3 STUDIES ON ACARI. 



in size from a millet seer! up to the dimensions of a walnut. Numerous 

 specimens of Demodex in various stages of development are to be found 

 in the cheesy or fluid contents of the nodules. The above account is 

 condensed from that of Griffiths, who states that badly infected animals 

 should be slaughtered and the other animals dipped once a week in 

 1-200 Cooper's improved Cattle Dip; the cattle-sheds must also be 

 thoroughly disinfected. Any animals suffering from the disease should 

 be isolated. 



In a later paper Griffiths points out that many of the cattle 

 suffering from Demodectic mange are also infected with a more serious 

 complaint, '" dermatitis," due to bacteria. 



Van Saceghem has seen cases of Demodectic mange in the Belgian 

 Congo aflecting indigenous cattle, and also animals imported from 

 Belgium and India (Zebu Cattle). The disease is characterised by 

 comedons occurring principally round the ears, on the sides, shoulders, 

 intercrural space, etc. The size of the comedons varies from that of 

 the head of a pin to that of a fowl's egg. The disease progresses slowly 

 and does not seem to affect the general health of the animal. Infected 

 cattle should be isolated and treated with arsenical baths. According 

 to Van Saceghem this disease is sometimes confused with contagious 

 dermatosis (a much more serious complaint caused by a bacterium). 



The pustules, or nodules as they are called by some observers, may 

 be situated in the thickness of the skin instead of on the surface. 

 A large number of animals in a herd are sometimes found to be 

 suffering from Demodectic mange, from which it would seem to be 

 infectious. The general health usually does not seem to be much 

 affected. It is probable that the more serious cases of disease 

 attributed to Demodex by Geoffrey and one or two other observers, are 

 really due to infection with some bacterium. 



Stiles states that the damage to the hides due to the enlarged holes 

 caused by Demodex bovis lessens their value very considerably. The 

 disease seems fairly common in the United States. 



Demodectic mange in Pigs. — Stevenson says of D. phylloides that 

 " it bores into the hair-follicles and sebaceous glands, causing pustules 

 that enlarge, rupture, and leave sores and ulcers on the skin. This 

 disease spreads from the snout, over the neck, the under part of the 

 chest and abdomen, and over the flanks and inner parts of the legs ; [other 

 parts may also be affected, however]. Its deep location in the skin 

 protects the parasite from ordinary treatment." He also says that 

 " government inspectors have frequently withheld hogs from the 



