factors predicting louse parasitism. Lice were most prevalent on plots with high densities of prairie dogs. At the scale of hosts, lice were most abundant on prairie dogs in poor body condition (with low mass:foot ratios) and prairie dogs harboring large numbers of fleas (Siphonaptera, mostly Oropsylla hirsuta (Baker, Siphonaptera: Ceratophyllidae) and Pulex simulans (Baker,Siphonaptera: Pulicidae)). Lice have been implicated as supplemental vectors of the primarily flea-borne bacterium Yersinia pestis (Yersin, Enterobacteriales: Yersiniaceae), a re-emerging pathogen that causes sylvatic plague in prairie dog populations. Coparasitism by lice and fleas, as found herein, might enhance plague transmission. L. cynomyis deserves attention in this context.
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Geneticists are a step closer to understanding how plague evolved into one of the great scourges of human history. Yersinia pestis, the bacterium that causes bubonic plague, spreads through the bites of infected fleas. In the flea’s gut, plague bacteria multiply until a mass of bacteria blocks the passage to the flea’s stomach. The starving flea bites a host and feeds frantically, but since it can’t swallow its meal, it ends up regurgitating blood and bacteria back into its prey’s bloodstream, spreading the disease to a new host.
Read more: Plague
Oral vaccination is an emerging management strategy to reduce the prevalence of high impact infectious diseases within wild animal populations. Plague is a flea-borne zoonosis of rodents that often decimates prairie dog (Cynomys spp.) colonies in the western USA. Recently, an oral sylvatic plague vaccine (SPV) was developed to protect prairie dogs from plague and aid recovery of the endangered black-footed ferret (Mustela nigripes). Although oral vaccination programs are targeted toward specific species, field distribution of vaccine-laden baits can result in vaccine uptake by non-target animals and unintended indirect effects. We assessed the impact of SPV on non-target rodents at paired vaccine and placebo-treated prairie dog colonies in four US states from 2013 to 2015. Bait consumption by non-target rodents was high (70.8%, n = 3113), but anti-plague antibody development on vaccine plots was low (23.7%, n = 266). In addition, no significant differences were noted in combined deer mice (Peromyscus maniculatus) and western harvest mouse (Reithrodontomys megalotis) abundance or community evenness and richness of non-target rodents between vaccine-treated and placebo plots. In our 3-year field study, we could not detect a significant positive or negative effect of SPV application on non-target rodents.
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Sylvatic plague poses a substantial risk to black-tailed prairie dogs ( Cynomys ludovicianus) and their obligate predator, the black-footed ferret ( Mustela nigripes). The effects of plague on prairie dogs and ferrets are mitigated using a deltamethrin pulicide dust that reduces the spread of plague by killing fleas, the vector for the plague bacterium. In portions of Conata Basin, Buffalo Gap National Grasslands, and Badlands National Park, South Dakota, 0.05% deltamethrin has been infused into prairie dog burrows on an annual basis since 2005. We aimed to determine if fleas ( Oropsylla hirsuta) in portions of the Conata Basin and Badlands National Park have evolved resistance to deltamethrin. We assessed flea prevalence, obtained by combing prairie dogs for fleas, as an indirect measure of resistance. Dusting was ineffective in two colonies treated with deltamethrin for >8 yr; flea prevalence rebounded within 1 mo of dusting. We used a bioassay that exposed fleas to deltamethrin to directly evaluate resistance. Fleas from colonies with >8 yr of exposure to deltamethrin exhibited survival rates that were 15% to 83% higher than fleas from sites that had never been dusted. All fleas were paralyzed or dead after 55 min. After removal from deltamethrin, 30% of fleas from the dusted colonies recovered, compared with 1% of fleas from the not-dusted sites. Thus, deltamethrin paralyzed fleas from colonies with long-term exposure to deltamethrin, but a substantial number of those fleas was resistant and recovered. Flea collections from live-trapped prairie dogs in Thunder Basin National Grasslands, Wyoming suggest that, in some cases, fleas might begin to develop a moderate level of resistance to deltamethrin after 5-6 yr of annual treatments. Restoration of black-footed ferrets and prairie dogs will rely on an adaptive, integrative approach to plague management, for instance involving the use of vaccines and rotating applications of insecticidal products with different active ingredients.
Read more: PubMed