Screening of army soldiers for Wuchereria bancrofti infection in the metropolitan Recife region, Brazil: implications for epidemiological surveillance.

Between 1989 and 1995, blood surveys were performed for Wuchereria bancrofti infection in several barracks of the Brazilian army in the metropolitan Recife region. For initial screening, 60 microliters of capillary blood were examined for microfilaria. All men who tested positive had microfilaria quantified by filtration of venous blood through a polycarbonate membrane. Of 23,773 men screened, 585 (2.5%) had microfilaria (mf). Microfilarial density ranged from < 1-8706 mf/ml of blood. Thirteen individuals had ultra-low microfilarial densities (1 mf/11 ml of blood). Characterization of 174 autochthonous cases made it possible to map 8 new districts in 4 cities within metropolitan Recife region where transmission of W. bancrofti was previously unknown. Routine screening of soldiers in the military may provide important surveillance data for national programmes to eliminate transmission of W. bancrofti.

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.

Renal abnormalities in microfilaremic patients with Bancroftian filariasis.

To determine the frequency of renal abnormalities occurring with Bancroftian filarial infections and to assess the effects of treatment on such abnormalities, we initiated a prospective, hospital-based study of 20 microfilaremic and five amicrofilaremic patients with Wuchereria bancrofti infections. Thorough clinical evaluations and detailed renal assessments were made prior to treatment and at multiple time points for 60 days following a standard twelve-day course of treatment with diethylcarbamazine (DEC). There were two important findings. First, even prior to DEC treatment, almost half of the microfilaremic patients had hematuria and/or proteinuria. Second, treatment with DEC induced these same abnormalities in almost all of the remaining microfilaremic patients. However, this DEC-induced hematuria and/or proteinuria was transient, and the long-term response to DEC in all of the microfilaremic patients was resolution of the abnormal renal findings during the two-month followup period. In the amicrofilaremic study patients, no hematuria or proteinuria was detected before, during, or after treatment with DEC.