Genetic variability in biochemical characters of Brazilian field populations of the Leishmania vector, Lutzomyia longipalpis (Diptera: Psychodidae).

Abstract

Abstract. The phlebotomine sand fly Lutzomyia longipalpis is the insect vector of visceral leishmaniasis, a protozoan disease of increasing incidence and distribution in Central and South America. Electrophoretic allele frequencies of 15 enzyme loci were compared among the L. longipalpis populations selected across its distribution range in Brazil. The mean heterozygosity of two colonized geographic strains (one each from Colombia and Brazil) were 6% and 13% respectively, with 1.6-1.9 alleles detected per locus. In contrast, among the seven widely separated field populations, the mean heterozygosity ranged from 11% to 16% with 2.1-2.9 alleles per locus. No locus was recovered that was diagnostic for any of the field populations. Allelic frequency differences among five field strains from the Amazon basin and eastern coastal Brazil were very low, with Nei's genetic distances of less than 0.01 separating them. The two inland and southerly samples from Minas Gerais (Lapinha) and Bahia (Jacobina) states were more distinctive with genetic distances of 0.024-0.038 and 0.038-0.059, respectively, when compared with the five other samples. These differences were the consequence of several high frequency alleles (glycerol-3-phosphate dehydrogenase [Gpd 1.69 ] and phosphoglucomutase [Pgm 1.69 ]) relatively uncommon in other strains. The low genetic distances, absence of diagnostic loci, and the distribution of genes in geographic space indicate L. longipalpis of Brazil to be a single, but genetically heterogeneous, polymorphic species.American visceral leishmaniasis (kala-azar) is a fatal disease in the New World tropics. Approximately 1.6 million people are at risk of infection with this disease and on average, 16,000 cases are reported annually. 1,2 More than 90% of human cases occur in Brazil. 3,4 Visceral leishmaniasis in humans is caused by the kinetoplastid protozoan Leishmania donovani chagasi Cunha and Chagas. 5,6 However, in Central America, infections also frequently result in cutaneous disease. [7][8][9] The most important vector of Leishmania d. chagasi is the phlebotomine sand fly Lutzomyia longipalpis (Lutz and Neiva). 10-13 It was first described from specimens collected in São Paulo Bosque de Saúde (no longer in existence), 100 km north northwest of Belo Horizonte at the Caves of Maquiné (Cordisburgo) and at a ranch near the river port of Benjamin Constant (Além Paraíba, 140 km northeast of Rio de Janeiro) Fazenda Ouro Fino. 14,15 It occurs from southern Mexico to northern Argentina in discontinuous distributions. 16 In Brazil, L. longipalpis has been recorded in habitats ranging from heavily populated urban centers to rural, periurban areas in a wide variety of ecotopes including mountain ranges to the east and the Amazon river basin covering most of the north and central Brazil. Therefore, the sand flies survive in a variety of habitats and sometimes in zones where formidable barriers prevent their migration. Since they have a limited flight range, rarely migrating more than 100 meters, the widely separ...

Phylogeography of the neotropical sand fly Lutzomyia longipalpis inferred from mitochondrial DNA sequences

“…Phylogenetic analysis (MP) reveals close relationships among populations in the Brazilian highlands (Lapinha Cave), the Amazon (Salvaterra and Santarem), San Francisco Basin (Jacobina) and Brazilian scrubland (Baturité). These results are concordant with patterns of divergence in the nuclear genome (isozyme variation) among the same Brazilian populations, with the exception of the population at Roraima, that was not included in the isozyme studies (Mukhopadhyay et al, 1998;Mutebi et al, 1999;Azevedo et al, 2000). These authors concluded that populations in Brazil represent a single species, but with relatively high levels of genetic divergence among local populations.…”

Aspects related to productivity for four generations of a Lutzomyia longipalpis laboratory colony

“…Colonies of L. longipalpis have been successfully established before (Sherlock & Sherlock 1959, Killick-Kendrick et al 1977, Ready 1978,1979, Modi & Tesh 1983, Buescher et al 1984. L. longipalpis populations from Central and South America show a great polymorphism in behavior, morphology and biochemical characters (Ward et al 1983, Hamilton et al 1996, Dujardin et al 1997, Mukhopadhyay et al 1998a, b, Dias et al 1998, Yin et al 1999. These results either lead L. longipalpis differences to be suspected as due to a complex of cryptic species (Lanzaro et al 1993, Warburg et al 1994 This work was partially supported by Capes (MSc scholarship to JFLM) and by the State Government of Roraima.…”

“…Variability in tergal spot morphology is believed to be a polymorphic character not related to genetic isolation (Mukhopadhyay et al 1998a).…”

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

“…The existence of such cryptic species in Brazil was disputed by Mukhopadhyay et al (1998), Mutebi et al (1999), Azevedo et al (2000), and Arrivillaga et al (2002Arrivillaga et al ( , 2003 who considered that there is only a single species in that country, based on a study of several widely separated populations for genetic variability in biochemical characters. They felt that the reasons for any epidemiological variations in AVL should be sought elsewhere.…”