Disease ecology, health and the environment: a framework to account for ecological and socio-economic drivers in the control of neglected tropical diseases.

Reducing the burden of neglected tropical diseases (NTDs) is one of the key strategic targets advanced by the Sustainable Development Goals. Despite the unprecedented effort deployed for NTD elimination in the past decade, their control, mainly through drug administration, remains particularly challenging: persistent poverty and repeated exposure to pathogens embedded in the environment limit the efficacy of strategies focused exclusively on human treatment or medical care. Here, we present a simple modelling framework to illustrate the relative role of ecological and socio-economic drivers of environmentally transmitted parasites and pathogens. Through the analysis of system dynamics, we show that periodic drug treatments that lead to the elimination of directly transmitted diseases may fail to do so in the case of human pathogens with an environmental reservoir. Control of environmentally transmitted diseases can be more effective when human treatment is complemented with interventions targeting the environmental reservoir of the pathogen. We present mechanisms through which the environment can influence the dynamics of poverty via disease feedbacks. For illustration, we present the case studies of Buruli ulcer and schistosomiasis, two devastating waterborne NTDs for which control is particularly challenging.This article is part of the themed issue 'Conservation, biodiversity and infectious disease: scientific evidence and policy implications'.

Cost-effectiveness of improvements in diagnosis and treatment accessibility for tuberculosis control in India.

SETTING: Inaccurate diagnosis and inaccessibility of care undercut the effectiveness of high-quality anti-tuberculosis treatment and select for resistance. Rapid diagnostic systems, such as Xpert(®) MTB/RIF for tuberculosis (TB) diagnosis and drug susceptibility testing (DST), and programs that provide high-quality DOTS anti-tuberculosis treatment to patients in the unregulated private sector (public-private mix [PPM]), may help address these challenges, albeit at increased cost. OBJECTIVE/DESIGN: We extended a microsimulation model of TB in India calibrated to demographic, epidemiologic, and care trends to evaluate 1) replacing DST with Xpert; 2) replacing microscopy and culture with Xpert to diagnose multidrug-resistant TB (MDR-TB) and non-MDR-TB; 3) implementing nationwide PPM; and combinations of (3) with (1) or (2). RESULTS: PPM (assuming costs of $38/person) and Xpert improved health and increase costs relative to the status quo. PPM alone or with Xpert cost <1 gross domestic product/capita per quality-adjusted life-year gained relative to the next best intervention, and dominated Xpert interventions excluding PPM. CONCLUSIONS: While both PPM and Xpert are promising tools for combatting TB in India, PPM should be prioritized over Xpert, as private sector engagement is more cost-effective than Xpert alone and, if sufficient resources are available, would substantially increase the value of Xpert if both interventions are implemented together.

Assessing effectiveness and cost-effectiveness of concurrency reduction for HIV prevention.

We estimated the effectiveness and cost-effectiveness of changes in concurrent sexual partnerships in reducing the spread of HIV in sub-Saharan Africa. Using data from Swaziland, Tanzania, Uganda and Zambia, we estimated country-specific concurrency behaviour from sexual behaviour survey data on the number of partners in the past 12 months, and we developed a network model to compare the impact of three behaviour changes on the HIV epidemic: (1) changes in concurrent partnership patterns to strict monogamy; (2) partnership reduction among those with the greatest number of partners; and (3) partnership reduction among all individuals. We estimated the number of new HIV infections over 10 years and the cost per infection averted. Given our assumptions and model structure, we find that reducing concurrency among high-risk individuals averts the most infections and increasing monogamy the least (11.7% versus 8.7% reduction in new infections, on average, for a 10% reduction in concurrent partnerships). A campaign that costs US$1 per person annually is likely cost-saving if it reduces concurrency by 9% on average, given our baseline estimates of concurrency. In sensitivity analysis, the rank ordering of behaviour change scenarios was unaffected by potential over-estimation of concurrency, though the number of infections averted decreased and the cost per HIV infection averted increased. Concurrency reduction programmes may be effective and cost-effective in reducing HIV incidence in sub-Saharan Africa if they can achieve even modest impacts at similar costs to past mass media campaigns in the region. Reduced concurrency among high-risk individuals appears to be most effective in reducing HIV incidence, but concurrency reduction in other risk groups may yield nearly as much benefit.

Patterns of fluid accumulation on screening ultrasonography for blunt abdominal trauma: comparison with site of injury.

The objectives of this study were to define where fluid accumulation is shown on screening ultrasonography after blunt abdominal trauma and to determine how fluid accumulation patterns are associated with the site of injury. From 1994 to 1998, 2,693 screening examinations for blunt abdominal trauma were performed, in which 7 regions were examined for fluid. On the basis of a preliminary analysis of patients with solitary injuries, all 194 patients with sonographically detected fluid were grouped by fluid accumulation pattern. Fluid patterns were compared with sites of injury. The patterns differed between hepatic and splenic injuries. Fluid in the left upper quadrant, in both upper quadrants, or diffusely distributed suggested splenic injury, whereas fluid in the right upper quadrant or the right upper quadrant and lower recesses suggested hepatic injury (P < .0001). Fluid accumulation was random after enteric injury. Patients with extraperitoneal injury had no fluid or had fluid focally at the injury site. The ability to predict the injury site on the basis of fluid patterns should expedite treatment of hemodynamically unstable patients with blunt abdominal trauma.

Quantification of fluid on screening ultrasonography for blunt abdominal trauma: a simple scoring system to predict severity of injury.

A simple ultrasonographic method of fluid quantification, which counted the number of fluid recesses, was developed to predict the severity of injury after blunt abdominal trauma. From 1994 to 1998, 2,693 screening ultrasonographic examinations were performed for blunt abdominal trauma. Of this group, 2,499 patients had a fluid score of 0 (no fluid), and 1.4% had injuries (0.4% requiring surgery); 110 had a score of 1 (fluid in a single examined region), and 59% had injuries (13% requiring surgery); 33 had a score of 2, and 85% had injuries (36% requiring surgery); 30 had a score of 3, and 83% had injuries (63% requiring surgery); and 21 had a score of 4, and 95% had injuries (81 % requiring surgery). Patients with scores of 3 or greater had significantly higher rates of injury (P < .002) and injury requiring surgery (P < .0001) than patients with lower scores. The ability to predict injury severity on the basis of a simple ultrasonographic scoring system should expedite treatment of patients with severe trauma.

Us of blunt abdominal trauma: importance of free pelvic fluid in women of reproductive age.

PURPOSE: To assess the importance of free fluid and to determine the accuracy of screening ultrasonography (US) in female patients of reproductive age with trauma. MATERIALS AND METHODS: US was performed in 1,047 patients, aged 10-60 years, to evaluate blunt trauma. Patients were retrospectively assigned to groups on the basis of presence and location of intraperitoneal free fluid. Injury and surgical injury rates were assessed by comparing US results with computed tomographic, repeat US, cystographic, peritoneal lavage, surgical, and/or autopsy findings in 144 patients and with final clinical outcome in 903. US scans were positive if fluid was outside the cul-de-sac or if suspicious parenchymal abnormalities were present. RESULTS: In 939 patients, no fluid was seen: Eight had injuries; three were surgical. In 56, anechoic fluid was isolated to the cul-de-sac: Two had injuries; one was surgical. In 26, fluid was isolated to the upper abdomen: Fifteen had injuries; five were surgical. In 22, fluid involved the pelvis and abdomen: Nineteen had injuries; 14 were surgical. In four, questionable fluid was isolated to the supravesical space. Patients with fluid in the cul-de-sac had similar injury and surgical injury rates as those with no fluid but had lower rates than those of patients with fluid elsewhere (P<.02 to P<.001). US screening had 89% sensitivity, 98% specificity, 97% accuracy, a 61% positive predictive value, and a 99% negative predictive value. CONCLUSION: In female patients of reproductive age with trauma, free fluid isolated to the cul-de-sac is likely physiologic; clinical follow-up should suffice. Patients with fluid elsewhere usually have clinically important injury and require further evaluation.

Factors associated with bone mineral density in middle-aged men.

This cross-sectional population-based study examined the association of anthropometric and lifestyle risk factors with bone mineral density (BMD) in 218 white ambulatory men aged 50-64 from the Rancho Bernardo, California cohort. BMD was measured at the lumbar spine and hip using dual-energy X-ray absorptiometry and at the ultradistal wrist and midshaft radius of the forearm using single-photon absorptiometry. Body mass index (BMI) was significantly correlated with BMD at all four skeletal sites. Overall, 17.0% of men aged 55-64 were osteopenic (BMD > or = 2 SD below the distribution for ages 50-54) at one skeletal site, 16.5% were osteopenic at two sites, and 13.6% were osteopenic at three or more sites. Men who reported regular exercise had significantly higher BMD levels at the spine and hip. Men meeting the recommended daily allowance (RDA) for calcium intake (> or = 800 g/day) had significantly higher BMD levels at the spine and wrist. Alcohol intake and smoking were associated with differences of borderline significance in BMD at the spine. In analyses adjusted for BMI, weight change, exercise, smoking, drinking, and calcium intake, there was a significant independent age-related decline in BMD at the hip (0.008 g/cm2/year; p = 0.001), at the wrist (0.004 g/cm2; p < 0.01), at the forearm (0.006 g/cm2; p < 0.01), but not at the spine (0.005 g/cm2). These data, although cross-sectional, strongly suggest that age-related bone loss occurs in middle-aged men and that both physical activity and an adequate calcium intake are associated with better bone density.

The impact of bone size on broadband ultrasound attenuation.

Quantitative ultrasound (QUS) is a simple, inexpensive and radiation-free technique to study skeletal status in osteoporosis. Broadband ultrasound attenuation (BUA) is typically used without normalizing for bone thickness. We investigated the impact of bone thickness on BUA, both in in vitro and in vivo, using commercially available ultrasound scanners (Walker Sonix UBA 575 and 575+). For the study in vitro, we analyzed 12 paired cubes (12 x 12 x 12 mm3) of bovine trabecular bone cut from six "parent" blocks (24 x 12 x 12 mm3). These "parent" blocks showed a fairly homogeneous structure as assessed by conventional radiography. BUA and dual x-ray absorptiometry (DXA) measurements of bone mineral density (BMD) were obtained. The difference between the paired cubes was significant for BUA (p < 0.001), but not for BMD (p > 0.05). The BUA of the "parent" blocks was larger by 32-92% than the average BUA of the corresponding paired cubes, and always less than the sum of the paired cubes (5-34%). BUA thus added up in a complex and nonlinear fashion. Measurements in vivo of the calcaneal bone width demonstrated on radiographs (study in vivo I, 28 postmenopausal women) and CT images (study in vivo II, 17 women) showed a small, positive but not significant correlation with BUA (r2 = 0.13 and r2 = 0.007, p > 0.05). The magnitude of this effect provides further evidence that BUA does not scale linearly with bone size. Our results indicate that simple normalization of BUA data by specifying the results in decibels per megahertz per millimeter units may not be appropriate.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiographic absorptiometry for bone mineral measurement of the phalanges: precision and accuracy study.

PURPOSE: To evaluate the accuracy and precision of a radiographic absorptiometry (RA) method for assessment of bone mineral of the middle phalanges. MATERIALS AND METHODS: Nineteen cadaveric hands were radiographed with an aluminum wedge, once at 50 kVp and 400 mA and once at 60 kVp and 300 mA. Bone mineral content (BMC) and bone mineral density (BMD) of the second to fourth middle phalanges, expressed in arbitrary units (BMC-AU and BMD-AU), were analyzed and averaged in each hand. RESULTS: The precision error of this method was 1.0% for BMC-AU and 0.6% for BMD-AU. A 2.0%-2.4% reduction in BMD-AU seen on radiographs obtained through ethanol thicknesses of 5 and 6 mm compared with that seen on controls was statistically significant (P < .01). The correlation between BMC-AU and forearm BMC determined with dual x-ray absorptiometry was good (r = .887), and that between BMC-AU and ash weight in the phalanges was excellent (r = .983). CONCLUSION: The RA method is precise and accurate for bone mineral assessment of the peripheral appendicular skeleton.

Noninvasive bone mineral density measurement in the evaluation of osteoporosis.

Bone densitometry has developed considerably during the past several decades. Because the techniques have become more precise than before, osteoporotic patients can now be followed over time, allowing for assessment of disease or response to treatment. Several densitometry techniques have been shown to allow for the assessment of fracture risk. Factors other than density, however, additionally influence fracture risk. The next step will be the evaluation of microstructure and bone quality.