Genomic characterization of dengue epidemics in Tanzania


Genomic characterization of dengue epidemics in Tanzania

genomic characterization, Tanzania

Gaspary Mwanyika from the SACIDS Foundation for One Health, Sokoine University of Agriculture, Tanzania details the importance of genomic characterization in controlling dengue

Dengue fever is the most important mosquito-borne viral disease of public health concern. Globally, the disease affects approximately 400 million people, resulting in more than 25,000 deaths each year. The overall prevalence of dengue infection in Africa is 14%, with serotypes 1 and 2 being the main causes of epidemics on the continent. Dengue fever control faces several challenges. The lack of a dengue virus vaccine makes it difficult to control the disease, increasing the risk of virus transmission. The disease often presents with nonspecific symptoms similar to other illnesses like malaria, yellow fever, Zika, chikungunya, and influenza, hence the need for rapid laboratory confirmation for a correct diagnosis. This highlights the need for improved differential diagnosis of febrile illnesses on the continent. Vector control and early detection remain the main strategies for dengue prevention and control.

Dengue fever in Tanzania

Prior to 2010, very little was known about the epidemiology of dengue fever in Tanzania and its impact was underestimated due to insufficient surveillance and diagnostic capacity. Since then, annual dengue fever outbreaks have been reported in the city of Dar es Salaam, which has become the epicenter of outbreaks in Tanzania.

Studies in Tanzania show that dengue infections are common in rural and urban communities. Misdiagnoses of dengue fever and co-infections with other febrile illnesses such as malaria and chikungunya have also been reported in Tanzania.

Dengue virus exposure in various ecological zones of Tanzania

Population-based serological studies have reported the presence of dengue virus in the human population across Tanzania, with the highest seroprevalence reported in the northeastern part of the country; with an overall prevalence of 16.1%. These results suggest widespread virus circulation and that a large proportion of those exposed are unlikely to be diagnosed by routine health care services due to the unavailability of reliable rapid diagnostic tools. Therefore, it is important that dengue virus surveillance and diagnostic platforms are strengthened in Tanzania to improve early diagnosis, patient management and outcomes.

Dynamics of dengue virus serotype circulation in Tanzania: a lesson for future outbreak response

Studies in Tanzania have indicated that dengue serotypes 1, 2 and 3 are prevalent. Nevertheless, the genomic characterization of circulating serotypes is not often carried out. Using field-deployable Oxford nanopore MinION sequencing technology, a recent study confirmed active transmission of dengue serotype 1 during the 2019 outbreak for the first time.

The analysis indicates that there was a possible introduction of dengue virus serotype 1 genotype V into Tanzania from a single source in Asia. These observations suggest that the introduction of new serotypes and/or genotypes in Tanzania could increase the risk of serious epidemics in the future. Indeed, immunity against earlier serotypes does not confer long-term cross-protection against later infecting serotypes. These results argue for the need for genomic characterization and surveillance of viruses recovered from the human population in Tanzania.

genomic characterization, Tanzania
“Globalization due to international connectivity through massive human travel from epidemic and endemic countries makes the risk of dengue fever transmission and spread inevitable in Tanzania.”

Opportunities to improve dengue diagnosis at the point of care

Studies indicate that rapid diagnostic tests have low specificity due to inherent cross-reactivity that can lead to misdiagnosis of dengue infection. In a study in Tanzania, we characterized the antigenic determinants of domain III of the dengue virus envelope protein using bioinformatics tools.

The domain III protein harbors serotype-specific antigenic determinants and induces potent neutralizing antibodies that make it a suitable biomarker for developing new diagnostic tools. In our study in Tanzania, we demonstrated that domain III proteins consist of conformational antigenic determinants that can be expressed in single bacterial cells as potential targets for developing diagnostic nanobodies. The application of nanobody-based diagnostic tools can help improve point-of-care diagnosis of dengue virus infection and minimize misdiagnosis with other infections.

The risk of transmission and spread of dengue is inevitable in Tanzania

Dengue fever is prevalent in various ecological zones of Tanzania, which can be partly attributed to the tropical climate and human activities that promote the presence and abundance of mosquito vectors near human habitats. The circulation of multiple dengue virus serotypes 1, 2 and 3 in Tanzania can lead to explosive outbreaks and an increased risk of serious illness in the future.

Globalization due to international connectivity through mass human movement from epidemic and endemic countries makes the risk of dengue transmission and spread inevitable in Tanzania. Studies in Tanzania indicate the need to characterize dengue virus genomes in order to monitor the spread of new/emerging genotypes and to develop reliable point-of-care diagnostic tests that can provide rapid evidence of the dengue epidemic. disease to guide public health interventions.

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© 2019. This work is under license CC-BY-NC-ND.

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