Specific Parasites - Exam 1

2 species of bot flies in cattle and their general life cycle

1. Hypoderma lineatum (common cattle grub)

2. Hypoderma bovis (northern cattle grub)

Egg > larva (maggot) > pupa > adult

Describe the life cycle of Hypoderma lineatum

The adult flies lay eggs, commonly on the heels, which stick to the hair. The larvae burrow into the subQ and migrate to the esophagus (last months of the year). In the late winter/early months of the year, the larvae travel to the subQ along the back, where they eventually perforate through. Larvae are dropped to the ground and turn to pupa.

Describe the life cycle of Hypoderma bovis

The adult flies lay eggs in the hair. The larvae burrow into the subQ and migrate to the spinal cord (last months of the year), where they move about without detection by the cow’s immune response. In the late winter/early months, the larvae move to the subQ along the back and perforate through. Larvae drop and pupate.

How are cattle bot flies diagnosed?

The larvae cause lumps on the back of cattle, or eggs may be seen on leg hairs.

Pathogenicity of cattle bot flies

1. Decreased weight gain

2. Damage to hide and meat

3. Predispose to inflammation

4. Worry factor/trauma

Treatment for cattle bot flies

1. Ivermectin type dewormers

2. Pour-on insecticides - permethrins, organophosphates

When should cattle be treated for bot flies?

The 1st week of November (do not treat after January or could cause anaphylaxis)

Warble fly (Hypoderma bovis)