Forgotten but not gone in rural South Africa: Urinary schistosomiasis and implications for chronic kidney disease screening in endemic countries

Abstract

Background: Urinary schistosomiasis caused by infection with Schistosoma haematobium (S. haematobium) remains endemic in Africa and is associated with haematuria and albuminuria/proteinuria. Kidney Disease Improving Global Outcomes clinical guidelines recommend evaluating proteinuria/albuminuria and glomerular filtration rate for chronic kidney disease (CKD) diagnosis. The guidelines are informed by population data outside of Africa but have been adopted in many African countries with little validation. Our study aimed to characterise the burden of urinary schistosomiasis in rural South Africa (SA) and evaluate its relationship with markers of kidney dysfunction with implications for CKD screening. Methods: In this population-based cohort study, we recruited 2021 adults aged 20 – 79 years in the Mpumalanga Province, SA. Sociodemographic data were recorded, urinalysis performed, and serum creatinine and urine albumin and creatinine measured. Kidney dysfunction was defined as an estimated glomerular filtration rate (eGFR) <60ml/min/1.73m2 and/or urine albumin-creatinine ratio >3.0mg/mmol. S. haematobium infection was determined by urine microscopy. Multivariable analyses were performed to determine relationships between S. haematobium and markers of kidney dysfunction. Results: Data were available for 1226 of 2021 participants. 717 (58.5%) were female and the median age was 35 years (IQR 27 – 47). Prevalence of kidney dysfunction and S. haematobium was 20.2% and 5.1% respectively. S. haematobium was strongly associated with kidney dysfunction (OR 8.66; 95% CI 4.10 – 18.3) and related to albuminuria alone (OR 8.69; 95% CI 4.11 – 18.8), with no evidence of an association with eGFR <90ml/min/1.73m2 (OR 0.43; 95% CI 0.05 – 3.59). Discussion: The strong association between urinary schistosomiasis and albuminuria requires careful consideration when screening for CKD. Screening for, and treatment of, schistosomiasis should be a routine part of initial work-up for CKD in S. haematobium endemic areas. Urinary schistosomiasis, a neglected tropical disease, remains a public health concern in the Mpumulanga province of SA.

Chronic kidney disease of unknown aetiology in Africa: A review of the literature

“…Exposure to infectious diseases, such as schistosomiasis, tuberculosis, malaria, hepatitis B and C viruses represent an almost unique cluster of risk factors responsible for CKD in the African population 54,61,65 . In a more recent population‐based study in rural South Africa, schistosomiasis infection was associated with 8.7‐fold risk of CKD 66 . In a study from Tanzania, history of tuberculosis and schistosomiasis infection were, respectively, associated with an up to 3.8 and 2.5‐fold higher risk of CKD, accounting for 22% of the CKD burden 46 .…”

“…54,61,65 In a more recent population-based study in rural South Africa, schistosomiasis infection was associated with 8.7-fold risk of CKD. 66 In a study from Tanzania, history of tuberculosis and schistosomiasis infection were, respectively, associated with an up to 3.8 and 2.5-fold higher risk of CKD, accounting for 22% of the CKD burden. 46 A study from Zimbabwe also reported tuberculosis, history of schistosomiasis infection and malaria as the aetiological conditions of CKD patients.…”

Proteomic insights into the pathophysiology of hypertension-associated albuminuria: Pilot study in a South African cohort

“…Approximately 20-30 ml urine was collected from ARK study participants. Urine samples were processed and stored at -80°C prior to shipping to the Council for Scientific and Industrial Research laboratory for proteomic testing (30). Serum and urine creatinine was measured using an isotope dilution mass spectrometry traceable Jaffe method (31).…”

“…Urine samples were processed and stored at -80°C prior to shipping to the Council for Scientific and Industrial Research laboratory for proteomic testing (30). Serum and urine creatinine was measured using an isotope dilution mass spectrometry traceable Jaffe method (31). The 2009 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation without adjustment for African American ethnicity was used to calculate eGFR (ml/min/1.73 m 2 ) (32).…”

“…The 2009 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation without adjustment for African American ethnicity was used to calculate eGFR (ml/min/1.73 m 2 ) (32). Immunoturbidimetry was used to measure urine albumin concentration (31). The UACR was calculated (mg/mmol) based on this measurement (31).…”