Sand Flies, Black Flies, and Midges

Announcements

Mucotaneous Leishmaniasis (espundia, Uta, chiclero)

• Found primarily in Brazil, Bolivia, and Peru. Probably in Paraguay as well.

• ‘uta’ – Quechua (Inca) for the nasal/oral disfiguration.

• Known from Incan pottery > 2,000 years old.

• Generally thought to be caused by the same Leishmania species as in cutaneous but is transmitted by different fly species. Different pathogen strains likely as well.

Result without treatment

Result with treatment

Reservoirs

• Dogs & rodents are efficient reservoirs.

• Dogs can acquire Leish. without sand flies through an unknown process. Early Stage Canine Leish.

End Stagesub corneal pustular dermatitis 

Prevalence• Prevalence increasing -

>500% increase in cases in the last 10 years.

• Now endemic in 88 countries

• Increase due to:– Expansion into new vector

habitat– Expansion of vector range– Coincident increase with

HIV.

Bartonellosis

• Etiological agent is Bartonella bacilliformis, a gram-negative bacterium.

• biphasic disease– phase 1: febrile disease– phase 2: hemolysis and/or verrucous skin lesions

(“verrucous” = “wart-like”)• Unique to humans, native to Andean South

America (Colombia, Equador, Peru).• Present in Pre-Columbian times, numerous

archelological artifacts dating >3,000 years ago, Peruvian mummies >6,000 years old show evidence of wide-spread outbreaks.

Bartonellosis• Historically a very confusing disease• Numerous names

– Phase 1 (Acute phase): Oroya fever (Peru), Guáitira Fever (Colombia). Untreated case fatality rate 40 – 90%

– Phase 2 (Chronic phase): Verruga Peruana, Muru Uncoy

– Carrión’s Disease. Low fatality rate.• Phase 2 symptomology historically

confused with measles and smallpox.• Traditionally only found between 500

m and 3,000 m elevations. Recently, a low-elevation strain has (re?)emerged & is typically monophasic.

Carrións Disease named after Daniel Alcides Carrión

• Peruvian medical student in the 1880’s

• From Cerro de Pasco

• Outbreak of Verruga Peruana among railroad workers.

• Went to investigate, with some friends …

National Hero

Carrións Disease has a restricted distribution now.

Bartonellosis Vectors

• Higher elevation forms: Lutzomyia verrucarum & peruensis in Peru, L. colombiana in Colombia

• Lower elevation forms are a different strain of the bacterium with low homology with the others. Probably a different vector species but it is unknown (may not be a sand fly).

Transmission is poorly understood

• Occurs during nocturnal blood feeding of vector

• Presumably via saliva and/or contaminated proboscis.

• Some adults (human) carry asymptomatic, nascent infections & act as the reservoir.

• Locals tend to react less than travelers. Outbreaks always associated with strangers coming into an endemic area.

Close relationship with El Niño climate event – outbreak occurs 1 – 3 months later.

Sandfly fever• Phlebovirus• Non-lethal, self-limiting. Noticeable only by immigrants.• Transmitted vertically (sandfly to egg) & horizontally to humans.

Vesicular Stomatitus – A growing threat in Kentucky

Black Flies

• Family Simuliidae• Larvae/pupae are aquatic

in flowing rivers/streams• Attach to substrate, move

on silk• Very difficult to

distinguish species morphometrically

• See text for photos

Black Fly Bites

• Can build up in big enough numbers that this is a problem.

• Irritation, exsanguination, and toxemia all occur.

• Bites often occur where clothing contacts skin.

• Telmophages

Main Medical Problem is Onchocerciasis

• River Blindness caused by Onchocerca volvulus• 99% of cases in Africa• 3rd leading cause of infectious blindness (trachoma is #1).

Transmission Cycle

External symptoms• Adult females clump together

& males enter to mate.• Clumping creates visible

nodules.Below is NOT O. volvulus. It is a Guinae Worm.

Occular involvement is the main issue

Occular Involvement

• Microfilarae migrate throughout epidermal tissues.

• Some end up in eye.• Cause lesions,

cataracts, retinal hemorrhages, corneal opacities (right), glaucoma.

• Involvement with a bacterial symbiont, Wolbachia.

Onchocerciasis Management

• Black fly control• WHO’s OCP

(Onchocerciasis Control Programme) and the 19-country APOC (African Programme for Onchocerciasis Control).

• Filarial control– Ivermectin: Paralyzes worms

but does not kill adults. Mectizan (Merk) in pill form.

– Antibiotics: Kills the Wolbachia symbiont

Biting Midges

• Order Ceratopogonidae

• “no-see-ums”: Very common in boggy areas, beaches (for this they are sometimes called “sand flies”).

• Many other names in your book (e.g. “jejenes”).

• For humans, the main problem is nuisance.

Biting Midges are mostly a veterinary problem.

• Blue Tongue (BT)

• Epizootic Hemorragic Disease (EHD)

• Both caused by orbivirus

• BT found mainly in domestic ruminants (esp. sheep & cattle), EHD mainly in wild ruminants (esp. white-tailed deer)

• Both transmitted by Culicoides spp.

EHD a growing threat to Kentucky White-tailed Deer

• Population has reached a point that could support an epidemic with large-scale sudden die-off.

• Incidence has increased dramatically in the last few years.

• 3,000 confirmed deaths in 2007, >4,000 in 2008. Actual number is probably much higher.

• Not a threat to humans but symptoms very similar to chronic wasting disease (which is a threat). Both are present in other states (esp. Michigan & Wisconsin). Deer are being imported from those states to KY.