Elizabeth Ferreira Rangel

Lutzomyia longipalpis and the eco-epidemiology of American visceral leishmaniasis, with particular reference to Brazil: a review

An historical review is given of American visceral leishmaniasis (AVL), with particular reference to the eco-epidemiology of the disease in Brazil. Following the first records of AVL in this country, in 1934, the sandfly Lutzomyia longipalpis (Lutz and Neiva, 1912) was incriminated as the principal vector. It is now generally accepted, however, that there exist a number of cryptic species under the name of Lu. longipalpis s.l. and that variations in the quantity of the vasodilatory peptide maxadilan in the saliva of flies from different populations of Lu. longipalpis s.l., may account for the variable clinical manifestations of AVL seen in different geographic regions. Distribution of AVL has been shown to extend throughout most of South and Central America, with the domestic dog serving as the principal reservoir of infection for man. However, while one hypothesis suggests that the causative parasite is Leishmania infantum, imported from Europe with the Portuguese and Spanish colonists, the demonstration of a high rate of benign, inapparent infection in foxes in Amazonian Brazil raised an opposing suggestion that the parasite is indigenous to the Americas. Recent reports of similar infections in native marsupials, and possibly rodents, tend to support this view, particularly as Lu. longipalpis is primordially a silvatic sandfly. Although effective control measures in foci of the disease will diminish the number of canine and human infections, the presence of such an enzootic in a variety of native animals will render the total eradication of AVL unlikely.

Proven and putative vectors of American cutaneous leishmaniasis in Brazil: aspects of their biology and vectorial competence

The aim of the present review is to give relevant information on aspects of the biology and ecology, including the vectorial competence of Lutzomyia sand fly species suggested as vectors of American cutaneous leishmaniasis in Brazil. The disease, due to Leishmania (Viannia) braziliensis, has been registered in most municipalities in all the Brazilian states and its transmission is associated with more than one sand fly species in each geographical region. A variety of Leishmania species can be found in the Amazon basin, where different epidemiological chains have been detected with the participation of different phlebotomine vectors. Finally, a discussion is presented on some sand fly species found naturally infected by Leishmania, but for which there is as yet no evidence regarding their epidemiological importance.

Infecção natural de Lutzomyia intermedia Lutz & Neiva, 1912, em área endêmica de leishmaniose tegumentar no Estado do Rio de Janeiro

In a focus of cutaneous leishmaniasis in Jacarepagua, Rio de Janeiro, one specimen of Lutzomyia intermedia was found naturally infected with Leishmania braziliensis.

Lutzomyia longipalpis (Diptera, Psychodidae, Phlebotominae) and urbanization of visceral leishmaniasis in Brazil.

The article discusses habits related to the vectorial competence of Lutzomyia longipalpis, along with evidence confirming the importance of this sand fly species in the epidemiological chain of visceral leishmaniasis in Brazil. A new epidemiological profile for visceral leishmaniasis is also postulated, associated with domestic environments and the role of Lu. longipalpis in this process, its sylvatic origin, and its capacity to adapt to a wide range of habitats. Another sand fly species, Lu. cruzi, is mentioned as a vector of visceral leishmaniasis in some municipalities in Central Brazil, based on studies in endemic areas of the country.

Studies on sandfly fauna (Diptera: Psychodidae) in a foci of cutaneous leishmaniasis in Mesquita, Rio de Janeiro State, Brazil

In a study on vectors of cutaneous leishmaniasis in Mesquita, Rio de Janeiro State, Brazil, eleven species of sandflies were found: Lutzomyia longipalpis, L. fischeri, L. quinquefer, L. intermedia, L. whitmani, L. shannoni, L. cortelezzii, L. edwardsi, L. migonei, L. lanei and L. firmatoi. Lutzomyia intermedia was the predominant species. It was collected indoors but in much higher numbers outdoors, in the close vicinity of houses. In comparative captures it was found to feed more frequently on equines, and less frequently on man and dogs. Studies, using man and animals as baits, showed that blood-feeding started in the evening, and remained stable during the night, until early morning. June, August and October were the months of highest density.

An outbreak of american cutaneous leishmaniasis (Leishmania braziliensis braziliensis) in a periurban area of Rio de Janeiro city, Brazil: clinical and epidemiological studies

From July 1984 to September 1986, 105 cases of American cutaneous leishmaniasis were studied in a locality closely situated to an urbanized area of the city of Rio de Janeiro, Brazil. Settlement in this area was established at least 20 years ago but the first cases were noted six months prior to the beginning of this study. Cases were almost exclusively cutaneous and ulcerated, with one to six months of evolution. Montenegros skin tests were positive in all cases and anti-Leishmania antibodies were detected by indirect immunofluorescence test in 74.3% of the patients. Parasites were demonstrated in 69.5% of cases. Domestic animals were easily found infected: 32% of the examined dogs and 30.8% of the examined equines were positive to the presence of Leishmania in cutaneous ulcerated lesions. Parasite isolates from human, dog and equines were immunologically characterized and identified as L. b. braziliensis. 73.0% of the sandfly population were Lutzomyia intermedia mainly caught on human baits and on domestic animals. Our observations suggest that this is an area of recent established L. b. braziliensis infection and that transmission probably occurs indoors or outdoors close to the houses.

Study on the bacterial midgut microbiota associated to different Brazilian populations of Lutzomyia longipalpis (Lutz & Neiva) (Diptera: Psychodidae)

The bacterial community associated with the midgut of three Brazilian Lutzomyia longipalpis (Lutz & Neiva) populations, two from endemic areas for visceral leishmaniasis (Jacobina, Bahia State and São Luís, Maranhão State) and one from a non-endemic area (Lapinha Cave, Minas Gerais State), was identified. Five groups, 35 females each, from each population were separated; a total of 175 females per collecting area were analyzed. The species identification was based on molecular and traditional bacteriological methods. All bacteria were either affiliated to non-Enterobacteriaceae, such as Acinetobacter, Burkholderia, Flavimonas, Pseudomonas and Stenotrophomonas, or and to Enterobacteriaceae, such as Citrobacter, Enterobacter, Escherichia, Klebsiella, Serratia, Pantoea, Morganella and Weeksella. Stenotrophomonas was found to be associated with all three populations studied. In addition, Serratia spp., which are well documented as laboratory contaminant of insects, were detected only in the Jacobina population. We also discuss the impact of the colonization of insect gut by bacteria on the development and transmission of pathogens.

Seasonality of Lutzomyia intermedia and Lutzomyia whitmani (Diptera: Psychodidae: Phlebotominae), occurring sympatrically in area of cutaneous leishmaniasis in the State of Rio de Janeiro, Brazil

Lutzomyia intermedia and Lutzomyia whitmani occur sympatrically in the district of Posse, municipality of Petrópolis, in the State of Rio de Janeiro (114 km from the city of Rio de Janeiro), where sand flies were captured weekly for three consecutive years in both the peridomicile and forest, in two first years from 18:00 to 22:00 h, using a Shannon trap and CDC light traps. The anthropophilic habit was assessed by recording the specimens that bit the human captors. Considering the different capture types and sites, the following species were identified: Brumptomyia brumpti, B. cardosoi, B. guimaraesi, Lutzomyia amarali, L. longipalpis, L. microps, L. costalimai, L. edwardsi, L. firmatoi, L. migonei, L. termitophila, L. tupynambai, L. fischeri, L. pessoai, L. lutziana, L. shannoni, L. barrettoi, L. intermedia, L. whitmani, L. lloydi, and L. minasensis. L. intermedia (38.3%) and L. whitmani (38.6%) predominated. L. intermedia predominated in the peridomicile, where it displayed more intense anthropophily, while L. whitmani displayed greater density in the banana plantations and forest, preferential sites for biting humans. Studies on seasonality showed that while L. intermedia displayed greater density in the hottest months of the year (December, January, and February), L. whitmani was abundant in the coolest months (June, July, and August), although both occurred throughout the year.

Zoonotic cutaneous leishmaniasis due to Leishmania (Viannia) braziliensis associated with domestic animals in Venezuela and Brazil

After outbreaks of cutaneous leishmaniasis in Solano State, Venezuela, 5% of the population had parasitized ulcers while after similar outbreaks in Mesquita, Rio de Janeiro State, Brazil, 9% had the disease. In these foci children, including some under six years of age, were affected. There was no significant difference in the occurrence of the disease according to sex or type of employment. In Solano, 3% of dogs and 28% of donkeys had parasitized lesions, while in Mesquita these indices were 19.8% and 30.8% respectively. The parasite from man, dogs and equines was identified as Leishmania (Viannia) braziliensis, by zymodeme and serodeme characterization. In these foci there is evidence suggesting that leishmaniasis is a zoonosis, possibly with equines and dogs as reservoirs, although both a wild enzootic cycle and the role of man as a source of infection can not be ruled out. Transmission is assumed to occur peridomestically by sandfly vectors such as Lutzomyia panamensis in Venezuela and Lutzomyia intermedia in Brazil. Information about the origin of these foci suggests that infected equines may be an important factor in the dissemination of the parasite in a peridomestic situation where these sandflies are abundant.

Variation between geographical populations of Lutzomyia (Nyssomyia) whitmani (Antunes & Coutinho, 1939) sensu lato (Diptera:Psychodidae:Phlebotominae) in Brazil

Phylogenetic analysis of morphometric and biological characters indicated that there are two distinct forms of Lutzomyia whitmani in Brazil: one is present both north and south of the River Amazonas in the State of Pará while the other occurs in northeast Brazil, in the State of Ceará, and further south, including the type locality in State of Bahia. The Amazonian form is reportedly neither strongly anthropophilic nor synanthropic, and it is the vector of Leishmania shawi; whereas the southern form is often collected peridomestically, while biting man, and has been found infected with Le.(V.) braziliensis. The ratio of the length of the genital filaments to that the genital pump was found to be consistently smaller in males of the Amazonian populations. A middle repetitive DNA element was isolated by differentially screening a genomic library made using Amazonian material, and the sequence was diagnostic for this form of Lu. whitmani (being absent or occurring in low copy number in the southern form). The total evidence suggests there are at least two, geographically-isolated forms of Lu. whitmani, which may represent different cryptic species.