Influence of temperature on microsporidia infections in a natural population of Simulium pertinax Kollar, 1832 (Diptera; Simuliidae).

During the studies involving the correlation between the water temperature of the breeding site of Simulium pertinax larvae and the infection prevalence by microsporidia, developed in the Andorinhas river, Magé, RJ, weekly samples of blackfly larvae were taken within a two-year period (2001-2002 and 2003-2004), and it was noticed that the infections by Amblyospora sp. were more prevalent when compared to infections by Polydispyrenia sp. in larvae. It was also observed that the infections do not follow the same pattern, since the genus Amblyospora was recorded almost every month during the study with the exception of December, 2001. In the results of correlation between the environmental water temperature and the microsporidia infection rates, it was observed that for the first period studied, there was a high negative correlation, while during the second period there was absence correlation. On the other hand, the Amblyospora sp. infection rates prove that the correlation was high and significant in the first period, but was not significant in the second sampling period and Polydispyrenia sp. showed absence correlation in both periods.

Influence of temperature on microsporidia infections in a natural population of Simulium pertinax Kollar, 1832 (Diptera; Simuliidae)

During the studies involving the correlation between the water temperature of the breeding site of Simulium pertinax larvae and the infection prevalence by microsporidia, developed in the Andorinhas river, Magé, RJ, weekly samples of blackfly larvae were taken within a two-year period (2001-2002 and 2003-2004), and it was noticed that the infections by Amblyospora sp. were more prevalent when compared to infections by Polydispyrenia sp. in larvae. It was also observed that the infections do not follow the same pattern, since the genus Amblyospora was recorded almost every month during the study with the exception of December, 2001. In the results of correlation between the environmental water temperature and the microsporidia infection rates, it was observed that for the first period studied, there was a high negative correlation, while during the second period there was absence correlation. On the other hand, the Amblyospora sp. infection rates prove that the correlation was high and significant in the first period, but was not significant in the second sampling period and Polydispyrenia sp. showed absence correlation in both periods.

Este estudo envolvendo a correlação entre a temperatura da água do criadouro de larvas de Simulium pertinax e a prevalência de infecção por microsporídeos, foi desenvolvido no rio Andorinhas, Magé, RJ, onde foram realizadas coletas semanais de larvas de simulídeos no período de dois anos (2001-2002 e 2003-2004), e foi observado que as infecções por Amblyospora sp. apresentaram maior prevalência quando comparadas com as infecções por Polydispyrenia sp. Com isso, verificou-se que as infecções não seguem o mesmo padrão, onde o gênero Amblyospora foi relatado em quase todos os meses de desenvolvimento do estudo, com exceção apenas de dezembro de 2001. Nos resultados de correlação entre a temperatura ambiente e a taxa de infecção por microsporídeos no primeiro período de estudo, foi observada uma forte correlação negativa, porém foi verificada ausência de correlação no segundo período. Embora tenha sido evidenciada uma forte e significante correlação com a taxa de infecção por Amblyospora sp. no primeiro período, esta correlação mostrou-se não significativa no segundo período de amostragem e Polydispyrenia sp. apresentou ausência de correlação em ambos os períodos de estudo.

Histopathological and ultrastructural effects of delta-endotoxins of Bacillus thuringiensis serovar israelensis in the midgut of Simulium pertinax larvae (Diptera, Simuliidae).

The bacterium Bacillus thuringiensis (Bt) produces parasporal crystals containing delta-endotoxins responsible for selective insecticidal activity on larvae. Upon ingestion, these crystals are solubilized in the midgut lumen and converted into active toxins that bind to receptors present on the microvilli causing serious damage to the epithelial columnar cells. We investigated the effect of these endotoxins on larvae of the Simulium pertinax, a common black fly in Brazil, using several concentrations during 4 h of the serovar israelensis strain IPS-82 (LFB-FIOCRUZ 584), serotype H-14 type strain of the Institute Pasteur, Paris. Light and electron microscope observations revealed, by time and endotoxin concentration, increasing damages of the larvae midgut epithelium. The most characteristic effects were midgut columnar cell vacuolization, microvilli damages, epithelium cell contents passing into the midgut lumen and finally the cell death. This article is the first report of the histopathological effects of the Bti endotoxins in the midgut of S. pertinax larvae and the data obtained may contribute to a better understanding of the mode of action of this bacterial strain used as bioinsecticide against black fly larvae.

Histopathological and ultrastructural effects of delta-endotoxins of Bacillus thuringiensis serovar israelensis in the midgut of Simulium pertinax larvae (Diptera, Simuliidae)

The bacterium Bacillus thuringiensis (Bt) produces parasporal crystals containing delta-endotoxins responsible for selective insecticidal activity on larvae. Upon ingestion, these crystals are solubilized in the midgut lumen and converted into active toxins that bind to receptors present on the microvilli causing serious damage to the epithelial columnar cells. We investigated the effect of these endotoxins on larvae of the Simulium pertinax, a common black fly in Brazil, using several concentrations during 4 h of the serovar israelensis strain IPS-82 (LFB-FIOCRUZ 584), serotype H-14 type strain of the Institute Pasteur, Paris. Light and electron microscope observations revealed, by time and endotoxin concentration, increasing damages of the larvae midgut epithelium. The most characteristic effects were midgut columnar cell vacuolization, microvilli damages, epithelium cell contents passing into the midgut lumen and finally the cell death. This article is the first report of the histopathological effects of the Bti endotoxins in the midgut of S. pertinax larvae and the data obtained may contribute to a better understanding of the mode of action of this bacterial strain used as bioinsecticide against black fly larvae.

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.

Biological control program against simuliids in the State of São Paulo, Brazil.

In Brazil, the use of biological vector-control methods has been largely confined to experimental research, with little or no application of such techniques by public institutions responsible for implementing control programs. The notable exceptions have been the black fly control program carried out by the Health Secretariat in the State of São Paulo. Since the 1980s, São Paulo's "Superintendência de Controle de Endemias" has been conducting studies on the viability of using Bacillus thuringiensis (H-14) for simuliid control, and the results have been so encouraging that the agency has now incorporated this method into its Simuliid Control Program.

[Control of Simuliidae with an emulsifiable concentrate of Bacillus thuringiensis]. / Controle de simulídeos com concentrado emulsionável de Bacillus thuringiensis.

The effects of the three flowable concentrate formulations of Bacillus thuringiensis var. israelensis (H-14): Teknar (Zoecon, Sandoz Inc.), Vectobac (Abbott Labs.), and Bactimos (Biochem, Solvay Labs.) against Simulium pertinax were evaluated in 24 streams in the North Littoral Zone of São Paulo State, Brazil. There was no significant difference in effective carry (80% or more mortality) among the formulations when applied at the rate of 10 mg/liter for one minute. There was a strong correlation between stream discharge and effective carry of the formulations, except in the case of Teknar, possibly due to the influence of the physical characteristics of the streams where evaluation was conducted.

Field evaluation of Bacillus thuringiensis var. israelensis for control of black flies in the North Littoral Zone of Brazil's São Paulo State.

The impact of three flowable concentrate formulations of Bacillus thuringiensis var. israelensis (H-14) upon Simulium pertinax larvae was evaluated in 24 coastal streams of Brazil's São Paulo State. While no significant differences were found regarding the three formulations' effectiveness, significant correlations were found between the discharge rates of individual streams and the distances over which at least two of the formulations were carried effectively downstream to produce 80% mortality. The relatively short carry distances found for small streams could pose difficulties for control programs that need to treat large numbers of such streams, and suggests a need for research directed at increasing the distances B. thuringiensis (H-14) formulations can be carried.