The mapping results in the Littoral, North-West, South and South-West regions of Cameroon showed that schistosomiasis was endemic in all four regions, but with relatively low level of endemicity. Among the 81 schools surveyed, infection was found in only 19, 22 and 9 schools for S. haematobium, S. mansoni and S. guineensis, respectively. The average prevalence in each region was below 10% for all three schistosome species. However, due to the typical nature of focal transmission of schistosomiasis, moderate or high endemicity was found in 12 schools across the 81 schools surveyed in the four regions, with overall schistosomiasis prevalence (including all three species) up to 86%. When comparing our results with the previous nationwide data collected in 1985–1987 by Ratard et al. , it appears a slight increase of the number of high transmission foci of schistosomiasis. This is not surprising given the fact that no mass drug administration (MDA) with praziquantel had been implemented in these health districts since the last mapping survey. It is also noted that the main purpose of the current survey was to map out the distribution of schistosomiasis in these regions so that the implementation of the MDA intervention could be planned. Therefore, in contrast to the 1985–87 survey, the current survey took into consideration a relatively even spatial coverage to include all health districts. Also, ecological and risk factors and prior knowledge were considered during selection.
The overall level of schistosomiasis endemicity in these regions was in line with our expectation, and was similar to the endemicity level found in other southern regions . Indeed, based on the 1985–1987 mapping, the highest transmission level of schistosomiasis is in the northern part of Cameroon [4, 21], and MDA with praziquantel had been primarily focused in the three northern regions, whereas in the southern part of the country regular treatment with praziquantel was implemented only in those very few health districts highly endemic for schistosomiasis . Apart from two districts (i.e. Loum in the Littoral region and Mbongue in the South-West region), none of the other districts in the four regions investigated in the present study had received regular treatment with praziquantel before this survey. Further to the key outcomes and recommendations in the last publication from the mapping in the Centre, East and West regions , in future deworming campaigns, the distribution of praziquantel should be undertaken in all endemic health districts to include all school age children according to the WHO roadmap for schistosomiasis elimination and the preventive chemotherapy guidelines for schistosomiasis in school age children [20, 22, 23]. Considering the overall low endemicity of schistosomiasis in the majority of these health districts, treatment will be conducted at district level in rural zones, whereas in urban settings treatment will be focused in those sub-districts with high prevalence spots of schistosomiasis.
For STH, the current mapping showed an overall significant reduction of infection prevalence in all four regions investigated in comparison to previous mapping data collected in 1985–1987 [5, 6, 21], similar to the recent mapping in the Centre, East and West regions of Cameroon . The overall STH prevalence declined by 46-86% from 1985–87 to 2010 in the four regions surveyed. The decline was greatest in the Littoral region compared to the three other regions. As previously discussed , school age children in Cameroon have been dewormed with mebendazole nationwide in all 179 health districts since 2007. These results clearly illustrated the positive impact of the school-based deworming campaigns implemented annually by the Ministry of Public Health, through the National Programme for the Control of Schistosomiasis and Intestinal Helminthiasis. In addition to the positive impact of repeated treatment with mebendazole, the reduction in STH prevalence may have also benefited from the ivermectin MDA implemented in onchocerchiasis endemic communities. Despite the observed significant reduction of STH infections, the overall STH prevalence was still over the treatment intervention threshold (>20%) in North-West, South and South-West regions and in many communities in the Littoral region, and intensities of A. lumbricoides and T. trichiura infections were still relatively high. Therefore, the national control program should continue implementing annual deworming of school age children in all endemic districts of these regions. In addition, preschool children, women of childbearing age and adults at high-risk in certain occupations should also be treated, according to WHO recommendations .
Over the past few decades, significant progress has been made in the control of schistosomiasis, STH and other NTDs. WHO recommends comprehensive control measures for the control of NTDs including preventive chemotherapy, intensified and innovative disease management, vector and intermediate host control, veterinary public health at the human-animal interface, and provision of safe water, sanitation and hygiene [9, 22]. However, the current funding almost exclusively focuses on preventive chemotherapy with specific anthelminthic drugs that can safely be co-administered in co-endemicity situations, e.g. praziquantel and albendazole/mebendazole for the control of schistosomiasis and STH. In order to appropriately determine where treatment for which disease is required, accurate mapping of the different NTDs is a pre-requisite. Based on infection prevalence, communities can then be classified into low, moderate and high-risk categories according to WHO specific disease thresholds and the appropriate treatment regimen applied . The current mapping results provided a foundation for such program planning.
Finally, the results of the present study highlight the need of implementing praziquantel MDA in the endemic health districts in the four regions for the control and elimination of schistosomiasis. Based on the results, medicines were procured and, within the integrated national NTD control program, praziquantel MDA was extended in 11 of the 65 health districts in the four targeted regions; i.e. 3 health districts in the Littoral region, 3 in the North-West and 5 in the South-West. The results also highlight the need of continued deworming for STH infections in all 65 health districts of these regions. This effort will be coordinated with the lymphatic filariasis MDA using albendazole when it starts. The results also contribute to updating global information resource on the distribution of schistosomiasis and STH, recently developed as an open-access database .