Helminths infection prevalence

One likely reason for the prevalence of helminths is their undoubted ability to down-regulate the host immune system at both the antigen-specific and polyclonal levels [3], In many chronic diseases, such as schistosomiasis and lymphatic filariasis, peripheral blood T cells show dramatically impaired parasite antigen-specific responsiveness [4], as discussed in more detail below. Moreover, from early reports of immunosuppression in animal models of infection, to studies in Africa linking vaccine failure to heavy helminth infection, there is clear evidence that infections can diminish reactivity to bystander antigens, particularly with increasing intensity of... 

Table 1 Changes in prevalences of helminthic infections in patients treated with albendazole...

IHTESTIHAL HELMINTHIASES — The world-wide incidence of Intestinal helminthic infections in man approaches the staggering figure of two billion. The prevalence of these infections and their complex and far-reaching effects upon body function cause them to rank among the most Important disease problems of man. 

Human infections with Salmonella spp. and E. coli 0157 H7 are a common worldwide phenomenon. Livestock may serve as a source of several relevant human pathogenic microorganisms (Table 19.2). The most prevalent group is the enteric pathogens which include bacteria, viruses and parasites (i.e. protozoa and helminths). Animals may shed pathogens through excreta without... 

Infections with helminth parasites remain extraordinarily prevalent in many developing countries, with >25% of the human population currently infected. Helminth diseases are also... 

Parasitic helminths, such as Ascaris lumbricoides, Trichuris trichiura, hookworms, schistosomes and filarial nematodes are highly prevalent in tropical and subtropical areas of the world [1]. These infections often overlap and affect more than 1 billion... 

The major nematode parasites of humans include the soil-transmitted helminths (STHs) and the filarial nematodes. The STH infections, which include ascariasis, trichuriasis, and hookworm infection, are among the most prevalent infections in developing countries. Eradication programs use schools to administer broad-spectrum anthelmintics on a periodic and frequent basis. The most widely used agents for reducing morbidity are the benzimidazole anthelmintics (BZAs), either albendazole (albenza and zentel) or mebendazole (VEEtMOX) (see Table 41-1). 

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. 

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