Filariasis are tissue helminth infections caused by nematodes, wired.
Human transmission takes place via an insect vector, during a sting.
The major pathogenic species are shown in the table below. In co-endemic areas, mixed infections are common.
Each wire has two main stages of development: macrofilaria (to adults) and microfilariae (embryos). The choice of treatment depends on the pathogenic stage of the species. It aims microfilariae for O. volvulus and macrofilariae for other species.
Conventional antifilarial are diethylcarbamazine (DEC), ivermectin and albendazole. Doxycycline is used only in the treatment of O. volvulus and lymphatic filaria, hosting symbiotic bacteria (Wolbachia) sensitive to doxycycline.
Onchocerciasis (river blindness):
The distribution of onchocerciasis is linked to that of the vector (blackfly), which breeds in fast flowing rivers in inter-tropical Africa (99% of cases), Latin America (Guatemala, Mexico, Ecuador, Colombia, Venezuela, Brazil) and Yemen.
In endemic areas, these signs associated to varying degrees, are suggestive of onchocerciasis:
– Onchocercomes: subcutaneous nodules containing adult worms, usually located next to a bone plane (iliac crest, trochanter, sacrum, rib cage, skull, etc.), measuring a few mm or cm, firm, smooth, round or oval , painless, mobile or adhering to the underlying tissue, single or multiple and contiguous to each other.
– Onchodermatosis acute papular: papular rash, sometimes diffuse but often localized to the buttocks and lower limbs, accompanied by intense itching and often secondarily infected excoriations ( “filarial itch”) 1. These symptoms result from the invasion of the dermis by microfilariae.
– Late chronic skin lesions: depigmentation of speckled shins ( “leopard skin”), skin atrophy or thickened areas of skin, dry, scaly (pachydermisation; “lizard skin”).
– Visual disturbances and eye damage.
– Detection of microfilariae in the dermis (skin biopsy bloodless, iliac crest).
– In areas where loiasis is co-endemic (mainly in Central Africa), seek Loiasis if the skin biopsy is positive.
– The diethylcarbamazine is against-indicated (risk of serious damage).
– Doxycycline PO (200 mg / day for 4 weeks minimum; if possible 6 weeks) kills a large proportion of adult worms and gradually reduces the number of microfilariae of O. 2 volvulus. It is against-indicated in children <8 years and pregnant or lactating women.
– Ivermectin PO is the treatment of choice: 150 microgram / kg single dose; a second dose is needed if clinical signs persist after 3 months. Then repeat the treatment every 6 or 12 months to maintain the parasite load audessous the threshold of appearance of clinical signs 3. Ivermectin is not recommended in children <5 years and <15 kg and in pregnant women.
– In case of co-infection with Loa loa or in areas where loiasis is co-endemic, administer ivermectin with caution (risk of severe side effects in patients heavily infected with L. loa)
• If it is possible to search Loa loa (thick film):
Confirm and quantify microfilaraemia. Depending microfilaraemia, provide treatment.
• If it is not possible to make a thick film, ask the patient:
If the patient has not developed any serious side effects during a previous treatment with ivermectin, administer the treatment.
If the patient has never taken ivermectin developed no signs of loiasis (passage of the adult worm under the conjunctiva of the eye or Calabar swellings), administer the treatment.
If the patient has already presented signs of loiasis and onchocerciasis if the signs are troublesome, administer ivermectin monitoring the environment or use an alternative (doxycycline, as above).
– In case of co-infection with a lymphatic filariasis: administer ivermectin, and a week after starting treatment Lymphatic Filariasis by doxycycline PO.
1* The differential diagnosis of filarial scabies is sarcoptic mange.
2* The removal of Wolbachia reduced longevity and fertility macrofilaria and therefore, the production of
new microfilariae in the body.
3* Ivermectin kills the microfilariae and blocks the production of microfilariae by adult worms but
treatment should be administered at regular intervals as it does not eliminate the adult worms.
The nodules are benign, sometimes very deep and their removal does not treat onchocerciasis. Nodulectomy is for cranial nodules (their proximity to the eye is a risk factor for ocular) and nodules posing an obvious cosmetic problem.The procedure is done under local anesthesia, in a suitable structure. For other nodules, abstention is recommended.
The distribution of loiasis is related to the location of the vector (chrysops) in forests or savannas with gallery forests of Central Africa (west limits: Benin, East: Uganda; northern Sudan and southern Angola).
Clinical signs :
– The transition from an adult worm under the conjunctiva of the eye is pathognomonic of Loa loa.
– Subcutaneous edema localized allergic origin, transient (hours or days), painless, no pitting, appearing on any body part, often on the upper limbs and the face, often associated with localized or generalized pruritus ( “Calabar edema”).
– Access pruritus, no other sign.
– Passage of an adult worm under the skin: red cord, palpable, sinuous, pruritic, mobile (1 cm / hour), quickly disappearing without trace 4. The passage of a wire under the skin, rarely spontaneous, usually occurs after taking diethylcarbamazine.
– Detection of microfilariae in the peripheral blood (thick stained with Giemsa). The sample should be taken between 10 and 17 hours. Quantify microfilaraemia even if the diagnosis is certain because the intensity of the parasitic load determines the conduct of the treatment.
– In areas where onchocerciasis is co-endemic (mainly in Central Africa), seek onchocerciasis if positive blood film.
– The diethylcarbamazine (DEC) is the only available macrofilaricide but is against-indicated:
• In patients with microfilaraemia is> 2000 mf / ml (risk of severe encephalopathy, poor prognosis).
• In co-infected patients O. volvulus (risk of severe eye damage).
• In pregnant women, infants and in case of significant deterioration of general condition.
4* For the differential diagnosis, see cutaneous larva migrans.
– Ivermectin (and possibly albendazole) are used to reduce the microfilaria before administering DEC but ivermectin may cause encephalopathy very heavily infected patients (> 30 000 mf / ml).
– Doxycycline is not indicated since Wolbachia is not present in L. loa.
– To behave :
1) The microfilariae of L. loa is <1000 to 2000 mf / ml:
The 28-day DEC treatment can be started with low doses of 3 or 6 mg / day, or about 1/32 or 1/16 of 100 mg tablet administered in 2 doses.
Doubling the daily dose to 400 mg / day in 2 divided doses for adults (3 mg / kg / day in children).
If microfilaraemia or symptoms persist, a second treatment is started at 4 week intervals.
If DEC is against-indicated because of a possible co-infection or confirmed by O. volvulus, ivermectin (150 micrograms / kg single dose) reduces pruritus, edema frequency of Calabar and treat onchocerciasis.
The treatment is possibly renewed every month or every 3 months.
2) The microfilariae of L. loa is between 2000 and 8000 mf / ml:
Lower microfilaraemia with ivermectin (150 micrograms / kg single dose); repeat the treatment every month if necessary; administer December when microfilaraemia is <2000 mf / ml.
3) The microfilariae of L. loa is between 8000 and 30,000 mf / ml:
Treatment with ivermectin (150 micrograms / kg single dose) can cause marked functional impairment for a few days.Monitoring by the entourage is required 5. Also prescribe paracetamol to 7 days.
4) The microfilariae of L. loa exceeds 30,000 mf / ml:
• Abstention may be preferable if loiasis is well tolerated because the disease is benign and ivermectin can cause, though rarely, very severe side effects (encephalopathy).
• If Loiasis a significant clinical impact and / or if the patient is symptomatic onchocerciasis must be treated, treatment with ivermectin (150 micrograms / kg single dose) is administered under supervision of five days in the hospital environment 6. You can try to lower pre microfilaremia L. loa with treatment with albendazole (400 mg / day in 2 divided doses for 3 weeks). When microfilaremia L. loa is <30 000 mf / ml, treated with ivermectin, with oversight by the surroundings and by the DEC when microfilaraemia is <2000 mf / ml.
The subcutaneous passage of an adult worm is usually the result of DEC treatment, the worm comes to die under the skin, there is no need to extract it.
When changing subconjunctival.
5* Patients may have various pains, unable to move without help or can not move at all. Monitoring is whether the patient remains autonomous for daily needs, and to ensure these needs if necessary. If the patient remains bedridden for several days, make sure he does not develop bedsores (mobilize, turn).
6* A severe reaction may occur to J2-J3. It is almost always preceded by haemorrhages of the palpebral conjunctiva to J1-J2. Search this sign, turning eyelids. If post-ivermectin encephalopathy disorders are reversible and the prognosis if the patient is cared for properly; treatment is symptomatic until resolution of symptoms. Avoid steroids because of side effects.
Lymphatic filariasis (LF):
The distribution of LF is linked to the location of mosquitoes (Anopheles, Culex, Aedes, etc.):
Bancroftian: Sub-Saharan Africa, Madagascar, Egypt, India, Southeast Asia, the Pacific, South America, Caribbean B.malayi: Southeast Asia, China, India, Sri Lanka B. timori Timor
FL W. bancrofti represent 90% of FL and Brugia sp, 10% of cases.
Clinical signs :
– Acute inflammatory Recurrent Events
• adenolymphangitis: lymphadenopathy (s) and edema red, warm, painful, along the path of a lymphatic vessel, with or without symptoms (eg, fever, nausea, vomiting..). The inflammation affects the lower limb or genitalia or breast.
• In men: acute inflammation of the spermatic cord (funiculitis), epididymis and testis (epididymoorchitis).
The yield pushed spontaneously in a week and usually occur in patients with chronic manifestations.
– Chronic Events
• Lymphedema: lymphatic edema of the lower limbs or genitalia or breast secondary to lymphatic obstruction by macrofilariae. Lymphedema is first reversible then becomes chronic and increasingly severe: hypertrophy of the affected area, gradually pachydermisation skin (fibrous thickening, formation of superficial and deep folds and warty lesions). The final stage of lymphedema is elephantiasis.
• In men: increase in the volume of grants by accumulation of fluid in the vaginal cavity (hydrocele, lymphocele, chylocele); Chronic epididymoorchitis.
• Chyluria: milky urine or rice water (rupture of a lymphatic vessel in the urinary tract).
In patients infected with Brugia sp, genital lesions and chyluria are rare; Lymphedema is often confined below the knee.
– Detection of microfilariae in the peripheral blood (smear, thick drop) 7; the sample should be taken from 21 am and 3 am.
– In areas where loiasis and / or onchocerciasis are co-endemic, search co-infection if the diagnosis is positive FL.
– The treatment is administered outside of an acute attack.
7* If negative examination in a clinically suspect patient, one can consider looking for circulating antigens (ICT rapid test) and / or an ultrasound of the inguinal region in search of “nests of worms” ( “filaria dance sign “).
– Doxycycline PO eliminates the majority of adult worms and improve lymphedema, only if administered in prolonged treatment: 200 mg / day for 4 weeks minimum. It is against-indicated in children <8 years and pregnant or lactating women.
– The diethylcarbamazine PO in a single dose (400 mg in adults, 3 mg / kg in children) may be an alternative but eliminates that part of macrofilaria (up 40%) and improved no symptoms; prolonged treatment no more effective than a single dose; DEC is more against-indicated in patients with onchocerciasis and Loa loa microfilariae> 2000 mf / ml and in pregnant or lactating.
– Ivermectin (low macrofilaricide effect, if not zero) and albendazole should not be used in individual treatment (lack of effect on clinical signs).
– If co-probable or confirmed infection O. volvulus: treat onchocerciasis then administer doxycycline.
Control / prevention of inflammatory events and infectious complications:
– Acute Driven: bed rest, elevation of the limb, bandage, a member of cooling (wet cloth, cold bath) and analgesics;Local treatment antibiotic / antifungal if necessary; if fever, antipyretics (paracetamol) and hydration.
– Preventing outbreaks of adenolymphangitis and lymphedema: hygiene of the affected limb 8, wear comfortable shoes, immediate attention to bacterial / fungal secondary infections and injuries.
– Lymphedema consists of: bandage the affected limb in the day, heightening member (after removing the tape) in a period of rest, practice simple exercises (lying in the flexion-extension position or standing foot, ankle rotation); skin hygiene, as above.
May be indicated in the treatment of chronic manifestations: Lymphedema
evolved (diversion-reconstruction), hydrocele and its complications, chyluria.
8* Wash at least once / day (soap and water at room temperature), highlighting folds and interdigital spaces; thorough rinsing and drying with a clean towel; nail care.