37 research outputs found

    On the evolutionary ecology of mosquito immunity and the use of transgenic mosquitoes for malaria control

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    Mosquitoes that are genetically manipulated to encapsulate the malaria parasite Plasmodium falciparum are being considered a possible method to control malaria. Hopes for this have been raised by the identification of genes involved in the mosquito鈥檚 encapsulation response and by advances in the tools required to transform mosquitoes. But will such genes be able to spread in natural populations? What will their impact be on the epidemiology of the disease? This article attempts to give answers to these questions by reviewing some of theoretical and empirical considerations underlying the evolutionary epidemiology of genetic manipulation and refractorines

    Ultrasound scanning for detecting morbidity due to Schistosoma haematobium and its resolution following treatment with different doses of praziquantel

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    A study to assess the resolution of urinary tract morbidity due to Schistosoma haematobium was conducted on 2 cohorts of schoolchildren attending neighbouring schools in Kilombero District, southern Tanzania. Schoolchildren were screened for S. haematobium infection using the standard World Health Organization filtration technique and subsequently examined for urinary tract pathology using a portable 3路0 MHz sector scanner (Siemens Sonoline 1300). Treatment with praziquantel was given to all infected children. Children with observed urinary tract pathology received either 20 (n = 52) or 40 (n = 79) mg/kg body weight and were sonographically re-examined one, 2, 3 and 6 months following treatment. Geometric mean outputs of 21 and 19 eggs/ml of urine were detected in the 2 cohorts before treatment. Urinary tract pathology correlated positively with egg output (蠂2, P = 0路02) and microhaematuria (P = 0路0001). Bladder (wall irregularities and polyps) and kidney (congestive changes) pathologies were found in 81% and 36%, respectively, of the group that received 20 mg/kg of praziquantel, and in 78% and 46% of the group that received 40 mg/kg. Six months after treatment, 90路4% and 88路0% parasitological cure rates were obtained using 20 or 40 mg praziquantel/kg body weight. The respective pathology clearances were 88% and 91%. 20 mg/kg of praziquantel was as effective with regard to cure rates and reversibility of morbidity as 40 mg/k

    In vitro resistance patterns of Plasmodium falciparum to chloroquine鈥攁 reflection of strain-specific immunity?

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    Studies in vitro among children on the response of Plasmodium falciparum to chloroquine were conducted as part of the national long-term monitoring of drug resistance in a holo- to hyperendemic malarious area of Tanzania between 1983 and 1989. Overall, no significant increase in chloroquine resistance was observed. However, in children under 5 years old resistance increased during this period, whereas in schoolchildren resistance decreased from 1986 to 1989. A hypothesis based on antigenic differences between resistant and sensitive strains is proposed to explain this age-specific pattern. If immunity develops principally against the most frequent parasite strains, then as it develops the numbers of the most frequent strains will be reduced, whilst the rare strains may become predominant and thus be detected in the blood of immune patients. Thus, in an endemic area, the observed resistance pattern in non-immune infants will differ from that in immune schoolchildren, as was observed in the present study. These findings may have important implications for the control of malaria and the development of vaccine
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