The dynamics of malaria transmission was studied comparatively in the villages of Zatta and Tiemelekro, central Cote d'Ivoire, from February 2002 to August 2003. Prominent agroecosystems in these villages are irrigated rice growing and vegetable farming, respectively. Mosquitoes (Diptera: Culicidae) were collected on human bait at night and by pyrethrum knock-down spray sheet collections at four randomly selected sentinel sites in each village. In 2002, for a total of 96 man-nights per village, 7716 mosquitoes were collected in Zatta and 3308 in Tiemelekro. In 2003, with half the sampling effort, 859 and 2056 mosquitoes were collected in Zatta and Tiemelekro, respectively. Anopheles gambiae Giles s.l. was the predominant mosquito and the key malaria vector throughout, followed by An. funestus Giles. Anthropophily among adult female Anopheles exceeded 95% in both villages. Comparison between years revealed that the biting rate of An. gambiae s.l. in Zatta decreased several-fold from 49.3 bites per person per night (b/p/n) in 2002 to 7.9 b/p/n in 2003 (likelihood ratio test (LRT) = 1072.66; P < 0.001). Although the biting rate remained fairly constant in Tiemelekro, the difference between years was significant (16.1 vs. 18.2 b/p/n; LRT = 148.06; P < 0.001). These observations were paralleled by a marked decrease in the infective rate of An. gambiae s.l. in Zatta (4.6-1.2%), and an increase in Tiemelekro (3.1-7.6%). Meanwhile, the entomological inoculation rate of An. gambiae s.l. decreased 21-fold in Zatta, from 789 to 38 infective bites per person per year (ib/p/y), whereas it remained high in Tiemelekro (233 vs. 342 ib/p/y). The interruption of irrigated rice growing in Zatta in 2003, consequential to a farmers' conflict over land, might be the underlying cause for the significant reduction in malaria transmission, whereas more stable conditions occurred in Tiemelekro.

The seasonality of malaria transmission was investigated in two villages in central Côte d'Ivoire: one usually with irrigated rice farming (Zatta) and one without (Tiémélékro). Adult mosquitoes were collected, from February 2002 to August 2005, inside and outside sentinel houses. In Tiémélékro, the biting rate of Anopheles gambiae s.s. showed a significant difference between the dry and rainy season only in 2003 (P<0.001). The corresponding rates for An. funestus s.s. showed significant seasonal differences in both 2002 and 2003 (P<0.001 for each year). In Zatta in 2003-2004, when irrigated rice farming was interrupted, there was no significant difference between the An. gambiae s.s. biting rates recorded in the dry and rainy seasons. In both 2002 and 2005, however, when irrigated rice farming was practised, the An. gambiae s.s. biting rate recorded in Zatta during the rainy season was significantly higher than that seen in the dry season (P<0.001 for each year). With just one exception (in Tiémélékro in 2005, the prevalence of Plasmodium infection in the An. funestus was significantly higher in the rainy season than in the dry season), no significant seasonal differences were seen in the prevalences of Plasmodium infection among the An. gambiae or An. funestus. In conclusion, although malaria transmission is quite stable in central Côte d'Ivoire throughout the year, it can be distinctly modified by irrigated rice farming.

BackgroundAmong parasitic infections, schistosomiasis ranks second after malaria in terms of worldwide morbidity. Despite efforts to contain transmission, more than 230 million people are infected, of which 85% live in Sub-Saharan Africa. While the epidemiologic characteristics of schistosomiasis have been extensively studied across endemic settings, social factors have been paid less attention. The current study assesses community knowledge of schistosomiasis causes, transmission, signs, symptoms and prevention, as well as healthcare-seeking behaviours in two West African settings, with the aim of strengthening schistosomiasis control interventions.MethodsFrom August 2014 to June 2015, we conducted two cross-sectional surveys in Korhogo, Côte d’Ivoire and Kaédi, Mauritania. We applied a questionnaire to collect quantitative data at the household level in Korhogo (n = 1456) and Kaédi (n = 1453). Focus group discussions (Korhogo: n = 32, Kaédi: n = 32) and participatory photography (photovoice) (Korhogo: n = 16, Kaédi: n = 16) were conducted within the communities to gather qualitative data. In addition, semi-structured interviews were used to discuss with key informants from control programmes, non-governmental organizations and health districts (Korhogo: n = 8, Kaédi: n = 7).ResultsThe study demonstrated that schistosomiasis is not well known by the communities; 64.1% claimed to know the causes of the disease, but the reality is different. This knowledge is more from cultural than biomedical source. It was observed that social construction of the disease is different from the biomedical definition. In Korhogo, schistosomiasis was often associated with several other diseases, notably stomach ulcer and gonorrhoea. The populations believe that schistosomiasis is caused by exposure to goat or dog urine in the environment. In Kaédi, schistosomiasis is considered as a disease transmitted by environmenal elements such as sunshine and dirty water. In both settings, the care-seeking pathways were found to be strongly influenced by local customs and self-medication acquired from the informal sector.ConclusionsThis study revealed that knowledge about the aetiology, transmission, symptoms, prevention and treatment of schistosomiasis among the populations in Korhogo and Kaédi is based on their local culture. Deep-rooted habits could therefore pose a significant obstacle to the elimination of schistosomiasis.Electronic supplementary materialThe online version of this article (10.1186/s40249-018-0453-0) contains supplementary material, which is available to authorized users.

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