{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,4]],"date-time":"2025-11-04T15:31:42Z","timestamp":1762270302651},"reference-count":0,"publisher":"Cambridge University Press (CUP)","issue":"2","license":[{"start":{"date-parts":[[2000,2,1]],"date-time":"2000-02-01T00:00:00Z","timestamp":949363200000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/www.cambridge.org\/core\/terms"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Parasitology"],"published-print":{"date-parts":[[2000,2]]},"abstract":"<jats:p>The compatibility between sympatric and allopatric combinations of <jats:italic>Onchocerca volvulus<\/jats:italic>\u2013anthropophilic species of \nSimulium was studied in the north-eastern focus of human onchocerciasis as well as in a densely populated locality of the \nAmazonas State in Venezuela. The objectives were to test the conjecture that local adaptation exists between the parasite \nand its vectors (the <jats:italic>Onchocerca<\/jats:italic>\u2013<jats:italic>Simulium<\/jats:italic> complex hypothesis), and assess the possibility of the infection spreading from \nits present distributional range. For the homologous combination, <jats:italic>O. volvulus<\/jats:italic>\u2013<jats:italic>S. metallicum<\/jats:italic> cytospecies E in Anzo\u00e1tegui \nState (north-eastern focus), parasite yield was 45% in contrast to 1% for the heterologous, southern parasite\u2013<jats:italic>S. metallicum<\/jats:italic> \ninfection. This was significantly lower than the parasite yield (4\u201310%) expected after allowing for the effect of density-dependent limitation of infective larval output described in this paper for <jats:italic>S. metallicum<\/jats:italic>. The population of <jats:italic>S. exiguum s.l.<\/jats:italic> \nfrom southern Venezuela allowed no larval development beyond the L1 stage of either northern or southern parasites. \nMechanisms for such refractoriness probably operate at the level of the thoracic muscles, not affecting microfilarial uptake \nor migration out of the bloodmeal. The parasite yield of southern <jats:italic>O. volvulus<\/jats:italic> in <jats:italic>S. oyapockense s.l.<\/jats:italic> flies biting man at \nPuerto Ayacucho (Amazonas) was about 1%, in agreement with the figures recorded for highly compatible sympatric \ncombinations such as <jats:italic>O. volvulus<\/jats:italic>\u2013<jats:italic>S. ochraceum s.l.<\/jats:italic> in Guatemala. No infective larval development of the northern parasite \nwas observed in southern <jats:italic>S. oyapockense<\/jats:italic>. These results, together with considerations of typical worm burdens in the \nhuman host, presence\/absence of armed cibaria in the simuliids, parasite-induced vector mortality, and fly biting rates, \nsuggest a lower potential for onchocerciasis to spread between the northern and southern endemic areas of Venezuela than \nthat between Amazonian hyperendemic locations and settlements outside this focus with high densities of <jats:italic>S. oyapockense<\/jats:italic> \ns.l.<\/jats:p>","DOI":"10.1017\/s0031182099005429","type":"journal-article","created":{"date-parts":[[2002,7,27]],"date-time":"2002-07-27T13:30:22Z","timestamp":1027776622000},"page":"143-160","source":"Crossref","is-referenced-by-count":14,"title":["<i>Onchocerca<\/i>\u2013<i>Simulium<\/i> complexes in Venezuela: can human \nonchocerciasis spread outside its present endemic areas?"],"prefix":"10.1017","volume":"120","author":[{"given":"M. G.","family":"BAS\u00c1\u00d1EZ","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"L.","family":"YARZ\u00c1BAL","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"H. L.","family":"FRONTADO","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"N. J.","family":"VILLAMIZAR","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"56","published-online":{"date-parts":[[2000,2,1]]},"container-title":["Parasitology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.cambridge.org\/core\/services\/aop-cambridge-core\/content\/view\/S0031182099005429","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2019,4,2]],"date-time":"2019-04-02T19:23:22Z","timestamp":1554233002000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.cambridge.org\/core\/product\/identifier\/S0031182099005429\/type\/journal_article"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2000,2]]},"references-count":0,"journal-issue":{"issue":"2","published-print":{"date-parts":[[2000,2]]}},"alternative-id":["S0031182099005429"],"URL":"https:\/\/doi.org\/10.1017\/s0031182099005429","relation":{},"ISSN":["0031-1820","1469-8161"],"issn-type":[{"value":"0031-1820","type":"print"},{"value":"1469-8161","type":"electronic"}],"subject":[],"published":{"date-parts":[[2000,2]]}}}