Culicinae Mosquitoes Overview

Culicinae Mosquitoes

• Subfamily contains 40 genera
• Important genera include Culex, Aedes, Haemagogus, Sabethes, Mansonia (medically significant). Others include Coquillettidia, Psorophora (less significant).
• Many are disease vectors, including yellow fever, dengue, filariasis, and arboviruses.

Culex Mosquitoes

• Found worldwide except extreme northern regions.
• Lay eggs in rafts (300 eggs) on water surfaces.
• Larvae have a long siphon with multiple subventral hair tufts.
• Adults have brown scales, simple tarsal claws, and a blunt abdomen tip.
• Breed in polluted water (drains, septic tanks, ditches).
• Vector of filariasis (Wuchereria bancrofti, Japanese encephalitis).
• Bites at night (nocturnal) and rests indoors/outdoors.

Aedes Mosquitoes

• Found worldwide, including arctic regions.
• Lay black eggs singly on damp surfaces (can withstand drying).
• Larvae have short siphons and one subventral hair tuft.
• Adults have distinctive black and white patterns on thorax, legs, and abdomen.
• Breed in container habitats (tree holes, tires, pots, water storage).
• Vector of yellow fever, dengue, chikungunya.
• Bites during the day and rests outdoors.

Haemagogus Mosquitoes

• Found in Central and South America.
• Breed in tree holes and bamboo stumps.
• Bites during the day, mostly in treetops.
• Vector of yellow fever.

Sabethes Mosquitoes

• Found in Central and South America.
• Breed in tree holes, bamboo, bromeliads.
• Bites during the day, mainly in the canopy.
• Vector of yellow fever.

Mansonia Mosquitoes

• Found mainly in tropical regions.
• Lay eggs under floating vegetation.
• Larvae attach to aquatic plants to breathe.
• Breed in swamps, marshes, ponds.
• Bites at night and rests outdoors.
• Vector of Brugia malayi filariasis.

Coquillettidia Mosquitoes

• Found mainly in tropical and some temperate regions.
• Larvae attach to plants (similar to Mansonia).
• Vector of Brugia malayi filariasis.

Psorophora Mosquitoes

• Found mainly in North, Central, and South America.
• Breed in flooded pastures and rice fields.
• Some species are predatory.
• Not major disease vectors but aggressive biters.

Medical Importance of Culicinae Mosquitoes

• Many cause severe biting in tropical and temperate regions.
• Large-scale control operations exist to reduce nuisance.

Yellow Fever

• Regions: Africa and tropical Americas.
• Transmission:
  • Sylvatic (forest): Monkey-to-monkey via Aedes africanus.
  • Rural (edge of forest): Monkey and human via Aedes bromelia, Aedes luteoceohalus.
  • Urban (cities): Human-to-human via Aedes aegypti.
• Vectors: Aedes (Africa, Americas), Haemagogus, and Sabethes (Americas).
• Control: Vaccination (17D mosquito).

Dengue

• Regions: Worldwide (50 million cases/year).
• Vectors: Aedes aegypti, Aedes albopictus.
• Transmission: Human-to-human (no animal reservoir).
• Types: Dengue fever, dengue hemorrhagic fever (severe).
• Control: Larval habitat reduction, genetic control (sterile male releases).

West Nile Virus

• Regions: Africa, Middle East, Europe, Americas.
• Vectors: Culex pipiens, Culex quinquefasciatus, Culex tarsalis.
• Hosts: Birds (primary reservoir), human & horses (dead-end hosts).
• Control: Mosquito reduction.

Japanese Encephalitis

• Regions: Asia, Papua New Guinea.
• Vectors: Culex tritaeniorhynchus, Culex vishnui (breed in rice fields).
• Hosts: Birds (primary), pigs (amplifying), humans (dead-end).
• Control: Vaccination, vector control.

Chikungunya

• Regions: Africa, Asia, Indian Ocean, Europe.
• Vectors: Aedes aegypti, Aedes albopictus.
• Hosts: Monkeys in Africa (possible zoonotic transmission).
• Control: Mosquito habitat reduction.

Filariasis

• Vectors: Culex, Aedes, Mansonia, mosquitoes.
• Forms:
  • Bancroftian filariasis (W. bancrofti): No animal reservoir.
  • Brugian filariasis (B. malayi): Reservoirs include monkeys, cats.
• Periodic Forms: Nocturnally periodic (Culex quinquefasciatus, Anopheles), Diurnally subperiodic (Aedes polynesiensis).
• Control: Mass drug administration (MDA), bed nets, vector control.

Control Strategies for Culicine Mosquitoes

• Aedes Control: Source reduction (eliminate breeding sites), larvicides (temphos, methoprene, Bacillus thuringiensis israelensis (Bti)), genetic control (sterile male release), vaccination (yellow fever).
• Culex Control: Sanitation improvements, insecticides (temephos, methoprene, chlorpyrifos), expanded polystyrene beads in pit latrines.
• Mansonia Control: Weed removal/herbicides to eliminate aquatic plants, granular insecticides for larval control.
• Filariasis Control: Mass drug administration (albendazole + ivermectin), insecticide-treated bed nets (ITNs), WHO's global program to eliminate lymphatic filariasis.

Black Flies (Simuliidae)

• Family: Simuliidae
• Found worldwide with >200 species in 25 genera.
• Medically important genus: Simulium
• Other genera: Prosimulium, Austrosimulium

Main Disease: Onchocerciasis (River Blindness)

• Vector:
  • Africa: Simulium damnosum complex, Simulium neavei
  • Central & South America: Simulium ochraceum, Simulium metallicum, Simulium exiguum
• Other transmissions: Simulium amazonicum (Mansonella ozzardi - filarial parasite, usually non-pathogenic).

General Characteristics

• Small (1.5–4 mm).
• Usually black, but some species have other colors/patterns.
• Humped thorax.

Head Features

• Females: Dichoptic eyes.
• Males: Holoptic eyes (touching).
• Males have larger upper eye lenses.
• Short, 11-segmented antennae.
• Short, inconspicuous mouthparts with hanging maxillary palps.

Biting Mechanism

• Labrum stretches skin.
• Mandibles and maxillae scrape and rupture blood capillaries.
• Blood is sucked up.

Wing Features

• Short, broad wings with few veins.
• No scales or prominent hairs.
• Colorless or nearly so.
• Wings rest over body like closed scissors.

Legs and Abdomen

• Legs with fine hairs, possible bands.
• Tarsi with simple claws.
• Short, squat abdomen with fine hairs.

Life Cycle of Black Flies

• Eggs: Triangular, black or brown, laid in flowing water.
• (Simulium ochraceum): Eggs scattered across water.
• Larvae: Cylindrical, swollen abdomen, attach to surfaces in flowing water.
• Pupae: Attached to underwater surfaces in cocoons.
• Adults: Emerge from pupae, fly long distances, lifespan several weeks.

Onchocerciasis Transmission

• Infected black fly bites human --> injects L3 filarial larvae.
• Larvae mature, form skin nodules.
• Adult worms produce microfilariae migrating through skin.
• Black fly bites infected person, ingests microfilariae.
• Microfilariae mature into infective L3 larvae inside fly, cycle repeats.

Onchocerciasis Symptoms

• Severe itching, skin thickening.
• Depigmentation.
• Eye infection and blindness.

Onchocerciasis Prevention

• Vector control (reducing black fly populations).
• Mass drug administration (MDA) with Ivermectin.

Control of Black Flies

• Personal Protection: Insect repellents, protective clothing, avoiding infested areas during peak biting times.
• Community-Level Control: Reducing breeding sites (removing vegetation, modifying water flow), larvicides (Bti), and MDA with Ivermectin.