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.

Uganda, Africa, 1996

WHO/TDR/Crump

Nigeria, Africa, 1998, 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 (3-6 min)

• Must take blood meal every few days.

Disease Vector• 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

Maddening itching, depigmentation (leopard skin), and thickened skin

© Copyright 1997 OCP/APOC/WHO.

Onchocerciasis ControlOnchocerciasis ControlVector 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

• 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.

DRUG MODE OF ACTION

CONTROL

• 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 burrows

Rodent reservoir

hosts

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.

• 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 - manifestationsLEISHMANIASIS - manifestations

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 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.

Leishmaniasis – Cause and EffectLeishmaniasis – Cause and Effect

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

A bottle of capsules of miltefosine, the first oral drug for treating visceral leishmaniasis.

TREATMENT

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 ControlVector 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 Biting Midges – Medical ImportanceImportance

• 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.