Everyone involved in the HUGS and SHIRE_VEC projects is delighted with Clinton Nkolokosa’s recent research paper, A first report of Biomphalaria pfeifferi in the Lower Shire Valley, Southern Malawi, a major intermediate snail host species for intestinal schistosomiasis, recently published within Scientific Reports.
This multi-author manuscript draws attention to the clear need for appropriate snail control, for example justifying an application of focal molluscicide, within Chikwawa. It also solves an older epidemiological puzzle about local transmission of intestinal schistosomiasis.
The origins of this puzzle trace back to a field MSc project by LSTM student and paediatrician Helen Poole in 2013. She worked under the joint supervision of Russell Stothard and Anja Terlouw, examining around 373 patients within 12 villages. It was then noted that urogenital schistosomiasis was very common within mothers (~50%) and their pre-school-aged children (~20%), however, the surveys unexpectedly found and confirmed a sizeable proportion (~20%) of participants also with intestinal schistosomiasis co-infection.
This was a seminal disease alert and Poole et al.’s report was even more surprising for the intermediate snail host for intestinal schistosomiasis, Biomphalaria, was proven absent from the study area. The team then postulated either that intestinal schistosomiasis was not acquired locally, perhaps being contracted elsewhere, potentially around Blantyre, or if local transmission did occur it was intermittent through time, such as shortly after periods of prior flooding. It now seems that the latter was correct, evidenced by the effects of cyclonic flooding within the area during 2023.
During late 2023, through to early 2024, Clinton and his snail collecting team conducted several snail surveys to find Biomphalaria pfeifferi within a handful of key aquatic habitats. In one particular location, Illovo Estate, very high numbers of snails were found. This then led to the estate taking ameliorative action to clean the canal, removing water lilies and snails, with mechanical excavators. In February 2025, the HUGS E12 environmental survey visited the same canal and confirmed that snail numbers were vastly reduced.
This recent observation, however, now poses a different question – how long will reduced snail numbers remain so? Only time will tell, but we can be sure that Clinton’s excellent report will serve as the baseline for future comparison.