PARASITES AND PARASITIC DISEASES OF HORSES 39 
SARCOPTIC MANGE 
SARCOPTIC MANGE MITE 
The mites which cause sarcoptic or common mange of horses are 
small, white, or yellowish parasites known technically as Sarcoptes 
scabiet equi. (Fig. 27.) The female when full grown measures 
about one-fiftieth and the male about one-sixtieth of an inch in 
length. When placed on a dark background they are visible to the 
naked eye. The general form of the body is more nearly round 
than oval, and the bluntly rounded head is as broad as it is long. 
When mature, these mites have four pairs of short, thick legs, the 
fourth pair and usually the third pair also not extending beyond 
the margin of the body. Under a high-power miscroscope a number 
of short, backward-projecting spines 
may be seen on the upper surface of 
the body. 
The sarcoptic mites penetrate the 
upper layer of the skin and exca- 
vate burrows or galleries in which 
the mating of the sexes occurs and 
the eggs are laid. Each female may 
lay from 10 to 25 eggs during the 
egg-laying period, which probably 
lasts from 12 to 15 days. When that 
period is completed the female dies 
in her burrow. The entire life cycle 
is passed on the body of the host 
animal. The eggs hatch in from 3 
to 10 days, and the young mites 
after passing through several molts 
reach maturity and begin laying 
eggs in 10 or 12 days. 
As the average period of incuba- : 
tion on the animal is about four paamaie” a (cated (00 cee 
days, and the average period after 
hatching until egg laying begins is about 11 days, a new generation 
of mites may be produced in about 15 days. If the first treatment 
or dipping could be depended on to kill all the mites on the animal 
the time for the second treatment could be calculated accurately. 
Jnfortunately, the first treatment usually does not kill all the 
sarcoptic mites on the animal because of the difficulty of getting the 
dip or other insecticidal substances into the burrows and in contact 
with the mites. Practical experience has shown that the interval 
between treatments or dippings should be from five to seven days. 
Symptoms.—tin the early stages of sarcoptic mange in horses the 
first visible lesions usually occur on the neck or shoulders or around 
the head, but the disease may start on the breast, flanks, sides, or other 
parts of the trunk. From these parts the disease spreads until the 
entire surface of the body may become involved. 
‘The mites penetrate the upper layer of the skin, each female 
making a separate burrow or gallery, which usually extends to the 
sensitive tissues or “ quick.” The presence and activities of the mites 
