A study was undertaken in order to determine the prevalence and aetiology of anaemia in pregnancy in coastal Kenya, so as to establish locally important causes and enable the development of appropriate intervention strategies. 275 women attending the antenatal clinic at Kilifi district hospital, Kenya, were recruited in November 1993. The prevalence of anaemia (haemoglobin [Hb] < 11 g/dL) was 75.6%, and the prevalence of severe anaemia (Hb < 7g/dL) was 9.8% among all parities; 15.3% of 73 primigravidae were severely anaemic, compared with 7.9% of 202 multigravidae (P = 0.07). In primigravidae, malaria infection (Plasmodium falciparum) was strongly associated with moderate and severe anaemia (chi 2 test for trend, P = 0.003). Severe anaemia was more than twice as common in women with peripheral parasitaemia as in those who were aparasitaemic, and parasitaemia was associated with a 2.2g/dL decrease in mean haemoglobin level (P < 0.001). In multigravidae, iron deficiency and hookworm infection were the dominant risk factors for anaemia. Folate deficiency and human immunodeficiency virus infection were not strongly associated with anaemia. It is suggested that an intervention that can effectively reduce malaria infection in primigravidae could have a major impact on the health of these women and their infants.

With the aim of developing an appropriate in vitro model of the sequestration of developing Plasmodium falciparum sexual-stage parasites, we have investigated the cytoadherence of gametocytes to human bone marrow cells of stromal and endothelial origin. Developing stage III and IV gametocytes, but not mature stage V gametocytes, adhere to bone marrow cells in significantly higher densities than do asexual-stage parasites, although these adhesion densities are severalfold lower than those encountered in classical CD36-dependent assays of P. falciparum cytoadherence. This implies that developing gametocytes undergo a transition from high-avidity, CD36-mediated adhesion during stages I and II to a lower-avidity adhesion during stages III and IV. We show that this adhesion is CD36 independent, fixation sensitive, stimulated by tumor necrosis factor alpha, and dependent on divalent cations and serum components. These data suggest that gametocytes and asexual parasites utilize distinct sets of receptors for adhesion during development in their respective sequestered niches. To identify receptors for gametocyte-specific adhesion of infected erythrocytes to bone marrow cells, we tested a large panel of antibodies for the ability to inhibit cytoadherence. Our results implicate ICAM-1, CD49c, CD166, and CD164 as candidate bone marrow cell receptors for gametocyte adhesion.Human malaria is caused by several species of protozoan parasites within the genus Plasmodium. The majority of malaria-related mortality is due to infection with the species Plasmodium falciparum. Microscopic examination of the peripheral blood of people infected with this species commonly reveals only two developmental forms: early trophozoite stages, termed "rings," and mature (stage V) gametocytes. Trophozoites are asexual forms that rapidly multiply, often causing disease, whereas gametocytes have no known association with disease but are the only form of the parasite that is infective to mosquitoes. All other stages of the parasite's development are sequestered in the deep vasculature among various host organs.Early stage V gametocytes of P. falciparum appear during in vitro culture 8 to 10 days after emergence from the parent schizont (14,22), suggesting that, in vivo, stage I to IV gametocytes spend a minimum of 7 days sequestered in host tissues. Recent observations of gametocyte emergence following antimalarial treatment of clinical malaria cases are consistent with this estimate of the duration of gametocyte sequestration (G. A. T. Targett and C. J. Drakeley, unpublished data). This is in marked contrast to the sequestration of asexual parasites, which is assumed to be in the order of 22 to 26 h in duration (9, 21). Furthermore, existing evidence from limited in vivo studies indicates that the distribution of sequestered gametocytes is measurably different from that of sequestered asexual parasites within the host. In a study of 22 Gambian children, Smalley et al. (23) found that immature gametocytes (stages II, III, and IV) had a 5-fold-highe...

Saliva contains components of both the mucosal and systemic immune systems. Variable flow rates, immunoglobulin proteases, and variation in collection and storage methods all introduce differences in the estimated concentrations of antibodies. We evaluated the effect of four collection methods and three storage protocols on the concentrations of immunoglobulin A (IgA) antibodies to pneumococcal capsular antigens 1, 5, 6B, and 14 and to pneumococcal surface adhesin A (PsaA) in saliva. Specimens were collected from 30 healthy Kenyan adults by collecting drool, by pipette suction, and with two commercial kits, OraSure and Oracol. Aliquots from each specimen were snap-frozen with glycerol in liquid nitrogen or stored for 4 to 8 h at ؉4°C either with or without the addition of protease enzyme inhibitors prior to storage at ؊70°C. Anticapsular IgA concentrations were not significantly different with different collection methods, but snap-freezing the specimens in liquid nitrogen led to concentrations 41 to 47% higher than those of specimens stored by the other methods (P < 0.0005).