Hypoderma spp. (1)

Question 1

What is the common name?

Answer 1

Warble fly

Heel fly

Ox warble

Cattle grub

Question 2

What are the hosts?

Answer 2

Cattle

Possibly humans

Question 3

Describe adults

Answer 3

Large

Bee-like

Short-lived

1 pair of lungs

Vestigial mouthparts

Question 4

Describe third instars

Answer 4

Barrel shaped

2.5-3 cm long

Dirty white in color - newly emerged

Rapidly turn black brown

Bear short spines

Question 5

Describe eggs

Answer 5

Slender

White

About 1 mm long

H. bovis - laid singly

H. lineatum - laid in rows of 6 or more

 - Reaches host by series of hops along eggs
 - Remains on lower limb while laying eggs
 - Animals may be unaware of presence

Question 6

Explain the life cycle

Answer 6

Adults glue eggs on hairs of legs of cattle

H. lineatum - active at the beginning of summer for 2 months

H. bovis - takes over through the remainder of the summer

First instars

 - Less than 1 mm
 - Hatch in a few days
 - Burrow through skin
 - Migrate through CT tissue
 - H. bovis - larvae accumulate in epidural fat of spinal cord
 - H. lineatum - larvae accumulate in submucosa of esophagus 

Migrate to subcutaneous tissue of back, cut breathing hole in skin

Appose spiracles

Molt 2x, growing larger

3rd instar spends 2 months in warbles (backs of infested cows)

Fully developed larvae enlarge breathing hole

 - Emerge through them
 - Fall to ground to pupate

Adult emerge from pupal case 1 month later, immediately seek mates

Females lay eggs and die

PPP: 1-2 weeks

Question 7

What is the site of infection for larvae?

Answer 7

Suncutaneous tissue of back (warbles)

Question 8

What is the site of infestation of eggs?

Answer 8

On hairs of legs

Question 9

Describe the Pathogenesis

Answer 9

3rd stage larvae under skin - damage/perforate adjacent tissue
- Necessitates trimming/downgrading carcass

Greenish gelatinous tissue - “Butcher’s jelly”
- Infested esophageal submucosal tissues

Larvae of H. bovis die in spinal canal -> release of highly toxic proteolysin -> PARAPLEGIA

Death of H. lineatum larvae in esophageal wall -> BLOAT (esophageal stricture) and FAULTY REGURGITATION

Buzzing noise of adults -> Panic in animals -> Injury

Question 10

How do you diagnose?

Answer 10

Identify parasite

Question 11

How do you treat and prevent?

Answer 11

Systemic MCLs (ivermectin, doramectin, Moxidectin)/Organophosphates (coumaphos, fenthion) - kill larvae in early stages of 
                                                                         migration

Treatments given in fall before H. bovis larvae reach spinal cord - TIMING CRITICAL
- Increase damage by treating at wrong time, cause larvae to die in
spinal cord

Question 12

What is important about Hypoderma spp.?

Answer 12

It is ZOONOTIC