scholarly journals Endemicity of Paragonimus and paragonimiasis in Sub-Saharan Africa: A systematic review and mapping reveals stability of transmission in endemic foci for a multi-host parasite system

2021 ◽  
Vol 15 (2) ◽  
pp. e0009120
Author(s):  
Muriel Rabone ◽  
Joris Wiethase ◽  
Paul F. Clark ◽  
David Rollinson ◽  
Neil Cumberlidge ◽  
...  
Keyword(s):  
Systematic Review ◽  
Life Cycle ◽  
Current Knowledge ◽  
Temporal Stability ◽  
Central Africa ◽  
Sub Saharan Africa ◽  
Similar Distribution ◽  
Intermediate Hosts ◽  
Tropical Regions ◽  
Larval Stages

Paragonimiasis is caused by zoonotic trematodes of Paragonimus spp., found in Asia, the Americas and Africa, particularly in tropical regions. These parasites have a complex, multi-host life cycle, with mammalian definitive hosts and larval stages cycling through two intermediate hosts (snails and freshwater decapod crustaceans). In Africa, paragonimiasis is particularly neglected, and remains the only human parasitic disease without a fully characterised life cycle. However paragonimiasis has potentially significant impacts on public health in Africa, and prevalence has likely been underestimated through under-reporting and misdiagnosis as tuberculosis due to a similar clinical presentation. We identified the need to synthesise current knowledge and map endemic foci for African Paragonimus spp. together with Poikilorchis congolensis, a rare, taxonomically distant trematode with a similar distribution and morphology. We present the first systematic review of the literature relating to African paragonimiasis, combined with mapping of all reported occurrences of Paragonimus spp. throughout Africa, from the 1910s to the present. In human surveys, numerous reports of significant recent transmission in Southeast Nigeria were uncovered, with high prevalence and intensity of infection. Overall prevalence was significantly higher for P. uterobilateralis compared to P. africanus across studies. The potential endemicity of P. africanus in Côte d’Ivoire is also reported. In freshwater crab intermediate hosts, differences in prevalence and intensity of either P. uterobilateralis or P. africanus were evident across genera and species, suggesting differences in susceptibility. Mapping showed temporal stability of endemic foci, with the majority of known occurrences of Paragonimus found in the rainforest zone of West and Central Africa, but with several outliers elsewhere on the continent. This suggests substantial under sampling and localised infection where potential host distributions overlap. Our review highlights the urgent need for increased sampling in active disease foci in Africa, particularly using molecular analysis to fully characterise Paragonimus species and their hosts.

Life cycle studies on two Digenea, Paradistomum geckonum (Dicrocoeliidae) and Mesocoelium sociale (Mesocoeliidae), in geckonid lizards from Indonesia

1987 ◽  
Vol 65 (10) ◽  
pp. 2491-2497 ◽  
Author(s):  
Murray J. Kennedy ◽  
L. M. Killick ◽  
M. Beverley-Burton
Keyword(s):  
Life Cycle ◽  
Intermediate Host ◽  
Intermediate Hosts ◽  
Larval Stages ◽  
Hemidactylus Frenatus ◽  
Pulmonate Gastropod ◽  
First Intermediate Host

Life cycle studies of Paradistomum geckonum (Dicrocoeliidae) were attempted experimentally. The pulmonate gastropod Lamellaxis gracilis served as the first intermediate host; geckonid lizards (Cosymbotus platyurus, Gehyra mutilata, and Hemidactylus frenatus) served as definitive hosts. The life cycle of Mesocoelium sociale (Mesocoeliidae) was studied in naturally infected first intermediate hosts (L. gracilis, Huttonella bicolor) and experimentally in geckonid definitive hosts (C. platyurus, G. mutilata, and H. frenatus). Some naturally infected L. gracilis were infected concurrently with larval stages of both digeneans. Second intermediate hosts, presumed to be arthropods, were experimentally unnecessary. Metacercariae of P. geckonum were not found. Cercariae of M. sociale formed encysted metacercariae in the same individual snails.

scholarly journals Interactions between hydatid cyst and regulated cell death may provide new therapeutic opportunities

Parasite ◽  
2019 ◽  
Vol 26 ◽  
pp. 70 ◽  
Author(s):  
Sirous Mehrani Moghaddam ◽  
Stephane Picot ◽  
Ehsan Ahmadpour
Keyword(s):  
Immune Response ◽  
Cell Death ◽  
Current Knowledge ◽  
Cyst Formation ◽  
Response Modulation ◽  
Intermediate Hosts ◽  
New Horizons ◽  
Larval Stages ◽  
Zoonotic Infections ◽  
Regulated Cell Death

Cystic echinococcosis and alveolar echinococcosis are chronic zoonotic infections, transmitted throughout the world. Development of the cestode larval stages in the liver and lungs causes damage to intermediate hosts, including humans. Several pathways leading to the suppression of host immune response and the survival of the cysts in various hosts are known. Immune response modulation and regulated cell death (RCD) play a fundamental role in cyst formation, development and pathogenesis. RCD, referring to apoptosis, necrosis and autophagy, can be triggered either via intrinsic or extrinsic cell stimuli. In this review, we provide a general overview of current knowledge on the process of RCD during echinococcosis. The study of interactions between RCD and Echinococcus spp. metacestodes may provide in-depth understanding of echinococcosis pathogenesis and open new horizons for human intervention and treatment of the disease.

How are soil carbon and tropical biodiversity related?

2016 ◽  
Vol 43 (3) ◽  
pp. 231-241 ◽  
Author(s):  
DOUGLAS SHEIL ◽  
BRENTON LADD ◽  
LUCAS C. R. SILVA ◽  
SHAWN W. LAFFAN ◽  
MIRIAM VAN HEIST
Keyword(s):  
Carbon Content ◽  
Soil Carbon ◽  
Current Knowledge ◽  
Central Africa ◽  
Federal District ◽  
Biological Conservation ◽  
Tropical Regions ◽  
Central Brazil ◽  
Soil Carbon Content ◽  
Tropical Biodiversity

SUMMARYThis article discusses how biological conservation can benefit from an understanding of soil carbon. Protecting natural areas not only safeguards the biota but also curtails atmospheric carbon emissions. Opportunities for funding biological conservation could potentially be greater if soil carbon content is considered. In this article current knowledge concerning the magnitude and vulnerability of soil carbon stocks is reviewed and the relationship of these stocks to biological conservation values is explored. Looking at two relatively well-studied tropical regions we find that 15 of 21 animal species of conservation concern in the Virunga Landscape (Central Africa), and nine of ten such species in the Federal District of Brazil (Central Brazil), rely on carbon-rich habitats (alluvial and/or wetlands). At national scales, densities of species, endemics and threatened taxa (plants, mammals, birds, reptiles, amphibians and fish) show positive and significant relations with mean soil carbon content in all but two cases (threatened amphibians and threatened fish). Of more than 1000 threatened species in 37 selected tropical nations, 85% rely on carbon-rich habitats. This tendency is observed in plants, mammals, reptiles, amphibians and crustaceans, while birds appear more evenly distributed. Research to clarify and explore these relationships is needed. Soil carbon offers major opportunities for conservation.

Paragonimusand paragonimiasis in West and Central Africa: unresolved questions

Parasitology ◽  
2018 ◽  
Vol 145 (13) ◽  
pp. 1748-1757 ◽  
Author(s):  
Neil Cumberlidge ◽  
David Rollinson ◽  
Jozef Vercruysse ◽  
Louis-Albert Tchuem Tchuenté ◽  
Bonnie Webster ◽  
...  
Keyword(s):  
Life Cycle ◽  
Central Africa ◽  
Disease Diagnosis ◽  
World Health ◽  
Intermediate Hosts ◽  
Public Health Importance ◽  
Resistant Tuberculosis ◽  
Lung Fluke ◽  
The 1960S ◽  
Health Organization

AbstractParagonimiasis, human lung fluke disease, is a foodborne anthropozoonosis caused by the trematodes assigned toParagonimusand is regarded by the World Health Organization as a Neglected Tropical Disease (NTD). The life cycle of this medically important parasite centres on a complex freshwater biological community that includes two intermediate hosts: a mollusc and a decapod, usually a brachyuran. Although there is a perception that the biology, symptoms, diagnosis and treatment ofParagonimusis well understood, in reality, this is not the case, especially in Africa. Much remains unknown concerning the life-cycle of the parasite, its transmission, the current epidemiology of the disease, diagnosis and the effectiveness of treatment. Furthermore, cases of paragonimiasis may be misdiagnosed as resistant tuberculosis (TB) because of the similar pulmonary symptoms and no remission after anti TB therapy. The endemic foci of human paragonimiasis in Africa have been reported mainly in the forest zones of Upper Guinea (Liberia, Guinea and Ivory Coast) and Lower Guinea (Nigeria, Cameroon, Equatorial Guinea and Gabon). Despite the perceived medical importance of paragonimiasis, relatively little attention has been paid to this NTD since its discovery in Africa in the 1960s. This review focuses on the current understanding of the life cycle and transmission ofParagonimusin Africa, discusses its diagnosis and public health importance and highlights many outstanding gaps in the knowledge that still exist for this NTD.

scholarly journals LARVAL STAGES OF PHYLLODISTOMUM SP. (DIGENEA, GORGODERIDAE) FROM THE DUCK MUSSELS ANODONTA ANATINA IN UKRAINE

2013 ◽  
Vol 47 (6) ◽  
pp. 37-42 ◽  
Author(s):  
O. S. Kudlai ◽  
L. N. Yanovich
Keyword(s):  
Life Cycle ◽  
Ventral Sucker ◽  
Experimental Infection ◽  
Definitive Host ◽  
Morphological Features ◽  
Carassius Carassius ◽  
Body Proportions ◽  
Intermediate Hosts ◽  
Free Swimming ◽  
Larval Stages

Abstract Rhopalocercous cercariae were found in the gonads of duck mussels, Anodonta anatina (Linnaeus, 1758) collected from the Sluch River (Zhytomyr oblast, Ukraine). The morphological features observed led to conclusion that this species belonged to the genus Phyllodistomum Braun, 1899. Obtained results suggested that the second intermediate hosts in the life cycle of this trematode were absent. Free-swimming cercariae were observed encysting in water. This species is similar to Phyllodistomum pseudofolium Nybelin, 1926 by overall body proportions and ratio of suckers: lengths of oral to ventral sucker 1 : 1.1; widths of the same organs 1 : 1.2. To confirm the taxonomic position of the species found and establish a possible relationship between it and P. pseudofolium an experimental infection of fish Carassius carassius (Linnaeus, 1758) as potential definitive host was performed. The infection was not successful. Descriptions and figures of all detected larval stages of Phyllodistomum sp. are provided.

scholarly journals The survival and dispersal of Taenia eggs in the environment: what are the implications for transmission? A systematic review

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Famke Jansen ◽  
Pierre Dorny ◽  
Sarah Gabriël ◽  
Veronique Dermauw ◽  
Maria Vang Johansen ◽  
...  
Keyword(s):  
Systematic Review ◽  
Current Knowledge ◽  
Intermediate Hosts ◽  
Egg Survival ◽  
Future Studies ◽  
Bovine Cysticercosis ◽  
Factors Influencing ◽  
Geographical Regions ◽  
Route Of Transmission ◽  
Wastewater Treatment Systems

AbstractTaenia spp. are responsible for a substantial health and economic burden in affected populations. Knowledge of the fate of the eggs of Taenia spp. in the environment and of other factors facilitating the transmission of eggs to intermediate hosts is important for the control/elimination of infections caused by Taenia spp. The aim of this systematic review was to summarize current knowledge of the factors influencing the survival and dispersal of Taenia spp. eggs in the environment. Publications retrieved from international databases were systematically reviewed. Of the 1465 papers initially identified, data were ultimately extracted from 93 papers. The results of this systematic review indicate that survival is favoured at moderate temperatures (0–20 °C). Humidity seems to affect the survival of Taenia spp. eggs more than temperature. Under field circumstances, Taenia spp. eggs have been found to survive for up to 1 year. Taenia spp. eggs are commonly found on vegetables (0.9–30%) and in soil and water samples (0–43%), with their presence posing a risk to the consumer. Invertebrates may act as transport hosts, transferring the infection to an intermediate host, but the importance of this route of transmission is still open to question. Wastewater treatment systems are not capable of entirely eliminating Taenia spp. eggs. Access to surface water and the use of sewage sludge as fertilizer on pastures are important risk factors for bovine cysticercosis. Although information on the survival and spread of Taenia spp. eggs is available, in general the data retrieved and reviewed in this article were old, focused on very specific geographical regions and may not be relevant for other areas or not specific for different Taenia spp. Furthermore, it is unknown whether egg survival differs according to Taenia sp. Future studies are necessary to identify sustainable methods to identify and inactivate parasite eggs in the environment and reduce their spread.

Molecular evidence linking the larval and adult stages of Mexiconema cichlasomae (Dracunculoidea: Daniconematidae) from Mexico, with notes on its phylogenetic position among Dracunculoidea

2018 ◽  
Vol 93 (05) ◽  
pp. 580-588 ◽  
Author(s):  
A.L. May-Tec ◽  
A. Martínez-Aquino ◽  
M.L. Aguirre-Macedo ◽  
V.M. Vidal-Martínez
Keyword(s):  
Life Cycle ◽  
Developmental Stages ◽  
Gravid Female ◽  
Small Subunit ◽  
Phylogenetic Position ◽  
Molecular Evidence ◽  
Intermediate Hosts ◽  
Larval Stages ◽  
The Family ◽  
Cichlasoma Urophthalmus

AbstractWe describe the larval developmental stages and life cycle of the dracunculid nematodeMexiconema cichlasomaein both the intermediate,Argulus yucatanus(Crustacea: Branchiura), and definitive hosts,Cichlasoma urophthalmus(Perciformes: Cichlidae), from the Celestun tropical coastal lagoon, Yucatan, Mexico. The morphological analyses showed significant differences between the total length of L1 found inM. cichlasomaegravid female and L2–L3 inA. yucatanus.This result indicates that theM. cichlasomaelarval development occurs in the intermediate host. We obtained sequences from the small subunit (SSU) ribosomal marker from larval stages ofM. cichlasomaeinA. yucatanusand adult nematodes inC. urophthalmus. Our morphological and molecular results support conspecificity betweenM. cichlasomaelarvae inA. yucatanusand the adult stages inC. urophthalmus. We briefly discuss the phylogenetic position ofM. cichlasomaeamong the Daniconematidae, and provide evidence of the monophyly of the daniconematids associated with branchiurid intermediate hosts. Based on the phylogenetic results, we support the transfer of theMexiconemagenus to the family Skrjabillanidae and do not support the lowering of family Daniconematidae to subfamily.

Children, snails and worms: the Brachylaima cribbi story

2016 ◽  
Vol 37 (1) ◽  
pp. 30 ◽  
Author(s):  
Andrew R Butcher
Keyword(s):  
Life Cycle ◽  
South America ◽  
South Australia ◽  
Land Snails ◽  
Intermediate Hosts ◽  
Larval Stages ◽  
Wide Range ◽  
Terrestrial Life ◽  
North And South America ◽  
North And South

Brachylaimids are parasitic trematode fluke worms that have a terrestrial life cycle involving land snails and slugs as the first and/or second intermediate hosts for the cercarial and metacercarial larval stages. A wide range of mammals, birds, reptiles and amphibians are the definitive hosts for the adult worm. Brachylaima spp. have been reported from most continents including Europe, Africa, Asia, North and South America and Australia. There are over 70 described species in the genus with seven species indigenous to Australia. Although Brachylaima spp. are a cosmopolitan terrestrial trematode they have not been recorded to infect humans other than the three Brachylaima cribbi infections reported in two children and an adult from South Australia.

Auto-infection by Echinostoma spp. cercariae in Helisoma anceps

2015 ◽  
Vol 60 (4) ◽  
Author(s):  
Michael R. Zimmermann ◽  
Kyle E. Luth ◽  
Gerald W. Esch
Keyword(s):  
Life History ◽  
Life Cycle ◽  
Life History Strategy ◽  
Null Model ◽  
Life Cycle Stage ◽  
Negative Consequences ◽  
Intermediate Hosts ◽  
Morphological Transformation ◽  
Larval Stages ◽  
Transmission Success

AbstractAuto-infection is a life history strategy used by many parasitic organisms, including digenetic trematodes. The process of autoinfection most frequently involves the transfer of a life cycle stage of the parasite from one site to another inside the same host, usually accompanied by morphological transformation. Moreover, among trematodes, the stage being transferred may also move from one host to another in completing the life cycle, i.e., an indirect cycle. Echinostoma spp. parasites offer the opportunity to study auto-infection because they utilize gastropods as both first and second intermediate hosts. Rejection of a null model predicting independent infection of first and second intermediate larval stages coupled with the presence of rediae being the best predictor of metacercariae prevalence and intensity suggests that auto-infection by Echinostoma spp. cercariae is occurring in their molluscan hosts. Shell length was also found to be a significant predictor of metacercariae intensity in the snails hosts, but this is most likely attributed to larger snails being more commonly infected with Echinostoma spp. rediae as opposed to an increased likelihood of cercariae infection. Auto-infection as a life history strategy increases transmission success of the parasite, but may also have negative consequences for the parasite that necessitate auto-infection coupled with the release of cercariae to maximize transmission success and host survival.

Cestodes (tapeworms)

2020 ◽  
pp. 1520-1528
Author(s):  
Richard Knight
Keyword(s):  
Life Cycle ◽  
The Body ◽  
Intermediate Hosts ◽  
Larval Stages ◽  
Terrestrial Life ◽  
Gut Mucosa ◽  
A Chain ◽  
Serious Disease

Adult tapeworms maintain anchorage to the host small-gut mucosa by means the scolex, a holdfast structure. The rest of the body forms the strobila and consists of a chain of flattened proglottids, which proliferate just behind the scolex. The life cycle then includes larval stages in one or more intermediate hosts. Many species of tapeworm, all zoonoses, infect humans as adult worms or larval stages. Serious disease can result when larval stages occur accidentally in humans, whereas infections by the adult stages often cause little harm. Two groups of cestode infect humans: the Cyclophyllidea and the Pseudophyllidea. The former have a terrestrial life cycle and cystic larvae; the latter have an aquatic cycle and worm-like larvae.

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