RESUMEN
A revision of the taxonomy of the Ketaketa subcomplex of the Simulium damnosum Theobald complex (Diptera: Simuliidae) is presented including new material from Tanzania, Malawi and South Africa. The cytotaxonomy, morphology and molecular identity of known and new taxa are described. The Ketaketa subcomplex is cytotaxonomically defined by the paracentric inversion 1L-7. We recognize three sibling species, namely Simulium latipollex (Enderlein), Simulium plumbeum Krueger, sp.n. and Simulium kipengere Krueger, sp.n., the latter comprising three cytoforms: 'Typical', 'Linthipe' and 'Mombo'. The cytoforms 'Mwamphanzi', 'Ketaketa' and 'Hammerkopi' are synonymized with S. plumbeum. Identification keys are provided on the basis of chromosomal and morphological characters. In view of their potential role as vectors of human onchocerciasis (river blindness) we also discuss the possible medical importance of the different cytoforms and their geographical distribution.
Asunto(s)
Cromosomas , Insectos Vectores/clasificación , Insectos Vectores/genética , Simuliidae/clasificación , Simuliidae/genética , Animales , Inversión Cromosómica , Mapeo Cromosómico , Clasificación/métodos , ADN Espaciador Ribosómico/genética , Femenino , Geografía , Insectos Vectores/anatomía & histología , Masculino , Reacción en Cadena de la Polimerasa/veterinaria , Simuliidae/anatomía & histología , Especificidad de la EspecieRESUMEN
The sibling species of the Simulium damnosum complex that are potential vectors in the foci of human onchocerciasis found in southern Malawi (the southern-most foci in Africa) were identified, using a combination of cytotaxonomic and molecular techniques. Simulium thyolense was found to be the most abundant species within the foci (representing 91% of the larvae collected), whilst S. kilibanum and cytoforms of the 'Ketaketa' subcomplex were the dominant members of the complex found outside of the foci. As all 188 biting female flies collected from the Thyolo, Mwanza and Mulanje foci were identified as S. thyolense, this species is probably the only significant vector of Onchocerca volvulus in the area, and the other Simulium species collected are assumed to be zoophilic. The results confirm the diagnostic value of the size of the amplicon(s) produced in PCR based on the sequences coding for the internal-transcribed-spacer region of the nuclear ribosomal DNA (ITS-1 rDNA), with a characteristic 340bp amplicon for S. thyolense. Chromosomal polymorphisms within S. thyolense indicate some degree of geographical isolation of the 'Thyolo-Mulanje' focus from the Mwanza focus.
Asunto(s)
Insectos Vectores/parasitología , Onchocerca volvulus , Oncocercosis/transmisión , Simuliidae/parasitología , Animales , Cromosomas/genética , ADN Espaciador Ribosómico/genética , Femenino , Amplificación de Genes/genética , Humanos , Insectos Vectores/genética , Cariotipificación/métodos , Larva/genética , Malaui/epidemiología , Oncocercosis/epidemiología , Polimorfismo Genético , Ríos , Simuliidae/genéticaRESUMEN
One of the fundamental challenges that the African Programme for Onchocerciasis Control (APOC) has had to face is how to identify the endemic communities where its mass ivermectin-treatment operations are to be carried out in conformity with its stated objective of targetting the most highly endemic, affected and at-risk populations. This it has done by adopting a technique, known as the rapid epidemiological mapping of onchocerciasis (REMO), that provides data on the distribution and prevalence of onchocerciasis. Integration of the REMO data into a geographical information system (GIS) enables delineation of zones of various levels of endemicity, and this is an important step in the planning process for onchocerciasis control. Zones are included in (or excluded from) the APOC-funded programme of community-directed treatment with ivermectin (CDTI), depending on whether or not their levels of onchocercal endemicity reach the threshold set by APOC. This review describes the application of the REMO/GIS technique by APOC in its operations, and identifies the remaining related challenges.
Asunto(s)
Cooperación Internacional , Oncocercosis Ocular/epidemiología , Práctica de Salud Pública , África/epidemiología , Animales , Dípteros , Vectores de Enfermedades , Métodos Epidemiológicos , Filaricidas/uso terapéutico , Humanos , Ivermectina/uso terapéutico , PrevalenciaRESUMEN
Larvae of the Simulium damnosum complex were collected in southern Malawi, in particular from the Thyolo onchocerciasis focus. Cytological identifications revealed the occurrence of S. (Edwardsellum) thyolense sp.nov., S. kilibanum Gouteux, 'Ketaketa', a new cytoform tentatively designated 'Mwamphanzi', and two unassigned specimens. Simulium thyolense sp.nov. is presumably the major vector of Onchocerca volvulus in the area, but it remains possible that the other cytospecies are secondary vectors. Simulium thyolense sp.nov. is most appropriately classified near the 'Sanje' subcomplex, whereas 'Mwamphanzi' and the unassigned specimens are members of the 'Ketaketa' subcomplex.