Publications by authors named "Christine B Graham"

Lyme disease is the most common vector-borne disease in the United States. While Lyme disease vectors are widespread, high incidence states are concentrated in the Northeast, North Central and Mid-Atlantic regions. Mapping the distribution of Lyme disease spirochetes in ticks may aid in providing data-driven explanations of epidemiological trends and recommendations for targeting prevention strategies to communities at risk.

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We collected questing Haemaphysalis longicornis ticks from southeastern counties of Pennsylvania, USA. Of 263 ticks tested by PCR for pathogens, 1 adult female was positive for Borrelia burgdorferi sensu stricto, yielding a 0.4% infection rate.

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As the geographic distributions of medically important ticks and tick-borne pathogens continue to expand in the United States, the burden of tick-borne diseases continues to increase along with a growing risk of coinfections. Coinfection with multiple tick-borne pathogens may amplify severity of disease and complicate diagnosis and treatment. By testing 13,400 Ixodes ticks from 17 US states spanning five geographical regions for etiological agents of Lyme disease (Borrelia burgdorferi sensu stricto [s.

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Tickborne diseases are rare in Washington, USA, and the ecology of these pathogens is poorly understood. We integrated surveillance data from humans and ticks to better describe their epidemiology and ecology. During 2011-2016, a total of 202 tickborne disease cases were reported in Washington residents.

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In the north-central United States, the blacklegged tick (Ixodes scapularis) is currently known to vector seven human pathogens. These include five bacteria (Borrelia burgdorferi sensu stricto, Borrelia mayonii, Borrelia miyamotoi, Anaplasma phagocytophilum, Ehrlichia muris eauclairensis), one protozoan (Babesia microti) and one virus (Powassan). We sought to assess the prevalence and distribution of these pathogens in host-seeking nymphs collected throughout Minnesota, a state on the northwestern edge of the tick's expanding range, where reported cases of I.

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Borrelia miyamotoi is an increasingly recognized human pathogen transmitted by Ixodes ticks in the Northern Hemisphere. In North America, infection prevalences of B. miyamotoi are characteristically low (<10%) in Ixodes scapularis (Say; Acari: Ixodidae) and Ixodes pacificus (Cooley & Kohls; Acari: Ixodidae), both of which readily bite humans.

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The incidence and geographic range of tick-borne illness associated with Ixodes scapularis and Ixodes pacificus have dramatically increased in recent decades. Anaplasmosis, babesiosis, and Borrelia spirochete infections, including Lyme borreliosis, account for tens of thousands of reported cases of tick-borne disease every year. Assays that reliably detect pathogens in ticks allow investigators and public health agencies to estimate the geographic distribution of human pathogens, assess geographic variation in their prevalence, and evaluate the effectiveness of prevention strategies.

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Article Synopsis
  • The distribution of the I. scapularis tick, which spreads Lyme disease, has increased in the north-central U.S. over the last 20 years, correlating with more human cases of the disease.
  • Researchers measured tick densities in various land use types in Washington County, Minnesota, aiming to identify factors influencing these densities and assess the prevalence of Lyme disease pathogens in the ticks.
  • The study found that ticks were most abundant in ecotonal areas between forests and lawns, with higher densities linked to residences with more forest cover and deer activity, and detected multiple pathogens, including the Lyme disease-causing bacterium.
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Borrelia mayonii is a newly described member of the Borrelia burgdorferi sensu lato complex that is vectored by the black-legged tick (Ixodes scapularis Say) and a cause of Lyme disease in Minnesota and Wisconsin. Vertebrate reservoir hosts involved in the enzootic maintenance of B. mayonii have not yet been identified.

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Tick-borne pathogens transmitted by Ixodes scapularis Say (Acari: Ixodidae), also known as the deer tick or blacklegged tick, are increasing in incidence and geographic distribution in the United States. We examined the risk of tick-borne disease exposure in 9 national parks across six Northeastern and Mid-Atlantic States and the District of Columbia in 2014 and 2015. To assess the recreational risk to park visitors, we sampled for ticks along frequently used trails and calculated the density of I.

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Borrelia miyamotoi is an emerging, tick-borne human pathogen. In North America, it is primarily associated with Ixodes scapularis and Ixodes pacificus, two species known to bite humans. Here we describe the development and evaluation of a pair of real-time TaqMan PCR assays designed to detect B.

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Article Synopsis
  • Unblocked fleas can transmit Yersinia pestis, the plague-causing bacterium, shortly after getting an infectious blood meal.
  • Researchers have focused on early-phase transmission efficiency in various fleas infected with highly bacteremic blood (≥10 cfu/ml).
  • This study specifically looks at Oropsylla montana fleas to find the minimum bacteremia needed for them to acquire and transmit Y. pestis, discovering that they can get infected from lower concentrations but only transmit when fed highly bacteremic blood.
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Rodent fleas from northwestern Chihuahua, Mexico, were analyzed for the presence of Bartonella and Yersinia pestis. In total, 760 fleas belonging to 10 species were tested with multiplex polymerase chain reaction analysis targeting the gltA (338-bp) and pla genes (478-bp) of Bartonella and Y. pestis, respectively.

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Pulex irritans L. is a cosmopolitan flea species that infests a wide variety of hosts. In North America it generally parasitizes large wild mammals, but in the Pacific Northwest an association has emerged between P.

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Article Synopsis
  • Plague, caused by the bacterium Yersinia pestis, spreads rapidly through fleas and has quiet periods where it persists, but little is known about its survival during these times.
  • It is theorized that Y. pestis survives in cycles involving fleas and resistant hosts, where susceptible hosts die, but resistant ones survive and maintain flea infections.
  • Recent studies show that fleas retain high infection rates and bacterial loads after feeding on both immunized and naive mice, supporting the idea that Y. pestis can persist even when hosts develop immunity.
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Plague, caused by Yersinia pestis, is characterized by quiescent periods punctuated by rapidly spreading epizootics. The classical 'blocked flea' paradigm, by which a blockage forms in the flea's proventriculus on average 1-2 weeks post-infection (p.i.

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Article Synopsis
  • Plague is a deadly disease caused by bacteria and mainly spread by fleas from rodents.
  • In a study in Uganda, researchers compared villages with and without human plague cases, finding higher rat-human contact and flea infestations in villages with cases.
  • Risk factors for plague included sleeping on straw mats, storing food and garbage in or near huts, and allowing dogs in sleeping areas, whereas control villages showed better practices like maintaining roofs and growing certain crops.
  • The study suggests that improving local hygiene practices could help prevent plague outbreaks.
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Programs that aim to control vector-borne zoonotic diseases require information on zoonotic hosts and on the feeding behavior of bridging vectors that are capable of transmitting pathogens from those hosts to humans. Here we describe an assay developed to identify bloodmeals in field-collected cat fleas (Ctenocephalides felis Bouché) to assess this species' potential role as a Yersinia pestis bridging vector in a plague-endemic region of Uganda. Our assay uses a single primer set and SYBR Green I-based real-time polymerase chain reaction to amplify a segment of the 12S mitochondrial ribosomal RNA gene for identification by sequencing.

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The cat flea, Ctenocephalides felis, is an inefficient vector of the plague bacterium (Yersinia pestis) and is the predominant off-host flea species in human habitations in the West Nile region, an established plague focus in northwest Uganda. To determine if C. felis might serve as a Y.

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Plague, an often-fatal zoonotic disease caused by Yersinia pestis, is characterized by epizootic and quiescent periods. How Y. pestis is maintained during inter-epizootic periods is poorly understood, but soil has been implicated as a potential reservoir.

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Article Synopsis
  • The study investigates the effectiveness of different methods for collecting host-seeking fleas, which are important for understanding the risk of flea-borne diseases like plague.
  • In laboratory tests, active collection methods using cotton socks were more efficient at gathering fleas compared to passive light traps, specifically with variations like blinking lights or carbon dioxide.
  • Field studies in northwest Uganda showed that Kilonzo traps with flashlights were effective in collecting fleas and were particularly successful in human habitats for capturing the species most commonly associated with humans, Ctenocephalides felis.
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Background: Traditionally, efficient flea-borne transmission of Yersinia pestis, the causative agent of plague, was thought to be dependent on a process referred to as blockage in which biofilm-mediated growth of the bacteria physically blocks the flea gut, leading to the regurgitation of contaminated blood into the host. This process was previously shown to be temperature-regulated, with blockage failing at temperatures approaching 30°C; however, the abilities of fleas to transmit infections at different temperatures had not been adequately assessed. We infected colony-reared fleas of Xenopsylla cheopis with a wild type strain of Y.

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Sharp declines in human and animal cases of plague, caused by the bacterium Yersinia pestis (Yersin), have been observed when outbreaks coincide with hot weather. Failure of biofilm production, or blockage, to occur in the flea, as temperatures reach 30 degrees C has been suggested as an explanation for these declines. Recent work demonstrating efficient flea transmission during the first few days after fleas have taken an infectious blood meal, in the absence of blockage (e.

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