Resistance of Musca domestica L. populations to cyromazine (insect growth regulator) in Brazil

Five field populations of Musca domestica L. collected in poultry farms were bioassayed in order to detect possible resistance to the larvicide cyromazine in Brazil. The concentrations used were 0, 0.5, 0.1, 0.2, 0.4, 1, 2, 4 and 8 ppm. Three populations (Petrópolis, RJ, Montes Claros, MG and Promissão, SP) were resistant, while the other two populations (Ibiuna, SP and Monte Mor, SP) were more susceptible than the reference pathern used by the World Health Organization. The presence of three resistant house fly populations to cyromazine in Brazilian poultry farms strongly suggests that the operational aspects of larvicide use are important for the resistance development. Cyromazine is applied as a feed-through, both in Brazil and in the USA, where resistance has already been documented. However, in Denmark, where it was approved only as a topical manure spray, no case of resistance has yet been detected.

Morphometric comparison of Simulium perflavum larvae (Diptera: Simuliidae) in relation to season and gender in Central Amazônia, Brazil

Number of larval instars, age structure and environmental effects on these parameters represent basic information in the study of insect population biology. When species have economic importance, this information is essential in order to choose the best period to apply different control methods and to determine the stages of the life cycle of the insect that are most susceptible to each treatment. The family Simuliidae has many species of medical/veterinary importance in the world, and some studies in the temperate region have suggested that the number of larval instars and the larval size can vary according to the season, gender and some environmental factors, such as temperature and diet. This study, with the zoophilic species Simulium perflavum Roubaud, is the first in the Neotropics observing some of these factors and will serve as a template for other species of medical importance in the region. S. perflavum larvae were collected in five streams in Central Amazônia (Manaus and Presidente Figueiredo counties, State of Amazonas), in Sept./Oct. 1996 (dry season) and Feb./Mar. 1997 (rainy season). These larvae were measured (lateral length of head capsule and width of cephalic apodema) to determine the number of larval instars (n=3985), to compare the larval size between seasons and genders (last and penultimate larval instars, n=200). Seven larval instars were determined for this species using frequency distributions, t-tests and Crosby´s growth rule. Significant differences were not detected (t-test, p>0.05) in larval size between seasons and genders. Our results differ from some found in temperate regions suggesting that in the Neotropical region the larval size in different seasons and different genders remains constant, although some environmental parameters, such as diet, change depending on the season.

Lutzomyia aldafalcaoae sp. n. a new species of Phlebotominae (Diptera: Psychodidae) from Mato Grosso do Sul, Brazil

A new sand fly species, Lutzomia aldafalcaoae is described from males collected in Vila Trindade, an urban district in Aquidauana county, State of Mato Grosso do Sul, Brazil, in October 1996. Taxonomic remarks and a description of the new species is presented.

Deltamethrin-impregnated dog collars have a potent anti-feeding and insecticidal effect on Lutzomyia longipalpis and Lutzomyia migonei

Deltamethrin-impregnated PVC dog collars were tested to assess if they were effective in protecting dogs from sand fly bites of Lutzomyia longipalpis and Lu. migonei. A protective effect against Old World species Phlebotomus perniciosus was demonstrated before. Four dogs wearing deltamethrin collars and three dogs wearing untreated collars (not impregnated with deltamethrin) were kept in separate kennels for over eight months in a village on the outskirts of Fortaleza in Ceará, Brazil. Periodically, a dog from each group was sedated, placed in a net cage for 2 h in which 150 female sand flies had been released 10-15 min before. Lu. longipalpis were used 4, 8, 12, 16, 22, 27, and 35 weeks after the attachment of the collars. Lu. migonei were used 3, 7, 11, 15, 22, 26, and 36 weeks after attachment. During 35 weeks, only 4.1% (81 of 2,022) Lu. longipalpis recovered from the nets with the deltamethrin collared dogs were engorged, an anti-feeding effect of 96%. Mortality initially was over 90% and at 35 weeks was 35% with half of the sand flies dying in the first 2 h. In contrast, 83% of the 2,094 Lu. longipalpis recovered from the nets containing the untreated collared dogs were engorged and the mortality ranged from zero to 18.8% on one occasion with 1.1% dying in the first 2 h. Similar findings were found with Lu. migonei: of 2,034 sand flies recovered over this period, only 70 were engorged, an anti-feeding effect of 96.5%, and mortality ranged from 91% initially to 46% at 36 weeks. In contrast, engorgement of controls ranged from 91 to71% and a mortality ranged from 3.5 to 29.8%. These studies show that deltamethrin impregnated collars can protect dogs against Brazilian sand flies for up to eight months. Thus, they should be useful in a program to control human and canine visceral leishmaniasis.

Identification of entomopathogenic Bacillus isolated from Simulium (Diptera, Simuliidae) larvae and adults

Entomopathogenic bacteria isolated from Simulium larvae and adults from breeding sites in the states of São Paulo and Rio de Janeiro, Brazil, were identified as 18 strains of Bacillus thuringiensis and one of B. sphaericus. Most of these strains were serotyped according to their flagellar antigens. However, nine of the B. thuringiensis samples, could not be serotyped and were designated as "autoagglutinating"; they were also shown to be toxic in preliminary tests against Aedes aegypti larvae. Additionally, B. sphaericus was also shown to be toxic towards Culex quinquefasciatus larvae.