John G. Ayisi
Kenya Medical Research Institute
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by John G. Ayisi.
Reproductive Health | 2006
Anna M. van Eijk; Hanneke M Bles; Frank Odhiambo; John G. Ayisi; Ilse E Blokland; Daniel H. Rosen; Kubaje Adazu; Laurence Slutsker; Kim A. Lindblade
BackgroundImproving maternal health is one of the UN Millennium Development Goals. We assessed provision and use of antenatal services and delivery care among women in rural Kenya to determine whether women were receiving appropriate care.MethodsPopulation-based cross-sectional survey among women who had recently delivered.ResultsOf 635 participants, 90% visited the antenatal clinic (ANC) at least once during their last pregnancy (median number of visits 4). Most women (64%) first visited the ANC in the third trimester; a perceived lack of quality in the ANC was associated with a late first ANC visit (Odds ratio [OR] 1.5, 95% confidence interval [CI] 1.0–2.4). Women who did not visit an ANC were more likely to have < 8 years of education (adjusted OR [AOR] 3.0, 95% CI 1.5–6.0), and a low socio-economic status (SES) (AOR 2.8, 95% CI 1.5–5.3). The ANC provision of abdominal palpation, tetanus vaccination and weight measurement were high (>90%), but provision of other services was low, e.g. malaria prevention (21%), iron (53%) and folate (44%) supplementation, syphilis testing (19.4%) and health talks (14.4%). Eighty percent of women delivered outside a health facility; among these, traditional birth attendants assisted 42%, laypersons assisted 36%, while 22% received no assistance. Factors significantly associated with giving birth outside a health facility included: age ≥ 30 years, parity ≥ 5, low SES, < 8 years of education, and > 1 hour walking distance from the health facility. Women who delivered unassisted were more likely to be of parity ≥ 5 (AOR 5.7, 95% CI 2.8–11.6).ConclusionIn this rural area, usage of the ANC was high, but this opportunity to deliver important health services was not fully utilized. Use of professional delivery services was low, and almost 1 out of 5 women delivered unassisted. There is an urgent need to improve this dangerous situation.
Reproductive Health | 2010
Peter Ouma; Anna M. van Eijk; Mary J. Hamel; Evallyne S Sikuku; Frank Odhiambo; Kaendi M Munguti; John G. Ayisi; Sara Crawford; Piet A. Kager; Laurence Slutsker
BackgroundMaternal 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.MethodsAn 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.ResultsAntenatal 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).ConclusionsWe 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.
PLOS Medicine | 2007
Jessica Keen; Lena Serghides; Kodjo Ayi; Samir N. Patel; John G. Ayisi; Anne M. Van Eijk; Richard W. Steketee; Venkatachalam Udhayakumar; Kevin C. Kain
Background Primigravid (PG) women are at risk for pregnancy-associated malaria (PAM). Multigravid (MG) women acquire protection against PAM; however, HIV infection impairs this protective response. Protection against PAM is associated with the production of IgG specific for variant surface antigens (VSA-PAM) expressed by chondroitin sulfate A (CSA)-adhering parasitized erythrocytes (PEs). We hypothesized that VSA-PAM-specific IgG confers protection by promoting opsonic phagocytosis of PAM isolates and that HIV infection impairs this response. Methods and Findings We assessed the ability of VSA-PAM-specific IgG to promote opsonic phagocytosis of CSA-adhering PEs and the impact of HIV infection on this process. Opsonic phagocytosis assays were performed using the CSA-adherent parasite line CS2 and human and murine macrophages. CS2 PEs were opsonized with plasma or purified IgG subclasses from HIV-negative or HIV-infected PG and MG Kenyan women or sympatric men. Levels of IgG subclasses specific for VSA-PAM were compared in HIV-negative and HIV-infected women by flow cytometry. Plasma from HIV-negative MG women, but not PG women or men, promoted the opsonic phagocytosis of CSA-binding PEs (p < 0.001). This function depended on VSA-PAM-specific plasma IgG1 and IgG3. HIV-infected MG women had significantly lower plasma opsonizing activity (median phagocytic index 46 [interquartile range (IQR) 18–195] versus 251 [IQR 93–397], p = 0.006) and levels of VSA-PAM-specific IgG1 (mean fluorescence intensity [MFI] 13 [IQR 11–20] versus 30 [IQR 23–41], p < 0.001) and IgG3 (MFI 17 [IQR 14–23] versus 28 [IQR 23–37], p < 0.001) than their HIV-negative MG counterparts. Conclusions Opsonic phagocytosis may represent a novel correlate of protection against PAM. HIV infection may increase the susceptibility of multigravid women to PAM by impairing this clearance mechanism.
AIDS | 2003
Chunfu Yang; Ming Li; Robert D. Newman; Ya-Ping Shi; John G. Ayisi; Anna M. van Eijk; Juliana Otieno; Ambrose O. Misore; Richard W. Steketee; Bernard L. Nahlen; Renu B. Lal
Background: Little is known about the impact of HIV-1 group M subtypes on mother-to-child transmission (MTCT) of HIV-1 in African settings where multiple HIV-1 group M subtypes are co-circulating. Objective: To assess the role of subtype variation on MTCT. Methods: HIV-1-infected women attending an antenatal clinic in western Kenya were enrolled for a prospective study (1996–2000) of MTCT. HIV-1 subtype analysis of p24gag and gp41env identified potential recombinants, and their role in MTCT was determined. Results: Among 414 women for whom HIV-1 subtype and HIV transmission status were available, MTCT occurred in 80 (19.3%). MTCT rates were higher among women with subtype D compared with subtype A in either the gp41 region [31.6 versus 16.1%, relative risk (RR) 2.0, P = 0.002] or p24 region (29.9 versus 18.0%, RR 1.7, P = 0.02). Discordant subtype combinations were identified in 103 of the women (25.9%), and were associated with higher rates of MTCT (28.2 versus 17.0%, RR 1.7, P = 0.01). In multivariate analysis, women with subtype combinations D/D, D/A, and A/D had an increased risk of MTCT (adjusted odds ratios 3.5, 2.5, 6.2; P = 0.005, 0.05, and 0.0003, respectively) compared with A/A women after adjustment for maternal HIV viral load, placental malaria infection, episiotomy or perineal tear, and low birthweight. Conclusion: MTCT appears to be more common among mothers infected with subtype D compared with subtype A. Such differences in MTCT frequency may be caused by altered cellular tropism for placental cell types.
The Journal of Infectious Diseases | 2007
Michael D. Green; Annemieke M. van Eijk; Feiko O. ter Kuile; John G. Ayisi; Monica E. Parise; Piet A. Kager; Bernard L. Nahlen; Richard W. Steketee; Henry Nettey
BACKGROUND Sulfadoxine-pyrimethamine (SP) is among the most commonly used antimalarial drugs during pregnancy, yet the pharmacokinetics of SP are unknown in pregnant women. HIV-infected (HIV(+)) women require more frequent doses of intermittent preventive therapy with SP than do HIV-uninfected (HIV(-)) women. We investigated whether this reflects their impaired immunity or an HIV-associated alteration in the disposition of SP. METHODS Seventeen pregnant HIV(-) women and 16 pregnant HIV(+) women received a dose of 1500 mg of sulfadoxine and 75 mg of pyrimethamine. Five HIV(-) and 6 HIV(+) postpartum women returned 2-3 months after delivery for another dose. The pharmacokinetics of sulfadoxine and pyrimethamine were compared between these groups. RESULTS HIV status did not affect the area under the curve (AUC(0-->infinity)) or the half-lives of sulfadoxine or pyrimethamine in prepartum or postpartum women, although partum status did have a significant affect on sulfadoxine pharmacokinetics. Among prepartum women, the median half-life for sulfadoxine was significantly shorter than that observed in postpartum women (148 vs 256 h; P<.001), and the median AUC(0-->infinity) was ~40% lower (22,816 vs 40,106 microg/mL/h, P<.001). HIV status and partum status did not show any significant influence on pyrimethamine pharmacokinetics. CONCLUSION Pregnancy significantly modifies the disposition of SP, whereas HIV status has little influence on pharmacokinetic parameters in pregnant women.
Journal of Immunological Methods | 1997
J.M. Moore; Bernard L. Nahlen; A.V.O Ofulla; J Caba; John G. Ayisi; Aggrey J. Oloo; A Misore; A.J Nahmias; Altaf A. Lal; Venkatachalam Udhayakumar
A noninvasive perfusion method for the recovery of maternal placental (intervillous) blood for use in immunologic assays is described. 60% of the perfused blood samples tested for fetal red blood cell (RBC) contamination were found to be pure maternal blood; in the remainder, fetal RBC contamination, with a single exception, was less than 6%. The intervillous mononuclear cells (IVBMC) isolated from this blood were of predominantly maternal origin as demonstrated by a polymerase chain reaction-based DNA typing technique. The number of IVBMC obtained was within the range of 9 to 55 X 10(6) cells. Phenotypic analysis of IVBMC surface antigens revealed that 61% of the cells were CD3 + T-cells and 18% were CD19 + B-cells. The CD4 + and CD8 + T-lymphocyte subsets accounted for 28 and 26% of the IVBMC, respectively. The IVBMC were functionally competent as evidenced by in vitro lymphoproliferation and cytokine production in response to mitogen and PPD stimulation. This technique allows for rapid and safe isolation of large numbers of IVBMC which are functionally active up to 12 h post-delivery, thus representing a significant improvement over previously described methods. It should facilitate more vigorous research in the study of uteroplacental immunity and infectious disease research, particularly in field settings where sample collection and laboratory facilities are distant.
The Journal of Infectious Diseases | 2000
Julie M. Moore; John G. Ayisi; Bernard L. Nahlen; Ambrose O. Misore; Altaf A. Lal; Venkatachalam Udhayakumar
An association was demonstrated recently between elevated in vitro production of interferon (IFN)-gamma by intervillous blood mononuclear cells (IVBMCs) and protection against placental malaria (PM). Because human immunodeficiency virus (HIV)-infected pregnant women have increased susceptibility to PM, loss of the IFN-gamma response in these women may impair their ability to control PM. Measurement of cytokines in culture supernatants by ELISA revealed that IFN-gamma responses by HIV-positive IVBMCs were impaired, especially after malarial antigen stimulation. Interleukin (IL)-4 and IL-10 responses also were reduced in HIV-positive persons, the latter more so in HIV-positive, PM-positive persons. In contrast, tumor necrosis factor-alpha production generally was enhanced in PM-positive and HIV-positive persons. Overall, cytokine production was reduced in HIV-positive persons with CD4 T cell counts <500/microL, particularly in response to malarial antigen. Thus, HIV-mediated cytokine dysregulation and impairment of the protective IFN-gamma response may contribute to the increased susceptibility of HIV-positive pregnant women to malaria.
PLOS Neglected Tropical Diseases | 2009
Anna M. van Eijk; Kim A. Lindblade; Frank Odhiambo; Elizabeth Peterson; Daniel H. Rosen; Diana M. S. Karanja; John G. Ayisi; Ya Ping Shi; Kubaje Adazu; Laurence Slutsker
Background Geohelminth infections are common in rural western Kenya, but risk factors and effects among pregnant women are not clear. Methodology During a community-based cross-sectional survey, pregnant women were interviewed and asked to provide a blood sample and a single fecal sample. Hemoglobin was measured and a blood slide examined for malaria. Geohelminth infections were identified using the concentration and Kato-Katz method. Results Among 390 participants who provided a stool sample, 76.2% were infected with at least one geohelminth: 52.3% with Ascaris lumbricoides, 39.5% with hookworm, and 29.0% with Trichuris trichiura. Infection with at least one geohelminth species was associated with the use of an unprotected water source (adjusted odds ratio [AOR] 1.8, 95% confidence interval [CI] 1.1–3.0) and the lack of treatment of drinking water (AOR 1.8, 95% CI 1.1–3.1). Geohelminth infections were not associated with clinical symptoms, or low body mass index. A hookworm infection was associated with a lower mid upper arm circumference (adjusted mean decrease 0.7 cm, 95% CI 0.3–1.2 cm). Hookworm infections with an egg count ≥1000/gram feces (11 women) were associated with lower hemoglobin (adjusted mean decrease 1.5 g/dl, 95% CI 0.3–2.7). Among gravidae 2 and 3, women with A. lumbricoides were less likely to have malaria parasitemia (OR 0.4, 95% CI 0.2–0.8) compared to women without A. lumbricoides, unlike other gravidity groups. Conclusion Geohelminth infections are common in this pregnant population; however, there were few observed detrimental effects. Routine provision of antihelminth treatment during an antenatal clinic visit is recommended, but in this area an evaluation of the impact on pregnancy, malaria, and birth outcome is useful.
Malaria Journal | 2012
Nnaemeka C. Iriemenam; Monica P. Shah; Wangeci Gatei; Anna M. van Eijk; John G. Ayisi; Simon Kariuki; Jodi Vanden Eng; Simon O. Owino; A A Lal; Yusuf Omosun; Kephas Otieno; Meghna Desai; Feiko O. ter Kuile; Bernard L. Nahlen; Julie M. Moore; Mary J. Hamel; Peter Ouma; Laurence Slutsker; Ya Ping Shi
BackgroundResistance 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.MethodsTemporal 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.ResultsThe 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.ConclusionsThere 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.
Tropical Medicine & International Health | 2007
Peter Ouma; A M van Eijk; Mary J. Hamel; E. Sikuku; Frank Odhiambo; K. Munguti; John G. Ayisi; Piet A. Kager; Laurence Slutsker
Background In 1998, Kenya adopted intermittent preventive treatment (IPTp) with sulphadoxine‐pyrimethamine (SP) for malaria prevention during pregnancy. We conducted a survey in 2002 among women who had recently delivered in the rural neighbouring areas Asembo and Gem and reported coverage of 19% of at least one dose and 7% of two or more doses of SP. Health care workers (HCW) in Asembo were retrained on IPTp in 2003.