Psoroptes ovis

Psoroptes ovis
Class	Arachnida
Order	Acariformes
Family	Psoroptidae

Also known as:

Scab mite

Predilection site

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

Introduction

Psoroptes ovis are astigmatic, non-burrowing mites of the class Arachnida. They are 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, resulting in further trauma.

Hosts

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

Identification

The adult Psoroptes are around 0.75mm in length and oval in shape. They have three-jointed pedicles, each with suckers on the ends; also known as pulvilli.

The legs of adult females are all approximately the same length. However, in the males the fourth pair of legs is significantly shorter than the rest. The males also tend to be smaller then the females.

The males may also be identified via copulatory suckers and paired posterior lobes. The males attach to deutonymphs (second moult after larval stage) in a process called copula. The males then remain in copula until the females moult for the final time. Copulation then occurs.

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.

Transmission is generally from direct contact with infected animals, but indirect transmission may also occur.