Research Articles
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A research article reports the results of original research, assesses its contribution to the body of knowledge in a given area, and is published in a peer-reviewed scholarly journal. The faculty publications through published and on-going articles/researches are captured in this community
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Item Incidence of symptomatic and asymptomatic plasmodium falciparum infection following curative therapy in adult residents of northern Ghana.(American Journal of Tropical Medicine and Hygiene, 2001) Owusu-Agyei, S.; Koram, K.A.; Baird, J.K.; Utz, G.C.; Binka, F.N.; Nkrumah, F.K.; Fryauff, D.J.; Hoffman, S.L.Adult residents of holoendemic malaria regions in Africa have a naturally acquired immunity (NAI) to malaria that renders them more resistant to new infections, limits parasitemia, and reduces the frequency and severity of illness. Given such attributes, it is not clear how one might evaluate drug or vaccine efficacy in adults without serious confounding. To determine symptomatic and asymptomatic malaria attack rates in adults of northern Ghana, 197 men and women underwent curative therapy for any pre-existing malaria infections at the start of the high transmission (wet) season. They were monitored for first parasitemia and first clinical episode of infection by Plasmodium falciparum over a 20-week period (May-October 1996). The cumulative incidence of primary infection by P. falciparum was 0.98 and incidence density of infection was calculated to be 7.0 cases/person-year. Symptoms were reported by 19.5% of the individuals at the time of first recurrent parasitemia. Incidence of infection, parasite density, and the frequency of symptoms were comparable in males and females. The results suggest that NAI did not provide these adults with significant defense against rapid re-infection and suggest that this population-infection design could serve to demonstrate the efficacy of a drug or vaccine in preventing parasitemia.Item Characteristics of severe anemia and its association with malaria in young children of the Kassena-Nankana district of northern Ghana.(American Journal of Tropical Medicine and Hygiene, 2002) Owusu-Agyei, S.; Fryauff, D.J.; Chandramohan, D.; Koram, K.A.; Binka, F.N.; Nkrumah, F.K.; Utz, G.C.; Hoffman, S.L.Severe anemia is thought to be the principal underlying cause of malaria death in areas of intense seasonal malaria transmission such as the Kassena-Nankana District of northern Ghana. Factors associated with severe anemia in young children, 6-24 months old, were elucidated by analyzing results of 2 malaria-associated anemia surveys (1996, 2000), separated by 4 years, but conducted in the same community and at the same seasonal time point. Age-adjusted comparison confirmed that the proportion of severely anemic children and overall mean hemoglobin (Hb) levels in the November 2000 sample were significantly improved over those of the 1996 sample (17.5 versus 26.4%, P = 0.03; Hb 7.5 versus 6.9 g/dL, P = 0.002). Weight-for-age Z-scores also indicated a significant improvement in the 2000 sample (-1.93 versus -2.20, P < 0.05). Independently, each survey identified statistically significant associations between severe anemia and age, parasite rate, fever, and sex. Relative to children with Hb > or = 6.0 g/dL, those with severe anemia (Hb < 6.0 g/dL) were older, more frequently parasitemic (odds ratio [OR], 1.60; 95% confidence interval [CI], 1.08-2.35), more often febrile (OR, 2.44; 95% CI, 1.71-3.48), and predominantly male (OR, 1.50; 95% CI, 1.05-2.13). An association was identified in both surveys between severe anemia and residence in the northern part of the district, but no clear link was observed in relation to irrigation. Blood transfusions, a likely surrogate index of severe anemia in young children, followed a distinct seasonal pattern. Evidence suggests that dramatic peaks and troughs of severe anemia are regular and possibly predictable events that may be used to gauge the health and survival of young children in this area.Item A multilateral effort to develop DNA vaccines against falciparum malaria.(Trends in Parasitology, 2002) Kumar, S.; Epstein, J.E.; Richie, T.L.; Nkrumah, F.K.; Soisson, L.; Carucci, D.J.; Hoffman, S.L.Scientists from several organizations worldwide are working together to develop a multistage, multigene DNA-based vaccine against Plasmodium falciparum malaria. This collaborative vaccine development effort is named Multi-Stage DNA-based Malaria Vaccine Operation. An advisory board of international experts in vaccinology, malariology and field trials provides the scientific oversight to support the operation. This article discusses the rationale for the approach, underlying concepts and the pre-clinical development process, and provides a brief outline of the plans for the clinical testing of a multistage, multiantigen malaria vaccine based on DNA plasmid immunization technology.Item Severe anemia in young children after high and low malaria transmission seasons in the Kassena-Nankana district of northern Ghana.(American Journal of Tropical Medicine and Hygiene, 2000) Koram, K.A.; Owusu-Agyei, S.; Utz, G.; Binka, F.N.; Baird, J.K.; Hoffman, S.L.; Nkrumah, F.K.Malaria and anemia accounted for 41% and 18% respectively of hospital deaths in the Kassena-Nankana district of northern Ghana during 1996. We measured hemoglobin (Hb), malaria prevalence, and anthropometric indices of 6—24-month-old infants and young children randomly selected from this community at the end of the high (May–October, n 347) and low (November–April, n 286) malaria transmission seasons. High transmission season is characterized by rainfall (the equivalent of 800–900 mm/yr.), while the remaining months receive less than 50 mm/yr. Severe anemia, defined as Hb 6.0 g/dL, was 22.1% at the end of the high transmission season compared to 1.4% at the end of the low transmission season (Odds Ratio [OR] 20.1; 95% CI: 7.1–55.3). Parasitemia was 71% and 54.3% at these time points (OR 2.1; 95% CI: 1.5–2.9). Nutritional anemia appeared to have little impact upon this seasonal difference since anthropometric indices were comparable. Although the relative contributions of other causes of severe anemia were not assessed, repeated malaria infections may be a primary determinant of severe anemia among infants and young children during the high transmission season.Item Seasonal profiles of malaria infection, anaemia, and bednet use among age groups and communities in northern Ghana.(Tropical Medicine and International Health, 2003) Koram, K.A.; Owusu-Agyei, S.; Fryauff, D.J.; Anto, F.; Atuguba, F.; Hodgson, A.; Hoffman, S.L.; Nkrumah, F.K.We conducted all-age point prevalence surveys to profile the severity and seasonality of malaria and anaemia in Kassena-Nankana District of northern Ghana. Random cross-sectional surveys were timed to coincide with the end of low (May 2001) and high (November 2001) malaria transmission seasons and to yield information as to the potential value of haemoglobin (Hb) levels and parasitaemia as markers of malaria morbidity and/or malaria vaccine effect. Parasitaemia was found in 22% (515 of 2286) screened in May (dry-low transmission), and in 61% of the general population (1026 of 1676) screened in November (wet-high transmission). Malaria prevalence in May ranged from 4% (infants <6 months and adults 50–60 years) to 54% (children 5–10 years). Age-specific malaria prevalence in November ranged from 38% (adults 50–60 years) to 82% (children 5–10 years). Differences between low- and high-transmission periods in the prevalence of severe anaemia (SA) among young children (6–24 months) were unexpectedly comparable (low, 3.9%vs. high, 5.4%; P = 0.52) and greatly reduced from levels measured in this same community and age group in November 2000 (12.5%) and November 1996 (22.0%). Despite the lower frequency of anaemia/SA in young children surveyed in 2001, it was still clear that this condition was strongly associated with parasitaemia and that children under 5 years of age experienced a significant drop in their mean Hb levels by the end of the high transmission season. Prevalence of parasitaemia was significantly lower (P < 0.01) among infants and young children (<2 years) whose parents reported the use of bednets. There was a significantly lower risk of parasitaemia among infants [odds ratio (OR) 6–8] and young children (OR 3–4) living in the central, more urbanized sector of the study area.