Gasterophilus spp. (1)

Question 1

What are the hosts?

Answer 1

Horses

Question 2

Describe adults

Answer 2

Up to 1.8 cm (large)

Short lived

Question 3

Describe 3rd stage larvae/instars

Answer 3

Found in feces

2 cm

Red or yellow with rows of spines - differentiate between species based on color and spines

Question 4

Explain life cycle

Answer 4

3-9 weeks - adult fly

G. intestinalis

 - Eggs deposited on hair of forelegs/shoulder
 - 1st instar hatches from egg
 - Licked by horse, attaches to tongue/lips
 - 3rd instars in non-glandular part of stomach and cardiac region
        - Color in feces - Red

G. nasalis

 - Eggs deposited on hairs of intermandibular area
 - 1st instar hatches spontaneously, crawls into mouth
 - 3rd instars attach around pylorus 
        - Yellow in feces

Oral cavity - develop to 2nd instars, swallowed

Develop to 3rd instars in stomach (G. intestinalis) or duodenal ampulla (G. nasalis)
- Can live for up to 12 months

Late spring these will pass out with feces to pupate soil

Question 5

What are the sites of infestation?

Answer 5

Larvae - attached to stomach

Eggs - on hair of forelegs/shoulders/intermandibular area

Intestines

Question 6

Describe the Pathogenesis

Answer 6

Adults - annoyance

Fly worry

Attachment of instars can provoke an inflammatory reaction

True pathogenic significance remains obscure

Question 7

How do you diagnose?

Answer 7

Differentiate based on color, spines, and location in host

Seen during gastroscopy

Identification of:

 - Larvae in feces
 - Eggs on hair

Adult fly activity

Question 8

How do you treat and prevent?

Answer 8

Eggs - removed from hair coat with special fine-tooth comb
- Process slow/laborious

Parasiticides effectively remove larval stages in equid

Question 9

What is the common name?

Answer 9

Bot fly larvae or instars

Bot fly