Helminth infections roundworms

Albendazole, a benzimidazole derivative closely related to mebendazole (qv), is used in the treatment of helminth infections, such as gastrointestinal roundworms, hydatid disease, neurocysticercosis, larva migrans cutanea, and strongyloidiasis (1). Provided that an adequate concentration is attained within the cyst, it is scolicidal. In high doses given for prolonged periods or cyclically, it is... 

A variety of helminths belonging to the class nematoda (roundworms), trema-toda (flatworms or flukes) and cestoda (tapeworms) are known to infect humans and domestic animals. The diseases caused by these worms are not only responsible for occasional deaths and wide range of health problems in man, but also exert detrimental effect on the nutritional and immune status of the host resulting in low resistance against other infections. The presence of helminth infections in livestock leads to decrease in output of animal products (milk, fat, butter, meat, eggs, wool and leather etc.) and has, therefore, strong socio-economic impact in countries with agro-and dairy-based industries [7]. 

Nematode Infections - Nematode parasites cause medically and economically important diseases in man and his domestic animals throu out the world. Among the more than 25 different worms that affect man, the large roundworm, the hookworm and the whipworm are responsible for more than half of mankind s helminthiases. The n imber of hiiman helminthic Infections in the United States has been estimated at about 44 million. The majority of these infections is due to pinworms (enterobiasis). 

Human infections caused by worms (helminths) represent one of the most important public health problems in the wodd. Helminths form three main categories or phyla Platyhelminths, flatworms Aschelminthes, roundworms and Nemathelminthes, thomy-headed worms. Platyhelminths consist of Trematoda and Cestoda. Members of the class Trematoda, or flukes (schistosomes), are slender leaf-shaped organisms that possess attachment organs in the form of cupshaped hooks called suckers. Members of the class Cestoidea, or tapeworms, are flat and ribbonlike. These worms have serially repeated sections behind the neck and an attachment organ called the scolex. The Aschelminthes (class Nematoda) are roundworms, which have a basic cylindrical shape with major variations in proportions, size, and structure. The Nemathelminthes (Acanthocephala), or thomy-headed worms, are widely distributed among animals and generally do not involve a human host. 

Thiabendazole. This benzimidazole derivative (12) is an effective oral drug used in the treatment of intestinal roundworms and selected tissue parasites. Infections with S. stercorahs are commonly treated with thiabendazole for two days. Disseminated strongyloidiasis is treated for at least five days. Satisfactory results have been reported when used for T. spirahs infections however, its effectiveness on encapsulated muscle larvae has not been clinically demonstrated. Extensively used in veterinary medicine, thiabendazole was the first broad-spectrum benzimidazole anthelmintic. It is widely used in the United States. The mechanism of action is not clearly understood, but it has been shown that thiabendazole inhibits the enzyme fiima.ra.te reductase, which is found specifically in the mitochondria of helminths (31). 

Parasitic helminth (worm) infections are widespread and may be the most common disease in the world. Estimates by the WHO and others are that one type of schistosomiasis, the blood flukes, has 200 million people infected. Ascaris, a large roundworm, accounts for at least 650 million, hookworm 450 million, and the several filarial worm species add another 250 million victims to the total. The situation has improved little in the past decade. 

Table 7-9 is a condensed classification and nomenclature of the important parasitic helminths that affect humans. The worms that infect humans are the flatworms and the roundworms. Helminths are the only parasites discussed here that are not microscopic. Quite the opposite, their dimensions are of the order of millimeters and, in the case of certain tapeworms, reach lengths of meters. 

Helminths constitute a major health problem in humans and domestic animals, especially in the tropical and sub-tropical areas of the world. They are classified in two phyla the flatworms (Platyhelminthes), comprising the flukes (or trematodes) and the tapeworms (or cestode), and the roundworms or nematodes (Nemathelminthes). Most nematodes are not parasitic, but some infect vertebrates by entering the digestive tracts of animals where they develop into adults. Diseases caused by infection are dependent on the residence site of the adult nematode the gastrointestinal tract or body tissues. 

Infections with helminths, or parasitic worms, affect more than two bilhon people worldwide. Pathogenic worms are classified into roundworms (nematodes) and two types of flatworms, flukes (trematodes) and tapeworms (cestodes). Immature forms invade humans via the skin or gastrointestinal (GI) tract and mature into adult worms with characteristic tissue distributions. With few exceptions, such as Strongyloides and Echinococcus, they cannot complete their life cycle and replicate themselves within the human host. 

Helminth parasites infect a broad range of species, including man and it is estimated that a third of the global population is infected with parasitic worms. In this chapter, we focus solely on parasitic helminths, which have a medical significance to humans. These species include the Digenean flukes of the Class Trematoda (Flatworms) and the Class Cestoda (Tapeworms), both of the phylum Platyhelminthes and the phylum Nematoda (Roundworms). Some of the major species of helminths of medical importance to humans are outlined in Table 1, presented with an arbitrary ranking based on prevalence of worldwide infections. 

Trypanosoma cruzi infection. The current treatment involves noxious organic drugs, the dose being limited by the toxicity of the therapy. Helminth worms include flukes, tapeworm and roundworms, which cause a diverse range of infections all over the world. For example, the annual incidence of infection from threadworm exceeds 200 milhon cases, including high levels of infection in Europe, Canada and the US. 

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