Observations on the field transmission dynamics of Schistosoma mansoni and S. mattheei in southern Natal, South Africa

Parasitology ◽  
1985 ◽  
Vol 91 (2) ◽  
pp. 281-290 ◽  
Author(s):  
Fiona A. Donnelly ◽  
C. C. Appleton
Keyword(s):  
South Africa ◽  
Schistosoma Mansoni ◽  
Transmission Dynamics ◽  
Small Rivers ◽  
Seasonal Patterns ◽  
Infection Rates ◽  
Intermediate Hosts ◽  
Low Oxygen ◽  
Transmission Season ◽  
Extensive Growth

Cercarial transmission of Schistosoma mansoni and S. mattheei was monitored in two small rivers near Durban, South Africa. The seasonal patterns recorded corresponded to those already documented for these parasites. Tn the case of S. mansoni, however, this was interrupted at the height of the transmission season. The reason for this was believed to be very low oxygen concentrations in the snail habitat due to unusually extensive growth of the plant Ludwigia stolonifera over the water. The failure of the spring rains, which would normally have flushed the system is seen as contributing to this phenomenon. Infection rates in the snail intermediate hosts were low ( > 10%). A preponderance of male worms of both schistosome species was noted.

Temporal variation of Meiogymnophallus minutus infections in the first and second intermediate host

2010 ◽  
Vol 84 (4) ◽  
pp. 362-368 ◽  
Author(s):  
J. Fermer ◽  
S.C. Culloty ◽  
T.C. Kelly ◽  
R.M. O'Riordan
Keyword(s):  
Temporal Variation ◽  
Intermediate Host ◽  
Seasonal Patterns ◽  
Intertidal Flat ◽  
Infection Rates ◽  
Intermediate Hosts ◽  
Cerastoderma Edule ◽  
Scrobicularia Plana ◽  
Second Intermediate Host ◽  
First Intermediate Host

AbstractIn order to study seasonal patterns of Meiogymnophallus minutus infections in its intermediate hosts, bivalve samples were collected monthly between April 2008 and March 2009 from a high intertidal flat at Courtmacsherry Bay, Ireland. Infection rates in the first intermediate host Scrobicularia plana did not fluctuate significantly with season. Completely developed M. minutus cercariae appeared in daughter sporocysts from June and prevailed from July to October, indicating that transmission of M. minutus from its first to its second intermediate host is confined to this period of the year. All analysed individuals of the second intermediate host Cerastoderma edule were found to be infected with metacercariae. Infection levels significantly increased in September, suggesting recent cercarial invasions. Throughout the year, the majority of metacercariae were hyperinfected by the pathogenic microsporidian Unikaryon legeri. Spreading of hyperinfections was confined to spring and summer. Newly settled metacercariae were not affected by hyperparasitism and presumably retained their infectivity for half a year. Our findings suggest that the spreading of hyperinfections is correlated with higher water temperatures and that the entire metacercarial population has to rebuild every year as a consequence of hyperparasite-induced mortality.

Transmission of Schistosoma mansoni from man to snail: laboratory studies on the influence of snail and miracidial densities on transmission success

Parasitology ◽  
1982 ◽  
Vol 85 (2) ◽  
pp. 361-372 ◽  
Author(s):  
N. P. Carter ◽  
R. M. Anderson ◽  
R. A. Wilson
Keyword(s):  
Schistosoma Mansoni ◽  
Biomphalaria Glabrata ◽  
Snail Host ◽  
Transmission Dynamics ◽  
Laboratory Studies ◽  
Infection Rates ◽  
Snail Infection ◽  
Transmission Success ◽  
Laboratory Infection ◽  
The Relationship

SUMMARYThe relationship between infection success, the density of Schistosoma mansoni miracidia and the density of the snail host Biomphalaria glabrata was examined experimentally. Within laboratory infection arenas, the distribution of miracidial infections/snail was approximately uniform and the net rate of snail infection was directly positive binomial to miracidial density. In contrast, however, the rate of infection declined exponentially as snail density increased. Mathematical models are developed to aid in the estimation of infection rates and experimental results are discussed in the context of the transmission dynamics of schistosomiasis.

scholarly journals Leeches as the intermediate host for strigeid trematodes: genetic diversity and taxonomy of the genera Australapatemon Sudarikov, 1959 and Cotylurus Szidat, 1928

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Ewa Pyrka ◽  
Gerard Kanarek ◽  
Grzegorz Zaleśny ◽  
Joanna Hildebrand
Keyword(s):  
Intermediate Host ◽  
Life Cycles ◽  
Coi Gene ◽  
Small Rivers ◽  
Ecological Niches ◽  
Its2 Region ◽  
28S Rrna ◽  
Intermediate Hosts ◽  
Internal Transcribed Spacer Region ◽  
Wide Range

Abstract Background Leeches (Hirudinida) play a significant role as intermediate hosts in the circulation of trematodes in the aquatic environment. However, species richness and the molecular diversity and phylogeny of larval stages of strigeid trematodes (tetracotyle) occurring in this group of aquatic invertebrates remain poorly understood. Here, we report our use of recently obtained sequences of several molecular markers to analyse some aspects of the ecology, taxonomy and phylogeny of the genera Australapatemon and Cotylurus, which utilise leeches as intermediate hosts. Methods From April 2017 to September 2018, 153 leeches were collected from several sampling stations in small rivers with slow-flowing waters and related drainage canals located in three regions of Poland. The distinctive forms of tetracotyle metacercariae collected from leeches supplemented with adult Strigeidae specimens sampled from a wide range of water birds were analysed using the 28S rDNA partial gene, the second internal transcribed spacer region (ITS2) region and the cytochrome c oxidase (COI) fragment. Results Among investigated leeches, metacercariae of the tetracotyle type were detected in the parenchyma and musculature of 62 specimens (prevalence 40.5%) with a mean intensity reaching 19.9 individuals. The taxonomic generic affiliation of metacercariae derived from the leeches revealed the occurrence of two strigeid genera: Australapatemon Sudarikov, 1959 and Cotylurus Szidat, 1928. Phylogenetic reconstructions based on the partial 28S rRNA gene, ITS2 region and partial COI gene confirmed the separation of the Australapatemon and Cotylurus clades. Taking currently available molecular data and our results into consideration, recently sequenced tetracotyle of Australapatemon represents most probably Au. minor; however, unclear phylogenetic relationships between Au. burti and Au. minor reduce the reliability of this conclusion. On the other hand, on the basis of the obtained sequences, supplemented with previously published data, the metacercariae of Cotylurus detected in leeches were identified as two species: C. strigeoides Dubois, 1958 and C. syrius Dubois, 1934. This is the first record of C. syrius from the intermediate host. Conclusions The results of this study suggest the separation of ecological niches and life cycles between C. cornutus (Rudolphi, 1808) and C. strigeoides/C. syrius, with potential serious evolutionary consequences for a wide range of host–parasite relationships. Moreover, phylogenetic analyses corroborated the polyphyletic character of C. syrius, the unclear status of C. cornutus and the separate position of Cotylurus raabei Bezubik, 1958 within Cotylurus. The data demonstrate the inconsistent taxonomic status of the sequenced tetracotyle of Australapatemon, resulting, in our opinion, from the limited availability of fully reliable, comparative sequences of related taxa in GenBank.

Susceptibilities of Various Snail Intermediate Hosts of Schistosoma mansoni to Different Strains of the Parasite

1965 ◽  
Vol 39 (4) ◽  
pp. 363-376 ◽  
Author(s):  
M.F.A. Saoud
Keyword(s):  
Puerto Rico ◽  
Schistosoma Mansoni ◽  
Intermediate Hosts ◽  
Considerable Evidence ◽  
The Past ◽  
Host Parasite Relationship ◽  
Parasite Relationship ◽  
Different Strains ◽  
Host Parasite ◽  
Comprehensive Studies

In the past two decades, considerable evidence has accumulated in the literature about the differences in the susceptibility of various intermediate hosts of Schistosoma mansoni to different strains of the parasite. Comprehensive studies on this aspect of host-parasite relationship have been published by Files & Cram (1949), Abdel-Malek (1950) and Files (1951). The results of more recent studies have been reported by Wright (1962) and Saoud (1964).In the present paper, the writer has studied the susceptibility of four intermediate hosts of S. mansoni from Brazil, Puerto Rico, Egypt and Tanganyika to some strains of the parasite.

scholarly journals Behaviour of albino and melanic variants of Biomphalaria glabrata Say, 1818 (Mollusca: Planorbidae) following infection by Schistosoma mansoni Sambon, 1907

2009 ◽  
Vol 69 (1) ◽  
pp. 217-222 ◽  
Author(s):  
SM. Allegretti ◽  
JF. Carvalho ◽  
LA. Magalhães ◽  
EM. Zanotti-Magalhães
Keyword(s):  
Mortality Rate ◽  
Schistosoma Mansoni ◽  
Cross Sections ◽  
Biomphalaria Glabrata ◽  
Infection Rates ◽  
Susceptibility To Infection ◽  
Belo Horizonte

The behaviour of the albino and melanic variants of Biomphalaria glabrata of Belo Horizonte (MG. Brazil) was studied comparatively, in terms of their respective susceptibilities to infection by Schistosoma mansoni of the same origin, through observation of the elimination of cercariae for a three-month period and the calculation of mortality and infection rates, in control and in infected snails. The number of amoebocytes, granulocytes and hyalinocytes in the circulating hemolymph during different periods of infection was analyzed. The evolution of the infection in the tissues was observed by means of histological cross-sections. The melanic variant showed greater susceptibility to infection and a higher mortality rate. The albino variant showed a higher number of circulating amoebocytes, both granulocytes and hyalinocytes. A higher number of degenerated sporocysts were seen in the histological cross-sections of the albino variant. The results suggest that the melanic variant of B. glabrata was more susceptible to infection by S. mansoni than was the albino variant.

scholarly journals Experimental infection with Schistosoma mansoni of Biomphalaria straminea from different parts of the Northeast of Brazil

1986 ◽  
Vol 28 (3) ◽  
pp. 160-165 ◽  
Author(s):  
E. A. Malek ◽  
M. Z. Rouquayrol
Keyword(s):  
Schistosoma Mansoni ◽  
Puerto Rican ◽  
Experimental Infection ◽  
Snail Host ◽  
The State ◽  
Infection Rates ◽  
Biomphalaria Straminea ◽  
Albino Strain ◽  
Very High ◽  
Different Parts

In the western part of the State of Bahia Biomphalaria straminea and B. glabrata both occur, but in the majority of cases they do not share the same habitat. In the State of Ceará, however, B. straminea is the sole snail host of Schistosoma mansoni. In this survey, no naturally infected B. straminea was found among snails collected from Bahia and Ceará, evidently because of the very low infection rates. The susceptibility of laboratory-reared specimens to infection with a Puerto Rican strain of S. mansoni was then tested experimentally. In general, the snails showed very low susceptibility. The infection rates were 1.1% among snails from Redenção (Ceará); 2.3% in those from Pentecoste (Ceará); 2.9% in snails from São Desidério (Bahia), while they were very high among an albino strain (NIH) of B. glabrata used as control. Another group of B. straminea from São Desidério was exposed to a Bahian strain of S. mansoni and the infection rate was still very low (3.6%) Apparently, the very low susceptibility of B. straminea, despite high snail density, is correlated with moderate infection rates with S. mansoni among humans, as shown by the results of stool examinations conducted by SUCAM in the municipalities of Redenção and Pentecoste, in Ceará.

Helminth communities ofNectomys squamipesnaturally infected by the exotic trematodeSchistosoma mansoniin southeastern Brazil

2006 ◽  
Vol 80 (4) ◽  
pp. 369-375 ◽  
Author(s):  
A. Maldonado Júnior ◽  
R. Gentile ◽  
C.C. Fernandes-Moraes ◽  
P.S. D'Andrea ◽  
R.M. Lanfredi ◽  
...  
Keyword(s):  
Schistosoma Mansoni ◽  
Endemic Area ◽  
Dominant Species ◽  
Helminth Species ◽  
Southeastern Brazil ◽  
Infection Rates ◽  
Cestode Species ◽  
Intensity Of Infection ◽  
Helminth Communities ◽  
Subadult Female

AbstractThe water ratNectomys squamipesis endemic in Brazil and found naturally infected withSchistosoma mansoni. Helminth communities, their prevalences, intensity of infection and abundance inN. squamipesin an endemic area of schistosomiasis in the state of Rio de Janeiro, Brazil were studied. Four species of nematodes (Physaloptera bispiculata, Syphacia venteli,Hassalstrongylus epsilonandLitomosoides chagasfilhoi) were recovered in 85.3%, two trematodes (Schistosoma mansoniandEchinostoma paraensei) in 38.8% and one cestode species (Raillietinasp.) in 1.7% of rats examined. Rats were infected with up to five helminth species each, and these were highly aggregated in distribution. ForH. epsilonandS. venteli, intensities and abundances were higher in adult male and subadult female hosts, respectively.Hassaltrongylus epsilon,P. bispiculata,S. venteliandS. mansoniwere classified as dominant species,L. chagasfilhoiandE. paraenseias co-dominant andRaillietinasp. as subordinated. No significant correlation was found in the intensity of infecton between each pair of helminth species.Schistosoma mansoniwas not related to any other helminth species according to their infection rates, althougthS. mansoniwas well established in the natural helminth comunity of the water rat.

Jasus lalandii 'walkouts' or mass strandings in South Africa during the 1990s: an overview

2001 ◽  
Vol 52 (8) ◽  
pp. 1085 ◽  
Author(s):  
Andrew C. Cockcroft
Keyword(s):  
South Africa ◽  
West Coast ◽  
The Other ◽  
Fishing Industry ◽  
Low Oxygen ◽  
Rock Lobster ◽  
The West ◽  
Hypoxic Conditions ◽  
Oxygen Conditions ◽  
Mass Mortalities

Faunal mass mortalities are a sporadic, but not uncommon, feature of the West and South coasts of South Africa. Five mass mortalities of West Coast rock lobsterJasus lalandii, including three of the most severe ever recorded in South Africa, occurred in the 1990s and resulted in the stranding of about 2263 tonnes of lobster. The bulk (97%) of the loss occurred in the last three years of the decade. The five events occurred within an 80 km stretch of coastline that straddled two fishing zones and resulted from hypoxic conditions associated with highbiomass dinoflagellate blooms. In each case, the quantity of lobsters stranded was directly related to the extent or duration of low-oxygen conditions. Small females constituted the bulk of the lobster stranded in most events. The lobster fisheries in the affected fishing zones suffered severe impacts. Recovery in one zone appears to be extremely slow, whereas the other zone is more resilient. Not only would a continuation of the trend of increasing frequency and severity of lobster strandings devastate the rock-lobster fishing industry and the employment prospects of small fishing communities, but it could also seriously affect the ecology of the region.

scholarly journals Community diversity reduces Schistosoma mansoni transmission, host pathology and human infection risk

2009 ◽  
Vol 276 (1662) ◽  
pp. 1657-1663 ◽  
Author(s):  
Pieter T.J Johnson ◽  
Peder J Lund ◽  
Richard B Hartson ◽  
Timothy P Yoshino
Keyword(s):  
Community Structure ◽  
Schistosoma Mansoni ◽  
Host Density ◽  
Biodiversity Loss ◽  
Infection Risk ◽  
Human Infection ◽  
Host Community ◽  
Community Diversity ◽  
Complex Life Cycle ◽  
Intermediate Hosts

Global biodiversity loss and disease emergence are two of the most challenging issues confronting science and society. Recently, observed linkages between species-loss and vector-borne infections suggest that biodiversity may help reduce pathogenic infections in humans and wildlife, but the mechanisms underlying this relationship and its applicability to a broader range of pathogens have remained speculative. Here, we experimentally evaluated the effects of host community structure on transmission of the human pathogen, Schistosoma mansoni , which alternates between snail intermediate hosts and vertebrate definitive hosts. By manipulating parasite exposure and community diversity, we show that heterospecific communities cause a 25–50 per cent reduction in infection among snail hosts ( Biomphalaria glabrata ). Infected snails raised alongside non-host snails ( Lymnaea or Helisoma sp.) also produced 60–80 per cent fewer cercariae, suggesting that diverse communities could reduce human infection risk. Because focal host density was held constant during experiments, decreases in transmission resulted entirely from diversity-mediated pathways. Finally, the decrease in infection in mixed-species communities led to an increase in reproductive output by hosts, representing a novel example of parasite-mediated facilitation. Our results underscore the significance of community structure on transmission of complex life-cycle pathogens, and we emphasize enhanced integration between ecological and parasitological research on the diversity–disease relationship.

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