Last data update: May 06, 2024. (Total: 46732 publications since 2009)
Records 1-9 (of 9 Records) |
Query Trace: Loftis AD[original query] |
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Duration of tick attachment necessary for transmission of Anaplasma phagocytophilum by Ixodes scapularis (Acari: Ixodidae) nymphs
Levin ML , Troughton DR , Loftis AD . Ticks Tick Borne Dis 2021 12 (6) 101819 This study assessed the duration of tick attachment necessary for a successful transmission of Anaplasma phagocytophilum by an infected I. scapularis nymph. Individual nymphs were placed upon BALB/c mice and allowed to feed for predetermined time intervals of 4 to 72 h. Ticks removed from mice at predetermined intervals were tested by PCR for verification of infection and evaluation of the bacterial load. The success of pathogen transmission to mice was assessed by blood-PCR at 7, 14 and 21 days postinfestation, and IFA at 21 days postinfestation. Anaplasma phagocytophilum infection was documented in 10-30 % of mice, from which ticks were removed within the first 20 h of feeding. However, transmission success was ≥70% if ticks remained attached for 36 h or longer. Notably, none of the PCR-positive mice that were exposed to infected ticks for 4 to 8 h and only half of PCR-positive mice exposed for 24 h developed antibodies within 3 weeks postinfestation. On the other hand, all mice with detectable bacteremia after being infested for 36 h seroconverted. This suggests that although some of the ticks removed prior to 24 h of attachment succeed in injecting a small amount of A. phagocytophilum, this amount is insufficient for stimulating humoral immunity and perhaps for establishing disseminated infection in BALB/c mice. Although A. phagocytophilum may be present in salivary glands of unfed I. scapularis nymphs, the amount of A. phagocytophilum initially contained in saliva appears insufficient to cause sustainable infection in a host. Replication and, maybe, reactivation of the agent for 12-24 h in a feeding tick is required before a mouse can be consistently infected. |
Rickettsia parkeri Rickettsiosis, Arizona, USA
Herrick KL , Pena SA , Yaglom HD , Layton BJ , Moors A , Loftis AD , Condit ME , Singleton J , Kato CY , Denison AM , Ng D , Mertins JW , Paddock CD . Emerg Infect Dis 2016 22 (5) 780-5 In the United States, all previously reported cases of Rickettsia parkeri rickettsiosis have been linked to transmission by the Gulf Coast tick (Amblyomma maculatum). Here we describe 1 confirmed and 1 probable case of R. parkeri rickettsiosis acquired in a mountainous region of southern Arizona, well beyond the recognized geographic range of A. maculatum ticks. The likely vector for these 2 infections was identified as the Amblyomma triste tick, a Neotropical species only recently recognized in the United States. Identification of R. parkeri rickettsiosis in southern Arizona demonstrates a need for local ecologic and epidemiologic assessments to better understand geographic distribution and define public health risk. Education and outreach aimed at persons recreating or working in this region of southern Arizona would improve awareness and promote prevention of tickborne rickettsioses. |
Panola Mountain Ehrlichia in Amblyomma maculatum from the United States and Amblyomma variegatum (Acari: Ixodidae) from the Caribbean and Africa
Loftis AD , Kelly PJ , Paddock CD , Blount K , Johnson JW , Gleim ER , Yabsley MJ , Levin ML , Beati L . J Med Entomol 2016 53 (3) 696-698 Panola Mountain Ehrlichia (PME) has been suggested as an emerging pathogen of humans and dogs. Domestic goats and white-tailed deer (Odocoileus virginianus) are also susceptible and likely serve as reservoirs. Experimentally, both the lone star tick (Amblyomma americanum (L.)) and the Gulf Coast tick (Amblyomma maculatum Koch) can transmit PME among deer and goats. In the current study, we detected PME in adult wild-caught A. maculatum from the United States and Amblyomma variegatum (F.) from the Caribbean and Africa. This significantly expands the range, potential tick vectors, and risk for exposure to PME. |
Detection of bacterial agents in Amblyomma americanum (Acari: Ixodidae) from Georgia, USA, and the use of a multiplex assay to differentiate Ehrlichia chaffeensis and Ehrlichia ewingii
Killmaster LF , Loftis AD , Zemtsova GE , Levin ML . J Med Entomol 2014 51 (4) 868-872 Amblyomma americanum, the lone star tick, is the most common and most aggressive human biting tick in the Southeastern United States. It is known to transmit the agents of human ehrlichioses, Ehrlichia chaffeensis and Ehrlichia ewingii. In addition, it carries agents of unspecified pathogenicity to humans, including Rickettsia amblyommii, Borrelia lonestari, and the newly emerging Panola Mountain Ehrlichia (PME). Surveillance of these ticks for recognized or emerging pathogens is necessary for assessing the risk of human infection. From 2005 to 2009, we surveyed A. americanum ticks from four locations in the state of Georgia. Ticks (1,183 adults, 2,954 nymphs, and 99 larval batches) were tested using a multiplex real-time polymerase chain reaction (PCR) assay designed to detect and discriminate DNA from Rickettsia spp., E. chaffeensis, and E. ewingii. This assay was capable of detecting as few as 10 gene copies of the aforementioned agents. Ticks were also tested for PME and B. lonestari by nested PCR. The prevalence of infection ranged from 0 to 2.5% for E. chaffeensis, 0 to 3.9% for E. ewingii, 0 to 2.2% for PME, 17 to 83.1% for R. amblyommii, and 0 to 3.1% for B. lonestari. There were 46 (4.1%) individual adults positive for two agents, and two females that were each positive for three agents. Two larval batches were positive for both B. lonestari and R. amblyommii, indicating the potential for transovarial transmission of both agents from a single female. Although infrequent in occurrence, the dynamics of coinfections in individual ticks should be explored further, given the potential implications for differential diagnosis and severity of human illness. |
Coxiella burnetii, the agent of Q fever, in domestic sheep flocks from Wyoming, United States
Loftis AD , Reeves WK , Miller MM , Massung RF . Vector Borne Zoonotic Dis 2012 12 (3) 189-91 Coxiella burnetii, the agent of Q fever, is an intracellular bacterial pathogen. It has a nearly cosmopolitan distribution. We conducted a serological survey of domestic sheep herds for infections with C. burnetii in Wyoming following reports of abortion and open ewes. Based on the serologic evidence, there was no link between reproductive problems and exposure to C. burnetii. However, the overall prevalence of C. burnetii in WY sheep was 7%, which indicates that the agent is present in the environment and could pose a threat to public health. |
Detection of Coxiella burnetii in commercially available raw milk from the United States
Loftis AD , Priestley RA , Massung RF . Foodborne Pathog Dis 2010 7 (12) 1453-6 Unpasteurized (raw) milk can be purchased in 39 U.S. states, with direct consumer purchase for human consumption permitted in 29 of those 39 states. Raw milk (n=21; cow, 14; goat, 7) was purchased in 12 states, and Coxiella burnetii, the agent of Q fever, was detected in 9 of 21 (42.9%) samples tested by polymerase chain reaction. Viability of the pathogen was demonstrated by isolation of the agent in tissue culture. The demonstration of viable C. burnetii in commercially available raw milk poses a potential public health risk. |
Presence of Coxiella burnetii DNA in the environment of the United States (2006-2008)
Kersh GJ , Wolfe TM , Fitzpatrick KA , Candee AJ , Oliver LD , Patterson NE , Self JS , Priestley RA , Loftis AD , Massung RF . Appl Environ Microbiol 2010 76 (13) 4469-75 Coxiella burnetii is an obligate intracellular bacterium that causes the zoonotic disease Q fever. Because C. burnetii is highly infectious, can survive under a variety of environmental conditions, and has been weaponized in the past, it is classified as a select agent and is considered a potential bioweapon. The agent is known to be present in domestic livestock and in wild animal populations, but the background levels of C. burnetii in the environment have not been reported. To better understand the amount of C. burnetii present in the environment of the U.S., greater than 1,600 environmental samples were collected from 6 geographically diverse U.S. states in the years 2006-2008. DNA was purified from these samples, and the presence of C. burnetii DNA was evaluated by quantitative PCR of the IS1111 repetitive element. Overall, 23.8% of the samples were positive for C. burnetii DNA. The prevalence in the different states ranged from 6 to 44 percent. C. burnetii DNA was detected in locations with livestock and also in locations with primarily human activity (post offices, stores, schools, etc.). This study demonstrates that C. burnetii is fairly common in the environment in the U.S., and any analysis of C. burnetii after a suspected intentional release should be interpreted in light of these background levels. It also suggests that human exposure to C. burnetii may be more common than what is suggested by the number of reported cases of Q fever. |
Isolation of Rickettsia parkeri and identification of a novel spotted fever group Rickettsia sp. from gulf coast ticks (Amblyomma maculatum) in the United States
Paddock CD , Fournier PE , Sumner JW , Goddard J , Elshenawy Y , Metcalfe MG , Loftis AD , Varela-Stokes A . Appl Environ Microbiol 2010 76 (9) 2689-96 Until recently, Amblyomma maculatum, (the Gulf Coast tick), has garnered little attention relative to other species of human-biting ticks in the United States. A. maculatum is now recognized as the principal vector of Rickettsia parkeri, a pathogenic spotted fever group rickettsia (SFGR) that causes an eschar-associated illness in humans that resembles Rocky Mountain spotted fever. A novel SFGR, distinct from other recognized Rickettsia spp., has also been detected recently in A. maculatum specimens collected from several regions of the southeastern United States. In this study, 198 questing adult Gulf Coast ticks were collected from 4 locations in Florida and Mississippi; 28% were infected with R. parkeri and 3% with a novel SFGR. Seventeen isolates of R. parkeri were cultivated in Vero E6 cells from individual specimens of A. maculatum; however, all attempts to isolate the novel SFGR were unsuccessful. Partial genetic characterization of the novel SFGR revealed identity with several recently described, incompletely characterized, and non-cultivated SFGR including Candidatus 'Rickettsia andeanae' and Rickettsia sp. 'Argentina', detected in several species of Neotropical ticks from Argentina and Peru. These findings suggest that each of these 'novel' rickettsiae represent the same species. Our study expands considerably the number of low-passage, A. maculatum-derived isolates of R. parkeri, and characterizes a second and sympatrically distributed Rickettsia sp. found in Gulf Coast ticks. |
Seroprevalence of Q fever in the United States, 2003-2004
Anderson AD , Kruszon-Moran D , Loftis AD , McQuillan G , Nicholson WL , Priestley RA , Candee AJ , Patterson NE , Massung RF . Am J Trop Med Hyg 2009 81 (4) 691-4 We performed serum testing for IgG antibodies against Coxiella burnetii (phase I and phase II) and analyzed questionnaire data from 4,437 adults > or = 20 years of age who participated in the National Health and Nutrition Examination Survey 2003-2004 survey cycle. National Q fever seroprevalence was determined by enzyme-linked immunosorbent assay and confirmed by using immunofluorescent antibody testing. Overall seroprevalence for Coxiella burnetii was 3.1% (95% confidence interval [CI] = 2.1-4.3%) among 4,437 adults > or = 20 years of age. Coxiella burnetii age-adjusted antibody prevalence was higher for men than for women (3.8%, 95% CI = 2.7-5.2% versus 2.5%, 95% CI = 1.5-3.7%, respectively, P < 0.05). Mexican Americans had a significantly higher antibody prevalence (7.4%, 95% CI = 6.6-8.3%) than either non-Hispanic whites (2.8%, 95% CI = 1.7-4.3%) or non-Hispanic blacks (1.3%, 95% CI = 0.6-2.5%) (P < 0.001). Multivariate analysis showed that the risk for Q fever antibody positivity increased with age and was higher among persons who were foreign-born, male, and living in poverty. These findings indicate that the national seroprevalence of Q fever in the United States is higher than expected on the basis of case numbers reported to the Centers for Disease Control and Prevention from state health departments. Potential differences in risk for exposure by race/ethnicity warrant further study. |
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