High Prevalence of Giardia duodenalis Assemblage B Infection and Association with Underweight in Rwandan Children

University of Pittsburgh, United States of America
PLoS Neglected Tropical Diseases (Impact Factor: 4.45). 06/2012; 6(6):e1677. DOI: 10.1371/journal.pntd.0001677
Source: PubMed


Giardia duodenalis is highly endemic in East Africa but its effects on child health, particularly of submicroscopic infections, i.e., those below the threshold of microscopy, and of genetic subgroups (assemblages), are not well understood. We aimed at addressing these questions and at examining epidemiological characteristics of G. duodenalis in southern highland Rwanda.
In 583 children <5 years of age from communities and health facilities, intestinal parasites were assessed by triplicate light microscopy and by PCR assays, and G. duodenalis assemblages were genotyped. Cluster effects of villages were taken into account in statistical analysis. The prevalence of G. duodenalis as detected by microscopy was 19.8% but 60.1% including PCR results. Prevalence differed with residence, increased with age, and was reduced by breastfeeding. In 492 community children without, with submicroscopic and with microscopic infection, underweight (weight-for-age z-score <-2 standard deviations) was observed in 19.7%, 22.1%, and 33.1%, respectively, and clinically assessed severe malnutrition in 4.5%, 9.5%, and 16.7%. Multivariate analysis identified microscopically detectable G. duodenalis infection as an independent predictor of underweight and clinically assessed severe malnutrition. Submicroscopic infection showed respective trends. Overall, G. duodenalis was not associated with gastrointestinal symptoms but assemblages A parasites (proportion, 13%) were increased among children with vomiting and abdominal pain.
The prevalence of G. duodenalis in high-endemicity areas may be greatly underestimated by light microscopy, particularly when only single stool samples are analysed. Children with submicroscopic infections show limited overt manifestation, but constitute unrecognized reservoirs of transmission. The predominance of assemblage B in Rwanda may be involved in the seemingly unimposing manifestation of G. duodenalis infection. However, the association with impaired child growth points to its actual relevance. Longitudinal studies considering abundant submicroscopic infections are needed to clarify the actual contribution of G. duodenalis to morbidity in areas of high endemicity.

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    • "The other 51 RT-PCR-negative samples were from age-and sexmatched children living in the same areas in Rwanda as the RT-PCR-positive children. Details of the previous study including the ethics statement and information regarding the RT-PCR assay used have been published before (Ignatius et al. 2012). "
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    • "Further progress in this field is hampered by the difficulty of culturing clinical samples [3]. Genotyping of Giardia for studies of epidemiology, symptomatology, virulence and drug resistance has therefore been limited to polymerase chain reaction (PCR) amplification and partial sequencing of one, or a few, specific genes [4] [5]. "
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    • "More recently, Ankarklev et al. reported a predominance of Assemblage B, followed by assemblage AII and by mixed assemblage infections of G. duodenalis among young children in Uganda [58]. In Rwanda, 85.9% of G. duodenalis-positive samples isolated from children were assemblage B and 12.7% were assemblage A2, in addition to one assemblage A1 and one mixed assemblage A+B [59]. In rural and in-hospital children in São Tomé island, anthroponotic assemblages A and B predominate, indicating person-to-person transmission plays an important role in giardiasis epidemiology. "
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