Filariasis

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Filariasis
Filariasis 01.png
Life cycle of Wuchereria bancrofti, a parasite that causes filariasis
Specialty Infectious disease

Filariasis is a parasitic disease caused by an infection with roundworms of the Filarioidea type. [1] These are spread by blood-feeding insects such as black flies and mosquitoes. They belong to the group of diseases called helminthiases.

Contents

These parasites exist in the wild in subtropical parts of southern Asia, Africa, the South Pacific, and parts of South America. One does not acquire them in temperate areas like Europe or the United States. [2]

Eight known filarial worms have humans as a definitive host. These are divided into three groups according to the part of the body they affect:

The adult worms, which usually stay in one tissue, release early larval forms known as microfilariae into the person's blood. These circulating microfilariae can be taken up during a blood meal by an insect vector; in the vector, they develop into infective larvae that can be spread to another person.

Individuals infected by filarial worms may be described as either "microfilaraemic" or "amicrofilaraemic", depending on whether microfilariae can be found in their peripheral blood. Filariasis is diagnosed in microfilaraemic cases primarily through direct observation of microfilariae in the peripheral blood. Occult filariasis is diagnosed in amicrofilaraemic cases based on clinical observations and, in some cases, by finding a circulating antigen in the blood.

Signs and symptoms

The most spectacular symptom of lymphatic filariasis is elephantiasis – edema with thickening of the skin and underlying tissues—which was the first disease discovered to be transmitted by mosquito bites. [3] Elephantiasis results when the parasites lodge in the lymphatic system.[ citation needed ]

Elephantiasis affects mainly the lower extremities, while the ears, mucous membranes, and amputation stumps are affected less frequently. However, different species of filarial worms tend to affect different parts of the body; Wuchereria bancrofti can affect the legs, arms, vulva, breasts, and scrotum (causing hydrocele formation), while Brugia timori rarely affects the genitals.[ citation needed ] Those who develop the chronic stages of elephantiasis are usually free from microfilariae (amicrofilaraemic), and often have adverse immunological reactions to the microfilariae, as well as the adult worms. [3]

The subcutaneous worms present with rashes, urticarial papules, and arthritis, as well as hyper- and hypopigmentation macules. Onchocerca volvulus manifests itself in the eyes, causing "river blindness" (onchocerciasis), one of the leading causes of blindness in the world.[ citation needed ] Serous cavity filariasis presents with symptoms similar to subcutaneous filariasis, in addition to abdominal pain, because these worms are also deep-tissue dwellers.[ citation needed ]

Cause

Human filarial nematode worms have complicated life cycles, which primarily consists of five stages. After the male and female worms mate, the female gives birth to live microfilariae by the thousands. The microfilariae are taken up by the vector insect (intermediate host) during a blood meal. In the intermediate host, the microfilariae molt and develop into third-stage (infective) larvae. Upon taking another blood meal, the vector insect, such as Culex pipiens , injects the infectious larvae into the dermis layer of the skin. After about one year, the larvae molt through two more stages, maturing into the adult worms.[ citation needed ]

Diagnosis

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.

Filariasis is usually diagnosed by identifying microfilariae on Giemsa stained, thin and thick blood film smears, using the "gold standard" known as the finger prick test. The finger prick test draws blood from the capillaries of the finger tip; larger veins can be used for blood extraction, but strict windows of the time of day must be observed. Blood must be drawn at appropriate times, which reflect the feeding activities of the vector insects. Examples are W. bancrofti, whose vector is a mosquito; night is the preferred time for blood collection. Loa loa's vector is the deer fly; daytime collection is preferred. [5] This method of diagnosis is only relevant to microfilariae that use the blood as transport from the lungs to the skin. Some filarial worms, such as M. streptocerca and O. volvulus, produce microfilariae that do not use the blood; they reside in the skin only. For these worms, diagnosis relies upon skin snips and can be carried out at any time.[ citation needed ]

Concentration methods

Various concentration methods are applied: membrane filter, Knott's concentration method, and sedimentation technique.[ citation needed ]

Polymerase chain reaction (PCR) and antigenic assays, which detect circulating filarial antigens, are also available for making the diagnosis. The latter are particularly useful in amicrofilaraemic cases. Spot tests for antigen [6] are far more sensitive, and allow the test to be done anytime, rather in the late hours.[ citation needed ]

Lymph node aspirate and chylous fluid may also yield microfilariae. Medical imaging, such as CT or MRI, may reveal "filarial dance sign" in the chylous fluid; X-ray tests can show calcified adult worms in lymphatics. The DEC provocation test is performed to obtain satisfying numbers of parasites in daytime samples. Xenodiagnosis is now obsolete, and eosinophilia is a nonspecific primary sign.[ citation needed ]

Treatment

The recommended treatment for people outside the United States is albendazole combined with ivermectin. [7] [8] A combination of diethylcarbamazine and albendazole is also effective. [7] [9] Side effects of the drugs include nausea, vomiting, and headaches. [10] All of these treatments are microfilaricides; they have no effect on the adult worms. While the drugs are critical for treatment of the individual, proper hygiene is also required. [11] There is good evidence that albendazole alone; or addition of albendazole to diethylcarbamazine or ivermectin, makes minimal difference in clearing microfilaria or adult worms from blood circulation. [12] Diethylcarbamazine-medicated salt is effective in controlling lymphatic filariasis while maintaining its coverage at 90% in the community for six months. [13]

Different trials were made to use the known drug at its maximum capacity in absence of new drugs. In a study from India, it was shown that a formulation of albendazole had better anti-filarial efficacy than albendazole itself. [14] [ non-primary source needed ]

In 2003, the common antibiotic doxycycline was suggested for treating elephantiasis. [15] Filarial parasites have symbiotic bacteria in the genus Wolbachia , which live inside the worm and seem to play a major role in both its reproduction and the development of the disease. This drug has shown signs of inhibiting the reproduction of the bacteria, further inducing sterility. [9] Clinical trials in June 2005 by the Liverpool School of Tropical Medicine reported an eight-week course almost eliminated microfilaraemia. [16] [ non-primary source needed ] [17]

Society and culture

Research teams

In 2015 William C. Campbell and Satoshi Ōmura were co-awarded half of that year's Nobel prize in Physiology or Medicine for the discovery of the drug avermectin, which, in the further developed form ivermectin, has decreased the occurrence of lymphatic filariasis. [17]

Prospects for elimination

Filarial diseases in humans offer prospects for elimination by means of vermicidal treatment. If the human link in the chain of infection can be broken, then notionally the disease could be wiped out in a season. In practice it is not so simple, and there are complications in that multiple species overlap in certain regions and double infections are common. This creates difficulties for routine mass treatment because people with onchocerciasis in particular react badly to treatment for lymphatic filariasis. [18]

Other animals

Filariasis can also affect domesticated animals, such as cattle, sheep, and dogs.[ citation needed ]

Cattle

Horses

Dogs

See also

Related Research Articles

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

Loa loa filariasis 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 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 one's vision but can be painful when moving about the eyeball or across the bridge of the nose. The disease 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 so-called neglected diseases.

<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">Diethylcarbamazine</span> Chemical compound

Diethylcarbamazine is a medication used in the treatment of filariasis including lymphatic filariasis, tropical pulmonary eosinophilia, and loiasis. It may also be used for prevention of loiasis in those at high risk. While it has been used for onchocerciasis, ivermectin is preferred. It is taken by mouth.

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

Elephantiasis, often incorrectly called elephantitis, is the enlargement and hardening of limbs or body parts due to tissue swelling. It is characterised by edema, hypertrophy, and fibrosis of skin and subcutaneous tissues, due to obstruction of lymphatic vessels. It may affect the genitalia. The term elephantiasis is often used in reference to parasitic worm infections, but may refer to a variety of diseases that swell parts of the subject's body to exceptionally massive proportions.

<span class="mw-page-title-main">Onchocerciasis</span> Human helminthiasis (infection by parasite)

Onchocerciasis, also known as river blindness, is a disease caused by infection with the parasitic worm Onchocerca volvulus. Symptoms include severe itching, bumps under the skin, and blindness. It is the second-most common cause of blindness due to infection, after trachoma.

<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.

<span class="mw-page-title-main">Albendazole</span> Chemical compound

Albendazole is a broad-spectrum antihelmintic and antiprotozoal agent of the benzimidazole type. It is used for the treatment of a variety of intestinal parasite infections, including ascariasis, pinworm infection, hookworm infection, trichuriasis, strongyloidiasis, taeniasis, clonorchiasis, opisthorchiasis, cutaneous larva migrans, giardiasis, and gnathostomiasis, among other diseases.

<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.

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.

<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.

In population ecology, density-dependent processes occur when population growth rates are regulated by the density of a population. This article will focus on density dependence in the context of macroparasite life cycles.

<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">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.

<span class="mw-page-title-main">Filarioidea</span> Superfamily of roundworms

The Filarioidea are a superfamily of highly specialised parasitic nematodes. Species within this superfamily are known as filarial worms or filariae. Infections with parasitic filarial worms cause disease conditions generically known as filariasis. Drugs against these worms are known as filaricides.

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. ↑ Center for Disease Control and Prevention. "Lymphatic Filariasis" . Retrieved 18 July 2010.
  2. ↑ Prevention, CDC-Centers for Disease Control and (17 September 2020). "CDC - Lymphatic Filariasis - General Information - Frequently Asked Questions". www.cdc.gov.
  3. 1 2 "Lymphatic filariasis". Health Topics A to Z. Source: The World Health Organization. Retrieved 24 March 2013.
  4. ↑ Wheeler L. "Microfilaria of Dirofilaria immitis (Heartworms) Surrounded by Neoplastic Lymphocytes". Flickr. Retrieved 2 December 2017.
  5. ↑ Metzger, Wolfram Gottfried; Mordmüller, Benjamin (April 2014). "Loa loa—does it deserve to be neglected?". The Lancet Infectious Diseases. 14 (4): 353–357. doi:10.1016/S1473-3099(13)70263-9. PMID   24332895.
  6. ↑ "Seva Fila" (PDF). JB Tropical Disease Research Centre & Department of Biochemistry, Mahatma Gandhi Institute of Medical Sciences. Archived from the original (PDF) on 4 March 2012. Retrieved 4 March 2010.
  7. 1 2 The Carter Center, Lymphatic Filariasis Elimination Program , retrieved 17 July 2008
  8. ↑ U.S. Centers for Disease Control, Lymphatic Filariasis Treatment , retrieved 17 July 2008
  9. 1 2 Taylor MJ, Hoerauf A, Bockarie M (October 2010). "Lymphatic filariasis and onchocerciasis". Lancet. 376 (9747): 1175–85. doi:10.1016/s0140-6736(10)60586-7. PMID   20739055. S2CID   29589578.
  10. ↑ Turkington CA. "Filariasis". The Gale Encyclopedia of Public Health. 1: 351–353.
  11. ↑ Hewitt K, Whitworth JA (1 August 2005). "Filariasis". Medicine. 33 (8): 61–64. doi:10.1383/medc.2005.33.8.61.
  12. ↑ Macfarlane CL, Budhathoki SS, Johnson S, Richardson M, Garner P (January 2019). "Albendazole alone or in combination with microfilaricidal drugs for lymphatic filariasis". The Cochrane Database of Systematic Reviews. 1 (1): CD003753. doi:10.1002/14651858.CD003753.pub4. PMC   6354574 . PMID   30620051.
  13. ↑ Adinarayanan S, Critchley J, Das PK, Gelband H, et al. (Cochrane Infectious Diseases Group) (January 2007). "Diethylcarbamazine (DEC)-medicated salt for community-based control of lymphatic filariasis". The Cochrane Database of Systematic Reviews. 2007 (1): CD003758. doi:10.1002/14651858.CD003758.pub2. PMC   6532694 . PMID   17253495.
  14. ↑ Gaur RL, Dixit S, Sahoo MK, Khanna M, Singh S, Murthy PK (April 2007). "Anti-filarial activity of novel formulations of albendazole against experimental brugian filariasis". Parasitology. 134 (Pt 4): 537–44. doi:10.1017/S0031182006001612. PMID   17078904. S2CID   24567214.
  15. ↑ Hoerauf A, Mand S, Fischer K, Kruppa T, Marfo-Debrekyei Y, Debrah AY, Pfarr KM, Adjei O, Buttner DW (2003), "Doxycycline as a novel strategy against bancroftian filariasis-depletion of Wolbachia endosymbionts from Wuchereria bancrofti and stop of microfilaria production", Med Microbiol Immunol (Berl), 192 (4): 211–6, doi:10.1007/s00430-002-0174-6, PMID   12684759, S2CID   23349595
  16. ↑ Taylor MJ, Makunde WH, McGarry HF, Turner JD, Mand S, Hoerauf A (2005), "Macrofilaricidal activity after doxycycline treatment of Wuchereria bancrofti: a double-blind, randomised placebo-controlled trial", Lancet, 365 (9477): 2116–21, doi:10.1016/S0140-6736(05)66591-9, PMID   15964448, S2CID   21382828
  17. 1 2 Andersson J, Forssberg H, Zierath JR (5 October 2015), "Avermectin and Artemisinin - Revolutionary Therapies against Parasitic Diseases" (PDF), The Nobel Assembly at Karolinska Institutet, retrieved 5 October 2015
  18. ↑ Ndeffo-Mbah ML, Galvani AP (April 2017). "Global elimination of lymphatic filariasis". The Lancet. Infectious Diseases. 17 (4): 358–359. doi: 10.1016/S1473-3099(16)30544-8 . PMID   28012944.
  19. ↑ Pringle H (3 March 2011), The Emperor and the Parasite , retrieved 9 March 2011

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