Diptera

Announcements• Presentations today from Philip Crain, Gordon Chaney

• Next Presentation is NEXT THURSDAY, Chris Gibson on Mosquitoes

• Reminder: Full Hour Exam Next Tuesday.

Exam Review - Material

• Material Covered for the Exam: Lecture & Reading material THROUGH today. – Lecture material– Text Readings (Chaps 1 – 13)

• Material NOT Covered– 5-min presentations– If we don’t complete the lecture material

today, then chapters not discussed will not be on the exam.

Exam Review - Format

Exam will have 3 General Parts1. Picture Questions

• Five or so picture questions, pictures will change every 15 sec. or so.

• For each picture, there will be 3 – 5 questions.

2. Non-Picture Questions• 20 – 25 multiple choice or “check all that apply”

3. Short-Answer• 5 – 10 questions that can be answered in a

sentence or two.

General Study Guide - 1

• What insects have been discussed so far (common names only)?– To what orders/families do they belong? Families are

important only if there are very few in the order, e.g. Heteroptera/Reduviidae/Triatominae.

• Which pathogens/diseases do these insects vector?– What is the transmission pathway?– What are the symptoms of the disease?– What type of pathogen is it? (e.g. bacteria, virus,

protozoan, rickettsia, etc.).

General Study Guide - 2

• For each insect/pathogen combination:– How prevalent/serious is the threat? – What host-pathogen-insect factors are

involved in the transmission-disease cycle?– What general categories/terms apply to the

various components?– In what situations would you expect to

encounter the problem (geographical location, season, ecological setting, specific sites/times of day, etc.).

– What are the general management options?

Current Status of Plague•Between 1998 and 2008, nearly 24,000 cases have been reported, including about 2,000 deaths

•In 2003, 9 countries reported 2118 cases and 182 deaths.

•98.7% of those cases and 98.9% of those deaths were reported from Africa.

•Most serious current epidemic is in the Congo (FKA Zaire).

• August, 2009, outbreak in Qinghai, China

US Human Cases

1970 - 1997

US normally has 10 – 20 cases/year

Diptera

• One of the largest orders of insects. • By far, the most medically-important order.• Only order to have significant presence in all

major categories of damage:– Direct:

• Biting – exsanguination• Invasion - myiasis• Toxins• Disturbance/Irritation

– Indirect:• Disease / pathogen transmission• Secondary Reactions - Allergies, weakening• Psychoses – entomophobia, dilussory parasitosis

General Characteristics of Diptera

• Holometabolus• One pair of flight wings,

one pair of halteres• Many larvae are

aquatic/semiaquatic • Adult mouthparts are

usually adapted for taking liquid food (some are non-functional or absent).

Nematocera vs. Brachycera

Character Nematocera Brachycera

Body shapeMosquito

like

House

Fly like

PupaeObtect Coarctate

Antennae cf. Fig. 10.4

Usually longer than the head

Usually shorter than the head

Principal Dipteran Families That We Will Discuss

• Psychodidae – Sand flies• Simuliidae – Black flies• Culicidae – Mosquitoes• Muscidae – House flies, Livestock_Flies• Glossinidae – Tsetse flies• Tabanidae – Horse flies• Hippoboscidae - Louse flies & Keds• Oestridae – Bot flies

Psychodidae - Psychodinae

• One of two subfamilies that have medical significance and this one is minor.

• AKA Moth flies, Drain flies.

• Non-biting species

• A few are sometimes nuisance species

• Drain flies can be problems in insect-sensitive areas.

Phlebotominae

• This subfamily has great medical significance• 700 spp. in 5 genera. • Female adults are blood feeders, about 1/3 to ½

the size of a mosquito, bite is somewhat more painful. Feed on blood to acquire protein for egg production.

• Males and females also feed on plant sap/nectar for carbohydrates.

• Very poor fliers, adults typically found at vegetation edges, immatures characteristically difficult to find.

Two groups of Phlebotomines

• New World Species – Those found in the Americas. Most important genus is Lutzomyia

• Old World Species – Those found outside of the Americas. Most important genus is Phlebotomus.

• Most of the species that feed on mammals can transmit a variety of disease (cf. Table 11.1)

At least two species in Kentucky

• L. shannoni feeds on mammals and L. vexator feeds on reptiles.

• First found in 2005 in very low numbers.

• Now common in Western Ky • Ky is the northern limit of the

range for most species.• Probably competent vector

of several pathogens.• Likely a more serious

veterinary threat than human one.

Leishmaniasis• Most serious disease transmitted by Phlebotomines.• Caused by protozoans in the genus Leishmania, several species &

many strains. • Leishmania is one of the 5 genera in the Trypanosomatida

– Another genus is Trypanosoma– All are parasitic on animals. Most are exclusively insect blood parasites.

• 12 million cases worldwide, 1.5 – 2million new cases/year. Increasing in prevalence.

• Causes characteristic lesions on the affected tissue • A group of diseases that are broadly classified into three forms:

– Cutaneous – Lesions on the skin, most common form, mainly disfiguring.– Visceral – Involvement of internal organs, especially the spleen & liver– Mucotaneous – Expression in the upper repiratory tract and/or oral mucosa.

South American forms are usually associated/preceded by one of the above two. Old world forms are not.

Cutaneous(Oriental sore, Delhi ulcer, Baghdad boil)

• Papule appears at the infection site 1-2 weeks (or as long as 1-2 months) after the bite.

• The papule gradually grows to form a relatively painless ulcer.

• The center of the ulcer encrusts while satellite papules develop at the periphery.

• The ulcer heals in 2-10 months, even if untreated but leaves a disfiguring scar.

Diagnosis is via skin biopsy which reveals vacuoles lined with

amastigotes. Leishmania spp. is confirmed via PCR.

Visceral Leishmaniasis(kala-azar, dumdum fever)

• Systemic form of the disease• Usually fatal if not treated.• Often relapses as kind of

cutaneous Leishmaniasis in survivors.

Profile view of a teenage boy suffering from visceral leishmaniasis. The boy exhibits splenomegaly, distended abdomen and severe muscle wasting.

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.

Exam is through this point

• Through Chapter 11, Excluding all sandfly-vectored disease EXCEPT Leishmaniasis.

• Includes all of Chapter 10 but you do NOT need to know the family names of the “minor medical or veterinary interest” groups beginning on p. 142. However, you might get a question on this material.