Community-wide Prevalence of Malaria Parasitemia in HIV-Infected and Uninfected Populations in a High-Transmission Setting in Uganda

Katrak, Shereen; Day, Nathan; Ssemmondo, Emmanuel; Kwarisiima, Dalsone; Midekisa, Alemayehu; Greenhouse, Bryan; Kamya, Moses R.; Havlir, Diane V.; Dorsey, Grant

doi:10.1093/infdis/jiw057

Cited by 15 publications

(19 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These data demonstrate that the prevalence of parasitaemia increases as children age and then declines in adulthood. This is a well described trend in malaria epidemiology [ 15 ], and consistent with previously published reports in this region [ 10 , 11 , 16 ]. However, differences in age trends emerged when sub-microscopic parasitaemia was considered in addition to microscopic parasitaemia.…”

Section: Discussionsupporting

confidence: 91%

Characterizing microscopic and submicroscopic malaria parasitaemia at three sites with varied transmission intensity in Uganda

Rek

Katrak

Obasi

et al. 2016

Malar J

Self Cite

View full text Add to dashboard Cite

BackgroundParasite prevalence is a key metric used to quantify the burden of malaria and assess the impact of control strategies. Most published estimates of parasite prevalence are based on microscopy and likely underestimate true prevalence.MethodsThick smear microscopy was performed in cohorts of children (aged 6 month to 10 years) and adults every 90 days over 2 years, at three sites of varying transmission intensity in Uganda. Microscopy-negative samples were tested for sub-microscopic parasitaemia using loop-mediated isothermal amplification (LAMP). Generalized estimating equation models were used to evaluate associations between age and parasitaemia, factors associated with sub-microscopic infection and associations between parasitaemia and haemoglobin.ResultsA total of 9260 samples were collected from 1245 participants. Parasite prevalence among children across the three sites was 7.4, 9.4 and 28.8 % by microscopy and 21.3, 31.8 and 69.0 % by microscopy plus LAMP. Parasite prevalence among adults across the three sites was 3.1, 3.0 and 5.2 % by microscopy and 18.8, 24.2 and 53.5 % by microscopy plus LAMP. Among those with parasitaemia, adults and persons recently treated with anti-malarial therapy had the highest prevalence of sub-microscopic infection. Children with sub-microscopic or microscopic parasitaemia had lower mean haemoglobin levels compared to children with no detectable parasites.ConclusionsAcross a range of transmission intensities in Uganda, microscopy vastly underestimated parasite prevalence, especially among adults.

show abstract

Section: Discussionsupporting

confidence: 91%

Characterizing microscopic and submicroscopic malaria parasitaemia at three sites with varied transmission intensity in Uganda

Rek

Katrak

Obasi

et al. 2016

Malar J

Self Cite

View full text Add to dashboard Cite

show abstract

“…A greater proportion of older children harbored asymptomatic parasites (either microscopic or submicroscopic) compared to those who were younger which may be indicative of naturally acquired immunity. This is consistent with reports showing increased asymptomatic parasitaemia prevalence with age and a later decline in adulthood (22,(26)(27)(28)(29). Several factors may account for this observation including increased use of long lasting insecticide treated nets in the younger age group children (30) and the higher likelihood of they getting earlier treatment once infected compared to older children.…”

Section: Downloaded Fromsupporting

confidence: 91%

Microscopic and Submicroscopic Asymptomatic Plasmodium falciparum Infections in Ghanaian Children and Protection against Febrile Malaria

et al. 2020

View full text Add to dashboard Cite

Naturally acquired immunity to Plasmodium falciparum malaria is thought to be non-sterile and sustained by persistence of low level parasitaemia. This study assessed the association between baseline microscopic and submicroscopic asymptomatic P. falciparum infections and anti-malarial antibody levels and whether these parasitaemia modify protective associations between antibody levels and malaria in Ghanaian children. Healthy children (N=973, aged 0.5-12 years) were recruited into a 50-week longitudinal malaria cohort study from January 2016 to January 2017. Baseline asymptomatic parasitaemia were determined by microscopy (microscopic parasitaemia) and polymerase chain reaction (submicroscopic parasitaemia) and antibody levels against crude schizont antigens measured by ELISA. Antibody levels, parasite diversity and risk of malaria in the ensuing transmission season were compared among children who had baseline asymptomatic microscopic or submicroscopic or no P. falciparum infections. Of the 99 asymptomatic baseline infections, 46 (46.5%) were microscopic and 53 (53.5%), submicroscopic. Cox regression analysis adjusting for age group, sex and community found a strong association between both baseline microscopic [Hazard ratio (HR)=0.36, 95%CI=(0.21, 0.63), p<0.001] and submicroscopic [HR=0.22, 95%CI=(0.11, 0.44), p<0.001] asymptomatic parasitaemia and a reduced risk of febrile malaria compared to those who were uninfected at baseline. Baseline asymptomatic submicroscopic parasitaemia had a significant effect on associations between anti-schizont antibodies and protection against febrile malaria (likelihood ratio test p<0.001). The study found both baseline P. falciparum asymptomatic microscopic and more strongly submicroscopic infections to be associated with protection against febrile malaria in the ensuing transmission season. This could have important implications for malaria sero-epidemiological studies and vaccine trials.

show abstract

“…Given the intrinsic reactivity of Vδ2 T cells to P. falciparum and their direct anti-merozoite effects in vitro , we speculate that these cells may play a beneficial role as ready-made effectors during primary acute malaria infection of infants and young children, before the development of an effective adaptive immune response 41 . Although the progressive loss and dysfunction of these cells with repeated exposure is associated with reduced symptoms, it may conceivably interfere with effective clearance of the infection in childhood, contributing to rising parasite prevalence with increasing age in high transmission settings 5 , 8 , 42 . Although individuals rarely if ever develop sterilizing immunity that prevents any infection, control of blood-stage parasite density improves with increasing age, which we speculate may be due to the eventual development of adaptive immune responses, including antibodies, that develop with repeated exposure.…”

Section: Discussionmentioning

confidence: 99%

“…they are protected against symptoms) 3 – 5 , but they commonly harbor parasites as asymptomatic and transmitting carriers 6 , 7 . Although individuals generally do not appear to develop sterilizing immunity that prevents any infection, blood-stage parasite density declines with age and repeated exposure 8 , suggesting the development of immune responses that are able to limit blood stage replication. Importantly, pro-inflammatory responses that limit parasitemia may also lead to clinical symptoms; thus, ‘clinical’ immunity could depend upon the ability to down-modulate such responses, as suggested by recent data from our group and others 9 – 11 .…”

Section: Introductionmentioning

confidence: 99%

Vδ2+ T cell response to malaria correlates with protection from infection but is attenuated with repeated exposure

Jagannathan

Lutwama

Boyle

et al. 2017

Sci Rep

Self Cite

View full text Add to dashboard Cite

Vδ2+ γδ T cells are semi-innate T cells that expand markedly following P. falciparum (Pf) infection in naïve adults, but are lost and become dysfunctional among children repeatedly exposed to malaria. The role of these cells in mediating clinical immunity (i.e. protection against symptoms) to malaria remains unclear. We measured Vδ2+ T cell absolute counts at acute and convalescent malaria timepoints (n = 43), and Vδ2+ counts, cellular phenotype, and cytokine production following in vitro stimulation at asymptomatic visits (n = 377), among children aged 6 months to 10 years living in Uganda. Increasing age was associated with diminished in vivo expansion following malaria, and lower Vδ2 absolute counts overall, among children living in a high transmission setting. Microscopic parasitemia and expression of the immunoregulatory markers Tim-3 and CD57 were associated with diminished Vδ2+ T cell pro-inflammatory cytokine production. Higher Vδ2 pro-inflammatory cytokine production was associated with protection from subsequent Pf infection, but also with an increased odds of symptoms once infected. Vδ2+ T cells may play a role in preventing malaria infection in children living in endemic settings; progressive loss and dysfunction of these cells may represent a disease tolerance mechanism that contributes to the development of clinical immunity to malaria.

show abstract

Community-wide Prevalence of Malaria Parasitemia in HIV-Infected and Uninfected Populations in a High-Transmission Setting in Uganda

Cited by 15 publications

References 45 publications

Characterizing microscopic and submicroscopic malaria parasitaemia at three sites with varied transmission intensity in Uganda

Characterizing microscopic and submicroscopic malaria parasitaemia at three sites with varied transmission intensity in Uganda

Microscopic and Submicroscopic Asymptomatic Plasmodium falciparum Infections in Ghanaian Children and Protection against Febrile Malaria

Vδ2+ T cell response to malaria correlates with protection from infection but is attenuated with repeated exposure

Contact Info

Product

Resources

About