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LOIASIS (Contact) Please CLICK on
image & underlined links for details: Loiasis is a
nematode disease vectored to humans by flies of the
family Tabanidae. Occurance of the
disease is primarily in forested areas of Nigeria, Ghana, Angola, Sudan,
Uganda, Guinea, Congo and the Cameroons.
The microfilariae are diurnally periodic and migrate to different
parts the body at different times of the day and night. When they are situated just below the skin
they can be transferred to tabanid flies that bite during the daytime. Service listed the principal vectors as Chrysops silaceus, C. dimidiatus, C. distinctipennis and C. longicornis. Following a blood meal some of the ingested microfilariae
that manage to survive digestion penetrate the intestinal wall and migrate to
the abdomen or thorax and head (Service 2008). After two molts they develop into a 3rd stage larva, which is
only 2 mm. in length. These move to
the thorax and head and after 7-15 days amass in the fly's proboscis. When a vector feeds on humans as many as
200 stage-3 larvae can be left on the skin.
Service (2008) noted that most of these die, but some pass through the
wounds made by the biting fly or even through skin abrasions. They migrate to connective tissue where
they mature in about three months.
Several months later the microfilariae can be found in the peripheral
blood. Reservoir hosts may involve forest simians that are bitten
by Chrysops centurionis and C. langi that are active at twilight or
nighttime. However, transmission to
humans is uncertain. CONTROL The Tabanidae are extremely difficult to control,
especially in areas where aquatic habitats cannot be practically reduced,
such as swamps and lakes.
Nevertheless, . Control
measures have involved draining swampland where the flies breed. Insecticidal control is also plagued by
the development of resistance and difficulties in locating principal breeding
areas. Service (2008) noted that some
control could be achieved with attractant traps for adults and the use of
repellents. = = = = = = = = = = = = = = = = = =
= = Key References: <medvet.ref.htm> <Hexapoda> Anderson, J. F. 1985.
The control of horse flies and deer flies (Diptera: Tabanidae). Myia 3:
547-98. Anthony, D. W. 1962.
Tabanids as disease vectors. IN: Biological Transmission of Disease
Agents. Academic Press, NY. p.
93-107. Braga da Rosa; Gustavo A.
2006. Predation
of hill topping horse-flies (Tabanidae) by birds in Brazil. Ornitologia Neotropical. 17: 619–622. Cheke, R. A., J. Mas & J. F. Chainey. 2003. Potential vectors of Ioiasis and other tabanids on the island
of Bioko, Equatorial Guinea. Med. Vet. Ent. 17:
221-3. Chippaux, J. P., B.
Bouchite, M. Demanov, I. Morlais & G. LeGoff. 2000. Density and
dispersal of the Loiasis vector
Chrysops dimidiata in southern
Cameroon. Med. & Vet. Ent.
14: 339-44. Eaton, Eric R.; Kaufman, Kenn (2007). "Deer
flies and horse flies". Kaufman Field Guide to Insects of North
America. Hillstar Editions. p. 284. Egri, A.; Blaho, M.; Kriska, G.;
Farkas, R.; Gyurkovszky, M.; Akesson, S.; Horvath, G. 2012. "Polarotactic tabanids find
striped
patterns with brightness and/or polarization modulation least
attractive: An advantage of zebra stripes". Journal of Experimental Biology. 215 (5): 736. Foil, L. D. 1989.
Tabanids as vectors of disease agents. Parasitology Today 5:
88-95. Legner,
E. F. 1995. Biological control of Diptera of medical
and veterinary importance. J. Vector
Ecology 20(1): 59_120. Legner, E. F. 2000.
Biological control of aquatic Diptera. p. 847_870.
Contributions to a Manual of Palaearctic Diptera, Vol. 1, Science Herald, Budapest. 978
p. Matheson, R. 1950. Medical Entomology. Comstock Publ. Co, Inc. 610 p. Middlekauff, Woodrow Wilson; Lane,
Robert S. 1980. Adult & Immature Tabanidae (Diptera) of California. University of California Press. pp. 1–2. Noireau, F., A. Nzoulani, D. Sinda & A. Itoua. 1990. Transmission indices of Loa
loa in the Chaillu Mountains, Congo. Amer. J Trop. Med. 43: 382-8. Padgett, J.J.; Jacobsen, K.H. (2008).
"Loiasis: African eye worm". Transactions of the Royal Society of
Tropical Medicine and Hygiene. 102 (10): 983–9. Quercia, O.; Emiliani,
F.; Foschi, F.G.; Stefanini, G.F. The
wasp-horsefly syncrome. European
Annals of Allergy and Clinical Immunology 40 (3): 61–63 Service, M. 2008.
Medical Entomology For Students.
Cambridge Univ. Press. 289 p Legner, E. F. 1995. Biological control of Diptera of medical and veterinary
importance. J. Vector Ecology 20(1):
59-120. Legner, E. F. 2000.
Biological control of aquatic Diptera. p. 847-870.
Contributions to a Manual of Palaearctic Diptera, Vol. 1, Science Herald, Budapest. 978 p. Thomson, M. C., V. Obsomer & J. Kamgno et
al. 2004. Mapping the distribution of Loa loa in Cameroon in support of
the African Programme for Onchocerciasis Control. Filaria J. 3: 7. Wilkerson, R.C.; Butler, J.F.;
Pechuman, L.L. (1985). "Swarming, hovering & mating behavior of male
horse flies & deer flies
(Diptera: Tabanidae)". Myia. 3: 515–546. |