Carbohydrate metabolism of schistosoma mansoni

1. Schistosoma mansoni utilizes in 1 hour an amount of glucose equivalent to one-sixth to one-fifth of its dry weight. Over 80 per cent of the metabolized glucose is converted to lactic acid by this organism. 2. The rates of glucose utilization and of lactic acid production by S. mansoni are the same under aerobic and under anaerobic conditions. 3. A high rate of lactic acid production and the absence of a postanaerobic increase in the oxygen uptake differentiate S. mansoni from most other parasitic helminths whose metabolism has been studied. 4. Arsenite and p-chloromercuric benzoate inhibit in low concentrations the oxygen uptake and the rate of glycolysis of S. mansoni. This inhibition is not prevented or reversed by an excess of glutathione or of thioglycollate. 5. Fluoride inhibits the removal of glucose and the production of lactic acid by S. mansoni to the same degree. 6. Low concentrations of quinacrine (atabrine) do not affect the respiration or the carbohydrate metabolism of the schistosomes. 7. The inhibitory effect of aldehydes on the metabolism of S. mansoni has been measured. Among this group of compounds dl-glyceraldehyde and o-nitrobenzaldehyde are the most effective inhibitors of glycolysis. 8. In a concentration of 2.6 x 10^–6M (1:1,000,000) a cyanine dye inhibits almost completely the respiration of the schistosomes, but has no effect on their rate of glycolysis. The oxygen uptake of the worms is inhibited by fuadin to a greater degree than their rate of glycolysis. 2-methyl-1,4-napthoquinone is a much more effective inhibitor of glycolysis than of the respiration of S. mansoni. The latter compound interacts with plasma albumin and, therefore, its inhibitory action on the metabolism of the schistosomes is greatly reduced in human serum or plasma. 9. Evidence is discussed which indicates that, in contrast to glycolysis, respiratory metabolism is not essential for the survival of S. mansoni.

SOLUBLE ANTIGEN FLUORESCENT-ANTIBODY TECHNIQUE

An indirect fluorescent-antibody (FA) procedure employing soluble antigen fixed onto an artificial matrix was developed, and a mechanical means for reading of test results was devised. The method employs two small cellulose acetate paper discs for each test. One disc contains soluble antigen diluted in 1% bovine serum albumin (BSA); the other contains only 1% BSA and serves as a control. After testing by the indirect FA procedure, the results of the tests are read on a fluorometer fitted with a paper chromatogram door. The instrument is set at zero with the control disc as a blank, and the specific fluorescence of the antigen disc is determined. Findings obtained with homologous and heterologous antisera indicated that the method yields excellent results. The soluble antigen fluorescent-antibody technique has definite advantages over the conventional indirect FA procedures. (i) The investigator may objectively select the antigen to be employed. (ii) It is possible to obtain objective mechanical reading of test results rather than the highly subjective readings required by conventional methods. (iii) The system compensates for any nonspecific fluorescence contributed either by the serum (e.g., drugs) or by free fluorescein in the conjugated antiserum.

THE EFFECTS OF ANTIMONY UPTAKE ON THE LOCATION AND PAIRING OF SCHISTOSOMA MANSONI

The rate of uptake and elimination of antimony by both male and female schistosomes has been measured. It has been confirmed that the female schistosome is more susceptible to antimony therapy than the male since she absorbs more drug. The changes in location of the worms and the separation of the sexes following one or more injections of antimony potassium tartrate have been related to the different rates of uptake and elimination of the drug by the two sexes. The suppressive treatment of schistosomiasis is discussed in the light of these observations.

SCHISTOSOMES FROM HIPPOPOTAMUS AMPHIBIUS L. II. THE MORPHOLOGY OF SCHISTOSOMA EDWARDIENSE SP. NOV

The morphology of the adult blood flukeSchistosoma edwardiensesp.nov. fromHippopotamus amphibiusL. is described and compared with that of other species ofSchistosoma.

I wish to acknowledge the receipt of a research grant from Makerere University College towards expenses incurred during this work. I should like to thank Captain F. Poppleton, Warden of the Queen Elizabeth National Park, Dr R. M. Laws, Nuffield Unit for Tropical Animal Ecology, and Dr W. M. Longhurst, University of California, for helping me to get specimens from the hippopotami, also Mr L. Rugema, histologist, for sectioning the worms.

DIFFERENCES IN THE EGG MORPHOLOGY AND CERTAIN BIOLOGICAL CHARACTERISTICS OF SOME AFRICAN AND MIDDLE EASTERN SCHISTOSOMES, GENUS SCHISTOSOMA, WITH TERMINAL-SPINED EGGS

There is some confusion regarding the differentiation of African and Middle Eastern schistosomes with terminal-spined eggs. In an attempt to clarify the situation, the author has separated the members of the genus Schistosoma that have terminal-spined eggs into three broad groups and five species on the basis of egg morphology and certain biological characteristics.THE GROUPS ARE: the haematobium group, with one species (S. haematobium); the bovis group, with three species (S. bovis, S. mattheei and S. leiperi); and the intercalatum group, with one species (S. intercalatum). Further species separation is not thought to be justified yet, and reasons are given for considering S. capense and S. curassoni as synonymous with S. haematobium and S. mattheei respectively.

STUDIES ON GRANULOMA FORMATION. III. ANTIGEN SEQUESTRATION AND DESTRUCTION IN THE SCHISTOSOME PSEUDOTUBERCLE

Images

SCHISTOSOME DERMATITIS IN SACRAMENTO, CALIFORNIA

Pruritus developed in two persons at different times, after contact with water in a duck pond at a motel in Sacramento. At those times (in August 1961 and June 1962) large numbers of snails infected with the dermatitis-producing cercariae T. physellae were present in the pond. Experimental lesions were produced in volunteers and by exposure to infected water while collecting snails along the shore of the pond.

OBSERVATIONS ON THE DISTRIBUTION OF FRESHWATER MOLLUSCA AND CHEMISTRY OF THE NATURAL WATERS IN THE SOUTH-EASTERN TRANSVAAL AND ADJACENT NORTHERN SWAZILAND

An extensive survey of the molluscan fauna and of the chemistry of the freshwaters of the Eastern Transvaal Lowveld has revealed no simple correlation between the two. The waters fall into four fairly distinct and geographically associated groups chiefly characterized by their calcium and magnesium content. The frequency of the two intermediate hosts of bilharziasis was found to be roughly proportional to the hardness of the water but as the latter, in this area, is associated with altitude and this again with temperature and stream gradient it is thought highly probable that the distribution of these snails is the result of the interaction of a complex of factors. None of the individual chemical constituents in any of the waters examined is regarded as outside the tolerance range of these snails. It is also concluded that under natural conditions this area would have had few waterbodies suitable for colonization by these snails but that the expansion of irrigation schemes has created ideal conditions for their rapid establishment throughout the area.

STUDIES ON ACQUIRED RESISTANCE TO SCHISTOSOMA MANSONI IN MICE EXPOSED TO X-IRRADIATED CERCARIAE

In the first part of this paper current information on acquired resistance to schistosomes is reviewed and related to factors which have led to divergent interpretations of experimental results.The author then reports on and discusses experiments performed by her on the development of challenge infections in mice exposed to X-irradiated cercariae of Schistosoma mansoni. While there is some evidence that resistance to S. mansoni may be developed by such exposure, the author considers present findings equivocal and stresses that further research is needed to clarify the situation.

OBSERVATIONS ON BILHARZIASIS AND THE POTENTIAL SNAIL HOSTS IN THE REPUBLIC OF THE CONGO (BRAZZAVILLE)

In 1962, the author conducted a preliminary investigation of bilharziasis in the Republic of the Congo (Brazzaville), at the request of the Government, in order to review existing information and work done on bilharziasis, to assess the prevalence and distribution of the disease, to make observations on the potential snail hosts, and to propose further suitable studies and control measures.Although little time was available for this study, it appears reasonable to conclude that Schistosoma haematobium is confined to a few foci in the west of the country, the main snail host being a new subspecies of Bulinus (B.) truncatus. Intestinal bilharziasis is apparently very rare, but systematic stool surveys have not been done; S. mansoni may be, or become, endemic at Dolisie, where Biomphalaria camerunensis is abundant. The main factors governing the restricted distribution of bilharziasis are discussed.Bilharziasis control appears to merit relatively low priority compared with that due to several other diseases, and the author concludes that bilharziasis is unlikely to become widespread in future years unless there is major environmental change, although the intensity of transmission may increase in some present endemic foci.

OBSERVATIONS ON THE TRANSMISSION OF SCHISTOSOMA HAEMATOBIUM AND SCHISTOSOMA BOVIS IN THE LAKE REGION OF TANGANYIKA

Previous investigations have shown that in the Lake Region of Sukumaland, Tanganyika, where Schistosoma haematobium is highly endemic, Bulinus (Physopsis) nasutus is responsible for the transmission of that schistosome in small, temporary rain pools. This area is one of low rainfall, and large artificial reservoirs are the chief source of water in the dry season. The role of these reservoirs in S. haematobium transmission was studied over a period of about a year.Previous work in South Africa had indicated the potential danger of bovine schistosomes to man. S. bovis is a very common parasite in cattle in the Lake Region, and a search for its intermediate host or hosts, previously unidentified, was therefore also made.The results of this double investigation suggest that large bodies of water are relatively unimportant in the transmission of both S. haematobium and S. bovis. Bulinus (Physopsis) africanus is shown to be a second intermediate of S. haematobium and a vector of S. bovis as well. Transmission of these parasites by this snail takes place principally in streams.