Capillaria philippinensis
Encyclopedia
Capillaria philippinensis is a parasitic nematode
which causes intestinal capillariasis
. This sometimes fatal disease was first discovered in Northern Luzon
, 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
, and fish-eating birds as definitive hosts. Humans acquire C. philippinensis by eating small species of infested fish whole and raw.
s were hired by the locals to exorcise 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.
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
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
s or monkey
s, with eggs shed in the feces of these mammal
ian hosts. Naturally infested fish (Hypseleotris bipartita and Apagon sp.) and birds (Ixobrychus
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, Puntius gonionotus, Rasbora borapetensis
, Eleotris melanosoma
, Ambassis
commersoni and Apagon sp., with C. philippinensis eggs yielded infective larvae. Experimental infestations of several birds, including Amaurornis phoenicurus
, Ardeola bacchus
, Nycticorax nycticorax
, Bubulcus ibis
, Ixobrychus sinensis
, Gallinula chloropus
, and Rostratula benghalensis
, with larvae 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
(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.
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...
which causes intestinal capillariasis
Capillariasis
-Symptoms:Symptoms in infested humans include watery diarrhea, abdominal pain, edema, weight loss, borborygmus , and depressed levels of potassium and albumin in the blood. In humans, the parasites damage the cells of the intestinal wall. This damage interferes with the absorption of nutrients...
. This sometimes fatal disease was first discovered in Northern Luzon
Luzon
Luzon is the largest island in the Philippines. It is located in the northernmost region of the archipelago, and is also the name for one of the three primary island groups in the country centered on the Island of Luzon...
, Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
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
Parasitic life cycles
Parasite life cycles can take a variety of forms, all involving the exploitation of one or more hosts. Those that must infect more than one host species to complete their life cycles are said to have complex or indirect life cycles, while those that infect a single species have direct life...
, 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, including 77 deaths. Witch doctorWitch doctor
A witch doctor originally referred to a type of healer who treated ailments believed to be caused by witchcraft. It is currently used to refer to healers in some third world regions, who use traditional healing rather than contemporary medicine...
s were hired by the locals to exorcise 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
Indirect life cycle. Fish-eating birds which harbor adult C. philippinensis in their intestine
Intestine
In human anatomy, the intestine is the segment of the alimentary canal extending from the pyloric sphincter of the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine...
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
Gerbil
A gerbil is a small mammal of the order Rodentia. Once known simply as "desert rats", the gerbil subfamily includes about 110 species of African, Indian, and Asian rodents, including sand rats and jirds, all of which are adapted to arid habitats...
s or monkey
Monkey
A monkey is a primate, either an Old World monkey or a New World monkey. There are about 260 known living species of monkey. Many are arboreal, although there are species that live primarily on the ground, such as baboons. Monkeys are generally considered to be intelligent. Unlike apes, monkeys...
s, with eggs shed in the feces of these mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
ian hosts. Naturally infested fish (Hypseleotris bipartita and Apagon sp.) and birds (Ixobrychus
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...
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, Puntius gonionotus, Rasbora borapetensis
Blackline rasbora
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...
, Eleotris melanosoma
Broadhead sleeper
The broadhead sleeper is a species of fish in the Eleotridae family. It is found in American Samoa, Fiji, French Polynesia, Hong Kong, India, Indonesia, Japan, Malaysia, Maldives, Mozambique, New Caledonia, Palau, Panama, Papua New Guinea, the Philippines, Samoa, South Africa, Taiwan, and...
, Ambassis
Ambassis
Ambassis is a genus of fish in the Ambassidae family. The genus was created by French naturalist Georges Cuvier, and is Greek for 'climbing up'.It contains the following species:* Agassiz's olive glassfish, Ambassis agassizii Steindachner, 1867....
commersoni and Apagon sp., with C. philippinensis eggs yielded infective larvae. Experimental infestations of several birds, including Amaurornis phoenicurus
White-breasted Waterhen
The White-breasted Waterhen 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...
, Ardeola bacchus
Chinese Pond Heron
The Chinese Pond Heron is an East Asian freshwater bird of the heron family .It is one of six species of birds known as "pond herons" . It is parapatric with the Indian Pond Heron to the west and the Javan Pond Heron The Chinese Pond Heron (Ardeola bacchus) is an East Asian freshwater bird of...
, Nycticorax nycticorax
Black-crowned Night Heron
The Black-crowned Night Heron commonly abbreviated to just Night Heron in Eurasia, is a medium-sized heron found throughout a large part of the world, except in the coldest regions and Australasia .-Description:Adults are...
, Bubulcus ibis
Cattle Egret
The Cattle Egret is a cosmopolitan species of heron found in the tropics, subtropics and warm temperate zones. It is the only member of the monotypic genus Bubulcus, although some authorities regard its two subspecies as full species, the Western Cattle Egret and the Eastern Cattle Egret...
, Ixobrychus sinensis
Yellow Bittern
The Yellow Bittern is a small bittern. It is of Old World origins, breeding in much of the Indian Subcontinent, east to Japan and Indonesia. It is mainly resident, but some northern birds migrate short distances...
, Gallinula chloropus
Common Moorhen
The Common Moorhen is a bird in the Rallidae family with an almost worldwide distribution. The North and South American Committees of the AOU and the IOC have voted on or before July 2011 to split the American forms into a new species Common Gallinule, however, no other committee has voted to...
, and Rostratula benghalensis
Greater Painted Snipe
The Greater Painted Snipe, Rostratula benghalensis, is a species of wader in the family Rostratulidae. It is found in marshes in Africa, India, Pakistan, and South-east Asia -Description:...
, with larvae 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
Meriones unguiculatus
Meriones unguiculatus, the Mongolian Jird or Mongolian Gerbil is a rodent belonging to subfamily Gerbillinae. It is the most widely known species of the Gerbil subfamily, and is the usual gerbil species to be kept as a pet or experimental animal, when it is known as the Domesticated Gerbil...
) or monkeys (Macaca
Macaque
The macaques constitute a genus of Old World monkeys of the subfamily Cercopithecinae. - Description :Aside from humans , the macaques are the most widespread primate genus, ranging from Japan to Afghanistan and, in the case of the barbary macaque, to North Africa...
sp.) led to infestations with thousands of adult worms through "autoinfection
Autoinfection
Autoinfection is the infection of a primary host with a parasite, particularly a helminth, in such a way that the complete life cycle of the parasite happens in a single organism, without the involvement of another host. Therefore, the primary host is at the same time the secondary host of the...
." 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
Oviparity
Oviparous animals are animals that lay eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, reptiles, all birds, the monotremes, and most insects, some molluscs and arachnids....
(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.