''Capillaria philippinensis'' is a
parasitic
Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...
nematode
The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (h ...
which causes
intestinal capillariasis. This sometimes fatal disease was first discovered in Northern
Luzon
Luzon ( , ) is the largest and most populous List of islands in the Philippines, island in the Philippines. Located in the northern portion of the List of islands of the Philippines, Philippine archipelago, it is the economic and political ce ...
, 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
Tagudin, officially the Municipality of Tagudin (; ; ), is a municipality of the Philippines, municipality in the Philippine Province, province of Ilocos Sur, Philippines. According to the 2020 census, it had a population of 41,538 people.
Etymo ...
, including 77 deaths.
Witch doctor
A witch doctor (also spelled witch-doctor), or witchcraft doctor, is a kind of magical healer who treats ailments believed to be caused by witchcraft. The term is often misunderstood, and they could more accurately be called "anti-witch doctors ...
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 do ...
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).
While the natural host range is not known, experimental infestations of several fishes, including ''
Cyprinus carpio
The common carp (''Cyprinus carpio''), also known as European carp, Eurasian carp, or simply carp, is a widespread freshwater fish of eutrophic waters in lakes and large rivers in Europe and Asia.Fishbase''Cyprinus carpio'' Linnaeus, 1758/ref>Ark ...
'', ''
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 na ...
'', ''
Eleotris melanosoma'', ''
Ambassis
''Ambassis'' is a genus of ray-finned 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 ...
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
The Chinese pond heron (''Ardeola bacchus'') is an East Asian freshwater bird of the heron family (biology), family, (Ardeidae).
It is one of six species of birds known as "pond herons" (genus ''Ardeola''). It is parapatric (or nearly so) with th ...
'', ''
Nycticorax nycticorax
The black-crowned night heron (''Nycticorax nycticorax'') r 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 Nort ...
'', ''
Bubulcus ibis
The western cattle egret (''Ardea ibis'') is a species of heron (family Ardeidae) found in the tropics, subtropics and warm temperate zones. Formerly, most taxonomic authorities lumped this species and the eastern cattle egret together (called t ...
'', ''
Ixobrychus sinensis'', ''
Gallinula chloropus
The common moorhen (''Gallinula chloropus''), also known as the waterhen, is a bird species in the rail family (Rallidae). It is distributed across many parts of the Old World, across Africa, Europe, and Asia. It lives around well-vegetated marsh ...
'', and ''
Rostratula benghalensis
The greater painted-snipe (''Rostratula benghalensis'') is a species of wader in the small painted-snipe family Rostratulidae. It widely distributed across Africa and southern Asia and is found in a variety of wetland habitats, including swamps a ...
'', 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
The Mongolian gerbil or Mongolian jird (''Meriones unguiculatus'') is a 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 used in s ...
'') or monkeys (''
Macaca
The macaques () constitute a genus (''Macaca'') of gregarious Old World monkeys of the subfamily Cercopithecinae. The 23 species of macaques inhabit ranges throughout Asia, North Africa, and Europe (in Gibraltar). Macaques are principally fru ...
'' sp.) led to infestations with thousands of adult worms through "
autoinfection
Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...
". 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 reproduce by depositing fertilized zygotes outside the body (i.e., by laying or spawning) in metabolically independent incubation organs known as eggs, which nurture the embryo into moving offsprings kno ...
(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.
Diagnosis
This parasite can be diagnosed by taking a tissue
biopsy
A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, an interventional radiologist, or an interventional cardiology, interventional cardiologist. The process involves the extraction of sampling (medicine), sample ...
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