Evolution of Schistosoma Mansoni and Its Snail Hosts - Eric Loker
It is hoped that vaccines and better diagnosis of human will help alleviate . The results show a direct relationship between temperature and infection rate, i.e., Snail hosts for schistosomes showed a regular pattern of activity in relation to the . Moreover an important key to understanding schistosome evolution is to comprehend relationships among S. mansoni populations, and among their snail hosts. Budget Start: ; Budget End: ; Support Year: 2; Fiscal. Marsh Flies, Snails, and Blood Flukes: Biology of the Ecologically Connected . The value of such non-adaptive characters in determining relationships of.
Blood fluke eggs were found in Egyptian mummies from BC, and hematria was commonly found among soldiers reported by surgeons in Napoleon's army in Egypt — Schistosomes do not require a second intermediate host in their life cycles but mature in the blood vascular system of subject hosts, namely fishes, turtles, birds, and mammals, including humans.
Here, the life of sciomyzid flies is linked to snails, as these fly larvae must feed on snail tissue Roberts and Janovy, The chapters are organized by important subject areas of biological and ecological factors related to the linkage between sciomyzid flies and mollusks, focused on all aspects of morphological, ecological, and behavioral characteristics of larval development in their hosts.
This chapter is followed by a section describing the unique panorama of the marsh flies-schistosomes-human ecosystem that includes the natural enemies of snails and slugs, the malacophagy of Diptera, and their life cycle.
In Chapters 5 through 8, the subject on the feeding behavior and competition of sciomyzid flies are presented in detail followed by Chapter 9 that is concerned with phenology, reproduction, and development of marsh flies.
Chapters 10 through 13 then present the core ecological resources related to population dynamics pp. A large portion of the book Chapters 14—17, pp. Beginning with a comprehensive character analysis pertaining to morphology, physiology, and behavior related to adults, larvae, and eggs, the useful taxonomic keys adults and puparia are presented for the genera of different geographic regions, followed by a comprehensive treatment of the higher classification of marsh flies pp.
Strategic Control of Schistosome Intermediate Host - SciAlert Responsive Version
In the concluding remarks, the authors discuss the issues of character selection Section It may be important to visit the statement pertaining to taxonomic characters that states: The value of such non-adaptive characters in determining relationships of species and genera of Sciomyzidae might be questionable.
In addition, the problem becomes even more complicated for arthropods, specifically most of the insects and diverse mites Acarina with complicated life cycles, such as many aquatic insects e. Irrespective of which cladistic technique is used for phylogeny, critical character analysis based on all acceptable characters is required for the most parsimony and the commonly acceptable classification. As shown in this book, all biological characters should be considered for character evolution including morphological and ecological ones.
It is natural to come up with two different phylogenetic trees and thus classifications of a specific taxon if the analysis was based exclusively on adults, larvae, eggs, or even on the composition of all stages. The enzymes also cause an eosinophilic inflammatory reaction when eggs get trapped in tissues or embolize to the liver, spleen, lungsor brain.
Cerebral granulomatous disease may be caused by S. Communities in China affected by S. For example, in S. Once this step has been completed, the parasite leaves the snail and enters the water column.
The parasite can live in the water for only 48 hours without a human host. Once a host has been found, the worm enters its blood vessels. For several weeks, the worm remains in the vessels, continuing its development into its adult phase. When maturity is reached, mating occurs and eggs are produced. If the eggs do not get excreted, they can become engrained in the body tissues and cause a variety of problems such as immune reactions and organ damage.
Humans encounter larvae of the Schistosoma parasite when they enter contaminated water while bathing, playing, swimming, washing, fishing, or walking through the water.
Young worms then pair and migrate to their predilection sites in the veins of the gut or bladder. Egg production begins from weeks after infection, and adult worms normally live for years, although some may survive much longer.
The eggs are sufficiently characteristic to facilitate specific diagnosis. On occasion, microscopy of rectal biopsies has been used to diagnose S.
Immunoserological tests have been developed to detect host antibodies against infection but they have experienced cross-reactivity problems and cannot discriminate between previous and active infection.
More recently, molecular techniques have been used to detect parasite antigens or DNA in host samples; some tests showing good correlations with parasite burdens. The drug of choice for the treatment of all Schistosoma spp. Nitridazole and metrifonate are effective against S.
- Marsh Flies, Snails, and Blood Flukes: Biology of the Ecologically Connected
While timely treatment is effective, cured individuals rapidly become re-infected in endemic areas. Various control programmes have therefore been developed based on mass chemotherapy in conjunction with preventive measures, including improved sanitation, snail vector control, modifying habitats and farming practices, and public education campaigns.
Water contamination can be reduced by preventing the ingress of parasite eggs as well as curtailing the asexual amplification cycle in snail hosts. The provision and use of latrines contains sources of infection, and modern biocomposting toilets appear to be effective in killing parasite eggs when used properly. Snail populations may be reduced by the strategic use of molluscicides niclosamide or copper sulphatedraining marshes and swamps, and clearing channels of vegetation.