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Susceptible Population (susceptible + population)
Selected AbstractsDecline in hepatitis B infection observed after 11 years of regional vaccination among Danish drug usersJOURNAL OF MEDICAL VIROLOGY, Issue 10 2010B.K. Mössner Abstract The aims of this study were to determine the current prevalence of viral hepatitis and HIV among drug users, and to compare this prevalence with previous findings in the same geographical region. Cross-sectional surveys of drug users attending treatment centers on the island of Funen with approximately 500,000 inhabitants were administered in 1996 and 2007. The 2007 prevalence estimates were: anti-HBc 50.2%, HBsAg 0.9%, anti-HCV 66.8%, HCV-RNA 40%, and anti-HIV 1.1%. The corresponding 1996 prevalence values were: anti-HBc 70% (P,<,0.0001), HBsAg 9.8% (P,<,0.0001), anti-HCV 82.8% (P,<,0.0001), HCV-RNA 56.3% (P,=,0.002), and anti-HIV 1% (P,=,1). The 2007 prevalence of viral hepatitis decreased due to the increasing proportion of non-injectors. Among injectors, the prevalence remained unchanged except for a significant decrease in HBsAg. The 2007 prevalence of ongoing HBV infection among infected (HBsAg/anti-HBc proportion) was the lowest that to our knowledge has been reported among drug-users. Vaccination coverage among susceptible persons tested in 2007 was 24%, compared to 0.7% in 1996. Therefore, despite an unchanged prevalence of anti-HBc among injecting drug users, a highly significant drop in HBsAg prevalence was seen during the last decade. This observation may be linked causally to an increase in hepatitis B vaccination of the susceptible population. Our findings suggest that even incomplete vaccination, without persistent protective anti-HBs levels, may induce an immune memory sufficient to prevent chronic infection upon transmission. J. Med. Virol. 82:1635,1639, 2010. 2010 Wiley-Liss, Inc. [source] Resistance of codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), larvae in Michigan to insecticides with different modes of action and the impact on field residual activityPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 9 2008David Mota-Sanchez Abstract BACKGROUND: The codling moth is one of the principal pests of apple in the world. Resistance monitoring is crucial to the effective management of resistance in codling moth. Three populations of codling moth in neonate larvae were evaluated for resistance to seven insecticides via diet bioassays, and compared with a susceptible population. In addition, apple plots were treated with labeled field rate doses of four insecticides. Treated fruit were exposed to neonate larvae of two populations from commercial orchards. RESULTS: Two populations of codling moth expressed two- and fivefold resistance to azinphos-methyl, seven- and eightfold resistance to phosmet, six- and tenfold resistance to lambda-cyhalothrin, 14- and 16-fold resistance to methoxyfenozide and sixfold resistance to indoxacarb, but no resistance to acetamiprid and spinosad. The impact of the resistance to azinphos-methyl, measured as fruit damage, increased as the insecticide residues aged in the field. In contrast, fruit damage in methoxyfenozide- and lambda-cyhalothrin-treated fruit was observed earlier for resistant codling moth. No differences in efficacy were found for acetamiprid. CONCLUSIONS: Broad-spectrum insecticide resistance was detected for codling moth. Resistance to azinphos-methyl, lambda-cyhalothrin and methoxyfenozide was associated with reduced residual activity in the field. Broad-spectrum resistance presents serious problems for management of the codling moth in Michigan. Copyright © 2008 Society of Chemical Industry [source] Comparison of dose responses and resistance ratios in four populations of the rice stem borer, Chilo suppressalis (Lepidoptera: Pyralidae), to 20 insecticidesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 3 2008Yue Ping He Abstract BACKGROUND: Chemical control is a major strategy for suppressing the rice stem borer, Chilo suppressalis (Walker). Owing to their high toxicity and increasing resistance development in the target insect, many insecticides will be phased out entirely in 2007 in China. Alternatives with relatively low toxicity are urgently needed to replace traditional chemicals for rice stem borer control. In this study, the authors examined four field populations of C. suppressalis for their toxicological responses to more than 20 insecticides, including a few low-toxicity organophosphates and many novel pesticides. Interpopulation resistance levels to 12 conventional insecticides were also compared. RESULTS: Based on LD50 values, the rice stem borer was most sensitive to avermectins and fipronil (LD50 < 1 ng larva,1). The stem borers exhibited the least sensitivity to endosulfan (LD50 > 100 ng larva,1) and monosultap (LD50 > 1000 ng larva,1). Insect growth regulators and chitin synthase inhibitors showed great efficacy against C. suppressalis, especially against populations that had developed resistance to conventional insecticides. Four field populations showed variable tolerance levels to many insecticides. LYG05 was the most susceptible population, only with a low level of resistance to monosultap (RR = 6.6). NC05 and GL05 populations exhibited intermediate tolerance levels with RR values up to 20.4 and 52.8 respectively. RA05 was the most resistant population to many insecticides, with resistance ratios up to 76.2. CONCLUSION: The results from this study provide valuable information for selection and adoption of new alternative insecticides and for resistance management of the rice stem borer. Copyright © 2008 Society of Chemical Industry [source] psbA mutation (Asn266 to Thr) in Senecio vulgaris L. confers resistance to several PS II-inhibiting herbicidesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 9 2006Kee Woong Park Abstract DNA sequence analysis of the psbA gene encoding the D1 protein of photosystem II (PS II), the target site of PS II-inhibiting herbicides, identified a point mutation (Asn266 to Thr) in a bromoxynil-resistant Senecio vulgaris L. population collected from peppermint fields in Oregon. Although this mutation has been previously reported in Synechocystis, this is the first report of this particular point mutation in a higher plant exhibiting resistance to PS II-inhibiting herbicides. The resistant population displayed high-level resistance to bromoxynil and terbacil (R/S ratio 10.1 and 9.3, respectively) and low-level resistance to metribuzin and hexazinone (R/S ratio 4.2 and 2.6, respectively) when compared with the susceptible population. However, the population was not resistant to the triazine herbicides atrazine and simazine or to the urea herbicide diuron. A chlorophyll fluorescence assay confirmed the resistance levels and patterns of cross-resistance of the whole-plant studies. The resistant S. vulgaris plants produced fewer seeds. Differences in cross-resistance patterns to PS II-inhibiting herbicides and the difference in fitness cost could be exploited in a weed management program. Copyright © 2006 Society of Chemical Industry [source] Implication of Ariaal sexual mixing on gonorrheaAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 3 2005C. Connell McCluskey Recent research on sexual mixing in populations of sub-Saharan Africa raises the question as to whether STDs can persist in these populations without the presence of a core group. A mathematical model is constructed for the spread of gonorrhea among the Ariaal population of Northern Kenya. A formula for the basic reproduction number R0 (the expected number of secondary infections caused by a single new infective introduced into a susceptible population) is determined for this population in the absence of a core group. Survey data taken in 2003 on sexual behavior from the Ariaal population are used in the model which is formulated for their age-set system including four subpopulations: single and married, female and male. Parameters derived from the data, and other information from sub-Saharan Africa are used to estimate R0. Results indicate that, even with the elevating effect of the age-set system, the disease should die out since R0 < 1. Thus, the persistence of gonorrhea in the population must be due to factors not included in the model, for example, a core group of commercial sex workers or concurrent partnerships. Am. J. Hum. Biol. 17:293,301, 2005. © 2005 Wiley-Liss, Inc. [source] Australian populations of onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), are resistant to some insecticides used for their controlAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 4 2008Grant A Herron Abstract Onion thrips, Thrips tabaci Lindeman, is a major pest of Australian field onion Allium cepa Linnaeus with their control heavily reliant on a few insecticides. An earlier study after grower complaints of control failures did not detect resistance in three populations. After testing an additional nine populations via a Potter spray tower laboratory bioassay unequally against ,-cypermethrin, diazinon, dimethoate, ,-cyhalothrin, malathion and methidathion, we document resistance in T. tabaci for the first time in Australia. The maximum difference in response (resistance) for each insecticide was detected by dividing the most resistant LC50 response by the least resistant LC50 response. Comparison of the most susceptible to the least susceptible population tested produced ,-cypermethrin and ,-cyhalothrin resistance at 164- and 606-fold, respectively. Diazinon and dimethoate resistance was also detected at 27-fold and 5.2-fold respectively although omethoate, malathion and methidathion resistance were not detected. [source] Thromboembolism in children with acute lymphoblastic leukaemia treated on Dana-Farber Cancer Institute protocols: effect of age and risk stratification of diseaseBRITISH JOURNAL OF HAEMATOLOGY, Issue 6 2005Uma H. Athale Summary Children with acute lymphoblastic leukaemia (ALL) are at increased risk for thromboembolism (TE). Identification of a susceptible population is crucial for effective thromboprophylaxis. However, the risk factors for ALL-associated TE are unclear. Concomitant asparaginase (ASP) and steroid therapy has been shown to increase the incidence of TE. Dana-Farber Cancer Institute (DFCI)-ALL protocols use a combination of ASP and steroids during the postinduction intensification phase when high-risk (HR) patients receive thrice the steroid-dose given to standard-risk (SR) patients. We studied prospectively assembled cohorts of children treated on two consecutive DFCI-ALL protocols to define the risk factors for symptomatic TE. Ten (11%) of 91 patients developed symptomatic TE; eight (seven HR) during intensification. Seven (44%) of 16 older patients (,10 years) compared with three of 75 (4%) younger patients developed TE (P < 0·0001). Nine of 35 (26%) HR and one of 56 (2%) SR patients developed TE (P = 0·0006). Gender, ALL-immunophenotype, steroid-type or ASP dosing schedule did not alter the risk but older age and HR-disease were factors predisposing to TE associated with DFCI-ALL protocols. Age-related risk may partly reflect the effect of ALL-risk stratification. Higher dose steroids combined with ASP may lead to an increased risk of TE in HR patients. [source] Time-distributed effect of exposure and infectious outbreaksENVIRONMETRICS, Issue 3 2009Elena N. Naumova Abstract Extreme weather affects the timing and intensity of infectious outbreaks, the resurgence and redistribution of infections, and it causes disturbances in human-environment interactions. Environmental stressors with high thermoregulatory demands require susceptible populations to undergo physiological adaptive processes potentially compromising immune function and increasing susceptibility to infection. In assessing associations between environmental exposures and infectious diseases, failure to account for a latent period between time of exposure and time of disease manifestation may lead to severe underestimation of the effects. In a population, health effects of an episode of exposure are distributed over a range of time lags. To consider such time-distributed lags is a challenging task given that the length of a latent period varies from hours to months and depends on the type of pathogen, individual susceptibility to the pathogen, dose of exposure, route of transmission, and many other factors. The two main objectives of this communication are to introduce an approach to modeling time-distributed effect of exposures to infection cases and to demonstrate this approach in an analysis of the association between high ambient temperature and daily incidence of enterically transmitted infections. The study is supplemented with extensive simulations to examine model sensitivity to response magnitude, exposure frequency, and extent of latent period. Copyright © 2008 John Wiley & Sons, Ltd. [source] A Microsatellite DNA Marker Developed for Identifying Disease-resistant Population of Giant Black Tiger Shrimp, Penaeus monodonJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 2 2009Kuntal Mukherjee White spot disease caused by white spot syndrome virus (WSSV) poses major problems that result in huge economic losses each year in shrimp aquaculture throughout the world. In the present study, microsatellite-based DNA fingerprints have been compared between naturally occurring WSSV disease-resistant and susceptible populations of giant black tiger shrimp, Penaeus monodon, to find DNA markers. For the first time, we report here a microsatellite locus, which, after amplification by polymerase chain reaction, provides a highly statistically significant DNA fingerprint of 71 bp, only in disease susceptible populations but not in disease-resistant shrimp populations, whereas a 317 bp band is common in both. The absence of the former DNA marker will be very useful to identify disease-resistant broodstock of P. monodon for marker-assisted selection in breeding programs to generate disease-free shrimps (P. monodon) in the aquaculture industry. [source] Acute lower respiratory tract infections by human metapneumovirus in children in Southwest China: A 2-year studyPEDIATRIC PULMONOLOGY, Issue 8 2010Xin Chen MD Abstract Human metapneumovirus (hMPV) has been reported to cause both upper and lower respiratory tract diseases in susceptible populations, particularly in children and the elderly. In this study, we describe a hospital-based epidemiological study of hMPV in patients presenting to a children's hospital and show the demographic and clinical characteristics associated with hMPV infection in China, retrospectively. Specimens were collected over a 2-year period from children hospitalized with acute lower respiratory tract infections (ALRTI) and analyzed for the presence of hMPV using real-time RT-PCR assays. The presence of hMPV was detected in 227 (25.9%) of the 878 children studied and may circulate year-round in the area, peaking during the winter,spring season. Younger children (aged less than 6 months) had the highest positive rate. Infections by hMPV showed similar epidemiology and clinical manifestations as for respiratory syncytial virus (RSV) and were found in high co-infections with RSV. Subgroup A2 hMPV was the most predominant genotype identified during the study period. This study indicates that hMPV is one of the major respiratory pathogens found in children in southwest China and vaccine development should be under consideration. Pediatr. Pulmonol. 2010; 45:824,831. © 2010 Wiley-Liss, Inc. [source] Modelling binary mixtures of herbicides in populations resistant to one of the components: evaluation for resistance managementPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 2 2009Bertrand Jacquemin Abstract BACKGROUND: Herbicide mixtures are commonly proposed to delay the selection of herbicide resistance in susceptible populations (called the SM strategy). However, in practice, herbicide mixtures are often used when resistance to one of the two active ingredients has already been detected in the targeted population (called the RM strategy). It is doubtful whether such a practice can select against resistance, as the corresponding selection pressure is still exerted. As a consequence, the effect of mixtures on the evolution of an already detected resistance to one of the herbicides in the combination remains largely unexplored. In the present work, a simple model was developed to explore further the necessary and sufficient conditions under which a binary RM strategy might stabilise or even reduce resistance frequency. RESULTS: Covering the hypothetical largest range of parameters, 39% of 9000 random simulations attest that the RM strategy might theoretically reduce resistance frequency. When strong enough, high genetic cost of resistance, negative cross-resistance between the herbicides associated in the mixture and reduced selection differential between resistant and susceptible plants can counterbalance the resistance advantage to one of the two applied herbicides. However, the required conditions for an RM strategy to ensure resistance containment in natural conditions seldom overlap with experimental parameter estimates given in the literature. CONCLUSION: It is concluded that the sufficient conditions for an RM strategy to be effective would rarely be encountered. As a consequence, the strategy of formulating mixtures with herbicides for which resistance has already been detected should be avoided. Copyright © 2008 Society of Chemical Industry [source] Differential response of Amaranthus tuberculatus (Moq ex DC) JD Sauer to glyphosatePEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 10 2005Ian A Zelaya Abstract Midwest USA farmers have reported inconsistent control of Amaranthus tuberculatus (= rudis) (Moq ex DC) JD Sauer by glyphosate in glyphosate-resistant crops. The potential of selection for decreased A tuberculatus sensitivity to glyphosate was therefore investigated in a reportedly resistant Everly, IA population (P0,EV). Evaluation of six A tuberculatus populations from the Midwest USA estimated a seedling baseline sensitivity of 2.15 mM glyphosate. Based on these results, three generations of divergent recurrent selection were implemented on P0,EV to isolate resistant and susceptible populations. A seedling assay was developed to screen large amounts of seeds and thus expedite the selection process. Whole-plant and seedling rate responses of P0,EV and a known pristine A tuberculatus population from Paint Creek, OH (P0,WT) identified no significant difference in response to glyphosate; however, greater phenotypic variance was ostensibly evident in P0,EV. The first recurrent generation selected for resistance at 3.2 mM glyphosate (RS1,R) had a 5.9- and 1.7-fold resistance increase at the seedling and whole-plant levels, respectively, compared with the susceptible generation selected at 32 µM glyphosate. After three cycles of recurrent selection, 14.6-fold difference in resistance at the seedling level and 3.1-fold difference at the whole-plant level were observed when comparing the populations selected for resistance (RS3,R) and susceptibility (RS3,S). Overall, recurrent selection increased the frequency of resistant individuals and decreased the variability to glyphosate at the population level. Nevertheless, variability for glyphosate resistance was still evident in RS3,R. Results herein suggested that A tuberculatus is inherently variable to glyphosate and that selection decreased the sensitivity to glyphosate. We purport that evolved glyphosate resistance in A tuberculatus may require multiple cycles of selection under field conditions. Historic estimated use of glyphosate alludes to the evolution of tolerant weed populations. Copyright © 2005 Society of Chemical Industry [source] | |||||||||||||