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PubMed2001

Adhesive secretions in the Platyhelminthes.

This review is the first to draw together knowledge about bioadhesives secreted by a group of parasites. Mechanisms of mechanical attachment are well known among parasites, but some can also attach to host surfaces by chemical means using a thin layer of adhesive material secreted at the parasite-host interface. Attachment by adhesives to living surfaces has not been studied in detail previously. A significant volume of research has determined much about the chemistry and nature of bioadhesives secreted by various marine macroinvertebrates from different phyla for attachment to inert substrates. Mussels and barnacles are sessile and adhere permanently, whereas starfish display temporary but firm adhesion during locomotion, feeding and burrowing. We focus on the Platyhelminthes that comprises the largely free-living Turbellaria and the wholly parasitic Monogenea, Cestoda, Digenea and Aspidogastrea. The term tissue adhesion is introduced to describe attachment by adhesives to epithelial surfaces such as fish epidermis and the lining of the vertebrate gut. These living layers regenerate rapidly, secrete mucus, are a site for immune activity and are therefore especially hostile environments for organisms that inhabit them, presenting a significant challenge for adhesion. Not all platyhelminths adhere to living surfaces and types of adhesion to inert substrates by the free-living turbellarians are also reviewed. Tissue adhesion is particularly well exemplified by monopisthocotylean monogeneans, parasites that are especially mobile as larvae, juveniles and adults on the epidermis of the body and gill surfaces of fish. These monogeneans secrete adhesives from the anterior end when they move from site to site, but some have secondarily developed adhesives at the posterior end to supplement or replace mechanical attachment by hooks and/or by suction. The temporary but tenacious anterior adhesives of monogeneans display remarkable properties of instant attachment to and detachment from their host fish surfaces. In contrast to the mobility of turbellarians and monopisthocotylean monogeneans and the simplicity of their direct life cycles, the largely endoparasitic Cestoda and Digenea are considered to be less mobile as adults. The complex cestode and digenean life cycles, involving intermediate hosts, place different demands on their various stages. Diverse, mostly anterior, gland cells in larvae, metacestodes and adults of the true tapeworms (Eucestoda), and in larval and adult Gyrocotylidea and Amphilinidea are reviewed. Conspicuous gland cells, mostly but not exclusively at the anterior end, in miracidia, cercariae and adults of digeneans and in cotylocidia and adults of aspidogastreans are also reviewed. Unlike turbellarians and monogeneans, accounts of unequivocal adhesive secretions in the Cestoda, but especially in the Digenea and Aspidogastrea, are relatively rare. The primary purpose of many conspicuous glands in the different stages of these mostly endoparasitic flatworms is for penetration into, or escape from, different hosts in their life cycle. We provide a detailed review of current knowledge about adhesion (in the sense of a thin layer of chemical material) in the Platyhelminthes including uses among eggs, larval, juvenile and adult stages. Information on structure, morphology and ultrastructure of the various adhesive systems that have been described is reviewed. Application of the 'duo gland' model is discussed. Comparisons are made between the little that is known about the chemistry of flatworm adhesives and the significant knowledge of the chemical nature of other invertebrate bioadhesives, especially those from marine macroinvertebrates. The potential importance of adhesives in parasitism is discussed. (ABSTRACT TRUNCATED)

Animals↗
PubMed1992

Growth, development and allometry of Philophthalmus nocturnus in the eyes of domestic chicks.

Fifty day-old chicks were each infected with 10 excysted metacercariae of Philophthalmus nocturnus Looss, 1907 around each orbit and growth, development and allometry were studied. The growth rate showed two phases over a period of 35 days, a limited lag phase lasting two days post-infection in which flukes did not exceed 440 microns in length, and a rapid phase during which growth was rapid and flukes reached a size of 3.008-3.504 mm on day 35. Five developmental stages were noticed during the course of development of the metacercaria to the egg-producing adult stage. Eggs appeared in the uterus on day 14 and oculate miracidia on day 25. The hindbody, testes and ovary showed positive allometric growth, the pharnyx less so, whereas negative allometric growth was shown by the forebody. Body width, oral sucker and ventral sucker were close to isometry, growing at the same rate as the body length.

Animals↗
PubMed1996

The distribution of common intestinal nematodes along an altitudinal transect in KwaZulu-Natal, South Africa.

In order to study the effect of climate and topography on the distribution of common, intestinal nematodes in schoolchildren, changes in prevalence were investigated along an altitudinal transect from approximately 50 m above sea level (asl), near the coast, to approximately 1700 m asl, in the foothills of the Drakensberg Mountains, KwaZulu-Natal, South Africa. These changes were related to several permutations of temperature, rainfall and evaporation, using univariate and multiple regression analyses. A total of 693 primary schoolchildren aged between 7 and 15 years was examined from six communities along the 150-km transect. Changes in the prevalence of Trichuris trichiura were significantly correlated with temperature-derived variables whereas those of Ascaris lumbricoides and Necator americanus were correlated with rainfall-derived variables. A total of 17 parasite species was recovered along the transect but polyparasitism was negatively correlated with altitude.

Adolescent↗
PubMed2000

Helminth parasites of the western painted turtle, Chrysemys picta belli (Gray), including Neopolystoma elizabethae n. sp. (Monogenea: Polystomatidae), a parasite of the conjunctival sac.

Neopolystoma elizabethae n. sp. is described from the conjunctival sac of the western painted turtle Chrysemys picta belli (Gray), from the Upper Peninsula of Michigan. This is the first species found in this location from chelonians in North America. The new species differs from all other species of Neopolystoma in possessing a circle of 8 genital spines that are recurved and possess a crescent-shaped base. Eight additional species of helminths were found in the 5 turtles examined in this study. All are common parasites of North American freshwater turtles. An additional species of Monogenea (Polystomoidespauli) was found in the oral cavity. Four species of Digenea (Eustomos chelydrae, Allassostomoides chelydrae, Spirorchis kirki, and Spirorchis parvus) and 3 species of Nematoda (Spiroxys contorta, Serpinema trispinosus, and Amphibiocapillaria serpentina) were also found. The following are reported from Michigan for the first time: P. pauli, S. kirki, and A. serpentina.

Animals↗
PubMed1977

Anthelmintics.

This article describes the drugs used in helminthic infections and their therapeutic indications, mode of action, toxicity and other details of each of the recommended drugs, and discusses the nature and treatment of infection by helminths important in human medicine. Infestation due to the roundworms Enterobius vermicularis, Ascaris lumbricoides and the hookworms, Ancylostoma duodenale and Necator americanus can all be treated effectively with pyrantel pamoate. For Enterobius vermicularis, however, a newer drug, mebendazole, is equally as effective. The advantage of these drugs in the indicated circumstances is that they can be administered in a single dose. Unfortunately, pyrantel pamoate is not a panacea and in the case of Necator it is not as effective as in the other roundworms. In that situation the use of tetrachlorethylene is preferable. For treatment of Strongyloides stercoralis, and important human parasite, because it can become disseminated and lead to fatal infections in immunoincompetent hosts, the only effective drug is thiabendazole. In treatment of Trichuris trichiura infection, mebendazole, administered over a period of 3 days, is the most effective available drug. For the roundworms inhabiting tissues--either as aberrant infections of man or as the normal part of their life cycle in man--therapy tends to be largely non-specific. For example, in visceral larva migrans, caused by the dog roundworm Toxocara canis, only palliative therapy with systemic anti-inflammatory agents and corticosteroids may be helpful. Cutaneous larva migrans, caused by the dog hookworms Ancylostoma brasiliensis and Ancylostoma caninum, is also treated primarily with symptomatic measures, but there is a suggestion that thiabendazole may kill the larvae and thus be effective. Trichinella spiralis may cause severe, even fatal infections in man, but only symptomatic therapy can be offered. Therapy for filarial infections is regrettably complicated and not completely effective. Diethylcarbamazine remains the best available drug, but in some of these infections local surgical excision may also be used. It is important to bear in mind that release of antigens from dying or dead worms may cause systemic inflammatory and allergic reactions that may require therapy with corticosteroids. Therapy for Cestodes is achieved most effectively with niclosamide, but the antimicrobial agent paromomycin has also been effective. For the aberrant cestode infections of man, such as echinococcal cysts or Taenia solium cycticerci, treatment is surgical if the affected areas are accessible. Treatment of schistosomal infections is quite toxic and, therefore, it is mandatory to determine viability of the worms before recommending therapy. If therapy is required, then Schistosoma mansoni infections are treated with stibophen and S. japonicum with antimony potassium tartrate, taking care in both of these instances to watch for the early signs of antimony toxicity; therapy of S. haematobium infections is based on administration of niridazole...

Anthelmintics↗
PubMed1999

Helminths of white-bellied opossum from Brazil.

Helminths were collected from 22 specimens of the white-bellied opossum (Didelphis albiventris) captured in the region of Pampulha (Belo Horizonte, Brazil), from May 1985 to March 1995. Ten species of helminths were collected; these included Rhopalias coronatus, Brachylaema migrans, Aspidodera raillieti, Cruzia tentaculata, Turgida turgida, Gongylonema sp., Viannaia hamata, Travassostrongylus orloffi, Trichuris didelphis and Capillaria sp.

Animals↗