Expression plasticity of Phlebotomus papatasi salivary gland genes in distinct ecotopes through the sand fly season.

BACKGROUND: Sand fly saliva can drive the outcome of Leishmania infection in animal models, and salivary components have been postulated as vaccine candidates against leishmaniasis. In the sand fly Phlebotomus papatasi, natural sugar-sources modulate the activity of proteins involved in meal digestion, and possibly influence vectorial capacity. However, only a handful of studies have assessed the variability of salivary components in sand flies, focusing on the effects of environmental factors in natural habitats. In order to better understand such interactions, we compared the expression profiles of nine P. papatasi salivary gland genes of specimens inhabiting different ecological habitats in Egypt and Jordan and throughout the sand fly season in each habitat. RESULTS: The majority of investigated genes were up-regulated in specimens from Swaymeh late in the season, when the availability of sugar sources is reduced due to water deprivation. On the other hand, these genes were not up-regulated in specimens collected from Aswan, an irrigated area less susceptible to drought effects. CONCLUSION: Expression plasticity of genes involved with vectorial capacity in disease vectors may play an important epidemiological role in the establishment of diseases in natural habitats.

Phlebotomus papatasi sand fly predicted salivary protein diversity and immune response potential based on in silico prediction in Egypt and Jordan populations.

Phlebotomus papatasi sand flies inject their hosts with a myriad of pharmacologically active salivary proteins to assist with blood feeding and to modulate host defenses. In addition, salivary proteins can influence cutaneous leishmaniasis disease outcome, highlighting the potential of the salivary components to be used as a vaccine. Variability of vaccine targets in natural populations influences antigen choice for vaccine development. Therefore, the objective of this study was to investigate the variability in the predicted protein sequences of nine of the most abundantly expressed salivary proteins from field populations, testing the hypothesis that salivary proteins appropriate to target for vaccination strategies will be possible. PpSP12, PpSP14, PpSP28, PpSP29, PpSP30, PpSP32, PpSP36, PpSP42, and PpSP44 mature cDNAs from field collected P. papatasi from three distinct ecotopes in the Middle East and North Africa were amplified, sequenced, and in silico translated to assess the predicted amino acid variability. Two of the predicted sequences, PpSP12 and PpSP14, demonstrated low genetic variability across the three geographic isolated sand fly populations, with conserved multiple predicted MHCII epitope binding sites suggestive of their potential application in vaccination approaches. The other seven predicted salivary proteins revealed greater allelic variation across the same sand fly populations, possibly precluding their use as vaccine targets.

Molecular homogeneity in diverse geographical populations of Phlebotomus papatasi (Diptera, Psychodidae) inferred from ND4 mtDNA and ITS2 rDNA Epidemiological consequences.

An intraspecific study on Phlebotomus papatasi, the main proven vector of Leishmania major among the members of the subgenus Phlebotomus, was performed. The internal transcribed spacer 2 (ITS 2) of rDNA and the ND4 gene of mt DNA were sequenced from 26 populations from 18 countries (Albania, Algeria, Cyprus, Egypt, Greece, India, Iran, Israel, Italy, Lebanon, Morocco, Saudi Arabia, Spain, Syria, Tunisia, Turkey, Yugoslavia and Yemen), and compared. Samples also included three other species belonging to the subgenus Phlebotomus: P. duboscqi, a proven vector of L. major in the south of Sahara (three populations from Burkina Faso, Kenya and Senegal), P. bergeroti, a suspected vector of L. major (three populations from Oman Sultanate, Iran and Egypt), and one population of P. salehi from Iran. A phylogenetic study was carried out on the subgenus Phlebotomus. Our results confirm the validity of the morphologically characterized taxa. The position of P. salehi is doubtful. Variability in P. papatasi contrasts with that observed within other species having a wide distribution like P. (Paraphlebotomus) sergenti in the Old World or Lutzomyia (Lutzomyia) longipalpis in the New World. Consequently, it could be hypothesized that all populations of P. papatasi over its distribution area have similar vectorial capacities. The limits of the distribution area of L. major are correlated with the distribution of common rodents acting as hosts of the parasites.

Discovery of diurnal resting sites of phlebotomine sand flies in a village in southern Egypt.

In an attempt to find diurnal resting sites of adult phlebotomine sand flies, potential phlebotomine adult habitats were aspirated in the village of Bahrif in Aswan, Egypt. During this survey, sand flies were aspirated from low (30-45 cm high) irregular piles of mud bricks found under high date palm canopies between the village and the Nile River. There were 5 males and 7 females of Phlebotomus papatasi and 3 males of Sergentomyia schwetzi. Six of the 7 aspirated females were engorged with blood. A total of 78 sand flies was captured on 3 glue boards placed overnight on the ground next to the mud bricks. Attempts to aspirate sand flies from adjacent walls and plants were unsuccessful. The identification of diurnal resting sites in less structured habitats may ultimately lead to more effective adult sand fly control.

Population genetics analysis of Phlebotomus papatasi sand flies from Egypt and Jordan based on mitochondrial cytochrome b haplotypes.

BACKGROUND: Phlebotomus papatasi sand flies are major vectors of Leishmania major and phlebovirus infection in North Africa and across the Middle East to the Indian subcontinent. Population genetics is a valuable tool in understanding the level of genetic variability present in vector populations, vector competence, and the development of novel control strategies. This study investigated the genetic differentiation between P. papatasi populations in Egypt and Jordan that inhabit distinct ecotopes and compared this structure to P. papatasi populations from a broader geographical range. METHODS: A 461 base pair (bp) fragment from the mtDNA cytochrome b (cyt b) gene was PCR amplified and sequenced from 116 individual female sand flies from Aswan and North Sinai, Egypt, as well as Swaimeh and Malka, Jordan. Haplotypes were identified and used to generate a median-joining network, F ST values and isolation-by-distance were also evaluated. Additional sand fly individuals from Afghanistan, Iran, Israel, Jordan, Libya, Tunisia and Turkey were included as well as previously published haplotypes to provide a geographically broad genetic variation analysis. RESULTS: Thirteen haplotypes displaying nine variant sites were identified from P. papatasi collected in Egypt and Jordan. No private haplotypes were identified from samples in North Sinai, Egypt, two were observed in Aswan, Egypt, four from Swaimeh, Jordan and two in Malka, Jordan. The Jordan populations clustered separately from the Egypt populations and produced more private haplotypes than those from Egypt. Pairwise F ST values fall in the range 0.024-0.648. CONCLUSION: The clustering patterns and pairwise F ST values indicate a strong differentiation between Egyptian and Jordanian populations, although this population structure is not due to isolation-by-distance. Other factors, such as environmental influences and the genetic variability in the circulating Le. major parasites, could possibly contribute to this heterogeneity. The present study aligns with previous reports in that pockets of genetic differentiation exists between populations of this widely dispersed species but, overall, the species remains relatively homogeneous.

Bionomics of phlebotomine sandflies at a peacekeeping duty site in the north of Sinai, Egypt.

A longitudinal entomological survey for sandflies was conducted from 1989 to 1991 at a focus of enzootic cutaneous leishmaniasis in Northeast Sinai, Egypt, within the border region monitored by multinational peacekeepers. Standardized sampling with CDC light traps, oiled paper "sticky traps", and human landing collection was employed to determine monthly trends in species composition, density, sex ratio, and reproductive status of vector sandflies. Each collection method independently defined sandfly seasonality as the period May-November in 1990, and March-October in 1991. Plebotomus papatasi was the only anthropophagic species found and comprised more than 94% of the sandfly population. Two population peaks (May, July) were observed for this species in both survey years. Density of P. papatasi in underground bunkers was higher than outside but inflated by a greater proportion of male flies. During 1990, the proportion of gravid P. papatasi increased progressively during the 5 months period from May to September and averaged 29.5% and 29.7% for interior and exterior collections, respectively. Density of P. papatasi was greater during 1991, but proportions of gravid flies were significantly lower in each survey month and averaged 14.9% and 12.3% for interior and exterior collections, respectively. Seasonal rates of Leishmania-infected P. papatasi averaged 0.8% and 0.9% in 1989 and 1990, but fell to zero in 1991, suggesting an unstable focus of Leishmania major transmission. Proportions of gravid flies may be a valid indicator of the physiological age and epidemiologic importance of the vector sandfly population at this focus. The strong correlation of sticky trap indices to human-landing/biting rates shows that this is an accurate, inexpensive, and no-risk alternative to human bait collections.

Use of bioassay and microplate assay to detect and measure insecticide resistance in field populations of Culex pipiens from filariasis endemic areas of Egypt.

Insecticide and resistance bioassays and microplate assays were performed on Culex pipiens mosquitoes to determine the level and mechanisms of resistance. Culex pipiens larvae were collected from three filariasis-endemic areas of Egypt and reared to adults for subsequent production and testing of F1 generation larvae and adults. Bioassays were performed using World Health Organization (WHO) methods with the diagnostic doses of 6 organophosphate insecticides for larvae and 1 organochlorine (OC), 4 pyrethroid, 2 organophosphate, and 2 carbamate insecticides for adults. Microplate assays were performed to measure levels of beta esterase, acetylcholinesterase, insensitive acetylcholinesterase, oxidases, and glutathione-S-transferase enzymes. Larval bioassay results showed clear indications of resistance to organophosphate insecticides. Adult bioassays also showed widespread, significant resistance to many insecticides from all four classes, including the OC, DDT. The Qalubiya larval population was susceptible only to malathion, whereas Sharkiya larvae were susceptible to malathion, temephos, and chlorpyrifos. On the other hand, larval specimens from Assiut were resistant to all insecticides tested. Larval bioassay results were supported by those of microplate assays in showing elevated levels of glutathione S-transferase in populations from all three areas. In general, microplate results confirmed patterns of resistance observed using bioassays, and mechanisms of resistance were evident for all three areas sampled. Mechanisms of resistance are discussed in relation to microplate and bioassay results for the areas sampled and pesticides used.

Phlebotomus papatasi SP15: mRNA expression variability and amino acid sequence polymorphisms of field populations.

BACKGROUND: The Phlebotomus papatasi salivary protein PpSP15 was shown to protect mice against Leishmania major, suggesting that incorporation of salivary molecules in multi-component vaccines may be a viable strategy for anti-Leishmania vaccines. METHODS: Here, we investigated PpSP15 predicted amino acid sequence variability and mRNA profile of P. papatasi field populations from the Middle East. In addition, predicted MHC class II T-cell epitopes were obtained and compared to areas of amino acid sequence variability within the secreted protein. RESULTS: The analysis of PpSP15 expression from field populations revealed significant intra- and interpopulation variation.. In spite of the variability detected for P. papatasi populations, common epitopes for MHC class II binding are still present and may potentially be used to boost the response against Le. major infections. CONCLUSIONS: Conserved epitopes of PpSP15 could potentially be used in the development of a salivary gland antigen-based vaccine.

Evaluation of 1-octen-3-ol and carbon dioxide as attractants for Phlebotomus papatasi (Diptera: Psychodidae) in southern Egypt.

The effectiveness of 1-octen-3-ol (octenol) as an attractant for collecting medically important psychodids has never been reported. This study evaluated the effects of carbon dioxide (CO2) and octenol released at 2 rates, individually and in combination, as attractants for adult sand flies in a small village in southern Egypt. Four sand fly species were collected: Phlebotomus papatasi, P. sergenti, Sergentomyia palestinensis, and S. schwetzi. Only P. papatasi was collected in numbers sufficient to allow statistical analysis. This study reaffirms that CO2 is an effective attractant for female P. papatasi and also demonstrates that neither male nor female P. papatasi respond to octenol alone. Additionally, no synergistic attractancy for either females or males was observed when CO2 and octenol were combined.

Profiling of human acquired immunity against the salivary proteins of Phlebotomus papatasi reveals clusters of differential immunoreactivity.

Phlebotomus papatasi sand flies are among the primary vectors of Leishmania major parasites from Morocco to the Indian subcontinent and from southern Europe to central and eastern Africa. Antibody-based immunity to sand fly salivary gland proteins in human populations remains a complex contextual problem that is not yet fully understood. We profiled the immunoreactivities of plasma antibodies to sand fly salivary gland sonicates (SGSs) from 229 human blood donors residing in different regions of sand fly endemicity throughout Jordan and Egypt as well as 69 US military personnel, who were differentially exposed to P. papatasi bites and L. major infections in Iraq. Compared with plasma from control region donors, antibodies were significantly immunoreactive to five salivary proteins (12, 26, 30, 38, and 44 kDa) among Jordanian and Egyptian donors, with immunoglobulin G4 being the dominant anti-SGS isotype. US personnel were significantly immunoreactive to only two salivary proteins (38 and 14 kDa). Using k-means clustering, donors were segregated into four clusters distinguished by unique immunoreactivity profiles to varying combinations of the significantly immunogenic salivary proteins. SGS-induced cellular proliferation was diminished among donors residing in sand fly-endemic regions. These data provide a clearer picture of human immune responses to sand fly vector salivary constituents.

Evaluation of the fat-tailed gerbil, Pachyuromys duprasi (Rodentia: Gerbillidae), as a new animal model for studies of Leishmania major infection and transmission.

The fat-tailed gerbil Pachyuromys duprasi is a common burrowing rodent found across the northern Sahara Desert from Morocco to Egypt. There is overlap in the geographical distribution and ecological habitats of P. duprasi, several Old World Leishmania species, and numerous sand fly vectors of Leishmania, but there are no records that document the natural occurrence of this gerbil with any species of Leishmania or phlebotomine sand fly. Experiments were conducted to determine its potential as a natural host and laboratory animal model for Leishmania major. Captive-born P. duprasi were inoculated subcutaneously (s.c.) in the tail with promastigotes or amastigotes of an Egyptian strain of L. major and monitored for signs of infection. Local swelling and erythema was visible 10-12 days after amastigote inoculation, and within 3-4 weeks swelling had increased tail widths by up to 78%. Infections progressed more slowly and less conspicuously following inoculation with promastigotes. Tissue density of amastigotes in the gerbil's tail lesions after inoculating with either stage of L. major was significantly lower than that produced in the footpads of BALB/c mice by the same parasite and incubation period. Laboratory transmission of L. major to P. duprasi by sand fly bite was demonstrated and acquisition of L. major, by bite, from tail lesions of infected P. duprasi to laboratory-reared Phlebotomus papatasi was also achieved with 10% of biting flies developing promastigote infections. The acquisition and development of L. major infections in P. papatasi after biting an infected P. duprasi and the susceptibility of P. duprasi to L. major delivered at low densities by sand fly bites indicate that fat-tailed gerbils could serve as a natural host and reservoir of L. major.

Ecological and control techniques for sand flies (Diptera: Psychodidae) associated with rodent reservoirs of leishmaniasis.

BACKGROUND: Leishmaniasis remains a global health problem because of the substantial holes that remain in our understanding of sand fly ecology and the failure of traditional vector control methods. The specific larval food source is unknown for all but a few sand fly species, and this is particularly true for the vectors of Leishmania parasites. We provide methods and materials that could be used to understand, and ultimately break, the transmission cycle of zoonotic cutaneous leishmaniasis. METHODS AND FINDINGS: We demonstrated in laboratory studies that analysis of the stable carbon and nitrogen isotopes found naturally in plant and animal tissues was highly effective for linking adult sand flies with their larval diet, without having to locate or capture the sand fly larvae themselves. In a field trial, we also demonstrated using this technique that half of captured adult sand flies had fed as larvae on rodent feces. Through the identification of rodent feces as a sand fly larval habitat, we now know that rodent baits containing insecticides that have been shown in previous studies to pass into the rodents' feces and kill sand fly larvae also could play a future role in sand fly control. In a second study we showed that rubidium incorporated into rodent baits could be used to demonstrate the level of bloodfeeding by sand flies on baited rodents, and that the elimination of sand flies that feed on rodents can be achieved using baits containing an insecticide that circulates in the blood of baited rodents. CONCLUSIONS: Combined, the techniques described could help to identify larval food sources of other important vectors of the protozoa that cause visceral or dermal leishmaniasis. Unveiling aspects of the life cycles of sand flies that could be targeted with insecticides would guide future sand fly control programs for prevention of leishmaniasis.

Experimental acquisition, development, and transmission of Leishmania tropica by Phlebotomus duboscqi.

We report experimental infection and transmission of Leishmania tropica (Wright), by the blood-feeding sand fly Phlebotomus duboscqi (Neveu-Lemaire). Groups of laboratory-reared female sand flies that fed "naturally" on L. tropica-infected hamsters, or artificially, via membrane feeding device, on a suspension of L. tropica amastigotes, were dissected at progressive time points post-feeding. Acquisition, retention and development of L. tropica through procyclic, nectomonad, and leptomonad stages to the infective metacyclic promastigote stage, and anterior progression of the parasites from abdominal midgut bloodmeal to the thoracic midgut were demonstrated in both groups. Membrane feeding on the concentrated amastigote suspension led to metacyclic promastigote infections in 60% of sand flies, whereas only 3% of P. duboscqi that fed naturally on an infected hamster developed metacyclics. Sand flies from both groups re-fed on naïve hamsters, but despite infections in 25-50% of membrane-fed and 2-3.5% of naturally fed flies, no skin lesions developed in the hamsters. After four months of observation these animals were euthanized and necropsied. Screening of the organs and tissue by polymerase chain reaction (PCR) that targeted the small subunit RNA gene, amplified generic Leishmania DNA from liver, spleen, bone marrow, and blood, but only from hamsters bitten by membrane-infected P. duboscqi. These results are notable in demonstrating the ability of P. duboscqi, originating from Kenya, to acquire, retain, develop, and transmit a Turkish strain of L. tropica originally isolated from a human case of cutaneous leishmaniasis. This marks the first demonstration of complete development and transmission of L. tropica by a member of the Phlebotomus subgenus of sand flies.

Effects of ivermectin on blood-feeding Phlebotomus papatasi, and the promastigote stage of Leishmania major.

Ivermectin (IVM) is a chemically modified macrocyclic lactone of Streptomyces avermitilis that acts as a potent neurotoxin against many nematodes and arthropods. Little is known of IVM's effect against either blood-feeding Phlebotomus sand flies, or the infective promastigote stage of Leishmania transmitted by these flies. We injected hamsters subcutaneously with two standard IVM treatments (200 and 400 µg/kg body weight) and allowed cohorts of Leishmania major-infected Phlebotomus papatasi to blood-feed on these animals at various posttreatment time points (4 h, 1, 2, 6, and 10 days). Infected and uninfected sand flies that bit treated and untreated hamsters served as controls. Serum levels of IVM in low- and high-dose-treated hamsters were determined at the five time points. Sand fly mortality following blood feeding was recorded at 24-h intervals and, in relation to IVM treatment, was time and dose dependent. Mortality was most rapid and greatest among infected flies that fed nearest to time of dosing. Mean survival of infected sand flies after feeding on untreated hamsters was 11.5 days, whereas that of infected sand flies that fed 4 h, 1 day, or 2 days posttreatment on high-dose-treated hamsters (400 µg/kg) was 1.6, 2.1, and 2.7 days, respectively. Infected and uninfected sand flies that blood fed 6 days following low-dose IVM treatment (200 µg/kg) still experienced significantly greater mortality (p < 0.02) than controls. Promastigotes dissected out of surviving flies that fed on IVM-treated hamsters showed typical motility and survival. Moreover, 21.7% of IVM-treated hamsters developed lesions after being fed upon by infected sand flies. L. major promastigotes appeared to be tolerant to ng/mL blood levels of IVM that caused significant mortality for up to 10 days posttreatment in blood-feeding P. papatasi.

Virus isolations and high population density implicate Culex antennatus (Becker) (Diptera: Culicidae) as a vector of Rift Valley Fever virus during an outbreak in the Nile Delta of Egypt.

In June, 2003, Egypt's hospital-based electronic disease surveillance system began to record increased cases of acute febrile illness from governorates in the Nile Delta. In response to a request for assistance from the Egyptian Ministry of Health and the World Health Organization (WHO), the U.S. Naval Medical Research Unit No. 3 (NAMRU-3) provided assistance in identifying the cause and extent of this outbreak. Testing of human clinical samples (n=375) from nine governorates in Egypt identified 29 cases of RVF viremia that spanned the period of June to October, and a particular focus of disease in Kafr el Sheikh governorate (7.7% RVF infection rate). Veterinary samples (n=101) collected during this time in Kafr el Sheikh and screened by immunoassay for RVFV-specific IgM identified probable recent infections in cattle (10.4%) and sheep (5%). Entomologic investigations that focused in rural, rice growing villages in the Sidi Salim District of Kafr el Sheikh during August-September, 2003, collected, identified, and tested host-seeking female mosquitoes for the presence of pathogenic viruses. Three isolates of RVF virus (RVFV) were obtained from 297 tested pools of female mosquitoes and all three RVFV isolates came from Cx. antennatus (Becker). While Cx. pipiens has been considered the primary vector of RVF virus in Egypt and is often the most common man-biting species found, Cx. antennatus was the dominant species captured at the 2003 outbreak location in Kafr el Sheikh governorate. This is the first time that Cx. antennatus has been found naturally infected with RVFV in Egypt.

Laboratory demonstration of the acquisition and development of leishmania major in the sand fly Phlebotomus kazeruni (Diptera: Psychodidae).

Phlebotumus kazeruni, a blood-feeding, xerophilic sand fly species found broadly throughout North Africa and Western Asia, is a suspected vector of cutaneous leishmaniasis (CL). Following successful laboratory colonization of this species, we employed the murine (BALB/c) infection model to determine whether our Sinai strain of P. kazeruni was able to successfully acquire, develop, and transmit a Sinai strain of Leishmania major. Groups of female sand flies were fed 1) by membrane, hamster blood containing culture-produced L. major promastigotes, 2) by membrane, hamster blood containing a suspension of L. major tissue amastigotes, and 3) directly upon L. major lesions in BALB/c mice. Samples of blood-fed sand flies from each group were dissected on selected days post-feeding and examined by light microscope for acquired and developing Leishmania infections. Female P. kazeruni acquired viable parasites by the three feeding methods. Development of ingested parasites to infective-stage metacyclic forms was observed and seen to progress from midgut to the mouthparts. Promastigote infection rates were 20% in flies fed directly upon infected mice, 35% in those fed amastigotes via membrane, and 100% in flies fed culture promastigotes via membrane. Direct blood fee-ding upon BALB/c mice was more avid (P < 0.001) among previously blood-fed flies, possibly indicative of selection and colony adaptation to murine blood-feeding. Although we failed to demonstrate clear transmission of infective-stage L. major promastigotes by feeding infected flies upon a susceptible murine host, and producing lesions in the animal, the progressive development of L. major from amastigote to metacyclic-stage promastigotes, and movement of the parasites from sand fly midgut to its mouthparts, provides evidence that P. kazeruni could serve as a vector for this parasite.

Rickettsial pathogens in the tropical rat mite Ornithonyssus bacoti (Acari: Macronyssidae) from Egyptian rats (Rattus spp.).

We collected and tested 616 tropical rat mites (Ornithonyssus bacoti (Hirst)) from rats (Rattus norvegicus (Berkenhout) and R. rattus (Linnaeus)) throughout 14 governorates in Egypt and tested DNA extracts from pools of these mites for Bartonella spp., Coxiella burnetii, and Rickettsia spp. by PCR amplification and sequencing. Three different mite-associated bacterial agents, including one Bartonella and two Rickettsia spp., were detected in eight pools of mites. Further research could demonstrate the vector potential of mites and pathogenicity of these agents to humans or animals.

Identification of Culex pipiens Linnaeus (Diptera: Culicidae) immunogens recognized by host humoral immunity and their impact on survival and fecundity.

Insecticide use continues to be the primary control strategy to reduce insect vector populations. Concerns about insecticide resistance in target organisms, environmental degradation, and possible deleterious impact on human health have led researchers to seek a variety of alternative control strategies. We tested a relatively new method for controlling mosquitoes using host immune response. New Zealand White (NZW) rabbits (Oryctolagus cuniculus) were immunized with salivary gland (SGE), midgut (MGE), or ovary (OVE) extracts from female Culex pipiens L. Immunized rabbits were then exposed to unfed adult mosquitoes which were subsequently observed for changes in survival, fecundity, and hatch success. Parents that fed upon MGE- (P<0.001), SGE- (P<0.018) and OVE- (P<0.018) immunized rabbits experienced significantly higher mortality within 48 hours than parents fed on control rabbits. Midgut extract elicited the strongest effects upon survival (P<0.001), oviposition activity (P<0.001), and hatch success (P<0.001) in the parent generation. Survival (P<0.018), oviposition activity (P<0.001), and hatch success (P<0.001) were likewise strongly reduced in parents fed on SGE-immunized rabbits. Ovary extract-fed parents experienced less pronounced, but significant reductions, in survival (P<0.018) and hatch success (P<0.034). Surviving progeny were most strongly impacted by feeding upon MGE-immunized rabbits. Our study suggests that manipulating host immune response may be a suitable technique for reducing Cx. pipiens mosquito survival and fecundity, and subsequently the potential risk of disease transmission by this species.