Plasmodium species positivity rates across regions with different malaria transmission intensities in Mainland Tanzania: Data from a nationwide survey conducted in 2023

Although Plasmodium falciparum is the most prevalent and highly virulent species in Sub-Saharan Africa, non-falciparum species are increasingly recognized as a hidden burden. Generally, infections caused by non-falciparum species occur with low parasite densities and often present as co-infections with P. falciparum . These parasites may evade detection by routine diagnostics, complicating malaria case management and control efforts. To investigate the distribution of different Plasmodium parasites, we analysed 5,314 randomly selected samples from 18,969 samples collected across all 26 regions of Mainland Tanzania in 2023. Plasmodium parasites were detected using 18S qPCR. Of the analyzed samples, 52.3% (n = 2,780) were positive for any Plasmodium species. P. falciparum was detected in 51.2% (2,719/5,314), P. malariae in 1.4% (76/5,314), and P. ovale spp. in 1.8% (98/5,314) of the samples. Mixed infections were detected in 2.0% (107/5,314), with P. malariae and P. falciparum in 0.8% (40/5,314), and P. ovale mixed with P. falciparum in 1.1% (61/5,314) of the samples analysed. Among the samples with positive results (n = 2,780), mono-infections were detected at 93.9% (2,612/2,780) for P. falciparum , 1.1% (30/2,780) for P. malariae , and 1.1% (31/2,780) for P. ovale spp., respectively. Unlike P. malariae and P. ovale , P. falciparum infections were significantly influenced by transmission intensities, with the highest odds in regions with high transmission intensities compared to those with low (OR=1.61, p < 0.001), and very low transmission (OR=1.48, p < 0.001). School children had higher odds of P. falciparum infections compared to adults (OR=1.56, p < 0.001) and under-fives (OR=1.47, p < 0.001). Adults were also less likely to have P. malariae infections than schoolchildren (OR= 0.45, p = 0.021).The findings of the first-ever nation-wide survey reveal a high prevalence of P. falciparum , low prevalence of non-falciparum species, and complex species landscape. They underpin the need to expand surveillance systems beyond P. falciparum and adapt interventions to target all Plasmodium species.