Effect of mouse antisera targeting the Phlebotomus papatasi midgut chitinase PpChit1 on sandfly physiology and fitness

In sandflies, the absence of the peritrophic matrix (PM) affects the rate of blood digestion. Also, the kinetics of PM secretion varies according to species. We previously characterised PpChit1, a midgut-specific chitinase secreted in Phlebotomus papatasi (PPIS) that is involved in the maturation of the PM and showed that antibodies against PpChit1 reduce the chitinolytic activity in the midgut of several sandfly species. Here, sandflies were fed on red blood cells reconstituted with naïve or anti-PpChit1 sera and assessed for fitness parameters that included blood digestion, oviposition onset, number of eggs laid, egg bouts, average number of eggs per bout and survival. In PPIS, anti-PpChit1 led to a one-day delay in the onset of egg laying, with flies surviving three days longer compared to the control group. Anti-PpChit1 also had a negative effect on overall ability of flies to lay eggs, as several gravid females from all three species were unable to lay any eggs despite having lived longer than control flies. Whereas the longer survival might be associated with improved haeme scavenging ability by the PM, the inability of females to lay eggs is possibly linked to changes in PM permeability affecting nutrient absorption.

Efficacy of two insecticides: Methyl carbamate and aluminium phosphide on leishmaniasis vectors in Varamin, Iran

Leishmaniosis is a prevalent tropical parasitic disease, which is caused by Leishmania protozoa. The infection can be limited in immune-competent individuals; however, in immune-compromised individuals it could proceed to chronic and ulcerative disease. The reservoirs are carnivores, and rodents and its vectors are Phlebotomus and Lutzumia. The prevalence of different spices of Phlebotomus populations and the effects of insecticides on them are investigated in Abardejhe district located in southeast of Tehran, Iran. Tablets of aluminum phosphide [3 g] and residual formulation of methyl carbamate at concentrations of 1 and 2 g/m 2 were used in rodents' burrows. Phlebotomus population was highly sensitive to both insecticides used here, and their population significantly decreased by 80% within two months after pplication of insecticides. The effects of methyl carbamate at concentrations used lasted two months longer than that of aluminum phosphide. Control and prevention of Leishmania infection depends on the habitat and behavior of vectors and reservoirs. Periodic insecticide spraying, using residual compound inside and outside residential areas, as well as breading places of sandflies, specially rodent's burrows, are shown to be very effective

Susceptibility of Phlebotomus argentipes against DDT in endemic Districts of North Bihar, India.

Susceptibility status of Indian kala-azar vector Phlebotomus argentipes after DDT spray from endemic areas of Muzaffarpur and Vaishali district and unsprayed non-endemic area of Patna district, Bihar, India were compared. Higher Lc50 viz. 2.6% and 3.2% and LT50, values 51.0 and 69.0 minutes to 4% DDT were observed for P. argentipes of Muzaffarpur and Vaishali district, whereas P. argentipes of Patna district was 100% susceptible to same concentration, indicating increased tolerance in P. argentipes. It is concluded DDT resistant P. argentipes, particularly in endemic zone growing. The possible explanation could be long-term insecticidal pressure.

Relative efficacy of DEPA and neem oil for repellent activity against Phlebotomus papatasi, the vector of leishmaniasis.

The insect repellent N, N-diethylphenyl acetamide (DEPA) was compared with neem oil, a commercial preparation, for protection against 3 day old un-fed female of the sandfly, Phlebotomus papatasi, (Diptera: Psychodidae) under laboratory conditions on mouse. The percentage protection against sandfly bite provided by neem oil was significantly higher than DEPA when applied at 1% and 2% concentrations (p = 0.000, t = 21.474; df = 6 and p = 0.001, t = 5.960; df = 6 respectively). However, neem oil did not show any significant difference with DEPA at 5% (p = 0.1682, t = 0.15667; df = 6). This clearly indicates that at higher concentration (5%) both neem oil and DEPA exhibited similar repellent action against P. papatasi.

Sandfly survey in Nainital and Almora districts of Uttaranchal with particular reference to Phlebotomus argentipes, vector of kala-azar.

Kala-azar continues to pose a major public health problem in Bihar, West Bengal and parts of eastern Uttar Pradesh in India causing great deal of morbidity and mortality. During 1998, several kala-azar cases from Sub-Himalayan region were treated in Delhi hospitals. And a suspected focus of kala-azar was subsequently reported from this area. Therefore a preliminary sandfly survey was carried out during October, 1999 in 18 randomly selected villages at different altitudes in Nainital & Almora districts of Kumaon region Uttaranchal. The surveys revealed relative preponderance of vector sandfly Ph. argentipes as 77%; mainly confined to cattlesheds and mixed dwellings in the villages at an altitude ranging from 350-960 metres main sea level. The other sandfly species encountered were: Ph. papatasi 6.9%, Ph. major 2.9% and 13.2% Sergentomyia spp. 17.4% Ph. argentipes reacted positive with human antisera and 82.6% with bovine but none reacted with goat, pig dog and bird antisera indicating that Ph. argentipes in the area is mainly zoophilic. Ph. argentipes was found to be highly susceptible to DDT; mortality ranging from 98-100%.

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]