R. J. Knowles

Observations on Schistosoma bovis Sonsino, 1876

Summary Some biological characteristics of Schistosoma bovis Morocco, Sardinia and Iran in hamsters are described and discussed. Differences in infectivity, growth rates, maturation times, egg production and tissue deposition of eggs in the different strains are recorded. The egg shape and size of S. bovis Morocco, Sardinia, Iran, Kenya and S. mattheei are compared, as are the acid phosphatase, malate dehydrogenase and glucose 3-phosphate dehydrogenase isoenzymes. The compatibility/incompatibility of the same four strains of S. bovis to various members of the five species complexes of the genus Bulinus are recorded.

The influence of Calicophoron microbothrium on the susceptibility of Bulinus tropicus to Schistosoma bovis.

A total of 480 snails were collected from 3 habitats on the Mau Escarpment, Kenya, and were identified asBulinus tropicus. Of the 351 snails examined alive in London, 75 were infected withCalicophoron microbothrium, 39 withC. microbothrium andSchistosoma bovis, 1 withS. bovis. 24 with other species of trematodes and 212 were uninfected. Examination of digestive glands ofB. tropicus either uninfected or infected with bothC. microbothrium andS. bovis demonstrated that it is possible to differentiate between parasite and host enzyme activity using glucose phosphate isomerase. However, malate dehydrogenase enables a much clearer differentiation between the enzyme activity of the schistosome and that of the amphistome. Laboratory snail infection experiments demonstrated that it is possible successfully to infectB. tropicus withS. bovis if the snails have previously been exposed to miracidia ofC. microbothrium.

On Schistosoma curassoni, S. haematobium and S. bovis from Senegal: development in Mesocricetus auratus, compatibility with species of Bulinus and their enzymes

A comparative study on the development of Senegalese isolates of Schistosoma curassoni, S. haematobium and S. bovis in hamsters is reported, together with the compatibility of these parasites with Bulinus spp. and enzymes of adult worms. The mean worm return from 35 hamsters exposed to 100 cercariae each of S. curassoni was 11·5%, and of these 54% were paired, the remainder were single males. The growth and maturation of the worms were recorded from 40 to 100 days. The cross-over point (when paired females are of the same length as paired males) was reached at 42 days post-infection when the worms averaged 13·7 mm in length. The majority of tissue eggs (84·5%) were recovered from the liver, compared with 11% in the colon, 2·5% in the caecum and 1·6% in the small intestine. Estimates of the fecundity of paired females averaged 167 eggs/day per female worm. Snail-infection experiments showed S. curassoni to be compatible with B. umbilicatus, marginally compatible with B. senegalensis and incompatible with B...

Mating behaviour in mixed infections of Schistosoma haematobium and S. intercalatum

Summary Experiments were designed to examine the mating behaviour of Schistosoma haematobium and S. intercalatum in mixed infections in hamsters. Individual worms were identified by electrophoretic analysis of glucose-6-phosphate dehydrogenase which was characteristic for each isolate, in addition the uterine eggs of individual females were examined. The results showed that a specific mate recognition system does not exist for S. haematobium and S. intercalatum. The application of statistical tests to the results suggests that S. haematobium male worms are better at pairing with female worms of either species than S. intercalatum male worms. The significance of the results is discussed in relation to an occurrence of natural hybridization between these species in Cameroun.

On Schistosoma margrebowiei Le Roux, 1933: The morphology of the egg, miracidium and cercaria, the compatibility with species of Bulinus, and development in Mesocricetus auratus

SummaryThe morphology of the egg, miracidium, and cercaria of Schistosoma margrebowiei are described.The compatibility of S. margrebowiei with species of Bulinus has been examined. The parasite develops well in the diploid, tetraploid and octoploid snails of the truncatus/tropicus complex with overall infection rates of 38.1%, 30.1% and 29.1% respectively, and in reticulatus group snails (Bulinus wrighti) with an infection rate of 45.8% of those snails surviving the prepatent period. Only two species of the forskali complex (Bulinus bavayi, Aldabra; Bulinus beccarii, South Arabia) are slightly compatible, and snails of the africanus group are incompatible.The overall worm return from 24 hamsters exposed individually to 100 cercariae was 39.8%; 82.1% of the worms were paired, the remainder unpaired. The growth of the paired worms was recorded from 28–60 days. The prepatent period in hamsters is 33 days, in sheep 38 days. The mean egg production was 837 eggs/day in infections ranging from 33 to 60 days. Most eggs (80.9%) were deposited in the intestine, and only 18.2% were deposited in the liver. The parasite is pathogenic in hamsters, and peak death rate occurred in the 50–60 day group infections which coincided with the period of peak egg production.

Observations on an isolate of Schistosoma bovis from Tanzania.

The eggs ofSchistosoma bovis isolated from Misungwi, Tanzania measure 211.1 μm±18.4 long and 66.7 μm±5.4 wide. The parasite is naturally transmitted byBulinus africanus and is compatible in the laboratory with snails belonging to theB. truncatus, B. forskali, andB. reticulatus groups. The compatibility withB. africanus group snails is shared with isolates from Kenya and Sudan but not withS. bovis from more northern distributions. Enzyme analyses were carried out by isoelectric focusing. In adult worms, phosphoglucomutase (PGM), hexokinase (HK), malate dehydrogenase (MDH), and lactate dehydrogenase (LDH) proved to be monomorphic whereas two types of glucosephosphate isomerase (GPI), three types of glucose-6-phosphate dehydrogenase (G6PDH), and two types of acid phosphatase (AcP) were identified. Differences in the pI values of GPI and MDH of snail digestive glands and of larval parasites allowed the intramolluscan stages to be characterised. The GPI heterogeneity encountered was common both to the larval and adult parasites. The enzyme types identified inS. bovis are discussed both from an intra- and interspecific viewpoint.

Identification of schistosome hybrids and larval parasites using rRNA probes.

Observations have been made on the ribosomal RNA (rRNA) gene units of hybrid progeny produced by experimental crosses of S. haematobium × S. mattheei, S. mattheei × S. bovis and S. haematobium × S. intercalatum. Hybridisation of DNA probe pSM 889 to restriction endonuclease digested DNA extracted from adult worms showed that each parental form could be differentiated by differences in the rRNA gene unit. In each experimental cross the F1 hybrid generation produced a composite major banding pattern of the two parental species. No differences associated with the stage of development were detected in the major bands of hybridisation when DNA extracted from various life-cycle stages of S. mansoni and S. margrebowiei was digested with EcoR1 and hybridised with probe pSM 889. Prepatent infections of S. mansoni in Biomphalaria glabrata were detected 16 days post-infection utilising probe pSM 389 and dot blot analysis. Small numbers of intact cercariae dotted onto nitrocellulose were detected using probe pSM 389, 10 cercariae being the minimum number required for accurate determination.

OnSchistosoma leiperi Le Roux, 1955: scanning electron micrscopy of adult worms, compatibility with species ofBulinus, development inMesocricetus auratus, and isoenzymes

Adult male and femaleS. leiperi Zambia were examined by scanning electron microscopy. The oral and ventral suckers of both sexes are described, as is the gonopore of the female. The surface of the male is tuberculate whereas that of the female is non-tuberculate. The tubercles of some male worms are heavily spined., whereas those on other males are without spines. The gynaecophoric fold and canal are covered in spines.The compatibility ofS. leiperi Botswana, and Zambia with species ofBulinus has been examined. Both isolates develop well in snails belonging to theB. africanus group (B. africanus, B. globosus, B. hightoni, andB. nasutus) andB. reticulatus group (B. wrighti) but are incompatible with snails belonging to theBulinus tropicus/truncatus complex andB. forskali group.The overall worm return from 32 hamsters exposed to 100 cercariae each ofS. leiperi Botswana, was 26.1% and of these 85.1% of the worms were paired, the remainder single. The growth and maturation of the worms were recorded from 40–100 days. The prepatent period in hamsters is 49 days. Most eggs were recovered from the liver (79.5%). The following enzymes of adult male worms were examined by isoelectric focusing:S. leiperi Zambia — phosphoglucomutase (PGM), glucose-6-phosphate dehydrogenase (G6PDH), hexokinase (HK), acid phosphatase (AcP), glucose phosphate isomerase (GPI), malate dehydrogenase (MDH), and lactate dehydrogenase (LDH);S. leiperi Botswana — PGM, G6PDH, GPI.

Observations on some isoenzymes of strains ofSchistosoma bovis; S. mattheei, S. margrebowiei, andS. leiperi

SummaryThere are two main and two weak fractions of malate dehydrogenase isoenzyme common toSchistosoma bovis, S. leiperi, S. margrebowiei andS. mattheei: a major fraction at pI 8.56, seconded at pI 7.38, with weaker activity at pI 7.05 and pI 8.15. Variation in malate dehydrogenase occurs in some species/strainsen passage.In the strains ofS. bovis there are eight common bands of lactate dehydrogenase isoenzymes, at pI 6.85, 7.05, 7.16, 7.35, 7.50, 7.95, 8.03 and 8.38 with peak activity at pI 8.38 forS. bovis [Kisat, Kajulu (B. africanus) (B. forskali), Urudi-Kenya: Sardinia; Spain].S. mattheei has a peak band at pI 8.38, and also additional bands at pI 7.16, 7.50, 7.95, 8.52, 8.65 and 8.72.S. leiperi has peak activity at pI 7.74, and about 25% of the total activity is found between pI 8.38 and pI 9.50.S. margrebowiei shows peak activity at pI 8.38, seconded by a band at pI 8.86.The strains ofS. bovis show peak activity of acid phosphatase at pI 6.45;S. mattheei andS. leiperi at pI 7.52 andS. margrebowiei at pI 7.37. Despite intraspecific variation, the secondary bands place strains ofS. bovis from Western Kenya into one group and the strains from the Mediterranean area into another group, with the exception ofS. bovis Urudi, Kenya which, like the Mediterranean forms, possesses alkaline fractions above pI 7.50.S. bovis Iran does not possess fractions alkaline to pI 6.65 and therefore shows similarity to four strains from Western Kenya.

Observations onSchistosoma intercalatum in south-east gabon

Observations were made in the field and laboratory to determine the strain characteristics ofSchistosoma intercalatum in south-east Gabon. For an isolate from Franceville, data are given for egg shape, behaviour of cercariae, seven enzyme systems separated by isoelectric focusing, and intermediate host specificity. Isolates from Cameroun (Edea) and Zaire (Kisangani) were included in a comparative study of the enzymes; Franceville and Edea isolates resembled each other but differed from the Zaire isolate in hexokinase and phosphoglucomutase. The Franceville isolate was polymorphic in phosphoglucomutase and glucosephosphate isomerase. The sum of characters indicates thatS. intercalatum as known from south-east Gabon belongs to the strain found in Cameroun and western Gabon, rather than to the strain known from Zaire. More information is needed on strain distribution, particularly for an area including western Zaire and the Republic of the Congo, which appears to separate the two known strains.