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This genus is distinguished from the genera such as Syngamus in birds by the fact that they are found in mammals and that there are longitudinal ribs on the inner walls of the buccal capsule of those found in mammals. Cases in cats occur in the Caribbean; cases have not been reported from dogs. Human infections with Mammomonogamus have been ascribed to Mammomonogamus nasicola or Mammomonogamus laryngeus. Cases in cats have typically been ascribed to other species such as Mammomonogamus ierei. It is possible that Mammomonogamus ierei is a synonym of the ruminant parasites, Mammomonogamus nasicola and Mammomonogamus laryngeus.
The worms live in the nares and nasopharynx. The females are about 20 mm long; with the maximum length reported by Buckley being 23.8 mm. The males are 5 to 6.9 mm long and rather stocky in appearance. The worms are found with the bursa of the male attached at the level of the vulva of the female. There is a large buccal capsule that has eight large teeth at its base. The eggs of Mammomonogamus ierei were illustrated by Buckley as being ovoid with a shell that is clear and marked with fine irregular transverse striations. The eggs averaged 49.5 mm by 92 (84 - 100) mm. The eggs when passed in the feces are typically in a four to six celled stage. Cuadrado et al., reported that the eggs of Mammomonogamus were typically larger than those of Ancylostoma, had a thicker shell, and that the shell in a salt flotation preparation was typically found with attached debris.
There has not been a complete description of the life cycle of any of the species of Mammomonogamus. Species of the related avian genera, Cyathostoma and Syngamus, have been found to infect birds through the ingestion of their embryonated eggs, free larvae, or the ingestion of earthworm paratenic hosts. Attempts to infect sheep with earthworms infected with Mammomonogamus nasicola or with free larvae of this parasite failed to induce infections with this parasite. Human cases have been reported in the USA in individuals within a week after short trips to Jamaica , Martinique, and St. Lucia; this would indicate that the adults are capable of developing within a few days to two weeks.
No signs have been reported for infected cats. Cuadrado et al., report that histologically there is evidence of chronic inflammation of the nasopharynx. Humans with this infection have reported had non-productive and sometimes violent coughs. Humans have been treated with mebendazole.
Linguatula serrata (Arthropod)
The pentastomid parasites are now considered to actually represent a group of specialized crustacean-like arthropods. The adults have a worm-like body and a mouth with a pair of hooks on each side. The adults are all associated with the respiratory system of the final host, being found in the air sacks of birds, the lungs of reptiles, and the nasal turbinates of dogs. These are large parasites, the adult female is about 8 to 10 cm long and about 1 cm in diameter. The male is about 2 cm long. The body appears superficially annulated, and the worms tend to be tan to brown in color. Infected dogs have been reported from North Africa, the Middle East, Turkey, Greece, east-central Europe, Brazil, Chile, and Argentina, Tanzania, and even Australia. Diagnosis can be performed by finding the eggs which are yellowish oval objects, about 80 m, surrounded by a bladderlike envelope and containing a four-legged larva, in the nasal secretions or around the nares.
The life cycle of Linguatula serrata involves a required intermediate host. The eggs that are passed by the female contain a four-legged larvae. According to Hobmaier and Hobmaier, the eggs do not appear in the feces of the dog but instead are found in the nasal secretions. The possibility that the eggs are not shed in the feces should receive additional verification because in other hosts, the eggs are passed in the feces. If the egg is ingested by a mammalian intermediate host, e.g., rodent, ruminant, or primate, the larvae hatch, and migrate to the liver, lungs, lymph nodes, and peritoneal mesenteries where they develop into nymphs that can be several cm in length and which are encased in a host tissue reaction. It is suspected that most dogs obtain their infections by the ingestion of sheep offal. When dogs ingest infected tissues, the nymphs migrate up the back of the throat into the nasal turbinates. Once swallowed, the nymphs do not migrate back up the esophagus. The prepatent period is about six months, and it is believed that the adult worms live about two years.
The early signs of infection with Linguatula serrata are sneezing and slight nasal discharge. The parasites become large, lie in the recesses of the nasal turbinates, and attach themselves firmly to the mucous membranes with their four hook. The adults apparently feed on respiratory mucosal cells and blood. When fully grown, the parasites are capable of causing impairment of respiration. In more chronic infections, the nasal discharge will increase in volume, and there is the possibility of obstruction of the nasal passages. Humans have on rare occasions been host to the same stage that is found in the dog. Humans present with signs that would be suspected from a several cm long larva migrating from the mouth into the nasal sinuses, e.g., throat discomfort, coughing, sneezing, dysphagia, and vomiting.
Treatment of infections with Linguatula serrata is typically by the removal of the organisms from the sinuses by physical means. In reindeer, ivermectin has been shown to be effective in killing the deer-sinus pentastomid, Linguatula arctica.
Anisakis rarely reach full maturity in humans and usually are eliminated spontaneously from the digestive tract lumen within 3 weeks of infection. In cases where the patient vomits or coughs up the worm, the disease may be diagnosed by morphological examination of the nematode. (Ascaris lumbricoides, the large roundworm of humans, is a terrestrial relative of anisakines and sometimes these larvae also crawl up into the throat and nasal passages.
Causes, incidence, and risk factors
Ascariasis is the most common intestinal worm infection. It is found in association with poor personal hygiene, poor sanitation, and in places where human feces are used as fertilizer. Intake of food or drink contaminated with roundworm eggs causes infection.
The eggs hatch and release larvae within the intestine. The larvae then move through the bloodstream to the lungs, exit up through the large airways of the lungs, and are swallowed back into the stomach and intestines.
During movement through the lungs the larvae may produce an uncommon form of pneumonia called eosinophilic pneumonia. Once back in the intestines, they mature into adult roundworms. Adult worms live in the intestine where they lay eggs that are present in feces.
It is estimated that 1 billion people are infected worldwide. Ascariasis occurs in all ages, though children seem to be affected more severely than adults.
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