Filarial Dance Sign in Scrotal Filarial Infection

  Lymphatic filariasis is a parasitic disease caused by filarial worms Wuchereria bancrofti and Brugia   malayi.

 Prevalence of infection -One third of the people infected with the disease live in India, Filariasis has been a known disease for thousands of years. The first documentation of this disease was found in Egyptian papyrus more than 5000 years BC.

 Etiology: Eight main species of nematodes (roundworms) can cause filariasis; however, the most common is W bancrofti (100 X 0.3 mm), followed by Brugiaorganisms.

 The nematodes can live for several years in the lymphatic vessels and lymph nodes. The female worms produce microfilariae (200-300 mm), which circulate in the blood.

 The microfilaria infects biting Culex pipiens mosquitoes (less commonly Anopheles, Aedes, and Mansonella species). It then develops into the infective filariform larvae within 1-2 weeks.

 During subsequent bites by the mosquito, the larvae infect human hosts and migrate to the lymphatic tissues, where they develop into adult worms within a year.

 

Pathophysiology: The pathologic changes in patients with filariasis are caused by adult worms, which cause lymphangiectasia.

W bancrofti adults have a predilection for periaortic, iliac, inguinal, and intrascrotal lymph vessels. . Death of the adult worms ends in a noninflammatory phase of lymphatic dilatation. However, 0granuloma formation is variable and depends on the host response. .  Fibrosis and obstruction of the scrotal lymphatic channels result in rupture of these vessels and hydrocele formation.

Lymphatic obstruction and dilatation predisposes to secondary infection, which, in turn, results in more fibrosis and obstruction.  Thus, secondary infection is the most common cofactor in the development of lymphedema and lymphangiectasia.

Microfilariae are released by adult female in the circulation according to a feedback system that maintains a constant blood level of microfilariae. The microfilariae live in the circulation for several months. Microfilariae are detected in approximately 40% of patients.

. Patients with filariasis develop higher titers of immunoglobulin E and eosinophilia. Some patients show increased immune response to the filarial infection and develop tropical eosinophilia or eosinophilic interstitial pneumonitis.

. Eosinophilic infiltrates have been found in affected lymph nodes, lungs, and around damaged microfilariae in patients with clinical and occult filariasis. Filarial lesions resemble tuberculous granulomas and may be misdiagnosed as tuberculosis.

1)50% of the population (more commonly men) may have subclinical infection and may rarely develop pathologic sequelae.

2)Filarial infections may cause fever in many patients because of their immune reactions. Patients present with episodic fever associated with lymphangitis, lymphadenitis, funiculoepididymitis (ie, inflammation of the spermatic cord and epididymis), transient edema, and small hydroceles.

3)The hallmark of clinical disease is lymphedema.The genitals and lower extremities are the areas most commonly affected. Elephantiasis of the penis and scrotum is the most common clinical problem encountered by urologists in patients with filariasis..

4)Chyluria occurs in young adult patients earlier in the disease than elephantiasis. Chyluria results from obstruction of the retroperitoneal lymphatic channels, which leads to dilatation and rupture in the urinary collecting system.

 5)Filarial hydroceles vary significantly in size. They can grow very large and may become socially unacceptable and cause significant morbidity and discomfort. Differentiating filarial hydrocele from idiopathic hydrocele is difficult in many cases.

DIAGNOSIS –

 2) IMAGING –                 

                                                    Filarial dance sign on UGS 

     The FDS was first described by Amaral andcoworkers in 1994.

    They described the movements of live adult filarial worms in the lymphatic vessels as   peculiar, random-appearing movements of objects inside vessels like structure. The worms are shown on HRUS as linear echogenic structures with persistent, random, almost tireless twirling movements.

 This sign is so striking that once it is detected on HRUS, it cannot be mistaken for anything else. FDS on HRUS correlates with active release of microfilariaeby the worms and hence indicates active infection.

 Nevertheless, ultrasonography, being the only modality that can show the adult worms, is an ideal technique for following patients receiving therapy.

Although USG was not to assess the macrofilaricidal efficacy of DEC, it found ultrasonography very useful in the follow up period to document there response of worms to the drug. Complete absence of worm movements on follow-up examination was taken as a positive response.

 

 TREATMENT- Diethylcarbamazine (DEC) is effective against both microfilariae and adult worm and is considered the drug of choice..

o      DEC does not reverse existing lymphatic damage and does not change the course of pathology in patients with established disease..

o      DEC is only partially effective against adult worms; therefore, an ultrasound scan of the scrotum 1 month after treatment will show any residual worms, which is an indication for re-treatment.

o      Recommended schedules are 6 mg/kg/d for a total of 72 mg/kg for W bancrofti and 4 mg/kg/d for a total of 60 mg/kg for B malayi.

o      DEC causes allergic reactions (Mazzotti reactions), especially in patients with high microfilarial counts. Headache, fever, nausea, vomiting, local pain, and swelling over lymph nodes and along lymphatic vessels have been reported..