Microbial inciters of acute asthma in urban Nigerian children

In tropical Africa the role of microbial agents of acute respiratory infections in acute exacerbations of bronchial asthma remains largely unexplored. However, empirical antibacterial therapy is frequently initiated in moderate to severe cases of acute asthma with symptoms of acute respiratory infection. A study was set up to determine how often acute respiratory infection is associated with acute asthma, to identify the associated pathogens, and to proffer appropriate therapeutic suggestions.

Over a 16 month period, 86 episodes of acute asthma were studied for clinical and laboratory features of acute respiratory infection at the University College Hospital (UCH), Ibadan. Virological diagnosis was based on immunofluorescence studies of nasopharyngeal aspirates and/or serological tests using the microtitre complement fixation technique. Throat swabs and blood were cultured for bacterial agents.

Of the 64 cases who presented with rhinorrhoea, 51 (79.7%) were pyrexial (T > or = 37.6 degrees C). Inflammatory changes (frequently interstitial streakiness) were identified in 10 (19.6%) of the 51 chest radiographs; only two of these had lobar shadowing. Significant bacterial isolates were made in only three (3.5%) of the throat swabs and two (2.4%) of the blood cultures from the 86 cases; none had clinical septicaemia. On the other hand, 55 viral agents were identified from 39 (53%) of the 74 subjects studied; 16 (41.0%) had dual viral identifications. Respiratory syncytial virus (RSV) accounted for 20 (36.4%) identifications, parainfluenza virus (PIV) type 3 for 15 (27.3%), and influenza type A (Flu A) for 12 (21.8%). Viral identifications were significantly higher in infants and preschool subjects (< 5 years) and in those presenting with either rhinorrhoea or pyrexia.

The results of this study underscore the importance of viral upper respiratory infections in asthma exacerbations in a tropical setting. The paucity of clinical and investigative features of bacterial acute respiratory infection suggests that there is little rationale for routine antibiotic cover in children with acute exacerbations of asthma in the tropics.