Mel Abreu

Parasite and Pestilence: Infectious Public Health Challenges

Stanford Human Biology




Agent / Synonyms / History / Clinical Presentations / Transmission / Reservoir / Vector / Incubation period/ Morphology/ Diagnostic Test/ Therapy/ Epidemiology/ Country Information/ References


This parasite is not common in humans as only about 90 cases have ever been reported (Muller, 142).  Humans are accidental hosts and very little is known about the parasite in humans, or the parasite in general. It doesn’t seem to have caused any fatalities. The main targets of these parasites include mammals such as cattle and perhaps cats, but mainly infects birds. These worms suck blood from its host, usually preferring to do this in the larynx and other air passages. It’s thought that the worms travel in the blood to the lungs and then up to the larynx. According to the IVIS website article, no one has outlined the complete life cycle nor is the exact mode of transmission known. Conflicting information has been given by various sources. Since no very little is known, exact information is somewhat unavailable.


Disease Name: Mammomonogamiasis or Mammomonogamiosis. In 2000, a switch was made from syngamiasis to mammomonogamiasis (Gideon). This disease is also called gapeworm when it occurs in birds.


Agent: Phylum Nematoda,  Family Syngamidae, Mammomonogamus laryngeus or M. nasicola

Synonyms: Syngamus laryngeus, Syngamus kingi (although now a term used just for the parasite that infects birds) (Muller, 142).

History: According to Muller, the name originates from two men, one French, Railliet and one Russian, Ryzhikov.  Both wrote books describing parasitic infections in humans; Railliet’s book in 1899 and Ryzhikov’s in 1948. Very little information was offered for further explanation of the history of Mammomonogamus. More information is known about the infection in birds, so literature regarding birds can be used to better understand the general background of the nematode.


Clinical Presentation in Humans: Irritated throat, dry cough, headache, nausea, high eosinophil count.


Transmission: It’s thought that a mammal’s fecal matter filled with eggs in soil gets onto crops and then puts the worm on fruits and vegetables, and humans ingest the parasite. Researchers have been unable to successfully transmit the parasite to mammal test subjects. How transmission actually works is unknown.



Reservoir: Hosts usually are mammals such as cattle; human infection is purely accidental.


Vector: No vector exists. The exact mode of transmission is still questionable as well as all of the players. It’s most likely that no vector exists.


Incubation Period: According to Muller, incubation is about 25-40 days. According to Bowman, it may take a few days or up to 2 weeks.


Morphology: Mammomonogus are unsegmented worms, bilaterally symmetrically. The female and male usually attached, with the female being larger than the male (20mm to 4mm respectfully). The trademark of this parasite is the attachment and “Y” shape. The males have been described as being quite fat.  The male is attached to the vulva of the female. The parasite has a sizeable buccal capsule to suck blood and eight big teeth to attach itself to the host. The buccal capsule of the parasite that infects mammals versus birds seems to have “ribs” to perhaps strengthen the buccal capsule in attaching to the host.


Diagnostic test: Worms can be coughed up or seen visibly in the larynx. The characteristic Y shape should be a key indicator that it is this specific family of nematodes. A stool sample may show the presence of the egg with a sheer boundary and “marked with fine irregular transverse striations” (Bowman). Each egg measures 80 by 45 μm in diameter. The eggs are usually made up of 4-6 cells at the time of passage.


Therapy: Muller suggests that Mebendazole or Abendazole treatments should work. Additionally, removal of the worms is also a possibility.


Epidemiology /Geography: Only 92 cases reported, mainly in South America, but some single cases in China, Thailand, and the West Indies (Muller 142). Cases reported in the US have occurred in individuals that recently traveled to the Caribbean.

Countries affected: Mainly South America, namely Brazil. Also, the Caribbean seems to also have this parasite, but perhaps more common in animals and less affecting people. According to Markell et al, Mammomonogamiasis has also occurred in Australia.


Prevention: Since so little is known about the parasite, no definite method of prevention is outlined.


Scanty Life Cycle:




Useful Websites:


International Veterinary Information Service:




Bowman, D.D. “Respiratory System Parasites of the Dog and Cat (Part I): Nasal Mucosa and

Sinuses, and Respiratory Parenchyma.” International Veterinary Information Service.

< advances/Parasit_Bowman/ddb_resp/ivis.pdf>. Accessed 30 April



“Gideon Update 2000.4.” <>. Accessed 26 April 2002.


Markell, Edward K., John, David T., Krotoski, Wojciech A. Markell and Voge’s Medical Parasitology. 8th ed. Philadelphia: W.B. Saunders Company, 1999.


Muller, Ralph. Worms & Human Disease. CABI Publishing, 2001. pp. 142-43.