Risk factors for trichiasis in women in Kongwa, Tanzania: a case-control study.

Women are at a greater risk compared to men for blinding complications from trachoma. In order to evaluate risk factors in women, 205 cases of trichiasis (TT) were selected from 11 villages in rural Tanzania. Each case of trichiasis was matched to two women of the same age and from the same village, who had no clinical signs of trachoma. Factors associated with trichiasis in a conditional logistic regression included history of trichiasis in the women's mother (odds ratio [OR] = 3.6; 95% confidence interval [CI]: 2.0-6.5); sleeping in a room with a cooking fire during childbearing years (OR = 1.8; 95% CI: 1.2-2.8); a home of wood and earth during childbearing years (OR = 2.1; 95% CI: 1.3-3.3); no adult education classes (OR = 2.2; 95% CI: 1.4-3.4); and five or more deaths among her children (OR = 2.6; 95% CI: 1.3-5.1). Detailed measures of prolonged exposure to child care as a young girl and as a mother showed no significant difference between cases and controls. Results from this study characterize women at high risk for severe disease and eventual blindness in a trachoma endemic area.

PIP: Ophthalmologists analyzed data on 205 women with ingrowing eyelashes caused by trachomatous scarring (trichiasis) with data on 410 age- and village-matched controls to determine risk factors for trichiasis in trachoma hyperendemic areas where women face a greater risk of trichiasis than do men. All women lived in the Kongwa subdistrict of Dodoma Region, Tanzania. Cases were 3.6 times more likely to have a mother who also had trichiasis. Family history of fathers or other relatives was not associated with trichiasis, however. Cases tended to have never married (odds ratio [OR] = 3.7), suggesting that in a society that expects marriage women with trichiasis were socially and economically marginalized. Mothers with trichiasis were more apt to experience at least 5 deaths of children than controls (OR = 2.6). The researchers assumed that a factor common to both trichiasis and increased child deaths (e.g., socioeconomic status) accounted for this association. Controls were more likely to have attended adult education classes than cases (OR = 2.2), yet attendance at primary school was not a predictor for trichiasis. Women who had slept in a room with a cooking fire during their reproductive years were more prone to trichiasis than women who did during childhood or as current practice (OR -1.8), indicating a more profound pathogenic response (scarring) to infection with Chlamydia trachomatis during pregnancy. Living in a wood/earth (i.e., traditional) home during childbearing years was also a significant predictor of trichiasis (OR = 2.1). These findings suggest that improving living conditions, educational opportunities, and socioeconomic status during the childbearing years would reduce the risk for trichiasis and blindness.

The epidemiology of trachoma in central Tanzania.

Trachoma is the leading infectious cause of blindness worldwide and data are needed on the epidemiological characteristics of active and residual disease in hyperendemic areas. This study describes the epidemiological characteristics of trachoma in Central Tanzania. Active, inflammatory disease peaks in pre-school children, with 60% showing signs of trachoma. Evidence of past infection, scarring, trichiasis, and corneal opacity, rose with age. In this population, 8% of those over age 55 had trichiasis/entropion. Females of all ages had more trachoma than males, with a fourfold increased risk of trichiasis observed in females. Women who were taking care of children appeared to have more active disease than non-caretakers. Clear evidence of clustering of trachoma by village, and within village, by neighbourhood was found. Clustering persisted even after accounting for differences in distance to water, local religion, and proportion of children with unclean faces. These findings have important implications for a trachoma control strategy.

The cryopreservation and in vitro cultivation of larval Onchocerca volvulus.

A system developed in our laboratory for the in vitro cultivation of larval Onchocerca volvulus is being employed in a series of morphogenetic, physiologic, chemotherapeutic and immunologic investigations of this parasite. Because of the need for a large and readily available supply of living worms for this work, cryogenic techniques are being used for the long-term preservation of larval parasites collected in various endemic areas of Guatemala, C.A. To date, microfilariae have survived frozen storage in human cutaneous tissues (excised nodules and skin snips) for as long as 504 days, and viable larvae, in all stages of development have been recovered from the black fly vectors (Simulium ochraceum and S. metallicum) kept frozen for 396 days. That cryopreservation does not appear to affect these parasites adversely is indicated by the fact that microfilariae derived from frozen tissues do not differ from those obtained from fresh tissues on the basis of: 1) numbers and vigor of emergent microfilariae; 2) survival and morphogenesis of microfilariae during cultivation in vitro for 24 days; 3) glucose utilization during 72 hours of incubation; and 4) their incorporation of 3H-amino acids as determined after 18 hours of incubation. Details of methodology for cryopreservation and in vitro cultivation, together with resultant data, are presented herein.

Aerobic and anaerobic carbohydrate metabolism and egg production of Schistosoma mansoni in vitro.

When S. mansoni adults were cultured in vitro for 12 days in a diphasic medium, their gross morphology, motor activity, frequency of sexual pairings, rates of glucose utilization and of lactic acid production were the same in the presence (90% N2/5% O2/5% CO2) or absence (95% N2/5% CO2) of oxygen. Therefore, no Pasteur effect, nor any reduction in lactic acid formation, was demonstrable under aerobic conditions. While aerobic conditions did not affect the rate of glycolysis, they had a marked effect on egg production. In the presence of oxygen, the rate of egg-laying reached a maximum between days 4 and 6. The average number of viable eggs produced per worm pair during this period was 118 (Sx equals 2.2), which is within the overall range (68 to 248) recorded by others for this same strain in vivo. Conversely, under anaerobic conditions in vitro, virtually no eggs were laid. It remains to be determined whether oxidative metabolism actually is required for energy to produce eggs, or whether some reaction yielding no ATP is essential for completion of their developmental process, such as tanning of the eggshall brought about by the oxidation of some phenolic compounds.