Oesophagostomum
Oesophagostomum is a genus of parasitic nematodes (roundworms) of the family Strongylidae. These worms occur in Africa, Brazil, China, Indonesia and the Philippines. The majority of human infection with Oesophagostomum is localized to northern Togo and Ghana. Because the eggs may be indistinguishable from those of the hookworms (which are widely distributed and can also rarely cause helminthomas), the species causing human helminthomas are rarely identified with accuracy. Oesophagostomum, especially O. bifurcum, are common parasites of livestock and animals like goats, pigs and non-human primates, although it seems that humans are increasingly becoming favorable hosts as well. The disease they cause, oesophagostomiasis, is known for the nodule formation it causes in the intestines of its infected hosts, which can lead to more serious problems such as dysentery. Although the routes of human infection have yet to be elucidated sufficiently, it is believed that transmission occurs through oral-fecal means, with infected humans unknowingly ingesting soil containing the infectious filariform larvae. Oesophagostomum infection is largely localized to northern Togo and Ghana in western Africa where it is a serious public health problem. Because it is so localized, research on intervention measures and the implementation of effective public health interventions have been lacking. In recent years, however, there have been advances in the diagnosis of Oesophagostomum infection with PCR assays and ultrasound and recent interventions involving mass treatment with albendazole shows promise for controlling and possibly eliminating Oesophagostomum infection in northern Togo and Ghana. Taxonomy and classification Oesophagostomum is part of the phylum Nematoda. This phylum is composed of five orders: Ascaridida, Enoplida, Oxyurida, Spirurida, Strongylida and Rhabditida. Strongylida has three superfamilies - Ancyclostomatoidea, Trichostrongyloidea and Strongylidea. Oesophagostomum lie within the Strongyloidae. Synonyms The prominent, single-nodule form of oesophagostomiasis is often referred to as Dapaong tumor named after a city in northern Togo. Within the villages of Togo, villagers often refer to it as ‘Kounkoul’, which means ‘turtle’ in the native Moba-language; the name aptly describes the hard, round mass in the patient's abdomen. History of discovery The first case of infection by Oesophagostomum spp. was reported in 1905 by Railliet and Henry, describing parasites found in the tumors of the caecum and colon of a male hailing from the Omo River in Southern Ethiopia. In 1910, H. Wolferstan Thomas reported the second known case, describing the macroscopical and microscopical pathology of Oesophagostomum stephanostomum. His descriptions were based on his observations regarding the post mortem of an infected Brazilian man who died from extreme dysentery. In subsequent decades, several more cases of Oesophagostomum spp. infection in humans were found in Brazil, Indonesia, Canada, and several areas of Africa, particularly Northern Ghana, Nigeria and Brazil. Of all reported Oesophagostomum human infections, only O. aculeatum, O. bifurcum and O. stephanostomum have been identified with certainty. Clinical presentation in humans There is no overarching clinical picture for symptoms of oesophagostomiasis; however, most patients experience pain in the lower right quadrant, accompanied by the presence of one or several protruding abdominal masses. In oesophagostomiasis, larvae can invade