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MLW Translational Research: Nkhotakota Human African Trypanosomiasis Dynamics Study

1. Background

Zoonotic diseases are concentrated at the interface of human activity, livestock, and wildlife. These are usually marginal areas where the human population is very poor with little or no access to basic health services. Vector-borne zoonoses require well-thought control strategies as screening and treatment of the human population alone are not sufficient. Rhodesian Human African Trypanosomiasis (r-HAT), caused by Trypanosoma brucei rhodesiense, is a zoonosis with parasites circulating in wild animals and livestock. In Malawi upsurges in r-HAT cases, the current highest in Africa, have been reported in communities surrounding Vwaza (in Rumphi district), Kasungu, and Nkhotakota wildlife reserves since 2019. A combination of approaches including vector control and treatment of infected livestock or humans with trypanocides is recommended. Currently, case detection and treatment and, vector monitoring and control in the r-HAT foci in the country are minimally and haphazardly applied in an ad hoc manner subject to the availability of funds. The upsurges in cases complicate conservation efforts in these reserves as high livestock mortalities due to nagana make communities resort to poaching. Further, reduced tourism activities due to fears of contracting the disease reduce revenue from the reserves some of which are repurposed for community development. This compromises the sustainability of conservation efforts as communities do not see the direct benefits of the initiatives.

We have, since 2021, been conducting an r-HAT control operation in Nkhotakota via community-led vector control and HAT screening and treatment in humans. The overall goal of the project has been to implement an r-HAT control operation in the communities surrounding the Nkhotakota Wildlife Reserve. To achieve this goal, we have embarked on:

  • Estimating seasonal abundance of tsetse flies in communities surrounding the game reserve.
  • Determining the r-HAT prevalence rates in the human population to understand the most at-risk populations, where most cases are clustered and associated with risk factors.
  • Implementing a vector control strategy at the interface of the Nkhotakota Wildlife Reserve.
  • Foster community-led vector control for increased intervention uptake and sustainability

2. Human surveys

Three human surveys were planned in the project to provide seasonal indications and to clear parasites in human reservoirs. This interrupts the progress to severe disease. Active surveillance may also assist in understanding the current dynamics of tsetse vectors and human interactions, hence facilitating appropriate epidemiological interventions. Two surveys were undertaken in the dry season (September 2021) and wet season (January to February 2022). In these surveys, we undertook active r-HAT surveillance in hotspot communities using microscopy with a confirmation based on a diagnostic PCR, collected parasite stabilates and RNA samples for future references and mapped r-HAT cases locations for targeted deployment of interventions.

3. Vector Surveys

Three vector surveys were planned in the project to provide seasonal indications and to understand vector densities and distribution. This is aimed at linking the transmission risk with ecological factors and seasons for targeted deployment of vector control interventions. Two surveys were undertaken in November, 2021and January to February 2022. In both surveys, Acetone-baited Nzi traps were deployed in purposively selected locations in nine villages based on local reports of where biting takes place.

4. Tsetse control

One hundred and fifty insecticide-impregnated targets have been deployed by communities in 14 villages selected based on reports of r-HAT cases. Locations of the targets were based on local knowledge of where most of the tsetse biting takes place.

5. Partnerships

Robust collaborations have been developed with key stakeholders; African Parks (Nkhotakota Wildlife Reserve), The Nkhotakota District Health Office (DHO), and the Community.

6.  Next plans

Last r-HAT screening and tsetse monitoring are scheduled for July 2022 Interface meetings with Stakeholders (The Community, The DHO, and The African-Parks-Nkhotakota Wildlife Reserve) and the District Executive Committee (DEC) are scheduled for July 2022