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Background: We aimed to determine the household distribution and viability of Chlamydia trachomatis (Ct) from the eyes, face, and hands during the initial two visits of a year-long fortnightly cohort study in geographically defined adjacent households. Methods/Findings: We enrolled 298 individuals from 68 neighbouring households in Shashemene Woreda, Oromia, Ethiopia. All individuals above 2 years of age residing in these households were examined for signs of trachoma. Swab samples were taken from the conjunctiva, faces, and hands and analysed for the presence and viability of Ct. Ct viability was determined using reverse transcription (RT) PCR. At the initial visit, out of 298 individuals, 133 (44.5%) were children aged 2–9 years. Among these children, 27/133 (20.3%) had trachomatous inflammation—follicular (TF), while 8/133 (6.0%) had trachomatous inflammation—intense (TI). Ct (omcB or pORF2) was detected in 16/133 (12.0%) eye swabs, 14/105 (13.5%) face swabs, and 11/105 (10.5%) hand swabs from children aged 2–9 years. Among these children at visit one, 12/14 (85.7%) with Ct on faces and 9/11 (81.8%) with Ct on hands also had detectable ocular Ct. The severity of the disease worsened from the first visit to the second, and no participants showed clearance of the disease within the two-week period. Ct infection was associated with TF (P = 0.002) and TI (P = 0.060). At visit one, among children aged 2–9 years, viable Ct was detected in 12/16 (75.0%) ocular, 6/14 (42.9%) face, and 4/11 (36.4%) hand swab samples. All viable Ct detected on the faces and hands were identified from individuals with viable ocular infections. Among caregivers whose child tested positive for Ct on their hands, 3 caregivers also had Ct on their hands, accounting for 20% (3 out of 15). Additionally, among caregivers whose child tested positive for Ct on their faces, 2 caregivers had Ct on their faces, which accounts for 14.3% (2 out of 14). In two participants, we detected Ct on the hands of ocular-negative children at the initial visit and later detected ocular Ct at the second visit. Conclusion/Significance: Using RT-qPCR assay to detect Ct omp2 mRNA to define viability offers a new, informative perspective of trachoma transmission in this community in Ethiopia. The presence of viable Ct on the faces and hands of individuals living in households with people with current ocular Ct infection supports the hypothesis that hands and faces are important routes for transmission of trachoma. This highlights the importance of targeted interventions to address these sites of Ct carriage to help interrupt transmission. Author summary: Trachoma, caused by Chlamydia trachomatis (Ct), remains a leading cause of infectious blindness globally. Understanding how Ct is transmitted within households is crucial for designing effective interventions. In this study, we investigated the presence and viability of Ct on the eyes, faces, and hands of individuals in geographically adjacent households in Shashemene Woreda, Oromia, Ethiopia, over two visits during a year-long cohort study. We enrolled 298 participants from 68 neighbouring households, including 133 children aged 2–9 years. Trachomatous inflammation—follicular (TF) was observed in 20.3% of these children, and trachomatous inflammation—intense (TI) was found in 6.0%. Ct was detected in ocular, facial, and hand swabs, with a strong association between ocular Ct infection and the presence of viable Ct on the face and hands. Notably, 75.0% of ocular Ct infections in children were viable, as were 42.9% and 36.4% of infections on the face and hands, respectively. Viable Ct on the face and hands was predominantly identified in individuals who also had viable ocular infections. Caregivers of children with Ct on their faces or hands occasionally carried Ct themselves, underscoring potential intra-household transmission. We also observed cases where Ct on the hands preceded ocular infection, supporting the hypothesis that hands and faces play a critical role in disease spread. By utilizing reverse transcription PCR to detect viable Ct, this study provides an insights into transmission dynamics in this Ethiopian community. The findings emphasize the need for targeted interventions focusing on facial and hand hygiene to disrupt Ct transmission and support ongoing trachoma elimination efforts. [ABSTRACT FROM AUTHOR]

Musca sorbens (Diptera: Muscidae) flies are thought to be vectors of the blinding eye disease trachoma, carrying the bacterium Chlamydia trachomatis (Ct) between the eyes of individuals. While their role as vectors has been convincingly demonstrated via randomised controlled trials in The Gambia, studies of fly-borne trachoma transmission remain scant and as such our understanding of their ability to transmit Ct remains poor. We examined fly-eye contact and caught eye-seeking flies from 494 individuals (79% aged ≤9 years) in Oromia, Ethiopia. Ct-carrying flies (harbouring Ct DNA) were found to cluster spatially in and nearby to households in which at least one resident had Ct infection. Fly-eye contact was positively associated with the presence of trachoma (disease), lower human body weight and increased human body temperature. Studies of laboratory-reared M. sorbens indicated that Ct is found both externally and internally following feeds to Ct culture, with scanning electron microscopy revealing how Ct bodies can cling to fly hairs (setae). Testing for Ct on field-caught M. sorbens found fly 'bodies' (thorax, wings and abdomen) to consistently test positive for Ct while legs and heads were infrequently Ct-positive. These studies strongly support the role of M. sorbens as vectors of trachoma and highlight the need for improved understanding of fly-borne trachoma transmission dynamics and vector competence. Author summary: Trachoma is a blinding eye disease caused by an infection of the eye by the bacterium Chlamydia trachomatis (Ct). Trachoma is responsible for vision impairment or blindness in 1.8 million people and is the leading infectious cause of blindness worldwide. The presence of flies around the eyes of young children is a common feature of life in trachoma endemic communities worldwide. This fly is most often Musca sorbens, an understudied species thought to transmit Ct. In order to understand more about Musca sorbens flies and their relationship with Ct, the researchers studied 247 households in the Oromia region of Ethiopia, where there is known to be a lot of trachoma. The authors found evidence of Ct on flies and that flies in households containing children with Ct infection were much more likely themselves to be carrying Ct, adding to evidence that M. sorbens flies contribute to transmission of the bacterium. They also found that children who weigh less and currently have trachoma were more likely to have flies land on their face. Should further studies clearly elucidate a role for M. sorbens as vectors of trachoma, controlling fly populations or preventing fly-eye contact may become an important aspect of trachoma disease control. [ABSTRACT FROM AUTHOR]