11 research outputs found
The Potential for Dispersal of Onchocerciasis in Ecuador in Relation to the Distribution of the Vector Simulium exiguum (Diptera:Simuliidae)
Elimination of onchocerciasis in Ecuador: findings of post-treatment surveillance.
BACKGROUND: The Esmeraldas focus of onchocerciasis in Ecuador expanded geographically during the 1980s and was associated with severe ocular and skin disease. Mass drug administration (MDA) with ivermectin started in 1991, initially once but later twice a year, in the principle endemic focus followed by all satellite foci. Treatment was stopped in 2009 when entomological assessments determined that transmission of Onchocerca volvulus had been interrupted. METHODS: Three years after the cessation of ivermectin treatment in 2012, as defined by the WHO guidelines for onchocerciasis elimination, blackfly collections were done in four sentinel sites in former hyperendemic areas. The presence of infective larvae in local vectors, Simulium exiguum and Simulum quadrivittatum, was assessed by detection of O. volvulus DNA by PCR. Additional flies captured in four extra-sentinel sites located in former hyper- and mesoendemic dispersed isolated areas were also assessed. RESULTS: The results from 68,310 captured blackflies, 40,114 from four sentinel villages in the previously hyperendemic areas (Corriente Grande, El Tigre, San Miguel on Río Cayapas and Naranjal on Río Canandé) and 28,197 from extra-sentinel locations, were all negative for the presence of O. volvulus. These extra-sentinel sites (Hualpí on Río Hoja Blanca, Capulí on Río Onzole, La Ceiba on Río Tululví and Medianía on Río Verde) were included to provide additional evidence of the impact of MDA on the transmission of O. volvulus in isolated endemic areas. CONCLUSIONS: Our data indicate that transmission of O. volvulus has been stopped in all endemic areas in Ecuador, including all satellite foci outside the main focus. These findings indicate that a strategy of ivermectin distribution twice a year to over 85% of the treatment-eligible population was effective in eliminating the infection from Ecuador in a focus with a highly competent primary vector, S. exiguum, and where the infection rates were equal to or greater than observed in many onchocerciasis foci in Africa
A survey on Triatoma dimidiata in an urban area of the province of Heredia, Costa Rica
Ecological patterns of blood-feeding by kissing-bugs (Hemiptera: Reduviidae: Triatominae)
The potential for dispersal of onchocerciasis in Ecuador in relation to the distribution of the vector Simulium exiguum (Diptera:Simuliidae)
The future dispersal of onchocerciasis in Ecuador is dependent on the
distribution of cytotypes of the vector species complex Simulium
exiguum. Over the last 14 years, collections of larvae have been made
from over 25 rivers, between 80-1600 m altitude, from various sites on
both sides of the Andes. Analysis of larval polytene chromosomes was
used to determine the distributions of each cytotype. On the western
side of the Andes, the Cayapa cytotype (the only cytotype directly
incriminated as a vector) has a distribution from Santo Domingo de los
Colorados northwards. The Quevedo and Bucay cytotypes occur from Santo
Domingo de los Colorados southwards. On the eastern side of the Andes,
the Aguarico cytotype occurs in the Rio Aguarico and a new cytotype is
present in the tributaries of the Rio Napo. Whether the disease will
spread south of Santo Domingo and on the eastern side of the Andes
depends on vector capacity of the cytotypes and the dispersal patterns
of individuals infected with onchocerciasis. At present the Aguarico,
Bucay and Quevedo cytotypes are known to be efficient hosts, but their
biting preferences and biting densities have not yet been evaluated
The Simuliidae (Diptera) of the Santiago onchocerciasis focus of Ecuador
Volume: 58Start Page: 79End Page: 13
Cytological and isoenzyme analysis of the Bucay and Quevedo cytotypes of the onchocerciasis vector Simulium exiguum (Diptera: Simuliidae) in Ecuador
Four cytotypes of Simulium exiguum occur in Ecuador, where this morphospecies is the primary vector of onchocerciasis. In this paper, we give the first full description of the banding pattern of the larval polytene chromosomes of the Quevedo cytotypes differ from the chromosomal standard sequence (of the Cayapa cytotype) by the fixed inversions IIL-5 and IIL-6. The Quevedo cytotype additionally differs from the standard and Bucay cytotypes by processing a differentiated X chromosome, wich is indicated by the inversion IIS-A. As the degree of reproductive isolation between the Bucay and Quevedo cytotypes has not yet been estabilished, they must be regarded as intraspecific variants of the same species. In fact, isoenzyme characterizations showed that the Bucay and Quevedo cytotypes are differentiated only to the extent expected of incipient species or geographical populations. Moreover, the sibiling species status previously given to the Bucay cytotype needs be reassessed, there being inadequate analysis from areas in Ecuador where Bucay occurs in sympatry with the standard Cayapa cytotype. No isoenzyme electromorphs were discovered that identified all or mostadult females of any one (cytotype-pure) collection