References:
- Global Infectious Diseases and Epidemiology Online Network: Infectious Diseases of the Philippines, 2013 eBook Edition, ISBN 978-1-61755-582-4, by Stephen Berger. Accessed here.
Bancroftian Filariasis
| Agent | PARASITE - Nematoda. Phasmidea, Filariae: Wuchereria bancrofti |
| Reservoir | Human |
| Vector | Mosquito (Anopheles, Aedes, Culex) |
| Vehicle | None |
| Incubation Period | 5 to 18 months (As early or late as 1 month to 2 years) |
| Diagnostic Tests | Identification of microfilariae in nocturnal blood specimen Nucleic acid amplification Serology may be helpful |
| Typical Adult Therapy | Diethylcarbamazine: 50 mg Day 1: 50 mg TID Day 2: 100 mg TID Then 2 mg/kg TID X 18 days OR Ivermectin 200µg/kg PO as single dose. Doxycycline 200 mg daily for 8 weeks is also effective. |
| Typical Pediatric Therapy | As for adult |
| Clinical Hints | Lymphangitis, lymphadenitis, eosinophilia, epididymitis, orchitis, hydrocoele or progressive edema; episodes of fever and lymphangitis may recur over several years; chyluria occasionally encountered. |
| Synonyms | Bancroftian filariasis, Rosetta leg, Wuchereria bancrofti |
WHO Case Definition for Surveillance
Clinical case definition: Hydrocoele or lymphedema in a resident of an endemic area for which other causes of these findings have been excluded.
Laboratory criteria for diagnosis: Microfilaria positive, antigen positive or biopsy positive.
Case classification
- Suspected: Not applicable.
- Probable: A case that meets the clinical case definition.
- Confirmed: A person with laboratory confirmation even if he/she does not meet the clinical case definition.
Clinical manifestations reflect either acute inflammation or lymphatic obstruction.
- Repeated episodes of lymphangitis, lymphadenitis, fever, headache, backache and nausea may occur; and arthritis, funiculitis, epididymitis, or orchitis are common.
- In long-standing cases lymphedema or persistent adenopathy may develop.
- Hydrocoele is the most common clinical manifestation of lymphatic filariasis, and causes sexual disability.
- Hydrocoelectomy accounts for 25% of all surgical procedures performed in endemic areas of Ghana and Kenya.
- Lower limb involvement is characterized by initial pretibial pitting edema, which eventually becomes nonpitting and involves the entire leg.
- The skin of the leg or scrotum becomes thick, fissured, and warty; and ulceration and secondary infection may occur.
- Rare instances of pleural effusion, multiple subcutaneous nodules and intra-abdominal cysts are reported
- Chyluria reflects rupture of swollen lymphatics into the urinary tract. Microscopic (occasionally gross) hematuria is reported in some cases.
- Filarial granuloma may mimic testicular cancer.
Microfilariae may be found in properly timed blood specimens, hydrocoele fluid, chylous urine and organ aspirates.
- Adult worms are identified in biopsy material.
- Eosinophilia usually appears only during acute episodes of inflammation.
There is extensive evidence that endosymbiont bacteria (Wolbachia spp.) are necessary for the development of filarial larvae, and fertility of adult parasites.
- Doxycycline has proven effective in therapy, presumably through inhibition of Wolbachia spp.
Brugian Filariasis
| Agent | PARASITE - Nematoda. Phasmidea, Filariae: Wuchereria bancrofti |
| Reservoir | Human Non-human primate Cat Civet Dog |
| Vector | Mosquito (Mansonia, Aedes, Anopheles) |
| Vehicle | None |
| Incubation Period | 5 to 18 months (As early or late as 1 month to 2 years) |
| Diagnostic Tests | Identification of microfilariae in nocturnal blood specimen Nucleic acid amplification Serology may be helpful |
| Typical Adult Therapy | Diethylcarbamazine : 50 mg Day 1: 50 mg TID Day 2: 100 mg TID Then 2 mg/kg TID for 18 days OR Ivermectin 200µg/kg PO as single dose. Add Doxycycline 100 mg PO daily for 6 weeks. |
| Typical Pediatric Therapy | As for adult |
| Clinical Hints | Lymphangitis, lymphadenitis, eosinophilia, fever and progressive lower extremity edema—usually spares the knee and elbow; hydrocoele and chyluria not encountered. |
| Synonyms | Brugia malayi, Malayan filariasis |
WHO Case Definition for Surveillance
Clinical case definition: Hydrocoele or lymphedema in a resident of an endemic area for which other causes of these findings have been excluded.
Laboratory criteria for diagnosis: Microfilaria positive, antigen positive or biopsy positive.
Case classification
- Suspected: Not applicable.
- Probable: A case that meets the clinical case definition.
- Confirmed: A person with laboratory confirmation even if he/she does not meet the clinical case definition.
Additional clinical features:
- Most cases present as painful regional lymphadenopathy, occasionally with eosinophilia.
- Microscopic (occasionally gross) hematuria is reported in some cases.
- Disseminated disease may be associated with pulmonary cysts and empyema.
Bancroftian vs. Brugian Filariasis
The main clinical features which differentiate Bancroftian from Brugian filariasis are the rarity of genital lesions (hydrocoele) and chyluria in the latter.
- Edema extending above the knee is also primarily a feature of bancroftian disease.
- Abscess formation is often encountered with Brugian filariasis in Malaysia, Indonesia and Thailand; but not in India and other countries.
- Human infection by zoonotic Brugia species usually involves lymphatics of the neck, groin or axilla.