PubMed Health⌕ Search

Biomedical subjects

F Frandsen

Publications and source records attributed to F Frandsen.

At least 55 records · Page 3Linked to original sources
PubMed1987

Seasonal patterns in the transmission of Schistosoma haematobium, S. mattheei and S. mansoni in the highveld region of Zimbabwe.

The pattern of fluctuation in the population size of Bulinus globosus and Biomphalaria pfeifferi, in their infection rates with Schistosoma haematobium/S. mattheei and S. mansoni, respectively, and in the cercarial population size as monitored using hamster immersions, was elucidated in streams in the temperate highveld region of Zimbabwe over a 27-month period during 1982-1984. The results revealed that transmission of S. mansoni was erratic and unpredictable without a clearcut seasonal transmission pattern. In contrast, transmission of S. haematobium and S. mattheei exhibited a marked seasonal pattern, being most intensive during the hot, dry season (September-November) and markedly reduced during the cold, dry season (June-August). During the rainy (December-February) and warm, post-rainy (March-May) seasons transmission was moderate and variable, but occasionally intensive. The results also showed that rodent immersion is to be preferred to measurements of snail population size and snail infection rate in elucidating seasonality of transmission of schistosomiasis.

Animals↗
PubMed1985

A study of the biological characteristics of a hybrid line between male Schistosoma haematobium (Dar es Salaam, Tanzania) and female S. intercalatum (Edea, Cameroun).

The viability of a hybrid between male Schistosoma haematobium (Dar es Salaam, Tanzania) and female S. intercalatum (Edea, Cameroun) was studied for up to the F7 hybrid generation and the biological characteristics of the hybrid were compared with those of each of the parental species. Using the total cercarial production/100 exposed snails/5 weeks value (TCP) as an index the hybrid miracidial infectivity to Bulinus forskalii (Kinshasa, Zaire), the host snail for S. intercalatum, remained comparable to that of S. intercalatum for up to at least the F5 generation and the TCP values for the hybrid/B. wrighti combination remained for up to the F7 generation intermediate between those of the parental species in B. wrighti. The hybrid also retained the infectivity for up to at least the F5 generation to B. globosus (Mazeras, Kenya), the host snail for S. haematobium, but the TCP values for the hybrid/B. globosus combination remained consistently lower than that of the S. haematobium/B. globosus combination. The hybrid cercarial infectivity to hamsters was for up to the F7 generation comparable to that of both parental species and the egg production capacity/worm pair/day of production of the F1 hybrid generation exceeded in both hamsters and mice that of both parental species. However, the egg production capacity subsequently decreased with that of the F3 to F6 generations in hamsters and with that of the F2 and F5 generations in mice being comparable to that of S. intercalatum. The pattern of distribution of eggs in tissue of hamsters of the F1 and F2 generations resembled that of S. haematobium and S. intercalatum, respectively, but the distributional pattern of the F3 to F6 generations deviated markedly from that of both the parental species and the preceding hybrid generations. The hybrid cercarial infectivity to mice and the pattern of egg distribution corresponded to that of S. intercalatum. The egg morphology of the P1 generation corresponded to that of S. intercalatum while that of the F1, F2 and F3 hybrid generations exhibited great polymorphism with a range of shapes through those of the parental species but with most eggs being intermediate in shape. However, the eggs of the F4 to F7 hybrid generations exhibited less polymorphism and resembled those of S. bovis in both size and shape.

Animals↗
PubMed1983

A review of the biology and transmission ecology of African bovine species of the genus Schistosoma.

The present paper reviews the information available concerning the biology and transmission ecology of the African bovine species Schistosoma bovis, S. mattheei, S. margrebowiei and S. leiperi. Criteria for species identification (egg morphology, intermediate host spectra, definitive host-parasite relationships, etc.) are listed and the geographical distribution of the four species and factors determining the relative occurrence within their overall distributional ranges are described. S bovis and S. mattheei occur north and south of 10 degrees S, respectively, and S. margrebowiei occurs mainly, and S. leiperi only, in southern central Africa. Definitive host-related factors (susceptibility, water contact pattern, ect.) providing the background for being a primary definitive host and the primary definitive host spectra for the four schistosome species are described. The primary definitive host spectrum for S. margrebowiei and S. leiperi comprise lechwe, puku and waterbuck, for S. mattheei lechwe, puku, waterbuck plus cattle, and for S. bovis cattle and possibly also some of the listed antelope species. In addition, wild bovines and cattle may provide a reservoir of S. mattheei and S. margrebowiei in humans, but wild bovines and domestic stock play no major role in the transmission of other human species of schistosomes. The intermediate snail host spectra of S. mattheei and S. leiperi only comprise members of the Bulinus africanus species complex; S. bovis is transmitted by members of the B. truncatus, B. africanus and B. forskalii species groups, and S. margrebowiei is transmitted by members of the B. forskalii species group and possibly also by members of the B. tropicus and B. truncatus species groups. Factors determining the transmission ecology of the four schistosome species, and thereby the epidemiology of bovine schistosomiasis, are discussed. Influential factors comprise environmental conditions mediated via the effect of these on the size of the snail host population and on the rate of the intramolluscan development, behavioural patterns of the definitive host population and the course of the infection in the definitive host as related to aspects of susceptibility and level of endemicity. The epidemiological pattern (prevalence and intensity of infection, seasonality of transmission, etc.) is described and exemplified, and it is finally concluded that the increasing water conservation and changing methods of husbandry may result in bovine schistosomiasis becoming a major veterinary problem in Africa.

Africa↗
PubMed1983

Studies on the relationship between Schistosoma and their intermediate hosts. V. The genus Bulinus and Schistosoma bovis from Iringa, Tanzania.

The relationship between an isolate of Schistosoma bovis from Iringa, Tanzania, and various species of the host snail genus Bulinus from East Africa was studied using the total cercarial production per 100 exposed snails over a period of 4 weeks following patency as an index of the compatibility. All populations of Bulinus forskalii and B. africanus tested exhibited a high level of susceptibility while the populations of B. truncatus and B. globosus tested were either refractory or of low to moderately low susceptibility. All populations of B. abyssinicus, B. canescens, B. nasutus and B. tropicus tested were refractory. It is suggested that B. africanus is the most important host snail for S. bovis in East Africa, that B. forskalii at least locally may contribute significantly to the transmission and that B. truncatus and B. globosus only play a limited role in the transmission.

Animals↗
PubMed1983

9-acridinyl and 2-methoxy-6-chloro-9-acridinyl derivatives of aliphatic di-, tri-, and tetraamines. Chemistry, cytostatic activity, and schistosomicidal activity.

9-acridinyl derivatives of 1,6-hexanediamine, 1,8-octanediamine, bis(3-aminopropyl)amine, N,N'-bis(3-amino-propyl)piperazine, and N-ethyl-1,6-hexanediamine in the form of their hydrochlorides were prepared in high yields and converted into potential hetero bis DNA intercalating diacridines. The corresponding potential homo bis DNA intercalating reagents were prepared by heating the above amines with 9-chloroacridines. The chemical stability of the acridines was examined. Their cytostatic activity against Cloudman melanoma cells, in vitro, has been determined. The strongest cytostatic activity was observed for the acridine derivatives of the tri- and tetraamines. The schistosomicidal activity of selected acridine and diacridine derivatives against Schistosoma mansoni in mice was found to be insignificant. The S. mansoni egg development was apparently suppressed by this treatment.

Aminoacridines↗
PubMed1982

Schistosoma intercalatum (Fisher, 1934) infection in sheep.

Parasitological and clinico-pathological aspects of Schistosoma intercalatum infection in sheep were studied after exposure to 5000 cercariae per animal. It was shown that the infection, in spite of relatively high tissue egg counts, only gave rise to low-grade clinico-pathological manifestations with almost unaffected blood parameters. The parasites were mainly located in the lower part of the intestinal tract, and the number of eggs being passed in faeces was very low.

Animals↗
PubMed1982

Clinical pathology of Schistosoma bovis infection in sheep.

The clinical pathology of Schistosoma bovis infection in sheep was studied for a period of 16 weeks. The length of the prepatent period was 10 weeks, and reduced haemoglobin and packed cell volume values and increased serum gammaglutamyl-transpeptidase levels were observed from eight to 10 weeks after infection and onwards. The bromsulphalein clearance rate was significantly reduced 16 weeks after infection. Eosinophil counts were increased six and eight weeks after infection and towards the end of the experiment.

Animals↗
PubMed1981

Further studies on resistance to Fasciola hepatica and Echinostoma revolutum in mice infected with Schistosoma sp.

Schistosoma sp. induced cross-resistance to a challenge with Fasciola hepatica and Echinostoma revolutum was studied in mice. Primary patent 56-days-old S. intercalatum and S. bovis infections stimulated a statistically significant level of resistance to a challenge with F. hepatica, and primary patent 100-day-old S. bovis infections induced an almost complete resistance to a challenge with E. revolutum. Primary single-sex S. mansoni infections, either male or female, aged 90 days did not stimulate any resistance to a challenge with E. revolutum. A primary infection with S. mansoni aged 70 days induced a marked reduction (94.1--100%) in the E. revolutum worm recovery already 2 h post-challenge as compared with that of the E. revolutum challenge control group and complete elimination of the echinostome worm population in S. mansoni infected mice had taken place 24 h after challenge. E. revolutum worm populations established in mice harbouring newly patent 36-day-old S. mansoni infections persisted unchanged for a period of at least 33 days into the patent period of the schistosome infection in spite of development of a complete resistance to a challenge with E. revolutum metacercariae during this period.

Animals↗
PubMed1981

Resistance to Fasciola hepatica in sheep harbouring primary Schistosoma bovis infections.

A substantial level of resistance to a heterologous challenge with Fasciola hepatica was demonstrated in sheep harbouring primary non-patent (two- to three-week-old) and newly patent (seven- to eight-week-old) Schistosoma bovis infections, the liver-fluke burdens being reduced by 70% and 93%, respectively, (p less than 0.01) in these groups compared with that of the challenge control group. The resistance was also reflected in less pronounced F. hepatica-induced liver damage and presumably also in a reduction of the egg-production capacity per established liver-fluke. In contrast, a corresponding heterologous resistance to challenge with F. hepatica could not be demonstrated in sheep harbouring primary 16- to 17-week-old S. bovis infections. Possible, presumably immunological, mechanisms involved in the observed cross-resistance are discussed, as is the possible practical relevance of this cross-resistance phenomenon in attempts to vaccinate sheep against F. hepatica.

Animals↗
PubMed1981

Resistance to Fasciola hepatica in calves harbouring primary patent Schistosoma bovis infections.

A substantial resistance to a heterologous challenge with Fasciola hepatica was demonstrated in calves harbouring primary patent Schistosoma bovis infections of an age of 10 weeks at challenge, the mean worm burden being reduced by 29.9% (p less than 0.025) in calves primarily infected with S. bovis as compared with that of the challenge control group. The heterologous resistance was also evidenced by less pronounced liver tissue damage and lower serum gammaglutamyl-transpeptidase values in the S. bovis-infected animals compared with the challenge control group.

Animals↗
PubMed1981

Homologous immunotolerance and decreased resistance to Schistosoma mansoni in Echinostoma revolutum-infected mice.

Homologous immunotolerance was demonstrated in Echinostoma revolutum infections in the mouse. High-level infections of about 15 worms were not expelled for a period of at least 61 days following infection, whereas low-level infections of about 10 to 12 worms or below were eliminated completely between day 47 and 61 after infection. A primary, 20- to 33-day-old, heavy E. revolutum infection in the mouse produced a statistically significant increase in the number of Schistosoma mansoni recovered in challenge infections. Worm burdens increased by 65.7 to 90.6% as compared with those of the respective S. mansoni challenge control groups.

Animals↗