Campbell later used to develop ivermectin, the drug used in MDA. It should be considered a victory in NTD awareness that such a renowned accolade was awarded to those fighting a battle that often flies below the radar.
This breakthrough provides a beacon of light for the countries who are still hoping to achieve onchocerciasis elimination and brings us one step closer to the end of the fight with this disease. The disease is commonly known as "river blindness" because the larvae of the blackfly vectors breed in fast flowing rivers.
Onchocerciasis is endemic in Africa, and in 13 foci in six countries of the Americas Brazil, Colombia, Mexico, Guatemala, Ecuador, and Venezuela , where it was introduced through the slave trade. The transmission has been interrupted or eliminated in 11 of 13 foci of the Americas.
As a result of a regional initiative, only about 28, people are still in need of continual treatment in Brazil and Venezuela Yanomami indigenous population. Furthermore, Colombia is the first country in the world to achieve the verification of Onchocerciasis elimination.
Know more. Home Topics Onchocerciasis - "River Blindness". In subcutaneous tissues the larvae develop into adult filariae, which commonly reside in nodules in subcutaneous connective tissues.
Adults can live in the nodules for approximately 15 years. Some nodules may contain numerous male and female worms. In the subcutaneous nodules, the female worms are capable of producing microfilariae for approximately 9 years.
They are occasionally found in peripheral blood, urine, and sputum but are typically found in the skin and in the lymphatics of connective tissues. A blackfly ingests the microfilariae during a blood meal. There the microfilariae develop into first-stage larvae and subsequently into third-stage infective larvae. The agent of river blindness, Onchocerca volvulus , occurs mainly in Africa, with additional foci in Latin America and the Middle East.
Onchocerciasis can cause pruritus, dermatitis, onchocercomata subcutaneous nodules , and lymphadenopathies. The most serious manifestation consists of ocular lesions that can progress to blindness. Onchocerciasis is usually diagnosed by the finding of microfilariae in skin snips or adults in biopsy specimens of skin nodules. Microfilariae of Onchocerca do not exhibit any form of periodicity and skin snips may be collected at any time.
Skin snips should be thin enough to include the outer part of the dermal palpillae but not so thick as to produce bleeding.
Skin snips should be placed immediately in normal saline or distilled water, just enough to cover the specimen. In this region, the at-risk population is the Afro-Colombian rural population dedicated to agricultural, hunting, fishing and mining activities [ 15 ].
Properly trained community health workers were responsible for the biannual distribution of treatments. This was accompanied by health education, social mobilization and community participation for 14 consecutive years. Epidemiological coverage rates were calculated after each treatment round. Interruption of O. Skin snips were taken from the right scapula and right iliac crest and examined following the same procedure as in the baseline study [ 15 ]. The microfilariae prevalence in skin snips and the community microfilarial load CMFL was obtained.
Four ophthalmological assessments were done in order to establish the magnitude of ocular damage caused by O. The first three, in baseline , and , were carried out following the criteria and procedures recommended at that time by OEPA [ 18 ].
The last one in used the definition for onchocercal punctate keratitis described in the study by Winthrop et al.
In the baseline study only persons with a microfilariae-positive skin snip were examined [ 15 , 20 ], while in the other 3 studies all persons aged 10 years or older who were present at the time of the assessment were studied. Serology was carried out in children less than 10 years of age in , and Blood samples were drawn by digital puncture with a sterile lancet.
In , capillary blood samples collected by finger prick were obtained from children and examined using Ov card tests as described by Lipner et al. After the baseline studies, three entomological assessments were carried out to evaluate the impact of the MDA. All of them were completed during the second half of the year July to December , the peak transmission season.
Several sampling sites were selected. The first two entomological studies to assess the impact of MDA on transmission were carried out in and , after four and ten treatment rounds, respectively.
In , some flies were dissected and others processed by polymerase chain reaction PCR to detect O. For the survey, the WHO guidelines [ 17 ] for entomological studies to assess the impact of MDA on transmission were followed. Collections were carried out once a month for five consecutive months between July and November The results were analyzed using the Poolscreen 2. When all the epidemiological indicators show that transmission has been interrupted, suspension of treatment is recommended and a 3-year period post-treatment surveillance is initiated in the focus [ 17 ].
Following the WHO guidelines [ 17 ], blackflies were collected in the second half of , at the end of the PTS period, for several consecutive days once a month during 4 months in the peak transmission season July to December to confirm that transmission had not recrudesced in the absence of treatments.
Up to the end of , 23 consecutive treatment rounds were carried out. Parasite surveys conducted at various time points during the ivermectin MDA showed that the prevalence of O. Prevalence of O. Prevalence of microfilariae in skin snips and community microfilarial load CMfL , Naiciona, Colombia, — However, there were considerable levels of prevalence of punctate keratitis that varied from All 21 samples from children aged up to 5 years and all 78 samples from children aged 5 to 14 years were negative in the Ov seroprevalence surveys carried out during Similarly, all serology samples from children aged from 0 to 9 years, 79 in and 64 in , were negative.
During these three surveys, the baseline of O. Evolution of Simulium exiguum s. Also, during , although the infectivity rate of flies carrying O. In , three years after MDA ended, none of the pools of S. Infectivity rate and transmission potential of Simulium exiguum s. The entomological evidence shows that after 12 years of continuous ivermectin MDA the O.
This provided the first proof of concept that elimination of onchocerciasis can be achieved by biannual MDA with ivermectin sustained for a period of 10 to 12 years. A clear decrease in prevalence and CMfL occurred as a consequence of the periodic distribution of ivermectin. However, it must be noted that only persons of 15 years or older were examined in the baseline survey in Rapid Epidemiological Assessment , while in the follow-up assessments children between 1 and 15 years, as well as adults, were examined.
Although no people were found to be positive for microfilariae in after 10 treatment rounds, this could possibly be explained by the fact that a lower number of people were examined as compared to the previous follow-up assessments. In , after 16 treatment rounds, only two adults were found to be positive for microfilariae. For different reasons, they had not received ivermectin during the previous three treatment rounds.
In none of the people examined had microfilariae positive skin snips. Before the criteria for O. In , when the updated definition was applied, no cases of punctate keratitis attributable to O. These, as well as the punctate keratitis lesions encountered in the previous assessments, were most likely of a different, non-onchocercal etiology, caused by either infections or small traumatic lesions.
Based on the results of the last ophthalmological assessment in , it was concluded that ocular morbidity attributable to O. Collectively, the seroprevalence results indicated that children were not exposed to infection by O. The results of the entomological assessment carried out in showed that transmission was successfully interrupted because the infectivity rate found in was below the threshold of 0.
Nevertheless, biannual ivermectin treatments continued mainly because, for administrative reasons, the results of the entomological assessment carried out in were not available until
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