Volume 74, Issue 5
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645


Measuring transmission of a vector-borne infection is essential to understanding infection dynamics. When infection prevalence in the vector population is low, transmission is often measured by pool screening (also referred to as group testing). Several investigators have developed statistical methods to recover infection prevalence estimates from pool screen data. These are based on models that contain certain assumptions, and a pool screening approach must be designed to take these into account if accurate estimates of infection prevalence are to be obtained. Here we describe these assumptions and discuss appropriate sampling protocols. The sources of error inherent in pool screening are described, and we show that, under most conditions in which one would want to use group testing, most of the error results from sampling and not the pooling process. Issues involved in developing a sampling protocol, including the total number of insects to be screened and optimal pool size, are explored. The meaning of confidence intervals associated with prevalence estimates and the appropriate interpretation of these intervals are discussed.


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  1. Nasci RS, Mitchell CJ, 1996. Arbovirus titer variation in field-collected mosquitoes. J Am Mosq Contr Assoc 12 : 167–171.
  2. Gu W, Lampman R, Novak RJ, 2003. Problems in estimating mosquito infection rates using minimum infection rate. J Med Entomol 40 : 595–596.
  3. Chiang CL, Reeves WC, 1962. Statistical estimation of virus infection rates in mosquito vector populations. Am J Hyg 75 : 377–391.
  4. Thompson KH, 1962. Estimation of the proportion of vectors in a natural population of insects. Biometrics 18 : 568–578.
  5. Burrows PM, 1987. Improved estimation of pathogen transmission rates by group testing. Phytopathology 77 : 363–365.
  6. Katholi CR, Toé L, Merriweather A, Unnasch TR, 1995. Determining the prevalence of Onchocerca volvulus infection in vector populations by PCR screening of pools of black flies. J Infect Dis 172 : 1414–1417.
  7. Barker JT, 2000. Statistical estimators of infection potential based on PCR pool screening with unequal pool sizes. PhD thesis, Department of Biostatistics, University of Alabama at Birmingham, Birmingham, AL.
  8. Hepworth G, 1996. Exact confidence intervals for proportions estimated by group testing. Biometrics 52 : 1134–1146.
  9. Rodríguez-Pérez MA, Danis-Lozano R, Rodríguez MH, Unnasch TR, Bradley JE, 1999. Detection of Onchocerca volvulus infection in Simulium ochraceum sensu lato: Comparison of a PCR assay and fly dissection in a mexican hypoendemic community. Parasitol 119 : 613–619.
  10. Yamèogo L, Toè L, Hougard J-M, Boatin BA, Unnasch TR, 1999. Pool screen PCR for estimating the prevalence of Onchocerca volvulus infection in simulium damnosum sensu lato: Results of a field trial in an area subject to successful vector control. Am J Trop Med Hyg 60 : 124–128.
  11. Williams SA, Laney SJ, Bierwert LA, Saunders LJ, Boakye DA, Fischer P, Goodman D, Helmy H, Hoti SL, Vasuki V, Lammie PJ, Plichart C, Ramzy RM, Ottesen EA, 2002. Development and standardization of a rapid, PCR-based method for the detection of Wuchereria bancrofti in mosquitoes, for xeno-monitoring the human prevalence of Bancroftian filariasis. Ann Trop Med Parasitol 96 : S41–S46.
  12. Goodman DS, Orelus JN, Roberts JM, Lammie PJ, Streit TG, 2003. PCR and mosquito dissection as tools to monitor filarial infection levels following mass treatment. Filaria J 2 : 11.
  13. Guevara AG, Vieira JC, Lilley BG, López A, Vieira N, Rumbea J, Collins R, Unnasch TR, 2003. Entomolological evaluation by pool screen polymerase chain reaction of Onchocerca volvulus transmission in Ecuador following mass Mectizan distribution. Am J Trop Med Hyg 68 : 222–227.
  14. Helmy H, Fischer P, Farid HA, Bradley MH, Ramzy RM, 2004. Test strip detection of Wuchereria bancrofti amplified DNA in wild-caught Culex pipiens and estimation of infection rate by a pool screen algorithm. Trop Med Int Health 9 : 158–163.
  15. Vasuki V, Hoti SL, Sadanandane C, Jambulingam P, 2003. A simple and rapid DNA extraction method for the detection of Wuchereria bancrofti infection in the vector mosquito, Culex quinquefasciatus by Ssp 1 PCR assay. Act Trop 86 : 109–114.
  16. Armstrong P, Borovsky D, Shope RE, Morris CD, Mitchell CJ, Karabatsos N, Komar N, Spielman A, 1995. Sensitive and specific colorimetric dot assay to detect eastern equine encephalomyelitis viral RNA in mosquitoes (diptera: Culicidae) after polymerase chain reaction amplification. J Med Entomol 32 : 42–52.
  17. Lanciotti RS, Kerst AJ, Nasci RS, Godsey MS, Mitchell CJ, Savage HM, Komar N, Panella NA, Allen BC, Volpe KE, Davis BS, Roehrig JT, 2000. Rapid detection of West Nile virus from human clinical specimens, field-collected mosquitoes, and avian samples by a Taqman reverse transcriptase-PCR assay. J Clin Microbiol 38 : 4066–4071.
  18. Hadfield TL, Turell M, Dempsey MP, David J, Park EJ, 2001. Detection of West Nile virus in mosquitoes by RT-PCR. Mol Cell Probes 15 : 147–150.
  19. White DJ, Kramer LD, Backenson PB, Lukacik G, Johnson G, Oliver J, Howard JJ, Means RG, Eidson M, Gotham I, Kulasekera V, Campbell S, 2001. Mosquito surveillance and polymerase chain reaction detection of West Nile virus, New York state. Emerg Infect Dis 7 : 643.
  20. Blyth CR, Still HA, 1983. Binomial confidence intervals. J Am Stat Assoc 78 : 108–116.
  21. Rodríguez-Pérez MA, Lilley BG, Domínguez-Vázquez A, Segura-Arenas R, Lizarazo-Ortega C, Mendoza-Herrera A, Reyes-Villanueva F, Unnasch TR, 2004. Polymerase chain reaction monitoring of transmission of Onchocerca volvulus in two endemic states in Mexico. Am J Trop Med Hyg 70 : 38–45.
  22. Ryan JR, Dave K, Collins KM, Hochberg L, Sattabongkot J, Coleman RE, Dunton RF, Bangs MJ, Mbogo CM, Cooper RD, Schoeler GB, Rubio-Palis Y, Magris M, Romer LI, Padilla N, Quakyi IA, Bigoga J, Leke RG, Akinpelu O, Evans B, Walsey M, Patterson P, Wirtz RA, Chan AS, 2002. Extensive multiple test centre evaluation of the Vectest malaria antigen panel assay. Med Vet Entomol 16 : 321–327.
  23. Nasci RS, Gottfried KL, Burkhalter KL, Ryan JR, Emmerich E, Dave K, 2003. Sensitivity of the Vectest antigen assay for Eastern Equine Encephalitis and Western Equine Encephalitis viruses. J Am Mosq Cont Assoc 19 : 440–444.
  24. Chiles RE, Green EN, Fang Y, Goddard L, Roth A, Reisen WK, Scott TW, 2004. Blinded laboratory comparison of the in situ enzyme immunoassay, the Vectest wicking assay, and a reverse transcription-polymerase chain reaction assay to detect mosquitoes infected with West Nile and St. Louis encephalitis viruses. J Med Entomol 41 : 539–544.
  25. Santos-Ciminera PD, Achee NL, Quinnan GV Jr, Roberts DR, 2004. Use of polymerase chain reaction technique to confirm Vectest screening results in Plasmodium falciparum and Plasmodium vivax vk 210 laboratory-infected Anopheles stephensi mosquitoes. J Am Mosq Cont Assoc 20 : 265–271.
  26. Anonymous, 2005. Ramp West Nile virus test package insert. Burnaby, British Columbia, Canada: Response Biomedical Corporation.
  27. Basanez MG, Rodriguez-Perez MA, Reyes-Villanueva F, Collins RC, Rodriguez MH, 1998. Determination of sample sizes for the estimation of Onchocerca volvulus (filarioidea: Onchocercidae) infection rates in biting populations of Simulium ochraceum s.L. (diptera: Simuliidae) and its application to ivermectin control programs. J Med Entomol 35 : 745–757.
  28. Casella G, Berger RL, 2002. Statistical Inference. Duxbury, Thomson Learning Group.

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  • Received : 19 Aug 2005
  • Accepted : 13 Jan 2006

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