Parasitology - Nuisance & Biting Flies

Question 1

Aside from fleas & lice, what are the other types of insects (Phyla: Insecta) that qualify as parasites of the skin? What is their order?

Answer 1

Diptera - flies

Question 2

In what family of Diptera insects do nuisance & biting flies fall?

What are the main nuisance & biting flies species or genera?

Answer 2

Family: Muscidae

Nuisance flies:

• Musca domestica* - house fly, standard fly
• Musca autumnalis* - face fly
• Hydrotaea -* head fly

Biting flies:

• Stomoxys* - stable fly
• Haematobia* - horn fly

Question 3

What family of Diptera contains the nuisance & biting flies?

Answer 3

Muscidae

Question 4

What are the species or genera of nuisance flies?

Answer 4

Musca spp: M. domestica, M. autumnalis

Hydrotaea irritans

Question 5

Musca domestica is also known as house fly or standard fly. Its morphological features are the “standard” against which all other flies are compared.

Describe M. domestica’s appearance in terms of:

size

thorax

abdomen

mouthparts

Answer 5

Size: ~7.6 mm

Thorax: Grey with longitudinal stripes

Abdomen: Yellow with one black stripe

Mouthparts: No forward-pointing proboscis. Rather, a sponge-like labellum to suck up food broken down by vomited enzymes

Question 6

What is M. domestica’s life cycle? How does this life cycle contribute to M. domestica’s ability to transmit disease?

Answer 6

Life cycle (12 days mimumum): Eggs laid in dung → Hatch into larvae → Pupate in manure → Adults (can survive overwintering by hibernating)

The fact that the fly is hatches and pupates in manure means it can easily pick up enterobacteria and other bacteria found in faeces such as E. Coli, Shigella, Salmonella. It can also transmit enteroviruses and some helminths.

Question 7

Aside from disease transmission, what other pathogenic significance do houseflies (M. domestica) have?

Answer 7

They cause “fly worry” in cattle, which can cause production losses in terms of reduced weight gain, reduced milk yield, etc.

Question 8

What is the most numerous nuisance fly causing fly worry in cattle?

Answer 8

Musca autumnalis, aka face fly

Question 9

What is Hydrotaea irritans and what species does it bother the most?

Answer 9

H. irritans is a nuisance fly in the Musca family that mainly bothers sheep. It is also found on cattle in some areas.

Question 10

How does H. irritans differ from the domestic house fly, M. domestica, in appearance?

Answer 10

H. irritans has a green abdomen

Question 11

Why is H. irritans especially bad for sheep?

Answer 11

H. irritans, aka “head fly”, swarms around the sheep’s head, rasps the skin before sponging up secretions and exudate with its labellum.

This can drive the sheep to self-injury called “broken head”, leaving it susceptible to secondary infection & blowfly strike.

Question 12

What is the difference in life cycle between the M. domestica and the H. irritans?

Where do they lay their eggs?

Answer 12

Life cycle of M. domestica is about 12 days. They lay eggs in dung.

Life cycle of H. irritans is one year because the larvae overwinter, pupate in spring and emerge as adults in summer. They lay eggs in rotting vegetation.

Question 13

What are the biting flies in the Musca family?

Answer 13

• Stomoxys calcitrans* - “stable fly”
• Haematobia irritans* - “horn fly”

Question 14

How do the mouthparts differ in nuisance flies and biting flies in the Musca family such as Haematobia irritans and Stomoxys calcitrans?

Answer 14

Haematobia irritans and Stomoxys calcitrans both have forward-pointing proboscis, like a hypodermic needle.

Question 15

What is the distinguishing behaviour of the stable fly, Stomoxys calcitrans?

Answer 15

It attacks all animals and humans. It “visits” (feeding on) hosts, but flies away and rests elsewhere.

Question 16

How does the stable fly differ in appearance from the M. domestica?

Answer 16

Instead of a grey thorax with black longitudinal stripes, it has a grey thorax with grey longitudinal stripes, and its abdomen is grey with black spots.

Question 17

How does the stable fly’s life cycle differ from M. domestica’s?

Answer 17

Its life cycle takes about one month instead of 12 days, and it lives for another month as an adult.

Like Hydrotaea irritans, it lays its eggs in rotting vegetation, like straw & hay.

Question 18

How does the behaviour of the biting fly Haematobia irritans (aka Lyperosia) differ from that of *Stomoxys calcitrans? *

Answer 18

“Resident” fly: spends most of time on host (usually cattle). Rests along back, shoulders & side, feeds on dewlap, udder & belly where skin is thinner.
- tend to “face downward” on back.

S. calcitrans is a “visiting fly”.

Question 19

Haematobia irritans (Lyperosia) & Stomoxys calcitrans look similar, but their life cycles are different in terms of where they lay their eggs. Haematobia, also known as “horn fly”, prefers to lay its eggs in a similar environment as M. domestica & M. autumnalis. Where is that?

Answer 19

In dung.

Haematobia irritans prefers FRESH cattle dung and emerges after just one week.

Question 20

Recap all the nuisance & biting flies in the Musca family.

Answer 20

Nuisance: labellum mouthparts

Musca domestica - house fly

Musca autumnalis - face fly

Hydrataea irritans - head fly, causes broken head in sheep

Biting: forward-pointing proboscis

Stomoxys calcitrans - grey stable fly, “visiting” fly

Haematobia irritans (Lyperosia) - horn fly, “resident” fly

Question 21

What are the biting flies that fall under the “forest flies & keds” category? They are also called “louse flies” because they look like lice.

Answer 21

Forest Flies:

Hippobosca bovis & Hippobosca equina - only attack cattle & horses

Sheep ked:

Melophagus ovinus - attacks sheep

Question 22

What is bad about the louse fly, Hippobosca equina, in terms of where it is found around horses and where it lives in the UK?

Answer 22

It tends to swarm around the perineal region of the horse.

Question 24

What is the difference between the sheep ked’s (Melophagus ovina) life cycle and the forest fly’s (Hippobosca bovis & H. equina) life cycle?

Answer 24

Sheep ked lifecycle is completely on host. Adult female ked deposits single larva in fleece → larval ked pupates in fleece → adult emerges a few weeks or months later, depending on temperature.

Forest flies’ lifecycle is mostly off the host. Adult fly deposits larva in soil → Larva pupate in soil → adult

Question 25

What are Tse Tse flies and where are they found?

What disease do they transmit?

Answer 25

Tse Tse are biting flies of the Glossinidae family. Both male and female leave painful bites.

They are found only in Africa.

They transmit Trypanosomes to cause fatal disease, “nagana”, in animals and “sleeping sickness” in humans.

Question 26

What is the appearance of the Tse Tse fly in terms of size, colour and wing venation?

Answer 26

See photo

Size: 6-13 mm (medium-sized)

Colour: Greenish thorax with yellow-brown abdomen

Wing Venation: “Butcher’s Cleaver”

Question 27

What is special about horse flies in terms of size, wing venation, mouthparts, life cycle & behaviour?

Answer 27

Size: They are BIG biting flies ~ 2.5 cm long (3x M. domestica)

Wing venation: Closed “discal” cell

Life cycle (one year): Eggs laid on leaves over H₂O →larvae fall into H₂O →return to land to pupate

Mouthparts: short, strong & down-pointing for slashing & sponging

Behaviour: only FEMALES suck blood

Question 28

What family of Diptera (order) do horse flies belong?

Answer 28

Tabanidae

Question 29

Besides Tabanidae (horse flies), which other biting flies lay their eggs on or near water?

Answer 29

Culicoides (midges), Simulium (black flies or buffalo gnats) & Culicidae (mosquitoes)

Culicoides midges - Eggs laid on plants near H₂O → larvae → pupae → adults

Simulium black flies/buffalo gnats - Eggs laid underwater → larva emerge & attach to water vegetation → pupate, floating to surface → adult emerges

Culicidae mosquitoes - Raft of eggs laid on water → larva hatch on water → pupate in water → adult

Question 30

What is the most important genus in the family Ceratopogonidae?

Answer 30

Ceratopogonidae are midges.

The most important genus is Culicoides, which cause sweet itch in horses and are vectors for viral diseases such as Blue Tongue and African Horse Sickness.

Question 31

How do Culicoides, in the family Ceratopogonidae, differ from appearance from M. domestica?

Answer 31

See photo.

They are very small, aka “noseeums” at 2-5 mm.

They are dark with humpbacked thorax.

They have mottled wings.

These are midges.

Question 32

Simulium are also known as black flies or buffalo gnats, even though they are very small (2-4 mm). Like midges (culicoides), they have arched, humpback appearance.

What is unique about their biting behaviour?

What is unique about their wings?

Answer 32

Only females suck blood.

They have clear wings with weak venation.

Question 33

The family Culicidae includes mosquitoes, which are always born on water (think of stagnant water!). What are three important genera?

Answer 33

Culex

Aedes

Anopheles

Question 34

What do mosquitoes (Culicidae) have in common with black flies & buffalo gnats (Simulium); and sandflies (Psychodidae) in terms of biting behaviour?

Answer 34

Only females suck blood.

Question 35

What are some diseases transmitted by Culicidae (mosquitoes)?

Answer 35

Human:

Malaria - plasmosis

Dengue fever

Animal:

arboviruses - eg., rabbit myxomatosis, equine encephalitis

parasites: Dirofilaria immitus

Question 36

Psychodidae is the family of sandflies. What are the two main genera of sandflies and why are they very important to vets in warm climates?

Answer 36

Phlebotomus (Old World)

Lutzomyia (New World)

They’re vectors for the protozoan parasite Leishmania, which causes the blood disease Leishmaniasis.

Leishmaniasis is an intracellular protozoal-parasite invasion of macrophages; the protozoan’s amastigote (later) stage transforms into promastigotes in sandfly’s gut.

Question 37

Which nuisance fly has the olive-green abdomen?

Answer 37

Hydrotaea irritans - head fly, affects sheep especially.