Phlebotomine sand flies
The name sand fly is a misnomer and wrongly suggests to the layman that he or she may be at risk of leishmaniasis while on holiday on the beach. There is further confusion because in some parts of the world midges (genus Culicoides) or black flies (family Simulidae) are called sand flies.
A distinction must therefore be made for the vectors of the leishmaniases which are correctly termed phlebotomine sand flies. They are grouped in the suborder Nematocera of the order Diptera (two-winged flies). Below that, the classification is not universally agreed, but they are generally put in the Family Psychodidae, subfamily Phlebotominae.
Six genera are generally recognised of which only two are of medical importance, namely Phlebotomus of the Old World (divided into 12 subgenera), and Lutzomyia of the New World, (divided into 25 subgenera and species groups). All proven vectors of the leishmaniases are species of these two genera.
Phlebotomus is based on the Greek phleps, phlebos meaning ‘vein’ and refers to the blood sucking habit of sand flies.
Lutzomyia was named in honour of Adolfo Lutz (b.1855), a German entomologist who worked in Brazil and, in 1912 with his colleague Arturo Neiva, named the New World vector of human visceral leishmaniasis and canine leishmaniasis, now known as Lutzomyia longipalpis.
Although sand flies are principally found in the warm parts of the world including southern Europe, Asia, Africa, Australia and Central and South America, their distribution extends northwards to just above latitude 50ºN in south west Canada and just below this latitude in northern France and Mongolia.
Their southernmost distribution is at about latitude 40ºS, but they are absent from New Zealand and the Pacific islands. Their altitudinal distribution is from below sea level (by the Dead Sea) to 3300 m above sea level in Afghanistan.
- Very common in warm parts of the world
Phlebotomine sand flies are vectors of all forms of leishmaniasis of both dogs and the human population in southern Europe, Africa, Asia and the Americas. WHO estimated that the global prevalence of all forms of human leishmaniasis is 12 million cases and that the annual incidence is 1.5 – 2 million cases.
Of human diseases caused by protozoal parasites, visceral leishmaniasis alone comes second in public health importance (after malaria) as measured by DALYs (Disability Adjusted Life Years).
Sand flies are also vectors of the sand fly fever group of viruses (Bunyaviridae: Phlebovirus) seven serotypes of which have been isolated from humans in Central America, South America, Southern Europe, North Africa and the Far East. They are also probable vectors of:
- the Changuinola virus (Reoviridae: Orbvirus) of humans in Panama,
- three serotypes of the vesicular stomatitis virus (Rhabdoviridae: Vesiculovirus) in the Western Hemisphere
- the Chandipura virus (Rhabdoviridae: Vesiculovirus) of India and West Africa.
In the mountain valleys of the Andes in Peru, Ecuador and Colombia, sand flies are vectors of a bacterium (Bartonella baciliformis), the causative organism of bartonellosis (= Oroya fever and/or verruga peruana) in the human population. Untreated, the case-fatality rate of Oroya fever is 10-40%.
- Sand flies (P papatasi) that rest and breed in burrows of the great gerbil have been controlled in the Central Asian Republics by poisoning the gerbils, then ploughing up the burrows and cultivating the steppes for winter wheat or cotton
Control via other means
- Vaccination – none.
- Scalibor deltamethrin-impregnated dog collars have been shown not only to deter sand flies from biting dogs, but also to kill sand flies coming to feed.
- Adult flies of both sexes
- For faunal surveys, adult flies are killed and stored in 60% ethanol. Long preservation will make the specimens hard and difficult to mount on slides. They can be transferred to Berlese’s fluid and stored indefinitely.
- For studies on isoenzymes and/or DNA, adult flies are stored in liquid nitrogen where they will remain in perfect condition for many years. These specimens can also be used for faunal surveys or for dissection and isolation of leishmanial parasites.
Transport of samples
- If tubed specimens in ethanol are to be posted, the tubes must be completely filled to avoid damage.
- Specimens in liquid nitrogen can be carried on aircraft if they are in containers designed for the transport of bull sperm.
- Phlebotomine sand flies are small with a body length seldom exceeding 3 mm. Their colour ranges from almost white to almost black. Three features make them easy to recognise: when at rest, they characteristically hold their wings at an angle above the abdomen; they are hairy; and, when coming to engorge, they typically hop around on the host before settling down to bite. Unlike mosquitoes, their attack is silent.
- Ostfeld R S, Roy P, Haumaier W, Canter L, Keesing F & Rowton E D (2004) Sand fly (Lutzomyia vexator) (Diptera: Psychodidae) populations in upstate New York: abundance, microhabitat, and phenology. J Med Entomol. 41, 774-778.
- Gossage S M, Rogers M E & Bates P A (2003) Two separate growth phases during the development of Leishmania in sand flies: implications for understanding the life cycle. Int J Parasitol. 33, 1027-1034.
- “>Killick-Kendrick R (1999) The biology and control of phlebotomine sand flies. Clinics in Dermatology. 17, 279-289.
- Killick-Kendrick R et al (1997) Protection of dogs from the bites of sand flies by deltamethrin collars for the control of canine leishmaniasis. Medical and Veterinary Entomology 11, 105-111.
Other sources of information
- Killick-Kendrick R (2002) Phlebotomine sand flies: biology and control. In: World Class Parasites, vol 3 Leishmaniasis. (Ed. J.P. Farrell), Boston: Kluwer Academic Press, 33-43.
- Rutledge L C & Gupta R K (2002) Moth flies and sand flies. In: Medical and Veterinary Entomology, San Diego: Academic Press, 147-161.
- Killick-Kendrick R (1999) The biology of sand fly vectors of Mediterranean canine leishmaniasis. In: Canine leishmaniasis: an update. Ed. R Killick-Kendrick. Proceedings of a Canine Leishmaniasis Forum, Barcelona (Sitges), 28-31 January, 1999 Wiesbaden: Hoechst Roussel Vet, 26-31.
- Lane R P (1993) Sandflies (Phlebotominae). In: Medical Insects and Arachnids. (Eds R P Lane & R W Crosskey), London: Chapman & Hall, 78-119.
- Robert Killick-Kendrick MPhil PhD DSc DIC FIBMS FRES CIBiol FIBiol, Department of Biological Sciences, Imperial College of Science, Technology and Medicine, London, UK.