Species-Specificity in Thermopreference and CO2-Gated Heat-Seeking in Culex Mosquitoes

Combining thermopreference (Tp) and CO2-gated heat-seeking assays, we studied the thermal preferendum and response to thermal cues in three Culex mosquito species exhibiting differences in native habitat and host preference (e.g., biting cold and/or warm-blooded animals). Results show that these species differ in both Tp and heat-seeking behavior. In particular, we found that Culex territans, which feed primarily on cold-blood hosts, did not respond to heat during heat-seeking assays, regardless of the CO2 concentration, but exhibited an intermediate Tp during resting. In contrast, Cx. quinquefasciatus, which feeds on warm blooded hosts, sought the coolest locations on a thermal gradient and responded only moderately to thermal stimuli when paired with CO2 at higher concentrations. The third species, Cx. tarsalis, which has been shown to feed on a wide range of hosts, responded to heat when paired with high CO2 levels and exhibited a high Tp. This study provides the first insights into the role of heat and CO2 in the host seeking behavior of three disease vectors in the Culex genus and highlights differences in preferred resting temperatures.

Culex Mosquitoes at Stormwater Control Measures and Combined Sewer Overflow Outfalls after Heavy Rainfall

Mosquito borne diseases are increasingly problematic as climate change continues to alter patterns of precipitation, flooding, and temperatures that may favor mosquito habitats. Stormwater control measures (SCMs), ecologically sustainable methods of stormwater management, may have varying impacts on Culex mosquitoes, such as in areas with combined sewer overflows (CSOs). We studied spatial and temporal associations of SCMs and Culex mosquito counts surrounding the SCMs, stratifying our examination amongst those that do/do not use pooling and/or vegetation, as well as surrounding CSO outfalls after heavy rainfall (≥95th percentile) during summer 2018. Results indicate Culex mosquito counts after heavy rainfall were not significantly different at SCMs that use vegetation and/or ponding from at those that do not. We also found a 35.5% reduction in the increase of Culex mosquitoes the day of, and 77.0% reduction 7–8 days after, heavy rainfall at CSO outfalls treated with medium SCM density compared to those without SCMs. Our results suggest that SCMs may be associated with a reduction in the increase of Culex mosquitoes at the CSO outfalls after heavy rainfall. More research is needed to study how the impacts of SCMs on mosquito populations may affect human health.

‘Crush Programme’ as Part of Combined Control Programme for Culex Mosquito in Both North and South Dhaka City Corporation

not available Bangladesh Med J. 2020 Sept; 49(3) : 53-56

Culex (Diptera: Culicidae) Mosquitoes in Jazan Region, Saudi Arabia, and Their Molecular Identification

Morphological characteristics have been the gold standard method to identify mosquito species. However, morphological identification has many limitations including lack of expertise and damaging of external characters due to improper specimen handling. Therefore, we used the polymerase chain reaction technique (PCR) as an integrated tool to identify Culex mosquito species to establish a more precise and reliable identification system related to their spatial distribution in Jazan region. We identified Culex mosquito species and subspecies using taxonomic keys, and then we used the polymerase chain reaction technique (PCR) as an integrated tool to confirm and refine the list of Culex mosquito species in the region. Phylogenetic trees were constructed for the identified species, and their distinctive clustering was compared with their reference’s species in the GenBank. We identified 7026 adult Culex mosquitoes belonging to 4 species. Culex tritaeniorhynchus was the predominant species (45%), followed by Cx. quinquefasciatus (32%), then Culex sitiens (20%), and Cx. pipiens (3%). The most infested areas by Culex in the region were Gizan and Sabya. The PCR achieved 100% success in identifying the four Culex mosquito species. We also report the molecular identification of Cx. quinquefasciatus and Cx. pipiens species for the first time in Jazan region while the molecular identification of Cx. tritaeniorhynchus and Cx. sitiens was reported for the first time in Jazan region and the whole Saudi Arabia. This study utilized for the first time PCR to identify Culex mosquito species in Jazan region. The PCR is a complementary and integrated taxonomy-based identification tool for mosquito species. This integration has the capacity to promote and enhance vector surveillance and control programs, as well as defining the genetic diversity of species in the region.

Genital Filariasis - A Recurred Case of Post Operated Hydrocele

Lymphatic filariasis, commonly termed as elephantiasis has been recorded since ancient Indian, Chinese, Egyptian and Persian writings.1 It is caused by a slender thread like nematode called Wuchereria bancrofti belonging to super family filaroidea.2 It exists in two morphological forms: Adult form and larvae. The adult form has a predilection for intrascrotal lymphatic vessels in hosts; thus hydrocele is one of the most common manifestations of bancroftian filariasis.3 Individuals having circulating microfilaria are outwardly healthy but have the ability to transmit infection to others through mosquito bites (Culex quinquefasciatus) 1 In developing countries like India, occurrence of genital filarial hydrocele is more common in people living in bancroftian endemic areas or in people who were previously operated for eversion of sac. We hereby report a case of hydrocele fluid with microfilaria- an incidental finding on microscopy. Wuchereria bancroti a filarial nematode inhabiting the lymphatics and transmitted through vector - culex mosquito. We hereby present a case of recurrence of genital filariasis. The patient presented with swelling of the left scrotal region with pain of dragging type. On evaluation, eosinophilia was not seen. He had a history of right hydrocele 28 years back. The aspirated hydrocele on direct microscopic examination showed presence of actively motile microfilaria which was confirmed on Giemsa staining. Recurrence is more common in bancroftian filarial endemic areas.

MEDIAN LETHAL CONCENTRATION (LC50) EKSTRAK DAUN SIRSAK (Annona muricata Linn) TERHADAP LARVA Culex sp DI KOTA KUPANG

The Culex mosquito is a species that can creates health problems for humans and animals. The handling efforts of the vector is very important to reduce the impact caused by this vector. One of the plants that has the potential as a larvicide is soursop leaves (Annona muricata L.). This study aims to determine the effect of soursop leaves (Annona muricata L.) extract on the mortality of Culex sp larvae and LC50 value to killing 50% Culex sp larva. The study was conducted from March to June 2020. This study used 7 treatment groups which 5 groups tested the effectiveness of soursop leaves extract and 2 control groups. The research data was analyzed using the Probit test to determine the LC50. The results showed that soursop leaves extract (Annona muricata L.) was effective in killing Culex sp larvae with LC50 value is 0.736%.

Molecular Identification and Insecticide Resistance Status of Culex mosquitoes collected from blocked drainages in Lagos State, Nigeria

Background: Culex mosquitoes are important vectors of several human pathogens causing infections such as lymphatic filariasis and several viruses. Poor and blocked drainage system can lead to impediment in water flow, leading to the artificial creation of larval habitats for Culex mosquitoes. Culex mosquitoes has the ability to breed in organically polluted water bodies and exhibit high resistance to insecticides. Therefore, this study assessed the species and insecticides susceptibility status of Culex breeding in blocked drainages in Lagos State. Methods: Culex mosquito larvae were collected from blocked drainages in three Local Government Areas (LGAs) of Lagos State, Nigeria, using standard WHO technique. The physicochemical parameters of the larval habitats were also recorded. Collected mosquito larvae were raised to adult, 2-3 days old. Glucose fed adults female mosquitoes were exposed to permethrin (0.75%) and DDT (4.0%) WHO insecticide test papers. Morphological identification was carried out using standard keys and molecular identification of Culex pipiens sub-species and kdr genotyping was carried out using PCR Results: High level of resistance was recorded with mortality r ate after 24 hour s for DDT ranging from 20% to 32% while permethrin ranges from 14% to 36%. The pH of the all the Culex mosquito larva habitats ranges from 7.38±0.11 to 7.62±0.29, while TDS ranges from 592.6±79.1 to 655±68.1. A total of 1113 Culex pipiens mosquitoes that were identify morphologically, some were selected for molecular identification using PCR assays, out of which 96.2% were identified as Culex p. quinquefasciatus while 3.7% were unidentified. Knockdown mutation (L1014F) was not detected in DDT and pyrethroids resistant Cx. quinquefasciatus in this study. Conclusion: Unplanned ur banization, inadequate w ater su pply and inefficient solid w aste and sewage management practices can result in the creation artificial larval habitats for Culex mosquitoes leading to potential outbreak of Culex mosquito borne diseases. The resistance to DDT and permethrin insecticides in Cx. quinquefasciatus in Lagos State may represent a threat towards the efficacy of ITNs and other forms of vector control such as indoor residual spraying in the future.