Trends in tuberculosis incidence and their determinants in 134 countries.

OBJECTIVE: To determine whether differences in national trends in tuberculosis incidence are attributable to the variable success of control programmes or to biological, social and economic factors. METHODS: We used trends in case notifications as a measure of trends in incidence in 134 countries, from 1997 to 2006, and used regression analysis to explore the associations between these trends and 32 measures covering various aspects of development (1), the economy (6), the population (3), behavioural and biological risk factors (9), health services (6) and tuberculosis (TB) control (7). FINDINGS: The TB incidence rate changed annually within a range of +/-10% over the study period in the 134 countries examined, and its average value declined in 93 countries. The rate was declining more quickly in countries that had a higher human development index, lower child mortality and access to improved sanitation. General development measures were also dominant explanatory variables within regions, though correlation with TB incidence trends varied geographically. The TB incidence rate was falling more quickly in countries with greater health expenditure (situated in central and eastern Europe and the eastern Mediterranean), high-income countries with lower immigration, and countries with lower child mortality and HIV infection rates (located in Latin America and the Caribbean). The intensity of TB control varied widely, and a possible causal link with TB incidence was found only in Latin America and the Caribbean, where the rate of detection of smear-positive cases showed a negative correlation with national incidence trends. CONCLUSION: Although TB control programmes have averted millions of deaths, their effects on transmission and incidence rates are not yet widely detectable.

Strengite dissolution in flooded soils and sediments.

Strengite (FePO(4) . 2H(2)O) undergoes partial dissolution under the reducing conditions existing in a flooded soil. The greatest release of phosphate and iron occurs under conditions of low oxidation-reduction potential in combination with low pH.

Construction of chimeric phages and plasmids containing the origin of replication of bacteriophage lambda.

Segments of the replication control region of bacteriophage lambda (lambda) and lambda mutants defective in replication were attached in vitro to the phi80 phage vector Charon 3 and to the plasmid vector mini Col El (pVH51). The chimeric phages and plasmids have been used to localize the origin of lambda DNA replication and to facilitate a structural analysis of the lambda replicator.

Charon phages: safer derivatives of bacteriophage lambda for DNA cloning.

The Charon lambda bacteriophages have been developed as vectors for cloning. Their construction incorporates mutations that make them simple to use and also greatly increases their safety for the biological containment of cloned recombinant DNA. Three of the Charon vector phages, 3A, 4A, and 16A, have been certified for use as EK2 vector-host systems, when propagated in bulk in a special bacterial host, DP50SupF. We present here some of the data on which the safety of these systems was evaluated. DNA fragments ranging in size from 0 to 2.2 X 10(4) base pairs can be cloned in these EK2 Charon phages.

Imaging of small-scale features on 433 Eros from NEAR: evidence for a complex regolith.

On 25 October 2000, the Near Earth Asteroid Rendevous (NEAR)-Shoemaker spacecraft executed a low-altitude flyover of asteroid 433 Eros, making it possible to image the surface at a resolution of about 1 meter per pixel. The images reveal an evolved surface distinguished by an abundance of ejecta blocks, a dearth of small craters, and smooth material infilling some topographic lows. The subdued appearance of craters of different diameters and the variety of blocks and different degrees of their burial suggest that ejecta from several impact events blanketed the region imaged at closest approach and led to the building up of a substantial and complex regolith consisting of fine materials and abundant meter-sized blocks.

The measurement and estimation of tuberculosis mortality.

Tuberculosis (TB) ranks among the 10 principal causes of death and disability worldwide, largely on the basis of mortality estimates. These estimates have been derived by a variety of methods, from a limited database. Here we review the data and methods used to measure and estimate TB mortality in adults, assess the strengths and weaknesses of each and suggest ways to improve current mortality statistics. In principle, deaths attributable to TB can be obtained directly from national vital registration (VR) systems. However, only 59 of 213 countries in 2005 (including three in the World Health Organization Africa Region and one in the South-East Asia Region) had VR systems that reported TB deaths, corresponding to just 10% of all estimated deaths attributable to TB. Until comprehensive, national VR systems are established, an interim solution is to carry out verbal autopsies within sample VR schemes. The number of TB deaths from VR should ultimately converge with deaths recorded in national TB control programmes. At present, deaths in treatment cohorts cover a small subset of all estimated TB deaths (<13% in 2006), as deaths are missed among patients who are never diagnosed, who default or fail treatment, and among patients with untreated recurrent TB or TB sequelae. In contrast, some deaths recorded during treatment are not due to TB. To ensure convergence between cohort monitoring and VR, definitions of causes of death--including TB as an associate cause in deaths from human immunodeficiency virus/acquired immune-deficiency syndrome--should be standardised, so that both systems adhere to the International Classification of Diseases.

Measuring tuberculosis burden, trends, and the impact of control programmes.

The targets for tuberculosis control, framed within the United Nations' Millennium Development Goals, are to ensure that the incidence per head of tuberculosis is falling by 2015, and that the 1990 prevalence and mortality per head are halved by 2015. In monitoring progress in tuberculosis control, the ultimate aim for all countries is to count tuberculosis cases (incidence) accurately through routine surveillance. Disease prevalence surveys are costly and laborious, but give unbiased measures of tuberculosis burden and trends, and are justified in high-burden countries where many cases and deaths are missed by surveillance systems. Most countries in which tuberculosis is highly endemic do not yet have reliable death registration systems. Verbal autopsy, used in cause-of-death surveys, is an alternative, interim method of assessing tuberculosis mortality, but needs further validation. Although several new assays for Mycobacterium tuberculosis infection have recently been devised, the tuberculin skin test remains the only practical method of measuring infection in populations. However, this test typically has low specificity and is therefore best used comparatively to assess geographical and temporal variation in risk of infection. By 2015, every country should be able to assess progress in tuberculosis control by estimating the time trend in incidence, and the magnitude of reductions in either prevalence or deaths.

Global monitoring of collaborative TB-HIV activities.

Tuberculosis (TB) and human immunodeficiency virus (HIV) programs are increasingly working together towards providing universal access to integrated TB and HIV prevention, treatment, care and support services. To monitor progress we need to measure the delivery and impact of these services; however, the lack of investment in monitoring and evaluation and the added complexity of sharing data between two vertical programs, makes monitoring and evaluation of collaborative TB-HIV activities especially challenging. We describe the global system to record, report and analyse data on collaborative TB-HIV activities and summarize results to date. Although the data suggest that there is a steady increase in collaborative TB-HIV activities in many high-burden countries over time, we are already falling behind the globally agreed implementation milestones. This is due to a combination of slow implementation and lack of necessary tools and systems for capturing activity data. In particular, data from HIV program monitoring of TB screening, TB preventive treatments and TB infection control for people living with HIV is lacking. Much remains to be done by both programs to improve the implementation, monitoring and evaluation of collaborative TB-HIV activities and to optimize prevention, treatment and care for people infected with both TB and HIV, especially in areas at high risk of drug-resistant TB.

Tuberculosis deaths in countries with high HIV prevalence: what is their use as an indicator in tuberculosis programme monitoring and epidemiological surveillance?

Although the reduction of tuberculosis deaths is one of the aims of tuberculosis control, it has not always been a priority for National Tuberculosis Programmes (NTPs). The usual explanation is that death as a treatment outcome not associated with ongoing tuberculosis transmission is not relevant to the public health objective of cutting the cycle of disease transmission. However, death as an adverse outcome for tuberculosis patients and their families is an important indicator in NTP monitoring. Global health targets agreed as part of the Millennium Development Goals include the reduction of tuberculosis deaths. Tuberculosis deaths as an indicator of the impact of tuberculosis control measures are therefore important in the epidemiological surveillance of progress towards these targets. These considerations are particularly important in countries with high human immunodeficiency virus (HIV) prevalence where HIV has exacerbated the tuberculosis epidemic and is now the single best predictor of tuberculosis incidence. Tuberculosis deaths are also closely linked to HIV prevalence. Routine NTP data on tuberculosis cohort deaths are important in programme monitoring, and improvements in recording and reporting of deaths would help to overcome limitations in their accuracy. As routine NTP data on tuberculosis cohort deaths are insufficient as an indicator in epidemiological surveillance regarding the impact of NTPs on tuberculosis mortality, measuring progress towards targets for reduced tuberculosis deaths depends on improved national vital registration systems for a more accurate determination of tuberculosis mortality.

The entrainment of persistent tidal rhythmicity in a filter-feeding bivalve using cycles of food availability.

Austrovenus stutchburyi is an intertidal, burrowing, filter-feeding bivalve. It exhibits a strong, approximately tidal pattern in the time of gaping of its valves when in constant laboratory conditions. Individuals that have been held in laboratory conditions long enough to lose their overt gaping pattern will respond to pulses of algae made available at a tidal frequency by opening to coincide with the times when food is available and remaining closed at other times. The opening of the valves is not solely a response to the arrival of the food; usually, their opening anticipates the arrival of the regular food pulses. The tidal pattern seen during the pulsed food treatment will continue for two cycles when food is withheld, indicating the involvement of an internal timing mechanism that is responsive to pulses of food. The short persistence of the food-entrained rhythm in constant conditions suggests that the food-entrained oscillator is only a minor component of the timing system, and this conclusion is supported by the finding that for the first 4-5 days when freshly collected clams are held in the laboratory and supplied with food pulses around the times of expected high water, the "circa" period of their gaping rhythm is not adjusted to a strictly tidal one. The characteristics of the food-entrained oscillator are discussed in relation to existing knowledge of tidal oscillators and food-entrained circadian oscillators.

Quantitative assessment of HIV-1 DNA load by coamplification of HIV-1 gag and HLA-DQ-alpha genes.

We developed an assay for simultaneous amplification, detection and quantitation of HIV-1 gag gene and the DQ-alpha locus of the histocompatibility (HLA) region of the human genome by polymerase chain reaction (PCR). Crude cell lysates from control cell lines and peripheral blood mononuclear cells (PBMC) from HIV-1-infected and control individuals were coamplified using optimized concentrations of primers directed at both loci, followed by simultaneous hybridization with radioactively labeled HIV-1-gag and HLA-DQ-alpha probes. Simultaneous quantitation of the 242-base-pair HLA and 115-base-pair HIV products was accomplished by both end-point dilution analysis and image analysis of autoradiographs relative to standard curves derived from infected cell lines. We observed good agreement between input cell counts on fresh samples and the HLA-DQ-alpha target copy number values determined by both end-point dilution analysis and comparison of band intensities with standard curves. HIV-1 proviral load in symptomatic patients ranged from 200 to 4000 HIV-PCR-units per 1 x 10(6) PBMC (mean of 1245 copies), whereas asymptomatic patients had levels ranging from two to 1000 HIV-PCR-units per 1 x 10(6) PBMC (mean of 213 copies). This HIV/HLA coamplification approach should be particularly useful for analysis of frozen repository samples from natural history studies, and may facilitate wider application of quantitative PCR analysis.

HIV infection and silicosis: the impact of two potent risk factors on the incidence of mycobacterial disease in South African miners.

OBJECTIVE: To investigate the combined effects of HIV infection and silicosis on mycobacterial disease. DESIGN AND SETTING: A retrospective cohort of 1374 HIV-positive and 2648 HIV-negative miners who attended a South African gold mining hospital and primary health clinics. PARTICIPANTS: Miners who had been tested for HIV, with consent, at primary health clinics during 1991-1996, predominantly because of a symptomatic sexually transmitted disease. RESULTS: Tuberculosis (TB) incidence was 4.9 and 1.1 per 100 person-years in HIV-positive and HIV-negative miners respectively. The incidence of Mycobacterium kansasii disease was also high (0.32 and 0.10 per 100 person-years, respectively). Silicosis was highly prevalent, implying inadequate dust control, and was a significant TB risk factor among both HIV-positive and HIV-negative men (adjusted incidence rate ratios 1.4-2.5 according to radiological severity). The data were consistent with the risks of silicosis and HIV combining multiplicatively, but did not fit an additive model. The incidence of HIV-associated TB increased significantly during the study, with no corresponding change in HIV-negative rates, to reach 16.1 per 100 person-years among HIV-positive silicotics. CONCLUSIONS: The risks of silicosis and HIV infection combine multiplicatively, so that TB remains as much a silica-related occupational disease in HIV-positive as in HIV-negative miners, and HIV-positive silicotics have considerably higher TB incidence rates than those reported from other HIV-positive Africans. The increasing impact of HIV over time may indicate epidemic TB transmission with rapid disease development in HIV-infected miners. Similar but currently unrecognized interactions may be contributing to TB control problems in other industrializing countries affected by the HIV epidemic.

A simplified and efficient vector-primer cDNA cloning system.

A simplified, efficient, and versatile vector-primer cDNA cloning system is presented. The dimer-primer system is a modification of the method of Okayama and Berg (1982) with the following features: (i) the vector-primer molecules are more rapidly and reliably prepared by virtue of the elimination of an endonuclease digestion and the agarose gel purification step from the original method, and (ii) the final cDNA products contain polylinkers at both cDNA-vector junctions, simplifying the size analysis, subcloning, and sequencing of inserts. The system is highly efficient, yielding greater than 10(5) transformants using 1 microgram mRNA and 1 pmol of vector-primer ends, with 75% or more of the transformants having inserts. The ability of the system to produce clones of full-length or near full-length is demonstrated by the analysis of 32 ribulose-1,5-bisphosphate carboxylase small subunit cDNA clones from tomato.

Isolation of a tomato alcohol dehydrogenase 2-encoding cDNA using phage-promoted antibody screening of a plasmid cDNA library.

We describe the cloning of a cDNA encoding tomato alcohol dehydrogenase 2 (Adh2) by screening plasmid cDNA clones in phage plaques. A cDNA library constructed in a plasmid vector containing a unique SstI site at the 5' end of the cDNA insert was transferred into the SstI site of the lacZ gene of phage lambda Charon16, and screened by anti-Adh2 antibody to identify reactive plaques. Plasmid cDNA clones were recovered by SstI digestion, ligation, and transformation from phage minipreps for subsequent characterization. This system preserves the original plasmid library for subsequent screening with nucleic acid probes to identify full-length, multiple independent, or related cDNA clones not subject to the selection pressure of phage growth or lysogeny, or negative antibody reactivity. Thirty-two cDNA clones were identified with polyclonal antiserum to Adh2. Three of these reacted with monoclonal anti-Adh2 and only those three hybridized to maize adh1 sequence. One of these cDNAs, Adh31, was further characterized as encoding Adh2 by hybrid-selected translation and high sequence homology with the maize adh1 gene.

A mouse genetic locus with death clock and life clock features.

A senility syndrome, with weight loss and priapism, occurs in CBAT6/T6 mice, an exceptionally long-lived strain. Instead of dying at the expected time, these mice get senile weight loss and priapism and go on living. We have postulated that a mutant death clock kills the wrong neurons. Crosses with the NZW and C57BL/6 strains show causation by a single genetic locus (Priap1), with a pronounced gene dosage effect on timing. We report here that various cancers were the cause of death in 31 of 32 NZW mice, compared to only five of 22 CBAT6/T6 mice, a highly significant difference (P<0.001). The longevity of (CBAT6/T6xNZW)F1 hybrids, and the segregation of longevity with priapism and senile weight loss in (CBAT6/T6xNZW) F2 hybrids, indicates that Priap1, or a linked gene, inhibits the cancers that usually shorten the lives of NZW mice. If a timer gene is involved, the cancer resistance action could be because the locus impedes the normal mid-life regression of anti-cancer defence. The priapism suggests loss of the medullary reticular formation neurons which normally inhibit male spinal sexual reflexes. In this region of the medulla there are also the respiratory and cardiac control centres, where apoptotic neuron destruction by the wild-type locus could govern maximal life-span. The CBAT6/T6 locus may be a mutant life-stage control clock. Its discovery could be the revelation of a new, major class of aetiology of disease.

Malnutrition, age and the risk of parasitic disease: visceral leishmaniasis revisited.

Children are said to be at greater risk of developing visceral leishmaniasis (VL) when they are younger and more malnourished. If malnutrition really is associated with VL, this potentially fatal and visible disease may be a general indicator of community health among the rural and suburban poor. Previous conclusions reached about the roles of malnutrition and age in VL epidemiology are questionable because they may have been confounded by transmission rate, because they have not been able to distinguish between different mechanisms of acquiring immunity, and because empirical observations have not been compared with theoretical expectations. Here we offer a framework with which to investigate these questions quantitatively, and do so with published data from endemic areas of Brazil. We conclude that children are indeed more susceptible to VL when they are younger and more malnourished, but it remains unclear whether the immunity to VL acquired with age is always acquired as a result of infection. The significance for leishmaniasis control, and for the control of other diseases associated with malnutrition, will depend on underlying mechanisms, which are not yet understood.