Introduction
The WHO published a road map for control and elimination of neglected tropical diseases (NTDs) 2021–2030 of which one of their public health targets is specific for schistosomiasis (WHO, 2022). Despite being targeted for elimination as a public health problem, schistosomiasis is one of the NTDs that continue to affect millions of people, particularly in resource-limited regions of the world (McManus et al. Reference McManus, Dunne, Sacko, Utzinger, Vennervald and Zhou2018; Buonfrate et al. Reference Buonfrate, Ferrari, Adegnika, Stothard and Gobbi2025). Despite being a major public health issue in many tropical and subtropical countries, schistosomiasis has often been overlooked in global health discussions and funding priorities. In sub-Saharan Africa (SSA), male genital schistosomiasis (MGS), a gender-specific manifestation of urogenital schistosomiasis in men, has a long history of being an under-recognized and under-reported largely due to limited awareness and access to diagnostic tools, particularly resource poor rural areas where urogenital schistosomiasis is endemic (Bustinduy et al. Reference Bustinduy, Randriansolo, Sturt, Kayuni, Leutscher, Webster, Van Lieshout, Stothard, Feldmeier and Gyapong2022). This is in contrast with female genital schistosomiasis (FGS) which has been widely studied, diagnostic, management and control strategies developed and advocated (WHO, 2015).
The condition, MGS, was first described in 1911 (Madden, Reference Madden1911), though it likely existed much earlier in SSA and the Middle East regions, where Schistosoma haematobium was prevalent (Kayuni et al. Reference Kayuni, Lampiao, Makaula, Juziwelo, Lacourse, Reinhard-Rupp, Leutscher and Stothard2019a). Men infected after exposure to schistosome cercariae-infested water bodies were observed to have genital lesions, including fibrosis in scrotum, prostate and seminal vesicles, testicular atrophy, and even infertility due to inflammatory response to tissue eggs deposition (Costain et al. Reference Costain, MacDonald and Smits2018).
In recent years, it has been demonstrated that S. haematobium has an innate capacity to form viable hybrids with other schistosome species, particularly with Schistosoma mattheei, a common species of animal schistosome found in livestock (Stothard et al. Reference Stothard, Kayuni, Al-Harbi, Musaya and Webster2020, Reference Stothard, Juhász and Musaya2024). Hybridization is a well-established evolutionary mechanism that contributes to genetic diversity, allowing species to adapt more quickly to environmental changes (Mawa et al. Reference Mawa, Kincaid-Smith, Tukahebwa, Webster and Wilson2021). In light of the future challenge to interrupt schistosome transmission, there is growing interest in hybrid schistosomes, and their environmental dynamics, resulting from crossbreeding between zoonotic and human Schistosoma species. Furthermore, such introgressed or hybrid variants can potentially complicate the clinical picture of urogenital schistosomiasis and how the parasite is evolving and adapting to different hosts (Rey et al. Reference Rey, Toulza, Chaparro, Allienne, Kincaid-Smith, Mathieu-Begné, Allan, Rollinson, Webster and Boissier2021; Kayuni et al. Reference Kayuni, Musaya and Stothard2024b).
Certainly, zoonotic schistosomes have contributed significantly to the overall burden of schistosomiasis in humans, with some causing fibrosis and calcification in prostate, seminal vesicles and testes (Buonfrate et al. Reference Buonfrate, Ferrari, Adegnika, Stothard and Gobbi2025; Léger et al. Reference Léger, Borlase, Fall, Diouf, Diop, Yasenev, Catalano, Thiam, Ndiaye and Morrell2020). Advancements in molecular biology significantly improved modern diagnostic tools for schistosomiasis, including MGS where detection of Schistosoma eggs, DNA and antigens can be made directly from semen, prostate biopsies, and other tissue samples, offering more precise and reliable diagnosis (Cunningham et al. Reference Cunningham, Kayuni, Juhász, Makaula, Lally, Namacha, Kapira, Chammudzi, Mainga and Jones2024, Rinaldi et al. Reference Rinaldi, Young, Honeycutt, Brindley, Gasser and Hsieh2015).
Following a baseline MGS survey within the longitudinal study entitled Hybridization of UroGenital Schistosomiasis (HUGS) in Mangochi and Nsanje districts, Southern Malawi (Kayuni et al. Reference Kayuni, Cunningham, Mainga, Kumwenda, Jnr, Chammudzi, Kapira, Namacha, Chisale and Nchembe2024a), a clinical 12-month follow-up was conducted on participating men to describe progression of schistosome infections either from human, zoonotic and hybrid worms undertaken between June 2023 and July 2024.
Materials and methods
Study sites
This MGS longitudinal study was conducted in the two sentinel communities at Samama and at Mthawira in Mangochi and Nsanje Districts, respectively (Figure 1). Here, hybrid infections have previously been identified in school children in these communities, with a tenth of infected children shedding atypical eggs in urine, alongside ectopic egg patent S. mansoni and zoonotic eggs, at the baseline of the HUGS study in 2022.
Figure 1. Map showing two study communities around Samama School in Mangochi District and Mthawira School in Nsanje District of Southern Malawi where participates came from.
Study population
The study population comprised of all males aged between 18 and 45 years old who had active egg-patent schistosomiasis at baseline in 2022 in the two study sites of Samama and Mthawira areas. These were recruited as at baseline of the MGS study in June and July 2023 and underwent a 6- and 12-month follow-up. Written informed consent was sought after adequate awareness before enrolment into the study. All participants were provided a directly observed treatment with praziquantel standard dose, 40 mg/kg body weight, at the end of each study visit.
Data collection
Demographic data were gathered through individual questionnaire interviews to collect details on participants’ health, socio-economic status, water contact habits, livestock availability and symptoms associated with MGS (Kayuni et al. Reference Kayuni, Cunningham, Mainga, Kumwenda, Jnr, Chammudzi, Kapira, Namacha, Chisale and Nchembe2024a).
Urine and semen microscopy
A 120 mL clear container was used to collect a urine sample during the study visit, which was then filtered and examined microscopically to detect Schistosoma eggs in 10 mL of the well-mixed sample (Cheesbrough, Reference Cheesbrough2005). Additionally, each sample underwent reagent dipstick testing and point-of-care circulating cathodic antigen (POC-CCA) analysis for detection of intestinal schistosomiasis. Participants were then requested to provide a semen sample, which was collected in a clear plastic bag for direct field microscopy (Kayuni et al. Reference Kayuni, Plam, LaCourse, Bartlett, Fawcett, Shaw, Makaula, Lampiao, Juziwelo, de Dood, Hoekstra, Verweij, Leutscher, van Dam, van Lieshout and Stothard2019b). The samples were subsequently centrifuged, and the sediments were re-examined microscopically. These sediments were preserved in 1 mL of 70% ethanol to prepare for shipment to Liverpool School of Tropical Medicine (LSTM) in the United Kingdom.
Molecular analyses
As previously described (Cunningham et al. Reference Cunningham, Kayuni, Juhász, Makaula, Lally, Namacha, Kapira, Chammudzi, Mainga and Jones2024; Kayuni et al. Reference Kayuni, Cunningham, Mainga, Kumwenda, Jnr, Chammudzi, Kapira, Namacha, Chisale and Nchembe2024a), molecular analysis of the semen sediments included High-Resolution Melt (HRM) and TaqMan® real-time PCR for Schistosoma spp. DNA markers for viral infection with HPV were also screened for using the QIAscreen HPV PCR Test kit (Qiagen, Manchester, UK), capable of screening for two high-risk genotypes, 16 and 18 alongside the others. Also, seminal sediments were analysed for other STIs such as Chlamydia trachomatis, Trichomonas vaginalis, Herpes simplex virus (HSV) 1, HSV 2, Candida spp., Ureaplasma spp., M. hominis, S. agalactiae using the EasyScreen™ STI Kit (SydPath, Sydney, Australia).
Data analyses
The results of the diagnostic tests were analysed using non-parametric tests due to the small sample size and non-normal distribution. These were tabulated and presented accordingly.
Ethical considerations
Ethical approval for the study was granted by the College of Medicine Research Ethics Committee (COMREC), Kamuzu University of Health Sciences (KUHeS), Malawi, (Approval number: P.08/21/3381) and the LSTM Research Ethics Committee (LSTM REC) in the United Kingdom (registration number: 22-028). Informed consent to participate in the study was obtained from all of the participants. Privacy and confidentiality were maintained throughout the study. All participants including those who had Schistosoma eggs in urine and/or semen were provided a directly observed treatment with praziquantel standard dose, 40 mg/kg body weight, at each time point. Appropriate referral for treatment and management was provided to participants who had other infections.
Results
Of the 22 male participants recruited into the MGS sub-study at baseline in June 2023, 19 (7 in Nsanje, 12 in Mangochi) and 14 (3 in Nsanje, 11 in Mangochi) participants were available for follow-up at 6- and 12-month time points, respectively (Table 1).
Table 1. Demographical information and laboratory findings of the participants at all the time points
Note: S. h. = Schistosoma haematobium, S. matt. = Schistosoma mattheei, N/A = not available.
Three participants (J, L and O) reported symptoms associated with MGS at baseline, namely blood in semen (haemospermia), sores and pain in the genitalia, pain during coitus and ejaculation (Table 2). Only one participant (J) with symptoms had Schistosoma eggs in their urine and semen. At 6-month follow-up, 10 participants reported MGS symptoms while 7 participants reported the symptoms at 12-month follow-up time point.
Table 2. Symptoms of MGS experienced by the participants at all the time points
Note: Within the table: red colour = symptom experienced, 1 = Schistosoma eggs in urine or semen, 0 = no Schistosoma eggs in urine or semen, N/A = urine or semen sample not available for analysis.
Five of the 10 participants who had Schistosoma eggs in their urine at baseline, remained egg-patent at 6-month follow-up, with 4 participants (E, L, R and T) who were urinary egg-patent for the first time, giving a prevalence of 47·4% (n = 19). At 12-month follow-up, 7 out of the 10 participants with Schistosoma eggs in their urine at baseline were present and participant J was urinary egg-patent at baseline and this time point while participant M was infected at all 3 time points. In total, 4 (J, L, M and P) had eggs in their urine (28·6%, n = 14) at this time point (Figure 2).
Figure 2. Map showing findings of semen microscopy of the study participants alongside those of urine filtration in the 2 communities around Samama school in Mangochi district and Mthawira school in Nsanje district of Southern Malawi where participants came from.
On semen microscopy, 10 out of 11 participants with S. haematobium eggs at baseline had persistent infection at 6-month follow-up, together with 6 participants who had eggs in their semen for the first time, showing a higher infection rate of 84·2% (n = 19). Two participants, G and M, also had S. mattheei eggs in semen.
Of the 13 participants who were available at 12-month follow-up, only 4 (A, D, G and M) had S. haematobium eggs in their semen which were persistent at all the time points, with 1 (participant G) having persistent S. mattheei eggs from 6-month follow-up, depicting a dual human and zoonotic infection at both time points. Two participants (A and D) had calcified S. haematobium eggs at this time point.
Only 1 of the 3 participants, D, who had changes in his semen observed at baseline, had normal features at subsequent follow-up time points. However, 4 additional participants (E, G, L and S) who also had Schistosoma eggs in their semen were observed to have abnormal changes ranging from loose semen consistency, few live or dead spermatozoa to azoospermia at 6- and 12-month time points.
Using real time PCR at 6-month follow-up, 14 of the 19 participants (73·7%) were positive for Schistosoma infection, with only 2 participants (E and R) who were infected for first time at this time point (Table 3 and Supplementary Table 1). Three participants had a possible hybrid infection at this time point. On 12-month follow-up, only 6 out of 13 participants had positive Schistosoma infection with no possible hybrid infection. All in all, only 6 of all recruited participants (B, C, F, L, P and S) had no positive Schistosoma infection on PCR at the end of the study.
Table 3. Results of molecular analysis on Schistosoma infection using real-time PCR of the participants’ semen
Note: Gen = generic, Mito = mitochondrial, HRM = high-resolution melt, Tm = melting temperature, N/A = not available; Sh = Schistosoma haematobium, Sm = Schistosoma mansoni, Smat = Schistosoma mattheei, Sc = Schistosoma curassoni, Shyp = Schistosoma hybrid, 0·0 = no Schistosoma detected; colours: dark blue = Schistosoma haematobium; plum = Schistosoma mansoni; dark green = Schistosoma mattheei; orange = Schistosoma curassoni; red = Schistosoma hybrid.
Of those participants who had Schistosoma eggs in semen during the study, 4 had none in urine (D, F, G and S). Furthermore, participants Q and T had no eggs in urine nor semen, also with negative PCR.
All the 12 (54·5%) participants who had detectable HPV serotypes 16 and 18 in semen, associated with penile and cervical carcinoma at baseline, had no HPV detected during follow-up at both time points (Table 4 and Supplementary Table 2). On STIs, particularly T. vaginalis, only one participant was positive at 6-month follow-up and none at 12-month follow-up, showing a downward trend of both infections.
Table 4. Results of the real time PCR for Human Papilloma Virus (HPV) serotypes and STIs – Trichomonas vaginalis in comparison with and Schistosoma species
Note: Gen = generic, HRM = high-resolution melt, Tm = melting temperature, Tv = T. vaginalis; N/A = not available, Sh = Schistosoma haematobium, Sm = Schistosoma mansoni, Smat = Schistosoma mattheei, Sc = Schistosoma curassoni, Shyp = Schistosoma hybrid, 0·0 = no Schistosoma detected; colours: dark blue = Schistosoma haematobium; plum = Schistosoma mansoni; dark green = Schistosoma mattheei; orange = Schistosoma curassoni; red = Schistosoma hybrid; yellow = HPV serotypes 16 or 18 or others; purple = T. vaginalis.
Discussion
As described previously, here in these 2 southern communities of Malawi, MGS remains a seldomly recognised, undiagnosed condition in endemic areas, where it is as commonly prevalent as urogenital schistosomiasis, and with coinfection signatures with S. mattheei (Kayuni et al. Reference Kayuni, Cunningham, Mainga, Kumwenda, Jnr, Chammudzi, Kapira, Namacha, Chisale and Nchembe2024a). This study is a 12-month follow-up to our initial study comprising a cohort of 22 men where Schistosoma eggs was detected in semen of 11 men (50·0%) with 16 men (72·7%) positive on real-time PCR for Schistosoma infection, conducted at 2 time points of 6 months each. It was noted that despite taking a directly observed standard dose of praziquantel treatment, 40 mg/kg body weight, some participants had persistent or possible re-infections.
An important observation is that four participants had Schistosoma eggs only in semen during the study, which is consistent with similar studies, showing that the individuals can have MGS due to worms inhabiting the blood vessels around the genital organs, rather than contamination of the urethra from urinary schistosomiasis (Kayuni et al. Reference Kayuni, Lampiao, Makaula, Juziwelo, Lacourse, Reinhard-Rupp, Leutscher and Stothard2019a, Reference Kayuni, Alharbi, Makaula, Lampiao, Juziwelo, LaCourse and Stothard2021; Bustinduy et al. Reference Bustinduy, Randriansolo, Sturt, Kayuni, Leutscher, Webster, Van Lieshout, Stothard, Feldmeier and Gyapong2022). Hence, the critical importance of analysing semen samples as a way of diagnosing MGS.
Previous reports on MGS associated with non-human schistosomes have been inadequate and mostly case reports of people visiting to endemic areas, despite studies done in Malawi and Madagascar describing significant burden of MGS (Leutscher et al. Reference Leutscher, Ramarokoto, Reimert, Feldmeier, Esterre and Vennervald2000; Kayuni et al. Reference Kayuni, Alharbi, Makaula, Lampiao, Juziwelo, LaCourse and Stothard2021, Reference Kayuni, Alharbi, Shaw, Fawcett, Makaula, Lampiao, Juziwelo, LaCourse, Verweij and Stothard2023a). Furthermore, the extent of the morbidity resulting from these zoonotic and hybrid MGS infections remains poorly understood although these schistosomes in SSA are increasingly becoming recognized as an emerging public health problem (Webster et al. Reference Webster, Alharbi, Kayuni, Makaula, Halstead, Christiansen, Juziwelo, Stanton, LaCourse, Rollinson, Kalua and Stothard2019; Stothard et al. Reference Stothard, Kayuni, Al-Harbi, Musaya and Webster2020) and future challenge in gaining adequate environmental transmission control (Stothard et al. Reference Stothard, Juhász and Musaya2024).
The proximity of most study participants to domesticated livestock such as goats, sheep and cattle in the study area which have shown to harbour both human and zoonotic mixed infections (Juhász et al. Reference Juhász, Makaula, Cunningham, Field, Jones, Archer, Mainga, Lally, Namacha and Kapira2024a, Reference Juhász, Makaula, Cunningham, Jones, Archer, Lally, Namacha, Kapira, Chammudzi, LaCourse, Seto, Kayuni, Musaya and Stothard2024b) could have significantly contributed to the level of MGS. Certainly, some participants were observed to have hybrid infections during the follow-up using our novel two-tube real-time PCR (Cunningham et al. Reference Cunningham, Kayuni, Juhász, Makaula, Lally, Namacha, Kapira, Chammudzi, Mainga and Jones2024), which brings about the need for advanced molecular diagnostics to improve detection of such diseases. Furthermore, one health initiatives can aid in addressing the emerging zoonotic and hybrid infections which is being worsened with adverse climate change, thereby affecting efforts in the control and elimination of schistosomiasis as public health problem in endemic areas (Mbabazi et al. Reference Mbabazi, Andan, Fitzgerald, Chitsulo, Engels and Downs2011; Shukla et al. Reference Shukla, Kleppa, Holmen, Ndhlovu, Mtshali, Sebitloane, Vennervald, Gundersen, Taylor and Kjetland2023).
Although some participants had changes in their semen, namely haemospermia, changes in semen colour and consistency and azoospermia which have also been reported in other studies, only one had resolved these abnormalities during follow-up. This highlights the need for earlier treatment with praziquantel to experience its beneficial effects, apart from other interventions to prevent such infections as well as improving diagnostic services, healthcare professional awareness and capacity in disease management (Mbabazi et al. Reference Mbabazi, Andan, Fitzgerald, Chitsulo, Engels and Downs2011; Shukla et al. Reference Shukla, Kleppa, Holmen, Ndhlovu, Mtshali, Sebitloane, Vennervald, Gundersen, Taylor and Kjetland2023).
Certainly, most health facilities in the endemic areas use the syndromic approach in the STI management (WHO 2005, 2021). These genital symptoms utilized are similar to those attributed to MGS, also observed in our study, which can result in under-diagnosis and inappropriate management. Also, MGS has been observed to play a role in the progression of other infections such as human immunodeficiency virus (HIV) among other factors, as previously observed in increasing seminal viral load of dually infected men (Midzi et al. Reference Midzi, Mduluza, Mudenge, Foldager and Leutscher2017; Kayuni et al. Reference Kayuni, Abdullahi, Alharbi, Makaula, Lampiao, Juziwelo, LaCourse, Kumwenda, Leutscher and Geretti2023b). Therefore, there is need for more advocacy for appropriate diagnostic and management resources together with awareness and capacity building among community people and healthcare providers in schistosomiasis-endemic areas.
As earlier alluded to, the study was limited in the low number of study participants owing to the sensitivity of the condition which calls for larger stratified studies in other endemic areas to provide a representative picture of the MGS outcome.
Conclusion
Human, zoonotic and hybrid schistosomes continues to being incriminated in causing MGS significantly, hence posing a One Health challenge in management and control measures in resource poor settings. This calls for more tailored public health education campaigns in the endemic communities, awareness of MGS among primary healthcare workers and local animal health experts and collaborations among these stakeholders and National Schistosomiasis Control Programme in handling this burden and address it adequately.
Supplementary material
The supplementary material for this article can be found at https://doi.org/10.1017/S0031182025100942.
Data availability statement
The datasets generated and analysed for this study has been included in this manuscript.
Acknowledgements
The study team acknowledge the generous support rendered by the Directors of Health and Social Services, District Medical Officers, District Environmental and Assistant Environmental Health Officers, District Laboratory Managers, Schistosomiasis Coordinators, Management and staff of Nsanje and Mangochi District Health Offices; the In-charges and Nurse-Midwives of Tengani and Mpondasi Health Centres; the Headteachers and teachers of Mthawira and Samama Primary Schools; and the study participants who took part in the HUGS Human longitudinal study, especially MGS sub-study. Much appreciation to Professor John Ellis at University of Sydney, Australia for testing STIs on the semen samples using their EasyScreen™ kit (SydPath, Sydney, Australia). Also grateful to the local community health workers: Abdul Salimu, Bossman Kutama, Christopher Thonje, Cynthia Issah, Grace Nyakamera, Harrison Makawa, Rester Fellow, Theresa Masauli, Witness Mapila, Angellina Mwenyewe, Flora Majawa, Caroline Mnthubula, Alice Kasonde, Doreen Chitsulo; and all traditional leaders and community members around Mthawira and Samama schools for their enthusiasm and support.
Author contributions
The authors contributed to this work as follows: SK, JM and JRS conceived and designed the study. SK, BM, FA, GD, DK1, AC, TN, DL, PC, DK2, GN, LK, EC, BN, GC, WK, HC, VK, AJ, SJ, JA, AOF, SR, AC, RC, LC, JC, PM, EJL, JM and JRS conducted data gathering. SK, BM, FA and LC performed statistical analyses. SK, BM, FA, GD, DK1, AC, TN, DL, PC, DK2, GN, LK, EC, BN, GC, WK, HC, VK, AJ, SJ, JA, AOF, SR, AC, RC, LC, JC, PM, EJL, JM and JRS wrote the article.
Financial support
This research received funding from National Institute for Health Research (NIHR) and Wellcome Trust through a Joint Investigator Award, grant number WT 220818/Z/20/Z.
Competing interests
The authors declare there are no conflicts of interest. The funders had no role in the design of the study, data gathering, statistical analyses and writing of the manuscript.
Ethical standards
The study was conducted in accordance with the Declaration of Helsinki and approved by the College of Medicine Research Ethics Committee (COMREC) of Kamuzu University of Health Sciences (KUHeS) in Malawi (approval number: P.08/21/3381) and LSTM Research Ethics Committee (LSTM REC) in the United Kingdom (approval number: 22-028). Informed consent to participate in the study was obtained from all of the participants.
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