Efficacy of permethrin-impregnated curtains against endophilic phlebotomine sandflies in Burkina Faso.
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Biomedical subjects
Publications and source records attributed to M Maroli.
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Transovarial transmission (TOT) of Toscana (TOS) and Arbia (ARB) viruses in a laboratory colony of Phlebotomus perniciosus is reported. Toscana and ARB viruses were maintained in P. perniciosus females, initially infected by intrathoracic inoculation, for 2 and 3 consecutive generations respectively. TOT was demonstrated in F1 (75%) and F2 (67%) generation adults for TOS and F1 (47%), F2 (37%), and F3 (34%) generation adults for ARB virus. The progressive decline of virus infection rates in each generation suggests that these agents cannot be maintained indefinitely by TOT. No infection was observed in F1 progeny after female parents were fed through membranes with either virus. Transovarially infected females were able to transmit TOS virus by bite to a susceptible vertebrate. Venereal infection of P. perniciosus females mated to males transovarially infected with TOS virus was seen.
In a survey of Leishmania infections of phlebotomine sandflies caught in central and south Italy in 1986, zymodeme MON-1 (Montpellier 1) of Leishmania infantum was isolated from Phlebotomus perniciosus and L. tarentolae [= Trypanosoma platydactyli?] was isolated from Sergentomyia minuta, providing for mainland Italy the first direct proof of these long-suspected parasite-vector associations. The roles of P. perfiliewi and P. perniciosus in the transmission of Leishmania spp. in Italy are discussed.
One out of 213 Phlebotomus perfiliewi caught from an endemic cutaneous leishmaniasis focus in Abruzzi region (Italy) was naturally infected with promastigotes. The parasites were grown in culture medium and in a hamster, typed by the examination of 11 isoenzymes, and found to be indistinguishable from Leishmania infantum s.st. (Montpellier zymodeme 1). The probable role of P. perfiliewi in the transmission of cutaneous leishmaniasis due to L. infantum s.l. in the focus is discussed.
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Dogs naturally infected with Leishmania infantum Nicolle were treated with three courses of meglumine antimoniate. Changes were observed in the dogs' clinical signs, antibody titres and in infection rates of Phlebotomus perniciosus Newstead fed on the dogs. A large reduction in the sandfly infection rate was observed for 4-5 months after the first treatment. The use of antimonial drugs is advocated for the control of canine leishmaniasis and to reduce risks of L.infantum transmission.
Three topical repellents were evaluated against Phlebotomus perniciosus using dose-response techniques. A total of 1800 laboratory reared nulliparous females of P. perniciosus, 2 to 15 days old, and 21 human volunteers were used. The effective dose (ED50 and ED90) for Deet, Indalone and MGK 11 has been determined. Indalone and MGK 11 were more effective than standard Deet. The data obtained indicate that P. perniciosus is highly sensitive to the repellents compared with other blood-sucking arthropods.
A total of 1,394 sandflies were collected in the domestic resting sites of Ouagadougou areas and in two villages of the East region of Burkina Faso using pyrethrum spray catch, oiled papers and miniature CDC light traps during the rainy season in 1984 and 1985. Thirteen species were identified, one belonging to the genus Phlebotomus and the others to the genus Sergentomyia. S. antennata (34.94%), S. bedfordi (16.64%), S. clydei (14.42%), S. schwetzi (13.20%), P. duboscqi (8.46%), S. adleri (7.03%) and S. africana (2.87%) were in order of percentage the more abundant species. The abdominal stages of the sandfly species caught in the human habitations are described. P. duboscqi, the suspected vector of cutaneous leishmaniasis in the area, seems to have a preferential domestic biotope.
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The role of the sandfly species Phlebotomus perniciosus Parrot in laboratory transmission of Leishmania infantum was investigated. One of the wild reservoirs of the disease, the black rat (Rattus rattus), was used as vertebrate host. The parasite was transmitted by the bite of experimentally infected P. perniciosus to the black rat which, six months later, was infective to the same sandfly species. These experimental data confirm the role of P. perniciosus in the transmission of L. infantum, as suggested by earlier studies based on epidemiological data.
Female sandflies of three Phlebotomus species were fed on membrane. The feeding apparatus is described and preliminary data obtained are also reported. A total 2,835 sandflies were fed: 2,596 P. perniciosus, 104 P. perfiliewi and 135 P. papatasi.
Phlebotomus perniciosus were infected by intrathoracic inoculation and membrane feeding techniques with two phleboviruses (Toscana and Arbia) isolated in Italy from this sand fly species. Low levels of multiplication of both viruses were detected after intrathoracic inoculation of the sand flies. Only some insects were found infected after oral ingestion of the two viruses. The percentage of flies infected orally was related to the amount of virus ingested. Toscana virus was transovarially transmitted to two larvae of the F1 progeny of orally infected sand flies. No signs of infection were observed after oral infection when unnatural virus-vector combinations were tested, e.g., Toscana virus-P. papatasi or Naples sand fly fever virus-P. perniciosus. The virus concentrations recorded in P. perniciosus experimentally infected with both Toscana and Arbia viruses were similar to those found in naturally-infected sand flies.
Man-bait catches of Phlebotomus perniciosus were carried out in a human and canine leishmaniasis focus in Central Italy (Monte Argentario, Grosseto) to evaluate the man-sandfly contact of this vector. P. perniciosus females were collected biting on man outside, during the first hours of the night, when the local people are at risk. The results of these captures are discussed and the man-sandfly contact is considered in relation to the epidemiological aspects of the disease in the area under study.
The recent finding that four Leishmania isolates from Rattus rattus are enzymologically identical to L. infantum, aetiological agent of human and canine visceral leishmaniasis in the Mediterranean area, has stimulated further research on the role of R. rattus in the epidemiology of visceral leishmaniasis in Tuscany, Italy. The present work has led to the following results: (a) R. rattus experimentally infected with L. infantum displayed a general resistance to the parasite, even though it appeared that a very low number of amastigotes persisted in the animal for a long period; (b) Phlebotomus perniciosus and P. perfiliewi induced to feed on rats, with either a massive visceral infection or a subpatent immunodepressed infection, became infected, though in different proportions; (c) P. perniciosus and P. perfiliewi were readily attracted to, and fed on, the black rat in nature. These findings, together with those obtained earlier, strongly suggest that the black rat may be one of the wild reservoirs of L. infantum in the areas under study.
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A skin test survey carried out in the towns of Porto St. Stefano and Porto Ercole showed a total positivity rate of 15.3%. The progressive increase of positivity according to age was not uniform but similar for the two towns since the values concerning the last two age groups did not follow the general trend of the graph but were lower than expected. The possible causes of this phenomenon have been discussed. The absence of overt visceral leishmaniasis cases in recent years and the concomitant high prevalence of canine leishmaniasis have been considered in the light of the occurrence of infectious diseases and the increase of the nutritional levels in the local human population.
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