Transcript Other Biting Flies

Other Biting Flies
Black-Flies, Biting Midges and
Sandflies
Family: Simuliidae
(Black-Flies, Buffalo Gnats, Turkey Gnats)
• 1600 species in 24 genera
• 1-5 mm long
• Variable in color, many are
black.
• 9-12 segmented antennae
• Prominent scutum
• Characterisitc wing venation
Importance
• (1) Annoyance (bite and persistence)
• (2) “Black Fly Fever” – reaction to salivary secretions.
• (3) Onchocerciasis “River Blindness”
Life Cycle
Eggs of Simulium damnosum attached to vegetation in running water.
Adults typically emerge in 8-12 days, depending on local temperature.
Larval Stage
Simulium naevei larvae
attached to a crab.
Nigeria, Africa, 1998, WHO/TDR/Crump
Uganda, Africa, 1996
WHO/TDR/Crump
Collecting blackfly immatures
Blackfly larvae clustered on a
stick in moving water
Adult Stage
Feeding Behavior
• Can be zoophilic
• Aggressive feeding
• Long engorgement time (36 min)
• Must take blood meal every
few days.
Disease Vector
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This is a 3 factor disease
Parasite:
Reservoir:
Vector:
Onchocerciasis
• Non-fatal dermal and ocular disease
• 95% of all cases worldwide occur in Africa in poor rural
areas, approx. 17 million affected
• Three main symptoms (occur 1-3 yrs after initial infection):
• Skin lesions (microfilariae in dermis)
• Painless nodules (where tissues thin, bone)
• Eye lesions (blindness – assoc. with dead
microfilaria)
Blindness caused by
onchocerciasis
© Copyright 1997 OCP/APOC/WHO.
Maddening itching, depigmentation
(leopard skin), and thickened skin
Onchocerciasis Control
Vector Control - The principal method for controlling
onchocerciasis has been to break the cycle of transmission by
eliminating the black fly. Simulium larvae are destroyed by
application of selected insecticides through aerial spraying of
breeding sites in fast-flowing rivers. Once the cycle of river
blindness has been interrupted for 14 years the reservoir of adult
worms dies out in the human population, thus eliminating the
source of the disease.
Ivermectin Treatment - To complement vector control
activities, the drug ivermectin is distributed where needed through
a community directed approach. Ivermectin kills the larval worms
that cause blindness and other onchocercal manifestations and
acts to decrease transmission as well. Ivermectin became
available in 1987 to complement blackfly control activities.
New villages in
areas formerly
uninhabitable
because of river
blindness
The result has been
increased activity and
productivity in many
of these areas
DRUG MODE OF ACTION
• Ivermectin (Mectizan®)- binds to glutamate gated chloride
channels in the parasites’ nervous system, causing them to
open.
• Albendazole - works by keeping the worm from absorbing
sugar (glucose), so that the worm loses energy and dies.
• Diethylcarbamazine – causes hyperpolarization of nerve
membrane and flaccid paralysis of the nematode, worms are
removed by normal peristalsis.
CONTROL
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This is one of the success stories!
Used to be a disease with no solution (WHO)
Ivomec (from Merck) – vector control
Treat larval habitats (Bacillus thuringiensis istaelensis BTI).
• There are many fly control programs in the United States.
Family: Phlebotominae
(Phlebotomine Sand-Flies)
• Two genera –
• Transmit
leishmaniasis
(worldwide)
• Transmit sandfly fever
virus (Mediterranean)
• Transmit Carrion’s
disease (bartonellosis)
- Peru, Ecuador and
Columbia
Lutzomyia longipalpis feeding
SANDFLIES
• Worldwide distribution
• 700 species in 5 genera
• Three genera contain bloodsucking species
• Most important genera are Phlebotomus and
Lutzomyia
Important Vectors of Leishmaniasis
Lutzomyia longipalpis
Central and South America
Phlebotomus argentipes
Middle East
Phlebotomus chinensis
China
Phlebotomus sergenti
India
Phlebotomus papatasi
Mediterranean
Lutzomyia verrucarum s.l. Central and South America
Lutzomyia intermedia
Central and South America
Life Cycle
• Egg  Larvae  Pupae  Adult
• Eggs laid in cracks and crevices
– Ground, stable floors
– Base of termite mounds
– Cracks in masonry
– Poultry houses
– Leaf litter, forest trees
• Larvae feed on decaying orgainic matter.
Sandfly Pupa
Sandfly Larvae
SANDFLIES: Adults
• Differentiate between Phlebotomus and Lutzomyia
by where (geographically) they are collected
• Very small (1.3-3.5 mm), very hairy, with long thin
legs
• Body tends to be brown/light brown in color
• Short mouthparts adapted for sucking –
• Wings held over the body when at rest – generally
poor fliers
• Short mouthparts inhibit biting through clothes.
Dogs can act as
reservoirs of
Leishmania
parasites.
They also exhibit
symptoms of
infection.
Rodent
reservoir
hosts
Rodent burrows
Rio de Janeiro.
Sandfly habitat in Jacarepagua district on the outskirts of Rio de
Janeiro.
Caused by obligate intracellular
protozoa of the genus Leishmania.
Leishmania donovani
promastigotes
Leishmania donovani
extracellular amastigote
During bloodfeeding, female sandflies inject the infective promastigote stage.
Promastigotes that reach the puncture wound are phagocytized by
macrophages and transform into amastigotes. Amastigotes multiply in
infected cells and affect different tissues, depending in part on the
Leishmania species. This originates the clinical manifestations of
leishmaniasis.
Sandflies become infected during blood meals on an infected host when they
ingest macrophages infected with amastigotes. In the sandfly's midgut, the
parasites differentiate into promastigotes, which multiply and migrate to the
proboscis.
LEISHMANIASIS - manifestations
• Two main forms of disease:
(1) cutaneous leishmaniasis (CL)
(2) visceral leishmaniasis (VL)
• Two less common forms also occur:
(1) mucocutaneous leishmaniasis (MCL), due to L.
braziliensis infection.
(2) diffuse cutaneous leishmaniasis (DCL), which produces
disseminated and chronic skin lesions.
LEISHMANIASIS - pathology
Cutaneous forms of the
disease normally produce
skin ulcers on the
exposed parts of the body
such as the face, arms
and legs. The disease can
produce a large number of
lesions - sometimes up to
200 - causing serious
disability and leaving the
patient permanently
scarred.
LEISHMANIASIS - pathology
• mucocutaneous
forms of leishmaniasis ,
lesions can lead to
partial or total
destruction of the
mucose membranes of
the nose, mouth and
throat cavities and
surrounding tissues.
LEISHMANIASIS - pathology
Visceral leishmaniasis also known as kala azar
- is characterized by
irregular bouts of fever,
substantial weight loss,
swelling of the spleen
and liver, and anemia
(occasionally serious). If
left untreated, the fatality
rate can be as high as
100%.
Leishmaniasis – Cause and Effect
• Leishmaniasis is related to environmental changes such
as deforestation, building of dams, new irrigation
schemes, urbanization and migration of non-immune
people to endemic areas.
• It seriously hampers productivity and socioeconomic
progress and epidemics have significantly delayed the
implementation of numerous development programs.
• This is particularly true in Saudi Arabia, Morocco, the
Amazon basin and the tropical regions of the Andean
countries.
Currently leishmaniases is prevalent in four
continents; considered to be endemic in 88
countries, 72 of which are developing countries:
• all visceral leishmaniasis cases occur in
Bangladesh, Brazil, India, Nepal and the Sudan
• mucocutaneous leishmaniasis occurs in Bolivia,
Brazil and Peru
• cutaneous leishmaniasis cases occur in
Afghanistan, Brazil, Iran, Peru, Saudi Arabia and
Syria
Distribution
TREATMENT
A bottle of capsules of
miltefosine, the first oral
drug for treating visceral
leishmaniasis.
A number of clinical studies to
test the effectiveness of
injectable paromomycin against
visceral leishmaniasis have
been carried out in India, where
the standard antimonial
treatment, sodium
stibogluconate, is not very
effective and failure rates are
high. Results show it to be safe
and effective.
Paromomycin
cream, used
for topical
application on
lesions in the
treatment of
cutaneous
leishmaniasis
Vector Control
Family: Ceratopogonidae
(Biting Midges)
• Very small 1-2 mm
• Wings fold flat over
abdomen; light and dark
patches.
• Eggs laid in damp
substrate (muddy edges)
• Larvae feed on decaying
organic matter
• Short mouthparts,
females only bloodfeed
Midge Larvae
Biting Midges
Culicoides pupae and adult
Culicoides habitat – many larval habitats similar
to that of mosquitoes
Biting Midges – Medical
Importance
• PEST impact
• Mansonella perstans and M. streptocerca (filarids)
transmitted by Culicoides sp.
• M. ozzardi transmitted by C. furens
• Filariae develop
• Oropoche virus (Brazil, Trinidad and Colombia)
• Blue tongue virus
• May be transmitted by
midges of the Culicoides
family and is endemic to
beach areas in the
Caribbean where these
pests are common.
• Most infected people are
completely asymptomatic.
However, joint pains,
headaches, coldness of the
legs, inguinal adenitis, and
itchy red spots have been
described in conjunction
with infection.
Mansonella ozzardi
distribution
• Infections by Mansonella perstans, while often asymptomatic,
can be associated with angioedema, pruritus, fever,
headaches, arthralgias, and neurologic manifestations.
• Mansonella streptocerca can cause skin manifestations
including pruritus, papular eruptions and pigmentation
changes.
Control
• Personal Protection
• Insecticidal spraying (requires heavy rainfall)
• Difficult to reduce larval breeding sites.