Ascaris lumbricoides
Eric S. Loker, Bruce V. Hofkin in Parasitology, 2015
Ascaris lumbricoides, the large human intestinal roundworm (Figure 1), resides in the small intestine and is the causative agent of ascariasis. Males are 15–31 cm and females 20–49 cm long. Distribution and prevalence A. lumbricoides is one of the most common of all parasites, infecting 0.8–1.2 billion people, or about one sixth of humanity. It is prevalent in tropical and subtropical locations with poor sanitation and hygiene, including sub-Saharan Africa, the Americas, China, and East Asia. It is grouped with Trichuris trichiura and the hookworms as a soil-transmitted helminth. Hosts and transmission Humans, especially children, are the usual host for A. lumbricoides. Pigs can rarely be infected, just as humans are occasionally infected with the closely related roundworm of pigs, A. suum. The two species are close relatives but gene flow is limited between them. Infection is acquired by ingestion of soil, food, or water contaminated with feces containing Ascaris eggs (Figure 2). An L3 larva covered by the L2 cuticle emerges from the egg in the small intestine, penetrates the gut, and moves to the liver where the L2 cuticle is lost. The L3 moves to the lungs, is coughed up and swallowed and molts to L4 and then adulthood in the small intestine.
An Overview of Helminthiasis
Venkatesan Jayaprakash, Daniele Castagnolo, Yusuf Özkay in Medicinal Chemistry of Neglected and Tropical Diseases, 2019
The disease has been seen in people aged 10 years and older. Filarial worms cause a variety of clinical pathologies depending on the degree of host immune reaction. The subcutaneous filariasis causes skin itching, scratch marks and papules until the entire skin is dry and tempered. Filariases that affect the skin are caused by Wuchereria bancrofti, Brugia malayi, Loa loa, and Onchocerca volvulus (Kalungi et al. 2017). Dracunculus medinensis is a nematode that causes drancunculosis, a parasitic dermatosis that has affected humans for centuries. Dracunculus medinensis known as “Guinea worm” has been reported in 17 African countries including Yemen, Saudi Arabia, India and Pakistan. The disease remains asymptomatic till completion of puberty and fertilisation of female larvea during incubation period. Systemic infections may cause cutaneous manifestations as well as diarrhea, nausea, dyspnea, syncope and vomiting. The diagnosis of drancunculosis can be favored by worm extrusion from a skin lesion or wet smears showing motile larvae on microscopy (Linquist and Cross 2017, Assimwe and Hengge 2017). Ascaris is a genus of parasitic nematode worms known as the “small intestinal roundworms” and it is usually prevalent in tropical regions and expected to infect 1/4 of the world’s population. Most patients who are infected with Ascaris lumbricoides are asymptomatic. When the number of worms increases, abdominal pain and intestinal obstruction may occur. Pulmonary symptoms, including cough, shortness of breath, and haemoptysis may occur and eosinophilic pneumonia may develop due to larval migration to lungs. These round worms live in the lumen of the small intestine for 2 years and release a large number of eggs with faeces. The eggs bear rhabditiform larvae that hatch in the intestine. The resulting larvae are released, burrow through the intestinal wall and enter the hepatic circulation via capillaries and lymphatics. The larvae migrate via the right side of the heart into the lungs and then up the bronchial tree, where they are swallowed and make their way to the duodenum where they mature into adults after several months. (Kim et al. 2010, Linquist and Cross 2017). Trichinellosis is a parasitic disease caused by Trichinella spiralis, a nematode typically recognized as the “pork worm”. The parasitic cycle has two stages recognized as intestinal (or enteral) phase and systemic or parenteral phase. This cycle covers a period of several days to weeks.
History of public health in Pacific Island countries
Milton J. Lewis, Kerrie L. MacPherson in Public Health in Asia and the Pacific, 2007
Bancroftian filariasis is exquisitely adapted to its vectors by producing microfilariae at the precise biting times of the locally prevalent mosquito involved in transmission. Wuchereria Bancrofti has a near continuous distribution from its undoubted home in central Africa through the Middle East, South Asia, Indo-China, Southeast Asia, thence New Guinea, northern Australia (formerly), and the Pacific Islands through to eastern Polynesia. In this instance it was not possible for humans to outrun the disease vector, for Wuchereria Bancrofti proved very flexible, and has adapted to numerous mosquito species for transmission, including Anopheles malaria vectors in Melanesia, but also local Aedes and Culex species across Melanesia and Polynesia, which are much less fastidious breeders than Anopheles. Infection with Bancroftian filariasis leads to disease in only a small proportion of cases producing deformity and handicap rather than death. Nevertheless, asymptomatic cases are capable of spreading the disease to others. Other fellow travellers with early humans would have been intestinal worms. Hookworm can cause significant iron deficiency anaemia depending on the intensity of infection, concurrent iron loss from other sources (especially in women), and dietary iron intake. The eggs that pass out in the faeces require development in the soil to become infective larvae which then penetrate the bare feet of unsuspecting pedestrians. Hookworm anaemia produces tiredness and reduces productivity. The locally endemic variety, possibly brought by early humans is necator americanis, whereas ankylostoma duodenale may have been introduced by Asian immigrants (Hermant et al. 1929: 53). Ascaris lumbricoides, a parasite only of humans, with transmission by ingestion of eggs from the faeces of other infected humans, is usually asymptomatic. However, it can cause some direct illness, and also compete for calories and protein in the host gut, precipitating overt signs of under-nutrition in those (especially children) on a marginal diet. It may have been brought by original humans or introduced. Intestinal worms are still considerable problems in Pacific Island countries (Hughes et al. 2004: 163–177). Parasitic zoonoses (from animals) are infrequent in PNG and further east in the Pacific Islands, except those from imported pigs and dogs, because of the paucity of large mammals (Owen 2005: 1–14). Australasian fauna extends east from the Wallace line between Lombok and Bali and Borneo and Sulewesi. A new species of Trichinella (papuae) has been described in wild pigs in PNG with evidence of human infection – which presumably dates back to prehistory (Owen, Gomez Morales, Pezzotti and Pozio 2005: 618–624). The pig tapeworm (Taenia solium), which causes cysts in many organs (including the brain) in humans, was introduced to pigs in west Irian via Indonesia only in the 1970s, according to Desowitz, in his classic story of New Guinea tapeworms and Jewish grandmothers (Desowitz 1981). Other intestinal infections also probably accompanied the early human diasporas, although not those that require large dense populations for sustenance. Perhaps salmonella was a traveller because it can infect poultry, pigs, dogs and humans, and produces episodes of diarrhoea. Of endemic infections, yaws and hepatitis B were probable companions.
Treatment options in the management of Ascaris lumbricoides
Published in Expert Opinion on Pharmacotherapy, 2004
Cristiano Lara Massara, Martin Johannes Enk
Infection with Ascaris lumbricoides constitutes one of the most common helmintic diseases in the world, especially in tropical and subtropical regions. Transmission of this disease involves environmental contamination with eggs, and therefore, is classified as a soil-transmitted disease. The public health importance of ascariasis is made evident by the high number of infected individuals suffering its consequences, which can become severe, depending on the worm burden. Since the introduction of benzimidazoles, chemotherapy has improved significantly, offering fast and direct effects at relatively low cost, as a result of the simple and safe application of these drugs. Unfortunately, the effects are not long-lasting or permanent. The intervention with chemotherapy alone constitutes a fast and efficient way to reduce the worm burden in a population of high prevalence, but does not avoid reinfection. Therefore, the option of integrated control programmes based on chemotherapy in combination with sanitation and health education, together with strong community involvement, must be considered in order to ensure the positive long-term effects of such programmes.
Role of Pathogens in Multiple Sclerosis
Published in International Reviews of Immunology, 2014
Jane E. Libbey, Matthew F. Cusick, Robert S. Fujinami
Multiple sclerosis (MS) is an inflammatory demyelinating autoimmune disease of the central nervous system (CNS). Although the etiology of MS is unknown, genetic and environmental factors play a role. Infectious pathogens are the likely environmental factors involved in the development of MS. Pathogens associated with the development or exacerbation of MS include bacteria, such as Mycoplasma pneumoniae and Chlamydia pneumoniae, the Staphylococcus aureus-produced enterotoxins that function as superantigens, viruses of the herpes virus (Epstein-Barr virus and human herpesvirus 6) and human endogenous retrovirus (HERV) families and the protozoa Acanthamoeba castellanii. Evidence, from studies with humans and animal models, supporting the association of these various pathogens with the development and/or exacerbation of MS will be discussed along with the potential mechanisms including molecular mimicry, epitope spreading and bystander activation. In contrast, infection with certain parasites such as helminthes (Schistosoma mansoni, Fasciola hepatica, Hymenolepis nana, Trichuris trichiura, Ascaris lumbricoides, Strongyloides stercolaris, Enterobius vermicularis) appears to protect against the development or exacerbation of MS. Evidence supporting the ability of parasitic infections to protect against disease will be discussed along with a brief summary of a recent Phase I clinical trial testing the ability of Trichuris suis ova treatment to improve the clinical course of MS. A complex interaction between the CNS (including the blood-brain barrier), multiple infections with various infectious agents (occurring in the periphery or within the CNS), and the immune response to those various infections may have to be deciphered before the etiology of MS can be fully understood.
Epidemiology and management of foodborne nematodiasis in the European Union, systematic review 2000–2016
Published in Pathogens and Global Health, 2018
Marta Serrano-Moliner, María Morales-Suarez-Varela, M. Adela Valero
Background: Foodborne nematodiasis are caused by the ingestion of food contaminated by helminths. In Europe, these diseases are present in all countries. Objectives: To review the available data on epidemiology and management of foodborne nematodiasis in the European Union, detect any trends and determine the possible causes of the observed changes. Methods: A review of available literature published between 2000 and 2016 was conducted. Results: Out of 1523 cases described in the literature, 1493 cases were autochthonous and 30 cases were imported. The detected parasites were Toxocara spp (34.7%), Ascaris lumbricoides (27.1%), Trichinella spp (21.9%), Anisakis spp (15.5%) and Angiostrongylus cantonensis (0.8%). Conclusions: Foodborne nematodiasis remains a public health challenge for the European Union. Autochthonous cases of nematodiasis present the greatest health risk within the European Union. Foodborne nematodes due to lack of hygiene in food processing are diseases that can be avoided by increasing