Gongylonema pulchrum: The Gullet Worm

Gongylonema pulchrum, the gullet worm, is a roundworm of cattle, goats, deer and many other mammals around the world, and it occasionally infects people [1][2][3]. In humans it is usually found in the mouth, and the most common symptom is the feeling of something moving there [1]. Human cases are rare: a 2012 report counted approximately 50 worldwide [4].

This page describes the worm and its life cycle, how people pick it up, the symptoms, how it is identified and treated, and the human cases reported from the United States, Europe and Asia. It also explains how a related species, a stomach worm of rats, became the subject of the 1926 Nobel Prize in medicine.

Table of Contents

  1. What Gongylonema pulchrum Is
  2. Its Life Cycle
  3. How People Become Infected
  4. Symptoms
  5. How It Is Diagnosed
  6. Treatment
  7. Human Cases Around the World
  8. Gongylonema and the 1926 Nobel Prize
  9. A Worm Felt Moving in the Mouth
  10. Key Research Papers
  11. Connections
  12. Featured Videos

What Gongylonema pulchrum Is

Gongylonema pulchrum is a nematode, the scientific name for a roundworm. A 2021 literature review describes it as a spiruroid nematode usually seen in ruminants, the cud-chewing animals such as cattle, goats and deer, and known to occasionally infect humans [1]. Spiruroid worms are a group of roundworms whose larvae develop inside insects or their relatives before they can infect their final host (see Its Life Cycle below).

The worm's common name is the gullet worm [2]. It is found worldwide in the mucosa, the moist lining, of the upper digestive tract of a variety of domestic and wild mammals, and of humans [3]. Infection with the worm is called gongylonemiasis [5].

Genetic studies have recorded the gullet worm in:

The Slovenian report describes the parasite as likely to be underdiagnosed, misdiagnosed or unnoticed in animals, which show little or no sign of illness and only minor damage. Its authors call on slaughterhouse workers, hunters and veterinarians to be aware of it [7].

Gongylonema worms look much alike, and their species are hard to tell apart by shape alone [2][8]. Genetic testing has shown that not every gullet worm is Gongylonema pulchrum: in 2016, a worm from water buffaloes in Nepal, described in the same research group's earlier study, was named a new species, Gongylonema nepalensis [2]. That species is known from Nepal and from Sardinia, Italy, where it has been recorded in cattle, sheep, goats and wild mouflon (a wild sheep), and in a red fox and a wild boar [3].

Worms of the genus also turn up in other animals. Two female Gongylonema worms, not identified to species, were collected from the lining of the tongue of a brown-nosed coati (Nasua nasua), a raccoon relative, in the Atlantic Forest of Minas Gerais, Brazil. It was the first report of the genus in Brazilian wild carnivores [9].

Its Life Cycle

Gongylonema worms need two kinds of host. The definitive host is the animal in which the worm grows to adulthood and breeds. The intermediate host is an animal in which the larva, the young stage, develops until it can infect a definitive host. A 2022 study describes Gongylonema as a genus whose cycle includes a coprophagous, or dung-eating, arthropod (an insect or one of its relatives) as intermediate host [10].

Definitive hosts: mammals

Adult gullet worms live in the lining of the upper digestive tract of domestic and wild mammals [3]. In the roe deer from Slovenia, adult female and male worms were found in the gullet [7]. Genetic studies in Japan found two separate transmission cycles, one in cattle and one in wild mammals [2]. Worms from native wild mammals in Japan differed genetically from those in cattle, but worms from feral (wild-living) Reeves's muntjacs, a deer not native to Japan, carried the cattle type. The authors write that contact between domestic and wild mammals, and their susceptibility to different Gongylonema species, need to be taken into account to understand how the worm spreads in nature [3].

Intermediate hosts: beetles and cockroaches

Scarab beetles (family Scarabaeidae), the family that includes dung beetles, are reported to serve as intermediate hosts for a related species, Gongylonema ingluvicola. In a 2010 laboratory study, beetles and other arthropods were exposed to that worm's eggs and then dissected to look for developing larvae. Of the two species exposed to that worm, only one, the dung beetle Gymnopleurus humanus, became infected, and no larvae of that worm were found in the millipede species tested [11].

Cockroaches are the other documented intermediate host. Since 1997, young scops owls (Otus scops) brought to an owl rescue centre in Madrid, Spain, have arrived with white plaques of dead tissue in their mouths. The condition, called necrotic oropharyngeal disease, can lead to death by starvation [10]. In 2011 alone, thirty-five cases were identified; in severe cases the damage reached the bone, and the clinical, tissue and genetic findings pointed to a Gongylonema species [12]. To find its intermediate host, researchers used a camera trap to record the prey brought to the owlets and trapped arthropods in the owls' hunting areas. They tested the arthropods with real-time polymerase chain reaction (PCR), a test that detects a parasite's genetic material (deoxyribonucleic acid, or DNA). Only oriental cockroaches (Blatta orientalis) tested positive, at 66.7%. In one gene, the worms from the cockroaches were 99.8% identical to the worm first isolated from a scops owl, and the authors concluded that the oriental cockroach can be regarded as an intermediate host of the owl disease [10].

In the owls, larvae were identified but no evidence of adult worms was found, so the researchers suggest that the owls are accidental hosts: animals outside the worm's usual cycle [12].

The infective larva

Infection starts when infective larvae are swallowed. In a 2008 laboratory study, third-stage larvae of the gullet worm (the infective stage) given by mouth to mice invaded the lining of the stomach, and rabbits infected with 30 such larvae carried adult worms four months later [13]. People are not part of the worm's usual cycle: a 2012 report describes humans as incidental, or accidental, hosts of the worm [4].

How People Become Infected

Gongylonemiasis is a zoonosis, an infection that people catch from the animal world [14]. A 2001 case report from Massachusetts describes it as a foodborne infection, acquired by accidentally swallowing an infected insect such as a beetle or a cockroach [15].

A 2018 case report and literature review states that the infection occurs throughout the world and is mainly caused by consuming contaminated water and raw food. After the worm was removed from its patient, she was advised to drink only boiled water and not to eat unwashed raw vegetables [14].

The case reports record where patients lived and travelled. A woman in New York City who had the worm often travelled to Mississippi to visit relatives, so the authors could not say where she was infected [16]. A woman in Bulgaria had no history of travelling abroad and no contact with animals [17]. A man in France lived in a rural area of southern Alsace, had never been to Africa, and oversaw the unloading of flour at the port of Basel [18].

Symptoms

A 2021 review of the reported cases found that in people the worm is usually located in the mouth, and that the most common symptom is the sensation of a moving foreign body in the mouth [1]. Adult worms can live in the human body for up to 10 years and cause local irritation in the mouth, the throat (pharynx) and the gullet (esophagus) [14]. A 2012 report describes the worm's ability to settle in the submucosa, the layer of tissue just beneath the lining, of the mouth and of the oropharynx, the part of the throat behind the mouth [4].

Where in the mouth it has been found

What patients felt and saw

When the worm is in the gullet

Some reports describe the worm in the esophagus, the tube that carries food from the throat to the stomach. A 2020 report in a Chinese journal describes a woman with the worm in her esophagus [21], and a 2024 case report describes infection of the human esophagus [22]. A patient in southeast Georgia, in the United States, had intermittent yet persistent nausea and vomiting for months; the report's title describes the symptoms as esophageal [23]. A 2021 report describes a patient with the worm in the esophagus together with early esophageal cancer; it is discussed in the Nobel Prize section below [5].

How It Is Diagnosed

The diagnosis rests on finding the worm and identifying it. In several reports the worm was noticed and pulled out by the patients themselves [20][19][17]. It is then identified by its morphology, meaning its shape and structures under the microscope, and in more recent cases by genetic analysis as well [24][19][25].

Under the microscope

In the 2005 case, microscopy showed a gravid female, a female worm carrying eggs [20]. In the 2018 case, the worm was confirmed as the gullet worm by microscopic examination and analysis of its shape [14]. In animals, the genus can be recognised under a light microscope by its cuticular bosses, small raised knobs on the outer skin (cuticle) at the front of the worm [7].

Genetic analysis

Because Gongylonema species show few obvious differences in shape, genetic analysis helps tell them apart [2]. A worm taken from the mouth of a resident of Williamsburg, Virginia, reported in 2013, was identified both by its shape and by its genes. It was the thirteenth reported case of human Gongylonema infection in the United States, the first confirmed as Gongylonema pulchrum, and the first genetic confirmation of a Gongylonema worm in humans [24]. In Slovenia in 2019, the worm was confirmed under the microscope and by copying and reading (sequencing) a stretch of its DNA [19]. A 2025 report in a Chinese journal describes morphological and genetic testing of a worm found in the lining of the mouth [25].

Why it can be missed

A 2021 review notes that clinicians sometimes have difficulty with the diagnosis because they lack knowledge of and experience with this rare parasite [1]. The worm may also be out of sight when the patient is examined. In the French case, the first examination found nothing; the patient then photographed a filament in his cheek lining and finally extracted the worm. The author writes that the typical presentation makes the diagnosis easy, but that the possible absence of the parasite at the visit can lead to a misdiagnosis of Ekbom syndrome, or delusional parasitosis, a condition in which a person is firmly convinced they are infested when they are not [18]. In the 2005 case, several examinations had found nothing abnormal before the patient brought in a worm she had removed with her toothbrush [20].

Two of the reports end with a message for clinicians. The New York City report notes that, as cases of delusional parasitosis continue to increase, clinicians and laboratory staff need to be alert to the possibility that objects removed from the mouth are real parasites, and that such objects are worth examining before they are thrown away [16]. The 2005 report concludes that even very unusual symptoms that might suggest a delusion deserve careful clarification, in some cases with the help of a specialised institution or laboratory [20].

Treatment

There is no proven treatment approach yet. A 2021 review of the published cases found that surgical removal of the worm is thought to be the most effective treatment, and that after surgery albendazole, an anti-worm medicine, was given in almost all cases. The review notes that debate over the benefit of albendazole continues, while it is claimed that the drug controls the infection and prevents it from coming back [1].

Removing the worm

In several cases, removing the worm was the whole treatment. In the 2018 case, the patient's symptoms resolved immediately after the worm was surgically removed [14]. In the 2005 case, a careful search found a second worm on the other side of the mouth, which was removed through a small cut (incision); the patient then remained free of symptoms without any further therapy [20]. In the French case, no other treatment was judged necessary after the worm came out [18].

Albendazole after removal

In Bulgaria, albendazole was prescribed for three days after the patient removed the worm herself [17]. In the Georgia case, worms had to be extracted on two occasions, each time followed by a course of albendazole. The authors conclude that infections with a high worm burden may relapse after extraction and a short 3-day course of albendazole, and that longer courses may be indicated in selected circumstances [23].

A 2008 drug study in rabbits

A 2008 study tested four deworming drugs against the gullet worm, in the laboratory and in infected rabbits. Six groups of three rabbits were each infected with 30 third-stage larvae. Four months later, the groups were treated with thiabendazole for 3 days, mebendazole for 3 days, a single dose of levamisole, a single injection of ivermectin under the skin, or the drugs' inactive carriers alone, as a control. When the rabbits were examined 14 days after treatment, levamisole had reduced the number of worms by 63.2%, mebendazole by 22.8% and ivermectin by 25.8%; thiabendazole produced no reduction [13].

In every group, the surviving worms were found mainly in the gullet, with the rest in the lining of the cheek, the tongue and the lining of the throat. Female worms from the thiabendazole group carried a number of abnormally shaped eggs inside their reproductive tract [13].

In the laboratory part of the study, larvae were soaked in each drug and then given by mouth to mice, to see whether they could still invade the stomach lining. Only larvae exposed to high concentrations of levamisole became tightly coiled, with abnormal intestines, and no worms were recovered from mice given larvae from the two highest levamisole concentrations. The authors concluded that levamisole shows efficacy against gullet worm infection in living animals, and that the mouse test could be used to screen drugs for activity against such worms [13]. Albendazole, the drug given after surgery in almost all human cases, was not among the four drugs tested [13][1].

Treatment in animals

In the Madrid scops owls, treatment combined supportive care, daily removal of dead, cheese-like (caseous) material from the mouth, and a five-day course of the deworming drug fenbendazole. Approximately 60% of the affected owls that arrived at the rescue centre in 2011 were cured and released back into the wild [12].

Human Cases Around the World

Human infection is rare. A 2012 report of a healthy 26-year-old man counted approximately 50 human cases worldwide, 11 of them documented in the United States [4]. The cases below are described as their published abstracts report them.

United States

Europe

Asia

Gongylonema and the 1926 Nobel Prize

The genus has a place in the history of cancer research. The Danish pathologist Johannes Fibiger (1867–1928), professor of pathological anatomy from 1900, was awarded the Nobel Prize in medicine in 1926 for his work on the alleged cancer-causing role of a nematode, Gongylonema neoplasticum, in some species of rats. Later difficulties, including questions over which Gongylonema species were involved in the rats, the rats' diet and lack of vitamin A, and even the impossibility of reproducing his results, led to his work being contested [27]. A 1952 study of Gongylonema neoplasticum (also called Spiroptera neoplasticum) and vitamin A deficiency in the forestomach, the front part of the rat stomach, compared its findings with Fibiger's results [28].

Fibiger's worm is a different species from the gullet worm. Gongylonema neoplasticum, named by Fibiger and Ditlevsen in 1914, lives in the stomach lining of rats such as the brown rat (Rattus norvegicus) and the black rat (Rattus rattus). It is regarded as cosmopolitan, meaning found worldwide, in line with the spread of its rat hosts beyond Asia; these rats originated in southern Asia, and the worm is their native parasite. A 2018 study characterised the genes of the worm from 114 rats of seven species in Southeast Asia, selected from archived material from almost 4,500 rodents [8]. A 2016 study compared the DNA of two rodent Gongylonema species, including Fibiger's worm from a black rat on Okinawa Island, Japan, with that of the gullet worm. Their DNA was distinct: only two of the ribosomal gene regions compared (genes for part of the cell's protein-making machinery) were highly similar, at 97.2–98.7%, while the remaining sequences were less than 75% identical [2].

For the gullet worm itself, a 2021 case report states that, to date, there had been no reports on cancer-causing properties of Gongylonema pulchrum. The report described the first patient found with the worm in the esophagus together with early esophageal cancer, a squamous cell carcinoma (a cancer of the flat cells that line the esophagus). The patient had none of the high-risk factors for that cancer, such as smoking, flushing after drinking alcohol, or a history of tumours. The authors speculated about unknown links between the cancer and the infection in this patient, and offered the case as possible evidence for a new hypothesis of how tumours form [5].

The 1997 historical paper on the challenge to Fibiger's prize notes that the cancer-causing action of some parasitic worms, such as the blood fluke Schistosoma, is now recognised [27]. The full story of Fibiger's experiments, his Nobel lecture and the later reappraisal is told on the site's page Fibiger and the Parasite That Won a Nobel Prize.

A Worm Felt Moving in the Mouth

The feeling of something moving in the mouth is the symptom most often reported with the gullet worm [1]. In the cases from New York City, from the 2005 report and from France, the complaint was confirmed when a worm was removed and examined, and all three reports discuss how such complaints can be mistaken for delusional parasitosis [16][20][18]. The gullet worm is not the only living thing documented in the human mouth: fly larvae in the mouth (oral myiasis) are covered on the site's Oral Myiasis page, and an amoeba that lives around the gums on Entamoeba gingivalis: The Gum Amoeba. What people report about ivermectin, an anti-parasite medicine, and gum disease is gathered on Ivermectin for Gum Disease.

Key Research Papers

  1. Kurumanastırlı B, Yılmaz YA. Literature Review of Gongylonema pulchrum: A Rare Nematode. Turkiye Parazitol Derg. 2021;45(4):311-316. PubMed PMID: 34889200
  2. Setsuda A, Da N, Hasegawa H, Behnke JM, Rana HB, Dhakal IP, et al. Intraspecific and interspecific genetic variation of Gongylonema pulchrum and two rodent Gongylonema spp. (G. aegypti and G. neoplasticum), with the proposal of G. nepalensis n. sp. for the isolate in water buffaloes from Nepal. Parasitol Res. 2016;115(2):787-95. PubMed PMID: 26531300
  3. Setsuda A, Varcasia A, Scala A, Ozawa S, Yokoyama M, Torii H, et al. Gongylonema infection of wild mammals in Japan and Sardinia (Italy). J Helminthol. 2018;94:e13. PubMed PMID: 30457072
  4. Ayala MA, Yencha MW. Gongylonema: a parasitic nematode of the oral cavity. Arch Otolaryngol Head Neck Surg. 2012;138(11):1082-4. PubMed PMID: 23165385
  5. Zhou Q, Wei Y, Zhai H, Li S, Xu R, Li P. Comorbid early esophageal cancer and Gongylonema pulchrum infection: a case report. BMC Gastroenterol. 2021;21(1):305. PubMed PMID: 34332527
  6. Popovici DC, Marin AM, Ionescu O, Moraru MMF, Kaya DA, Imre M, et al. First Molecular Data of Gongylonema pulchrum (Rhabditida: Gongylonematidae) in European Fallow Deer Dama dama from Romania. Pathogens. 2024;13(2). PubMed PMID: 38392914
  7. Bandelj P, Žele Vengušt D, Vengušt G, Kušar D. Case report: First report of potentially zoonotic Gongylonema pulchrum in a free-living roe deer (Capreolus capreolus) in Slovenia. Front Vet Sci. 2024;11:1444614. PubMed PMID: 39132436
  8. Setsuda A, Ribas A, Chaisiri K, Morand S, Chou M, Malbas F, et al. Molecular genetic diversity of Gongylonema neoplasticum (Fibiger & Ditlevsen, 1914) (Spirurida: Gongylonematidae) from rodents in Southeast Asia. Syst Parasitol. 2018;95(2-3):235-247. PubMed PMID: 29446034
  9. Soares R, Bueno C, Vieira FM, Muniz-Pereira LC. Gongylonema sp. in the Tongue of a Brown-Nosed Coati (Nasua nasua) from the Brazilian Atlantic Forest. J Wildl Dis. 2023;59(3):528-531. PubMed PMID: 37170422
  10. Lopes F, Esperón F, Bravo-Barriga D, Frontera E, Cabrero-Sañudo FJ, Gil-Tapetado D, et al. Identification of the intermediate host of Gongylonema sp., the etiological agent of the necrotic oropharyngeal disease of the Scops owl (Otus scops). Parasitol Int. 2022;86:102443. PubMed PMID: 34461282
  11. Mukaratirwa S, Pillay E, Munsammy K. Experimental infection of selected arthropods with spirurid nematodes Spirocerca lupi Railliet & Henry, 1911 and Gongylonema ingluvicola Molin, 1857. J Helminthol. 2010;84(4):369-74. PubMed PMID: 20132587
  12. Esperón F, Martín MP, Lopes F, Orejas P, Carrero L, Muñoz MJ, et al. Gongylonema sp. infection in the scops owl (Otus scops). Parasitol Int. 2013;62(6):502-4. PubMed PMID: 23872068
  13. Kudo N, Kubota H, Gotoh H, Ishida H, Ikadai H, Oyamada T. Efficacy of thiabendazole, mebendazole, levamisole and ivermectin against gullet worm, Gongylonema pulchrum: in vitro and in vivo studies. Vet Parasitol. 2008;151(1):46-52. PubMed PMID: 18061354
  14. Xiaodan L, Zhensheng W, Ying H, Hongwei L, Jianqiu J, Peiru Z, et al. Gongylonema pulchrum infection in the human oral cavity: A case report and literature review. Oral Surg Oral Med Oral Pathol Oral Radiol. 2018;125(3):e49-e53. PubMed PMID: 29329982
  15. Wilson ME, Lorente CA, Allen JE, Eberhard ML. Gongylonema infection of the mouth in a resident of Cambridge, Massachusetts. Clin Infect Dis. 2001;32(9):1378-80. PubMed PMID: 11303277
  16. Eberhard ML, Busillo C. Human Gongylonema infection in a resident of New York City. Am J Trop Med Hyg. 1999;61(1):51-2. PubMed PMID: 10432055
  17. Vuchev D, Popova G, Tomova M. Human Infection with the Nematode Gongylonema sp.: A Case Report from Bulgaria. Iran J Parasitol. 2024;19(3):366-369. PubMed PMID: 39318818
  18. Battistelli-Lux C. [Buccal infection with Gongylonema pulchrum: an indigenous case in France]. Ann Dermatol Venereol. 2013;140(10):623-7. PubMed PMID: 24090893
  19. Kramar U, Skvarč M, Logar M, Islamović S, Kolenc M, Šoba B. First case of human Gongylonema pulchrum infection in Slovenia. J Helminthol. 2019;94:e62. PubMed PMID: 31328705
  20. Urch T, Albrecht BC, Büttner DW, Tannich E. [Human infection with Gongylonema pulchrum]. Dtsch Med Wochenschr. 2005;130(45):2566-8. PubMed PMID: 16273496
  21. Zhang QQ. [Human Gongylonema pulchrum infection in esophagus: a case report]. Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi. 2020;32(2):217-218. PubMed PMID: 32458617
  22. Li X, Yan C, Liu H, Zong L. Gongylonema pulchrum infection in human esophagus: A case report. Asian J Surg. 2024;47(1):734-735. PubMed PMID: 37914651
  23. Libertin CR, Reza M, Peterson JH, Lewis J, Hata DJ. Human Gongylonema pulchrum Infection: Esophageal Symptoms and Need for Prolonged Albendazole Therapy. Am J Trop Med Hyg. 2017;96(4):873-875. PubMed PMID: 28138043
  24. Allen JD, Esquela-Kerscher A. Gongylonema pulchrum infection in a resident of Williamsburg, Virginia, verified by genetic analysis. Am J Trop Med Hyg. 2013;89(4):755-7. PubMed PMID: 23958907
  25. Tang F, Sun X, Xu X, Mao F, Liu Y. [Human infection with Gongylonema pulchrum: a case report and review of relevant literature during the recent 10 years]. Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi. 2025;37(3):332-336. PubMed PMID: 40730534
  26. Wilde H, Suankratay C, Thongkam C, Chaiyabutr N, Chaiyabutr N. Human gongylonema infection in Southeast Asia. J Travel Med. 2001;8(4):204-6. PubMed PMID: 11703903
  27. Petithory JC, Théodoridès J, Brumpt L. [A challenged Nobel Prize: Johannes Fibiger, 1926]. Hist Sci Med. 1997;31(1):87-95. PubMed PMID: 11625107
  28. HITCHCOCK CR, BELL ET. Studies on the nematode parasite, Gongylonema neoplasticum (spiroptera neoplasticum), and avitaminosis A in the forestomach of rats: comparison with Fibiger's results. J Natl Cancer Inst. 1952;12(6):1345-87. PubMed PMID: 14939031

PubMed Topic Searches

  1. PubMed: Gongylonema pulchrum
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  3. PubMed: Gongylonema in the mouth
  4. PubMed: Gongylonema and albendazole
  5. PubMed: Gongylonema intermediate hosts
  6. PubMed: Gongylonema neoplasticum

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