Our integrated surveillance approach with three linked cross-sectional surveys, with conjoined malacological inspections, builds a more thorough assessment of the changing epidemiology of intestinal and urogenital schistosomiasis on the Lake Malawi shoreline, Fig. 1 and Table 1. Of note, is that the prevalence of both forms of schistosomiasis is increasing, Fig. 2, indicative perhaps that the force of infection  for each parasite is rising, with intestinal schistosomiasis being of newest public health concern here.
The unexpected occurrence of intestinal schistosomiasis elsewhere in Malawi, alongside the more well-known urogenital schistosomiasis, has been encountered before; the surveys conducted by Poole et al. in Chikhwawa during June 2012 noted that 24.9% and 9.1% of mothers and their pre-school-aged children were positive by urine CCA-dipsticks with ova-patent S. mansoni infections confirmed . While Biomphalaria was not detected in their search for local snails , the occurrence of B. pfeifferi, as shown here in Fig. 1, adds weight to their postulate of intermittent transmission of S. mansoni in Chikhwawa. They suggested that the occasional influx of upstream populations of B. pfeifferi in the Shire River, as being swept downstream during seasonal flooding, might then colonize temporary pools in the Lower Shire River flood plain, to spark sporadic transmission in Chikhwawa . By contrast, an enduring presence of B. pfeifferi along Lake Malawi and Upper Shire River, gives rise to more sustained opportunities in local transmission of S. mansoni in Mangochi District.
In regard of this lake shoreline setting, we have shown 1) increases in the prevalence of intestinal schistosomiasis at Mchoka and Samama Schools, 2) occurrence of intestinal schistosomiasis at MOET and Koche schools and 3) endemic intestinal schistosomiasis occurring along a 80 km section of Lake Malawi and Shire River shoreline, noting additional populations of B. pfeifferi on the lake’s eastern shoreline, Fig. 1. Of particular note is the strong association of S. mansoni infection, as detected by urine CCA-dipsticks, with FOB in 16.2% of examined children, see Table 2, indicative of overt intestinal pathology . Combined with the observations of ova-patent infections of moderate- and heavy-intensities at Koche and Ndembo, as well as, ova-patent infections at a further 5 schools, this is pervasive evidence of more sustained local transmission of intestinal schistosomiasis.
Whilst the debate on how to interpret ‘trace’ reactions of urine-CCA dipsticks continues, a ‘positive’ reaction is considered solid evidence of active intestinal schistosomiasis . Therefore, 31.5% [95% CI 27.5–35.5] of our sampled children were suffering from intestinal schistosomiasis but if a ‘trace’ reaction was considered diseased then a total of 82.5% [95% CI = 79.2–85.8] were infected or, at the very least, at-risk. Of particular note in this light is intestinal schistosomiasis at Ndembo and St Augustine II schools, see Fig. 1, where the prevalence of ‘positive’ urine-CCA dipsticks was > 50% and ova-patent S. mansoni infections were encountered, being of light and moderate infection intensities, Table 1; moreover, moderate and heavy ova-patent S. mansoni infections were detected at Koche school where the prevalence of ‘positive’ urine-CCA dipsticks was 35.0%, with B. pfeifferi found nearby.
Our rapid disease mapping surveillance across 8 schools, currently augments district-level information of the NCP, critically revising scientific appraisals concerning the previous absence of intestinal schistosomiasis , and better demonstrates the newly defined endemicity of intestinal schistosomiasis along the Mangochi District shoreline. When taken as a whole, we judge that there is now sufficient evidence to notify that an outbreak of intestinal schistosomiasis is occurring. This has immediate bearing on the health of the local populace and tourists who may visit here, as well as, in health advice or diagnostic testing undertaken in local or international medical clinics presently unaware of this new risk of intestinal schistosomiasis.
<please insert Fig. 3 near here>
In terms of environmental surveillance, it is worthy to note that the lake is undergoing ecological change, most easily seen with lake level changes through time, see Fig. 3. Its dynamic shoreline and lake level are manifest, perhaps creating new habitats for B. pfeifferi to colonize and or were facilitating collection of this snail in locations previously too deep to be retrieved by hand. The dispersion of this snail, a keystone species for S. mansoni, like in Senegal  or in Ethiopia , is a critical epidemiological driver of intestinal schistosomiasis transmission. We therefore recommend increased vigilance for B. pfeifferi, especially along the lake’s eastern shores and in downstream locations on the Shire River, with additional epidemiological inspections of adjacent schools and communities. This will better gauge the full footprint of intestinal schistosomiasis with newly recognized environmental opportunities for associated transmission.
Control of schistosomiasis needs a multisectoral approach and it is often debated how control tactics should be changed  or better tailored to aquatic environments . To respond to this outbreak of intestinal schistosomiasis, we propose that current MDA efforts should be intensified, adopting biannual treatment cycles in schools, which has been successfully implemented elsewhere , alongside expanded access to praziquantel for all community members with intestinal schistosomiasis, in need of regular treatment throughout the year . From recent surveys of adult fishermen who have urogenital schistosomiasis, making specific reference to male genital schistosomiasis, co-infection with S. mansoni has been noted alongside re-infections within a calendar year [20, 21]. To augment MDA and community-access to praziquantel, it is important to strengthen health education and outreach with suitable WASH interventions [20, 22], better appropriate to this lakeshore setting, noting that even focal application of molluscicides is inappropriate , given this lake’s global importance in biodiversity.