Nematode worm

Antinematodal. An anthelmintic effective against round worms (nematodes). 

Worms are known as helminths and the majority is not parasitic. Classes of worms that parasitize man are round worms (nematodes) and flat worms (platyhelminths). The flat worms are divided into tapeworms (cestodes) and flukes (trematodes). Only a few human parasitic worms are common in the United Kingdom, for example threadworms and round worms. In tropical and subtropical parts of the world, where abundant water and high temperatures provide an optimal environment for the larvae and intermediate hosts, parasitic worms are common and widespread. Table 9.8 lists some parasitic worms that can infect man, their effect and drugs used to treat them. 

Column 6 Homologs listed for h = human, m = mouse, w = worm (nematode) together with BLASTp e-scores. 

Many parasitic worms cause systemic infections outside the gastrointestinal tract. These include Strong loides stercoralis (threadworm), Trichinella spiralis Dracunculus medinensis and the several species of nematodes that cause filariasis (Mansonellaperstans and Onchocerca volvulus). 

Ivermectin has an extremely broad spectmm of antinematodal activity in a variety of domestic animals. Indeed, among the many nematodes against which it has been tested, none has been found that is not affected by ivermectin during at least one stage of the life cycle. In all but a few instances the dmg is highly active against both immature and mature worms (19). 

Caenorhabditis elegans (simple animal nematode worm) 100 (1998 )... 

Imidacloprid is a widely used neonicotinoid insecticide that kills pests by targeting their central nAChRs. Levamisol is used to kill nematodes by acting on nAChRs in the worm s muscles. 

Marine Worms. (Platyhelminthes, Rynchocoela, Annelida, Sipunaelida.) A variety of species from worm phylla have been found to contain toxins. There are approximately 56,000 species of worms (14,000 annelids, 25,000 platyhelminthes, 15,000 nematodes, and 800 nemertines), and of these, most of the toxic species are found in the nemertines. The most well-known toxin is nereisotoxin which has been modified to form a very useful insecticide. 

Within the body of filarial nematodes, intracellular bacteria have been observed by electron microscopy in the lateral cords of both males and females. Within the cell cytoplasm, the bacteria are in membrane-bound vacuoles. In some cases, the cytoplasm of lateral cord cells is filled by bacteria these bacteria-filled cells resemble in some ways insect bacteriocytes (Baumann et al, 1998). In female worms, bacteria are present also in the oogonia, oocytes, developing embryos and in the cell layer surrounding... 

M. B., Tanya, V.N., Donnely, M.J. and Trees, A.J. (2000) Macrofilaricidal activity of tetracycline against the filarial nematode Onchocerca ochengi elimination of Wolbachia precedes worm death and suggests a dependent relationship. Proceedings of the Royal Society of London B 267, 1063-1069. 

Investigating phenotypic diversity is not easy. A basic requirement is to have different lines of parasite available and in natural host species. However, being aware of the possibility of variation between individual worms would be a start. The few studies that have molecularly considered individual worms (Bianco et al., 1990 Fraser and Kennedy, 1990 Currie et al., 1998) have found variation between individual worms. Such variation may be the basis of some experimental noise . Perhaps efforts should be focused on this noise The phenotypic diversity that exists in natural, and even laboratory, populations of nematodes is maintained there by natural selection. This tells us, anthropomorphically, that such diversity matters to parasitic nematodes. It is hoped that this chapter has shown that it should also matter to us. 

Parasitism by T. spiralis has been a subject of scientific interest for over 150 years. Recently, considerable attention has been paid to the parasite by immunologists interested in immunity to nematodes in general, and mucosal immunity in particular. It has been shown that glycan-specific antibodies are highly effective mediators of host defence against intestinal 7. spiralis infection. Protective monoclonal antibodies have been used to elucidate mechanisms of worm expulsion, as well as to identify molecules that the parasite uses to create its niche. In the future, detailed characterization of these molecules and their functions should afford additional insights into parasitism by Trichinella spiralis, and possibly also by other types of pathogen. 

Vaccination of lambs with a contortin-enriched preparation gave a mean reduction in worm burdens of 78% (Table 13.1) (Munn et al., 1987). This result was particularly significant because it showed that proteins expressed on the surface of the gut, albeit from a blood-feeding nematode, could induce high levels of protective immunity when used as an immunogen. These proteins are not normally accessible to the host immune system during the course of infection they are termed hidden or concealed antigens and the immunity conferred by them is described as artificial immunity. 

Contortin-like material was also observed in Teladorsagia circumcincta, another stomach worm of ruminants, while material separating the microvilli of the rodent nematodes N. brasiliensis and Syphada obvelata was... 

A cardinal role for IL-4 in host protection against intestinal nematode infection was first shown in the H. polygyrus challenge model. Worm expulsion was delayed following treatment with anti-IL-4 or anti-IL-4 receptor monoclonal antibodies, while control treated animals successfully cleared infection (Urban et al., 1991b). Blockade of the IL-4 receptor effectively prevents the in vivo function of IL-4 and IL-13, as these two cytokines share the IL-4 receptor a-chain for signalling functions (Lin et al, 1995). In... 

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