RESUMO
Biomphalaria pfeifferi of different sizes were subjected to fluctuating temperature regimes incorporating quantities of above-optimal heat ranging from approximately 2 to 75 degree hours greater than 27 degrees C per day. Fecundity over this range was found to be similar from 2 to 45 deg.h. greater than 27 degrees C/day but above this level egg production fell sharply. Histological examination of the gonads of experimental and control snails showed that not only was gametogenesis retarded above 45 deg.h. greater than 27 degrees C/day but also, and perhaps more importantly, development of the gonad was considerably impaired. It is hoped that this kind of information, which is based on field data, will be useful in assessing the likelihood of Schistosoma mansoni transmission becoming established in newly impounded waters in non-endemic areas.
Assuntos
Biomphalaria/fisiologia , Temperatura Alta , Animais , Feminino , Fertilidade , Oócitos/ultraestrutura , Oogênese , Fatores de TempoRESUMO
Faecal specimens were collected form a total of 7569 scholars at 45 different localities in northern KwaZulu and screened for the presence of intestinal helminth and protozoan parasites. The soil-transmitted nematodes Ascaris lumbricoides, Trichuris trichiura and hookworm sp. were extremely common, with prevalences in certain localities ranking among the highest to be recorded in South Africa. Entamoeba coli was by far the commonest (60%) of the protozoa;p all the other species had prevalences of less than 10%. The distribution age-specific prevalence and the influence of the variables-sex, ara and age-on the occurrence of the various intestinal parasites are described.
Assuntos
Helmintíase/epidemiologia , Enteropatias Parasitárias/epidemiologia , Infecções por Protozoários/epidemiologia , Adolescente , Adulto , Negro ou Afro-Americano , Fatores Etários , População Negra , Criança , Pré-Escolar , Fezes/parasitologia , Feminino , Geografia , Humanos , Masculino , Fatores Sexuais , África do SulRESUMO
Urine and stool specimens from 856 school children aged from 7 to 20 years, and from 80 preschool children, were examined for Schistosoma haematobium and intestinal helminths and protozoa. S. haematobium was present in 57% with a peak of 81% in 13-14-year-old children. Peak intensity preceded peak incidence and egg loads gradually decreased with age. There was no clear-cut difference between boys and girls with regard to intestinal parasites, nor was there a close correlation between the incidence of Schistosoma spp. and that of the intestinal parasites. There was a considerable reduction in the incidence of Ascaris lumbricoides and Trichuris trichiura infestation with age.