External parasites can be as big of a problem as internal parasites and they can cause problems with your goats. The below will give you a better understanding on mites that affect goats.
Mites belong to the family class which includes spiders and ticks. Like spiders, mites have 4 pair of legs. Mites are usually microscopic in size and their body and legs are covered with long hairs. Goats can be host to three different types of mites, the non-burrowing Psorptes and Chorioptes mites and the Sarcoptic mites that burrow into the skin.
Infections of Psorptes mites, also known and called mange or scab mites usually start on the shoulders the back or the tail area. These mites prefer areas that are well covered by hair. As the course of the infection develops they will spread to other part of the body. Psorptes cuniculi mites (which at most times affect rabbits) prefer to live inside the ears. This is a very contagious mite.
Psorptes mites do not burrow into the skin. These mites have piercing mouth parts that they use to puncture the skin and to suck lymph. This stimulates an immune reaction by the host and the area swells and serous fluid will seep to the surface creating a crust and scabs. The hair or wool will fall out or the goat will pull it out when biting at the very itchy lesions.
These Psorptes mites do not prefer to live on the bare crusty patches so they will migrate to the edges extending the infection outward. Skin scrapings to identify this mite needs to be made at the edges of the crusty lesions. Long standing infections can cause weight loss. Psorptes mites are identified by their long, segmented pedicles.
The life cycle is typical of most Psorptes mites where the female lays eggs at the edges of crusty lesions hatching in 1 to 3 days. If eggs are laid away from the skin they take longer to hatch or may die. Larvae feed for several days after hatching then molt to a nymph stage. These nymphs will molt in another 3 to 4 days into young females or males where usually there are about twice as many females than males. Mating takes place shortly after the molt and lasts only for 1 day or less. The female mite will molt again about 2 days later then will begin laying eggs in another day. This whole cycle takes only 9 days after she first hatched from the egg. The female will live for 30 to 40 days, laying about 5 eggs every day.
This type of mite commonly called a mange mite, causes tail or foot mange and it does not burrow into the skin. Chorioptes mites are not species specific. Different species of this genus can be found on cattle, sheep and goats and the different species can interbreed with each other. Although the species that usually infect goats is called Chorioptes caprae, it is probably the same as the species that infects sheep and cattle.
Infections of Chorioptes caprae the species that infects goats usually begins on the lower legs, later spreading to the hindquarters. Infections cause itching, and crust and scab formation. The life cycle is very similar to Psorptes mites, but is completed in about 3 weeks.
This type of mange mite burrows into the skin often spending the entire life cycle within burrows. Sarcoptes scabei is the species that infects most mammals. An infection begins in hairless regions or regions of short hair usually on the face or ears.
The female Sarcoptes scabei burrows into the skin, and lays 40 to 50 eggs, 4 to 5 a day. The eggs hatch in 3 to 5 days producing six-legged larva. The larva leaves the breeding tunnels and wanders on the skin or remains in the breeding tunnels and develops to the nymph stage. Those that reach the surface may die, or they can make shallow pockets in the skin tissue to feed and molt to several nymph stages which can also wander on the surface and make new pockets or extend the molting tunnels. Adult males and females form about 17 days after the eggs were first laid.
The female remains in her molting pocket until fertilized by a male then extends it into a breeding tunnel, or returns to the skin surface to create a new tunnel and then begins laying eggs. Mature females do not live much longer than a month. Wandering larvae, nymphs and fertilized females spread the infection on the host and to other hosts. They cannot survive off the host for more than a few days.
As they pierce the skin to feed on lymph fluid and skin cells they cause a great deal of irritation, itching, and scratching which worsens the condition. Crusts form on the skin and then the skin becomes thickened and wrinkled and the hair falls out. Lesions in the skin begin to develop in just a few days after infection, but the intense itching typical of Sarcoptic mite infection does not begin for a month or so later. The fecal pellets of the mite are responsible for the host inflammatory response. These mites prefer areas where there isn’t much hair such as the face of goats and ears although in long standing infections the mites can spread to all parts of the body.
The signs include bare skin, which is thick and wrinkled and covered in dry crusts. Early in the infection small raised red bumps and fresh exudates can be seen. To identify these mites in the microscope deep scrapings of skin must be made down to the point of drawing blood. It still might be difficult to find live mites in the burrows.
Goats may rarely get infections of this mite commonly called an itch mite. Found more commonly on sheep, these very tiny, round mites — about half the size of a Sarcoptes mite — spread very slowly over the course of 3 to 4 years on the individual animal. It can cause a mild irritation, dry, scaly skin and weaking of the wool in sheep. Beware – Can infect humans!