''Capillaria philippinensis'' is a
parasitic
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has c ...
nematode
The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...
which causes intestinal
capillariasis
Capillariasis is a disease caused by nematodes in the genus ''Capillaria''.Berger SA, Marr JS. Human Parasitic Diseases Sourcebook. Jones and Bartlett Publishers: Sudbury, Massachusetts, 2006. The two principal forms of the disease are:
* Intestina ...
. This sometimes fatal disease was first discovered in Northern
Luzon
Luzon (; ) is the largest and most populous island in the Philippines. Located in the northern portion of the Philippines archipelago, it is the economic and political center of the nation, being home to the country's capital city, Manila, as ...
, Philippines, in 1964. Cases have also been reported from China, Egypt, Indonesia, Iran, Japan, Korea, Lao PDR, Taiwan and Thailand.
[ ] Cases diagnosed in Italy and Spain were believed to be acquired abroad, with one case possibly contracted in Colombia. The natural life cycle of ''C. philippinensis'' is believed to involve fish as
intermediate hosts
In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include a ...
, and fish-eating birds as definitive hosts. Humans acquire ''C. philippinensis'' by eating small species of infested fish whole and raw.
Discovery and nomenclature
Between the first case reported in 1964 and the end of 1967, more than 1000 cases were documented in and around Northern Luzon particularly at Tagudin, Ilocos Sur, including 77 deaths.
Witch doctor
A witch doctor (also spelled witch-doctor) was originally a type of Folk healer, healer who treated ailments believed to be caused by witchcraft. The term is now more commonly used to refer to Alternative medicine, healers, particularly in region ...
s were hired by the locals to
exorcise
Exorcism () is the religious or spiritual practice of evicting demons, jinns, or other malevolent spiritual entities from a person, or an area, that is believed to be possessed. Depending on the spiritual beliefs of the exorcist, this may be ...
the curse placed on them by the river god, which they believed was responsible for this sudden disaster.
In 1968, the cause was identified as ''Capillaria philippinensis''. Adult ''C. philippinensis'' are very small, with males measuring 1.5–3.9 mm long and 23–28 µm maximum width, while adult females are 2.3–5.3 mm long and 29–47 µm maximum width. Eggs measure 36–45 µm long and 20 µm wide, and are described as peanut-shaped with a striated shell.
This species has been transferred to the genus ''Aonchotheca'', as ''Aonchotheca philippinensis'', and to the genus ''Paracapillaria'', as ''Paracapillaria philippinensis''. However, this species is almost universally referred to as ''Capillaria philippinensis'' in the current medical literature.
Hosts and life cycle
The complete life cycle of ''C. philippinensis'' has been demonstrated in experimental studies, and may be either indirect (involving an intermediate host) or direct (complete in one host).
Indirect life cycle. Fish-eating birds which harbor adult ''C. philippinensis'' in their
intestine
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans ...
s, shed embryonated eggs in their feces. When these eggs are fed to uninfected fish, ''C. philippinensis'' larvae are recovered from the intestines of fish. If the fish are fed to uninfested birds, the larvae develop into adults in the intestinal tract of the birds. Larvae recovered from the fish also developed into adults when fed to
gerbil
The Mongolian gerbil or Mongolian jird (''Meriones unguiculatus'') is a small rodent belonging to the subfamily Gerbillinae. Their body size is typically , with a tail, and body weight , with adult males larger than females. The animal is use ...
s or
monkey
Monkey is a common name that may refer to most mammals of the infraorder Simiiformes, also known as the simians. Traditionally, all animals in the group now known as simians are counted as monkeys except the apes, which constitutes an incomple ...
s, with eggs shed in the feces of these
mammal
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
ian hosts. Naturally infested fish (''Hypseleotris bipartita'' and ''Apagon'' sp.) and birds (''
Ixobrychus
''Ixobrychus'' is a genus of bitterns, a group of wading bird in the heron family Ardeidae.
It has a single representative species in each of North America, South America, Eurasia, and Australasia. The tropical species are largely resident, but t ...
'' sp.) have also been found. Humans become infested when they eat raw or undercooked fish, probably small fish eaten whole, which have the infective larvae in their intestinal tract. Raw fish are commonly eaten by several of the Asian cultures in which ''C. philippinensis'' infestations have been found.
While the natural host range is not known, experimental infestations of several fishes, including ''
Cyprinus carpio
The Eurasian carp or European carp (''Cyprinus carpio''), widely known as the common carp, is a widespread freshwater fish of eutrophic waters in lakes and large rivers in Europe and Asia.Fishbase''Cyprinus carpio'' Linnaeus, 1758/ref>Arkive The ...
'', ''Puntius gonionotus'', ''
Rasbora borapetensis
The blackline rasbora (''Rasbora borapetensis'') is a fish of the family Cyprinidae found in Asia in the Mekong, Chao Phraya, and Mae Klong basins, and also the northern Malay Peninsula. In the aquarium trade, it is known by a variety of other ...
'', ''
Eleotris melanosoma
''Eleotris melanosoma'', the broadhead sleeper or dusky sleeper, is a species of fish in the family Eleotridae native to marine, fresh, and brackish waters from coastal eastern Africa through southern Asia to the islands of the western Pacific O ...
'', ''
Ambassis
''Ambassis'' is a genus of fish in the family Ambassidae, the Asiatic glassfishes. They are found widely in the Indo-Pacific region, with species in fresh, brackish and coastal marine waters.
This genus includes fish known commonly as glassies ...
commersoni'' and ''
Apogon
''Apogon'' is a large genus of fish in the family ''Apogonidae'', the cardinalfishes. They are among the most common fish on coral reefs. Over 200 species have been classified in genus ''Apogon'' as members of several subgenera. Some of these sub ...
'' sp., with ''C. philippinensis'' eggs yielded infective larvae. Experimental infestations with larvae of several birds, including ''
Amaurornis phoenicurus
The white-breasted waterhen (''Amaurornis phoenicurus'') is a waterbird of the rail and crake family, Rallidae, that is widely distributed across South and Southeast Asia. They are dark slaty birds with a clean white face, breast and belly. They ...
'', ''
Ardeola bacchus'', ''
Nycticorax nycticorax
The black-crowned night heron (''Nycticorax nycticorax''), or black-capped night heron, commonly shortened to just night heron in Eurasia, is a medium-sized heron found throughout a large part of the world, including parts of Europe, Asia, and N ...
'', ''
Bubulcus ibis
The western cattle egret (''Bubulcus ibis'') is a species of heron (family Ardeidae) found in the tropics, subtropics and warm temperate zones. Most taxonomic authorities lump this species and the eastern cattle egret together (called the catt ...
'', ''
Ixobrychus sinensis
The yellow bittern (''Ixobrychus sinensis'') is a small bittern. It is of Old World origins, breeding in the northern Indian Subcontinent, east to the Russian Far East, Japan and Indonesia. It is mainly resident, but some northern birds migrate ...
'', ''
Gallinula chloropus
The common moorhen (''Gallinula chloropus''), also known as the waterhen or swamp chicken, is a bird species in the rail family (Rallidae). It is distributed across many parts of the Old World.
The common moorhen lives around well-vegetated mar ...
'', and ''
Rostratula benghalensis
The greater painted-snipe (''Rostratula benghalensis'') is a species of wader in the family Rostratulidae. It is found in marshes in Africa, South Asia and South-east Asia.
Description
Medium-sized, plump wading bird. Long reddish-brown bill, ...
'', yielded mature adults.
Direct life cycle. Researchers also found that feeding just a few dozen larvae from the intestines of fish to Mongolian gerbils (''
Meriones unguiculatus'') or monkeys (''
Macaca'' sp.) led to infestations with thousands of adult worms through "
autoinfection". Autoinfection is when the offspring produced by adults can reinfest the same host, allowing the infestation to multiply within a single host animal. Both
oviparous
Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, most reptiles, and all pterosaurs, dinosaurs (including birds), and ...
(egg-laying) and larviparous (giving birth to active larvae) adult female ''C. philippinensis'' were found in Mongolian gerbils and some birds. The experimentally infested monkeys never developed any clinical symptoms, even during prolonged, active infestations. Of several rodents tested, only Mongolian gerbils developed severe symptoms due to infestation and died.
Pathology
Although ''C. philippinensis'' infections are rare, it can serve as an indicator that one is being exposed to raw or undercooked fish. Early diagnosis of the parasite is beneficial so the number of worms in an infected person would not increase.
Worms create infection by penetrating the mucosa of the small intestine and reentering the lumen. As they progress into the body, they cause the mucosa and submucosa to degenerate. Infected people can have abdominal pains, diarrhea, weight loss, weakness, malaise, anorexia, and emaciation. They also experience loss of proteins and electrolytes and malabsorption of fats and sugars. If symptoms and the number of worms increase, it can eventually lead to death.
Diagnosis
This parasite can be diagnosed by taking a tissue
biopsy
A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, or an interventional cardiologist. The process involves extraction of sample cells or tissues for examination to determine the presence or extent of a diseas ...
from the small intestine or by examining stool samples through a microscope. In a heavily infected person, it is best to examine their feces because it will show an abundance of adult worms and eggs. When looking at the eggs of ''C. philippinensis'', one must be able to distinguish it from the eggs of ''Trichuris trichiura''. ''C. philippinensis'' eggs have nonprotruding polar plugs and are slightly smaller than ''T. trichiura'' eggs.
Treatment
''C. philippinensis'' infections should be treated with 200 mg of mebendazole. This drug is taken twice a day for 20 days or until all symptoms subside and there are no longer eggs present in the stool samples of the patient. Another drug that may be used is albendazole 400 mg, which is taken orally every day for at least 10 days.
References
{{DEFAULTSORT:Capillaria Philippinensis
Trichocephalida
Parasitic nematodes of fish
Parasitic nematodes of vertebrates
Parasites of birds
Parasitic nematodes of humans
Parasitic diseases
Conditions diagnosed by stool test
Nematodes described in 1968