Historical intensity of natural selection for resistance to tuberculosis

Infections have long been thought to exert natural selection on humans. Infectious disease resistance is frequently invoked as a mechanism shaping human genetic diversity, but such hypotheses have rarely been quantitatively evaluated with direct measures of disease-related mortality. Enhancement of genetically determined resistance to tuberculosis by natural selection has been proposed as a factor explaining the decline of tuberculosis in Europe and North America in the period 1830-1950 (before the advent of antimicrobial chemotherapy) and the apparently reduced susceptibility of Europeans and their descendants to tuberculosis infection and/or disease. We used Swedish vital statistics from 1891 to 1900 to estimate that individuals who escaped mortality from pulmonary tuberculosis (PTB) during the European tuberculosis epidemic would have enjoyed a fitness advantage of 7-15% per generation compared to individuals who were susceptible to PTB mortality; individuals with 50% protection would have had a selection coefficient of 4-7%/generation. Selection during the peak of the European TB epidemic could have substantially reduced the frequency of already rare alleles conferring increased susceptibility to PTB mortality, but only if the phenotypic effects of these alleles were very large. However, if resistant alleles were rare at the beginning of this period, 300 years would not have been long enough for such selection to increase their frequency to epidemiologically significant levels. Reductions in the frequency of rare susceptibility alleles could have played at most a small part in the decline of the epidemic in the century preceding 1950. Natural selection by PTB deaths during the European TB epidemic alone cannot account for the presently low level of TB disease observed among Europeans and their descendants just prior to the appearance of antibiotic treatment.

Epidemiology and control of tuberculosis in Taipei

OBJECTIVES

This retrospective study evaluated epidemiological trends in tuberculosis and the performance of a TB control program in Taipei.

METHODS

Data of all recorded tuberculosis cases from 1994 through 2000 obtained from the Tuberculosis Registry Center was used to analyze the trend of incidence. Tuberculin skin tests were also performed to estimate the prevalence and annual risk of tuberculosis infection in second-grade schoolchildren during the period 1996-1999. The management cards for all tuberculosis patients from 1992 to 1996 obtained from Taipei Municipal Chronic Disease Hospital were also reviewed.

RESULTS

The results show that incidence of tuberculosis had an increasing trend during the study periods with an average annual increase of 7.73% and 9.93% for males and females, respectively. Age-specific incidence showed a similar trend with a clear predominance of cases occurring in patients aged 25-34 and 65+ years. This bimodal pattern became more apparent in 2000. In second-grade schoolchildren, the annual risk of tuberculosis infection was approximately 0.68% with a decreasing trend over the study period. The relatively low cure rate of TB, averaging 47.2%, did not change significantly during the study period. Cure rate was significantly associated with patient's age, patient status as a new or recurrent case, and the development of side effects due to treatment with antituberculosis drugs.

CONCLUSIONS

Because of the low overall cure rate of 47.2%, this region of Taipei remains high TB rates. The inefficiency of the existing tuberculosis control program is largely to blame for the alarmingly high rates. The high percentage of recurrent cases and of cases in individuals aged 25-34 and older than 65 present a severe challenge to effective management and form a chronic pool of infectious cases. Our findings suggest that in order to achieve the WHO target of cure in 85% of TB cases, focusing effort on the identification and treatment of these groups is mandatory.

Serpens endocrania symmetrica (SES): a new term and a possible clue for identifying intrathoracic disease in skeletal populations

This paper describes a phenomenon in the endocranial plate, which we have termed "serpens endocrania symmetrica" (SES), and discusses its value as a diagnostic tool. The affected discolored bone area exhibits disruption of the endocranial surface, lending it a maze-like appearance. Histological sections demonstrate that the process is limited to the most superficial portion of the endocranium, with no diploic and ectocranial involvement (sinus areas excepted). Adult skulls (n = 1,884) from the Hamann-Todd collection (HTH), housed at the Cleveland Museum of Natural History, were utilized for the present study. SES was recognized in 32 of the 1,884 skulls studied (1.7%). The frequency of SES among individuals reported to have died from tuberculosis (TB) was 4.4%. The rate of SES in the non-TB sample was only 0.53%. The locations were as follows: limited to sinus area, 28.1%; calvarium (excluding the sinuses), 46.9%; sinus + calvarium, 25.0%. SES was bilateral in 90.9% of cases. Twenty-five of the 32 individuals (78.1%) with SES in the HTH collection had tuberculosis specifically listed as the cause of death. Six of the other 7 individuals had infections other than TB. In 29 of the 32 individuals with SES, infection involved structures within the thorax. As SES was also associated with another osteological phenomenon known to represent pulmonary disease, i.e., hypertrophic osteoarthropathy (HOA; 68.0% of SES individuals also had HOA), SES may be of diagnostic value in paleopathology for the recognition of intrathoracic disease, and perhaps tuberculosis.

Infections in Hispanic immigrants

Hispanic immigrants are an increasing portion of the United States (US) population. In addition to being at risk for diseases common in the US-born population, Hispanic immigrants also are at risk for infections that do not usually occur in the US-born population. Thus, such diseases as tuberculosis, neurocysticercosis, brucellosis, typhoid fever, malaria, amebiasis, viral exanthems, and hepatitis need to be considered in Hispanics who present with fever or focal lesions. When included in the differential diagnosis, most of these infections can be readily diagnosed and treated with currently available methods.

[Analysis of tuberculosis mortality in a general hospital of a large city]

In thanatogenesis of tuberculosis in emergency cases admitted to general hospitals in 1998-2000 predominated acute destructive prigressive forms which are most unfavourable epidemiologically. At autopsies tuberculosis is encountered 3 times more frequently. The diagnosis of tuberculosis is missed because of critical condition of the patients and their short stay in hospital due to early lethal outcome which doesn't allow adequate examination for tuberculosis.

Special coverage: 9th Conference on Retroviruses. TB, pneumonia deaths down, but heart attacks up

The profile of AIDS deaths has changed since HIV-infected patients began to receive highly active antiretroviral therapy in 1996. While fewer people are now dying overall, more are dying from non-AIDS-related diseases. Research from the Centers for Disease Control and Prevention and other sources is showing an increase in non-AIDS-defining illnesses. One CDC study presented at the recent retroviruses conference showed that while there have been declines in the proportions of deaths from some AIDS-related causes, there is an increase in deaths from non-AIDS-related causes, including liver and kidney disease and possibly ischemic heart disease.

[Tuberculosis in Russia in the late 20th century]

The present tuberculosis epidemic situation in Russia is marked by an increasing role of exogenous infection. The peak deteriorated epidemic situation was observed in 1993 and 1999. There was a considerable deterioration of the epidemic situation in 1999 due to the economic crisis in August 1998, which caused a drastic fall in living conditions. Trends for an epidemic process changed in the 1990s. Spread of tuberculous infection occurs by the same mechanisms as did in the early 20th century. The official incidence of tuberculosis does not completely reflect actual morbidity (nearly by 15%) due to the fact that patients with tuberculosis have not been detected.

Moderate to severe malnutrition in patients with tuberculosis is a risk factor associated with early death

A study was conducted in new patients registered with tuberculosis (TB) in a rural district of Malawi to determine (i) the prevalence of malnutrition on admission and (ii) the association between malnutrition and early mortality (defined as death within the first 4 weeks of treatment). There were 1181 patients with TB (576 men and 605 women), whose overall rate of infection with human immunodeficiency virus (HIV) was 80%. 673 TB patients (57%) were malnourished on admission (body mass index [BMI] < 18.5 kg/m2). There were 259 patients (22%) with mild malnutrition (BMI 17.0-18.4 kg/m2), 168 (14%) with moderate malnutrition (BMI 16.0-16.9 kg/m2) and 246 (21%) with severe malnutrition (BMI < 15.9 kg/m2). 95 patients (8%) died during the first 4 weeks. Significant risk factors for early mortality included increasing degrees of malnutrition, age > 35 years, and HIV seropositivity. Among all the 1181 patients, 10.9% of the 414 patients with moderate to severe malnutrition died in the first 4 weeks compared with 6.5% of the 767 patients with normal to mild malnutrition (odds ratio 1.8, 95% confidence interval 1.1-2.7). In patients with TB, BMI < 17.0 kg/m2 is associated with an increased risk of early death.

Transmembrane TNF induces an efficient cell-mediated immunity and resistance to Mycobacterium bovis bacillus Calmette-Guérin infection in the absence of secreted TNF and lymphotoxin-alpha

The contribution of a transmembrane (Tm) form of TNF to protective immunity against Mycobacterium bovis bacillus Calmette-Guérin (BCG) was studied in transgenic (tg) mice expressing a noncleavable Tm TNF but lacking the TNF/lymphotoxin-alpha (LT-alpha) locus (Tm TNF tg mice). These mice were as resistant to BCG infection as wild-type mice, whereas TNF/LT-alpha(-/-), TNF(-/-), and LT-alpha(-/-) mice succumbed. Tm TNF tg mice developed granulomas of smaller size but at 2- to 4-fold increased frequencies compared with wild-type mice. Granulomas were mainly formed by monocytes and activated macrophages expressing Tm TNF mRNA and accumulating acid phosphatase. NO synthase 2 activation as a key macrophage bactericidal mechanism was low during the acute phase of infection in Tm TNF tg mice but was still sufficient to limit bacterial growth and increased in late infection. While infection with virulent Mycobacterium tuberculosis resulted in very rapid death of TNF/LT-alpha(-/-) mice, it also resulted in survival of Tm TNF tg mice which presented an increase in the number of CFU in spleen (5-fold) and lungs (10-fold) as compared with bacterial load of wild-type mice. In conclusion, the Tm form of TNF induces an efficient cell-mediated immunity and total resistance against BCG even in the absence of LT-alpha and secreted TNF. However, Tm TNF-mediated protection against virulent M. tuberculosis infection can also be efficient but not as strong as in BCG infection, in which cognate cellular interactions may play a more predominant role in providing long-term surveillance and containment of BCG-infected macrophages.

Increased survival of persons with tuberculosis and human immunodeficiency virus infection, 1991--2000

To determine factors associated with the occurrence of human immunodeficiency virus (HIV) infection and tuberculosis (TB) disease (HIV-TB) and the associated survival rate, we analyzed patients with HIV-TB at Grady Memorial Hospital, Atlanta, Georgia, from 1991 through 2000. Overall, 644 patients with HIV-TB were seen. The number of HIV-TB cases per year was highest in 1992 (102 cases) and declined to 39 cases in 2000. Over time, patients were more likely to be enrolled in the HIV outpatient clinic (P<.01), but, in 1997, only 21 (51%) of 41 patients were enrolled in HIV-infection care programs and only 9 (22%) of 41 received HAART. The 1-year survival rate for patients with HIV-TB was 58% in 1991, 81% in 1994, and 83% in 1997 (P<.001). The increase in survival for patients with HIV-TB between 1991 and 1994 was likely due to improved TB and HIV therapy. More effective strategies for enrolling and maintaining HIV-TB patients in HIV-infection care programs could further increase survival.

Induction of an AIDS virus-related tuberculosis-like disease in macaques: a model of simian immunodeficiency virus- mycobacterium coinfection

The mechanism by which human immunodeficiency virus (HIV)-Mycobacterium tuberculosis coinfection facilitates development of HIV-related tuberculosis is poorly characterized. Macaque models of simian immunodeficiency virus (SIV(mac))-Mycobacterium bovis BCG coinfection were employed to explore the pathogenesis of AIDS virus-related tuberculosis. Following BCG coinfection, SIV (SIV)-infected macaques with high viral loads developed an SIV-related tuberculosis-like disease. This disease was characterized clinically by a syndrome of diarrhea, anorexia, weight loss, and altered levels of consciousness and pathologically by the presence of disseminated granulomas. In contrast, SIV(mac)-infected macaques with low viral loads either showed no evidence of BCG-induced disease or developed focal granulomatous lesions. Pathogenic SIV-BCG interactions appeared to play a critical role in triggering the development of this SIV-related tuberculosis-like disease. BCG coinfection enhanced the destruction of CD4(+) T cells in SIV(mac)-infected macaques whose viral loads were high. Reciprocally, exacerbations of SIV disease led to marked suppression of BCG-specific T-cell responses, persistence of the BCG infection, and development of an SIV-related tuberculosis-like disease. Furthermore, development of this SIV-related tuberculosis-like disease was also seen in naïve macaques simultaneously inoculated with SIV(mac) and BCG. These results provide in vivo evidence that coinfection of AIDS virus-infected individuals with an avirulent mycobacterium can lead to development of a tuberculosis-like disease.

[Somatic diseases as cause of death of patients with active tuberculosis]

Two hundred and fifteen case histories were studied to clarify causes of death in patients with active tuberculosis who had died from it. Males accounted for the largest proportion (86%) (n = 185). Patients above 50 years were 63.3% (n = 136). Two thirds were patients with restrictive tuberculosis without destruction and bacterial isolation. A hundred and fifty (70%) and 30% patients died from somatic diseases and other causes (sequels to alcohol abuse, violent death, suicide, etc.), respectively. Of the somatic diseases, cardiovascular diseases head the list, cancer ranks next to it, nonspecific respiratory diseases occupy the third place.

Treatment of tuberculosis in HIV-infected persons in the era of highly active antiretroviral therapy

OBJECTIVE

To assess the risks and benefits of administering highly active antiretroviral therapy (HAART) during the treatment of tuberculosis (TB) in HIV-infected patients.

DESIGN AND METHODS

HIV-1 patients presenting to 12 HIV centres in Greater London and south-east England with culture-proven TB were identified from January 1996 to June 1999. Case-notes were reviewed retrospectively.

RESULTS

Patients (n = 188) were severely immunocompromised with a median CD4 cell count at TB diagnosis of 90 x 106 cells/l (IQR: 30-180). At presentation, 85% (n = 159) were not taking antiretrovirals. A total of 45% commenced HAART during TB treatment, which was associated with significant reductions in viral load, AIDS-defining illness (ADI) [3.5 versus 24.5%; relative risk (RR) = 0.14] and mortality. Only nine of 91 (10%) patients with a CD4 count > 100 x 106 cells/l at TB diagnosis experienced a further ADI, whereas 18 of 92 (20%) patients with a CD4 count < 100 x 106 cells/l developed this complication. Adverse events (AE) occurred in 99 (54%) of 183 patients, one-third of whom changed or interrupted HIV and/or TB medication. The majority of AE occurred within the first 2 months, with peripheral neuropathy (21%), rash (17%) and gastrointestinal upset (10%) occurring most commonly.

CONCLUSIONS

Many physicians delay HAART in patients presenting with TB because of pill burden, drug/drug interactions and toxicity. Although the use of HAART led to significant reductions in viral load, ADI and mortality, co-infected patients commonly experienced AE leading to interruptions in TB/HIV therapy. We therefore recommend starting HAART early for patients with advanced HIV disease (CD4 < 100 x 106 cells/l) and deferring HAART until the continuation phase of TB therapy (i.e. after 2 months) for patients who are clinically stable (CD4 > 100 x 106 cells/l).

[Study on epidemic trend and control policy of tuberculosis in Sichuan province]

OBJECTIVE

To evaluate efficacy of tuberculosis control policy and provide scientific evidence for drawing up tuberculosis control program.

METHODS

Data of the epidemiological survey for tuberculosis in Sichuan in 2000 were analyzed and part of the results were compared with that before.

RESULTS

The prevalence of active pulmonary tuberculosis, the bacteriological positive prevalence and smear positive prevalence of pulmonary tuberculosis in 2000 were 544/100 000, 250/100 000 and 144/100 000, respectively, decreased by 41.8%, 30.0% and 35.0% respectively in comparison with 1990, and the annual reduction rates were 5.3%, 3.5% and 4.2% respectively during the past 10 years. The mortality of tuberculosis and pulmonary tuberculosis was 24/100 000 and 22/100 000, respectively, decreased by 20.0% and 12.0% respectively in comparison with 1990. The prevalence of tuberculosis in minority area and mountainous area were higher than that in city, countryside and hills. 71% of infectious patients were newly detected, 33.3% of which were re-treatment cases. The economic status was found the key factor affecting the implementation of tuberculosis control.

CONCLUSIONS

The modern tuberculosis control strategy, which mainly targeted infectious patients and advocated DOTS policy, is the guarantee of sustainable development of tuberculosis control, though the prevalence of pulmonary tuberculosis decreased slowly in Sichuan during the past 10 years.

[Report on fourth national epidemiological sampling survey of tuberculosis]

OBJECTIVE

To investigate the epidemiological trend of tuberculosis, to evaluate the efficacy of control measures and to provide scientific basis for making National Tuberculosis Control Programme 2001 approximately 2010.

METHODS

Tuberculin testing was carried out among 0 approximately 14 years old children; fluroscopy was carried out for >/= 15 years old population and children with >/= 10 mm reaction of tuberculin testing; chest X-ray film, sputum smear and culture were done for the patients of fluroscopy abnormal and suspects of tuberculosis symptom (persistent cough for 3 weeks or more); drug sensitivity test was done for the patients with culture positive; a retrospective study of tuberculosis mortality in 1999 was conducted at all investigation points; social economic study was done for the active pulmonary tuberculosis cases; the survey of tuberculosis infection rate for all population was carried out in 59 investigation points.

RESULTS

The population actually examined in this survey numbered 365 097. The examination rate was more than 95%. The prevalence of active pulmonary tuberculosis was 367/100 000, the prevalence of smear positive pulmonary tuberculosis was 122/100 000 and the prevalence of bacteriological positive pulmonary tuberculosis was 160/100 000. In comparison with 1979, the annual reduction rates were 4.5% for the standardized prevalence of active pulmonary tuberculosis and 3.8% for the standardized prevalence of smear positive pulmonary tuberculosis. In comparison with 1990, the annual reduction rates were 5.4% and 3.2%, respectively. The smear positive prevalence standardized showed a 44.4% decrease in the regions of implementing project of Health V but only 12.3% decrease in the regions without the project. The prevalence in the west region was higher than national average prevalence.

CONCLUSIONS

The epidemic of tuberculosis is still serious and prevalence decrease was slow. The governments at different levels must pay more attention to tuberculosis control programme, increase budget, implement DOTS strategy.

[Report on fourth epidemiological survey for tuberculosis in Heilongjiang province]

OBJECTIVE

To investigate the epidemiological trend of tuberculosis, to evaluate the efficacy of control measures and to provide scientific evidence for provincial 2001 approximately 2010 tuberculosis control programme.

METHODS

Tuberculin testing was carried out and BCG scar was examined among 0 approximately 14 years old children; fluroscopy was carried out for >/= 15 years old population and children of tuberculin testing positive; chest X-ray film, sputum smear and culture, drug sensitivity test were done for the patients of fluroscopy abnormal; the survey of tuberculosis infection rate for all population was carried out in 2 investigation points; a retrospective study of tuberculosis mortality was conducted at all investigation points; social economic study was done for the active pulmonary tuberculosis cases.

RESULTS

The overall examination rate was more than 95%. The prevalence of active pulmonary tuberculosis was 512/100 000, the prevalence of smear positive pulmonary tuberculosis was 121/100 000 and the prevalence of bacteriological positive pulmonary tuberculosis was 146/100 000. In comparison with 1979, the annual reduction rates were 3.2% for the prevalence of active pulmonary tuberculosis and 2.0% for the prevalence of smear positive pulmonary tuberculosis. In comparison with 1990, the annual reduction rates were 1.49% and 0, respectively. The prevalence increased slightly in city and decreased slowly in countryside.

CONCLUSIONS

The smear positive prevalence has not decreased since 1990. The governments at different levels must pay more attention to tuberculosis control programme, increase the budget, strengthen law management, implement DOTS strategy.