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Importance of ivermectin to human onchocerciasis: past, present, and the future  [cached]
Cupp EW,Mackenzie CD,Unnasch TR
Research and Reports in Tropical Medicine , 2011,
Abstract: Ed W Cupp1, Charles D Mackenzie2, Thomas R Unnasch31Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, USA; 2Department of Pathobiology, Michigan State University, East Lansing, MI, USA; 3Department of Global Health, University of South Florida, Tampa, FL, USAAbstract: Ivermectin (registered for human use as Mectizan ) was donated by Merck & Co Inc in 1987 for the treatment and control of human onchocerciasis ("river blindness"). This philanthropic gesture has had a remarkable effect in reducing the incidence and prevalence of this serious ocular and dermatological disease, while changing health system support for millions of people worldwide. Over 800 million doses have been given to more than 80 million people for onchocerciasis during the past 23 years. As a result, onchocerciasis has been significantly reduced in more than 25 countries, transmission has been interrupted in foci in at least 10 countries, and the disease is no longer seen in children in many formerly endemic foci. Recent communications have suggested that the drug's efficacy as the major therapeutic agent for these control and elimination programs may be threatened, but alternative interpretations for suboptimal response/resistance suggest otherwise. Current research needs and control methods by which the public health community in endemic countries may respond to resistance, should it occur in their area, are discussed, along with the continuing importance of this anthelmintic as the mainstay in onchocerciasis control programs.Keywords: Ivermectin, Onchocerca volvulus, river blindness, resistance, African Programme for Onchocerciasis Control, Onchocerciasis Elimination Program for the Americas
Importance of ivermectin to human onchocerciasis: past, present, and the future
Cupp EW , Mackenzie CD, Unnasch TR
Research and Reports in Tropical Medicine , 2011, DOI: http://dx.doi.org/10.2147/RRTM.S19477
Abstract: rtance of ivermectin to human onchocerciasis: past, present, and the future Perspectives (2778) Total Article Views Authors: Cupp EW , Mackenzie CD, Unnasch TR Published Date May 2011 Volume 2011:2 Pages 81 - 92 DOI: http://dx.doi.org/10.2147/RRTM.S19477 Ed W Cupp1, Charles D Mackenzie2, Thomas R Unnasch3 1Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, USA; 2Department of Pathobiology, Michigan State University, East Lansing, MI, USA; 3Department of Global Health, University of South Florida, Tampa, FL, USA Abstract: Ivermectin (registered for human use as Mectizan ) was donated by Merck & Co Inc in 1987 for the treatment and control of human onchocerciasis ("river blindness"). This philanthropic gesture has had a remarkable effect in reducing the incidence and prevalence of this serious ocular and dermatological disease, while changing health system support for millions of people worldwide. Over 800 million doses have been given to more than 80 million people for onchocerciasis during the past 23 years. As a result, onchocerciasis has been significantly reduced in more than 25 countries, transmission has been interrupted in foci in at least 10 countries, and the disease is no longer seen in children in many formerly endemic foci. Recent communications have suggested that the drug's efficacy as the major therapeutic agent for these control and elimination programs may be threatened, but alternative interpretations for suboptimal response/resistance suggest otherwise. Current research needs and control methods by which the public health community in endemic countries may respond to resistance, should it occur in their area, are discussed, along with the continuing importance of this anthelmintic as the mainstay in onchocerciasis control programs.
Can ivermectin mass treatments eliminate onchocerciasis in Africa?
Winnen,M.; Plaisier,A.P.; Alley,E.S.; Nagelkerke,N.J.D.; van Oortmarssen,G.; Boatin,B.A.; Habbema,J.D.F.;
Bulletin of the World Health Organization , 2002, DOI: 10.1590/S0042-96862002000500009
Abstract: objective: to elucidate the conditions in which mass treatment with ivermectin reduces the transmission of onchocerca volvulus sufficiently to eliminate infection from an african community. methods: onchosim, a microsimulation model for onchocerciasis transmission, was used to explore the implications of different treatment intervals, coverage levels and precontrol endemicities for the likelihood of elimination. findings: simulations suggested that control strategies based exclusively on ivermectin mass treatments could eliminate onchocerciasis. the duration of treatment required to eliminate infection depended heavily on the treatment programme and precontrol endemicity. in areas with medium to high levels of infection, annual mass treatments with 65% coverage for at least 25 years were necessary. model predictions suggested that durations exceeding 35 years would be required if there were much heterogeneity in exposure to vector bites and, consequently, wide individual variation in microfilaria counts. if the treatment interval were reduced from 12 to 6 months the time for completion of the programme could be more than halved and elimination could be accomplished in areas of hyperendemicity, provided that the effects of each treatment would be the same as with annual treatments. however, it was doubtful whether high coverage levels could be sustained long enough to achieve worldwide eradication. conclusion: elimination of onchocerciasis from most endemic foci in africa appears to be possible. however, the requirements in terms of duration, coverage, and frequency of treatment may be prohibitive in highly endemic areas.
Can ivermectin mass treatments eliminate onchocerciasis in Africa?  [cached]
Winnen M.,Plaisier A.P.,Alley E.S.,Nagelkerke N.J.D.
Bulletin of the World Health Organization , 2002,
Abstract: OBJECTIVE: To elucidate the conditions in which mass treatment with ivermectin reduces the transmission of Onchocerca volvulus sufficiently to eliminate infection from an African community. METHODS: ONCHOSIM, a microsimulation model for onchocerciasis transmission, was used to explore the implications of different treatment intervals, coverage levels and precontrol endemicities for the likelihood of elimination. FINDINGS: Simulations suggested that control strategies based exclusively on ivermectin mass treatments could eliminate onchocerciasis. The duration of treatment required to eliminate infection depended heavily on the treatment programme and precontrol endemicity. In areas with medium to high levels of infection, annual mass treatments with 65% coverage for at least 25 years were necessary. Model predictions suggested that durations exceeding 35 years would be required if there were much heterogeneity in exposure to vector bites and, consequently, wide individual variation in microfilaria counts. If the treatment interval were reduced from 12 to 6 months the time for completion of the programme could be more than halved and elimination could be accomplished in areas of hyperendemicity, provided that the effects of each treatment would be the same as with annual treatments. However, it was doubtful whether high coverage levels could be sustained long enough to achieve worldwide eradication. CONCLUSION: Elimination of onchocerciasis from most endemic foci in Africa appears to be possible. However, the requirements in terms of duration, coverage, and frequency of treatment may be prohibitive in highly endemic areas.
Changes In Peripheral Leukocyte And Body Fluids Of Onchocerciasis Patients Treated With Ivermectin
OU Manafa, MA Mafe, ET Idowu, MB Ajayi
African Journal of Clinical and Experimental Microbiology , 2004,
Abstract: This study evaluated the peripheral leukocyte count and the presence of microfilariae in the body fluids of onchocerciasis patients treated with ivermectin. Fifty-three patients over the age 10 years were selected from Ipogun, an onchocerciasis endemic area in Ondo State, Nigeria. Before and after treatment, all patients received a parasitologic and clinical examination that included physical examination, palpation of onchocercal nodules, assessment of microfilarial densities in iliac crest skin snips, diagnosis of concomitant parasitic infections in stool specimens and total leukocytes differential counts. Results indicated that ivermectin did not induce a decrease in the total number of peripheral leukocytes but there was a decrease in the number of eosinophils. Microfilariae were not found in increase frequency in the urine, blood and sputum, while the number of microfilariae per mg of skin snip decreased. Afr. J. Clin. Exper. Microbiol. 2004; 5 (3): 225-230
Primary motives for demand of ivermectin drug in mass distribution programmes to control onchocerciasis
Okwuoma Abanobi,Uchechukwu Chukwuocha,Celestine Onwuliri,Kenneth Opara
North American Journal of Medical Sciences , 2011,
Abstract: Background: Onchocerciasis is a disease with a spectrum of manifestations suffered by different infected people. Based on individual perceptions and manifestations presented, demand for the drug Ivermectin was due to different motives and priorities during mass distribution programmes. Subjects and Method: This study presents findings from a sample of 594 persons out of a total of 35,763 treated individuals who voluntarily demanded Ivermectin treatment during a community-based Ivermectin distribution exercise. The distribution, which took place in 2008, was mass distribution of the microfilaricide to control onchocerciasis in endemic communities of Ezinihitte in the Imo River Basin of Nigeria. The subjects who were selected by quota sampling procedure on the basis of community and gender, were asked to rank-order six plausible reasons for seeking treatment in terms of their order of importance in motivating them to demand Ivermectin. Results: “To gain treatment and prevention of Skin Problems” and “Desire to be De-wormed” ranked first and second respectively. “To gain promotion of general wellbeing” and “To improve state of vision and prevent blindness” ranked third and fourth respectively. In the fifth and sixth rank-order positions were “To prevent hanging groin” and “to prevent/relieve enlargement of the scrotum or clitoris” in that order. A test of hypothesis to determine if there was significant agreement among treated persons on the rank order of importance of their reasons for demanding Ivermectin gave a Kendall’s Coefficient of Concordance of W = 0.62, p <.001. Conclusion: The findings are interpreted within the framework of the major postulations of the health belief model with consideration to perceptions of severity of the conditions and belief that submitting to treatment will abate the perceived risk of the conditions. The role of endemicity of specific manifestations of onchocerciasis in lay assessment of risk of this disease is also discussed.
Compliance with eight years of annual ivermectin treatment of onchocerciasis in Cameroon and Nigeria
William R Brieger, Joseph C Okeibunor, Adenike O Abiose, Samuel Wanji, Elizabeth Elhassan, Richard Ndyomugyenyi, Uche V Amazigo
Parasites & Vectors , 2011, DOI: 10.1186/1756-3305-4-152
Abstract: A multi-site study in five APOC sponsored projects in Nigeria and Cameroon was undertaken to identify the socio-demographic correlates of compliance with ivermectin treatment. A total of 8,480 villagers above 9 years of age selected through a systematic random sampling from 101 communities were surveyed to ascertain their levels of compliance, by adapting APOC's standard household ivermectin survey form. Community leaders, community directed distributors (CDDs) of ivermectin and health workers were interviewed with in-depth interview guides, while focus group discussions were held with community members to help explain how socio-demographic factors might affect compliance.Eight-year compliance ranged from 0 to 8 times with 42.9% taking ivermectin between 6-8 times annually (high compliance). In bivariate analysis high compliance was positively associated with being male, over 24 years of age, having been married, not being Christian, having little or no formal education and being in the ethnic majority. These variables were also confirmed through regression analysis based on total times ivermectin was taken over the period. While these factors explained only 8% of the overall variation in compliance, ethnic status and education appeared to be the strongest factors. Those with higher education may be more mobile and harder to reach while neglect of ethnic minorities has also been documented in other programs.These findings can help managers of CDTI programmes to ensure ivermectin reaches all segments of the population equally.The community directed treatment with ivermectin (CDTI) programme of the African Programme for Onchocerciasis Controls (APOC) was established in 1995. Its goal was to put in place a sustainable drug distribution system and maintain a minimum of 65% annual population coverage with Mectizan? in endemic communities for at least 15 years, required for effective control of onchocerciasis [1-4]. Currently, CDTI is on-going in over 95,000 communities w
Interruption of Infection Transmission in the Onchocerciasis Focus of Ecuador Leading to the Cessation of Ivermectin Distribution  [PDF]
Raquel Lovato,Angel Guevara,Ronald Guderian,Roberto Proa?o,Thomas Unnasch,Hipatia Criollo,Hassan K. Hassan,Charles D. Mackenzie
PLOS Neglected Tropical Diseases , 2014, DOI: 10.1371/journal.pntd.0002821
Abstract: Introduction: A clinically significant endemic focus of onchocerciasis existing in Esmeraldas Province, coastal Ecuador has been under an ivermectin mass drug administration program since 1991. The main transmitting vector in this area is the voracious blackfly, Simulium exiguum. This paper describes the assessments made that support the decision to cease mass treatment. Methodology and Principle Findings: Thirty-five rounds of ivermectin treatment occurred between 1991–2009 with 29 of these carrying >85% coverage. Following the guidelines set by WHO for ceasing ivermectin distribution the impact on parasite transmission was measured in the two vector species by an O-150 PCR technique standard for assessing for the presence of Onchocerca volvulus. Up to seven collection sites in three major river systems were tested on four occasions between 1995 and 2008. The infectivity rates of 65.0 (CI 39–101) and 72.7 (CI 42–116) in 1995 dropped to zero at all seven collection sites by 2008. Assessment for the presence of antibodies against O. volvulus was made in 2001, 2006, 2007 and 2008 using standard ELISA assays for detecting anti-Ov16 antibodies. None of total of 1810 children aged 1–15 years (between 82 and 98% of children present in the surveyed villages) tested in the above years were found to be carrying antibodies to this antigen. These findings were the basis for the cessation of mass drug treatment with ivermectin in 2009. Significance: This fulfillment of the criteria for cessation of mass distribution of ivermectin in the only known endemic zone of onchocerciasis in Ecuador moves the country into the surveillance phase of official verification for national elimination of transmission of infection. These findings indicate that ivermectin given twice a year with greater than 85% of the community can move a program to the final stages of verification of transmission interruption.
Drawing and interpreting data: Children's impressions of onchocerciasis and community-directed treatment with ivermectin (CDTI) in four onchocerciasis endemic countries in Africa  [cached]
Mary Amuyunzu-Nyamongo,Yolande Flore Longang Tchounkeu,Rahel Akumu Oyugi,Asaph Turinde Kabali
International Journal of Qualitative Studies on Health & Well-Being , 2011, DOI: 10.3402/qhw.v6i2.5918
Abstract: Although the depiction of a child leading a blind man is the most enduring image of onchocerciasis in Africa, research activities have hardly involved children. This paper aims at giving voice to children through drawings and their interpretation. The study was conducted in 2009 in Cameroon, Democratic Republic of Congo (DRC), Nigeria and Uganda. Children aged 6–16 years were asked to draw their perceptions of onchocerciasis and community-directed treatment with ivermectin (CDTI) in their communities. A total of 50 drawings were generated. The drawings depicted four main aspects of onchocerciasis: (1) the disease symptoms, (2) the negative consequences of onchocerciasis among children and in the community generally, (3) the ivermectin distribution process, and (4) the benefits or effects of taking ivermectin. Out of the 50 drawings, 30 were on symptoms, 7 on effects of the disease on children, 8 on distribution process, and 5 represented multiple perceptions on symptoms, drug distribution processes, benefits, and effects of treatment. The lack of clarity when treatment with ivermectin can be stopped in endemic areas requires working with children to ensure continued compliance with treatment into the future. Children's drawings should be incorporated into health education interventions.
Impact of long-term treatment of onchocerciasis with ivermectin in Kaduna State, Nigeria: first evidence of the potential for elimination in the operational area of the African Programme for Onchocerciasis Control
Afework Tekle, Elizabeth Elhassan, Sunday Isiyaku, Uche V Amazigo, Simon Bush, Mounkaila Noma, Simon Cousens, Adenike Abiose, Jan H Remme
Parasites & Vectors , 2012, DOI: 10.1186/1756-3305-5-28
Abstract: In 2008, an epidemiological evaluation using skin snip parasitological diagnostic method was carried out in two onchocerciasis foci, in Birnin Gwari Local Government Area (LGA), and in the Kauru and Lere LGAs of Kaduna State, Nigeria. The survey was undertaken in 26 villages and examined 3,703 people above the age of one year. The result was compared with the baseline survey undertaken in 1987.The communities had received 15 to 17 years of ivermectin treatment with more than 75% reported coverage. For each surveyed community, comparable baseline data were available. Before treatment, the community prevalence of O. volvulus microfilaria in the skin ranged from 23.1% to 84.9%, with a median prevalence of 52.0%. After 15 to 17 years of treatment, the prevalence had fallen to 0% in all communities and all 3,703 examined individuals were skin snip negative.The results of the surveys confirm the finding in Senegal and Mali that ivermectin treatment alone can eliminate onchocerciasis infection and probably disease transmission in endemic foci in Africa. It is the first of such evidence for the APOC operational area.Onchocerciasis is a vector-borne parasitic disease caused by the filarial worm Onchocerca volvulus. The disease is endemic in Central and South America and the Yemen but 99% of the disease occurs in sub Saharan Africa, where it causes blindness and skin disease [1]. It is a disabling disease that causes significant morbidity, psychosocial problems and reduced work, especially reduced agricultural productivity in populations affected by the disease. About 37 million people in tropical Africa and 140,000 others in Latin America are infected with O. volvulus [1,2]. In many endemic countries including Nigeria, onchocerciasis constitutes a major public health and socio-economic problem because of its dermal and ocular manifestations. The main strategy for control in endemic countries is by mass ivermectin (Mectizan?) distribution. Following the availability of iverme
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