RESUMEN
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 on 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.
Asunto(s)
Chlamydia trachomatis , Insectos Vectores , Tracoma , Chlamydia trachomatis/aislamiento & purificación , Chlamydia trachomatis/fisiología , Animales , Humanos , Etiopía , Tracoma/transmisión , Tracoma/microbiología , Femenino , Masculino , Insectos Vectores/microbiología , Niño , Preescolar , Muscidae/microbiología , Lactante , Ojo/microbiología , Adolescente , Adulto , Adulto JovenRESUMEN
BACKGROUND: Trachoma, the leading infectious cause of blindness, is caused by the bacterium Chlamydia trachomatis (Ct). Despite enormous disease control efforts and encouraging progress, trachoma remains a significant public health problem in 44 countries. Ethiopia has the greatest burden of trachoma worldwide, however, robust data exploring transmission risk factors and the association between socio-economic status is lacking from some regions. This is the first study to investigate these factors in this South-Eastern region of Oromia, Ethiopia. METHODOLOGY/PRINCIPAL FINDINGS: A total of 1211 individuals were enrolled from 247 households in Shashemene Rural district in Oromia Region between 11th April and 25th June 2018, of whom 628 (51.9%) were female and 526 (43.4%) were children aged 1-9 years. Three standardised ophthalmic nurses examined each participant for the presence of active trachoma using the WHO simplified trachoma grading system. Conjunctival swab samples were collected from the upper tarsal conjunctiva of the left eye of each participant. Ct was detected using quantitative PCR. Risk factor data were collected through structured interviews and direct observations. Clinical signs of trachomatous inflammation-follicular among children aged 1-9 (TF1-9) were observed in at least one eye of 106/526 (20.2%) and trachomatous inflammation-intense among children aged 1-9 (TI1-9) were observed in at least one eye of 10/526 (1.9%). We detected Ct by PCR in 23 individuals, of whom 18 (78.3%) were in children aged 1-9 years. Among the 106 children aged 1-9 years with TF, 12 (11.3%) were Ct PCR positive and among 20 children aged 1-9 years with TI, 4 (20.0%) were Ct PCR positive. In a multivariable model, adjusting for household clustering, active trachoma was associated with younger age, the poorest households (aOR = 2.56, 95% CI 1.21-5.51), presence of flies on the face (aOR = 2.87, 95% CI 1.69-6.46), and ocular discharge (aOR = 1.89, 95% CI 1.03-3.24). Pre-school children face washing more than once a day had lower odds of having active trachoma (aOR = 0.59, 95% CI 0.19-0.84). The same was true for washing children's clothing at least once per week (aOR = 0.27, 95% CI 0.33-1.02). CONCLUSION/SIGNIFICANCE: Younger age, personal hygiene in this age group (presence of ocular and nasal discharges, infrequent washing of faces and clothing) and fly-eye contacts are potential risk factors for trachoma in this setting, suggesting that hygiene interventions and environmental improvements are required to suppress transmission to ensure sustained reduction in disease burden Further studies are needed to evaluate these interventions for trachoma control and elimination. Trachoma remains a disease associated with lower socio-economic status, emphasising the need for continued implementation of control measures in addition to poverty reduction interventions in this region.
Asunto(s)
Tracoma , Humanos , Femenino , Preescolar , Lactante , Niño , Masculino , Tracoma/microbiología , Etiopía/epidemiología , Chlamydia trachomatis , Factores de Riesgo , Inflamación , Conjuntiva , PrevalenciaRESUMEN
BACKGROUND: Trachoma elimination efforts are hampered by limited understanding of Chlamydia trachomatis (Ct) transmission routes. Here we aimed to detect Ct DNA at non-ocular sites and on eye-seeking flies. METHODS: A population-based household survey was conducted in Oromia Region, Ethiopia. Ocular and non-ocular (faces, hands, clothing, water containers and sleeping surfaces) swabs were collected from all individuals. Flies were caught from faces of children. Flies, ocular swabs and non-ocular swabs were tested for Ct by quantitative PCR. RESULTS: In total, 1220 individuals in 247 households were assessed. Active trachoma (trachomatous inflammation-follicular) and ocular Ct were detected in 10% and 2% of all-ages, and 21% and 3% of 1-9-year-olds, respectively. Ct was detected in 12% (95% CI:8-15%) of tested non-ocular swabs from ocular-positive households, but in none of the non-ocular swabs from ocular-negative households. Ct was detected on 24% (95% CI:18-32%) of flies from ocular-positive households and 3% (95% CI:1-6%) of flies from ocular-negative households. CONCLUSION: Ct DNA was detected on hands, faces and clothing of individuals living in ocular-positive households suggesting that this might be a route of transmission within Ct infected households. In addition, we detected Ct on flies from ocular-positive households and occasionally in ocular-negative households suggesting that flies might be a vector for transmission within and between Ct infected and uninfected households. These potential transmission routes may need to be simultaneously addressed to suppress transmission.
Asunto(s)
Infecciones por Chlamydia/diagnóstico , Infecciones por Chlamydia/transmisión , Chlamydia trachomatis/aislamiento & purificación , Infecciones Comunitarias Adquiridas/diagnóstico , Infecciones Comunitarias Adquiridas/transmisión , Transmisión de Enfermedad Infecciosa , Adolescente , Adulto , Animales , Niño , Preescolar , Chlamydia trachomatis/genética , Vestuario , Estudios Transversales , Dípteros/microbiología , Etiopía , Heces/microbiología , Femenino , Fómites/microbiología , Mano/microbiología , Humanos , Lactante , Masculino , Persona de Mediana Edad , Reacción en Cadena en Tiempo Real de la Polimerasa , Adulto JovenRESUMEN
Eye-to-eye transmission of Chlamydia trachomatis, the causative agent of trachoma, may be plausibly interrupted if faces are kept free of ocular and nasal discharge. Between April and June 2018, 83 children aged 1-9 years with active trachoma were recruited from 62 households and allocated to a face cleaning protocol: face washing with water, face washing with water and soap, or face wiping. Faces were examined for the presence of ocular and nasal discharge, and swabs were taken from faces and hands to test for C. trachomatis at baseline, immediately post protocol, and after 1, 2, and 4 hours (washing protocols). Washing with soap was more effective at removing ocular discharge than either washing with water (89% and 27% of discharge removed, respectively, P = 0.003) or wiping with a hand (42%, P = 0.013). The reduction in prevalence of ocular discharge was sustained for at least four hours. The prevalence of C. trachomatis on face swabs was reduced by all washing protocols. The importance of soap should not be overlooked during facial cleanliness promotion.