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PRE-RECORDED: TARGETS FOR ELIMINATION AS A PUBLIC HEALTH PROBLEM FAIL TO DIFFERENTIATE SCHISTOSOMIASIS MORBIDITY PREVALENCE IN SCHOOL-AGE CHILDREN (ID 1887)
The World Health Organization’s framework for the assessment of schistosomiasis morbidity control utilizes the prevalence of heavy intensity infections (PHI) and defines < 1% PHI as having eliminated schistosomiasis as a public health problem (EPHP). Research has found that a higher proportion of the schistosomiasis morbidity burden is due to light and moderate infections rather than heavy intensity infections. The objectives of these analyses were to improve the schistosomiasis monitoring and evaluation framework by evaluating whether current PHI-based EPHP targets are linked to morbidity indicators and calculate infection prevalence targets linked to morbidity. Utilizing data collected in the national control programs for schistosomiasis and soil-transmitted helminthiasis in Burkina Faso, Mali, Niger, Tanzania, Uganda, and Zambia between 2003-2008, analyses found that S. haematobium PHI was only associated with microhaematuria prevalence, but EPHP targets provided minimal utility. Infection prevalence had much greater utility and targets of 5%, 8%, and 11% would be expected to keep microhaematuria prevalence below 10%, 13%, and 15%, respectively. No robust targets for S. mansoni infection prevalence could be found. PHI-based targets are inadequate to evaluate EPHP and new infection prevalence targets should be developed. S. mansoni morbidity control may require changes to accurately evaluate EPHP.
SCHISTOSOMIASIS INDUCES PLASMA B CELL DEATH IN THE BONE MARROW AND ACCELERATES THE DECLINE OVER TIME OF HOST VACCINE RESPONSES (ID 1888)
Schistosomiasis is a debilitating parasitic disease that is most common in Sub-Saharan Africa. The disease has previously been shown to influence systemic immunity towards unrelated antigens such as vaccines. However, mechanisms behind the parasite’s impact on vaccine mounted long-term immunity are not fully understood. We investigated the impact of chronic Schistosoma mansoni infection on the efficacy of vaccine-induced immunity in school-aged Cameroonian children and laboratory mice. Our findings highlighted impaired maintenance of long-term anti-polio vaccine-specific serological immunity in both vaccinated children and mice. Using a mouse model of anti-viral vaccination, additional mechanistic evaluations demonstrated that chronic schistosomiasis caused vaccine-elicited immunity impairment through reduced survival of plasmablasts and antibody-producing plasma B cells in the bone marrow. Treatment with praziquantel partially reversed the impact of chronic schistosomiasis on serological immunity of both vaccinated children and mice, and plasma B cell populations in the bone marrow of mice. Our results, therefore, demonstrate the morbid impact and a potential mechanism thereof, of chronic schistosomiasis on immunological responses induced by anti-viral vaccination. Further, this study presents praziquantel treatment as a potential strategic tool to improve vaccination effectiveness through ameliorated sustainability post-vaccination in at-risk population groups in schistosomiasis endemic regions. These findings are timely for the informed rollout of antiviral COVID-19 vaccines in Schistosomiasis-infested countries.
SELF-SAMPLING MOLECULAR APPROACHES FOR SCREENING FEMALE GENITAL SCHISTOSOMIASIS AND CERVICAL CANCER (ID 1889)
It is estimated that around 40 million women living in Sub-Saharan Africa (SSA) are affected by female genital schistosomiasis (FGS), a chronic gynaecological disease caused by the waterborne parasite, Schistosoma haematobium (Sh). FGS is associated with infertility, dyspareunia and symptoms mimicking sexually transmitted infections. Awareness of the disease is largely absent despite growing evidence of increased prevalence of HIV and suggestion of increased cervical dysplasia, the precursor of cervical cancer (CC). Conventional FGS diagnosis is challenging, as it relies on costly equipment and high-level specialised training seldom available in resource-limited countries.
Genital self-sampling for the diagnosis of female genital schistosomiasis (FGS) was a novel strategy piloted in 2018 (BILHIV study) in Zambia. Parasite DNA detection from self-sampling strategies was comparable to clinician obtained. Samples were processed by conventional PCR and field-deployable isothermal assay (RPA) with excellent concordance. Self-sampling strategies have been validated for the detection of oncogenic human papillomavirus (HPV) genotypes, etiological agents of CC. HPV point-of-care diagnostic tests are commercially available. Genital self-swabs are well accepted by participants and increase compliance across settings.
The ongoing Zipime Schista Study! In Zambia is a longitudinal cohort study aiming to include multiple-pathogen screening through genital self-sampling (Sh, HPV) and offering self-testing for HIV and STIs. This strategy is coupled with novel molecular assays that are field deployable and can provide a scalable cost-effective strategy. The design and preliminary results of the study will be presented.
MORBIDITIES ASSOCIATED WITH HYBRID INFECTIONS IN CHILDREN ALONG SOUTH LAKE MALAWI (ID 1890)
The discovery of Schistosoma hybrids in Mangochi and Nsanje had brought a new dimension of biology of schistosomiasis in Malawi. We believe Schistosoma haematobium-hybrids are able to be maintained in environmental transmission through livestock and still infect people and cause disease. The clinical picture of hybrids is humans is not understood and it underpins the course of schistosomiasis control interventions. We have embarked on a study to assess the prevalence of hybrids in the communities in Mangochi and Nsanje districts and to ascertain if there is any increased host morbidity in hybrids or co-infected individuals with a mirrored picture in cattle samples. We are collecting urine, stool and blood samples from 1200 consented participants from each district aged from 2 to 45 years of age. The Urine and stool are inspected for eggs and isolated eggs on FTA card are extracted for ITS PCR and DNA sequencing of cox1 and 18S and ITS regions capable of detecting hybrids. While the blood sample is assessed for anemia and inflammation associated with schistosomiasis, suspected individuals with hybrid infection receive ultrasonography assessment. We will present our preliminary results from human and animal which so far is showing presents of possible hybrids. A possible 22% suspected hybrids in cattle has already been analyzed. We hope our data will add to the understanding of the pathology associated of schistosomiasis in Malawi and the region.