Volume 71, Issue 5
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645


The objective of this study was to examine nodules from Mexico, Guatemala, and Ecuador collected over a one-year period (2001) to determine the effects of semi-annual ivermectin treatments on macrofilarial populations. Nodules were sectioned, stained with hematoxylin and eosin, and histologic findings were compared between countries and with historical data prior to the introduction of ivermectin into the region. Nodules from Ecuador had 10 times more dead or moribund worms than the historical control (66.6% versus 6.5%); nodules from patients from Mexico and Guatemala did not differ from the control. More than 80% of the female worms in each country were uninseminated and producing unfertilized oocytes. Nodules containing males differed in each country from the historical control ( < 0.0001), with presence of males ranging from 19.7% in Mexico to 13.6% in Ecuador versus 73% in the control. Nodules with females producing active microfilariae ranged from 7.8% (Mexico) to 2.7% (Ecuador) versus 60% in the historical control ( < 0.0001). Nodules from Ecuador and Mexico were significantly smaller in size than those from Guatemala or historical controls ( < 0.0005). These results depict a deteriorating condition of adult populations in Mexico, Guatemala and Ecuador, indicating that semi-annual ivermectin treatment of ≥6 years has had a profound effect on survival and reproduction of this species.


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  1. Richards F, Boatin B, Saurebrey M, Sékétéli A, 2001. Control of onchocerciasis today: status and challenges. Trends Parasitol 17 : 558–563. [Google Scholar]
  2. Blanks J, Richards F, Beltran F, Collins R, Alvarez E, Zea-Flores G, Bauler B, Cedillos R, Heisler M, Brandling-Bennett D, Baldwin W, Bayona M, Klein R, Jacox M, 1998. The Onchocerciasis Elimination Program of the Americas: a history of partnership. Pan Am. J Public Health 3 : 367–374. [Google Scholar]
  3. Cupp EW, Ochoa O, Collins RC, Cupp MS, Gonzales-Peralta C, Castro J, Zea-Flores G, 1992. The effects of repetitive community-wide ivermectin treatment on transmission of Onchocerca volvulus in Guatemala. Am J Trop Med Hyg 47 : 170–180. [Google Scholar]
  4. Collins RC, Lehmann T, Viera Garcia JC, Guderian RH, 1995. Vector competence of Simulium exiguum for Onchocerca volvulus: implications for the epidemiology of onchocerciasis. Am J Trop Med Hyg 52 : 213–218. [Google Scholar]
  5. Duke BOL, Zea-Flores G, Castro J, Cupp EW, Munoz B, 1991. Comparison of the effects of a single dose and four six-monthly doses of ivermectin on adult Onchocerca volvulus. Am J Trop Med Hyg 45 : 132–137. [Google Scholar]
  6. Anonymous, 2002. Onchocerciasis (river blindness). Report from the eleventh InterAmerican conference on onchocerciasis, Mexico City. Wkly Epidemiol Rec 77 : 249–253. [Google Scholar]
  7. Albiez EJ, Büttner DW, Duke BO, 1988. Diagnosis and extirpation of nodules in human onchocerciasis. Trop Med Parasitol 39 (Suppl. 4): 331–346. [Google Scholar]
  8. Boussinesq M, Gardon J, Kamgno J, Demanga-Ngangues, Pion SD, Duke BO, 2001. Studies on the macrofilarial population of Onchocerca volvulus in hyperendemic villages of the central province of Cameroon. Ann Trop Med Parasitol 95 : 379–388. [Google Scholar]
  9. Duke BO, Zea-Flores G, Gannon RT, 1990. On the reproductive activity of the female Onchocerca volvulus. Trop Med Parasitol 41 : 387–402. [Google Scholar]
  10. Duke BOL, Zea-Flores G, Castro J, Cupp EW, Muñoz B, 1990. Effects of multiple monthly doses of ivermectin on adult Onchocerca volvulus. Am J Trop Med Hyg 43 : 657–664. [Google Scholar]
  11. Guderian RH, Anselmi M, Espinel M, Mancero T, Rivadeneira G, Proano R, Calvopina HM, Vieira JC, Cooper PJ, 1997. Successful control of onchocerciasis with community-based ivermectin distribution in the Rio Santiago focus in Ecuador. Trop Med Int Health 2 : 982–988. [Google Scholar]
  12. Trpis M, Childs JE, Fryauff DJ, Greene BM, Williams PN, Munoz BE, Pacque MC, Taylor HR, 1990. Effect of mass treatment of a human population with ivermectin on transmission of Onchocerca volvulus by Simulium yahense in Liberia, west Africa. Am J Trop Med Hyg 42 : 148–156. [Google Scholar]
  13. Kläger SL, Whitworth JAG, Downham MD, 1996. Viability and fertility of adult Onchocerca volvulus after 6 years of treatment with ivermectin. Trop Med Int Health 1 : 581–589. [Google Scholar]
  14. Chavasse DC, Whitworth JAG, Lemoh PA, Bennett S, Davies JB, 1995. Low level ivermectin coverage and the transmission of onchocerciasis. Trans R Soc Trop Med Hyg 89 : 534–537. [Google Scholar]
  15. Karam M, Schulz-Key H, Remme J, 1987. Population dynamics of Onchocerca volvulus after 7 to 8 years of vector control. Acta Trop 44 : 445–457. [Google Scholar]
  16. Gardon J, Boussinesq M, Kamgno J, Gardon-Wendel M, Demanga-Ngangue, Duke BO, 2002. Effects of standard and high doses of ivermectin on adult worms of Onchocerca volvulus: a randomised controlled trial. Lancet 360 : 203–210. [Google Scholar]
  17. Kläger S, 1988. Investigations of enzymatically isolated male Onchocerca volvulus: qualitative and quantitative aspects of spermatogenesis. Trop Med Parasitol 39 : 441–445. [Google Scholar]
  18. Walsh JF, Davies JB, Cliff B, 1981. World Health Organization Onchocerciasis Control Programme in the Volta River Basin. Laird M, ed. Blackflies. The Future for Biological Methods in Integrated Control. New York: Academic Press, 85–103.
  19. Schulz-Key H, Karam M, 1986. Periodic reproduction of Onchocerca volvulus. Parasitol Today 2 : 284–286. [Google Scholar]
  20. Schulz-Key H, 1990. Observations on the reproductive biology of Onchocerca volvulus. Acta Leiden 59 : 27–43. [Google Scholar]
  21. Plaisier AP, van Oortmarssen GJ, Remme J, Habbema JD, 1991. The reproductive lifespan of Onchocerca volvulus in west African savanna. Acta Trop 48 : 271–284. [Google Scholar]
  22. Chavasse DC, Post RJ, Davies JB, Whitworth JAG, 1993. Absence of sperm from the seminal receptacle of female Onchocerca volvulus following multiple doses of ivermectin. Trop Med Parasitol 44 : 155–158. [Google Scholar]
  23. Lok JB, Knight DH, Selavka CM, Eynard J, Zhang Y, Bergman RN, 1995. Studies of reproductive competence in male Dirofilaria immitis treated with milbemycin oxime. Trop Med Parasitol 46 : 235–240. [Google Scholar]
  24. Guevara AG, Vieira JC, Lilley BG, Lopez A, Vieira N, Rumbea J, Collins R, Katholi CR, Unnasch TR, 2003. Entomological 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. [Google Scholar]
  25. Rodriguez-Perez MA, Lilley BG, Dominguez-Vazquez 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. [Google Scholar]
  26. Darge K, Troeger J, Engelke C, Leichsenring M, Nelle M, Awadzi K, Buettner DW, 1994. Evaluation of ultrasonography for the detection of drug-induced changes in onchocercal nodules. Am J Trop Med Hyg 51 : 800–808. [Google Scholar]

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  • Received : 24 Mar 2004
  • Accepted : 29 Apr 2004

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