Mammomonogamus
Encyclopedia
Mammomonogamus is a genus
of parasitic nematode
of the family Syngamidae
that parasitises the respiratory tract of cattle
, sheep, goats, deer
, cat
s, orangutans, and elephant
s. The nematode can also infect humans and cause the disease called Mammomonogamiasis. There are several known species that fall under the Mammomonogamus genus, but the most common species found to infest humans is Mammomonogamus laryngeus. Infection in humans is very rare with only about 100 reported cases worldwide and assumed to be largely accidental. Cases have been reported from the Caribbean, China, Korea, Thailand, and Philippines. The worm usually inhabits the upper-respiratory region in the trachea
, bronchus
, or larynx
and can elicit chronic coughing and asthma
-like symptoms. One interesting case from Thailand reported finding worms in the patient's duodenum, suggesting that M. laryngeus can also be a gastrointestinal parasite. More research is needed because the life cycle is not completely known. Diagnosis is made by recovering the worms on bronchoscopy
or oesophagogastroduodenoscopy. Due to the scant amount of information available on this parasite in literature, increased awareness is necessary especially in endemic areas near M. laryngeus’ reservoir hosts in order to for clinicians, the local population in the endemic area, and traveling tourists to effectively recognize and prevent against Mammomonogamiasis.
Classification of Mammomonogamus falls under the Syngamidae family. Syngamidae is in the Strongyloidae superfamily and Strongylata order, making them close relatives to hookworms and other nematodes.
The genus name Mammomonogamus is derived from the Latin root “Mammo-” (breast) and the Greek roots “mono” (single) and “gamus” (marriage), which most likely is referring to the distinct characteristic of the male and female worm acting as a single unit through the male being joined in permanent copulation to the middle portion of the female’s body.
Species within this genus are Mammomonogamus laryngeus, Mammomonogamus nasicola, and Mammomonogamus gangguiensis. Only M. laryngeus is known to infect and cause disease in humans. Because of M. laryngeus’ close resemblance to the gapeworm
from the Syngamus genus that commonly infect birds, M. laryngeus was originally called Syngamus laryngeus and Syngamus kingi. The classification was revised in 1948 when Ryzhikov reconstructed the phylogenetic relationship of the Syngamidae family and re-categorized the parasite as M. laryngeus.
Infestation with M. laryngeus has been called Mammomonogamiasis, Mammomonogamosis, Syngamosis, or Syngamiasis
Adult M. laryngeus worms are red to reddish-brown in color due to their hemophagous nature. They possess spicules ranging from 23-30μm in length and cup-shaped buccal capsules (mouth) that open at the anterior end. Located deep in the buccal cavity are 8 to 10 teeth that are not thought to be used for attachment.
The adult male is about half the length of the female. Case reports have found male worms ranging from 3-6.3mm in length and 360-380μm in width. The larger females were reported to be 8.7-23.5mm long and 550-570μm wide. Females also have a pointed posterior end with long or short tails. The female while in copula lays many ellipsoid-shaped eggs that are about 40 x 80μm in size, non-operculated, and usually possess thicker shells than hookworm eggs.
Although the complete life cycle of M. laryngeus is not fully known due to the rareness of the parasite in humans, some have postulated that the parasite adopts a life cycle similar to Syngamus trachea, the common gapeworm infection in birds that was initially thought to be Mammomonogamiasis. Currently, there are two existing hypotheses that will help aid medical diagnostics, especially in endemic areas such as the tropics, Caribbean, and Brazil.
Hypothesis #1:
Infection initially begins by the ingestion of foods, water, or intermediate hosts contaminated by adult worms. The infective adults migrate to the larynx or trachea and attach to the mucosal walls. Sexual reproduction
occurs here, and the females begin to lay eggs in the upper respiratory region. Eggs do not develop at body temperature and are expelled in sputum
or re-swallowed and excreted in feces.
Hypothesis #2:
The infective agent may be embryonated eggs or infective larvae, and infection is due to ingestion of contaminated food, water, or intermediate hosts. As larvae are released into the intestinal area, they can burrow through intestinal walls, travel into the mesenteric vein
s, and migrate to the alveoli. Here, they undergo a pulmonary cycle, where the larvae develop into adult worms in a process that may take 7 days. After reaching adulthood, M. laryngeus migrates upwards to the trachea, larynx, or bronchi, where sexual reproduction occurs. Egg production begins approximately 3 weeks later, and eggs are coughed up and expelled in sputum or feces. Larvae may hatch from embryonated eggs outside of the mammalian host.
More research is needed to fully elucidate the life cycle, but it may appear that both larvae and adults can be infective. One recent case reported finding adult worms in the duodenum
, which is the first presentation of adult worms not in the upper respiratory region. It is possible that the adult worms might have been coughed up and re-swallowed before settling in the duodenum. The development from larvae to adult is about 3 weeks, but there is uncertainty regarding the existence of a larval pulmonary cycle. Intermediate hosts, although not fully known, may be earthworms (an intermediate host for the genus Syngamus, the parasite causing avian gapeworm), snails, or arthropods. Other than intermediate hosts, there has been no mention of other biological or mechanical vectors.
. Worms in the bronchial region can trigger a chronic, nonproductive cough and asthma-like symptoms due to the obstruction of airways by the worms. These symptoms along with a low-grade fever can last for several months if not initially diagnosed correctly. A scratching or crawling sensation can be felt in the throat if the worms are attached in the larynx. Weight loss and pneumonitis
have been reported as possible long-term consequences, but not anemia
.
Recently, M. laryngeus worms were found in the duodenum
of a Thai patient, which was the first gastrointestinal case of Mammomonogamiasis. The patient complained of chest pain, haematemesia, melaena, abdominal bloating, but no respiratory symptoms. Although nothing conclusive was determined, it is possible that the adult worms were dislodged from the larynx, re-swallowed, and later found in the duodenum.
The incubation period is usually 6–11 days after infection. This supports the second hypothesis of a possible pulmonary cycle that explains the one to two week delay in the presentation of symptoms.
Eosinophilia
count is not a reliable measure of extent of infection because it varies from individual to individual. Some cases with multiple pairs of worms have reported low eosinophils levels while other cases with a single pair had very high eosinophil count. Such variation may be due to the lack of host tissue invasion by the parasite, since M. laryngeus attaches to the mucosal epithelium
in the tracheolaryngeal region. A singular case even found worms within a cyst
.
Past cases have demonstrated that simple removal of the worms from upper-respiratory area led to a cessation of symptoms and was a sufficient cure with or without anti-helmintics. No lasting pathological tissue damage was reported.
Thus far, there has been no mention of a re-infection mechanism for M. laryngeus, so all adult worms found inside a human must be the result of an ingested embryonated egg, larvae, or adult worm. Most of the time, only one pair of worms is found, but occasionally, the patient may have multiple pairs that must all be removed.
, a bronchoscope, or endoscopic instruments. However, worms might be difficult to remove if firmly attached to the bronchial walls. M. laryngeus eggs found in the sputum or feces is another sure sign of infection.
The eggs closely resemble hookworm eggs, but Mammomonogamus eggs have a much thicker shell. Due to the individual variation on eosinophilia counts, this is not a reliable diagnostic tool.
, Mebendazole
or Thiabendazole
with no adverse effects. Patients given Albendazole were instructed to take 400 mg for 3 days or if given a combination of drugs, Albendazole is given 200 mg, 3x a day for 3 days with Mebendazole at 100 mg, 3x a day for 3 days. The drug regimens ranged from 200–3000 mg/day for 3–20 days.
While the complete life cycle is still not fully known, transmission is thought to be oral-fecal, where infection comes from ingesting contaminated food or water containing embryonated eggs, hatched larvae, or intermediate hosts. Possible intermediate host candidates include earthworms, snails, and arthropods. Eggs are expelled in sputum or feces. Most often, travelers to tropical climate places become exposed to contaminated sources and are diagnosed upon return to their country. The best preventative measure is to ensure proper food preparation and water sanitation.
From the numerous case reports, endemic areas include Martinique, Brazil, Puerto Rico, Dominica, Santa Lucia, Trinidad, Guyana, Guadeloupe, India, tropic regions in Africa, Malaysia, Philippines, Vietnam, China, Korea, and Thailand.
Due to the frequency of travelers contracting this disease, countries such as Australia, Canada, United States, UK, France have reported cases although these countries are not considered to be endemic for the parasite.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of parasitic nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
of the family Syngamidae
Syngamidae
Syngamidae is a family of nematodes which commonly parasitize mammals, birds, and rarely humans. They are classified in the Strongyloidae superfamily and Strongylata order ....
that parasitises the respiratory tract of cattle
Cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
, sheep, goats, deer
Deer
Deer are the ruminant mammals forming the family Cervidae. Species in the Cervidae family include white-tailed deer, elk, moose, red deer, reindeer, fallow deer, roe deer and chital. Male deer of all species and female reindeer grow and shed new antlers each year...
, cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
s, orangutans, and elephant
Elephant
Elephants are large land mammals in two extant genera of the family Elephantidae: Elephas and Loxodonta, with the third genus Mammuthus extinct...
s. The nematode can also infect humans and cause the disease called Mammomonogamiasis. There are several known species that fall under the Mammomonogamus genus, but the most common species found to infest humans is Mammomonogamus laryngeus. Infection in humans is very rare with only about 100 reported cases worldwide and assumed to be largely accidental. Cases have been reported from the Caribbean, China, Korea, Thailand, and Philippines. The worm usually inhabits the upper-respiratory region in the trachea
Vertebrate trachea
In tetrapod anatomy the trachea, or windpipe, is a tube that connects the pharynx or larynx to the lungs, allowing the passage of air. It is lined with pseudostratified ciliated columnar epithelium cells with goblet cells that produce mucus...
, bronchus
Bronchus
A bronchus is a passage of airway in the respiratory tract that conducts air into the lungs. The bronchus branches into smaller tubes, which in turn become bronchioles....
, or larynx
Larynx
The larynx , commonly called the voice box, is an organ in the neck of amphibians, reptiles and mammals involved in breathing, sound production, and protecting the trachea against food aspiration. It manipulates pitch and volume...
and can elicit chronic coughing and asthma
Asthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
-like symptoms. One interesting case from Thailand reported finding worms in the patient's duodenum, suggesting that M. laryngeus can also be a gastrointestinal parasite. More research is needed because the life cycle is not completely known. Diagnosis is made by recovering the worms on bronchoscopy
Bronchoscopy
Bronchoscopy is a technique of visualizing the inside of the airways for diagnostic and therapeutic purposes. An instrument is inserted into the airways, usually through the nose or mouth, or occasionally through a tracheostomy. This allows the practitioner to examine the patient's airways for...
or oesophagogastroduodenoscopy. Due to the scant amount of information available on this parasite in literature, increased awareness is necessary especially in endemic areas near M. laryngeus’ reservoir hosts in order to for clinicians, the local population in the endemic area, and traveling tourists to effectively recognize and prevent against Mammomonogamiasis.
Taxonomic classification
The genus name Mammomonogamus is derived from the Latin root “Mammo-” (breast) and the Greek roots “mono” (single) and “gamus” (marriage), which most likely is referring to the distinct characteristic of the male and female worm acting as a single unit through the male being joined in permanent copulation to the middle portion of the female’s body.
Species within this genus are Mammomonogamus laryngeus, Mammomonogamus nasicola, and Mammomonogamus gangguiensis. Only M. laryngeus is known to infect and cause disease in humans. Because of M. laryngeus’ close resemblance to the gapeworm
Gapeworm
A gapeworm is a parasitic nematode worm infecting the tracheas of certain birds. The resulting disease, known as gape or the gapes, occurs when the worms clog and obstruct the airway. The worms are also known as red worms or forked worms due to their red color and the permanent procreative...
from the Syngamus genus that commonly infect birds, M. laryngeus was originally called Syngamus laryngeus and Syngamus kingi. The classification was revised in 1948 when Ryzhikov reconstructed the phylogenetic relationship of the Syngamidae family and re-categorized the parasite as M. laryngeus.
Infestation with M. laryngeus has been called Mammomonogamiasis, Mammomonogamosis, Syngamosis, or Syngamiasis
History
The Mammomonogamus parasite of greatest significance to humans is M. laryngeus due to the occasional, incidental cases reported in humans. While M. laryngeus commonly infects domestic ungulates and ruminants, the first reported case of a human infection was by Dr. King who diagnosed the parasite in a woman from St. Lucia, Antilles. The next case originated in Brazil in the 1920s where the connection with bovine species was confirmed.Morphology
The most distinct feature of M. laryngeus is the “Y” shape that is formed when the male is joined to the female in copula. The smaller male uses its posterior bursa to attach to the female vulva located on the side near the middle of the female worm. The adult worms usually remain permanently joined in this “Y” formation as they settle on the mucosal epithelium of the larynx, trachea, or bronchi.Adult M. laryngeus worms are red to reddish-brown in color due to their hemophagous nature. They possess spicules ranging from 23-30μm in length and cup-shaped buccal capsules (mouth) that open at the anterior end. Located deep in the buccal cavity are 8 to 10 teeth that are not thought to be used for attachment.
The adult male is about half the length of the female. Case reports have found male worms ranging from 3-6.3mm in length and 360-380μm in width. The larger females were reported to be 8.7-23.5mm long and 550-570μm wide. Females also have a pointed posterior end with long or short tails. The female while in copula lays many ellipsoid-shaped eggs that are about 40 x 80μm in size, non-operculated, and usually possess thicker shells than hookworm eggs.
Life cycle
Hypothesis #1:
Infection initially begins by the ingestion of foods, water, or intermediate hosts contaminated by adult worms. The infective adults migrate to the larynx or trachea and attach to the mucosal walls. Sexual reproduction
Sexual reproduction
Sexual reproduction is the creation of a new organism by combining the genetic material of two organisms. There are two main processes during sexual reproduction; they are: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the...
occurs here, and the females begin to lay eggs in the upper respiratory region. Eggs do not develop at body temperature and are expelled in sputum
Sputum
Sputum is mucus that is coughed up from the lower airways. It is usually used for microbiological investigations of respiratory infections....
or re-swallowed and excreted in feces.
Hypothesis #2:
The infective agent may be embryonated eggs or infective larvae, and infection is due to ingestion of contaminated food, water, or intermediate hosts. As larvae are released into the intestinal area, they can burrow through intestinal walls, travel into the mesenteric vein
Mesenteric vein
Mesenteric vein can refer to:*Superior mesenteric vein*Inferior mesenteric vein...
s, and migrate to the alveoli. Here, they undergo a pulmonary cycle, where the larvae develop into adult worms in a process that may take 7 days. After reaching adulthood, M. laryngeus migrates upwards to the trachea, larynx, or bronchi, where sexual reproduction occurs. Egg production begins approximately 3 weeks later, and eggs are coughed up and expelled in sputum or feces. Larvae may hatch from embryonated eggs outside of the mammalian host.
More research is needed to fully elucidate the life cycle, but it may appear that both larvae and adults can be infective. One recent case reported finding adult worms in the duodenum
Duodenum
The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms anterior intestine or proximal intestine may be used instead of duodenum...
, which is the first presentation of adult worms not in the upper respiratory region. It is possible that the adult worms might have been coughed up and re-swallowed before settling in the duodenum. The development from larvae to adult is about 3 weeks, but there is uncertainty regarding the existence of a larval pulmonary cycle. Intermediate hosts, although not fully known, may be earthworms (an intermediate host for the genus Syngamus, the parasite causing avian gapeworm), snails, or arthropods. Other than intermediate hosts, there has been no mention of other biological or mechanical vectors.
Symptoms of infection in humans
Symptoms usually began to appear 6–11 days after initial infection, beginning with a fever and cough. Most cases reported a progression to a persistent cough, leading to expectoration and sometimes hemoptysisHemoptysis
Hemoptysis or haemoptysis is the expectoration of blood or of blood-stained sputum from the bronchi, larynx, trachea, or lungs Hemoptysis or haemoptysis is the expectoration (coughing up) of blood or of blood-stained sputum from the bronchi, larynx, trachea, or lungs Hemoptysis or haemoptysis ...
. Worms in the bronchial region can trigger a chronic, nonproductive cough and asthma-like symptoms due to the obstruction of airways by the worms. These symptoms along with a low-grade fever can last for several months if not initially diagnosed correctly. A scratching or crawling sensation can be felt in the throat if the worms are attached in the larynx. Weight loss and pneumonitis
Pneumonitis
Pneumonitis or pulmonitis is a general term that refers to inflammation of lung tissue.Pneumonia is pneumonitis combined with consolidation and exudation...
have been reported as possible long-term consequences, but not anemia
Anemia
Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...
.
Recently, M. laryngeus worms were found in the duodenum
Duodenum
The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms anterior intestine or proximal intestine may be used instead of duodenum...
of a Thai patient, which was the first gastrointestinal case of Mammomonogamiasis. The patient complained of chest pain, haematemesia, melaena, abdominal bloating, but no respiratory symptoms. Although nothing conclusive was determined, it is possible that the adult worms were dislodged from the larynx, re-swallowed, and later found in the duodenum.
Pathogenesis
Little is known about how M. laryngeus causes disease. Symptoms do not arise until the worms have reached the adult stage and obstruct the bronchial airways leading to asthma-like symptoms and coughing. Similar symptoms are seen in humans as well as the domestic ungulates and ruminant hosts. Bronchial inflammation or hemotypsis may occur due to the worms attaching to the mucosal walls and ingesting red blood cells.The incubation period is usually 6–11 days after infection. This supports the second hypothesis of a possible pulmonary cycle that explains the one to two week delay in the presentation of symptoms.
Eosinophilia
Eosinophilia
Eosinophilia is a condition in which the eosinophil count in the peripheral blood exceeds 0.45×109/L . A marked increase in non-blood tissue eosinophil count noticed upon histopathologic examination is diagnostic for tissue eosinophilia. Several causes are known, with the most common being...
count is not a reliable measure of extent of infection because it varies from individual to individual. Some cases with multiple pairs of worms have reported low eosinophils levels while other cases with a single pair had very high eosinophil count. Such variation may be due to the lack of host tissue invasion by the parasite, since M. laryngeus attaches to the mucosal epithelium
Epithelium
Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...
in the tracheolaryngeal region. A singular case even found worms within a cyst
Cyst
A cyst is a closed sac, having a distinct membrane and division on the nearby tissue. It may contain air, fluids, or semi-solid material. A collection of pus is called an abscess, not a cyst. Once formed, a cyst could go away on its own or may have to be removed through surgery.- Locations :* Acne...
.
Past cases have demonstrated that simple removal of the worms from upper-respiratory area led to a cessation of symptoms and was a sufficient cure with or without anti-helmintics. No lasting pathological tissue damage was reported.
Thus far, there has been no mention of a re-infection mechanism for M. laryngeus, so all adult worms found inside a human must be the result of an ingested embryonated egg, larvae, or adult worm. Most of the time, only one pair of worms is found, but occasionally, the patient may have multiple pairs that must all be removed.
Diagnosis
The definitive diagnosis is the obtainment of adult worms either by coughing them up or removing them with forcepsForceps
Forceps or forcipes are a handheld, hinged instrument used for grasping and holding objects. Forceps are used when fingers are too large to grasp small objects or when many objects need to be held at one time while the hands are used to perform a task. The term 'forceps' is used almost exclusively...
, a bronchoscope, or endoscopic instruments. However, worms might be difficult to remove if firmly attached to the bronchial walls. M. laryngeus eggs found in the sputum or feces is another sure sign of infection.
The eggs closely resemble hookworm eggs, but Mammomonogamus eggs have a much thicker shell. Due to the individual variation on eosinophilia counts, this is not a reliable diagnostic tool.
Treatment
Mammomonogamiasis is relatively easy to treat. Manual or bronchoscopic removal of worms has been successful. One case followed up with aspiration. Although no controlled study on the efficacy of anti-helmintics in treating Mammomonogamiasis has been conducted, most patients were given AlbendazoleAlbendazole
Albendazole, marketed as Albenza, Eskazole, Zentel and Andazol, is a member of the benzimidazole compounds used as a drug indicated for the treatment of a variety of worm infestations. Although this use is widespread in the United States, the U.S. Food and Drug Administration has not approved...
, Mebendazole
Mebendazole
Mebendazole or MBZ is a benzimidazole drug developed by Janssen Pharmaceutica and marketed as Vermox, Ovex, Antiox, and Pripsen...
or Thiabendazole
Thiabendazole
Tiabendazole is a fungicide and parasiticide.-Fungicide:...
with no adverse effects. Patients given Albendazole were instructed to take 400 mg for 3 days or if given a combination of drugs, Albendazole is given 200 mg, 3x a day for 3 days with Mebendazole at 100 mg, 3x a day for 3 days. The drug regimens ranged from 200–3000 mg/day for 3–20 days.
Epidemiology
Mammomonogamiasis is a very rare human infection yet a common veterinary parasite. Only 100 human cases of M. laryngeus have been reported thus far. Its reservoir hosts are largely in tropical regions, most commonly the domestic cattle, cats, orangutans, and other ruminants and ungulates. Therefore, humans are accidental hosts, where infections are most likely to due close exposure to bovine or feline species.While the complete life cycle is still not fully known, transmission is thought to be oral-fecal, where infection comes from ingesting contaminated food or water containing embryonated eggs, hatched larvae, or intermediate hosts. Possible intermediate host candidates include earthworms, snails, and arthropods. Eggs are expelled in sputum or feces. Most often, travelers to tropical climate places become exposed to contaminated sources and are diagnosed upon return to their country. The best preventative measure is to ensure proper food preparation and water sanitation.
From the numerous case reports, endemic areas include Martinique, Brazil, Puerto Rico, Dominica, Santa Lucia, Trinidad, Guyana, Guadeloupe, India, tropic regions in Africa, Malaysia, Philippines, Vietnam, China, Korea, and Thailand.
Due to the frequency of travelers contracting this disease, countries such as Australia, Canada, United States, UK, France have reported cases although these countries are not considered to be endemic for the parasite.
Public health
Mammomonogamiasis is not considered an emerging disease because of the rarity of cases. Consequently, there are no control measures currently being implemented. Very little information about this disease can be found in literature, so physicians especially in endemic areas should be aware of the parasitic disease, the clinical presentations, and treatment for humans.External links
- Information from the Centers for Disease Control and PreventionCenters for Disease Control and PreventionThe Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...
.