Studies on the periodicity and intravascular distribution of Wuchereria bancrofti microfilariae in paired samples of capillary and venous blood from Recife, Brazil.

We examined the periodicity and intravascular distribution of Wuchereria bancrofti microfilariae (mf) and determined the effect of these parasite properties on the accuracy of blood filming and filtration methods for diagnosis of bancroftian filariasis in the endemic area of Recife, Brazil. Microfilariae in both venous and capillary blood exhibited a nocturnal periodicity pattern with a relatively high amplitude. Overall, capillary blood contained approximately 1.25 times the number of mf present at the same time in the same volume of venous blood. However, the ratio of mf present in capillary and venous blood varied over a 24-hour period, so that the fewest mf were present in the capillary bed of the skin at the time when biting activity of the local Culex vector is the lowest. Twenty or 60 microliters blood films did not reliably detect carriers with fewer than 100 or 60 mf/ml venous blood, respectively, and were thus inadequate for the identification of low density mf carriers. In contrast, all carriers with > 1 mf/20 or 60 microliters blood smear at night could be identified during daytime hours by filtration of 1 micromilligram venous blood.

Tolerance of diethylcarbamazine by microfilaraemic and amicrofilaraemic individuals in an endemic area of Bancroftian filariasis, Recife, Brazil.

To determine the tolerance to diethylcarbamazine (DEC) treatment of patients with Bancroftian filariasis, 193 individuals (138 asymptomatic microfilaraemic, 30 amicrofilaraemic diseased patients and 25 asymptomatic amicrofilaraemic endemic residents) were enrolled in a prospective trial with different dose schedules, in a hospital and outpatient clinic setting in Brazil. Systemic adverse reactions, localized adverse reactions, and side effects, related to microfilariae, adult worms and the drug itself, were evaluated. Systemic reactions occurred irrespective of the DEC dose and schedule in about 40% of the microfilariae carriers, but not in amicrofilaraemic diseased patients or residents; they usually consisted of microscopic haematuria, followed by fever and malaise. Localized reactions were manifested by the appearance of inflammatory reactions, mainly in the scrotal area. Nodules containing degenerating adult worms developed mainly in the scrotal lymphatics of microfilaraemic patients, diseased amicrofilaraemic patients, and residents. Drowsiness, which increased with higher doses of DEC, was the most common side effect in both microfilaraemic and amicrofilaraemic individuals, followed by nausea and gastric upset. The results indicate that the occurrence of systemic and local adverse reactions was unrelated to either the dose of DEC or the pretreatment microfilarial density. The severity of systemic reactions was proportional to the microfilarial density. Side effects were dependent on the drug dosage irrespective of infection status.

Wuchereria bancrofti: freeze-fracture study of the epicuticle of microfilariae.

The freeze-fracture technique was used to analyze the surface of microfilariae of Wuchereria bancrofti. The examination of thin sections showed that the epicuticle is formed by two closely apposed membrane-like structures, appearing as hepta-laminated structures. Freeze-fracture replicas revealed the presence of two fracture faces. The outer one is smooth but presents rosette-like structures. The inner face, which is in contact with the hypodermal cells, presents a large number of particles.

Immunocytochemical localization of surface antigens in microfilariae of Wuchereria bancrofti.

Antigenic sites were localized on the surface structure (sheath and cuticle) of microfilariae of Wuchereria bancrofti using sera from microfilaraemic and amicrofilaraemic patients using antibodies associated to colloidal gold particles and transmission electron microscopy. No labeling was observed on the surface of intact parasites. Microfilariae without the sheath and isolated sheath were obtained by ultrasound treatment. Using these preparations labeling of the inner portion of the sheath was observed when sera from amicrofilaraemic patients were used. Labeling of the cuticle surface was observed mainly in the regions of the cuticular annulations.

Fine structure and localization of anionic sites on the surface of microfilaria of Wuchereria bancrofti.

The fine structure of the sheath and the cuticle of microfilaria of Wuchereria bancrofti was analysed and the results obtained were compared with those from other filarial parasites. Cationized ferritin particles bind to the surface of the sheath and the epicuticle. No binding of colloidal iron hydroxyde particles to the microfilaria surface was observed. Reaction product indicative of carbohydrates containing vic-glycol groups was not observed in thin sections of microfilaria submitted to the periodic acid-thiosemicarbazide-silver proteinate technique. The results obtained are discussed in relation to previous studies using lectins.