Lung function in African infants: a pilot study.

BACKGROUND: The burden of childhood respiratory illness is large in low and middle income countries (LMICs). Infant lung function (ILF) testing may provide useful information about lung growth and susceptibility to respiratory disease. However, ILF has not been widely available in LMICs settings where the greatest burden of childhood respiratory disease occurs. AIM: To implement and evaluate a pilot study of ILF testing in a semi-rural setting in South Africa. METHOD: Infant lung function testing was established at a community hospital in South Africa. All measures were done in unsedated infants during sleep. Measurements, made with the infant quietly breathing through a face mask and bacterial filter, included tidal breathing (TBFVL), exhaled nitric oxide (eNO), and sulphur hexafluoride multiple breath washout (MBW) measures using an ultrasonic flow meter and chemoluminescent NO analyzer. RESULTS: Twenty infants, mean age of 7.7 (SD 2.9) weeks were tested; 8 (40%) were Black African and 12 (60%) were mixed race. Five (25%) infants were preterm. There were 19 (95%) successful TBFVL and NO tests and 18 (90%) successful MBW tests. The mean tidal volume was 30.5 ml (SD 5.9), respiratory rate 50.2 breaths per minute (SD 8.7), and eNO 10.4 ppb (SD 7.3). The mean MBW measures were: functional residual capacity 71 ml (SD 13) and the lung clearance index 7.6 (SD 0.5). The intra-subject coefficient of variations (CV) of lung function measures were similar to published normative data for Caucasian European infants. CONCLUSION: In this study we demonstrate that unsedated infant lung function measures of tidal breathing, MBW, and eNO are feasible in a semi-rural African setting with rates comparable to those reported from high income countries.

Odor-induced host location in tsetse flies (Diptera: Glossinidae)

Four aspects of olfaction in host location by tsetse flies, Glossina spp., are discussed as follows: (1) host location and its mechanism, (2) factors affecting host location, (3) kairomones and host location, and (4) kairomones and host selection. Flight behavior in the various phases of host location (i.e., ranging, activation, orientation, and landing) in the absence and presence of olfactory cues is summarized. Movement toward an odor source is effected inter alia through optomotor-steered, upwind anemotaxis. It is still unclear how tsetse employ upwind anemotaxis to realize host location, considering the often highly variable wind direction. Olfactorily induced activation is governed by the olfactory cue perceived and threshold levels set by the internal state of the fly. The former depends on the odor source and distance from it; the latter is determined by species, sex, and physiological state. Wind direction and speed, as well as vegetation and the mobility of the host, interfere with successful completion of odor-induced host location. Close-range olfactory cues (including composition and concentration gradients), visual cues, and nutritional state determine whether a fly, having reached the host animal, will land on it. Carbon dioxide is important in host location because it induces landing and long-range attraction. The role of the other kairomones (acetone, 1-octen-3-ol, 4-methyl-phenol, and 3-n-propyl-phenol) is less clear. Apart from the complacency of various host species under tsetse attack, host choice by tsetse is predominantly opportunistic and primarily the result of the frequency of successful tsetse-host encounters. Nevertheless, host selection based on olfactory cues cannot be ruled out.

A trial to control the tsetse fly, Glossina morsitans centralis, with low densities of odour-baited targets in west Zambia.

A large-scale trial investigated the possibility of eradicating G.m.centralis from a traditional cattle rearing area using odour-baited targets at a reduced overall target density from 4 to 0.5-2.3 per km2, thus cutting down initial material costs by about 50%. Only the periphery of what was thought to be prime tsetse habitat (dense woodland) was treated with targets. These were all black or blue/black cloth (1.8 x 1 m), sprayed with deltamethrin suspension concentrate and baited with butanone and/or acetone (40-130 mg/h) and 1-octen-3-ol (0.5 mg/h). Although fly catches from traps and flyrounds initially dropped by approximately 3% per day and trypanosomiasis cases declined by 99% within a year, eradication was not achieved, so that more targets were deployed at a later stage. Although initially cheaper, the option of using reduced target densities proved financially unattractive because of prolonged periods of target maintenance prior to eradication. Revised strategies for tsetse control with odour-baited, insecticide-impregnated targets in west Zambia are presented.