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.
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.[3]
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.[4] 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.[5] 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.[3]
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.[6] In oesophagostomiasis, larvae can invade the colon wall, potentially causing two pervading types of nodular pathology. Multinodular disease is characterized by the formation of many tiny nodular lesions containing worms and pus along the colon wall. About 15% of patients have this form of oesophagostomiasis.[7] Nodules themselves are usually not a problem, but they can give rise to further complications, such as bowel obstruction, peritonitis and intestinal volvulus. In rare cases, serious disease can occur including emaciation, fluid in the pericardium, cardiomegaly, hepatosplenomegaly, perisplenitis and enlargement of the appendix.[citation needed]
Single-nodular disease, more commonly known as Dapaong disease, is characterized by the development of a single mass that develops throughout the colon wall. This is the most common form of oesophagostomiasis, affecting 85% of patients.[7] This nodule can instigate intense tissue reactions that result in the formation of painful projecting masses.
Common misdiagnoses include carcinoma, appendicitis, amebiasis and tuberculosis.[8]
The following is a summary of the second recorded case of oesophagostomiasis, as reported by H. Wolferstan Thomas in 1910:
Patient: male, 36 years old, native of the Rio Purus region in the Amazon State Chief complaints: suffering from acute dysentery, later experiencing deliriousness Outcome: Died within the three days following his admission. Major Findings: Lungs were emphysematous. Heart had evidence of hypertrophy in muscle, with some atheromatous patches along the aortic ring. Exterior of the small intestine was lined with several prominent tumors dark in color, 37 in total. Most of the tumors were found between the outside muscular layer and the bowel's peritoneal covering of the bowel. The tumors were generally small and varied in shape, from smooth ovular masses to flat button shapes to elongated masses akin to a leech; they were elevated by as much as 6 to 8mm above the bowl surface. These nodules were found to contain one worm each, no more, no less. In the interior of the small intestine, twenty nodules were found along the walls, causing a discernible bulging of the mucous membrane. The caecum walls were irregularly thickened and dark in color, with three ovular tumors containing immature adult Oesophagostomum. Interior of the caecum was filled with rope-like opaque masses of rows of cystic tumors, which caused great thicking of the walls. Examination of the exterior of the ascending colon revealed the formation of thick adhesions spanning the whole length of the colon; these adhesions were filled with fat, enlarged glands and omental tissue. Underneath were a multitude of small cystic tumors that ruptured upon disturbance of the adhesion, disclosing small worms. The interior of the colon was most affected, with tumors of widely varying shapes and sizes occupying the walls and floor of the gut, causing as much as 5mm of thickening of colon walls.[5]
Transmission
Egg of Oesophagostomum sp. from primates in Côte d'Ivoire
Transmission of Oesophagostomum is believed to be oral-fecal for both humans and animals, largely because percutaneous infection with Oesophagostomum has never been reported.[9] It is unclear whether or not parasite transmission is specifically waterborne, foodborne, or both. Regardless, introduction of the stage three infective larvae is necessary for human infection. Much about the biological mechanism of transmission is still unknown, and current knowledge of oral-fecal transmission mechanisms does not explain why Oesophagostomum are mostly localized to Northern Togo and Ghana. It is possible that there are behavioral factors or unique soil conditions that facilitate larval development and are not found outside the current endemic areas.[9] Oesophagostomiasis is generally classified as a zoonotic disease, which is an infectious disease that can be transmitted between animals and humans. This has been called into question recently, as recent research has found that human-to-human transmission is possible.[8]
Reservoir
Oesophagostomum are carried predominantly by non-humans, infecting cattle, sheep, goats, wild pigs, and primates. Humans are largely presumed to be an accidental host, as they are not suitable for completion of the Oesophagostomum development; however, the extreme localization of oesophagostomiasis to northern Togo and Ghana in Africa suggests the possibility that the Oesophagostomum is increasingly exhibiting preference for human hosts.[10]
Until recently it was believed that primates were the main reservoirs of human-infecting Oesophagostomum in northern Togo and Ghana, as these particular species have a considerable concentration in non-human primate reservoirs. A 2005 study done by van Lieshout and de Gruijter found that O. bifurcum in humans from northern Ghana is distinct from the O. bifurcum found in olive baboons and mona monkeys outside the endemic area. They used species-specific PCR and microscopy to establish the identification of two separate species of O. bifurcum.[11] These results are significant, as they necessitate further research to determine the definitive reservoirs of human-infecting O. bifurcum.
The life-cycle of Oesophagostomum can usually be completed in less than 60 days.[9] When the eggs are passed into the feces to the outside environment, they hatch into stage one larve. The stage two larve then molt twice, developing into infective stage three larva in 6–7 days. These stage three larvae can survive extended periods of desiccation by shrinking within their sheaths.[3]
Morphology
Morphology
Adult worms of all Oesophagostomum spp. exhibit a cephalic groove by its proximal gut as well as a visible secretory pore, or stomum, at the same level of the oesophagus19. Like other nematodes, Oesophagostomum spp. contain a developed, multi-nucleate digestive tract as well as a reproductive system. Their developed buccal capsule and club-shaped oesophagus are useful for distinguishing Oesophagostomum spp. from hookworms.[12]
Both sexes of adults have a cephalic inflation and an oral opening lined with both internal and external leaf crowns.[6] Female adults, which have a length range of 6.5–24mm, are generally larger than their male counterparts, with a length range of 6–16.6mm. Males can be distinguished by their bell-like copulatory bursa, located in the tail, and their paired rodlike spicules.[9]
Eggs are ovular in shape and range from 50 to 100 micrometres in size; they closely resemble those of hookworms, which renders diagnosis via stool analysis useless in areas co-infected with both Oesophagostomum and hookworm.[9]
Life cycle
Life cycle
For non-human hosts, the life cycle of Oesophagostomum begins with the passing of eggs in the animal feces. From there the eggs develop into stage one larvae. These larvae then spend 6–7 days in the environment developing into stage two and then infectious stage three larvae.[9] Infection begins with the ingestion of soil contaminated with stage three larvae. After ingestion the larvae end up in the large intestine, unsheathing and penetrating the intestinal wall to form nodules. The resulting adult worms that remain in the intestinal lumen copulate; the eggs from the female are then deposited in the feces. Females usually lay around 5,000 eggs per day, which is on par with reproductive rates of other nematodes within Strongyloidea.[13]
For human hosts, the life cycle is very similar to that of Oesophagostomum in animals. It begins when an animal reservoir defecates into the soil, leaving feces infested with eggs that develop into rhabitiform larvae.[9] These larve then develop into stage two and then infectious stage three larvae in the environment over the course of 6–7 days. Human infection occurs when soil or water containing the third-stage larvae is ingested, presumably via contaminated meat obtained from infected livestock or crops with contaminated soil. Once ingested, the filariform larvae migrate to the submucosa of the small or large intestine, then to the lumen of the colon. The developing worms then penetrate the intestinal tissues, causing nodular lesion formation in the intestines and colon; it is in these nodules that the larvae mature to stage four larvae.[10] These larvae may then emerge from their nodules and migrate back to the intestinal lumen, where they mature into adults. But many larvae often do not complete development and remain in their colon nodules, as humans are generally unsuitable hosts for Oesophagostomum. The instances where Oesophagostomum have completed development in humans seem to be dependent on certain environmental and host factors that have yet to be identified.[14]
Diagnostic tests
A definitive diagnosis of Oesophagostomum infection is traditionally done by demonstrating the presence of the larval or young adult forms in nodules of the intestinal wall via surgical examination of tissue. The larvae usually found in tissues can be 500 nanometers or longer in length.[9] With microscopy, one can identify the larvae based on the presence of somatic musculature divided into four quarters, along with a multinucleated intestine as well as an immature reproductive system.[8]
Laboratory methods are of little use for Oesophagostomum diagnosis. It is virtually impossible to make a diagnosis based on microscopy of stool samples alone, as Oesophagostomum eggs cannot be differentiated from hookworm eggs, which are often found in Oesophagostomum endemic areas.[3] The only way to differentiate between the two species of eggs is to perform coproculture, which allows eggs to develop to their stage three larvae, although this is both time-consuming and unreliable.[10] Immunoassay tests like ELISA that monitoring for increases in IgG4 antibodies can indicate tissue invasion by Oesophagostomum.[3]
Recent advances, however, have allowed for less invasive and more accurate methods of diagnosis. The following is a review of three articles detailing the diagnostic use of PCR assays and sonographic imaging. Verweij, Jaco J., Anton M. Polderman, et al. “PCR assay for the specific amplification of Oesophagostomum bifurcum DNA from human faeces.” International Journal for Parasitology 30.2 (2000): 137-142. This study developed a molecular-based approach to diagnosing oesophagostomiasis caused by O. bifurcum in humans. Using genetic markers in ribosomal DNA, the researchers developed PCR assays to selectively amplify O. bifurcum DNA from human fecal samples. These assays achieved sensitivity ratings of 94.6% and specificity of 100%, suggesting that the PCR method could be a viable alternative to the long-standing methods of diagnosis as well as an opportunity to reveal more about the epidemiology of oesophagostomiasis.[15]
Storey, P A, S Anemana, et al. “Ultrasound diagnosis of oesophagostomiasis.” Br. J. Radiol. 73.867 (2000): 328-32.
Sonographic imaging and ultrasound were used to examine two cases of oesophagostomiasis in the Nalerigu hospital in northern Ghana. The technology allowed for the detection of intestinal and abdominal wall modules, as well as their size, type and location in the case of the ultrasound. Multinodular disease was representedby nodular colonic lesions and pseudokidney appearances, while the single-nodular Dapaong tumor had the appearance of an echo-free lumen surrounded by a defined but badly reflective wall. The ability to diagnose oesophagostomiasis via ultrasound can reduce the number of excessive invasive surgeries and put greater emphasis on chemotherapy.[16]
Verweij, Jaco J, Eric A T Brienen, et al. “Simultaneous detection and quantification of Ancylostoma duodenale, Necator americanus and Oesophagostomum bifurcum in fecal samples using multiplex real-time PCR. (2007) Am. J. of Trop. Med. Hygiene 77 (4) 685-690
A multiplex PCR method was developed for simultaneously detection of A. dudodenale, N. americanus and O. bifurcum in human fecal samples. The method was tested on human fecal samples from an area in Ghana where co-infections with all three species are endemic. Results showed that the method was both highly specific and sensitive, attaining 100% specificity and sensitivities of 100%, 86.7%, and 100% for detection of N. americanus, O. bifurcum and A. duodenale respectively. Furthermore, cycle threshold values, which correspond to parasite-specific DNA load, correlated with measured intensity of infection as demonstrated in Kato-Kato smears. This PCR method could potentially elucidate species-specific transmission pathways of hookworm-like infections and improve monitoring of interventions.[17]
Management and therapy
The typical adult therapy for oesophagostomiasis is a single 400mg dose of albendazole (200mg for children) or pyrantel pamoate.[7] 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.[8] 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.[8]
For oesophagostomiasis with complications, the type of treatment varies depending on the severity of the disease. Usually 200–400mg of albendazole will be given immediately and continued for up to 5 days in conjunction with 250mg dosages of amoxicillin.[9] 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.[9]
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.[7] 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.[7]O. bifurcum infection in northern Togo and Ghana is found in virtually every village, with some rural areas exhibiting as much as 90% prevalence.[10]
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.[10]
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.[13] 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.[citation needed]
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. Females showed higher prevalence of infection (34%) than men (24%). Based on these epidemiological studies, this group was able 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.[18]
"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 and 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.[19]
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.[9]
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.[20]
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.[14]
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.[21]
Related Research Articles
Strongyloides stercoralis is a human pathogenic parasitic roundworm causing the disease strongyloidiasis. Its common name in the US is threadworm. In the UK and Australia, however, the term threadworm can also refer to nematodes of the genus Enterobius, otherwise known as pinworms.
Trichuriasis, also known as whipworm infection, is an infection by the parasitic worm Trichuris trichiura (whipworm). If infection is only with a few worms, there are often no symptoms. In those who are infected with many worms, there may be abdominal pain, fatigue and diarrhea. The diarrhea sometimes contains blood. Infections in children may cause poor intellectual and physical development. Low red blood cell levels may occur due to loss of blood.
Toxocariasis is an illness of humans caused by the dog roundworm and, less frequently, the cat roundworm. These are the most common intestinal roundworms of dogs, coyotes, wolves and foxes and domestic cats, respectively. Humans are among the many "accidental" or paratenic hosts of these roundworms.
Hymenolepiasis is infestation by one of two species of tapeworm: Hymenolepis nana or H. diminuta. Alternative names are dwarf tapeworm infection and rat tapeworm infection. The disease is a type of helminthiasis which is classified as a neglected tropical disease.
Hookworm infection is an infection by a type of intestinal parasite known as a hookworm. Initially, itching and a rash may occur at the site of infection. Those only affected by a few worms may show no symptoms. Those infected by many worms may experience abdominal pain, diarrhea, weight loss, and tiredness. The mental and physical development of children may be affected. Anemia may result.
Baylisascaris is a genus of roundworms that infect more than fifty animal species.
Necator americanus is a species of hookworm commonly known as the New World hookworm. Like other hookworms, it is a member of the phylum Nematoda. It is an obligatory parasitic nematode that lives in the small intestine of human hosts. Necatoriasis—a type of helminthiasis—is the term for the condition of being host to an infestation of a species of Necator. Since N. americanus and Ancylostoma duodenale are the two species of hookworms that most commonly infest humans, they are usually dealt with under the collective heading of "hookworm infection". They differ most obviously in geographical distribution, structure of mouthparts, and relative size.
Taeniasis is an infection within the intestines by adult tapeworms belonging to the genus Taenia. There are generally no or only mild symptoms. Symptoms may occasionally include weight loss or abdominal pain. Segments of tapeworm may be seen in the stool. Complications of pork tapeworm may include cysticercosis.
Parasitic worms, also known as helminths, are large macroparasites; adults can generally be seen with the naked eye. Many are intestinal worms that are soil-transmitted and infect the gastrointestinal tract. Other parasitic worms such as schistosomes reside in blood vessels.
Ancylostoma duodenale is a species of the roundworm genus Ancylostoma. It is a parasitic nematode worm and commonly known as the Old World hookworm. It lives in the small intestine of hosts such as humans, cats and dogs, where it is able to mate and mature. Ancylostoma duodenale and Necator americanus are the two human hookworm species that are normally discussed together as the cause of hookworm infection. They are dioecious. Ancylostoma duodenale is abundant throughout the world, including Southern Europe, North Africa, India, China, southeast Asia, some areas in the United States, the Caribbean, and South America.
Uncinaria stenocephala is a nematode that parasitizes dogs, cats, and foxes as well as humans. It is rare to find in cats in the United States. Uncinaria stenocephala is the most common canine hookworm in cooler regions, such as Canada and the northern regions of the US, where it can be found primarily in foxes (40%). U. stenocephala is also one of the most common hookworms in the UK, called the northern hookworm, however it has a rather low prevalence. U. stenocephala is also considered to be zoonotic hookworms because they live in animals but can be transmitted to humans.
Ancylostomiasis is a hookworm disease caused by infection with Ancylostoma hookworms. The name is derived from Greek ancylos αγκύλος "crooked, bent" and stoma στόμα "mouth".
Necatoriasis is the condition of infection by Necator hookworms, such as Necator americanus. This hookworm infection is a type of helminthiasis (infection) which is a type of neglected tropical disease.
Trichostrongylus species are nematodes, which are ubiquitous among herbivores worldwide, including cattle, sheep, donkeys, goats, deer, and rabbits. At least 10 Trichostrongylus species have been associated with human infections. Infections occur via ingestion of infective larvae from contaminated vegetables or water. Epidemiological studies indicate a worldwide distribution of Trichostrongylus infections in humans, with the highest prevalence rates observed in individuals from regions with poor sanitary conditions, in rural areas, or who are farmers / herders. Human infections are most prevalent in the Middle East and Asia, with a worldwide estimated prevalence of 5.5 million people.
Pinworm infection, also known as enterobiasis, is a human parasitic disease caused by the pinworm, Enterobius vermicularis. The most common symptom is itching in the anal area. The period of time from swallowing eggs to the appearance of new eggs around the anus is 4 to 8 weeks. Some people who are infected do not have symptoms.
Trichuris vulpis is a whipworm that lives in the large intestine of canines in its adult stages. Out of different types of worms, Trichuris vulpis is one of the smaller worms with a size ranging from 30–50 mm in length. As the name suggests, the worm has a whip-like shape with distinct features including a small, narrow anterior head, which is the digestive part of the worm, and a larger posterior tail, which is the reproductive part of the worm. Eggs from T. vulpis are oval shaped with bipolar plugs and contain a thick outer shell. Their sizes range from 72–90 μm in length and 32–40 μm in width. Because of their thick outer shell, T. vulpis eggs are very resistant to environmental extremes such as freezing or hot temperatures, thus allowing for their long viability in the outside world.
Baylisascaris procyonis, also known by the common name raccoon roundworm, is a roundworm nematode, found ubiquitously in raccoons, the definitive hosts. It is named after H. A. Baylis, who studied them in the 1920s–30s, and Greek askaris. Baylisascaris larvae in paratenic hosts can migrate, causing larva migrans. Baylisascariasis as the zoonotic infection of humans is rare, though extremely dangerous due to the ability of the parasite's larvae to migrate into brain tissue and cause damage. Concern for human infection has been increasing over the years due to urbanization of rural areas resulting in the increase in proximity and potential human interaction with raccoons.
Soil-transmitted helminthiasis is a type of worm infection (helminthiasis) caused by different species of roundworms. It is caused specifically by those worms which are transmitted through soil contaminated with faecal matter and are therefore called soil-transmitted helminths. Three types of soil-transmitted helminthiasis can be distinguished: ascariasis, hookworm infection and whipworm infection. These three types of infection are therefore caused by the large roundworm A. lumbricoides, the hookworms Necator americanus or Ancylostoma duodenale and by the whipworm Trichuris trichiura.
Hookworms are intestinal, blood-feeding, parasitic roundworms that cause types of infection known as helminthiases. Hookworm infection is found in many parts of the world, and is common in areas with poor access to adequate water, sanitation, and hygiene. In humans, infections are caused by two main species of roundworm, belonging to the genera Ancylostoma and Necator. In other animals the main parasites are species of Ancylostoma. Hookworm is closely associated with poverty because it is most often found in impoverished areas, and its symptoms promote poverty through the educational and health effects it has on children. It is the leading cause of anemia and undernutrition in developing countries, while being one of the most commonly occurring diseases among poor people. Hookworm thrives in areas where rainfall is sufficient and keeps the soil from drying out, and where temperatures are higher, making rural, coastal areas prime conditions for the parasite to breed.
Nematode infection in dogs - the infection of dogs with parasitic nemamotodes - are, along with tapeworm infections and infections with protozoa, frequent parasitoses in veterinary practice. Nematodes, as so-called endoparasites, colonize various internal organs - most of them the digestive tract - and the skin. To date, about 30 different species of nematode have been identified in domestic dogs; they are essentially also found in wild dog species. However, the majority of them often cause no or only minor symptoms of disease in adult animals. The infection therefore does not necessarily have to manifest itself in a worm disease (helminthosis). For most nematodes, an infection can be detected by examining the feces for eggs or larvae. Roundworm infection in dogs and the hookworm in dogs is of particular health significance in Central Europe, as they can also be transmitted to humans (zoonosis). Regular deworming can significantly reduce the frequency of infection and thus the risk of infection for humans and dogs.
References
↑ John, David T., Krotoski, Wojciech A. and Markell, Edward K. Markell and Voge's Medical Parasitology. St. Louis: Saunders Elsevier, 2006. 9th ed.
1 2 3 4 5 Polderman, A. M., and J. Blotkamp. “Oesophagostomum infections in humans.” Parasitology Today 11.12 (1995): 451-456.
↑ Polderman, A. M.; Gigase, P.; Krepel, H. P.; Blotkamp, J.; Baeta, S. (1991). "Oesophagostomiasis, a common infection of man in northern Togo and Ghana". American Journal of Tropical Medicine and Hygiene. 44 (3): 336–344. doi:10.4269/ajtmh.1991.44.336. PMID2035755.
1 2 Thomas, H.W. (1910). The pathological report of a case of oesophagostomiasis in man. Annals of Tropical Medicine and Parasitology. 4: 57-88.
1 2 Ash, Lawrence R. and Orihel, Thomas C. Parasites in Human Tissues. Chicago: ASCP Press, 1995.
1 2 3 4 5 Gasser, R. B.; de Gruijter, J. M.; Polderman, A. M. (April 2006). "Insights into the epidemiology and genetic make-up of Oesophagostomum bifurcum from human and non-human primates using molecular tools". Parasitology. 132 (Pt 4): 453–60. doi:10.1017/S0031182005009406. PMID16332292. S2CID6156503.
↑ Elmes, B. G. T.; McAdam, I. W. J. (1954). "Helminthic abscess, a surgical complication of oesophagostomes and hookworms". Annals of Tropical Medicine & Parasitology. 48 (1): 1–7. doi:10.1080/00034983.1954.11685590. PMID13149111.
1 2 Krepel, H.P.; Polderman, A.M. (1992). "Egg production of Oesophagostomum bifurcum, a locally common parasite of humans in Togo". American Journal of Tropical Medicine and Hygiene. 46 (4): 469–472. doi:10.4269/ajtmh.1992.46.469. PMID1575294.
1 2 Ziem, Juventus B.; Magnussen, Pascal; Olsen, Annette; Horton, John; Asigri, Von L. L.; Polderman, Anton M. (2006). "Impact of repeated mass treatment on human Oesophagostomum and hookworm infections in northern Ghana". Tropical Medicine and International Health. 11 (11): 1764–1772. doi:10.1111/j.1365-3156.2006.01729.x. PMID17054758. S2CID30212124.
↑ Verweij, Jaco J., Anton M. Polderman, et al. “PCR assay for the specific amplification of Oesophagostomum bifurcum DNA from human faeces.” Int. J. Parasitol. 30.2 (2000): 137-142.
↑ Storey, P A, S Anemana, et al. “Ultrasound diagnosis of oesophagostomiasis.” Br. J. Radiol. 73.867 (2000): 328-32.
↑ Verweij, Jaco J, Eric A T Brienen, et al. “Simultaneous detection and quantification of Ancylostoma duodenale, Necator americanus and Oesophagostomum bifurcum in fecal samples using multiplex real-time PCR.” Am. J. Trop. Med. and Hygiene 77.4 (2007): 685-690.
↑ "Human Oesophagostomum infection in northern Togo and Ghana: epidemiological aspects." By: Krepel et al. Annals of Tropical Medicine and Parasitology.1992. 86:289-300.
↑ "Clinical epidemiology and classification of human oesophagostomiasis." By: P.A. Storey et al. Trans R Soc Trop Med Hyg. 2000. 94:177-182.
↑ Polderman, A. M., S. D. Anemana, and V. Asigri. “Human Oesophagostomiasis: A Regional Public Health Problem in Africa.” Parasitology Today 15.4 (1999): 129-130.
↑ 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.
Online resources
- a free online compendium of all aspects of Oesophagostomum bifurcum biology
- J.B. Ziem's doctoral thesis on controlling human oesophagostomiasis in northern Togo and Ghana
- A.M. Polderman's review on human oesophagostomiasis
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
