313 Am. J. Trop. Med. Hyg., 58(3), 1998, pp. 313–315 Copyright  1998 by The American Society of Tropical Medicine and Hygiene APPLICATION OF THE ENZYME-LINKED IMMUNOELECTROTRANSFER BLOT TO FILTER PAPER BLOOD SPOTS TO ESTIMATE SEROPREVALENCE OF CYSTICERCOSIS IN BOLIVIA HASAN S. JAFRI, FAUSTINO TORRICO, JOHN C. NOH, RALPH T. BRYAN, FANOR BALDERRAMA, JOY B. PILCHER, AND VICTOR C. W. TSANG Division of Pediatric Infectious Diseases, The University of Texas Southwestern Medical Center, Dallas, Texas; Universidad Mayor de San Simon, Facultad de Medicina, Cochabamba, Bolivia; Division of Parasitic Diseases, Immunology Branch, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia; Centers for Disease Control and Prevention, Hantavirus Project, Indian Health Service-Headquarters West, Epidemiology Branch, Albuquerque, New Mexico Abstract. An enzyme-linked immunoelectrotransfer blot (EITB) assay was used to study the prevalence of cys- ticercosis in rural Bolivia. Dried blood spots on filter paper from fingersticks were used as assay samples. Before the serosurvey, experiments were performed to show that samples eluted from dried whole blood on filter paper exhibited no decrease in sensitivity when compared with the more traditional serum samples used in the EITB. Fingerstick blood dried on filter paper is a convenient, economical way of transporting and storing field samples for epidemiologic surveys of cysticercosis in developing countries. This report shows the utility of this sample collection method in underdeveloped countries where refrigeration is not possible and where venipuncture is a problem. Blood was obtained from randomly selected residents in three rural regions of Bolivia: Chuquisaca (n = 1,859), Cochabamba (n = 1,516), and Tarija (n = 1,010). The estimated seroprevalence on 10% of the sample collected for the three regions were 9%, 4.5%, and 2%, respectively. Cysticercosis is caused by infection of tissues by the lar- val stages of Taenia solium. The disease is clinically di- verse because cysts can occur in virtually any anatomic location. Neurocysticercosis is the most commonly recog- nized manifestation. In addition to taeniasis, an intestinal infection by the adult tapeworm, cysticercosis is endemic throughout the developing world where swine husbandry practices and human consumption of inadequately cooked pork favor transmission. In South America, neurocysticer- cosis is a major cause of morbidity creating the loss of huge amounts of resources every year. 1 Recent studies in Peru and Mexico, for example, have demonstrated seropreval- ences ranging from 8% to 12%, and have confirmed that neurocysticercosis is a major cause of neurologic morbidity in those countries. 2–7 In Bolivia, unpublished data from surveys performed in the altiplano region indicate that the seroprevalence of cys- ticercosis in some communities ranges from 10% to 19%. Observed pork consumption and pig husbandry practices in these regions suggest that taeniasis/cysticercosis disease may be a significant, but largely unrecognized, public health problem. In this study, we examined the seroprevalence of cysticercosis in the Bolivian regions of Tarija, Chuquisaca, and Cochabamba. In addition to estimating the seroprevalence of human cysticercosis in Bolivia, this study evaluated blood collec- tion in the form of dried blood spots on filter paper and found that many of the problems of collecting, processing, and transporting blood samples for serologic surveys can be overcome by the use of small volumes of blood col- lected by finger stick and dried onto filter paper. This sim- ple technique negates difficulties in cold-chain transport of serum or plasma as well as cultural problems associated with venipuncture. Various filter paper methods have been in use for many years for other assays. 8–11 The present re- port shows the utility of this sample collection method in an enzyme-linked immunoelectrotransfer blot (EITB) assay for cysticercosis. MATERIALS AND METHODS Filter paper samples preparation. All samples were col- lected by finger stick and spotted onto Whatman (Clifton, NJ) #1 filter paper. The filter papers were air-dried and stored at ambient temperature until use. For testing, 7.0-mm disks were punched out of the center of each dried blood spot and placed into 500 l of phosphate-buffered saline/Tween 20/azide (0.10 M NaCl, 0.05 M Na 2 PO 4, pH 7.2, with 0.3% [v/v] Tween 20 and 0.1% [w/v] NaN 3 ). Samples were soni- cated (Waterbath Sonicator Model #B-12; Branson, Shelton, CT) for 15 min continuously. Eluted samples can be stored until needed after sonication in PBS/Tween 20/azide at -20°C. The volume of dried blood on a 7.0-mm disk of filter paper was approximately equal to 3.5 l of liquid whole blood. Patient study. All samples used in this study were part of an infectious disease survey sample archive collected in the early 1990s under the aegis of the Bolivian Ministry of Health, in accordance with its human subjects policies. All samples were tested in the present study with no patient identification. Fingerstick blood samples were obtained from 1,859 residents from the region of Chuquisaca, 1,010 resi- dents from Tarija, and 1,516 from Cochabamba. Ten percent of these samples were randomly selected from each of the three regions (yielding 186 samples from Chuquisaca, 101 from Tarija, and 158 from Cochabamba), and tested for an- tibodies to cysticercosis. The EITB using filter paper samples. The EITB assay for T. solium-specific antibodies was performed as previous- ly described. 12 Briefly, seven lentil-lectin purified T. solium glycoprotein antigens were used in an EITB format to detect infection-specific antibodies eluted from the whole blood spots. Each sonicated eluent was diluted with an equal vol- ume of PBS/Tween 20/10% nonfat dry milk and mixed well before use as the antibody source. Antibody reactions against these glycoproteins were visualized with the H 2 O 2 /diaminob-