Blowflies, screwworms, flesh flies, bot flies

Question 1

Define myiasis

Answer 1

Myiasis is the invasion of tissue or organs of host animals by larval flies usually known as maggots or grubs

Question 2

What are the two forms of myiasis?

Answer 2

Cutaneous myiasis (screwworms, blowflies, flesh flies, skin bots)

Internal myiasis (nose bots, stomach bots, cattle grubs)

Question 3

Cyclorrapha: Blow flies

Where do Blow flies lay their eggs and where are their larva developing?

Answer 3

Eggs are laid in wounded, infected, or soild skin of mammals, Larvae are developing directly in the decaying organic matter

Question 4

What is a common feature of all Blowflies?

Answer 4

All are attracted to dampness and bacterial growth (odor) on the skin and hair coat

Question 5

List the species of blowfly which is the most common fly associated with carrion in the northern climes

Answer 5

Calliphora sp.

Question 6

Name the blowfly most commonly associated with wool maggots and cutaneous myiasis in other animals

Answer 6

Lucilia sp.

Question 7

Can Blowflies be useful?

Answer 7

Yes

Blow flies are commonly used as surgical maggots for debridement therapy for horse wounds!

Question 8

Cyclorrapha: Screw worm

1. List the important general features of screwworms
2. How does one go about identifying a screwworm larvae?

Answer 8

1. They all are obligate ectoparasites; Adult females only mate once
2. Identification of the characteristic dark pigmented tracheal trunk

Question 9

What is the natural range for the screwworm fly?

Answer 9

Through the southern states of the US down

Question 10

1. List the name of the eradication program for screwworms?
2. How do they eradicate these worms?

Answer 10

1. SWASS (Screwworm Adult Suppression System)
2. They preform a large scale sterilization of male flies

Question 11

Cyclorrapha: Flesh flies

Where do flesh flies lay their eggs and where are their larva developing?

Answer 11

Because flesh flies are larviparous they lay their larva directly on the area of interest

They are facultative parasites so they can lay their eggs on: wounds, living tissue, excrement, garbage, and decaying vegtable matter

Question 12

What are the two genus of flesh flies which we talked about in class?

Answer 12

Genus Sarcophaga

Genus Wohlfahrtia

Question 13

What about the genus wohlfahrtia is important?

Answer 13

Wohlfahrtia sp. are obligate parasites which penetrate the normal skin of a newborn and grow in a hypodermal pocket

Question 14

1. How does one go about treating a Wohlfahrtia infection (infestation?)?
2. How do you prevent this form occuring?

Answer 14

1. Need to clip and clean with antiseptic wash the wound. Removal of the larvae needs to occur as well.
2. Crutching (clipping hair) and avoid wounds (surgery) during fly season

Question 15

Cyclorrhapha: Bot flies

What are some general features of all bot flies?

Answer 15

All cause obligatory myiasis

Larval stages are long-lived

Highly host and site-specific

Adults are short-lived

Question 16

1. What is the scientific name for the Rodent skin bot?
2. Geographically where is it found?

Answer 16

1. Cuterebra sp.
2. Found throughout N. America

Question 17

What is the general life cycle of a Cuterebra sp.?

Answer 17

Adults lay eggs alone rabbit runs and rodent burrows –> larvae enter the host through some body opening –> migrate through to the skin –> drop out and pupate in the ground

Question 18

Cyclorrapha: Nose bots

1. What is the species which is found in sheep?
2. Where is the egg deposited?

Answer 18

1. Oestrus ovis
2. Larvae will be deposited in the nostrils of sheep

Question 19

How doesOestrus ovis exit the nostrils?

Answer 19

Oestrus ovis exits the nostrals by being blown out or by manually backing out

Question 20

What are some clinical signs associated with Oestrus ovis?

Answer 20

Head shaking

Chronic nasal discharge

Loss of appetite

Question 21

Cyclorrapha: Cattle grubs, warble fly, or heel fly

What genus do these flies belong in?

Answer 21

Hypoderma sp.

Consists of the common name flies the cattle grubs, warble fly, or heel fly

Question 22

Where is parasitisum of the hypoderma sp. (cattle grub, warble fly, heel fly) occur?

Answer 22

In cattle raised throughout the US, EU, and Asia

Question 23

1. Where do Hypoderma sp. flies lay there eggs?
2. Name the to species of Hypoderma we covered in class and when they occur

Answer 23

1. They glue their eggs to hairs on the legs of cattle
2. H. lineatum - occurs in April-June ; H. bovis - occurs from June - rest of the summer

Question 24

What is the life cycle of the Hypoderma lineatum fly?

Answer 24

Larvae penetrate the skin directly or through a hair follicle –> will migrate between the fascial planes of muscle and along CT –> accumulate in the submucosa of the esophagus –> will over winter here then proceed to the back –> here they will form a hole at the skin surface and warble until undergoing two molts –> falling off and pupating

Question 25

What is the life cycle for *Hypoderma bovis*?

Answer 25

Larvae penetrate the skin directly or through a hair follicle --\> **will follow nerves below the skin --\> larvae will acumulate in the spinal cord and migrate around the epidural space** --\> then proceed to the back --\> here they will form a hole at the skin surface and remain until March-June --\> falling off and pupating in the dirt

Question 26

What are your biggest concerns when treating with ivermectin for Cattle grubs?

Answer 26

Treating during the larval stage (inflammatory stage) or when in the spinal cord. This can lead to death of the larval --\> **anaphylaxis** **\*Key is to treat prior to larva reaching the esophagus or spinal cord (at the end of fly season (late August))**

Question 27

Cyclorrapha: Stomach bots 1. What is the genus of stomach bots? 2. Are they obligate or facultative parasites?

Answer 27

1. *Gasterophilus sp.* (stomach bots) 2. Obligate parasites of equids

Question 28

Name the species we discussed in class belonging to the genus *Gasterophilus?*

Answer 28

* G. intestinalis* * G. nasalis* * G. hemorrhoidalis*

Question 29

List where on the horse each species of *Gastrophilus* lays their eggs

Answer 29

* *G. intestinalis* * *​*lay their eggs on the hairs of the forelegs and shoulders * *G. nasalis* * *​*Deposits eggs on the hairs of the intermandibular space * *G. hemorrhoidalis* * *​*Deposits eggs on the short hairs of that adjoin the lips

Question 30

List where on the horse each species of *Gastrophilus* what is required for hatching

Answer 30

* G. intestinalis * ​Grooming (moisture and friction) * G. nasalis * ​Hatch spontaneously in 5 to 6 days * G. hemorrhoidalis * Hatch when they contact moisture

Question 31

List where on the horse each species of Gastrophilus resides in the stomach

Answer 31

* G. intestinalis * ​Around the boundary of the glandular and non-glandular stomach * G. nasalis * Pyloric portion of the stomach and anterior duodenum * G. hemorrhoidalis * In stomach and duodenum

Question 32

What is one unique feature of *Gastrophilus hemorrhoidalis*

Answer 32

Before being passed in the third larval stage in the feces it will **regrasp the rectal mucosa and stay about one week**