Serological and PCR investigation of Yersinia pestis in potential reservoir hosts from a plague outbreak focus in Zambia.

BACKGROUND: Plague is a bacterial zoonotic disease, caused by Yersinia pestis. Rodents are the natural hosts with fleas as the vehicle of disease transmission. Domestic and wild dogs and cats have also been identified as possible disease hosts. In Zambia, plague outbreaks have been reported in the Southern and Eastern regions in the last 20 years. Based on these observations, Y. pestis could possibly be endemically present in the area. METHODS: To substantiate such possibility, sera samples were collected from rodents, shrews, dogs and cats for detection of antibodies against Fraction 1 gene (Fra1) of Y. pestis while organs from rodents and shrews, and fleas from both dogs and rodents were collected to investigate plasminogen activator gene (pla gene) of Y. pestis using ELISA and PCR respectively. RESULTS: A total of 369 blood samples were collected from domestic carnivores, shrews and domestic and peri-domestic rodents while 199 organs were collected from the rodents and shrews. Blood samples were tested for antibodies against Fra1 antigen using ELISA and 3% (5/165) (95% CI 0.99-6.93%) dogs were positive while all cats were negative. Of 199 sera from rodents and shrews, 12.6% (95% CI 8.30-17.98%) were positive for antibodies against Fra1 using anti-rat IgG secondary antibody while using anti-mouse IgG secondary antibody, 17.6% (95% CI 12.57-23.60%) were positive. PCR was run on the organs and 2.5% (95% CI 0.82-5.77%) were positive for plasminogen activator gene of Y. pestis and the amplicons were sequenced and showed 99% identity with Y. pestis reference sequences. All 82 fleas collected from animals subjected to PCR, were negative for pla gene. The specific rat-flea and dog-flea indices were 0.19 and 0.27 respectively, which were lower than the level required to enhance chances of the disease outbreak. CONCLUSIONS: We concluded that plague was still endemic in the area and the disease may infect human beings if contact is enhanced between reservoir hosts and flea vectors. The lower specific rodent-flea Indices and absence of Y. pestis in the potential vectors were considered to be partly responsible for the current absence of plague outbreaks despite its presence in the sylvatic cycle.

Anti-tuberculosis treatment outcomes in HIV-infected adults exposed to isoniazid preventive therapy in Botswana.

SETTING: Eight public health clinics in Gaborone and Francistown, Botswana. OBJECTIVES: To describe the characteristics and outcomes of incident tuberculosis (TB) cases in human immunodeficiency virus (HIV) infected adults exposed to isoniazid preventive therapy (IPT) with access to antiretroviral and anti-tuberculosis treatment. DESIGN: In 1995 HIV-infected adults, TB disease was excluded before commencing IPT. During and after receipt of 6 or 36 months of IPT, symptomatic participants were evaluated using chest radiographs, sputum microscopy, cultures and drug susceptibility testing (DST). Incident TB cases received ≥6 months of anti-tuberculosis treatment. RESULTS: Seventy-five incident TB cases were identified among 619 symptomatic participants. The median duration of IPT in these cases was 6 months (range 1-35), and the median time to initiation of anti-tuberculosis treatment was 12 months after IPT cessation. Antiretroviral therapy (ART) was initiated before anti-tuberculosis treatment in 37 cases. Culture was positive in 43/58 (74%) TB cultures. DST was available for 38 cases, of which six (16%) were resistant to isoniazid (INH); 67/75 (89%) cases, including four with INH-monoresistant TB, completed anti-tuberculosis treatment or were cured. CONCLUSIONS: With prompt initiation of anti-tuberculosis treatment and access to ART, excellent outcomes were achieved in a public health setting in HIV-infected adults who developed TB disease.

Association of chest radiographic abnormalities with tuberculosis disease in asymptomatic HIV-infected adults.

SETTING: Francistown and Gaborone, Botswana. OBJECTIVE: Chest radiography is used to screen for tuberculosis (TB) in asymptomatic persons living with the human immunodeficiency virus (PLWH) seeking isoniazid preventive therapy (IPT). We describe radiographic features in PLWH in a TB-endemic setting and identify features associated with TB disease. DESIGN: Asymptomatic PLWH seeking IPT under program conditions for a clinical trial between 2004 and 2006 received chest radiographs (CXRs) that were read using the standardized Chest Radiograph Reading and Recording System (CRRS). Clinical characteristics, including TB disease, were compared with the radiographic findings. RESULTS: From 2732 screening CXRs, 183 had one or more abnormalities and were scored using CRRS, with 42% having infiltrates (36% upper lobes), 35% parenchymal fibrosis and 32% adenopathy. TB disease status was determined in 129 (70%) PLWH, of whom 22 (17%) had TB disease. TB disease was associated with upper lobe infiltrates (relative risk [RR] 3.0, 95%CI 1.5-6.2) and mediastinal adenopathy (RR 3.9, 95%CI 1.8-8.4). The sensitivity and specificity of either upper lobe infiltrates or mediastinal lymphadenopathy for TB disease were respectively 64% and 82%. CONCLUSION: A combination of CXR features was useful for predicting TB disease in asymptomatic PLWH. CRRS should be used more frequently in similar studies.

Tuberculosis in asymptomatic HIV-infected adults with abnormal chest radiographs screened for tuberculosis prevention.

BACKGROUND: Isoniazid preventive therapy (IPT) prevents tuberculosis (TB) in people living with HIV (human immunodeficiency virus, PLWH). Symptom screening without chest radiographs (CXRs) was established as the strategy for excluding TB disease among PLWH seeking IPT in Botswana's 2001 pilot project. This strategy was evaluated in 2004-2006 among candidates screened for an IPT clinical trial. METHODS: PLWH referred from clinics and HIV testing centers were screened for TB symptoms. All asymptomatic candidates received CXRs; those with abnormal CXRs were investigated further. RESULTS: Among 2732 asymptomatic candidates screened, 302 (11%) had abnormal CXRs potentially compatible with TB; TB disease was diagnosed in 43 of these 302 (14%), or 43 (1.6%) of the 2732 asymptomatic candidates. While not associated with CD4 lymphocyte counts < 200 cells/mm(3), TB was associated with a positive tuberculin skin test (relative risk 2.1, 95%CI 1.1-4.0). IPT was initiated in 113 (62%) of 182 asymptomatic PLWH with abnormal CXRs; 8/113 (7%) subsequently developed TB, and 7/8 (88%) successfully completed anti-tuberculosis treatment. CONCLUSIONS: The prevalences of abnormal CXRs and TB were respectively 2.6- and 8.9-fold higher among asymptomatic PLWH screened for the trial than in the pilot. A cost-effectiveness analysis is needed to determine whether the benefits of symptom screening alone are offset by the risk of inducing INH resistance by excluding CXRs during screening.

Characterisation of a Malawian isolate of Beauveria bassiana, a potential control agent of coffee stem borer, Monochamus leuconotus.

The radial growth, sporulation and viability of a Beauveria bassiana isolate were assessed at three temperatures (23, 28, 33 degrees C) under light and dark conditions. Optimum radial growth and sporulation occurred at 23 degrees C regardless of photoperiod with the highest spore concentration being attained after incubating for 28 days. Loss of viability was highest at 33 degrees C and there was no significant loss in viability at 23 degrees C for up to five weeks. It would appear that 33 degrees C is too hot for the sporulation, growth and viability of this insect fungus. Photoperiod effects were insignificant for all the parameters evaluated. The infectivity on white coffee stem borers at 2.5 x 10(8) spores ml(-1) was high with 100% of the test larvae immobilised and not feeding within 24 h and dying within two to twelve days.

The relentless spread of tuberculosis in Zambia--trends over the past 37 years (1964-2000).

OBJECTIVE: To review trends in the rates of tuberculosis (TB) case notifications over a 37-year period. DESIGN: A retrospective study of Ministry of Health records on TB notifications between 1 January 1964 and 31 December 2000. SETTING: Zambia, sub-Saharan Africa. METHODS: Retrospective analysis of case-notification data for TB of the Zambia Ministry of Health annual returns. OUTCOME MEASURES: Annual TB case-notification rates and trends over the past 37 years. RESULTS: TB case-notification data from 1964 to 2000 show a 12-fold increase over the past two decades, and apparent gains in controlling TB seen in the 1960s and 1970s have been reversed over the past two decades. A stable situation during the period 1964-1984 (case-notification rate remained around 100 per 100,000 population) was followed by an exponential increase since the mid-1980s. The absolute number of new TB cases increased from 8,246 in 1985 (124/100,000) to 38,863 (409/100,000) in 1996 and 52,000 (512/100,000) in 2000. Comparison of case-notification rates over the past 2 decades with neighbouring countries (Zimbabwe, Malawi and Tanzania) show that Zambia has one of the highest case-notification rates in the region. CONCLUSIONS: Zambia, like many countries in Africa, is in the midst of a serious TB epidemic and there are no signs that it is abating. This increase was most likely due to the impact of the HIV/AIDS epidemic and subsequent breakdown of TB services. Concerted donor-government efforts should invest appropriately in long-term plans for TB control.

Pathology and causes of death in a group of 128 predominantly HIV-positive patients in Botswana, 1997-1998.

BACKGROUND: Little is known about causes of death in countries of southern Africa seriously affected by the HIV/AIDS epidemic. METHODS: After obtaining informed consent, autopsies were performed on 128 mainly hospitalised adults in Francistown, Botswana, between July 1997 and June 1998. Criteria for case selection included those who died before a diagnosis could be established, those whose condition deteriorated unexpectedly during hospitalization, and those who had respiratory disease. This represented 14% of adult medical patients who died in hospital during the study period. RESULTS: Of the 128 patients, 104 (81%) were HIV-positive. Among HIV-positive patients, the most common pathologic findings were tuberculosis (TB) (40%), bacterial pneumonia (23%), Pneumocystis carinii pneumonia (11%), and Kaposi's sarcoma (11%); these conditions were the cause of death in 38%, 14%, 11%, and 6%, respectively. Of the 40 pulmonary TB cases, 90% also had disseminated extra-pulmonary TB. Chest radiology could not reliably distinguish the pathologies pre-mortem. CONCLUSIONS: TB was the leading cause of death in our series of HIV-positive adults in Botswana, selected towards those with chest disease; in most, it was widely disseminated. Bacterial pneumonia also played an important role in mortality. Pneumocystis carinii pneumonia was present, but relatively uncommon.