Malnutrition and risk of kala-azar: a systematic review with meta-analysis

This systematic review was conducted with the objective of clarifying the association between malnutrition and the risk of developing kala-azar in humans. The research question was formulated using the PECO acronym: "Is malnutrition a risk factor for the development of kala-azar?" The search was carried out between September and November 2022, with an update in October 2024, in the PubMed, Embase, CAPES Journal Portal databases, and the grey literature. Original studies including individuals exposed to kala-azar with an evaluation of their nutritional status were included. Of the 1,261 records identified, five studies met the inclusion criteria, comprising four cohort studies and one case-control study. Four studies evaluated the association between malnutrition and clinical disease, and one evaluated the association with asymptomatic infection. Only two studies demonstrated a statistically significant association between malnutrition and kala-azar. A meta-analysis was conducted with two studies using R Studio software. The relative risk found was higher for malnourished individuals, although without statistical significance, possibly due to the high heterogeneity among the studies. A higher risk of kala-azar was observed in malnourished children, although without statistical concordance among findings. The methodological quality of the studies was considered low, with a high risk of bias, especially regarding the classification between primary and secondary malnutrition. It is concluded that there is evidence suggesting an association between malnutrition and kala-azar, but it is not possible to affirm this causal relationship with certainty. Further studies with greater methodological rigor, longer follow-up, and larger sample sizes are needed to confirm whether malnutrition modifies the risk of developing kala-azar.