Helminth infections tapeworms

Clinical Use. Paromomycin (Humatin) is an aminoglycoside antibacterial (see Chapter 33) that is used primarily to treat mild to moderate intestinal infections (amebiasis).51 This drug may also be used as an adjunct to other amebicides during the treatment of more severe protozoal infections. Paromomycin is also effective against some bacteria and tapeworms, and may be used as a secondary agent in certain bacterial or helminthic infections. This drug is administered orally. 

Infections with Taenia, a genus belonging to the family of tapeworms, is of no consequence for the human liver and bile ducts. In contrast, echinococcosis is a helminthic infection of major clinical significance. 

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]. 

The tapeworm infection is a widespread helminth disease which has attracted the attention of native practitioners and physicians. The first so called "effective" herbal preparation for eradicating tapeworms from humans became available in 1775 known as "Madame Nauffer s Tapeworm Cure" [1]. The active ingredient of this remedy was male fern. Since then the extract of the rhizome of male fern (Dryop-terisfilix mas), called aspidium oleoresin, has been used as a folk remedy and also as a drug in clinical medicine to treat tapeworm infections in humans. 

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. 

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. 

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. 

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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