Plasmodium falciparum gametocyte sex ratios in symptomatic children treated with antimalarial drugs

Sowunmi, A.; Balogun, Sulayman Tunde; Gbotosho, Grace O.; Happi, Christian T.

doi:10.1016/j.actatropica.2008.10.010

Cited by 30 publications

(36 citation statements)

References 34 publications

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“…Considering that our time periods overlapped, this similarity was expected. The similar population sex ratios and breeding rates before and after the policy change suggest that ACTs had little or no effect on the gametocyte sex ratio in this endemic setting although ACTs tend to produce a female-biased sex ratio in the individual patients after treatment (Sowunmi et al 2007(Sowunmi et al , 2009a. The lack of the effect of ACTs on sex ratios and inbreeding rates would be expected since the individual patients receiving ACTs constitute a negligible portion of the parasite reservoir.…”

Section: Discussionmentioning

confidence: 85%

“…Patients enrolled in drug studies -Patients were recruited into antimalarial efficacy studies as described previously (Sowunmi et al 2009a), from January 2001-November 2010, at The Malaria Clinic of the University College Hospital in Ibadan, a malaria-endemic area in southwest Nigeria (Salako et al 1990). All patients with a presumptive diagnosis of malaria were evaluated for the presence of P. falciparum parasitaemia.…”

Section: Patients Materials and Methodsmentioning

confidence: 99%

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Plasmodium falciparum gametocyte carriage, sex ratios and asexual parasite rates in Nigerian children before and after a treatment protocol policy change instituting the use of artemisinin-based combination therapies

Gbotosho

Sowunmi

Happi

et al. 2011

Mem. Inst. Oswaldo Cruz

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The effects of artemisinin-based combination therapies (ACTs) on transmission of Plasmodium falciparum were evaluated after a policy change instituting the use of ACTs in an endemic area. P. falciparum gametocyte carriage, sex ratios and inbreeding rates were examined in 2,585 children at presentation with acute falciparum malaria during a 10-year period from 2001-2010. Asexual parasite rates were also evaluated from 2003-2010 in 10,615 children before and after the policy change. Gametocyte carriage declined significantly from 12.4% in 2001 to 3.6% in 2010 (@@χ2 for trend = 44.3, p < 0.0001), but sex ratios and inbreeding rates remained unchanged. Additionally, overall parasite rates remained unchanged before and after the policy change (47.2% vs. 45.4%), but these rates declined significantly from 2003-2010 (@@χ2 for trend 35.4, p < 0.0001). Chloroquine (CQ) and artemether-lumefantrine (AL) were used as prototype drugs before and after the policy change, respectively. AL significantly shortened the duration of male gametocyte carriage in individual patients after treatment began compared with CQ (log rank statistic = 7.92, p = 0.005). ACTs reduced the rate of gametocyte carriage in children with acute falciparum infections at presentation and shortened the duration of male gametocyte carriage after treatment. However, parasite population sex ratios, inbreeding rates and overall parasite rate were unaffected

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Section: Discussionmentioning

confidence: 85%

Section: Patients Materials and Methodsmentioning

confidence: 99%

Plasmodium falciparum gametocyte carriage, sex ratios and asexual parasite rates in Nigerian children before and after a treatment protocol policy change instituting the use of artemisinin-based combination therapies

Gbotosho

Sowunmi

Happi

et al. 2011

Mem. Inst. Oswaldo Cruz

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“…This rate is considerably lower than 40%, were a hematocrit less than 30% were used in this cohort of children. Our justification for the cut off was based on recent studies that showed a hematocrit less than 25% was a predictor of a male-biased PfGSR in malarious children from this endemic area [22]. Overall, the gametocyte carriage rate of 16% in anemic children was almost significantly higher than the 10% in the non-anemic group ( Table 2).…”

Section: Discussionmentioning

confidence: 99%

Influence of Anemia on Plasmodium falciparum Gametocyte Sex Ratios in Acutely Symptomatic Children

Sowunmi¹,

Balogun²,

Gbotosho³

et al. 2008

TOTMJ

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Anemia is common in African children but little is known about how malarial anemia influences Plasmodium falciparum gametocyte sex ratios (PfGSR) and transmission in endemic areas in Africa. We investigated the changes in PfGSR in 1126 consecutive children with acute, symptomatic, uncomplicated falciparum malaria who did (n = 99) or did not (n = 1027) have anemia (defined as a hematocrit < 25%) and who were treated with various antimalarial drugs in an endemic area of southwest Nigeria. On presentation, anemic children were significantly younger and had a significantly higher PfGSR (0.28 + 0.07 (se) v 0.15 + 0.02, P = 0.044). In anemic, but not in non-anemic children, a duration of illness > 3 d was associated with a male-biased sex ratio (defined as PfGSR > 0.5) (P = 0.029). Hematocrit correlated negatively with PfGSR in non-anemic but not in anemic children (r = -0.219, P = 0.027 and r = -0.106, P = 0.697, respectively) suggesting that the critical hematocrit producing 'all or none effect' on PfGSR was a value below 25% in this cohort of children. Temporal changes showed that, in general, in anemic children, PfGSR was significantly higher at enrolment than in non-anemic children treated with chloroquine (CQ), amodiaquine (AQ) and amodiaquine-sulfalene-pyrimethamine (ASP) (P < 0.0007 in all cases), and remained significantly higher by day 7 or 14 in those treated with AQ and pyrimethaminesulfadoxine plus probenecid (PSP) (P < 0.007 in all cases). In children who received the same treatment, the ratio of the sex specific half-life male:female, the 'gametocyte maleness index', was one and a half to two folds higher in anemic than non-anemic children suggesting anemia prolongs the survival of microgametocytes and may encourage transmission. These findings have implications for malaria control efforts in endemic sub-Saharan countries where malarial anemia is common.

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“…Although competition from other parasite genotypes was not evaluated in the present study, a less female-biased SR was observed in anaemic children when compared to non-anaemic children during follow-up. The possible reasons for this observation are as follows: an increased erythropoietin (EPO) secretion and release in anaemic children [in lower animals, increased (EPO) in secretion in response to anaemia is associated with a less female-biased sex allocation] (Paul et al 2000) and a blunting of the tendency of ACTs to selectively favour the emergence of a female-biased SR following treatment (Sowunmi et al 2007(Sowunmi et al , 2009a. In the latter context, further exploration of the interaction(s) between anaemia and ACT treatment on SR is urgently needed.…”

Section: Discussionmentioning

confidence: 99%

“…This interplay may be perturbed by antimalarial drugs used for therapy (Sowunmi et al 2009a) or host immunity. It is currently unclear how P. falciparum malaria-associated anaemia influences these processes and how the condition impacts the gametocyte SR in malarious children undergoing therapy with artemisinins or artemisinin-based combination therapies (ACTs).…”

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confidence: 99%

Plasmodium falciparum gametocyte carriage, emergence, clearance and population sex ratios in anaemic and non-anaemic malarious children

Gbotosho¹,

Sowunmi²,

Dokunmu³

et al. 2011

Mem. Inst. Oswaldo Cruz

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Anaemia in falciparum malaria is associated with an increased risk of gametocyte carriage, but its effects on transmission have not been extensively evaluated in malarious children. Plasmodium falciparum gametocyte carriage, emergence, clearance, population sex ratios (SR) (defined as the proportion of gametocytes that are male), inbreeding rates and temporal changes in SR were evaluated in 840 malarious children. Gametocyte carriage pre-treatment was at a level of 8.1%. Anaemia at enrolment was an independent risk factor for gametocyte carriage post-treatment. The emergence of gametocytes seven days post-treatment was significantly more frequent in anaemic children (7/106 vs. 10/696, p = 0.002). In the initially detected gametocytes, the proportion of children with a male-biased SR (MBSR) (> 0.5) was significantly higher in anaemic children (6/7 vs. 3/10, p = 0.027). Pre-treatment SR and estimated inbreeding rates (proportion of a mother's daughters fertilised by her sons) were similar in anaemic and non-anaemic children. Pre-treatment SR became more female-biased in non-anaemic children following treatment. However, in anaemic children, SR became male-biased. Anaemia was shown to significantly increase gametocyte emergence and may significantly alter the SR of emerging gametocytes. If MBSR is more infective to mosquitoes at low gametocytaemia, then these findings may have significant implications for malaria control efforts in endemic settings where malaria-associated anaemia is common

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Plasmodium falciparum gametocyte sex ratios in symptomatic children treated with antimalarial drugs

Cited by 30 publications

References 34 publications

Plasmodium falciparum gametocyte carriage, sex ratios and asexual parasite rates in Nigerian children before and after a treatment protocol policy change instituting the use of artemisinin-based combination therapies

Plasmodium falciparum gametocyte carriage, sex ratios and asexual parasite rates in Nigerian children before and after a treatment protocol policy change instituting the use of artemisinin-based combination therapies

Influence of Anemia on Plasmodium falciparum Gametocyte Sex Ratios in Acutely Symptomatic Children

Plasmodium falciparum gametocyte carriage, emergence, clearance and population sex ratios in anaemic and non-anaemic malarious children

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