Human behaviour and residual malaria transmission in Zanzibar: findings from in-depth interviews and direct observation of community events

Abstract

Background Zanzibar has maintained malaria prevalence below 1% for the past decade, yet elimination remains elusive despite high coverage of core vector control interventions. As part of a study investigating the magnitude and drivers of residual transmission in Zanzibar, qualitative methods were utilized to better understand night time activities and sleeping patterns, individual and community-level risk perceptions, and malaria prevention practices. Methods A total of 62 in-depth interviews were conducted with community members and local leaders across six sites on Unguja Island, Zanzibar. Twenty semi-structured community observations of night-time activities and special events were conducted to complement interview findings. Data were transcribed verbatim, coded, and analysed using a thematic approach. Results Participants reported high levels of ITN use, but noted gaps in protection, particularly when outdoors or away from home. Routine household and community activities were common in evenings before bed and early mornings, while livelihood activities and special events lasted all or most of the night. Gender variation was reported, with men routinely spending more time away from home than women and children. Outdoor sleeping was reported during special events, such as weddings, funerals, and religious ceremonies. Participants described having difficulty preventing mosquito bites while outdoors, travelling, or away from home, and perceived higher risk of malaria infection during these times. Travel and migration emerged as a crucial issue and participants viewed seasonal workers coming from mainland Tanzania as more likely to have a malaria infection and less likely to be connected to prevention and treatment services in Zanzibar. Some community leaders reported taking the initiative to register seasonal workers coming into their community and linking them to testing and treatment services. Conclusions Targeting malaria interventions effectively is critical and should be informed by a clear understanding of relevant human behaviour. These findings highlight malaria prevention gaps in Zanzibar, and the importance of identifying new approaches to complement current interventions and accelerate the final phases of malaria elimination. Development and deployment of complementary interventions should consider human behaviour, including gender norms, that can influence exposure to malaria vectors and prevention practices. Expansion of community-level programmes targeting travellers and seasonal workers should also be explored.

Knowledge, Attitudes, Practices and Risk factors about Malaria in High Endemic Rural Eastern Tanzania

“…Furthermore, most respondents reported night-time communal ceremonies/gatherings, which may take more than three days. Similar observations are increasingly documented in many other malaria endemic resource-poor settings [17,43,[44][45][46]. Cooking and communal ceremonies/gatherings have been reported among the popular activities that kept people outdoors in many endemic areas of Africa notably Kilombero Valley, southern Tanzania [17,44,47], Unguja Island, Zanzibar [46], northern…”

“…Tanzania [17,44,46] and elsewhere in Africa [43,45,48], respondents reported little or no protection at all during outdoor activities at or away from home. Purportedly, the study communities experience a high risk of malaria because the documented night-time outdoor activities take long periods which may coincide with vector's peak biting time.…”

Evidence of extrinsic factors dominating intrinsic blood host preferences of major African malaria vectors

“…Similarly little is known of the short-and long-term impacts of different control methods on host choice.The introduction of indoor residual spraying and insecticidal nets has resulted in a change in the biting behaviour of major malaria vectors with many mosquito species seeking a higher proportion of blood meals outdoors 3-6 and/or from non-human hosts 7-10 . Coupled with increasing rates of insecticide resistance 11 , these behavioural changes indicate potential inadequacies of current leading vector-control tools to target outdoor biting and, correspondingly, sustained residual malaria transmission [12][13][14][15][16][17][18][19] . Therefore, understanding this behaviour is becoming increasingly important when implementing vector control strategies.In the field, which host is ultimately bitten is a complex balance between intrinsic (genetic) and extrinsic (environmental) factors including behavioural conditioning driven by exposure to insecticides or previous successful feeds from a particular host 20,21 .…”

Association Between Recent Overnight Travel And Use Of Long-Lasting Insecticidal Nets In Rural Uganda: A Prospective Cohort Study In Tororo

“…A strength of this study is that behaviours at home and during travel within the same individuals were prospectively compared, minimizing the potential for confounding. Similar studies have only assessed malaria-relevant behaviours while travelling, or at home, but not both [23,41,42]. A study conducted in south-eastern Tanzania evaluated human behaviour of participants at home [20].…”

“…Although travellers may be at increased risk of malaria due to exposure to higher malaria transmission [18,19], changes in behaviour while away from home may also contribute. Some studies have suggested that individuals who travel within malaria-endemic areas may take part in outdoor activities, go to bed late, and be less likely to use LLINs, all behaviours that increase exposure to mosquitoes and risk of malaria infection [20][21][22][23]. To further explore associations between overnight travel and behaviours that might modify the risk of malaria infection, data collected over a two-year period from a cohort of individuals living in Tororo, Uganda, were analysed.…”