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Methylene blue is a good background stain for tuberculosis light-emitting diode fluorescence microscopy
No full textSETTING: Damien Foundation Bangladesh tuberculosis (TB) control projects. OBJECTIVES: To compare blue ink, potassium permanganate and methylene blue background staining for transmitted light-emitting diode (LED) TB fluorescence microscopy (FM). DESIGN: Auramine smears made in triplicate from Ziehl-Neelsen (ZN) acid-fast bacilli (AFB) positive or negative sputum and stained with one of the background variations were read blind by LED FM. Reference laboratory rechecking of discordant series was used before and after auramine restaining as the gold standard. RESULTS: Of 1977 series evaluated, 991 (50.1%) were made from ZN-positive specimens. There were 919, 942 and 958 FM true-positives with blue ink, permanganate and methylene blue counterstaining, against respectively 12, 12 and 16 false-positives. Methylene blue counterstaining was more sensitive (95.6%, 95%CI 94.2-96.8) than blue ink or permanganate (92.7%, 95%CI 90.9-94.3 and 93.6%, 95%CI 91.9-95.0; respectively P < 0.01 and <0.05). No AFB could be found in 85% and 18% of 180 discordant series without and with restaining. CONCLUSIONS: Methylene blue is at least equivalent to potassium permanganate counterstaining for FM using blue LED transmitted excitation and is cheaper than blue ink. Restaining of all smears prior to first re-reading may be unavoidable for blinded rechecking of auramine-stained smears for external quality assessment
A new format of the CATT test for the detection of Human African Trypanosomiasis, designed for use in peripheral health facilities
No full textDiagnosis of drug-resistant tuberculosis: reliability and rapidity of detection
No full textWith the emergence of multidrug-resistant tuberculosis (MDR-TB), the need for rapid drug susceptibility testing (DST) is felt globally. National tuberculosis control programmes (NTPs) may find it hard to choose from the bewildering variety of rapid tests. We give an overview of the most important methods, discussing their merits and shortcomings, emphasising techniques that offer an alternative to the commercial systems and genotypic tests. Correlation between phenotypic and genotypic DST remains problematic due to our insufficient knowledge of the mutations underlying drug resistance, besides the past standardisation of phenotypic DST. Rapid growth-based DST tends to be less accurate due to growth retardation of some resistant strains. To arrive at optimal resistance monitoring and management of MDR-TB without overloading the laboratories, the test indications and definition of a suspect need careful consideration, while excellent microscopy remains crucial but challenging. The hitherto little-studied fluorescein diacetate vital staining technique may offer the solution, reconciling earlier detection and appropriate pre-selection for rapid DST. For the choice of methods, appropriateness and sustainability should be considered in conjunction with the prospects for complete population coverage. Excellent coverage will only be feasible through decentralisation of simple, low-requirement methods or alternatively by centralised genotypic DST with, in principle, easy specimen referral. The small differences in DST turnover time are relatively unimportant, provided primary culture isolation is not required. No test is fully accurate, and proper pre-selection may allow the use of less accurate but simple screening methods. Conventional slow DST will still be needed for confirmation and for epidemiological monitoring
Personal protection by long-lasting insecticidal hammocks against the bites of forest malaria vectors
No full textSummary Objective In Southeast Asia, malaria vectors bite outside the houses before bedtime, and forest dwellers rarely use insecticide-treated nets (ITNs). Thus, we tested the protection of long-lasting insecticidal hammocks (LLIH) using Olyset technology against exophagic vectors in two forest villages of Cambodia. Methods In each village, we conducted two entomological surveys (middle and end of the rainy season), each lasting 10 consecutive nights. These comprised human landing collections during the whole night by people sitting outside in the hammocks. Five households were selected per village, and for each household, two fixed positions were allocated: one for the control and one for the treated hammock. Results In total, 6449 mosquitoes were collected from control hammocks compared to 4481 in treated hammocks. Personal protection conferred by the hammocks was 46% (CI 95%: 35-55%) against the bites of Anopheles minimus. A significant reduction of An. dirus bites (46% CI 95%: 25-62%) was only observed at the end of the rainy season. An. maculatus and culicines bites were only reduced in one of the two study sites. Conclusion Even if this LLIH is not inducing full protection against the bites of malaria vectors, it could prove effective in protecting forest workers and villagers before sleeping time. LLIH can be an additional and valuable tool in eliminating artemisinin-resistant malaria in the region
Immunodiagnosis of Taenia solium taeniosis/cysticercosis
No full textNeurocysticercosis, the infection of the central nervous system by larvae of Taenia solium, is a major cause of epilepsy in developing countries. This cestode is a public health problem in most developing countries where pigs are raised and its occurrence is strongly associated with poverty. The development of immunodiagnostic tools has contributed to our knowledge on the importance of this parasite by enabling seroepidemiological surveys and community-based studies to be conducted. Here, we present a comprehensive overview of the various proteins used in antibody detection techniques, as well as the latest developments in antigen detection techniques and serodiagnosis of taeniosis. A critical view on the use of serology in epidemiological studies and clinical control programs is given and future research needs are presented. Copyright 2010 Elsevier Ltd. All rights reserved
Demonstration of differences in virulence between two Theileria parva isolates
No full textIn areas with a low incidence of infection due to unimodal presence of ticks, Theileria parva has been observed to induce a disease with relatively low pathology. This is followed by a carrier state, rather than death and therefore provides a better chance of transmission of the parasite back to the tick vector since in unimodal conditions, the different tick stages occur at different times. One isolate from such an area in Zambia, T. parva Chitongo, was compared for virulence with T. parva Muguga, isolated from an area exhibiting a continuous presence of all vector stages in East Africa. To reduce any variation due to infection dose, an in vitro standardized dose was used to initiate infection of groups of three local zebu cattle with each isolate. Parameters of virulence measured were prepatent period, fever, survival (based on ECF index), parasitosis, piroplasm parasitaemia and hematological parameters. Our results suggest that T. parva Chitongo developed a slightly later onset (1-2 days) and lower levels of parasitosis in the lymph node, causing less and later mortality. Comparison of the in vitro rate of transformation confirmed that the time needed to transform an infected lymphocyte took 4 days longer for T. parva Chitongo than T. parva Muguga. Elucidating the mechanism responsible for the lower virulence of T. parva Chitongo could be useful for designing an attenuated vaccine
