PARASITES AXD 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 

 scabiei 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 ej T e. 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 

 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. 

 Unfortunately, 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. — In 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 



— San-optic manure mire. 

 (Magnified 100 times) 



