Hidden Malaria Vectors and Parasites Revealed Across Tanzania by New DNA Sequencing Panel

Malaria remains one of the deadliest infectious diseases on the planet, and the fight against it depends on knowing exactly which mosquitoes transmit the parasite and where they live. A new study published in Parasites & Vectors has now delivered one of the most comprehensive molecular surveys of malaria vectors ever conducted in Tanzania, revealing a hidden diversity of Anopheles mosquitoes and Plasmodium parasites that routine surveillance tools have been quietly missing. The findings, drawn from more than 71,000 mosquitoes collected across 25 districts of mainland Tanzania between 2020 and 2023, suggest that the country’s malaria landscape is more complex than current control strategies assume.

The research team, led by Maneno E. Baravuga of the Ifakara Health Institute and the Wellcome Sanger Institute, together with colleagues including Mara K. N. Lawniczak and Nicodem J. Govella, applied a previously published amplicon sequencing panel known as ANOSPP to characterise both mosquito and parasite diversity simultaneously. Unlike conventional PCR assays, which are typically restricted to the major vector complexes such as the Anopheles gambiae species group, ANOSPP is designed to resolve a much broader range of Anopheles species and Plasmodium parasites in a single workflow. This capability proved decisive in a country where the full spectrum of vector species has never been systematically catalogued at the molecular level.

Of the 71,146 mosquitoes collected during the survey, only 10,020, or 14.0 percent, were Anopheles. Molecular identification using ANOSPP resolved 15 distinct species across the country. Among these were two notable firsts for Tanzania: the first record of Anopheles funestus-like, represented by 10 specimens, and the first resolution of Anopheles longipalpis to Type C in the country, with 13 specimens identified. These discoveries are significant because both species belong to complexes whose members are morphologically indistinguishable, yet may differ in their capacity to transmit malaria parasites. Anopheles funestus-like, in particular, is a close relative of the major vector Anopheles funestus sensu stricto, and its presence in Tanzania raises questions about whether it plays a role in local transmission that has previously gone unnoticed.

The study also used ANOSPP assignments as a molecular benchmark against which traditional morphological identification could be evaluated. The results were sobering for anyone who has relied on visual inspection of mosquito features. Morphology misclassified 6.2 percent of specimens that were analysed by ANOSPP, with Anopheles rufipes and Anopheles maculipalpis frequently misidentified. More strikingly, Anopheles pretoriensis and Anopheles marshallii sensu lato were completely missed by morphological identification, meaning that these species would have gone entirely undetected without molecular sequencing. This level of error matters because misidentified specimens can distort estimates of vector species composition, which in turn inform decisions about which control interventions to deploy in a given area.

On the parasite side, the study detected five Plasmodium species across 37 Plasmodium-positive mosquitoes: Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, Plasmodium malariae, and Plasmodium caprae. The detection of P. falciparum was expected, as it is the dominant malaria parasite in Tanzania and the primary focus of routine diagnostic workflows. However, the presence of the other four species is remarkable. Plasmodium vivax, which is historically rare in Africa due to the high prevalence of Duffy-negative red blood cells among African populations, has been increasingly reported in recent years, and its detection in Tanzanian mosquitoes adds to the growing body of evidence that non-falciparum malaria may be more widespread on the continent than previously thought.

The most striking parasite discovery was Plasmodium caprae, a parasite species that primarily infects goats and was found only in Anopheles arabiensis mosquitoes, with six positive specimens. This represents the first record of P. caprae in Tanzania and, remarkably, the first detection of this parasite in Anopheles arabiensis anywhere in the world. The finding raises intriguing questions about the potential for zoonotic malaria parasites to circulate in African mosquito populations, and whether such parasites could pose any risk to human health. While P. caprae is not known to infect humans, its presence in a major human malaria vector suggests that the boundaries between parasite species that infect livestock and those that infect humans may be more permeable than previously recognised.

Beyond the species discoveries, the study examined whether the spatial distribution of primary vector species was associated with patterns of malaria endemicity across Tanzania. The researchers linked district-level patterns of vector co-occurrence to the National Malaria Control Programme transmission strata and an underlying composite malaria risk score. The results showed that the co-occurrence of Anopheles arabiensis, Anopheles funestus sensu stricto, and Anopheles gambiae sensu stricto was more common in districts with higher malaria transmission intensity. In contrast, districts in the very-low and low transmission strata were characterised predominantly by the presence of Anopheles arabiensis alone. This pattern suggests that areas with the highest malaria burden are those where multiple primary vectors overlap, creating conditions that favour sustained and intense transmission.

The implications of these findings for malaria control in Tanzania are substantial. The three primary vectors identified in the study, Anopheles arabiensis, Anopheles funestus sensu stricto, and Anopheles gambiae sensu stricto, are the main targets of current interventions such as insecticide-treated bed nets and indoor residual spraying. However, the discovery of additional vector species, some of which belong to complexes that are morphologically indistinguishable from primary vectors, suggests that current control strategies may need to account for a wider range of mosquitoes than previously considered. Anopheles funestus-like, for example, may share ecological characteristics with its major vector relative, potentially allowing it to survive and transmit parasites in environments where the primary vectors have been suppressed by existing interventions.

The study also highlights the limitations of routine surveillance tools that are optimised for detecting Plasmodium falciparum. The detection of P. vivax, P. ovale, P. malariae, and P. caprae in Tanzanian mosquitoes indicates that non-falciparum parasites are circulating in the country’s vector populations, yet these species would not be detected by workflows designed exclusively for P. falciparum. This has potential consequences for clinical case management, as infections with non-falciparum species may require different treatment approaches and may be missed by rapid diagnostic tests that target only P. falciparum antigens. The researchers conclude that routine surveillance tools remain valuable for monitoring major malaria vectors, but that integrating ANOSPP substantially improved both vector and parasite resolution, uncovering new species records and detecting atypical and non-falciparum Plasmodium species that routine workflows miss.

As Tanzania continues its efforts to reduce the burden of malaria, studies like this one provide a critical foundation for understanding the full complexity of the transmission landscape. The combination of large-scale field collection across diverse ecological settings and high-resolution molecular identification offers a template for how other malaria-endemic countries might approach the challenge of characterising their own vector and parasite diversity. The discoveries of Anopheles funestus-like, Anopheles longipalpis Type C, and Plasmodium caprae in Tanzania demonstrate that even in a country where malaria has been studied for decades, there is still much to learn about the mosquitoes and parasites that drive one of humanity’s oldest diseases.

Subject of Research: A molecular survey using the ANOSPP amplicon panel revealed 15 Anopheles species and five Plasmodium species across Tanzania, including the first record of Plasmodium caprae in the country and its first global detection in Anopheles arabiensis.

Article Title: Exploring the diversity and spatial distribution of Anopheles mosquitoes and their associated Plasmodium species in Tanzania using the ANOSPP amplicon panel

Article References: Exploring the diversity and spatial distribution of Anopheles mosquitoes and their associated Plasmodium species in Tanzania using the ANOSPP amplicon panel. (n.d.). https://doi.org/10.1186/s13071-026-07737-y

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07737-y

Keywords: Exploring, diversity, spatial, distribution, Anopheles, mosquitoes, associated, Plasmodium, species, Tanzania, ANOSPP, amplicon