Impact of hookworm infection and preventive chemotherapy on haemoglobin in non‐pregnant populations

Byrne, Aisling; Manalo, Giselle; Clarke, Naomi E.; Nery, Susana Vaz

doi:10.1111/tmi.13681

“…The latter is mainly governed by the scale parameter σ of the Hb distribution, defined to be equal for both groups of infected and not infected individuals, thus reflecting an underlying prevalence of anaemia due to other causes in the total population. This approach finds support from a recently published systematic review and meta-analysis [ 28 ] which showed that the intensity of hookworm infection and the influence of other sources on the risk of anaemia drive differences in mean Hb concentrations, in hookworm endemic settings.…”

Section: Discussionmentioning

confidence: 83%

“…In addition, a single KK slide may be sufficient for assessing this morbidity target. Further studies are needed to elucidate Hb dynamics pre- and post- mass drug administration, where the infection harbouring time plays an important role [ 28 ], ideally using longitudinal data collected in both children and adults.…”

Section: Discussionmentioning

confidence: 99%

Appropriateness of the current parasitological control target for hookworm morbidity: A statistical analysis of individual-level data

Malizia

¹

,

Giardina

²

,

Vlas

³

et al. 2022

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Background Soil-transmitted helminths affect almost 2 billion people globally. Hookworm species contribute to most of the related morbidity. Hookworms mainly cause anaemia, due to blood loss at the site of the attachment of the adult worms to the human intestinal mucosa. The World Health Organization (WHO) aims to eliminate hookworm morbidity by 2030 through achieving a prevalence of moderate and heavy intensity (M&HI) infections below 2%. In this paper, we aim to assess the suitability of this threshold to reflect hookworm-attributable morbidity. Methodology/Principal findings We developed a hierarchical statistical model to simulate individual haemoglobin concentrations in association with hookworm burdens, accounting for low haemoglobin values attributable to other causes. The model was fitted to individual-level data within a Bayesian framework. Then, we generated different endemicity settings corresponding to infection prevalence ranging from 10% to 90% (0% to 55% M&HI prevalence), using 1, 2 or 4 Kato-Katz slides. For each scenario, we estimated the prevalence of anaemia due to hookworm. Our results showed that on average, haemoglobin falls below the WHO threshold for anaemia when intensities are above 2000 eggs per gram of faeces. For the different simulated scenarios, the estimated prevalence of anaemia attributable to hookworm ranges from 0% to 30% (95%-PI: 24% - 36%) being mainly associated to the prevalence of M&HI infections. Simulations show that a 2% prevalence of M&HI infections in adults corresponds to a prevalence of hookworm-attributable anaemia lower than 1%. Conclusions/Significance Our results support the use of the current WHO thresholds of 2% prevalence of M&HI as a proxy for hookworm morbidity. A single Kato-Katz slide may be sufficient to assess the achievement of the morbidity target. Further studies are needed to elucidate haemoglobin dynamics pre- and post- control, ideally using longitudinal data in adults and children.

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“…In our model we accounted for an underlying prevalence of anaemia due to other causes such as nutritional factors or other infectious diseases, by explicitly modelling individual Hb variation. This approach finds support from a recently published systematic review and meta-analysis [24] which showed that the intensity of hookworm infection and the influence of other sources on the risk of anaemia drive differences in mean Hb concentrations, in hookworm endemic settings.…”

Section: Discussionmentioning

confidence: 83%

“…In addition, a single KK slide may be sufficient for assessing this morbidity target. Further studies are needed to elucidate Hb dynamics pre- and post-mass drug administration, where the infection harbouring time plays a crucial role [24], ideally using longitudinal data collected in both children and adults.…”

Section: Discussionmentioning

confidence: 99%

Appropriateness of the current parasitological control target for hookworm morbidity: a statistical analysis of individual-level data

Malizia

¹

,

Giardina

²

,

Vlas

³

et al. 2022

Preprint

1

0

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BackgroundSoil-transmitted helminths affect almost 2 billion people globally. Hookworm species contribute to most of the related morbidity. Hookworms mainly cause anaemia, due to blood loss at the site of the attachment of the adult worms to the human intestinal mucosa. The World Health Organization (WHO) aims to eliminate hookworm morbidity by 2030 through achieving a prevalence of moderate and heavy intensity (M&HI) infections below 2%. In this paper, we aim to assess the suitability of this threshold to reflect hookworm-attributable morbidity.Methodology/Principal FindingsWe developed a hierarchical statistical model to simulate individual haemoglobin concentrations in association with hookworm burdens, accounting for low haemoglobin values attributable to other causes. The model was fitted to individual-level data within a Bayesian framework. Then, we generated different endemicity settings corresponding to infection prevalence ranging from 10% to 90% (0% to 55% M&HI prevalence), using 1, 2 or 4 Kato-Katz slides. For each scenario, we estimated the prevalence of anaemia due to hookworm. Our results showed that on average, haemoglobin falls below the WHO threshold for anaemia when intensities are above 2000 eggs per gram of faeces. For the different simulated scenarios, the estimated prevalence of anaemia attributable to hookworm ranges from 0% to 30% (95%-PI: 24% - 36%) being mainly associated to the prevalence of M&HI infections. Simulations show that a 2% prevalence of M&HI infections in adults corresponds to a prevalence of hookworm-attributable anaemia lower than 1%.Conclusions/SignificanceOur results support the use of the current WHO thresholds of 2% prevalence of M&HI as a proxy for hookworm morbidity. A single Kato-Katz slide may be sufficient to assess the achievement of the morbidity target. Further studies are needed to elucidate haemoglobin dynamics pre- and post-control, ideally using longitudinal data in adults and children.Author summarySoil-transmitted helminths affect almost 2 billion people globally. About 65% of the related morbidity is attributable to hookworm infection, especially anaemia, which is caused by adult worms attaching to the intestinal mucosa of the human host to feed on blood. The World Health Organization (WHO) defines the target for the elimination of morbidity as reaching moderate-to-heavy intensity infections prevalence < 2%. In this paper, we aim to assess the suitability of the current WHO threshold to reflect hookworm-attributable anaemia. To this end, we developed a statistical model to simulate individual haemoglobin concentrations in association with hookworm burdens in adults, accounting for low haemoglobin values attributable to other causes, such as malnutrition and malaria. We used model outcomes to estimate the prevalence of hookworm-attributable anaemia in different endemicity scenarios. Our predictions suggested that anaemia is mainly associated to moderate-to-heavy intensity infection and that the 2% threshold corresponds to a prevalence of hookworm-attributable anaemia <1%. These results support the use of the current WHO threshold as a proxy for hookworm morbidity. Our predictions represent a first step towards better quantifying the prevalence of anaemia due to hookworm infection.

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“…A more recent systematic review of preventive chemotherapy in nonpregnant populations (preschool‐aged children, school‐aged children, adult males, and nonpregnant adult females) found that preventive chemotherapy increases hemoglobin concentrations, although the impact varied by medication, with albendazole increasing hemoglobin by 3.02 g/L and mebendazole not having an effect 60 . Coadministration of albendazole with praziquantel or with iron supplements did not appear to enhance the effect on hemoglobin.…”

Section: Who‐recommended Preventive Interventions For Anemiamentioning

confidence: 96%

Review of intervention products for use in the prevention and control of anemia

Lopez de Romaña,

Mildon,

Golan

et al. 2023

Annals of the New York Academy of Sciences

5

0

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Anemia remains a major public health problem, especially in low‐ and middle‐income countries. The World Health Organization recommends several interventions to prevent and manage anemia in vulnerable population groups, including young children, menstruating adolescent girls and women, and pregnant and postpartum women. Daily iron supplementation reduces the risk of anemia in infants, children, and pregnant women, and intermittent iron supplementation reduces anemia risk in menstruating girls and women. Micronutrient powders reduce the risk of anemia in children. Fortifying wheat flour with iron reduces the risk of anemia in the overall population, whereas the effect of fortifying maize flour and rice is still uncertain. Regarding non‐nutrition‐related interventions, malaria treatment and deworming have been reported to decrease anemia prevalence. Promising interventions to prevent anemia include vitamin A supplementation, multiple micronutrient supplementation for pregnant women, small‐quantity lipid‐based supplements, and fortification of salt with iodine and iron. Future research could address the efficacy and safety of different iron supplementation formulations, identify the most bioavailable form of iron for fortification, examine adherence to supplementation regimens and fortification standards, and investigate the effectiveness of integrating micronutrient, helminth, and malaria control programs.

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Impact of hookworm infection and preventive chemotherapy on haemoglobin in non‐pregnant populations

Cited by 6 publications

References 52 publications

Appropriateness of the current parasitological control target for hookworm morbidity: A statistical analysis of individual-level data

Appropriateness of the current parasitological control target for hookworm morbidity: A statistical analysis of individual-level data

Appropriateness of the current parasitological control target for hookworm morbidity: a statistical analysis of individual-level data

Review of intervention products for use in the prevention and control of anemia

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