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Filariasis
Filariasis is a parasitic tropical disease caused by thread-like nematode worms belonging to the subfamily Filarioidea, spread by vectors.
• Nine species of filarial worms utilize humans as definitive hosts, residing in lymphatics, skin, connective tissue, serous cavities, and blood vessels. • Adult worms can inhabit the host for more than 20 years.
EPIDEMIOLOGY • Bancroftian and Malayan filariasis – Endemic in 83 countries across tropical and subtropical regions of Asia, Africa, Central and South America, and Pacific Island states. Approximately 1.3 billion individuals globally are at risk of illness (1).
- 120 million individuals have already been infected (1).
Approximately 40 million individuals are afflicted with debilitating or disfiguring diseases (1).
• Loiasis
- Restricted to the rainforest region of western and central Africa. Humans constitute the sole identified reservoir. • Onchocerciasis (“river blindness”) - Approximately 18 million individuals are affected (1).
– Approximately 270,000 individuals are blind, and a further 500,000 are visually impaired. Second primary cause of global blindness behind trachoma (1).
- Illness observed in South America and Africa.
Dracunculiasis (Guinea worm) primarily manifests in a limited region encompassing some African nations and Yemen (1). • Dirofilariasis (Canine heartworm) – Symptomatic infection infrequent (1) – Global distribution Mansonelliasis is a disease prevalent in Africa, Central and South America, and the Caribbean.
FACTORS OF RISK
• Residing in or visiting endemic regions • Diminished socio-economic standing
Genetics
No genetic variables are implicated
GENERAL PREVENTION • Health education • Vector control strategies
• Sleep beneath a mosquito net • Apply insect repellent containing a minimum of 30% DEET (N,N-Diethyl-meta-toluamide) on exposed skin and clothing • Wear long-sleeved garments to avert insect bites • Administer diethylcarbamazine 300 mg/week orally as prophylaxis against Loiasis • Dracunculiasis – Consume clean, boiled water – Filter copepods from drinking water – Restrict individuals with Guinea worm ulcers from accessing drinking water sources
- Administer chemical treatments, such as Abate, to eliminate copepods in contaminated water sources. - Introduce fish species that consume copepods into affected water bodies.
PATHOPHYSIOLOGY • Bancroftian and Malayan Filariasis Adult worms induce hypertrophy and dilation of lymphatic channels, resulting in valve dysfunction and subsequent extensive permanent lymphedema.
“Elephantiasis.” • Loiasis – Larvae infiltrate through the bite of a red fly, subsequently molting and migrating beneath the skin, resulting in temporary migratory angioedema (“Calabar” swellings), discomfort, pruritus, and urticaria, which are localized hypersensitivity reactions.
• Onchocerciasis — Larvae are introduced through a blackfly bite, mature, and reproduce, yielding microfilariae around one year post-bite. Adult worms reside in nodules inside the dermis and deep fascia. Microfilariae traverse the dermis and may infiltrate the ocular region, resulting in inflammation that can lead to blindness, known as "river blindness," as well as skin nodules and onchodermatitis.
• Dracunculiasis – Larvae are consumed by contaminated drinking water containing infected copepods. Larvae are discharged. They infiltrate the intestine, develop within the abdominal cavity, and reproduce. Male specimens perish, while gravid females move to the lower extremities, where they generate a papule that ultimately ulcerates. The worm surfaces to discharge larvae upon contact with water. Worms that do not penetrate the skin perish and undergo calcification.
Dirofilariasis involves worms that elicit a mild granulomatous response in subcutaneous tissue or obstruct a pulmonary artery, resulting in a solitary, minor pulmonary infarct.
Mansonelliasis involves the release of antigenic material from dying worms, which triggers an inflammatory response that leads to the formation of localized abscesses and granulomas.
ETIOLOGY
• Lymphatic filariasis – Infection caused by Wuchereria bancrofti, Brugia malayi, and Brugia timori – Transmitted by mosquitoes of the Anopheles, Aedes, Culex, and Mansonia genera
• Loa loa is transmitted by red tabanid flies (Chrysops species). • Onchocerca volvulus is transmitted by blackflies (Simulium species).
Dracunculus medinensis is consumed through drinking water contaminated with infected microcrustaceans (copepods).
Dirofilaria species spread by Culex mosquitoes.
Mansonella streptocerca is transmitted by midges of the Culicoides genus.
Mansonella perstans and Mansonella ozzardi induce serous cavity filariasis.
FREQUENTLY CO-OCCURRING CONDITIONS
No frequently correlated situations
DIAGNOSTIC HISTORY • Bancroftian and Malayan filariasis – Acute manifestations including fever, lymphadenitis, lymphangitis, funiculitis, and epididymitis – Chronic manifestations including abscesses, hyperkeratosis, polyarthritis, hydroceles, lymphoedema, and elephantiasis – Bronchospasm
• Loiasis – Temporary edema, typically of the wrists and ankles, accompanied by pruritus, paresthesia, and urticaria – Worm migration within the ocular region • Onchocerciasis – Subcutaneous nodules, pruritus, rashes, lymphadenopathy, lymphatic obstruction, chronic dermatological conditions, ocular lesions • Dracunculiasis – Painful, inflamed cutaneous lesion harboring a worm and arthritis • Dirofilariasis – Thoracic pain, cough, and hemoptysis • Mansonelliasis
Localized edema, pruritus, pyrexia, cephalalgia, arthralgia, neurological symptoms, and hydroceles
Inquire on travel to endemic regions.
PHYSICAL EXAMINATION
• Bancroftian and Malayan filariasis – Lymphangitis and lymphadenitis – Femoral/inguinal lymphadenopathy – Enlarged epididymis and spermatic cord – Hydrocele, lower extremity lymphoedema – May induce monoarticular arthritis
• Loiasis – Mature worms may migrate beneath the conjunctiva or into the dermis.
Calabar swelling frequently occurs in the wrists and ankles; the edema may persist for only hours but might repeat over several years. • Onchocerciasis – Dermatological alterations range from papular eruptions to regions of hyper- or hypopigmentation.
– Patients may exhibit eczematoid dermatitis and dermal thickening.
– Nontender subcutaneous nodules. – Potential reduction in optical acuity. • Dracunculiasis – A white, filamentous adult worm manifests at the cutaneous surface.
Ulceration in distal extremities. • Dirofilariasis – Typically asymptomatic Mansonelliasis is characterized by angioedema, pruritus, papular rash, alterations in skin pigmentation, fever, headaches, arthralgia, lymphadenopathy, hepatomegaly, and neurological symptoms.
DIAGNOSTIC TESTS AND INTERPRETATION Laboratory
• Bancroftian and Malayan filariasis - Blood smears reveal the presence of filarial worms.
– Serological assays lack specificity in filariasis. – Eosinophilia is frequently absent.
– PCR-based assays for the DNA of W. bancrofti and B. malayi are accessible in research environments.
• Loiasis – Blood smears, skin snips, or skin biopsy
• Onchocerciasis – Microscopic examination of skin biopsies reveals the presence of worms – Dracunculiasis – Diagnosis is clinical.
• Dirofilariasis - Histological Examination
• Mansonelliasis – Blood smears reveal filarial worms.
Microscopic examination of the skin biopsy reveals the presence of worms. Eosinophilia is significant.
Imaging
• Bancroftian and Malayan filariasis — Adult worms may be observed in dilated lymphatics using ultrasound. • Onchocerciasis – Cutaneous and subcutaneous nodules identified with ultrasound and magnetic resonance imaging.
• Dracunculiasis – Standard radiography reveal calcified worms.
• Dirofilariasis – Larvae can become encapsulated within necrotic lung tissue, resulting in distinct pulmonary nodules that may be detectable on computed tomography images.
DIFFERENTIAL DIAGNOSIS
Bancroftian and Malayan filariasis include bacterial lymphangitis, thrombophlebitis, idiopathic hydrocele, congestive heart failure, cirrhosis, and nephrotic syndrome. • Loiasis
– Cutaneous larva migrans, dracunculiasis, gnathostomiasis, myiasis, onchocerciasis • Onchocerciasis – M. streptocerca, scabies, leprosy, eczema, glaucoma, loiasis • Dracunculiasis – Cutaneous larva migrans, loiasis, rat bite infection, gnathostomiasis, myiasis • Dirofilariasis – Asthma, allergies, lung cancer • Mansonelliasis – Loiasis, onchocerciasis
INITIAL THERAPEUTIC AGENT
• Bancroftian and Malayan filariasis — Wolbachia spp., a genus of Rickettsia, are essential for filarial growth. Administer Doxycycline 100 mg orally twice daily for a duration of 4 to 6 weeks to address Wolbachia. Four months subsequent to initiating treatment, a single dosage of albendazole 400 mg orally and ivermectin 150 mg/kg orally was administered.
• Loiasis - Administer a single dosage of diethylcarbamazine citrate (DEC) at 6 mg/kg orally.
• Onchocerciasis - Administer one dosage of ivermectin at 150 mcg/kg orally (ineffective against mature worms). Recur in six months.
– Administer prednisone at a dosage of 1 mg/kg/day orally one week prior to ivermectin if ocular involvement is present.
• Dracunculiasis – Gradual and meticulous removal of the protruding worm.
Metronidazole 250 mg administered orally three times daily may
Mitigate inflammatory response, hence aiding in the expulsion of worms. Mebendazole 400–800 mg each day for 6 days may eradicate the worm.
• M. perstans – Administer albendazole 400 mg orally twice daily for 10 days. • M. streptocerca and M. ozzardi – Administer a single dose of ivermectin at 200 mcg/kg. • Dirofilariasis – No effective pharmacological treatment available. Second Line
• Bancroftian and Malayan filariasis – DEC, as previously mentioned for M. streptocerca. DEC should not be administered in regions with endemic lymphatic filariasis and loiasis/onchocerciasis.
SUPPLEMENTARY THERAPY
Comprehensive Measures
The treatment primarily targets the microfilarial stage of the infection. Adult worms are seldom impacted by a single dose of medicine. Repetitive therapy is frequently required for a cure.
Concerns for Referral
• Specialists in infectious diseases • Ophthalmologist for ocular assessment in onchocerciasis
CHIRURGICAL INTERVENTIONS/ADDITIONAL PROCEDURES
• Nodulectomy of palpable nodules in onchocerciasis • Surgical excision of dirofilariasis from the lung IN-PATIENT CONSIDERATIONS
Preliminary Stabilization
Resuscitation in accordance with advanced life support protocols as necessary
Criteria for Admission
• Patients with septicemia resulting from open wounds • Overnight admission for nocturnal blood sample collection for diagnostic testing
IV Fluids • Administer fluid resuscitation using colloids, such as Gelofusine, in cases of septicemia.
• Maintenance fluids utilizing Ringer's lactate
Nursing
Patients with elephantiasis may require comprehensive nursing care for the affected body portion.
Release Criteria for the resolution of septicemia
CONTINUING CARE POST-TREATMENT RECOMMENDATIONS
Every 4 to 6 weeks for treatment evaluation and symptomatic management
Patient Surveillance
Routine ocular assessments
OUTLOOK
Disability and disfigurement are mitigated by accurate diagnosis and therapy.
COMPLICATIONS
Bancroftian filariasis - Elephantiasis; Septicemia resulting from bacterial infection of exposed sores.
• Onchocerciasis - Visual Impairment
Filariasis is a parasitic tropical disease caused by thread-like nematode worms belonging to the subfamily Filarioidea, spread by vectors.
• Nine species of filarial worms utilize humans as definitive hosts, residing in lymphatics, skin, connective tissue, serous cavities, and blood vessels. • Adult worms can inhabit the host for more than 20 years.
EPIDEMIOLOGY • Bancroftian and Malayan filariasis – Endemic in 83 countries across tropical and subtropical regions of Asia, Africa, Central and South America, and Pacific Island states. Approximately 1.3 billion individuals globally are at risk of illness (1).
- 120 million individuals have already been infected (1).
Approximately 40 million individuals are afflicted with debilitating or disfiguring diseases (1).
• Loiasis
- Restricted to the rainforest region of western and central Africa. Humans constitute the sole identified reservoir. • Onchocerciasis (“river blindness”) - Approximately 18 million individuals are affected (1).
– Approximately 270,000 individuals are blind, and a further 500,000 are visually impaired. Second primary cause of global blindness behind trachoma (1).
- Illness observed in South America and Africa.
Dracunculiasis (Guinea worm) primarily manifests in a limited region encompassing some African nations and Yemen (1). • Dirofilariasis (Canine heartworm) – Symptomatic infection infrequent (1) – Global distribution Mansonelliasis is a disease prevalent in Africa, Central and South America, and the Caribbean.
FACTORS OF RISK
• Residing in or visiting endemic regions • Diminished socio-economic standing
Genetics
No genetic variables are implicated
GENERAL PREVENTION • Health education • Vector control strategies
• Sleep beneath a mosquito net • Apply insect repellent containing a minimum of 30% DEET (N,N-Diethyl-meta-toluamide) on exposed skin and clothing • Wear long-sleeved garments to avert insect bites • Administer diethylcarbamazine 300 mg/week orally as prophylaxis against Loiasis • Dracunculiasis – Consume clean, boiled water – Filter copepods from drinking water – Restrict individuals with Guinea worm ulcers from accessing drinking water sources
- Administer chemical treatments, such as Abate, to eliminate copepods in contaminated water sources. - Introduce fish species that consume copepods into affected water bodies.
PATHOPHYSIOLOGY • Bancroftian and Malayan Filariasis Adult worms induce hypertrophy and dilation of lymphatic channels, resulting in valve dysfunction and subsequent extensive permanent lymphedema.
“Elephantiasis.” • Loiasis – Larvae infiltrate through the bite of a red fly, subsequently molting and migrating beneath the skin, resulting in temporary migratory angioedema (“Calabar” swellings), discomfort, pruritus, and urticaria, which are localized hypersensitivity reactions.
• Onchocerciasis — Larvae are introduced through a blackfly bite, mature, and reproduce, yielding microfilariae around one year post-bite. Adult worms reside in nodules inside the dermis and deep fascia. Microfilariae traverse the dermis and may infiltrate the ocular region, resulting in inflammation that can lead to blindness, known as "river blindness," as well as skin nodules and onchodermatitis.
• Dracunculiasis – Larvae are consumed by contaminated drinking water containing infected copepods. Larvae are discharged. They infiltrate the intestine, develop within the abdominal cavity, and reproduce. Male specimens perish, while gravid females move to the lower extremities, where they generate a papule that ultimately ulcerates. The worm surfaces to discharge larvae upon contact with water. Worms that do not penetrate the skin perish and undergo calcification.
Dirofilariasis involves worms that elicit a mild granulomatous response in subcutaneous tissue or obstruct a pulmonary artery, resulting in a solitary, minor pulmonary infarct.
Mansonelliasis involves the release of antigenic material from dying worms, which triggers an inflammatory response that leads to the formation of localized abscesses and granulomas.
ETIOLOGY
• Lymphatic filariasis – Infection caused by Wuchereria bancrofti, Brugia malayi, and Brugia timori – Transmitted by mosquitoes of the Anopheles, Aedes, Culex, and Mansonia genera
• Loa loa is transmitted by red tabanid flies (Chrysops species). • Onchocerca volvulus is transmitted by blackflies (Simulium species).
Dracunculus medinensis is consumed through drinking water contaminated with infected microcrustaceans (copepods).
Dirofilaria species spread by Culex mosquitoes.
Mansonella streptocerca is transmitted by midges of the Culicoides genus.
Mansonella perstans and Mansonella ozzardi induce serous cavity filariasis.
FREQUENTLY CO-OCCURRING CONDITIONS
No frequently correlated situations
DIAGNOSTIC HISTORY • Bancroftian and Malayan filariasis – Acute manifestations including fever, lymphadenitis, lymphangitis, funiculitis, and epididymitis – Chronic manifestations including abscesses, hyperkeratosis, polyarthritis, hydroceles, lymphoedema, and elephantiasis – Bronchospasm
• Loiasis – Temporary edema, typically of the wrists and ankles, accompanied by pruritus, paresthesia, and urticaria – Worm migration within the ocular region • Onchocerciasis – Subcutaneous nodules, pruritus, rashes, lymphadenopathy, lymphatic obstruction, chronic dermatological conditions, ocular lesions • Dracunculiasis – Painful, inflamed cutaneous lesion harboring a worm and arthritis • Dirofilariasis – Thoracic pain, cough, and hemoptysis • Mansonelliasis
Localized edema, pruritus, pyrexia, cephalalgia, arthralgia, neurological symptoms, and hydroceles
Inquire on travel to endemic regions.
PHYSICAL EXAMINATION
• Bancroftian and Malayan filariasis – Lymphangitis and lymphadenitis – Femoral/inguinal lymphadenopathy – Enlarged epididymis and spermatic cord – Hydrocele, lower extremity lymphoedema – May induce monoarticular arthritis
• Loiasis – Mature worms may migrate beneath the conjunctiva or into the dermis.
Calabar swelling frequently occurs in the wrists and ankles; the edema may persist for only hours but might repeat over several years. • Onchocerciasis – Dermatological alterations range from papular eruptions to regions of hyper- or hypopigmentation.
– Patients may exhibit eczematoid dermatitis and dermal thickening.
– Nontender subcutaneous nodules. – Potential reduction in optical acuity. • Dracunculiasis – A white, filamentous adult worm manifests at the cutaneous surface.
Ulceration in distal extremities. • Dirofilariasis – Typically asymptomatic Mansonelliasis is characterized by angioedema, pruritus, papular rash, alterations in skin pigmentation, fever, headaches, arthralgia, lymphadenopathy, hepatomegaly, and neurological symptoms.
DIAGNOSTIC TESTS AND INTERPRETATION Laboratory
• Bancroftian and Malayan filariasis - Blood smears reveal the presence of filarial worms.
– Serological assays lack specificity in filariasis. – Eosinophilia is frequently absent.
– PCR-based assays for the DNA of W. bancrofti and B. malayi are accessible in research environments.
• Loiasis – Blood smears, skin snips, or skin biopsy
• Onchocerciasis – Microscopic examination of skin biopsies reveals the presence of worms – Dracunculiasis – Diagnosis is clinical.
• Dirofilariasis - Histological Examination
• Mansonelliasis – Blood smears reveal filarial worms.
Microscopic examination of the skin biopsy reveals the presence of worms. Eosinophilia is significant.
Imaging
• Bancroftian and Malayan filariasis — Adult worms may be observed in dilated lymphatics using ultrasound. • Onchocerciasis – Cutaneous and subcutaneous nodules identified with ultrasound and magnetic resonance imaging.
• Dracunculiasis – Standard radiography reveal calcified worms.
• Dirofilariasis – Larvae can become encapsulated within necrotic lung tissue, resulting in distinct pulmonary nodules that may be detectable on computed tomography images.
DIFFERENTIAL DIAGNOSIS
Bancroftian and Malayan filariasis include bacterial lymphangitis, thrombophlebitis, idiopathic hydrocele, congestive heart failure, cirrhosis, and nephrotic syndrome. • Loiasis
– Cutaneous larva migrans, dracunculiasis, gnathostomiasis, myiasis, onchocerciasis • Onchocerciasis – M. streptocerca, scabies, leprosy, eczema, glaucoma, loiasis • Dracunculiasis – Cutaneous larva migrans, loiasis, rat bite infection, gnathostomiasis, myiasis • Dirofilariasis – Asthma, allergies, lung cancer • Mansonelliasis – Loiasis, onchocerciasis
INITIAL THERAPEUTIC AGENT
• Bancroftian and Malayan filariasis — Wolbachia spp., a genus of Rickettsia, are essential for filarial growth. Administer Doxycycline 100 mg orally twice daily for a duration of 4 to 6 weeks to address Wolbachia. Four months subsequent to initiating treatment, a single dosage of albendazole 400 mg orally and ivermectin 150 mg/kg orally was administered.
• Loiasis - Administer a single dosage of diethylcarbamazine citrate (DEC) at 6 mg/kg orally.
• Onchocerciasis - Administer one dosage of ivermectin at 150 mcg/kg orally (ineffective against mature worms). Recur in six months.
– Administer prednisone at a dosage of 1 mg/kg/day orally one week prior to ivermectin if ocular involvement is present.
• Dracunculiasis – Gradual and meticulous removal of the protruding worm.
Metronidazole 250 mg administered orally three times daily may
Mitigate inflammatory response, hence aiding in the expulsion of worms. Mebendazole 400–800 mg each day for 6 days may eradicate the worm.
• M. perstans – Administer albendazole 400 mg orally twice daily for 10 days. • M. streptocerca and M. ozzardi – Administer a single dose of ivermectin at 200 mcg/kg. • Dirofilariasis – No effective pharmacological treatment available. Second Line
• Bancroftian and Malayan filariasis – DEC, as previously mentioned for M. streptocerca. DEC should not be administered in regions with endemic lymphatic filariasis and loiasis/onchocerciasis.
SUPPLEMENTARY THERAPY
Comprehensive Measures
The treatment primarily targets the microfilarial stage of the infection. Adult worms are seldom impacted by a single dose of medicine. Repetitive therapy is frequently required for a cure.
Concerns for Referral
• Specialists in infectious diseases • Ophthalmologist for ocular assessment in onchocerciasis
CHIRURGICAL INTERVENTIONS/ADDITIONAL PROCEDURES
• Nodulectomy of palpable nodules in onchocerciasis • Surgical excision of dirofilariasis from the lung IN-PATIENT CONSIDERATIONS
Preliminary Stabilization
Resuscitation in accordance with advanced life support protocols as necessary
Criteria for Admission
• Patients with septicemia resulting from open wounds • Overnight admission for nocturnal blood sample collection for diagnostic testing
IV Fluids • Administer fluid resuscitation using colloids, such as Gelofusine, in cases of septicemia.
• Maintenance fluids utilizing Ringer's lactate
Nursing
Patients with elephantiasis may require comprehensive nursing care for the affected body portion.
Release Criteria for the resolution of septicemia
CONTINUING CARE POST-TREATMENT RECOMMENDATIONS
Every 4 to 6 weeks for treatment evaluation and symptomatic management
Patient Surveillance
Routine ocular assessments
OUTLOOK
Disability and disfigurement are mitigated by accurate diagnosis and therapy.
COMPLICATIONS
Bancroftian filariasis - Elephantiasis; Septicemia resulting from bacterial infection of exposed sores.
• Onchocerciasis - Visual Impairment
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