Rift Valley Fever Seroprevalence in Coastal Kenya.

Rift Valley fever virus (RVFV) causes severe disease in both animals and humans, resulting in significant economic and public health damages. The objective of this study was to measure RVFV seroprevalence in six coastal Kenyan villages between 2009 and 2011, and characterize individual-, household-, and community-level risk factors for prior RVFV exposure. Sera were tested for anti-RVFV IgG via enzyme-linked immunosorbent assay.

Dengue and West Nile Virus Transmission in Children and Adults in Coastal Kenya.

Dengue virus (DENV) and West Nile virus (WNV) are important reemerging arboviruses that are under-recognized in many parts of Africa due to lack of surveillance. As a part of a study on flavivirus, alphavirus, and parasite exposure in coastal Kenya, we measured neutralizing antibody against DENV and, to evaluate assay specificity, WNV in serum samples that tested positive for serum anti-DENV IgG by enzyme-linked immunosorbent assay. Of 830 anti-DENV IgG-positive samples that were tested for neutralizing activity, 488 (58.

Contrasting Patterns of Serologic and Functional Antibody Dynamics to Plasmodium falciparum Antigens in a Kenyan Birth Cohort.

IgG antibodies to Plasmodium falciparum are transferred from the maternal to fetal circulation during pregnancy, wane after birth, and are subsequently acquired in response to natural infection. We examined the dynamics of malaria antibody responses of 84 Kenyan infants from birth to 36 months of age by (i) serology, (ii) variant surface antigen (VSA) assay, (iii) growth inhibitory activity (GIA), and (iv) invasion inhibition assays (IIA) specific for merozoite surface protein 1 (MSP1) and sialic acid-dependent invasion pathway. Maternal antibodies in each of these four categories were detected in cord blood and decreased to their lowest level by approximately 6 months of age.

Use of prospective hospital surveillance data to define spatiotemporal heterogeneity of malaria risk in coastal Kenya.

Background: Malaria in coastal Kenya shows spatial heterogeneity and seasonality, which are important factors to account for when planning an effective control system. Routinely collected data at health facilities can be used as a cost-effective method to acquire information on malaria risk for large areas. Here, data collected at one specific hospital in coastal Kenya were used to assess the ability of such passive surveillance to capture spatiotemporal heterogeneity of malaria and effectiveness of an augmented control system.

Anemia Among Children Exposed to Polyparasitism in Coastal Kenya.

Anemia represents a substantial problem for children living in areas with limited resources and significant parasite burden. We performed a cross-sectional study of 254 Kenyan preschool- and early school-age children in a setting endemic for multiple chronic parasitic infections to explore mechanisms of their anemia. Complete venous blood cell counts revealed a high prevalence of local childhood anemia (79%).

Age-Stratified Profiles of Serum IL-6, IL-10, and TNF-α Cytokines Among Kenyan Children with Schistosoma haematobium, Plasmodium falciparum, and Other Chronic Parasitic Co-Infections.

In a study of children having polyparasitic infections in a Schistosoma haematobium-endemic area, we examined the hypothesis that S. haematobium-positive children, compared with S. haematobium-negative children (anti-soluble worm antigen preparation [SWAP] negative and egg negative) have increased systemic production of pro-inflammatory cytokines (interleukin [IL]-6, tumor necrosis factor [TNF]-α) and decreased down-regulatory IL-10.

High rates of o'nyong nyong and Chikungunya virus transmission in coastal Kenya.

Background: Chikungunya virus (CHIKV) and o'nyong nyong virus (ONNV) are mosquito-borne alphaviruses endemic in East Africa that cause acute febrile illness and arthritis. The objectives of this study were to measure the seroprevalence of CHIKV and ONNV in coastal Kenya and link it to demographics and other risk factors.

Methodology: Demographic and exposure questionnaires were administered to 1,848 participants recruited from two village clusters (Milalani-Nganja and Vuga) in 2009.

Cross-sectional study of the burden of vector-borne and soil-transmitted polyparasitism in rural communities of Coast Province, Kenya.

Background: In coastal Kenya, infection of human populations by a variety of parasites often results in co-infection or poly-parasitism. These parasitic infections, separately and in conjunction, are a major cause of chronic clinical and sub-clinical human disease and exert a long-term toll on economic welfare of affected populations. Risk factors for these infections are often shared and overlap in space, resulting in interrelated patterns of transmission that need to be considered at different spatial scales.

Development of a specimen-sparing multichannel bead assay to detect antiparasite IgG4 for the diagnosis of Schistosoma and Wuchereria infections on the coast of Kenya.

To better delineate the impact of parasitic coinfection in coastal Kenya, we developed a novel specimen-sparing bead assay using multiplex flow immunoassay (MFI) technology to simultaneously measure serum or plasma immunoglobulin G4 (IgG4) against Brugia malayi antigen (BMA) and Schistosoma haematobium soluble worm antigen (SWAP). Properties of the bead assay were estimated by latent class analysis using data from S. haematobium egg counts/filarial rapid diagnostic cards (RDTs), parasite-specific enzyme-linked immunosorbent assays (ELISAs), and the multichannel IgG4 assay.

Evaluation of the health-related quality of life of children in Schistosoma haematobium-endemic communities in Kenya: a cross-sectional study.

Background: Schistosomiasis remains a global public health challenge, with 93% of the ~237 million infections occurring in sub-Saharan Africa. Though rarely fatal, its recurring nature makes it a lifetime disorder with significant chronic health burdens. Much of its negative health impact is due to non-specific conditions such as anemia, undernutrition, pain, exercise intolerance, poor school performance, and decreased work capacity.

Impact of polyparasitic infections on anemia and undernutrition among Kenyan children living in a Schistosoma haematobium-endemic area.

We measured prevalence of Schistosoma haematobium, Wuchereria bancrofti, Plasmodium falciparum, hookworm, and other geohelminths among school-aged children in four endemic villages in Kwale County, Kenya and explored the relationship between multiparasite burden, undernutrition, and anemia. In 2009-2010 surveys, cross-sectional data were obtained for 2,030 children 5-18 years old. Infections were most prevalent for S.

Projecting the long-term impact of school- or community-based mass-treatment interventions for control of Schistosoma infection.

Background: Schistosomiasis remains a significant health burden in many areas of the world. Morbidity control, focused on limiting infection intensity through periodic delivery of anti-schistosomal medicines, is the thrust of current World Health Organization guidelines (2006) for reduction of Schistosoma-related disease. A new appreciation of the lifetime impact of repeated Schistosoma infection has directed attention toward strategies for greater suppression of parasite infection per se, with the goal of transmission interruption.

Differentiating Schistosoma haematobium from related animal schistosomes by PCR amplifying inter-repeat sequences flanking newly selected repeated sequences.

In schistosomiasis elimination programs, successful discrimination of Schistosoma haematobium from the related animal Schistosoma parasites will be essential for accurate detection of human parasite transmission. Polymerase chain reaction assays employing primers from two newly selected repeated sequences, named Sh73 and Sh77, did not discriminate S. haematobium when amplifying Sh73-77 intra- or inter-repeats.

Partnering parasites: evidence of synergism between heavy Schistosoma haematobium and Plasmodium species infections in Kenyan children.

Background: Residents of resource-poor tropical countries carry heavy burdens of concurrent parasitic infections, leading to high rates of morbidity and mortality. This study was undertaken to help identify the social and environmental determinants of multiple parasite infection in one such community.

Methodology/principal Findings: Residents of Kingwede, Kenya aged 8 years and older were tested for presence and intensity of S.

In utero activation of fetal memory T cells alters host regulatory gene expression and affects HIV susceptibility.

In utero priming to malaria antigens renders cord blood mononuclear cells (CBMC) more susceptible to productive HIV infection in vitro in the absence of exogenous stimulation. This provides a unique model to better understand mechanisms affecting lymphocyte susceptibility to HIV infection in vivo. Effector memory CD3(+)CD4(+) T cells (T(EM)) were the exclusive initial targets of HIV with rapid spread to central memory cells.

Impact of drought on the spatial pattern of transmission of Schistosoma haematobium in coastal Kenya.

We analyzed temporal changes in spatial patterns of active Schistosoma haematobium infection in different age groups and associated them with ponds infested with Bulinus snails. A major drought between 2001 and 2009 resulted in drying of ponds that were known sources of infection, and we detected very few or no snails in ponds that were infested in the past. The household-level spatial pattern of infection for children of various age groups in 2009 was contrasted with historical data from 2000.

Measuring fitness of Kenyan children with polyparasitic infections using the 20-meter shuttle run test as a morbidity metric.

Background: To date, there has been no standardized approach to the assessment of aerobic fitness among children who harbor parasites. In quantifying the disability associated with individual or multiple chronic infections, accurate measures of physical fitness are important metrics. This is because exercise intolerance, as seen with anemia and many other chronic disorders, reflects the body's inability to maintain adequate oxygen supply (VO(2) max) to the motor tissues, which is frequently linked to reduced quality-of-life in terms of physical and job performance.

Fine specificity of neonatal lymphocytes to an abundant malaria blood-stage antigen: epitope mapping of Plasmodium falciparum MSP1(33).

Cord blood T cells have been reported to respond to a variety of exogenous Ags, including environmental allergens and various viruses and parasites, as demonstrated by enhanced proliferation and cytokine secretion. This finding is evidence that Ags in the maternal environment transplacentally prime and result in fetal development of memory T cells. Some studies suggest these neonatal T cell responses may arise by nonspecific activation of T cells that express TCRs with low binding affinity, thus lacking fine lymphocyte specificity.

Spatial and temporal variations in local transmission of Schistosoma haematobium in Msambweni, Kenya.

As part of an extensive study of the eco-epidemiology of urinary schistosomiasis along the southern coast of Kenya, spatial and temporal transmission patterns were associated with various ponds infested with Bulinus snails. The household-level spatial pattern of infection for children of various age groups in 2000 was contrasted with historical data from 1984. Significant local clustering of high and low infection levels among school age children was detected, and the spatial extent of clusters and their direction from specific water sources were measured.

Prenatal T cell immunity to Wuchereria bancrofti and its effect on filarial immunity and infection susceptibility during childhood.

Background: Antenatal immune experience with Wuchereria bancrofti due to maternal filariasis may influence susceptibility to infection. We tested the hypothesis that filarial-specific T cell responses at birth that are indicative of in utero tolerance or sensitization affect the evolution of filarial-specific immunity and susceptibility to W. bancrofti infection during childhood.

The effects of maternal helminth and malaria infections on mother-to-child HIV transmission.

Objective: To investigate the effect of helminth and/or malaria infection on the risk of HIV infection in pregnant women and its transmission to their offspring.

Design: A retrospective cohort study of pregnant Kenyan women and their offspring from term, uncomplicated vaginal deliveries (n = 936) with a nested case-control study.

Methods: We determined the presence of HIV, malaria, schistosomiasis, lymphatic filariasis, and intestinal helminthes in mothers and tested for HIV antibodies in 12-24 month-old offspring of HIV-positive women.

Increased ratio of tumor necrosis factor-alpha to interleukin-10 production is associated with Schistosoma haematobium-induced urinary-tract morbidity.

Bladder and kidney disease, which affect approximately 25%-30% of subjects infected with Schistosoma haematobium, are mediated by T cell-dependent granulomatous responses to schistosome eggs. To determine why only some infected subjects develop disease, we examined the hypothesis that infected Kenyan subjects with ultrasound-detected urinary-tract morbidity (n=49) had dysregulated cytokine production leading to enhanced granulomatous responses, compared with subjects of similar age and intensity of infection without morbidity (n=100). Peripheral blood mononuclear cells from subjects with morbidity produced 8-fold greater levels of egg antigen-driven tumor necrosis factor (TNF)-alpha and had a 99-fold greater mean TNF-alpha:interleukin (IL)-10 ratio, compared with subjects without disease.