Although T. vaginalis has been confirmed to be linked to a range of adverse gynecological and obstetric outcomes, little emphasis has been placed on detecting its prevalence and risk factors in the recent past, such that there is no overall prevalence rate in China. This population-based study compared the prevalence rate of T. vaginalis in two hospitals located in different geographical regions (central vs western China). A relatively high rate (20.94%) of T. vaginalis-infected females was identified in the Tibetan area compared with those (2.84%) obtained in Wuhan city. Among this population, risk factors related to T. vaginalis infection include lower educational status and family income, clinical symptoms and a high level of vaginal cleanliness.
T. vaginalis prevalence was present in 20.94% of these Tibetan patients, which was obviously higher than that in the WHO regions and other reported regions in China (P < 0.05, Fig. 2) but comparable to the rate (20.14%) among HIV-positive pregnant women, as recently reported in South Africa (Peters et al. 2021). However, also in South Africa, a systematic review including 48 studies from 2015 to 2020 reported a pooled prevalence of 13.8% among pregnant women (Nyemba et al. 2021). This illustrates that the prevalence of T. vaginalis varies based on population characteristics. Although the disparity between the two regions presented above might be due to the difference in the target population, this result indicated the widespread existence of T. vaginalis infection in the Tibetan area. Although wet-mount microscopy showed a poorer sensitivity (Ghallab et al. 2021) for detecting T. vaginalis in the Tibetan area than nucleic acid hybridization, which was used in Wuhan city, the result was unexpected. Thus, identifying socioeconomic status and behavioral and lifestyle factors rather than the population specificity of selected Tibetan women might be crucial to explain the T. vaginalis prevalence.
Furthermore, it is well established that T. vaginalis infection is a sexually transmitted infection transmitted mainly by sexual activity (Workowski and Bolan 2015). Inadequate treatment and the lack of concurrent treatment of sexual partners may be related to the continuing epidemics of T. vaginalis infection(Schumann and Plasner 2022). As Fig. 1 shows, the prevalence of T. vaginalis infection was highest in this area, followed by BV and VVC. This result was inconsistent with some previous reports including another Tibetan area in China and a resource-limited region in India, both of which showed that T. vaginalis was less common than BV or VVC (Dai et al. 2010; Khan et al. 2019). Lack of formal treatment for T. vaginalis infection seems to give a reason for the disparity, leading to a high prevalence.
In this study, women with educational levels lower than college were more likely to be involved in T. vaginalis infection, which is consistent with other studies by Tompkins et al., Rosenbaum et al. and Aboyeji et al. (Aboyeji and Nwabuisi 2003; Rosenbaum 2018; Tompkins et al. 2020). As a result of lower education, women may lack knowledge of T. vaginalis or other vaginal infectious diseases; thus, they are unable to make better decisions about contraception methods. Nearly half of participants with college or higher education used a condom for sex; in contrast, only 16% of women with lower education used condoms. Thus, further efforts to improve educational levels are needed to prevent T. vaginalis infection in the Tibetan area.
Family income was strongly associated with the likelihood of T. vaginalis infection in our study. Cases were more prevalent among females with family income below the average level, which is the same as prior reports in the US and southern Brazil (Gatti et al. 2017; Patel et al. 2018). In accordance with the WHO, women in low-income countries undertake a greater burden of T. vaginalis infection (Organization 2013). For one thing, lower income in many cases means lower educational attainment, the evidence of which was a smaller proportion (15.40%) of women with lower income received a college education compared to women with higher family income (P < 0.01). Another reason for this is poor access to health care in low-income women, which leads to a higher risk of transmission of T. vaginalis. Thus, more interventions for improving living standards should be targeted to this population.
Using a condom for sex was a protective factor against T. vaginalis infection, as Barbosa et al. found (Barbosa et al. 2020). In this study, women who did not use condoms for sex were twice as likely to be T. vaginalis positive as women who did. The marked disparity is due to asymptomatic sex partners. Without awareness of infection, asymptomatic sex partners readily transmit T. vaginalis to women during penile-vaginal sexual encounters. Additionally, our study indicated that no sex may reduce the risk of T. vaginalis infection, which is closely related to reducing the probability of transmission via sexual contact. These results highlight that consistent and correct condom use can prevent the transmission of T. vaginalis by providing an effective barrier against pathogens (Wan Muda et al. 2018).
The proportion of asymptomatic carriers of T. vaginalis should not be overlooked. Our study found that only 15.30% of T. vaginalis-positive women were asymptomatic, compared with nearly 80%, a universally recognized level (Workowski and Bolan 2015). A greater percentage of T. vaginalis-positive women came to this hospital because they had related uncomfortable symptoms. This is problematic since some women in this area have no awareness of having regular gynecological examinations unless symptoms appear. Hence, general surveillance for sexually transmitted diseases, an effective way to prevent T. vaginalis infection, is needed.
The major strength of this study was the high rate of testing T. vaginalis infection and a real-life condition in the process of diagnosis in the hospital. Moreover, the characteristics of the population enrolled in this study have rarely been studied before. The limitation of the study was obvious. This study recruited only participants who just wanted to seek medical care or had access to medical care of this hospital or had associated symptoms; thus, the limit affected the generalizability and led to selection bias. For measurement bias, our subsequent studies should introduce more sensitive tests and biochemical indicators based on direct microscopy to improve the sensitivity.
On the basis of this study, we conclude that the prevalence of T. vaginalis infection is estimated to be 20.94% among women treated in the hospital of Shannan city during this period. Associated risk factors include lower educational status and family income, higher sexual frequency, nonuse of condoms, clinical symptoms and a high level of vaginal cleanliness. Our results have improved our understanding of the prevention of T. vaginalis in the Tibetan area. To effectively reduce the occurrence of T. vaginalis infection in this area, adopted measures depended on different customs and demographic characteristics, including raising the standard of living as well as women's educational level and promoting reproductive hygiene habits.