Sandflies

External anatomy and classification

Sandflies form a distinct subfamily within the family Psychodidae. Externally, these are very small insects whose bodies are densely covered with yellowish hairs.

Main morphological features of the adult:

• Head: small, with two large black compound eyes located on the sides.
• Limbs: legs are long and visually very thin.
• Wings: broad with pointed tips. They are densely covered with hairs, but scales are completely absent.

These insects inhabit primarily tropical and subtropical climates, although they are occasionally found in temperate zones.

Biology and life cycle

Both blood-sucking and non-blood-sucking species exist among sandflies. Females feed on the blood of humans and more than 300 different animal species, including mammals, birds, reptiles, and amphibians. Interestingly, they attack both warm-blooded and cold-blooded creatures.

Females are characterized by a gonotrophic cycle similar to that of mosquitoes: the ovaries begin to develop exclusively after a blood meal, and the egg maturation process proceeds strictly in parallel with food digestion. Most females die of exhaustion immediately after their first oviposition.

Oviposition occurs 2–10 days after the blood meal. Development proceeds with complete metamorphosis:

1. Larva: has a worm-like shape and molts 4 times during growth.
2. Pupa: an immobile stage about 3 mm long that lasts exactly 10 days.
3. Imago: the adult insect.

Breeding sites are dark, dry or humid shelters rich in organic matter. These include the crawl spaces of residential buildings, livestock facilities, soil cracks, and bird nests. Sandflies often breed in the burrows of animals: rodents (rats, gerbils, susliks), tortoises, porcupines, and jackals.

Medical and epidemiological significance

Sandflies act not only as ectoparasites, but also as crucial vectors of dangerous pathologies.

During a bite, toxins are introduced into the wound with the insect's saliva, causing the attack to be very painful. The clinical picture of a bite includes itching that can persist for 1 to 2 weeks, local redness, and noticeable skin swelling. A blister forms at the center of the lesion, which ruptures when scratched and becomes covered with a dense crust.

The main danger lies in the fact that sandflies (including the species Phlebotomus papatasii) are specific vectors of the causative agents of the following diseases:

• Cutaneous and visceral leishmaniases.
• Pappataci fever.
• Bartonellosis.

Control measures and prevention

Preventive measures are aimed at interrupting the chain of transmission. The vector in this case is insects of the genus Phlebotomus.

Personal prophylaxis (protection against bites):

• Regular use of repellents and wearing protective clothing.
• Fitting windows and ventilation openings with screens.
• Using bed canopies and mosquito nets. It is important to use nets with very fine mesh, as sandflies can penetrate standard barriers due to their small size.

Public prophylaxis:

• Sanitary and epidemiological reconnaissance and elimination of breeding sites: timely garbage removal, elimination of waste heaps, high-quality room repairs (sealing cracks in floors, walls, and soil).
• Vector control: treatment of habitats and breeding sites of winged insects (basements, cracks, rodent burrows) with insecticides.
• Control of natural reservoirs: to prevent zoonotic cutaneous leishmaniasis, rodent extermination (gerbils, susliks) is carried out around settlements. To control visceral leishmaniasis, infected dogs are identified and treated (or culled).
• Specific prophylaxis: in endemic areas, leishmanization may be used—a prophylactic vaccination with a live culture of the cutaneous leishmaniasis pathogen. This method is rarely used nowadays.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Peculiarities of the life cycle of cutaneous and visceral leishmaniasis pathogens within the sandfly body.
• Clinical picture and differences of Pappataci fever from other arboviral infections.
• Mechanism of the toxic action of sandfly saliva during a bite and the development of a local allergic reaction.
• Methods of sanitary and epidemiological reconnaissance and monitoring of sandfly population numbers in endemic foci.
• Specific prophylaxis: history of application and reasons for abandoning mass leishmanization.

Other topics in the "Medical Arachnoentomology" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.