[
Rev Latinoam Microbiol
]
Onchocerciasis is one of the major causes of blindness in the World, with about 17.7 million infected, particularly in West Africa. In Mexico, onchocerciasis is also present and has been subjected to control since 1923. The standard diagnosis of onchocerciasis is by the detection of microfilariae by skin biopsy and transmission is evaluated by detection of Onchocerca volvulus larvae in the vector. Classically, this was carried out by manual dissection of Simuliumn ochraceun s.l. However, with the use of ivermectin, a drug that kills microfilariae but not the adult worms, the skin biopsy is becoming no longer useful for detecting microfilariae levels and due to the reduced transmission, fly dissection is no longer viable. The subject of this paper is to present the immunological and molecular techniques developed to supersede the skin biopsy and fly dissection, and their diagnostic ability to assess the impact of multiple bi-annual mass ivermectin treatments on O. volvulus transmission in Mexico.
[
Adv Parasitol,
2011]
Onchocerciasis has historically been one of the leading causes of infectious blindness worldwide. It is endemic to tropical regions both in Africa and Latin America and in the Yemen. In Latin America, it is found in 13 foci located in 6 different countries. The epidemiologically most important focus of onchocerciasis in the Americas is located in a region spanning the border between Guatemala and Mexico. However, the Amazonian focus straddling the border of Venezuela and Brazil is larger in overall area because the Yanomami populations are scattered over a very large geographical region. Onchocerciasis is caused by infection with the filarial parasite Onchocerca volvulus. The infection is spread through the bites of an insect vector, black flies of the genus Simulium. In Africa, the major vectors are members of the S. damnosum complex, while numerous species serve as vectors of the parasite in Latin America. Latin America has had a long history of attempts to control onchocerciasis, stretching back almost 100 years. The earliest programmes used a strategy of surgical removal of the adult parasites from affected individuals. However, because many of the adult parasites lodge in undetectable and inaccessible areas of the body, the overall effect of this strategy on the prevalence of infection was relatively minor. In 1988, a new drug, ivermectin, was introduced that effectively killed the larval stage (microfilaria) of the parasite in infected humans. As the microfilaria is both the stage that is transmitted by the vector fly and the cause of most of the pathologies associated with the infection, ivermectin opened up a new strategy for the control of onchocerciasis. Concurrent with the use of ivermectin for the treatment of onchocerciasis, a number of sensitive new diagnostic tools were developed (both serological and nucleic acid based) that provided the efficiency, sensitivity and specificity necessary to monitor the decline and eventual elimination of onchocerciasis as a result of successful control. As a result of these advances, a strategy for the elimination of onchocerciasis was developed, based upon mass distribution of ivermectin to afflicted communities for periods lasting long enough to ensure that the parasite population was placed on the road to local elimination. This strategy has been applied for the past decade to the foci in Latin America by a programme overseen by the Onchocerciasis Elimination Program for the Americas (OEPA). The efforts spearheaded by OEPA have been very successful, eliminating ocular disease caused by O. volvulus, and eliminating and interrupting transmission of the parasite in 8 of the 13 foci in the region. As onchocerciasis approaches elimination in Latin America, several questions still need to be addressed. These include defining an acceptable upper limit for transmission in areas in which transmission is thought to have been suppressed (e.g. what is the maximum value for the upper bound of the 95% confidence interval for transmission rates in areas where transmission is no longer detectable), how to develop strategies for conducting surveillance for recrudescence of infection in areas in which transmission is thought to be interrupted and how to address the problem in areas where the mass distribution of ivermectin seems to be unable to completely eliminate the infection.
[
Cell,
1996]
Anyone who has watched an early embryo develop cannot help but be awed by the choreography of the early cleavages. The orientation and timing of cleavage in an animal cell are always such that the cleavage furrow bisects the mitotic apparatus (MA) during telophase, thus ensuring the equal partitioning of daughter chromosomes. In addition, the regulation of cleavage plane orientation is necessary for correct partitioning of localized determinants to specific daughter cells, for optimal positioning of cells in developing embryos, and for morphogenesis in plants, which are not motile.
[
Science,
1998]
The Caenorhabditis elegans genome sequence was surveyed for transcription factor and signaling gene families that have been shown to regulate development in a variety of species. About 10 to 25 percent of the genes in most of the gene families already have been genetically analyzed in C. elegans, about half of the genes detect probable orthologs in other species, and about 10 to 25 percent of the genes are, at present, unique to C. elegans. Caenorhabditis elegans is also missing genes that are found in vertebrates and other invertebrates. Thus the genome sequence reveals universals in developmental control that are the legacy of metazoan complexity before the Cambrian explosion, as well as genes that have been more recently invented or lost in particular phylogenetic lineages.AD - Department of Molecular Biology, Massachusetts General Hospital, Department of Genetics, Harvard Medical School, Boston, MA 02114, USA. ruvkun@frodo.mgh.harvard.eduFAU - Ruvkun, GAU - Ruvkun GFAU - Hobert, OAU - Hobert OLA - engPT - Journal ArticlePT - ReviewPT - Review, TutorialCY - UNITED STATESTA - ScienceJID - 0404511RN - 0 (Helminth Proteins)RN - 0 (Transcription Factors)SB - IM