Travel distance and human movement predict paths of emergence and spatial spread of chikungunya in Thailand.

Human movement contributes to the probability that pathogens will be introduced to new geographic locations. Here we investigate the impact of human movement on the spatial spread of Chikungunya virus (CHIKV) in Southern Thailand during a recent re-emergence. We hypothesised that human movement, population density, the presence of habitat conducive to vectors, rainfall and temperature affect the transmission of CHIKV and the spatiotemporal pattern of cases seen during the emergence. We fit metapopulation transmission models to CHIKV incidence data. The dates at which incidence in each of 151 districts in Southern Thailand exceeded specified thresholds were the target of model fits. We confronted multiple alternative models to determine which factors were most influential in the spatial spread. We considered multiple measures of spatial distance between districts and adjacency networks and also looked for evidence of long-distance translocation (LDT) events. The best fit model included driving-distance between districts, human movement, rubber plantation area and three LDT events. This work has important implications for predicting the spatial spread and targeting resources for control in future CHIKV emergences. Our modelling framework could also be adapted to other disease systems where population mobility may drive the spatial advance of outbreaks.

Identifying transmission routes of Streptococcus pneumoniae and sources of acquisitions in high transmission communities.

Identifying the transmission sources and reservoirs of Streptococcus pneumoniae (SP) is a long-standing question for pneumococcal epidemiology, transmission dynamics, and vaccine policy. Here we use serotype to identify SP transmission and examine acquisitions (in the same household, local community, and county, or of unidentified origin) in a longitudinal cohort of children and adults from the Navajo Nation and the White Mountain Apache American Indian Tribes. We found that adults acquire SP relatively more in the household than other age groups, and children 2-8 years old typically acquire in their own or surrounding communities. Age-specific transmission probability matrices show that transmissions within household were mostly seen from older to younger siblings. Outside the household, children most often transmit to other children in the same age group, showing age-assortative mixing behavior. We find toddlers and older children to be most involved in SP transmission and acquisition, indicating their role as key drivers of SP epidemiology. Although infants have high carriage prevalence, they do not play a central role in transmission of SP compared with toddlers and older children. Our results are relevant to inform alternative pneumococcal conjugate vaccine dosing strategies and analytic efforts to inform optimization of vaccine programs, as well as assessing the transmission dynamics of pathogens transmitted by close contact in general.

Potential for large-bodied zooplankton and dreissenids to alter the productivity and autotrophic structure of lakes.

While limnological studies have emphasized the importance of grazers on algal biomass and primary production in pelagic habitats, few studies have examined their potential role in altering total ecosystem primary production and it's partitioning between pelagic and benthic habitats. We modified an existing ecosystem production model to include biotic feedbacks associated with two groups of large-bodied grazers of phytoplankton (large-bodied zooplankton and dreissenid mussels) and estimated their effects on total ecosystem production (TEP), and the partitioning of TEP between phytoplankton and periphyton (autotrophic structure) across large gradients in lake size and total phosphorus (TP) concentration. Model results indicated that these filter feeders were capable of reducing whole-lake phytoplankton production by 20-70%, and increasing whole-lake benthic production between 0% and 600%. Grazer effects on TEP were constrained by lake size, trophic status, and potential feedbacks between grazing and maximum rates of benthic photosynthesis (BP(MAX)). In small (mean depth Z < 10 m) oligotrophic and mesotrophic (TP < 100 mg P/m2) lakes, both large-bodied zooplankton and dreissenids were capable of increasing the benthic fraction (Bf) by 10-50% of TEP. Small lakes were also the only systems where TEP had the potential to increase in the presence of large-bodied grazers, but such increases only occurred if grazer-induced changes in water clarity, macrophyte coverage, or nutrient availability stimulated specific growth rates of periphyton. In other scenarios, TEP declined by a maximum of 50%. In very large lakes (Z > 100 m), Bf was minor (< 10%) in the presence or absence of grazers, but increases in littoral habitat and the stimulation of benthic production in these ecosystems could be of ecological relevance because littoral zones in large lakes contain a relatively high proportion of within-lake biodiversity and are important for whole-lake food webs.

Post-traumatic stress disorder symptoms after acute lung injury: a 2-year prospective longitudinal study.

BACKGROUND: Survivors of critical illnesses often have clinically significant post-traumatic stress disorder (PTSD) symptoms. This study describes the 2-year prevalence and duration of PTSD symptoms after acute lung injury (ALI), and examines patient baseline and critical illness/intensive care-related risk factors. METHOD: This prospective, longitudinal cohort study recruited patients from 13 intensive care units (ICUs) in four hospitals, with follow-up 3, 6, 12 and 24 months after ALI onset. The outcome of interest was an Impact of Events Scale - Revised (IES-R) mean score ≥1.6 ('PTSD symptoms'). RESULTS: During the 2-year follow-up, 66/186 patients (35%) had PTSD symptoms, with the greatest prevalence by the 3-month follow-up. Fifty-six patients with post-ALI PTSD symptoms survived to the 24-month follow-up, and 35 (62%) of these had PTSD symptoms at the 24-month follow-up; 50% had taken psychiatric medications and 40% had seen a psychiatrist since hospital discharge. Risk/protective factors for PTSD symptoms were pre-ALI depression [hazard odds ratio (OR) 1.96, 95% confidence interval (CI) 1.06-3.64], ICU length of stay (for a doubling of days, OR 1.39, 95% CI 1.06-1.83), proportion of ICU days with sepsis (per decile, OR 1.08, 95% CI 1.00-1.16), high ICU opiate doses (mean morphine equivalent ≥100 mg/day, OR 2.13, 95% CI 1.02-4.42) and proportion of ICU days on opiates (per decile, OR 0.83, 95% CI 0.74-0.94) or corticosteroids (per decile, OR 0.91, 95% CI 0.84-0.99). CONCLUSIONS: PTSD symptoms are common, long-lasting and associated with psychiatric treatment during the first 2 years after ALI. Risk factors include pre-ALI depression, durations of stay and sepsis in the ICU, and administration of high-dose opiates in the ICU. Protective factors include durations of opiate and corticosteroid administration in the ICU.

Histopathologic and bacteriologic evaluations of cellulitis detected in legs and caudal abdominal regions of turkeys.

The objective of this study was to identify the causative agent of cellulitis in turkeys. Eighteen flocks from nine producers were sampled at the local processing plant, and 37 birds with cellulitis on legs or caudal thoracic area were obtained. None of the 37 birds with cellulitis had lesions in other organs. On gross examination, lesions were categorized into two groups: cellulitis with unopened skin lesions (type a) and cellulitis with opened skin lesions (type b). Histopathologically, cellulitis with unopened skin lesions had dermal necrosis with underlying fibrin and inflammatory exudate but cellulitis with open skin lesions had chronic granulomatous/granulation tissue-type reaction associated with foreign material. A complete bacteriologic study was conducted on 25 of 37 birds. Bacteria were isolated from 12 of the 25 birds with cellulitis lesions. No aerobic, microaerophilic, or anaerobic bacteria were isolated from the remaining 13 birds with cellulitis lesions. Escherichia coli was isolated in low numbers in mixed cultures with Proteus mirabilis, Lactobacillus spp., Klebsiella spp., and Staphylococcus spp. in 9 of 12 lesions. The remaining few cases yielded P. mirabilis in pure culture or in mixed culture with Pseudomonas aeruginosa. Types a and b cellulitis lesions in turkeys could be associated with primary contact dermatitis and skin abrasions, respectively. Their occurrence is likely associated with different management practices.