Filarioidea

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Filarioidea
Adult Loa Loa Parasite (8905176106).jpg
Adult Loa loa filarial worm
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Nematoda
Class: Chromadorea
Order: Rhabditida
Infraorder: Spiruromorpha
Superfamily: Filarioidea
Chabaud & Anderson, 1959
Families [1]

The Filarioidea are a superfamily of highly specialised parasitic nematodes. [2] [3] Species within this superfamily are known as filarial worms or filariae (singular filaria). Infections with parasitic filarial worms cause disease conditions generically known as filariasis. Drugs against these worms are known as filaricides.

Contents

Introduction

Filarioidea all are specialised parasites and the definitive host is always a vertebrate, a mammal, bird, reptile or amphibian, but not a fish. The intermediate host is always an arthropod. [4]

Most of Filarioidea parasitise wild species, birds in particular, but some, especially in the family Onchocercidae, attack mammals, including humans and some domestic animals. Conditions that result from parasitism by Onchocercidae include some of the most troublesome diseases of the warmer regions, including river blindness and elephantiasis. [4]

Taxonomy

The Filarioidea include several families:

Filarioidea and disease

Microfilaria of Dirofilaria immitis (heartworms) in a lymph node of a dog with lymphoma. This baby nematode is in a pillow of intermediate-to-large, immature lymphocytes exhibiting multiple criteria of cancer. Microfilaria of Dirofilaria immitis (Heartworms) Surrounded by Neoplastic Lymphocytes 1.jpg
Microfilaria of Dirofilaria immitis (heartworms) in a lymph node of a dog with lymphoma. This baby nematode is in a pillow of intermediate-to-large, immature lymphocytes exhibiting multiple criteria of cancer.

In and about endemic regions filarial diseases have been public health concerns for as long as recorded history. Archaeological evidence for elephantiasis for example extends back some 3000 years, by which time apparently it already was no novelty. [6] Currently perhaps some hundreds of millions of people worldwide, mainly in tropical regions, are infected with pathogenic species of filariae. Where the diseases are endemic many times more are exposed routinely to infection. Some victims harbour more than one medically significant infection simultaneously and this can complicate diagnosis and treatment. [7]

Humankind is the definitive host of at least eight species of filariae in various families. Six are particularly significant in medical terms. The ones that mainly occupy lymph vessels and cause conditions such as adenolymphangitis, elephantiasis, and filarial fever are:

Three other medically important parasitic species are:

The other two are less seriously pathogenic but commonly parasitise humans.

Some Dirofilaria species usually parasitize animals such as dogs, but occasionally infect humans as well. They are not well adapted to humans as hosts and seldom develop properly though they may cause various confusing symptoms. [7]

Various filarial diseases specific to humans are candidates for elimination by such means as breaking the cycle of infection. To eliminate the vectors is not really practical, but if the human population were sufficiently cleared of parasites by treatment with filaricides then one year without any human reservoirs of infection should suffice to exterminate the parasite. That is the intention of for example, the Global Programme to Eliminate Lymphatic Filariasis, which aims to interrupt transmission in that way. [9]

Life cycle of Filarioidea

Whole blood with microfilaria worm, from a person with Loa loa, Giemsa stain Loa Loa.jpg
Whole blood with microfilaria worm, from a person with Loa loa , Giemsa stain

The mature worms live in the body fluids and cavities of the definitive hosts, or predominantly in particular tissues. Details vary according to species. Some of the worst pathogens invade lymphatic vessels and may be numerous enough to clog them. Some species invade deep connective tissues; some infest subcutaneous connective tissue, causing unbearable itching. Some invade the lungs or serous cavities such as the pleural cavity, or pericardial cavity. Wherever established, they may survive for years, the fertilized females continuously producing motile embryos called microfilariae rather than eggs. [7] [10]

A microfilaria cannot reproduce in the definitive host and cannot infect another definitive host directly, but must make its way through the host's body to where an intermediate host that acts as a vector can swallow it while itself acting as an ectoparasite to the definitive host. It must succeed in invading its vector organism fairly soon, because, unlike adult filarial worms, microfilariae only survive for a few months to a year or two depending on the species and they develop no further unless they are ingested by a suitable blood-feeding female insect.

In the intermediate host the microfilaria can develop further till the vector conveys it to another definitive host. In the new definitive host the microfilaria complete the final stage of development into sexual maturity; the process takes a few months to a year or more depending on species. The mature filaria then must mate before a female can produce the next generation of microfilariae, so that invasion by a single worm cannot produce an infection. Accordingly, it takes years of exposure to infections before a serious disease condition can develop in the human host.

Once a new generation of microfilariae is released in the primary host, those in turn must seek out host tissue suited to the nature of the vector species. For example, if the vector is a skin-piercing fly such as a mosquito the microfilaria must enter the peripheral blood circulation, whereas species borne by skin-rasping flies such as Simuliidae [10] and skin-cutting flies such as Tabanidae tend to establish in hypodermal tissues. For obscure reasons, some such species actually undergo daily migrations to bodily regions favoured by the vector ectoparasites. [4] [10] Outside those periods they take refuge in blood circulation of the lungs. [7]

Related Research Articles

<i>Loa loa</i> filariasis Medical condition

Loa loa filariasis, (Loiasis) is a skin and eye disease caused by the nematode worm Loa loa. Humans contract this disease through the bite of a deer fly or mango fly, the vectors for Loa loa. The adult Loa loa filarial worm can reach from three to seven centimetres long and migrates throughout the subcutaneous tissues of humans, occasionally crossing into subconjunctival tissues of the eye where it can be easily observed. Loa loa does not normally affect vision but can be painful when moving about the eyeball or across the bridge of the nose. Loiasis can cause red itchy swellings below the skin called "Calabar swellings". The disease is treated with the drug diethylcarbamazine (DEC), and when appropriate, surgical methods may be employed to remove adult worms from the conjunctiva. Loiasis belongs to the group of neglected tropical diseases, and there is a call for it to be included in the high priority listing.

<i>Loa loa</i> Species of roundworm

Loa loa is a filarial (arthropod-borne) nematode (roundworm) that causes Loa loa filariasis. Loa loa actually means "worm worm", but is commonly known as the "eye worm", as it localizes to the conjunctiva of the eye. Loa loa is commonly found in Africa. It mainly inhabits rain forests in West Africa and has native origins in Ethiopia. The disease caused by Loa loa is called loiasis and is one of the neglected tropical diseases.

<span class="mw-page-title-main">Filariasis</span> Parasitic disease caused by a family of nematode worms

Filariasis, is a filarial infection caused by parasitic nematodes (roundworms) spread by different vectors. They are included in the list of neglected tropical diseases.

<i>Wuchereria bancrofti</i> Species of parasitic worm

Wuchereria bancrofti is a filarial (arthropod-borne) nematode (roundworm) that is the major cause of lymphatic filariasis. It is one of the three parasitic worms, together with Brugia malayi and B. timori, that infect the lymphatic system to cause lymphatic filariasis. These filarial worms are spread by a variety of mosquito vector species. W. bancrofti is the most prevalent of the three and affects over 120 million people, primarily in Central Africa and the Nile delta, South and Central America, the tropical regions of Asia including southern China, and the Pacific islands. If left untreated, the infection can develop into lymphatic filariasis. In rare conditions, it also causes tropical pulmonary eosinophilia. No vaccine is commercially available, but high rates of cure have been achieved with various antifilarial regimens, and lymphatic filariasis is the target of the World Health Organization Global Program to Eliminate Lymphatic Filariasis with the aim to eradicate the disease as a public-health problem by 2020. However, this goal was not met by 2020.

<i>Brugia malayi</i> Medical condition

Brugia malayi is a filarial (arthropod-borne) nematode (roundworm), one of the three causative agents of lymphatic filariasis in humans. Lymphatic filariasis, also known as elephantiasis, is a condition characterized by swelling of the lower limbs. The two other filarial causes of lymphatic filariasis are Wuchereria bancrofti and Brugia timori, which both differ from B. malayi morphologically, symptomatically, and in geographical extent.

<i>Dirofilaria immitis</i> Species of worm that causes parasitic disease in animals

Dirofilaria immitis, also known as heartworm or dog heartworm, is a parasitic roundworm that is a type of filarial worm, a small thread-like worm, and which causes dirofilariasis. It is spread from host to host through the bites of mosquitoes. Four genera of mosquitoes transmit dirofilariasis, Aedes, Culex, Anopheles, and Mansonia. The definitive host is the dog, but it can also infect cats, wolves, coyotes, jackals, foxes, ferrets, bears, seals, sea lions and, under rare circumstances, humans.

Brugia pahangi is a parasitic roundworm belonging to the genus Brugia. It is a filarial nematode known to infect the lymph vessels of domestic cats and wild animals, causing a disease filariasis.

Acanthocheilonema is a genus within the family Onchocercidae which comprises mainly tropical parasitic worms. Cobbold created the genus Acanthocheilonema with only one species, Acanthocheilonema dracunculoides, which was collected from aardwolf in the region of South Africa in the nineteenth century. These parasites have a wide range of mammalian species as hosts, including members of Carnivora, Macroscelidea, Rodentia, Pholidota, Edentata, and Marsupialia. Many species among several genera of filarioids exhibit a high degree of endemicity in studies done on mammalian species in Japan. However, no concrete evidence has confirmed any endemic species in the genus Acanthocheilonema.

Acanthocheilonemiasis is a rare tropical infectious disease caused by a parasite known as Acanthocheilonema perstans. It can cause skin rashes, abdominal and chest pains, muscle and joint pains, neurological disorders and skin lumps. It is mainly found in Africa. The parasite is transmitted through the bite of small flies. Studies show that there are elevated levels of white blood cells.

<span class="mw-page-title-main">Lymphatic filariasis</span> Medical condition

Lymphatic filariasis is a human disease caused by parasitic worms known as filarial worms. Usually acquired in childhood, it is a leading cause of permanent disability worldwide, impacting over a hundred million people and manifesting itself in a variety of severe clinical pathologies While most cases have no symptoms, some people develop a syndrome called elephantiasis, which is marked by severe swelling in the arms, legs, breasts, or genitals. The skin may become thicker as well, and the condition may become painful. Affected people are often unable to work and are often shunned or rejected by others because of their disfigurement and disability.

<i>Mansonella perstans</i> Species of roundworm

Mansonella perstans is a filarial (arthropod-borne) nematode (roundworm), transmitted by tiny blood-sucking flies called midges. Mansonella perstans is one of two filarial nematodes that causes serous cavity filariasis in humans. The other filarial nematode is Mansonella ozzardi. M. perstans is widespread in many parts of sub-Saharan Africa, parts of Central and South America, and the Caribbean.

Mansonelliasis is the condition of infection by the nematode Mansonella. The disease exists in Africa and tropical Americas, spread by biting midges or blackflies. It is usually asymptomatic.

Brugia timori is a filarial (arthropod-borne) nematode (roundworm) which causes the disease "Timor filariasis", or "Timorian filariasis". While this disease was first described in 1965, the identity of Brugia timori as the causative agent was not known until 1977. In that same year, Anopheles barbirostris was shown to be its primary vector. There is no known animal reservoir host.

<span class="mw-page-title-main">Microfilaria</span> Early stage in the life cycle of certain parasitic nematodes in the family Onchocercidae

The microfilaria is an early stage in the life cycle of certain parasitic nematodes in the family Onchocercidae. In these species, the adults live in a tissue or the circulatory system of vertebrates. They release microfilariae into the bloodstream of the vertebrate host. The microfilariae are taken up by blood-feeding arthropod vectors. In the intermediate host the microfilariae develop into infective larvae that can be transmitted to a new vertebrate host.

<span class="mw-page-title-main">Onchocercidae</span> Family of roundworms

The Onchocercidae are a family of nematodes in the superfamily Filarioidea. This family includes some of the most devastating human parasitic diseases, such as lymphatic filariasis, onchocerciasis, loiasis, and other filariases.

Mansonella ozzardi is a filarial (arthropod-borne) nematode (roundworm). This filarial nematode is one of two that causes serous cavity filariasis in humans. The other filarial nematode that causes it in humans is Mansonella perstans. M. ozzardi is an endoparasite that inhabits the serous cavity of the abdomen in the human host. It lives within the mesenteries, peritoneum, and in the subcutaneous tissue.

<i>Dirofilaria repens</i> Species of roundworm

Dirofilaria repens is a filarial nematode that affects dogs and other carnivores such as cats, wolves, coyotes, foxes, and sea lions, as well as muskrats. It is transmitted by mosquitoes. Although humans may become infected as aberrant hosts, the worms fail to reach adulthood while infecting a human body.

Mansonella streptocerca,, is a filarial (arthropod-borne) nematode (roundworm) causing the disease streptocerciasis. It is a common parasite in the skin of humans in the rain forests of Africa, where it is thought to be a parasite of chimpanzees, as well.

Tropical pulmonary eosinophilia, is characterized by cough, bronchospasm, wheezing, abdominal pain, and an enlarged spleen. Occurring most frequently in the Indian subcontinent and Southeast Asia, TPE is a clinical manifestation of lymphatic filariasis, a parasitic infection caused by filarial roundworms that inhabit the lymphatic vessels, lymph nodes, spleen, and bloodstream. Three species of filarial roundworms, all from the Onchocercidae family, cause human lymphatic filariasis: Wuchereria bancrofti, Brugia malayi, and Brugia timori.

<i>Brugia</i> Genus of roundworms

Brugia is a genus for a group of small roundworms. They are among roundworms that cause the parasitic disease filariasis. Specifically, of the three species known, Brugia malayi and Brugia timori cause lymphatic filariasis in humans; and Brugia pahangi and Brugia patei infect domestic cats, dogs and other animals. They are transmitted by the bite of mosquitos.

References

  1. ↑ "Filarioidea". NCBI taxonomy. Bethesda, MD: National Center for Biotechnology Information. Retrieved 14 January 2019.
  2. ↑ Filarioidea at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
  3. ↑ "NCBI Taxonomy Browser" . Retrieved 2009-05-21. Filarioidea
    Taxonomy ID: 6295
    Inherited blast name: nematodes
    Rank: superfamily
    Genetic code: Translation table 1 (Standard)
    genetic code: Translation table 5 (Invertebrate Mitochondrial)
  4. 1 2 3 Janovy, John; Schmidt, Gerald D.; Roberts, Larry S. (1996). Gerald D. Schmidt & Larry S. Roberts' Foundations of parasitology. Dubuque, Iowa: Wm. C. Brown. ISBN   978-0-697-26071-0.
  5. ↑ Wheeler, Lance. "File:Microfilaria of Dirofilaria immitis (Heartworms) Surrounded by Neoplastic Lymphocytes". Flickr. Retrieved 2 December 2017.
  6. ↑ Yoshihito Otsuji. History, Epidemiology and Control of Filariasis. Trop Med Health. 2011 Mar; 39(1 Suppl 2): 3-13. doi : 10.2149/tmh.39-1-suppl_2-3 PMC   3153148
  7. 1 2 3 4 5 6 Warrell, D. A.; Weatherall, D. J.; Ledingham, J. G. G. (1996). Oxford textbook of medicine. Oxford [Oxfordshire]: Oxford University Press. ISBN   978-0-19-262140-5.
  8. ↑ GIDEON Informatics, Inc.; Dr. Stephen Berger (20 January 2017). Mansonelliasis: Global Status (2017 ed.). GIDEON Informatics Inc. pp. 15–. ISBN   978-1-4988-1619-9.
  9. ↑ Martial L Ndeffo-Mbah, Alison P Galvani. Global elimination of lymphatic filariasis. The Lancet Infectious Diseases Volume 17, No. 4, p358-359, April 2017 Published: 21 December 2016 DOI: https://dx.doi.org/10.1016/S1473-3099(16)30544-8
  10. 1 2 3 O’Donoghue, Peter. PARA-CITE. Published by: School of Molecular & Microbial Sciences, Faculty of Science, The University of Queensland, Brisbane 4072, Australia July, 2010. ISBN   978-1-8649999-1-4
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