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Trachoma Epidemiology:Transmission: The role of familiesThe importance of the family in sustaining trachoma was demonstrated by Barenfanger 1975 who compared two groups of infants around 1 years old, one group with sustained trachomatous infection and a second, uninfected group. In the former group, 50% of the associated family members had active infection as shown by the presence of chlamydial inclusions, with 80% of the siblings within 6 years of age to the index cases infected. In contrast in the uninfected group, only 9% of associated family members had active trachoma and only 20% of the comparable siblings. Other studies also providing evidence of the importance of families in the transmission of trachoma were reported by Haddad, 1965 and Grayston et al., 1985. However Assad et al 1971 found no evidence for the aggregation of cases in households in Taiwan. In The Gambia, computerized Monte Carlo simulation analysis of the distribution of trachoma in the village of Jali found no geographical association of diseased rooms or compounds [Bailey et al., 1989] similar to that which had been observed in South Africa [Ballard et al., 1981]. Cases of active trachoma were predominantly clustered in families, notwithstanding the presence in communal housing of interconnecting roof spaces through which flies could freely fly. This suggests that close contact with infected ocular secretions within the family is also a significant route of trachoma transmission. The observed importance of familial transmission in trachoma explains why older women, who "mother" or "granny" infected children and are thus more exposed to infection, are much more likely than their husbands to suffer the scarring sequelae of trachoma. It also raises operational questions as to whether attempts to prevent the disease by antibiotic treatment should be aimed at whole villages [which may be logistically simpler] or simply at households where infected cases have been identified [which might be more cost effective]. NEXT: The prevention of trachoma ReferencesAssad, F. A., Sundaresan, T. & Maxwell-Lyons, F. (1971). The household pattern of trachoma in Taiwan. Bulletin of the World Health Organisation 44, 605 - 615. Bailey, R., Osmond, C., Mabey, D. C. W.,
Whittle, H. C. & Ward, M. E. (1989). Analysis
of the household distribution of trachoma in a Gambian village using a Monte
Carlo simulation procedure. International Journal of
Epidemiology 18, 944-955. Ballard, R. C., Fehler, H. G., Baerveldt, G., Owen, G., Sutter E. E,, Mphahlele M. (1981). The epidemiology and geographical distribution of trachoma in Lebowa. South African Medical Journal 60, 531 - 535. Barenfangar, J. (1975). Studies on the role of the family unit in the transmission of trachoma. American Journal of Tropical Medicine and Hygiene 24, 509-515. Grayston, J. T., Wang, S-P., Leh, L. J. & Kuo, C-C.
(1985). The
importance of re-infection in the pathogenesis of trachoma. Reviews of
infectious diseases 7, 717 - 725. Haddad, N. A. (1965). Trachoma in Lebanon: observations on epidemiology in rural areas. American Journal of Tropical Medicine and Hygiene 14, 652-655. |
