Date Published: March 11, 2019
Publisher: Oxford University Press
Author(s): Nathalie J Lambrecht, Mark L Wilson, Andrew D Jones.
Animal husbandry and capture (AHC) may mitigate anemia among women and children by supplying a source of micronutrient-rich animal source foods (ASF), yet may concurrently increase exposure to anemia-inducing pathogens such as Plasmodium spp., helminths, and enteropathogens. We conducted a systematic literature review to assess the relation between AHC and anemia among women of reproductive age, school-aged children, and children aged <5 y in low- and middle-income countries (LMICs). We used a 2-stage screening process, in which 1 reviewer searched 4 databases (PubMed, Web of Science, EMBASE, and Global Health) with predetermined search terms for relevant articles. Two reviewers then independently screened studies using a priori exclusion criteria, yielding a total of 23 articles included in the final review. We evaluated evidence from observational studies assessing animal-dependent livelihoods and livestock ownership, and interventions that promoted livestock and fish production. We found little consistency in anemia outcomes across the several AHC exposures and population groups. Poultry production interventions had modest benefits on anemia among women and children, although whether these improvements were a result of increased ASF consumption, or a result of the combined treatment study design could not be determined. Observational studies identified chicken ownership, and no other livestock species, as a risk factor for anemia among young children. However, there was limited evidence to evaluate pathways underlying these associations. Studies tended to rely on self-reported fever and diarrhea to assess illness, and no study directly assessed linkages between AHC, pathogen burden, and anemia. Thus, there is insufficient evidence to conclude whether AHC improves or worsens anemia among women and children in LMICs. Given the current interest in promoting animal production among low-income households, future studies with robust measures of livestock ownership, ASF consumption, pathogen burden, and anemia status are needed to understand the nuances of this complex and potentially contradictory relation.
Animals play an integral role in the livelihoods of people around the world. For the nearly 1 billion rural poor living in Sub-Saharan Africa and South Asia that raise livestock (1) and the approximately 160 million people engaged in fish-related activities (2), animals are a source of income, food, manure, draught power, transportation, financial stability, and social status (3). Animal source foods (ASF) are rich in key micronutrients often missing in staple-based diets, notably iron, zinc, vitamin A, vitamin B12, riboflavin, calcium, and essential fatty acids (1, 3). Inadequacies in these micronutrients contribute to severe short- and long-term health consequences, especially among women and children living in low- and middle-income countries (LMICs) (4). Consumption of ASF is, therefore, a viable strategy for reducing micronutrient deficiencies among women and children. At the same time, animal rearing may have negative repercussions for human health. Raising or consuming animals can expose people to infectious disease pathogens through direct contact, or indirectly via blood-feeding arthropod vectors and fecal contamination of the local environment (5, 6). Such zoonotic infections in humans, which involve microbe transmission cycles among animals and “spillover” to humans, significantly contribute to the human disease burden in LMICs, particularly in resource-poor environments where animals and humans live in close proximity (7).
This systematic review follows the reporting guidelines set forth by the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement (28). The review protocol was not registered.
This systematic review assessed the relation between animal husbandry and capture and anemia among women of reproductive age, school-aged children, and children aged <5 y by evaluating evidence from observational and intervention studies of pastoral livelihoods, livestock ownership, and fishing. A secondary objective of the review was to explore the hypothesized pathways by which AHC may influence anemia status as shown in Figure 1 (i.e., through ASF consumption and pathogenic infections). Overall, we found little consistency in results across several AHC exposures and population groups. Therefore, we have limited confidence in determining whether AHC promotes or prevents anemia. Further, our assessment of the evidence was hampered by study methods that were not designed to answer our research questions; for example, studies had poor comparison groups, missing data on diet and morbidity indicators, and insufficient adjustment for confounding. Our conclusions agree with 2 other recent reviews that the evidence base for evaluating iron and anemia status, consumption of ASF, and morbidity outcomes as they relate to animal production is weak (22, 23). Nevertheless, we noted that some AHC exposures were more often associated with specific anemia outcomes. Below, we elaborate on these trends and describe recommendations and implications for future research. Source: http://doi.org/10.1093/advances/nmy080