Psoroptes ovis

Predilection site

Skin; particularly on legs, feet, and the base of the tail.

Introduction

Psoroptes ovis are astigmatic, non-burrowing mites around 750μm (0.75mm) in length, and oval shaped. They are extremely pruritic, and cause a contagious skin disease, as well as a loss in body condition. They also cause the host to rub and bite the infected areas, causing further trauma.

Hosts

Sheep, cattle, goats, horses, rabbits, and camelids.

Life Cycle

The eggs are relatively large, and within around 2 days transform into a hexapod larva. The larvae then moult into a protonymph , which then subsequently moults into a tritonymph. Finally the tritonymph moults to become a mature adult.

Each stage takes around 2 days to complete. The total duration from egg to adult, takes around 10 days, but this figure can longer

Psoroptes cuniculi (Copyright Joel Mills, Wikimedia Commons)

Identification

• Males identified by copulatory suckers and paired posterior lobes

• Males attach to deutonymphs (second moult after larval stage) in a process called copula
  • Males remain in copula until females moult for the last time
  • Copulation occurs

• Life cycle last 14 days

• Transmitted by direct contact between sheep

• Indirect transmission can also occur