Big fleas have little fleas

T he delta agent is one of the most subtle of human pathogens, with an extreme of the parasitic life-style that is matched by few other organisms. It is capable of infecting only those individuals who are also actively infected with hepatitis B virus, and in these patients it causes very marked additional liver damage. Therefore, delta agent is of great interest, both because of the unusual requirements for its growth in cells, and because of its epidemiological effects. In this issue of the Journal (page 128), Dimitrakakis et al. report the steeply rising prevalence of delta infection which they have been able to document during the 15 years (1971-1985) since its introduction to Melbourne. During this time the number of acute cases of hepatitis B itself was also rising, though much more slowly. For both viruses, narcotic abuse appears to have been the significant factor, and delta infection was absent from most other categories of patient that are known to be at high risk of exposure to hepatitis B. Even patients with haemophilia had escaped parenteral infection, presumably because delta agent was automatically excluded from transfused blood products by the hepatitis B screening programme. Sexual transmission seems to have been of little importance in the spread of delta agent since neither homosexual men nor prostitutes were affected. The Melbourne study reveals a pattern similar to that seen in Sweden, 1 England," Eire' and the United States." In all these countries delta agent is one important cause of the multiple attacks of "non-A non-B" hepatitis which are a problem in intravenous drug abusers. The consensus of all these reports, as well as the experience in Italy where delta virus has become endemic," is that patients who are infected simultaneously with hepatitis B and delta viruses experienced a more severe illness than did those infected with hepatitis B alone. Similarly, delta superinfection produces renewed liver damage in chronic carriers of the virus. While the clinical significance of delta infection is becoming reasonably clear, the pathological events are still obscure. Delta antigen was first recognized in the nuclei of liver parenchymal cells by Rizzetto et al. who were using human sera as the source of antibody to detect hepatitis B core (HBc) antigen." They found that the sera from certain hepatitis B carriers stained the nuclei Neurodevelopment of 5-year-old very low birthweight survivors with attention deficit disorder. Paper presented at the Australian College of Paediatrics, 31st Annual Scientific Meeting, Canberra, May 21-23, 1986. 10. Kennell JH, Klaus MH. Care of the mother of the high-risk infant. Clin Obstet Gynaecol 1971; 14: 926-954. II. McCormick Me. Shapiro S, Stanfield B. Factors associated with maternal opinion of infant