Parasites and Pestilence
Gongylonema pulchrum infections are due to humans acting as accidental hosts for the parasite. There are seven genera of spirudia nematodes that infect human hosts accidentally: gnoathostoma, thelazia, gonyglonema, physaloptera, spirocerca, rictularia. The g. pulchrum parasite is a nematode worm of the order Spirudia. It is a relatively thin nematode, and like other worms within its class, it has no circulatory or respiratory system. In the Gongylonema family, it is the only species that can infect humans. Most other gongylonema species infect birds and mammals: there are 25 species found in mammals and 10 species found in birds. (GIDEON)
History of Discovery
Gongylonema pulchrum was first named and presented with its own species by Molin in 1857. The first reported case was in 1850 by Dr. Joseph Leidy, when he identified a worm “obtained from the mouth of a child” from the Philadelphia Academy. He originally described it as Filariae hominis oris, and initially considered the worm was a guinea worm (Dracunculiasis medeninsis), but because of the unique location of the worm (buccal cavity), and the relatively short size compared to the guinea worm, the hypothesis was disregarded. There have only been around 50 reported human cases of g. pulchrum world wide since 1864, and these infections have been widespread and globally ubiquitous. G. pulchrum infections have been notoriously and historically hard to diagnose due to symptom complaints by patients- this will be touched on later. Also, morphological diagnosis of the parasite is also somewhat complicated because of the variable size of adult worms, and the tendency of the worm to be different lengths depending on what host the worm is recovered from. This will also be discussed in the morphology section. (Ward)
Transmission to humans is due mostly to unsanitary conditions and the ingestion of infected coprophagous insects, mostly dung beetles and cockroaches. Beyond direct ingestion of infected intermediate hosts (insects), foods can become contaminated if unsanitary conditions pervade in the production of the food- coprophagous insects are found in the food, or in the production chain. Also, contaminated water sources, again with the intermediate hosts or the infective third stage larva, can lead to transmission to humans. (GIDEON, Garcia)
Reservoir and Vector
Gongylonema pulchrum, along with most
other gongylonema nematodes, has a broad natural host range. This includes
hedgehogs, cattle, dogs, cats, ruminants, rabbits, and skunks. The vector and
intermediate host for gongylonema pulchrum infections are coprophagous insects
(dung beetles and cockroaches). (Garcia)
In humans, there can be an up to six week incubation period for worm development and symptoms may not appear until the second molting of the worm, in which the young adult worms begin migration to from the esophagus to the buccal and oral palate tissue. It is this movement through the mucosa of the mouth and lips that causes patients to complain of symptoms. (Wilson, Kudo, Ward)
The morphology of the worm is as follows, from a 2000 Veterinary Medicine study:
“The anterior end in both sexes was covered by numerous cuticular platelets. There was a pair of lateral cervical papillae. The buccal opening was small and extended in the dorsoventral direction. Around the mouth a cuticular elevation enclosed the labia, and eight papillae were located laterodorsally and lateroventrally. Two large lateral amphids were seen. On the lateral sides of the female's tail, phasmidal apertures were observed. The caudal end of the male was asymmetrically alate and bore 10 pairs of papillae and two phasmidal apertures.” (Naem)
The average length for male worms is 29.1 mm, while the average length for adult females is 58.7 mm. The worm is highly mobile, as observed in patients’ mouths and as evidenced by the morphological design of the worm. (Kirkpatrick, Ward, Lichtenfels)
Fig. 1. Scanning electron micrograph of the anterior end of an adult Gongylonema pulchrum showing the
zigzag pattern of the adult worm. Bar, 400 mm.
Fig. 2. Scanning electron micrograph of the anterior end of an adult Gongylonema pulchrum. An en face view
of the female cephalic region showing small mouth, with funnel-shaped rim lined by an inner circle of two
distinct lateral lips with three lobes each (black arrowheads); there are papillae (black arrows), an amphidal
aperture (A), and semilunar depressions (stars). Bar, 9 mm.
Fig. 3. Scanning electron micrograph of the anterior end of an adult male Gongylonema pulchrum showing
numerous bosses on the surface. There are hat-like cervical papilla (arrowhead) and lateral alae (arrow).
Bar, 63.3 mm.
Fig. 4. Scanning electron micrograph of the anterior end of an adult Gongylonema pulchrum showing a higher
magnification of the hat-like cervical papilla. Bar, 4 mm.
Fig. 5. Scanning electron micrograph of the anterior end of an adult Gongylonema pulchrum showing the
button-like cervical papilla (arrow), lateral alae (LC) and cuticular bosses (B). Bar, 16.7 mm.
Fig. 6. Scanning electron micrograph of the anterior end of an adult Gongylonema pulchrum showing a higher
magnification of the button-like cervical papilla with cilia. Bar, 2 mm.
FIGURE 1. Photomicrographs of Gongylonema sp. removed from
the oral cavity of a patient in New York City. A, anterior end of the
worm showing characteristic cuticular bosses (magnification 3 77).
B, posterior end of the worm showing typical shape of tail, and
illustrating that the posterior end of the worm is appreciably greater
in diameter than the anterior end (magnification 3 77). C, higher
magnification of eggs in utero showing larvae inside the eggs (magnification
- In humans, the hypothesized lifecycle is as follows: Ingestion of contaminated food, water, or infected dung beetle. Infects upper esophagus, moves around and lays eggs in buccal cavity of human host, ingested eggs locate near esophagus, develop and mature into adult worms after two subsequent molting stages, migrate into buccal cavity, no eggs are ever found in human feces, which strengthens the assumption that humans are solely incidental, accidental, and dead end hosts for the gongylonema pulchrum parasite life cycle. (Wilson, Kudo)
-The pulchrum parasite has also been studied in vivo in rabbits. The lifecycle is as follows:
- Infective third stage larva from naturally infected dung beetles (intermediate hosts and vectors), were orally given to rabbits. The larvae entered the upper gastrointestinal tract of the rabbits (esophagus and upper stomach), and then migrated upward into the buccal cavity- pharyngeal mucosa and tongue. A third molt took place 11 days after primary infection, and the final molt took place at 36 days after primary infection. Worms reached sexual maturity at about 8 weeks, and were found mostly in the esophagus of the rabbit. 72-81 days post primary infection, embryonated eggs appeared in the feces of the rabbits. (Kudo)
- With initial infection, some patients have reported remembering a mild fever and flu-like symptoms about a month previous to extraction or identification of worm. The most common symptom is the complaint of sensation of a worm moving around the mouth, near the lips, and in the soft palate area. This movement is normally engendered by immature adult female worms. Symptoms, once noted, may continue from a month to a year if the worm is not surgically extracted. Eosinophilia is noted in some patients. (Haruiki)
-There is a danger of misdiagnosing infections of gongylonema pulchrum as delusional parasitosis. Diagnosis is often made by visible recognition of the worm moving through the tissue of the buccal cavity by either patient or doctor. Also, recovery of worm from patient is also a diagnostic technique. Microscopic identification of worm removed from patient’s mouth or tissue is another diagnostic technique for determining the parasite infection type. (Garcia)
- Treatment for infections with gongylonema
pulchrum include surgical/manual extraction and dosage of albendazole (400 mg
BID (twice daily) X 21 days).
Follow up measures include periodic of checks of buccal cavity and
esophagus to ensure parasite infection has cleared. (Garcia, GIDEON)
- Infections of gongylonema pulchrum are not a huge public health concern. There have only been 50 recorded infections world wide since the first reported case in 1850. The infections of g. pulchrum have been widespread, and countries reporting human infections include the United States, Germany, Iran, Japan, Laos, Morocco, China, Italy, New Zealand, and Egypt, among others. Control measures for reducing infections include making sure vector and larval contamination of food and water sources does not occur- this could be included in basic sanitary practices. Another control measure is ensuring children and adults do not accidentally or purposefully ingest infected dung beetles and other coprophagous insects. (GIDEON, Garcia, Kudo)
Individual Case Studies
- In 1996, the first reported case of gongylonema pulchrum infection was reported in Japan. A 34-year old male complaining of irritable stomatitis on his lower lip went in to see his doctor, but the pain subsided spontaneously. However, it reoccurred several times in the next few months. When he went in to his doctor after one of these episodes, a thread like organism was seen protruding from his ulcer. The patient also had eosinophilia, but the ulcer healed with no scar once the organism was removed. The organism was identified as a female gongylonema pulchrum worm, and the patient needed no further treatment.
How the patient contracted the worm is still unknown. He didn’t report eating any abnormal foods, nor had he traveled outside of Japan in the past few years. He also did not report drinking any water from possibly infected wells. It is possible that he ate food that had been contaminated in an endemic country and shipped to Japan. With the globalized food market now present, this is not out of the realm of possibility, and should be considered as a possible means of transmission into countries that have no previous history of g. pulchrum infection. (Haruki)
-In 1999, a 41 year old female resident of New York City went in to her doctor complaining of the sensation of something moving in her mouth. She said she had had the feeling for the duration of one year. Supposedly, she had removed worms from her mouth on two separate occasions- one from her lip, and one from her gums. She submitted one of the specimens for microscopic identification, and it was found to be an adult female gongylonema pulchrum worm. She traveled frequently to visit relatives in Mississippi, so it is unknown whether she contracted the worm in New York or in the south. This was the first reported case of gongylonema in the United States since 1963.(Eberhard)
-Also in 1999, a 38-year old woman of Cambridge, Massachusetts sought medical attention for the visible identification of a “migrating mass” in her cheek mucosa. Six months earlier, she had noted an irregular patch of mucosa on her cheek, but thought nothing of it. Previously in the year, she’d traveled to Mexico, Guatemala, and France. She didn’t report ingesting any beetles, but she did eat raw foods when vacationing in Mexico. She described the foods as “raw, crunchy, and saladlike”. Approximately 12 hours after eating the food, she and five other individuals she was traveling with had an acute attack of nausea, vomiting, and dizziness. The symptoms seemed to resolve themselves with no need of further treatment.
A small female gongylonema worm was surgically removed from her cheek mucosa under local anesthesia, and follow up treatment included albendazole two times daily for three days. This was the eleventh reported case of g. pulchrum infection in the United States. Most cases reported in the US are reported from the southeastern part of the country. (Wilson)
-There was a 1916 infection reported in a 16 year old girl from Mississippi. She presented with gastrointestinal pain, vomiting and a low fever (101.5). She complained of a sensation of a worm moving around her lower lip, but was disregarded by her physician. As she continued to complain, the physician examined her mouth, and discovered the outline of a worm. He extracted the worm with a sewing needle, and the child’s complaints stopped and she appeared to have no further symptoms of parasite infection. (Ward)
Sources to be added to the Wiki page:
1. “Gongylonema”. GIDEON Infectious Diseases. 1994-2010. http://web.gideononline.com/web/epidemiology/index.php?disease=10995&country=&view=General
2. Ward, Henry B. “Gongylonema in the Role of a Human Parasite”. The Journal of Parasitology. Vol 2, No. 3. Published by American Society of Parasitologists. March 1916. Pages 119-125.
3. Garcia, Lynn Shore. “Gongylonema”. Diagnostic Medical Parasitology. Fourth edition. 2001.
4. Haruki, K, et al. “Gongylonema Infection in Man: A first case of gongylonemosis in Japan”. Helminthologia. 42.2. 63-66. 2005.
5. Kudo, N, et al. “Further Observations on the Development of Gongylonema pulchrum in Rabbits”. Journal of Parasitology. 91(4): 750-755. 2005
6. Wilson, M, et al. “Gongylonema Infection of the Mouth in a Resident of Cambridge Massachusetts”. CID 2001: 32. May 1.
7. Lichtenfels, JR. “Morphological variation in the gullet nematode, Gongylonema pulchrum Molin, 1857, from eight species of definitive hosts with a consideration of Gongylonema from Macaca spp.” Journal of Parasitology. 57. P. 348-355. 1971.
8. Eberhard, ML and Busillo, C. “Human Gongylonema infection in a resident of New York City”. American Journal of Tropical Medicine and Hygiene. Vol 61, Issue 1. 51-52. 1999.
9. Naem, S, et al. “Scanning Electron Microscopy of Adult Gongylonema pulchrum”. Journal of Veterinary Medicine. 47, 2000. 249-255. 2000.
10. Kirkpatrick, CE, et al. “Gongylonema pulchrum Molin in Black Bears from Pennsylvania”. Journal of Wildlife Diseases. 22(1). 119-121. 1986.