Malaria prevalence and performance of diagnostic tests among patients hospitalized with acute undifferentiated fever in Zanzibar

• Published in: Malaria Journal
• Main Authors: Annette Onken, Christel Gill Haanshuus, Mohammed Khamis Miraji, Msafiri Marijani, Kibwana Omar Kibwana, Khamis Ali Abeid, Kristine Mørch, Marianne Reimers, Nina Langeland, Fredrik Müller, Pål A. Jenum, Bjørn Blomberg
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2022
• Subjects: Malaria; Prevalence; Surveillance; Fever; Microscopy; Point-of-care diagnostic tests; Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Arctic
• Online Access: https://doi.org/10.1186/s12936-022-04067-z; https://doaj.org/article/601328fb02ba460fa773e0fc2ec32851

Abstract Background Control efforts in Zanzibar reduced the burden of malaria substantially from 2000 to 2015, but re-emergence of falciparum malaria has been observed lately. This study evaluated the prevalence of malaria and performance of routine diagnostic tests among hospitalized fever patients in a 1.5 years period in 2015 and 2016. Methods From March 2015 to October 2016, paediatric and adult patients hospitalized with acute undifferentiated fever at Mnazi Mmoja Hospital, Zanzibar were included. The malaria prevalence, and performance of rapid diagnostic test (RDT) and microscopy, were assessed using polymerase chain reaction (PCR) as gold standard. Results The malaria prevalence was 9% (63/731). Children under 5 years old had lower malaria prevalence (5%, 14/260) than older children (15%, 20/131, p = 0.001) and persons aged 16 to 30 years (13%, 15/119, p = 0.02), but not different from persons over 30 years old (6%, 14/217, p = 0.7). All cases had Plasmodium falciparum infection, except for one case of Plasmodium ovale. Ten malaria patients had no history of visiting mainland Tanzania. The RDT had a sensitivity of 64% (36/56) and a specificity of 98% (561/575), and microscopy had a sensitivity of 50% (18/36) and a specificity of 99% (251/254), compared to PCR. The malaria parasitaemia was lower in patients with false negative results on RDT (median 7 × 103 copies/µL, interquartile range [IQR] 2 × 103 – 8 × 104, p = 0.002) and microscopy (median 9 × 103 copies/µL, IQR 8 × 102 – 7 × 104, p = 0.006) compared to those with true positive RDT (median 2 × 105 copies/µL, IQR 3 × 104 – 5 × 105) and microscopy (median 2 × 105 copies/µL, IQR 6 × 104 – 5 × 105). Conclusions The study emphasizes that malaria was a frequent cause of febrile illness in hospitalized patients in Zanzibar in the years 2015-2016, particularly among school age children and young adults. We found evidence of autochthonous malaria transmission in Zanzibar. Compared to PCR, both RDT and microscopy had low sensitivity, and false negative ...