From the Guidelines
The urine filaria test is not a recommended diagnostic method for lymphatic filariasis, as the evidence suggests that nocturnal blood microscopy is the preferred investigation method 1. When diagnosing lymphatic filariasis, it is essential to consider the prepatent period, which is the time it takes for microfilariae to appear in the blood, and the incubation period, which is the time it takes for clinical symptoms to develop. According to the UK guidelines for the investigation and management of eosinophilia in returning travellers and migrants 1, the prepatent period for Wuchereria bancrofti is 7-8 months, and for Brugia malayi, it is 2 months. The clinical presentation of lymphatic filariasis can vary, but most infections are initially asymptomatic, causing lymphatic damage nevertheless. The mode of transmission is through the bite of mosquitoes, including Aedes spp., Anopheles spp., and Culex. Some key points to consider when investigating lymphatic filariasis include:
- The distribution of the disease, which is endemic in parts of Africa, West Pacific, and Caribbean, with sporadic cases in South America, India, and SE Asia 1
- The clinical presentation, which can include acute fever, localized skin inflammation, lymphadenitis, and lymphangitis, followed by chronic lymphoedema and scrotal oedema/hydrocoele 1
- The treatment, which involves specialist input and the use of diethylcarbamazine (DEC) and doxycycline, with the recommended dose being DEC 6 mg/kg in 3 divided doses for 14 days, plus doxycycline 200 mg daily for 6 weeks 1 It is crucial to exclude onchocerciasis and loiasis if the patient has traveled to co-endemic areas, and to seek expert advice in cases of co-infection. The investigation of choice is serology and nocturnal blood microscopy, which involves collecting 20 ml of blood in 4x citrated blood bottles between 10 pm and 2 am, without refrigeration 1.
From the Research
Urine Filaria Test
- The urine filaria test is not a commonly discussed method for diagnosing filariasis, as the traditional method involves examining blood or skin samples for microfilariae 2.
- However, a study reported two cases of filariasis where microfilaria were found in kidney biopsy, and the patients presented with renal symptoms such as passage of milky urine and gross hematuria 3.
- In these cases, urine examination revealed nephrotic range proteinuria, but the diagnosis of filariasis was made through kidney biopsy, which is a rare method for diagnosing the disease 3.
- Other diagnostic methods for filariasis include antigen detection, radiographic imaging, and polymerase chain reaction, but urine tests are not typically mentioned as a primary diagnostic tool 2, 4.
- The Global Programme to Eliminate Lymphatic Filariasis recommends mass treatment with albendazole, diethylcarbamazine, and ivermectin, but the effectiveness of these treatments in reducing microfilarial levels is still being studied 5, 6.