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

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

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

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 3·0 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 (χ2, P = 0·02) and microhaematuria (P = 0·0001). 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, 90·4% and 88·0% 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

Epidemiology and strain differentiation of Echinococcus granulosus in Kenya

SIGLEAvailable from British Library Document Supply Centre-DSC:DX198395 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Role of jackals in the transmission of Ecchinococcus granulosus in the Turkana District of Kenya

In IDL-535

The epidemiology of hydatid disease in the United Kingdom and Kenya

Unilocular hydatid disease, caused by larvae of the tapeworm, Echinococcus granulosus, is endemic in the U.K. and Kenya. In the U.K., there are foci of human infection notably in the sheep-rearing areas of South Wales and North-West Scotland, where there is a correspondingly high prevalence in sheep and farm dogs. Red foxes may play a significant role in the sheep/dog cycle in Wales. In the Turkana region of North West Kenya, the incidence for human hydatidosis is the highest anywhere in the world. This is related, in part, to large numbers of heavily infected feral and domestic dogs. Silver backed and golden jackals also harbour the parasite, but wild, infected, intermediate hosts have not been found. The disease has a low prevalence in cattle, sheep and goats and, uniquely, man is a potential biological participant in the cyclic transmission of E. granulosus. In contrast, in Masailand (Southern Kenya), there is a low incidence in man, a high prevalence in domestic animals and a sylvatic cycle perpetuated between lions, Cape hunting dogs, jackals and a range of wild ungulates. A sheep/dog strain and a horse/ dog strain of E. granulosus have been identified in the U.K. Whereas the former strain is known to be infective to man, the precise host-specificity of the latter remains undetermined although indirect epidemiological evidence suggests a low infectivity to man. The strain picture emerging from Kenya indicates an unusually complex strain situation with the sheep/dog, human/dog and majority of goat/dog parasites being similar and probably infective to one another. The cattle/dog and, particularly the camel/dog parasites have major differences from the human/dog form and their status remains undefined, especially with regard to their potential infectivity to man.L’hydatidose (échinococcose uniloculaire) causée par la larve d'E .granulosus est endémique en Grande-Bretagne et au Kenya. Il existe en Grande-Bretagne des foyers notables d’infection dans les secteurs d’élevage ovin au sud du pays de Galles et au nord-ouest de l’Ecosse où existe une forte prévalence concordante entre moutons et chiens de ferme. Les renards peuvent jouer un rôle significatif dans le cycle mouton/chien au pays de Galles. Dans la région du Turkana au nord-ouest du Kenya, l’incidence humaine d’hydatidose est la plus forte du monde. Ceci est en partie lié au grand nombre de chiens errants et domestiques lourdement infestés. Les deux espèces de chacals hébergent le parasite, mais les hôtes intermédiaires sauvages restent inconnus. La prévalence est assez faible chez les bovins, moutons et chèvres et fait unique, l’homme participe potentiellement, comme hôte intermédiaire, au cycle de E. granulosus. Au contraire en pays Masai (sud du Kenya) l’incidence est faible chez l’homme et la prévalence forte chez les espèces domestiques. Un cycle selvatique se perpétue entre les lions, lycaons, chacals et divers ongulés sauvages. Une souche chien/mouton et une autre chien/cheval de E. granulosus ont été reconnues en Grande-Bretagne. Alors que la première souche est connue pour contaminer l’homme, la spécificité d’hôte précise de la seconde reste indéterminée, quoique des éléments épidémiologiques indirects suggèrent un pouvoir infectieux faible chez l’homme. Au Kenya, la situation des souches est plus confuse car les parasites chien/mouton, chien/homme et la majorité des parasites chien/chèvre sont semblables, et probablement inter-infectieux. Les parasites chien/bétail et surtout chien/dromadaire présentent des différences majeures de la forme chien/homme et leur situation reste mal définie, particulièrement sous l’aspect de la contagion à l’homme.McManus D.P., Smyth J.D., Macpherson C.N.L. The epidemiology of hydatid disease in the United Kingdom and Kenya . In: Revue d'Écologie (La Terre et La Vie), tome 40, n°2, 1985. pp. 217-223