Entomological survey of phlebotomine sand flies (Diptera: Psychodidae) in a focus of visceral leishmaniasis in central Iran.

BACKGROUND & OBJECTIVES: Visceral leishmaniasis (VL) is a major vector-borne disease in Iran. A focus of VL is present in Shahreza county, Isfahan province, central Iran. The main objective of this study was to determine the probable vectors in this area. METHODS: Sand flies were collected biweekly using sticky paper traps, CDC light-traps, and aspirators from outdoors as well as indoors. All female sand flies were dissected and identified. Promastigotes were inoculated to hamsters and detected by Nested PCR. Approximately 7528 sand flies representing 12 species were collected from April 2003 to October 2004. Phlebotomus (Phlebotomus) papatasi Scopoli, Phlebotomus (Larroussious) major Annandale and Sergentomyia (Sergentomyia) sintoni Pringle were the predominant species. Two percent of P. major was found with natural promastigote infections. INTERPRETATION & CONCLUSION: This is the first report of natural promastigote infection in P. major in central Iran. The activity of P. major started from April and ended in October with a peak in September. The parasites were identified as Leishmania infantum using standard PCR. P. major is a possible vector of leishmaniasis and is susceptible to DDT in this area.

Vector control in leishmaniasis.

Indoor residual spraying is a simple and cost effective method of controlling endophilic vectors and DDT remains the insecticide of choice for the control of leishmaniasis. However resistance to insecticide is likely to become more widespread in the population especially in those areas in which insecticide has been used for years. In this context use of slow release emulsified suspension (SRES) may be the best substitute. In this review spraying frequencies of DDT and new schedule of spray have been discussed. Role of biological control and environment management in the control of leishmaniasis has been emphasized. Allethrin (coil) 0.1 and 1.6 per cent prallethrin (liquid) have been found to be effective repellents against Phlebotomus argentipes, the vector of Indian kalaazar. Insecticide impregnated bednets is another area which requires further research on priority basis for the control of leishmaniasis. Role of satellite remote sensing for early prediction of disease by identifying the sandflygenic conditions cannot be undermined. In future synthetic pheromons can be exploited in the control of leishmaniasis.

Susceptibility status of Japanese encephalitis vectors in Kurnool and Mehboobnagar districts of Andhra Pradesh, India.

An entomological survey in Kurnool and Mahboobnagar districts of Andhra Pradesh state, India was undertaken in January, 2002 to find out vector population of Japanese Encephalitis and their susceptibility status to different insecticides. Five Culicine species viz. of Cx. tritaeniorhynchus, Cx. vishnui, Cx. pseudovishnui, Cx. bitaeniorhynchus, Cx. gelidus were captured during the survey. Another suspected vectors Anopheles subpictus and An. hyrcanus were also prevalent in the study villages. The larval population showed a high degree of resistance to Fenthion and Temephos. The test mortality to DDT ranged between 75% and 90%. The mortality of Cx. tritaeniorhynchus, Cx vishnui and An. subpictus ranged from 85% to 95%. Cx. tritaeniorhynchus is susceptible to Deltamethrin and Cyfluthrin. Cx. vishnui showed 80 % and 85% mortality to DDT and Malathion respectively.

Glutathion S-transferase activity and DDT-susceptibility of Malaysian mosquitos.

Comparative DDT-susceptibility status and glutathion s-transferase (GST) activity of Malaysian Anopheles maculatus, Culex quinquefasciatus and Aedes aegypti was investigated to ascertain the role of this enzyme in DDT resistance. The standardised WHO dose-mortality bioassay tests were used to determine DDT susceptibility in these mosquitos, whilst GST microassay (Brogdon and Barber, 1990) was conducted to measure the activity of this enzyme in mosquito homogenate. It appeared that DDT susceptibility status of Malaysian mosquitos was not correlated with GST activity.

Mixed function oxidase system in hepatic and extrahepatic tissues of developing chickens following various treatments.

Alterations in hepatic and extrahepatic protein content, activities of drug enzymes, lipid peroxidation and hydrogen peroxide formation and levels of microsomal electron transport components were examined in developing chickens during treatment with phenobarbital (PB), benzene and 1,1,1,-trichloro 2,2, bis (p-chlorophenyl) ethane (DDT) treated group of 4-8 weeks old chickens. Activities of hepatic and extrahepatic (kidney, lung, intestine) tissues enzymes were induced during PB treatment in all groups of chicken. However benzene and DDT treated group of chickens recorded decrease in activities of drug enzymes. Magnitude of increase due to PB administration was much more in liver as compared to kidney, lung and intestine. Hydrogen peroxide and lipid peroxide formation significantly increased in all tissues during treatments of benzene and DDT. Levels of cyto P-450, cyto b5 and cyto c-reductase, lipid peroxidation and hydrogen peroxide formation increased in all groups of chickens during various treatments. The results suggest that chicken liver contains more drug enzyme activities and electron transport components during development as compared to other tissues. Benzene and DDT administration resulted into decrease in the activities of drug enzymes.

Effect of sublethal dosages of insecticides on chikungunya virus susceptible and refractory strains of Aedes aegypti.

Three strains of Aedes aegypti mosquitos viz (i) CRS, refractory to Chikungunya (CHIK) virus by oral route of infection but susceptible to DDT (2) CSS, susceptible to CHIK virus and also susceptible to DDT (3) CSS-DDTR, susceptible to CHIK virus but resistant to DDT, were examined for the effect of sublethal dosages of DDT and deltamethrin on their fecundity. Biochemical analysis showed that there was an increase in glutathione s-transferase activity in the CSS-DDTR strain which was associated with DDT resistance. There was an increase in acetylcholinesterase activity in the CRS strain, however it was not associated with resistance to all the three insecticides tested. No significant differences in the fecundity of these three strains were observed, though there was some increase in the number of non layers in CSS-DDTR strain after the treatment of DDT and mean number of eggs laid by CSS and CRS strains was slightly reduced (0.5 > p < 0.1) after the treatment with deltamethrin.

Biochemical basis of DDT-resistance in Aedes aegypti population from a dengue affected area in Shahjahanpur city.

Entomological studies conducted in Jalalnagar, Shahjahanpur city, Uttar Pradesh, India, during an outbreak of dengue in 1992, showed that Ae. aegypti mosquitoes were resistant to DDT and had some tolerance to malathion in the adults and the larvae. Biochemical analysis suggested that DDT resistance was related to elevated glutathione s-transferase and tolerance to malathion was due to a little increase in esterase activity. Crosses of DDT-resistant and susceptible strain suggested that resistance was codominant (metabolic type).

Insecticide susceptibility status of Anopheles koliensis (Diptera: Culicidae) in northeastern Irian Jaya, Indonesia.

Anopheles koliensis, an important malaria vector in the interior region of Irian Jaya, Indonesia, was evaluated for susceptibility to three different insecticide compounds using the standard World Health Organization diagnostic test kit and pretreated impregnated papers. A series of tests were conducted in Arso PIR I, a transmigrant settlement 60 km south of Jayapura, from January 1988 to May 1989. All compounds were tested at the recommended diagnostic dosage and exposure time. An. koliensis were susceptible to 1.0% fenitrothion at two hour exposure (N = 358) and 5.0% malathion at one hour exposure (N = 371) after the 24-hour holding period. Significant resistance to DDT was observed in both the An. koliensis and Culex quinquefasciatus populations. Approximately 30% of the An. koliensis population (N = 468) was resistant to 4% DDT at both one and two hour exposures. These findings indicate that routine use of DDT in Arso PIR I for indoor residual house spraying may be of limited effectiveness, in part, because of physiological resistance. However, use of an alternative insecticide will be more expensive and might prove equally ineffective because of the exophilic behavior of the species. This is the first confirmed report from repeated observations of DDT resistance in An. koliensis from Indonesia.

susceptibility of the Egyptian phlebotomus papatasi to five insecticides

The present study was undertaken to establish a baseline susceptibility levels of the Egyptian P. papatasi to five insecticides [BHC and DDT [chlorinated hydrocarbon], permethrin [synthetic pyrethroides], malathion [organophosphorus] and propoxur [carbamate]]. The results obtained revealed that the laboratory bred P. papatasi were more susceptible to the five insecticides than the wild caught ones. The insecticidal efficiency of the five insecticides based on LC50 was in the following descending order: Propoxur, permethrin, BHC, DDT and malathion for laboratory bred flies and propoxur, permethrin, BHC, malathion then DDT for wild caught flies. The least LC50 was when using propoxur for both the wild caught flies [0.0014%] and laboratory bred ones [0.00043%]. The least LT50 was when using propoxur for both the wild caught flies [4.8 seconds] and the laboratory bred flies [2.2 seconds]