Peter Ouma

Publications (9)21.92 Total impact

• Source

  Available from: Nnaemeka C. Iriemenam

  Article: Temporal trends of sulphadoxine-pyrimethamine (SP) drug-resistance molecular markers in Plasmodium falciparum parasites from pregnant women in western Kenya.

  Nnaemeka C Iriemenam, Monica Shah, Wangeci Gatei, Anna M van Eijk, John Ayisi, Simon Kariuki, Jodi Vanden Eng, Simon O Owino, Ashima A Lal, Yusuf O Omosun, Kephas Otieno, Meghna Desai, Feiko O ter Kuile, Bernard Nahlen, Julie Moore, Mary J Hamel, Peter Ouma, Laurence Slutsker, Ya Ping Shi
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  ABSTRACT: Resistance to sulphadoxine-pyrimethamine (SP) in Plasmodium falciparum parasites is associated with mutations in the dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) genes and has spread worldwide. SP remains the recommended drug for intermittent preventive treatment for malaria in pregnancy (IPTp) and information on population prevalence of the SP resistance molecular markers in pregnant women is limited. Temporal trends of SP resistance molecular markers were investigated in 489 parasite samples collected from pregnant women at delivery from three different observational studies between 1996 and 2009 in Kenya, where SP was adopted for both IPTp and case treatment policies in 1998. Using real-time polymerase chain reaction, pyrosequencing and direct sequencing, 10 single-nucleotide polymorphisms (SNPs) of SP resistance molecular markers were assayed. The prevalence of quintuple mutant (dhfr N51I/C59R/S108N and dhps A437G/K540E combined genotype) increased from 7% in the first study (1996-2000) to 88% in the third study (2008-2009). When further stratified by sample collection year and adoption of IPTp policy, the prevalence of the quintuple mutant increased from 2.4% in 1998 to 44.4% three years after IPTp policy adoption, seemingly in parallel with the increase in percentage of SP use in pregnancy. However, in the 1996-2000 study, more mutations in the combined dhfr/dhps genotype were associated with SP use during pregnancy only in univariable analysis and no associations were detected in the 2002-2008 and 2008-2009 studies. In addition, in the 2008-2009 study, 5.3% of the parasite samples carried the dhps triple mutant (A437G/K540E/A581G). There were no differences in the prevalence of SP mutant genotypes between the parasite samples from HIV + and HIV- women over time and between paired peripheral and placental samples. There was a significant increase in dhfr/dhps quintuple mutant and the emergence of new genotype containing dhps 581 in the parasites from pregnant women in western Kenya over 13 years. IPTp adoption and SP use in pregnancy only played a minor role in the increased drug-resistant parasites in the pregnant women over time. Most likely, other major factors, such as the high prevalence of resistant parasites selected by the use of SP for case management in large non-pregnant population, might have contributed to the temporally increased prevalence of SP resistant parasites in pregnant women. Further investigations are needed to determine the linkage between SP drug resistance markers and efficacy of IPTp-SP.
  Malaria Journal 04/2012; 11:134. · 3.19 Impact Factor
• Article: Antenatal and delivery care in rural western Kenya: the effect of training health care workers to provide "focused antenatal care"

  Peter Ouma, van Eijk Anna, Mary Hamel, Evallyne Sikuku, Frank Odhiambo, Kaendi Munguti, John Ayisi, Sara Crawford, Piet Kager, Laurence Slutsker
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  ABSTRACT: Abstract Background Maternal mortality remains high in developing countries and data to monitor indicators of progress in maternal care is needed. We examined the status of maternal care before and after health care worker (HCW) training in WHO recommended Focused Antenatal Care. Methods An initial cross-sectional survey was conducted in 2002 in Asembo and Gem in western Kenya among a representative sample of women with a recent birth. HCW training was performed in 2003 in Asembo, and a repeat survey was conducted in 2005 in both areas. Results Antenatal clinic (ANC) attendance was similar in both areas (86%) in 2005 and not significantly different from 2002 (90%). There was no difference in place of delivery between the areas or over time. However, in 2005, more women in Asembo were delivered by a skilled assistant compared to Gem (30% vs.23%, P = 0.04), and this proportion increased compared to 2002 (17.6% and 16.1%, respectively). Provision of iron (82.4%), folic acid (72.0%), sulfadoxine-pyrimethamine (61.7%), and anthelminths (12.7%) had increased in Asembo compared to 2002 (2002: 53.3%, 52.8%, 20.3%, and 4.6%, respectively), and was significantly higher than in Gem in 2005 (Gem 2005: 69.7%, 47.8%, 19.8%, and 4.1%, respectively) (P < 0.05 for all). Offering of tests for sexually transmitted diseases and providing information related to maternal health was overall low (<20%) and did not differ by area. In 2005, more women rated the quality of the antenatal service in Asembo as very satisfactory compared to Gem (17% vs. 6.5%, P < 0.05). Conclusions We observed improvements in some ANC services in the area where HCWs were trained. However, since our evaluation was carried out 2 years after three-day training, we consider any significant, sustained improvement to be remarkable.
  Reproductive Health. 01/2010;
• Article: Does cotrimoxazole prophylaxis for the prevention of HIV-associated opportunistic infections select for resistant pathogens in Kenyan adults?

  Mary J Hamel, Carolyn Greene, Tom Chiller, Peter Ouma, Christina Polyak, Kephas Otieno, John Williamson, Ya Ping Shi, Daniel R Feikin, Barbara Marston, John T Brooks, Amanda Poe, Zhiyong Zhou, Benjamin Ochieng, Eric Mintz, Laurence Slutsker
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  ABSTRACT: We assessed the effect of daily cotrimoxazole, essential for HIV care, on development of antifolate-resistant Plasmodium falciparum, naso-pharyngeal Streptococcus pneumoniae (pneumococcus), and commensal Escherichia coli. HIV-positive subjects with CD4 cell count < 350 cells/muL (lower-CD4; N = 692) received cotrimoxazole; HIV-positive with CD4 cell count > or = 350 cells/muL (higher-CD4; N = 336) and HIV-negative subjects (N = 132) received multivitamins. Specimens were collected at baseline, 2 weeks, monthly, and at sick visits during 6 months of follow-up to compare changes in resistance, with higher-CD4 as referent. P. falciparum parasitemia incidence density was 16 and 156/100 person-years in lower-CD4 and higher-CD4, respectively (adjusted rate ratio [ARR] = 0.11; 95% confidence interval [CI] = 0.06-0.15; P < 0.001) and 97/100 person-years in HIV-negative subjects (ARR = 0.62; 95% CI = 0.44-0.86; P = 005). Incidence density of triple and quintuple dihydrofolate-reductase/dihydropteroate-synthetase mutations was 90% reduced in lower-CD4 compared with referent. Overall, cotrimoxazole non-susceptibility was high among isolated pneumococcus (92%) and E. coli (76%) and increased significantly in lower-CD4 subjects by Week 2 (P < 0.005). Daily cotrimoxazole prevented malaria and reduced incidence of antifolate-resistant P. falciparum but contributed to increased pneumococcus and commensal Escherichia coli resistance.
  The American journal of tropical medicine and hygiene 10/2008; 79(3):320-30. · 2.59 Impact Factor
• Article: Dihydrofolate reductase I164L mutations in Plasmodium falciparum isolates: clinical outcome of 14 Kenyan adults infected with parasites harbouring the I164L mutation.

  Mary J Hamel, Amanda Poe, Peter Bloland, Andrea McCollum, Zhiyong Zhou, Ya Ping Shi, Peter Ouma, Kephas Otieno, John Vulule, Ananias Escalante, Venkatachalam Udhayakumar, Laurence Slutsker
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  ABSTRACT: Recently, Plasmodium falciparum bearing dihydrofolate reductase (DHFR) I164L was isolated from Africa. Quadruple mutations containing I164L confer high-level resistance to antifolate antimalarials. We prospectively measured the effect of co-trimoxazole (CTX) prophylaxis on P. falciparum antifolate resistance development among HIV-infected persons. HIV-positive patients with CD4 cell count < 350 cells/microl (n=692) received CTX; HIV-positive patients with CD4 cell count > or = 350 cells/microl (n=336) and HIV-negative patients (n=132) received multivitamins. Malaria microscopy-positive samples (n=413) and selected microscopy-negative/PCR-positive samples (n=76) were analysed for DHFR mutations at baseline and during six months follow up. We identified I164L in 14 patients. Seven were malaria microscopy-positive: two failed sulfadoxine-pyrimethamine (SP). Among seven microscopy-negative/PCR-positive patients, none developed patent infections with I164L. I164L was not associated with high-level SP resistance or poor outcome among adults living where malaria is highly endemic. Surveillance to monitor spread of I164L is critical, especially among children and pregnant women, who are potentially a source for I164L amplification.
  Transactions of the Royal Society of Tropical Medicine and Hygiene 05/2008; 102(4):338-45. · 2.16 Impact Factor
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  Available from: kit.nl

  Article: Malaria and anaemia among pregnant women at first antenatal clinic visit in Kisumu, western Kenya.

  Peter Ouma, Anna M van Eijk, Mary J Hamel, Monica Parise, John G Ayisi, Kephas Otieno, Piet A Kager, Laurence Slutsker
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  ABSTRACT: To determine the prevalence of malaria and anaemia among urban and peri-urban women attending their first antenatal clinic (ANC) in an area of perennial malaria transmission. Between November 2003 and May 2004 we screened first ANC attenders for malaria and anaemia in a large urban hospital in Kisumu (western Kenya) and interviewed them to obtain demographic and medical information. Among the 685 study participants, prevalence of malaria parasitaemia was 18.0%, prevalence of any anaemia (haemoglobin < 11 g/dl) was 69.1% and prevalence of moderate anaemia was (haemoglobin < 8 g/dl) 11.8%. Sixteen women were hospitalized during pregnancy, eight because of malaria. In multivariate analysis, young age, living in a house with mud walls, a visit to rural area, peri-urban residence, second trimester of pregnancy and Luo ethnicity were significant risk factors for malaria parasitaemia. Malaria was an important risk factor for any and moderate anaemia; use of an insecticide-treated net (ITN) was a protective factor for any anaemia. Married women with a higher level of education, better-quality housing and full-time employment were more likely to use an ITN. Malaria and anaemia are established problems by the time of the first ANC visit. Mechanisms to deliver ITNs to women of child-bearing age before they become pregnant need to be explored. Early ANC visits are warranted in order for women to benefit from policies aimed at reducing the burden of malaria and anaemia.
  Tropical Medicine & International Health 01/2008; 12(12):1515-23. · 2.80 Impact Factor
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  Available from: PubMed Central

  Article: Reproductive health issues in rural Western Kenya.

  Anna M van Eijk, Kim A Lindblade, Frank Odhiambo, Elizabeth Peterson, Evallyne Sikuku, John G Ayisi, Peter Ouma, Daniel H Rosen, Laurence Slutsker
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  ABSTRACT: We describe reproductive health issues among pregnant women in a rural area of Kenya with a high coverage of insecticide treated nets (ITNs) and high prevalence of HIV (15%). We conducted a community-based cross-sectional survey among rural pregnant women in western Kenya. A medical, obstetric and reproductive history was obtained. Blood was obtained for a malaria smear and haemoglobin level, and stool was examined for geohelminths. Height and weight were measured. Of 673 participants, 87% were multigravidae and 50% were in their third trimester; 41% had started antenatal clinic visits at the time of interview and 69% reported ITN-use. Malaria parasitemia and anaemia (haemoglobin < 11 g/dl) were detected among 36% and 53% of the women, respectively. Geohelminth infections were detected among 76% of the 390 women who gave a stool sample. Twenty percent of women were underweight, and sixteen percent reported symptoms of herpes zoster or oral thrush in the last two months. Nineteen percent of all women reported using a contraceptive method to delay or prevent pregnancy before the current pregnancy (injection 10%, pill 8%, condom 0.4%). Twenty-three percent of multigravidae conceived their current pregnancy within a year of the previous pregnancy. More than half of the multigravidae (55%) had ever lost a live born child and 21% had lost their last singleton live born child at the time of interview. In this rural area with a high HIV prevalence, the reported use of condoms before pregnancy was extremely low. Pregnancy health was not optimal with a high prevalence of malaria, geohelminth infections, anaemia and underweight. Chances of losing a child after birth were high. Multiple interventions are needed to improve reproductive health in this area.
  Reproductive Health 01/2008; 5:1.
• Article: Reproductive health issues in rural Western Kenya

  van Eijk Anna, Kim Lindblade, Frank Odhiambo, Elizabeth Peterson, Evallyne Sikuku, John Ayisi, Peter Ouma, Daniel Rosen, Laurence Slutsker
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  ABSTRACT: Abstract Background We describe reproductive health issues among pregnant women in a rural area of Kenya with a high coverage of insecticide treated nets (ITNs) and high prevalence of HIV (15%). Methods We conducted a community-based cross-sectional survey among rural pregnant women in western Kenya. A medical, obstetric and reproductive history was obtained. Blood was obtained for a malaria smear and haemoglobin level, and stool was examined for geohelminths. Height and weight were measured. Results Of 673 participants, 87% were multigravidae and 50% were in their third trimester; 41% had started antenatal clinic visits at the time of interview and 69% reported ITN-use. Malaria parasitemia and anaemia (haemoglobin < 11 g/dl) were detected among 36% and 53% of the women, respectively. Geohelminth infections were detected among 76% of the 390 women who gave a stool sample. Twenty percent of women were underweight, and sixteen percent reported symptoms of herpes zoster or oral thrush in the last two months. Nineteen percent of all women reported using a contraceptive method to delay or prevent pregnancy before the current pregnancy (injection 10%, pill 8%, condom 0.4%). Twenty-three percent of multigravidae conceived their current pregnancy within a year of the previous pregnancy. More than half of the multigravidae (55%) had ever lost a live born child and 21% had lost their last singleton live born child at the time of interview. Conclusion In this rural area with a high HIV prevalence, the reported use of condoms before pregnancy was extremely low. Pregnancy health was not optimal with a high prevalence of malaria, geohelminth infections, anaemia and underweight. Chances of losing a child after birth were high. Multiple interventions are needed to improve reproductive health in this area.
  Reproductive Health. 01/2008;
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  Available from: oxfordjournals.org

  Article: Antifolate resistance in Plasmodium falciparum: multiple origins and identification of novel dhfr alleles.

  Andrea M McCollum, Amanda C Poe, Mary Hamel, Curtis Huber, Zhiyong Zhou, Ya Ping Shi, Peter Ouma, John Vulule, Peter Bloland, Laurence Slutsker, John W Barnwell, Venkatachalam Udhayakumar, Ananias A Escalante
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  ABSTRACT: Sulfadoxine-pyrimethamine has been widely used as first-line therapy for uncomplicated malaria throughout sub-Saharan Africa. Recent studies conducted in Asia and Africa suggest the triple-mutant dhfr genotype (51I/59R/108N) may have been generated as a single event in Southeast Asia, with subsequent spread of the single lineage to the African continent, but this hypothesis needs further validation. Direct sequencing of polymerase chain reaction (PCR) products, pyrosequencing, and cloning of PCR products were utilized to identify mutations in dhfr. To investigate the evolutionary history of dhfr alleles, we assayed microsatellite loci flanking dhfr along chromosome 4. A total of 15 of 479 samples from western Kenya showed the presence of I164L, in 5 different genotypes. We document C50R in 2 of our samples. Using microsatellite markers, we show 2 haplotypes for both the 51I/108N/164L and 51I/59R/108N/164L genotypes. Our results also show multiple lineages for the triple-mutant dhfr genotype in Africa. These findings highlight the importance of local characterization of alleles before molecular surveillance of drug-resistant alleles is considered in different endemic settings and populations.
  The Journal of Infectious Diseases 08/2006; 194(2):189-97. · 6.41 Impact Factor
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  Available from: Feiko O ter Kuile

  Article: A randomized controlled trial of folate supplementation when treating malaria in pregnancy with sulfadoxine-pyrimethamine.

  Peter Ouma, Monica E Parise, Mary J Hamel, Feiko O Ter Kuile, Kephas Otieno, John G Ayisi, Piet A Kager, Richard W Steketee, Laurence Slutsker, Anna M van Eijk
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  ABSTRACT: Sulfadoxine-pyrimethamine (SP) is an antimalarial drug that acts on the folate metabolism of the malaria parasite. We investigated whether folate (FA) supplementation in a high or a low dose affects the efficacy of SP for the treatment of uncomplicated malaria in pregnant women. This was a randomized, placebo-controlled, double-blind trial. The trial was carried out at three hospitals in western Kenya. The participants were 488 pregnant women presenting at their first antenatal visit with uncomplicated malaria parasitaemia (density of >or= 500 parasites/microl), a haemoglobin level higher than 7 g/dl, a gestational age between 17 and 34 weeks, and no history of antimalarial or FA use, or sulfa allergy. A total of 415 women completed the study. All participants received SP and iron supplementation. They were randomized to the following arms: FA 5 mg, FA 0.4 mg, or FA placebo. After 14 days, all participants continued with FA 5 mg daily as per national guidelines. Participants were followed at days 2, 3, 7, 14, 21, and 28 or until treatment failure. The outcomes were SP failure rate and change in haemoglobin at day 14. The proportion of treatment failure at day 14 was 13.9% (19/137) in the placebo group, 14.5% (20/138) in the FA 0.4 mg arm (adjusted hazard ratio [AHR], 1.07; 98.7% confidence interval [CI], 0.48 to 2.37; p = 0.8), and 27.1% (38/140) in the FA 5 mg arm (AHR, 2.19; 98.7% CI, 1.09 to 4.40; p = 0.005). The haemoglobin levels at day 14 were not different relative to placebo (mean difference for FA 5 mg, 0.17 g/dl; 98.7% CI, -0.19 to 0.52; and for FA 0.4 mg, 0.14 g/dl; 98.7% CI, -0.21 to 0.49). Concomitant use of 5 mg FA supplementation compromises the efficacy of SP for the treatment of uncomplicated malaria in pregnant women. Countries that use SP for treatment or prevention of malaria in pregnancy need to evaluate their antenatal policy on timing or dose of FA supplementation.
  PLoS Clinical Trials 02/2006; 1(6):e28. · 4.77 Impact Factor