New Study highlights demographic shift of VL to older patients and increased incidence of relapses in Brazil
A new study into visceral leishmaniasis (VL) in Brazil has created the most comprehensive picture of the disease in the country, and highlighted trends including more older patients being diagnosed with the disease and more patients presenting with relapses over time.
The paper, Epidemiological shifts in visceral leishmaniasis incidence, relapse, and mortality in Brazil, 2007-2023: Analysis using National Notifiable Diseases Information System, has been published in the Open Forum Infectious Diseases.
The paper, led by IDDO’s WHO/TDR Fellow Dawit Getachew Assefa, sets out the long-term epidemiological trends in disease incidence, and identifies persistent hotspots in Tocantins, Maranhão, Mato Grosso do Sul, Ceará, and Minas Gerais.
VL is a neglected tropical disease that is transmitted by female sandflies. It is the most severe of the three forms of leishmaniasis and is almost always fatal without treatment.
Brazil currently accounts for over 90% of VL cases reported in South America. But VL cases fell every year by around 6.0% between 2007-2023, likely due to improved vector control efforts, including insecticide spraying, canine reservoir control and improvements in housing and sanitation. In particular, a major drop in cases has been observed during 2019-2023.
Varying trends
However, researchers caution that national trends may obscure regional variations, because VL transmission is influenced by socio-environmental factors and spatial clustering, with incidence reductions varying by region. This is because of heterogeneous intervention coverage and evolving ecological risks like urbanisation, particularly in Tocantins and Mato Grosso do Sul.
This new work used 55,723 patient records from 2007-2023 from the open-access SINAN database, and compared records between 2007-2009 and 2019-2023.
Overall, the results showed the annual VL incidence in Brazil decreased by 6% per year, largely driven by changes observed over the past 5 years, while the median age of patients increased from 10-years-old in 2007 to 32-years-old in 2023. The analysis also showed the proportion of patients presenting with a relapse and presenting with HIV co-infection had steadily increased over time.
Newer drugs
During the same period, the use of liposomal amphotericin B, a less toxic and more effective drug, increased in use from 6.1% to 38.1%, displacing the older, traditional drug Pentavalent antimony, which was the primary treatment for VL – its use fell from 68.0% to 32.7%. The analysis also showed that after treatment, death from VL was highest among infants and patients aged over 50 years.
First author Dawit Getachew Assefa, former IDDO WHO/TDR Fellow and currently undertaking AfOx Fellowship, said: “Our analysis offers a comprehensive long-term overview regarding the epidemiology of VL in Brazil. We identified a shift in age-distribution of patients and were able to characterise the spatial variability in disease incidence over time. The analysis and interpretation of the finding was possible through a close collaboration with our colleagues from Brazil who were able to mentor this project. At a personal level, this project has been a major learning curve in undertaking collaborative science and enhancing my epidemiological skillset”.
VL expert and study co-author Dr. Glaucia Cota, from the Instituto René Rachou, Fiocruz Minas, Belo Horizonte, Brazil, said: “This has been a fruitful collaboration and extremely valuable descriptive epidemiology offering several valuable insights.”
Dr Cota, who also mentored this study, added “The clear identification of demographic shift of the disease towards adults, the rise in VL-HIV co-infections over time, and a mapping of the patterns of the drug usage by age-distribution, all provide important signals. Together, these findings help generate hypotheses, highlight emerging epidemiological phenomena, and identify key areas for deeper investigation into disease dynamics, clinical trajectories, and long-term outcomes in Brazil."
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About VL
Visceral leishmaniasis (VL) is one of the neglected tropical diseases aimed for elimination by 2030. The disease is often fatal if not treated promptly
Globally, VL is principally endemic in four regions: the Indian sub-continent (ISC), East Africa, the Mediterranean basin and South America. In the Americas, the transmission of the disease is zoonotic with L. infantum as the causative parasite and dogs as the main reservoir. In Brazil, VL disproportionately affects the Northeast regions and is strongly linked to poverty, malnutrition, environmental changes, and migration patterns.
Over the past three decades, the endemicity of disease has expanded from rural areas in the North and Northeast regions to many urban areas and newly developed cities throughout the country. VL thus continues to be a major public health concern in Brazil and is recognised as a notifiable disease in the country.