Oesophagostomum

style="background:#Template:Taxobox colour;"|Template:Taxobox name
style="background:#Template:Taxobox colour;" | Scientific classification
Kingdom: Animalia Phylum: Nematoda Order: Strongylida Family: Strongyloidae Genus: Oesophagostomum Species: Oesophagostomum aculeatum Oesophagostomum bifurcum Oesophagostomum brumpti Oesophagostomum stephanostomum Oesophagostomum stephanostomum var thomasi

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Management and therapy

The typical adult therapy for oesophagostomiasis is a single 400 mg dose of albendazole (200 mg for children) or pyrantel pamoate. Albendazole works by binding to the free beta tubulin, which inhibits tubulin polymerization. This results in the inhibition of glucose uptake by the Oesophagostomum. Albendazole and pyrantel pamoate at these doses have cure rates of 85% and 59-82%, respectively. Excision of Oesophagostomum larvae from nodules has been shown to have a curative effect on the patient but is invasive and more resource intensive than chemotherapy.

For oesophagostomiasis with complications, the type of treatment varies depending on the severity of the disease. Usually 200–400 mg of albendazole will be given immediately and continued for up to 5 days in conjunction with 250 mg dosages of amoxicillin. In the case of formation of abscesses or fistulae arising from Dapaong tumors, incision and drainage is performed, followed by a regimen of albendazole and antibiotic treatment.

Epidemiology

Oesophagostomiasis is endemic or potentially endemic to 35 countries; approximately 250,000 are infected worldwide, with 1 million more at risk according to the Gideon Infectious Diseases Database. Most of the cases originate in Africa, specifically in Ghana, Togo, Uganda, Nigeria, Zimbabwe and other nearby countries. A few sporadic cases have been reported in countries in South America and Southeast Asia, including Brazil, Indonesia and Malaysia. The vast majority of clinical cases have been collected from northern Togo and Ghana, in West Africa. 156 cases from the areas alone were collected in a 2000 study; before then, only 116 cases were recorded in the literature. O. bifurcum infection in northern Togo and Ghana is found in virtually every village, with some rural areas exhibiting as much as 90% prevalence.

Prevalence is higher in children between ages 2–10), and females older than 5 years of ages have higher prevalence than males within the same age group. These age demographic and gender discrepancies are not yet sufficiently explained – possible factors include differential exposure to contaminated water and strength of immune response.

A study done by Krepel in 1992 revealed a correlation between infection with O. bifurcum and N. americanus in that individuals living in endemic villages were either coinfected with both parasites or neither. This could be due to cofactors shared by both parasites, including poor hygiene, certain agricultural practices and the dearth of potable water suitable for consumption.

Below is a review of some epidemiological studies on the epidemiology of Oesophagostomum bifurcum in northern Togo and Ghana.

"Human Oesophagostomum infection in northern Togo and Ghana: epidemiological aspects." By: Krepel et al. Annals of Tropical Medicine and Parasitology.1992. 86:289-300.

A regional survey of O. bifurcum infection was carried out in Togo and Ghana. The parasite was found in 38 of the 43 villages surveyed, with the highest prevalence rates reaching 59% in some small, isolated villages. Infection was found to be positively correlated with hookworm infection; however, the difficulty in distinguishing these parasites may have had some confounding effect. Infection rates were low in children under 3 years of age, beyond that, rates of infection increased dramatically until 10 years of age. Interestingly, females showed higher prevalence of infection (34%)than men (24%). Based on these epidemiological studies, this group was ale to conclude that tribe, profession, or religion had no effect on the prevalence of infection in the different communities surveyed. The habitats and life cycle of this parasite do not explain its distribution.

"Clinical epidemiology and classification of human oesophagostomiasis." By: P.A. Storey et al. Trans R Soc Trop Med Hyg. 2000. 94:177-182.

The study investigated the clinical epidemiology of oesophagostomiasis by observing 156 cases in the Nalerigu hospital between 1996-1998. About 1 patient/week presented with this disease over the course of two years and 1% of all surgeries carried out were related to oesophagostomiasis. 13% of the patients presented with the multinodular form of the disease in which they had several nodules in their small intestine, abdominal pain, diarrhea, and weight loss. The other 87% of the patients presented with the Dapaong, or single, tumor form of the disease that was associated with inflammation in the abdomen, fever, and pain.

Public health and prevention strategies/vaccines

Given that infective Oesophagostomum larvae are most likely transmitted via oral-fecal routes, sufficiently cleaning and cooking meat and vegetables, as well as boiling all consumed water or only using potable water would help to complement a mass treatment program. Factors like religion, family size and wealth do not suffice in explaining the unique epidemiology of Oesophagostomum; geographic and geological factors must be explored in more detail.

Since oesophagostomiasis is primarily a regional problem (localized in northern Ghana and Togo, an optimal approach to addressing it requires mobilization of resources within and around the endemic area. One proposed solution is to organize all research and intervention projects at the local level, so as to instill knowledge of the infection in the community, and establish a regional collaboration between Ghana, Togo, and Burkina Faso in order to effectively combat oesophagostomiasis.

There is no vaccine for oesophagostomiasis, although prolonged treatment with albendazole seems to be highly effective in countering the Oesophagostomum threat. In fact, recent research indicates that albendazole treatment may be the best intervention available for eliminating oesophagostomiasis from northern Togo and Ghana; following treatment, prevalence continued to go down even with interruption of the intervention. The following is a review of J. B. Ziem’s study of a mass treatment campaign in northern Ghana, as well as the follow-up conducted with the Lymphatic Filariasis Elimination Program.

Ziem, Juventus B et al. “Impact of repeated mass treatment on human Oesophagostomum and hookworm infections in northern Ghana.” Tropical Medicine & International Health: TM & IH 11.11 (2006): 1764-72.

This was a two year study, with four rounds of albendazole treatment administered to a village in Ghana; the target area and an untreated control area were monitored. In the target area, prevalence went down dramatically from 53.0% to 5.4% in the first year to 0.8% in the second year. Larval counts in stools also went down, as well as hookworm prevalence. In contrast, the control area saw an increase in prevalence from 18.5% to 37%. The results indicate potential for elimination of oesophagostomiasis utilizing similar albendazole-distributing mass treatment programs.

Ziem, J. B. et al. “Annual mass treatment with albendazole might eliminate human oesophagostomiasis from the endemic focus in northern Ghana.” Tropical Medicine & International Health: TM & IH 11.11 (2006): 1759-63.

This follow-up to the original two-year study by J.B. Ziem saw collaboration with the Lymphatic Filariasis Elimination Programme, essentially expanding the scope of the Oesophagostomum Intervention Research Program that Ziem worked under. 11 villages across northeastern Ghana were given albendazole-ivermectin treatment and monitored for changes in prevalence; once again, decreases in both Oesophagostomum and hookworm infections occurred after two years of mass treatment. However, after interrupting mass treatment, Oesophagostomum prevalence continued to decrease even as hookworm prevalence increased again. Human oesophagostomiasis infection thus seems interruptible; even small numbers of persistent Oesophagostomum post-treatment were not sufficient to cause reinfection.

Online resources

• [2] - a free online compendium of all aspects of Oesophagostomum bifurcum biology
• [3] - Gideon Infectious Disease database entry on oesophagostomiasis
• [4] - J.B. Ziem’s doctoral thesis on controlling human oesophagostomiasis in northern Togo and Ghana
• [5] - A.M. Polderman’s review on human oesophagostomiasis