Helminthic infestations

Because of the importance of malaria, antiparasitic drugs are sometimes divided into two classes antiparasitic agents for protozoans, especially malaria, and antiparasitic agents for helminthic infestations. Each of these classes will be examined separately. 

Ivermectin (9.119), a semisynthetic macrocyclic lactone, is the dmg of choice for strongyloidiasis and onchocerciasis types of helminth infestation. Ivermectin appears to paralyze the nematode, which may lead to its death but which certainly facilitates its expulsion from the body. 

Ectoparasites such as ticks, mites and haematophagous flies together with certain endoparasites may be "managed" by use of avermectins (macrocyclic lactones) or hormone analogues and by Immunization of the hosts with antigens derived from the vectors or parasites themselves. Recently this combined approach has been used most effectively against helminth infestations as well as against ticks and flies. Use of components of host odors and pheromones to trap, sterilize or kill tsetse flies is described as well as inexpensive methods of crop and livestock protection, such as oils and plant extracts, used traditionally in less developed countries. 

Helminthic infestations cause considerable morbidity.The drugs that are effective against these organisms are summarised. 

Anthelmintics are drugs that have the capability of riddin the body of parasitic worms or helminths. The prevalence of human helminthic infestations is widespread throughout the globe and represents a major world health problem, particularly in Third World countries. Helminths parasitic to humans and other animals are derived from two phyla. Plaly-helminthcs and Nemalhelminthes. Cestodcs (lapewomut... 

The mucosal inflammatory responses which accompany asthma, allergic inflammation and helminthic infestations are characterized by a marked and specific infiltration of eosinophils into the relevant mucosal surfeces. Of the cytokines secreted by activated T lymphocytes, IL-3, IL-5 and GM-CSF promote maturation, activation and prolonged survival of the eosinophil (Lopez etal., 1986 Rothenberg et al., 1988, 1989). 11 5 is unique in that, unlike IL-3 and GM-CSF, it acts specifically on... 

A number of nitrophenyl and nitroheteroaryl drugs have been found to be effective in treating helminth infestations in humans and domestic animals [57,58]. 

The iron deficiency and helminth infestation are two of the most common conditions afflicting children in iess industriaiized countries. Hookworm species being transmitted in a community influence the burden of iron deficiency anemia and should be considered when prioritizing and planning programs for hookworm and anemia control. 

It thus appears that for some helminths infesting some animal hosts there are limiting factors in the host s diet which control the establishment and development of the parasite. This seems to apply to carbohydrate for rat tapeworms and to calcium and phosphorus for chick round-worms. Some factor or factors in the B complex vitamins may limit the development of rat tapeworms also. 

Pyrantel is a dmg of first choice for the treatment of a number of round-, thread- and hookworm infestations. However, it has no activity against whipworm. Its mechanism of action is based on triggering the release of acetylcholine in helminths causing a depolarizing neuromuscular blockade that leads to spastic paralysis. 

Anthelmintic agents are used to eradicate (either kill or expel) the infesting helminths. 

This group of compounds has played an important role in the control of worm infestations of cattle, sheep and horses, with particular activity against the larval stages of worms. Prior to their introduction there was no effective treatment of larval stages of worms. The benzimidazoles are also active against tapeworms and fluke. The main compounds in use are thiabendazole, cambendazole, fenbendazole, oxfendazole, mebendazole and albendazole. The mode of action of these compounds is through their effect on the uptake of nutrients by the helminth, which results in a reduction in glycogen and subsequent starvation. 

Guryanova, S.D. (1980). Lipid composition of some tissues of turbot infested by helminths (In Russian). In Biochemistry of Freshwater Fish of Karelia (V.S. Sidorov, ed.), pp. 36-40. Karelian Branch of the Academy of Sciences of the USSR, Petrozavodsk. 

Mention should be made at this point that the avermectins have been used primarily to clear livestock of those infesting endopara-sltes (18) that utilize GABA as a transmitter between nerve cells. World-wide losses of production in livestock infested with helminths cannot be overemphasized. 

This chapter discusses the major parasitic diseases, including protozoan diseases (amebiasis, malaria), helminthic infections (as-cariasis, enterobiasis), and ectoparasitic infestations (head and body lice). Emphasis is placed on diseases seen more frequently in the... 

It is difficult to title correctly a discussion that attempts to deal with the broad area of drugs utilized to treat all the types of infections that parasitize humanity. Antiparasitic might be technically more correct because it would include all organisms from the microscopic in size to the 75-foot tapeworm, but the term parasite has acquired a much narrower meaning as commonly used. The title antimicrobial was selected even though drugs controlling helminthic (worm) infestations will be considered. Similarly, antiviral compounds will also be discussed, even if viruses are not microbes as commonly viewed. 

The host immune response to helminths is partially controlled by cytokines as immune cell signalii molecules, and chemokines to induce cell-specific chemotaxis, in order to ehcit the appropriate antihelminthic response. Prolonged co-existence of helminths and their hosts have resulted in parasite developing homologues to human cytokines and chemokines that manipulates the host immune response in such a way as to prolong parasite infestation. Examples of helminth cytokine and chemokine homologues are shown in Table 6 and described herein. 

Oesophagostomiasis is infestation with Oesopha-gostomum bifurcum, a human parasitic intestinal helminth. It is endemic in parts of West Africa (Polderman et al. 1991 Polderman et al. 1999). Oesophagostomum bifurcum juveniles develop in the colonic wall causing pus-filled granulomas (Storey... 

In this chapter the term infection" is limited to infestations by protozoal and helminthic parasites. The Editors. 

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