The Info List - Filariasis

--- Advertisement ---

is a parasitic disease caused by an infection with roundworms of the Filarioidea
type.[1] These are spread by blood-feeding black flies and mosquitoes. This disease belongs to the group of diseases called helminthiases. Eight known filarial nematodes use humans as their definitive hosts. These are divided into three groups according to the niche they occupy in the body:

Lymphatic filariasis
Lymphatic filariasis
is caused by the worms Wuchereria bancrofti, Brugia malayi, and Brugia timori. These worms occupy the lymphatic system, including the lymph nodes; in chronic cases, these worms lead to the syndrome of elephantiasis. Subcutaneous filariasis is caused by Loa loa
Loa loa
(the eye worm), Mansonella
streptocerca, and Onchocerca volvulus. These worms occupy the subcutaneous layer of the skin, in the fat layer. L. loa causes Loa loa
Loa loa
filariasis, while O. volvulus causes river blindness. Serous cavity filariasis is caused by the worms Mansonella
perstans and Mansonella
ozzardi, which occupy the serous cavity of the abdomen. Dirofilaria immitis, the dog heartworm, rarely infects humans.

The adult worms, which usually stay in one tissue, release early larval forms known as microfilariae into the host's bloodstream. These circulating microfilariae can be taken up with a blood meal by the arthropod vector; in the vector, they develop into infective larvae that can be transmitted to a new host. 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.


1 Signs and symptoms 2 Cause 3 Diagnosis

3.1 Concentration methods

4 Treatment 5 Society and culture

5.1 Research teams 5.2 Prospects for elimination

6 Other animals

6.1 Cattle 6.2 Horses 6.3 Dogs

7 See also 8 References 9 Further reading 10 External links

Signs and symptoms[edit] 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.[2] Elephantiasis results when the parasites lodge in the lymphatic system. 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
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.[2] 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. Cause[edit] 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 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. Diagnosis[edit]

of Dirofilaria immitis
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.[3]

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. 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 microfilarae 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. Concentration methods[edit]

This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (May 2010) (Learn how and when to remove this template message)

Various concentration methods are applied: membrane filter, Knott's concentration method, and sedimentation technique. Polymerase chain reaction
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[4] are far more sensitive, and allow the test to be done anytime, rather in the late hours. 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. Treatment[edit] The recommended treatment for people outside the United States is albendazole combined with ivermectin.[5][6] A combination of diethylcarbamazine and albendazole is also effective.[5][7] Side effects of the drugs include nausea, vomiting, and headaches.[8] 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.[9] 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.[10][non-primary source needed] In 2003, the common antibiotic doxycycline was suggested for treating elephantiasis.[11] 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.[12] Clinical trials in June 2005 by the Liverpool School of Tropical Medicine
Liverpool School of Tropical Medicine
reported an eight-week course almost completely eliminated microfilaraemia.[13][non-primary source needed] Society and culture[edit] Research teams[edit] In 2015 William C. Campbell and Satoshi Ōmura
Satoshi Ōmura
were Co-awarded half of that year's Nobel prize in Physiology or Medicine
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.[14] Prospects for elimination[edit] 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 quite 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.[15] Other animals[edit] Filariasis
can also affect domesticated animals, such as cattle, sheep, and dogs. Cattle[edit]

Verminous hemorrhagic dermatitis is a clinical disease in cattle due to Parafilaria bovicola. Intradermal onchocerciasis of cattle results in losses in leather due to Onchocerca dermata, O. ochengi, and O. dukei. O. ochengi is closely related to human O. volvulus (river blindness), sharing the same vector, and could be useful in human medicine research. Stenofilaria assamensis and others cause different diseases in Asia, in cattle and zebu.


"Summer bleeding" is hemorrhagic subcutaneous nodules in the head and upper forelimbs, caused by Parafilaria multipapillosa (North Africa, Southern and Eastern Europe, Asia and South America).[16]


Heart filariasis is caused by Dirofilaria immitis.

See also[edit]

Neglected diseases Eradication of infectious diseases Helminthiasis List of parasites (human)


^ Center for Disease Control and Prevention. "Lymphatic Filariasis". Retrieved 18 July 2010.  ^ a b "Lymphatic filariasis". Health Topics A to Z. Source: The World Health Organization. Retrieved 2013-03-24.  ^ Wheeler, Lance. Flickr https://www.flickr.com/gp/146435388@N03/0670TX. Retrieved 2 December 2017.  Missing or empty title= (help) ^ "Seva Fila" (PDF). JB Tropical Disease Research Centre & Department of Biochemistry, Mahatma Gandhi Institute of Medical Sciences.  ^ a b The Carter Center, Lymphatic Filariasis
Elimination Program, retrieved 2008-07-17  ^ U.S. Centers for Disease Control, Lymphatic Filariasis
Treatment, retrieved 2008-07-17  ^ Bockarie, Moses; Hoerauf, Achim; Taylor, Mark J. (8 October 2010). " Lymphatic filariasis
Lymphatic filariasis
and onchocerciasis". The Lancet. 376 (9747): 1175–1185. doi:10.1016/s0140-6736(10)60586-7.  ^ Turkington, Carol A. "Filariasis". The Gale Encyclopedia of Public Health. 1: 351–353.  access-date= requires url= (help) ^ Hewitt, Kirsten; Whitworth, James AG (1 August 2005). "Filariasis". Medicine. 33 (8): 61–64. doi:10.1383/medc.2005.33.8.61.  ^ Gaur RL, Dixit S, Sahoo MK, Khanna M, Singh S, Murthy PK (2007). "Anti-filarial activity of novel formulations of albendazole against experimental brugian filariasis". Parasitology. 134: 537–44. doi:10.1017/S0031182006001612. PMID 17078904.  ^ 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
Wuchereria bancrofti
and stop of microfilaria production", Med Microbiol Immunol (Berl), 192 (4): 211–6, doi:10.1007/s00430-002-0174-6, PMID 12684759  ^ Bockarie, Moses; Hoerauf, Achim; Taylor, Mark J. (8 October 2010). " Lymphatic filariasis
Lymphatic filariasis
and onchocerciasis". The Lancet. 376 (9747): 1178. doi:10.1016/s0140-6736(10)60586-7.  ^ 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  ^ Jan Andersson; Hans Forssberg; Juleen R. Zierath; The Nobel Assembly at Karolinska Institutet (5 October 2015), Avermectin
and Artemisinin - Revolutionary Therapies against Parasitic Diseases (PDF), retrieved 5 October 2015  ^ Ndeffo-Mbah Martial L, Galvani Alison P. "Global elimination of lymphatic filariasis". The Lancet Infectious Diseases. 17 (4): 358–359. doi:10.1016/S1473-3099(16)30544-8.  ^ Pringle, Heather (3 March 2011), The Emperor and the Parasite, retrieved 9 March 2011 

Further reading[edit]

" Special
issue", Indian Journal of Urology, 21 (1), 2005  "Filariasis". Therapeutics in Dermatology. June 2012. Retrieved 24 July 2012. 

External links[edit]


V · T · D

ICD-10: B74 ICD-9-CM: 125.0-125.9 MeSH: D005368

External resources

Patient UK: Filariasis

Wikimedia Commons has media related to Filariasis.

Research at the University of Tuebingen The Carter Center Lymphatic Filariasis
Elimination Program UK Health Charity working to cure and prevent Lymphatic filariasis Brugia malayi
Brugia malayi
Filarial worms. Video by R. Rao. Washington University in St. Louis Page from the "Merck Veterinary Manual" on "Parafilaria multipapillosa" in horses

v t e

Infectious diseases Parasitic disease: helminthiases

B65–B83 120–129

Flatworm/ platyhelminth infection

Fluke/trematode (Trematode infection)

Blood fluke



Trichobilharzia regenti

Swimmer's itch

Liver fluke

Clonorchis sinensis


Dicrocoelium dendriticum/Dicrocoelium hospes


Fasciola hepatica/gigantica


Opisthorchis viverrini/Opisthorchis felineus


Lung fluke

Paragonimus westermani/Paragonimus kellicotti


Intestinal fluke



Metagonimus yokagawai


Heterophyes heterophyes


Cestoda (Tapeworm infection)


Echinococcus granulosus/Echinococcus multilocularis


Taenia saginata/Taenia asiatica/ Taenia solium
Taenia solium


Hymenolepis nana/Hymenolepis diminuta





Spirometra erinaceieuropaei




Roundworm/ Nematode infection




Dracunculus medinensis



Filarioidea (Filariasis)

Onchocerca volvulus


Loa loa

Loa loa
Loa loa



Dirofilaria repens Dirofilaria immitis


Wuchereria bancrofti/Brugia malayi/Brugia timori

Lymphatic filariasis


Gnathostoma spinigerum/Gnathostoma hispidum






Strongylida (hookworm)

infection Ancylostoma duodenale/Ancylostoma braziliense

Ancylostomiasis Cutaneous larva migrans

Necator americanus


Angiostrongylus cantonensis





Ascaris lumbricoides




Toxocara canis/Toxocara cati

Visceral larva migrans/Toxocariasis

Baylisascaris Dioctophyme renale


Parascaris equorum


Strongyloides stercoralis




Halicephalobus gingivalis


Enterobius vermicularis

Enterobiasis Pinworm


Trichinella spiralis


Trichuris trichiura
Trichuris trichiura
( Trichuriasis
* Whipworm) Capillaria philippinensis

Intestinal capillariasis