The Parasitological and Pathological Significance of Arrested Development in Nematodes

1953 ◽  
Vol 27 (3-4) ◽  
pp. 199-205 ◽  
Author(s):  
E. L. Taylor ◽  
J. F. Michel
Keyword(s):  
Intermediate Host ◽  
Larval Stage ◽  
Final Host ◽  
Parasitic Nematodes ◽  
Intermediate Hosts ◽  
Suitable Host ◽  
Free Living ◽  
Arrested Development ◽  
Essential Requirement

In summarising, therefore, we conclude that a tendency to become dormant during the larval stage, which is so characteristic a feature of the free-living larvae of parasitic nematodes and is an essential requirement in their use of intermediate hosts is not an uncommon occurrence during their life in the final host. Its purpose in each instance is essentially the same, i.e. to carry it through a period in which the environment is unsuited to development; on the ground, for instance, where it waits for a suitable host, as a parasite of an intermediate host, where it waits for a suitable final host, or in a resistant final host where inhibited development serves the parasite in enabling it to wait until some depression of the host's state of resistance allows it to grow to maturity.

The significance of precocity in the transmission of the nematode parasites of vertebrates

1993 ◽  
Vol 71 (10) ◽  
pp. 1917-1922 ◽  
Author(s):  
R. C. Anderson ◽  
Cheryl M. Bartlett
Keyword(s):  
Intermediate Host ◽  
Definitive Host ◽  
Egg Production ◽  
Infective Larva ◽  
Parasitic Nematodes ◽  
Fourth Stage ◽  
Intermediate Hosts ◽  
Nematode Parasites ◽  
Large Size ◽  
Advanced Development

The significance of precocity in the transmission of heteroxenous parasitic nematodes is reviewed. Precocity of nematodes in intermediate hosts manifests itself in the following ways depending on the species: (i) the unusually large size of the infective larva; (ii) the advanced development of the genital primordium in the infective larva; (iii) development to the fourth stage in the intermediate host; and (iv) development to the subadult stage (early fifth stage) in the intermediate host. Precocity apparently accelerates gamete and egg production in the definitive host when the behaviour of intermediate and definitive hosts restricts transmission to confined limits of space and time. Examples of precocity are outlined and, whenever possible, related to the behaviour of definitive and intermediate hosts during transmission.

Sex determination and sex differentiation in coccidia: gametogony and oocyst production after monoclonal infection of cats with free-living and intermediate host stages of Isospora (Toxoplasma) gondii

Parasitology ◽  
1985 ◽  
Vol 90 (1) ◽  
pp. 35-44 ◽  
Author(s):  
A. W. C. A. Cornelissen ◽  
J. P. Overdulve
Keyword(s):  
Gene Expression ◽  
Toxoplasma Gondii ◽  
Antibody Response ◽  
Intermediate Host ◽  
Sex Chromosomes ◽  
Sex Differentiation ◽  
Final Host ◽  
Patent Period ◽  
Free Living ◽  
Differential Gene

Clones of single oocysts, single sporocysts, single sporozoites, single proliferative parasites, single cysts and single cystozoites of Isospora (Toxoplasma) gondii (KB-strain) were made under visual control using a de Fonbrune micromanipulator. Cloning was successful in 28, 32, 21, 8, 54 and 7% of the trials, respectively. All clones were used for monoclonal infection in non-immune conventionally reared (CV) or specified pathogen-free (SPF) cats. Pre-patent and patent periods, sporulation percentages of excreted oocysts, mouse infectivity of sporulated oocysts, antibody response and immunity to reinfection of CV cats were determined. For these parameters almost no differences were observed between monoclonal infections and infections described with the non-cloned KB-strain. In all cats autopsied during the patent period, 5–8 days post-infection, macrogametes, microgametes and oocysts were found. Since meiosis occurs during sporulation and since all free-living and intermediate host stages proved to be bisexual, it is concluded that sex differentiation in I. (T) gondii is not determined by segregation of sex chromosomes or sex genes but is caused by some final host factor(s) that induce(s) differential gene expression in genetically identical cells.

scholarly journals Parasite-induced colour alteration of intermediate hosts increases ingestion by suitable final host species

Behaviour ◽  
2019 ◽  
Vol 156 (13-14) ◽  
pp. 1329-1348
Author(s):  
Timo Thünken ◽  
Sebastian A. Baldauf ◽  
Nicole Bersau ◽  
Joachim G. Frommen ◽  
Theo C.M. Bakker
Keyword(s):  
Intermediate Host ◽  
Host Species ◽  
Final Host ◽  
Life Cycles ◽  
Intermediate Hosts ◽  
Dead End ◽  
Body Colouration ◽  
Species Specific ◽  
Acanthocephalan Parasite ◽  
Parasitic Manipulation

Abstract Parasites with complex life cycles often alter the phenotypic appearance of their intermediate hosts in order to facilitate ingestion by the final host. However, such manipulation can be costly as it might increase ingestion by less suitable or dead-end hosts as well. Species-specific parasitic manipulation is a way to enhance the transmission to suitable final hosts. Here, we experimentally show that the altered body colouration of the intermediate host Gammarus pulex caused by its acanthocephalan parasite Pomphorhynchus laevis differently affects predation by different fish species (barbel, perch, ruffe, brown trout and two populations of three-spined stickleback) depending on their suitability to act as final host. Species that were responsive to colour manipulation in a predation experiment were more susceptible to infection with P. laevis than unresponsive species. Furthermore, three-spined stickleback from different populations responded to parasite manipulation in opposite directions. Such increased ingestion of the intermediate host by preferred and suitable hosts suggests fine-tuned adaptive parasitic manipulation and sheds light on the ongoing evolutionary arms race between hosts and manipulative parasites.

scholarly journals Winning the arms race: host–parasite shared evolutionary history reduces infection risks in fish final hosts

2018 ◽  
Vol 14 (7) ◽  
pp. 20180363 ◽  
Author(s):  
Danny J. Sheath ◽  
Jaimie T. A. Dick ◽  
James W. E. Dickey ◽  
Zhiqiang Guo ◽  
Demetra Andreou ◽  
...  
Keyword(s):  
Intermediate Host ◽  
Final Host ◽  
Arms Race ◽  
Response Analysis ◽  
Intermediate Hosts ◽  
Counter Selection ◽  
Fish Hosts ◽  
Host Parasite ◽  
Acanthocephalan Parasite ◽  
Infected Prey

Parasite manipulation of intermediate hosts evolves to increase parasite trophic transmission to final hosts, yet counter selection should act on the final host to reduce infection risk and costs. However, determining who wins this arms race and to what extent is challenging. Here, for the first time, comparative functional response analysis quantified final host consumption patterns with respect to intermediate host parasite status. Experiments used two evolutionarily experienced fish hosts and two naive hosts, and their amphipod intermediate hosts of the acanthocephalan parasite Pomphorhynchus tereticollis . The two experienced fish consumed significantly fewer infected than non-infected prey, with lower attack rates and higher handling times towards the former. Conversely, the two naive fish consumed similar numbers of infected and non-infected prey at most densities, with similar attack rates and handling times towards both. Thus, evolutionarily experienced final hosts can reduce their infection risks and costs via reduced intermediate host consumption, with this not apparent in naive hosts.

Ultrastructure of Cercarial Tails

1974 ◽  
Vol 32 ◽  
pp. 180-181
Author(s):  
Richard S. Demaree ◽  
Donald M. Wootton
Keyword(s):  
Schistosoma Japonicum ◽  
Intermediate Hosts ◽  
Suitable Host ◽  
Ultrastructural Studies ◽  
Tail Structure

Cercariae (juvenile trematodes with tails) emerge from mollusk intermediate hosts and swim toward definitive hosts or encystment objects. The locomotor power is furnished by the tail. Upon reaching a suitable host or encystment object, the tail is cast off and the cercariae penetrate and/or encyst. Ultrastructural studies of cercariae are sparse. There is even lessUltrastructural studies of cercariae are sparse. There is even less information about the tail structure; and body-to-tail morphology has been documented only for Acanthatrium oregonense and Schistosoma japonicum.

scholarly journals Domestication of wild animals may provide a springboard for rapid variation of coronavirus

2021 ◽  
Vol 16 (1) ◽  
pp. 252-254
Author(s):  
Lei Gao
Keyword(s):  
Intermediate Host ◽  
Wild Animals ◽  
Intermediate Hosts ◽  
Natural Conditions ◽  
Rapid Variation ◽  
Cross Breeding ◽  
Important Direction ◽  
Animal Hosts

Abstract Coronaviruses have spread widely among humans and other animals, but not all coronaviruses carried by specific animals can directly infect other kinds of animals. Viruses from most animal hosts need an intermediate host before they can spread widely among humans. Under natural conditions, coronaviruses do not rapidly change from infecting wild animals as intermediate hosts and to spreading widely among humans. The intermediate host might be the animals captured or bred for the purpose of cross-breeding with domesticated species for improvement of the breed. These animals differ from wild animals at the environmental and genetic levels. It is an important direction to study the semi-wild animals domesticated by humans in search for intermediate hosts of viruses widely spread among humans.

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.

scholarly journals First Case of Human Cerebral Taenia martis Cysticercosis

2015 ◽  
Vol 53 (8) ◽  
pp. 2756-2759 ◽  
Author(s):  
Julie Brunet ◽  
Aurélien Benoilid ◽  
Stéphane Kremer ◽  
Constanza Dalvit ◽  
Nicolas Lefebvre ◽  
...  
Keyword(s):  
Larval Stage ◽  
Immunocompetent Patient ◽  
Intermediate Hosts ◽  
Biopsy Material ◽  
Content Type ◽  
Dna Analyses ◽  
First Case

Taenia martis is a tapeworm affecting mustelids, with rodents serving as intermediate hosts. The larval stage (cysticercus) has been found before only rarely in humans or primates. We hereby describe a case of cerebral T. martis cysticercosis in a French immunocompetent patient, confirmed by DNA analyses of biopsy material.

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