Trichomonas vaginalis epidemiology: parameterising and analysing a model of treatment interventions

Background: Trichomonas vaginalis, which affects at least 170 million indiv iduals globally, may increase the risk of transmission of HIV and predispos e pregnant women to premature rupture of membranes and early labour. Objective: To more clearly define the epidemiology of trichomoniasis and to develop a mathematical model of disease transmission dynamics in order to explore various treatment strategies. Design: A deterministic model of trichomoniasis was constructed. Parameter values were set to fit the model to known endemic prevalence levels of Tric homonas vaginalis. Two treatment interventions ("screening" and "syndromic management") were simulated. Results: The age specific prevalence of the disease was seen to differ from other STDs in a number of studies. Parameter fitting indicates that the av erage duration of infection in women is at least 3-5 years and approximatel y 4 months for men. "Syndromic management" (that is, treating only those wi th symptoms of disease) had minimal effect upon the endemic prevalence of d isease even at high levels of coverage. "Screening" (that is, identificatio n of individuals with both symptomatic and asymptomatic infection) was show n to be the most efficient method of control, but was sensitive to the scre ening interval. Conclusions: The control of trichomoniasis seems to have been a success in developed countries because of the regular access to health care, whereas i t has remained endemic in many developing countries where control may only be possible by regular screening and treatment. However, without a large in vestment in services, success in controlling trichomoniasis is likely to be transitory.