Category Archives: Schistosomiasis

Identifying a More Accurate Test for Schistosomiasis in The Gambia

During the recently concluded 65th Annual Meeting of the American Society of Tropical Meicine and Hygiene colleagues from The Gambian Ministry of Health and Social Welfare, the World Health Organization and the NTD Support Center presented a poster entitled, “Field Performance of a Circulating Cathodic Antigen Rapid Test at Point-Of-Care for Mapping Schistosomiasis-Endemic Districts in Gambia.” The authors included Bakary Sanneh, Kristen Renneker, Joof  Ebrima, Sanyang M. Abdoulie, Camara Yaya, Sambou M. Sana, Sey Alhagie Papa, Jagne Sherifo, Baldeh Ignacious, Louis-Albert Tchuem Tchuente, Patrick J Lammie, and Kisito Ogoussan. Their abstract appears below.

figureBackground: The traditional parasitological Kato Katz smears and urine filtration methods recommended by the World Health Organization (WHO) to implement mapping of schistosomiasis have been found to be less sensitive in the detection of light-intensity schistosomiasis infections. Field surveys in Sub-Sahara Africa have shown that the Circulating Cathodic Antigen (CCA) point-of-care (POC) test is more accurate for detecting Schistosoma mansonia than the microscopic Kato Katz technique.

Aim: To establish the field sensitivity and specificity of POC CCA as mapping tool to provide the endemicity of schistosomiasis in The Gambia.

Methods: A cross-section study …

  • Ten school per region in 4 regions with historical known risk
  • Fifty children aged 7 to 14 years: 25 boys and 25 girls (WHO Mapping sampling guide)
  • Stool, urine and finger pricks samples were examined for Schistosomiasis
  • Parasitological tests: 2 Kato-katz slides to read from each stool sample, and urine filtration technique, urine dip-stick and Circulating Cathodic Antigen (CCA) techniques,

table-1Discussion: The CCA prevalence in this study was 23.34% (95% CI, 21.51-25.26%) two times higher than the prevalence based on  egg-detection for S. haematobium and S.mansoni (10.13,95% CI 8.87-11.55; and 0.26%, (95% CI, 0.09-0.62, respectively).  Although The Gambia is thought to be endemic for only S. haematobium, yet 5 subjects were found to harbor S. mansoni. Three of the 5 individuals from the high endemic schistosomiasis regions were co-infected with S. haematobium and S. mansoni.

table-2The sensitivity of the POC-CCA proved to be relatively high (60.0%), using double Kato-Katz as a reference for S. mansoni detection, although few infections were found, 5 out 1954  tested. The specificity of the POC CCA was 76.8%, respectively.  Using urine filtration as reference standard for the detection of S. haematobium, the sensitivity of POC-CCA was 47.9% and the specificity was 79.4%.

Conclusion: The Gambia is endemic for both urinary and intestinal schistosomiasis although most of the infections are due to S. haematobium in the 4 regions investigated. The results of the study showed a low sensitivity of the POC-CCA test in detecting S. haematobium and therefore we conclude further research is needed  to develop an ideal rapid diagnosis tool for urinary schistosomiasis.

schisto-acknowledgementAcknowledgement: Thanks to the Mapping Team,  Consultants, MoHSW, WHO,  Task Force for Global Health (TFGH) for all their support. For questions please contact: Dr. Kisito Ogoussan, kogoussan@taskforce.org; or Mr. Bakary Sanneh, sheikbakary@yahoo.com