Human hookworm infection: Is effective control possible? A review of hookworm control efforts and future directions.

Human hookworm, a soil-transmitted helminth (STH) infection caused by either Necator americanus or Anclystoma duodenale, is a major cause of morbidity globally and predominantly affects the world's poorest populations. Transmitted primarily by larval invasion of exposed skin, the adults inhabit the host small intestine, where they consume host blood. The resultant chronic iron deficiency anemia can lead to stunted growth and cognitive deficits in children, reduced work capacity in adults, and a variety of pregnancy complications. Historically, successful STH elimination has only been achieved in regions with concomitant significant economic growth. Since 2001, control of the STHs has been attempted via single-dose mass deworming of at-risk school-aged and preschool-aged children within STH-endemic countries, with the goal of morbidity reduction. Research questioning this strategy has grown in recent years, and current studies are evaluating the effectiveness of novel deworming strategies, including multidrug regimens and expansion of deworming to entire communities. While footwear campaigns may be associated with reduced odds of hookworm infection, the evidence supporting the impact of water, sanitation, and hygiene (WASH) interventions upon hookworm is mixed. Progress towards a human hookworm vaccine continues, with promising results from recent Phase 1 trials and several others ongoing. Integrated STH control programs, which combine mass deworming with WASH interventions, are relatively unstudied but may be a promising advancement. Whether interruption of STH transmission can be achieved apart from significant economic growth remains unanswered, but likely the implementation of intensive, integrated control programs will be necessary to achieve that goal.

Establishment of a self-propagating population of the African malaria vector Anopheles arabiensis under semi-field conditions.

BACKGROUND: The successful control of insect disease vectors relies on a thorough understanding of their ecology and behaviour. However, knowledge of the ecology of many human disease vectors lags behind that of agricultural pests. This is partially due to the paucity of experimental tools for investigating their ecology under natural conditions without risk of exposure to disease. Assessment of vector life-history and demographic traits under natural conditions has also been hindered by the inherent difficulty of sampling these seasonally and temporally varying populations with the limited range of currently available tools. Consequently much of our knowledge of vector biology comes from studies of laboratory colonies, which may not accurately represent the genetic and behavioural diversity of natural populations. Contained semi-field systems (SFS) have been proposed as more appropriate tools for the study of vector ecology. SFS are relatively large, netting-enclosed, mesocosms in which vectors can fly freely, feed on natural plant and vertebrate host sources, and access realistic resting and oviposition sites. METHODS: A self-replicating population of the malaria vector Anopheles arabiensis was established within a large field cage (21 × 9.1 × 7.1 m) at the Ifakara Health Institute, Tanzania that mimics the natural habitat features of the rural village environments where these vectors naturally occur. Offspring from wild females were used to establish this population whose life-history, behaviour and demography under semi-field conditions was monitored over 24 generations. RESULTS: This study reports the first successful establishment and maintenance of an African malaria vector population under SFS conditions for multiple generations (> 24). The host-seeking behaviour, time from blood feeding to oviposition, larval development, adult resting and swarming behaviour exhibited by An. arabiensis under SFS conditions were similar to those seen in nature. CONCLUSIONS: This study presents proof-of-principle that populations of important African malaria vectors can be established within environmentally realistic, contained semi-field settings. Such SFS will be valuable tools for the experimental study of vector ecology and assessment of their short-term ecological and longer-term evolutionary responses to existing and new vector control interventions.