20 Mites Injurious to Domestic Animals. 



those in poor condition, and are more easily cured. As is well-known, 

 sheep-scab is treated by dipping, and many patent dips are on the 

 market. The wool should be clipped from the affected parts before 

 dipping. Most of the dippings fail to destroy the eggs, hence it is 

 necessary to give a second immersion at an interval of about eight 

 days in order to destroy any mites that have developed (before they 

 start laying eggs themselves). According to Stockman and Beare 

 creosote dip is very effective against the eggs. 



Sheep in the first stage of the disease often show no visible 

 signs, hence the necessity of systematic dipping. 



Much advice on the dipping of sheep is given in leaflets Nos. 61 

 and 145 issued by the Ministry of Agriculture. Sheep-scab is a 

 notifiable disease, and it is the duty of the owners of infected sheep 

 to give notice of the fact to the nearest police constable. 



A. W. Shilston has written an excellent account of the habits 

 of Psoroptes communis, var. ovis, based on observations in South 

 Africa (Third and Fourth Reports of the Division of Veterinary 

 Research, Dept. of Agriculture, Union of South Africa, Nov. 1915, 

 pp. 69-98). He points out that the all-important factor in the 

 eradication of sheep-scab is the destruction of every mite on the 

 sheep themselves, and that to ensure this more efficient dipping is 

 necessary than has usually been employed in the past. He says 

 that the interval between the first two dippings should be ten days, 

 and that a third dipping is advisable. The expense of this third 

 dipping is slight compared to that occasioned by a recurrence of 

 the disease, possibly some months later, owing to the survival of a 

 few acari on one or two sheep which may have passed too rapidly 

 through the tank, or were not completely immersed. " In addition, 

 a third dipping would greatly lessen the risk of reinfection from 

 kraals or sleeping places. Acari are known to be unable to live 

 for more than four weeks apart from sheep (in the experiments all 

 were dead in twenty-one days), and eggs will not hatch after ten 

 days, so that by the time the third dipping is given say twenty to 

 twenty-four days after the first acari in the kraals would be dead 

 or too feeble to infect recently dipped sheep. It would, of course, 

 be unwise to neglect to thoroughly disinfect all places in which 

 scabby sheep had been confined, but absolute cleansing of the sheep 

 is the essential point in the eradication of the disease. The necessity 

 of treating every sheep in the flock, and not only those visibly 

 affected, is obvious." The above observations, of course, refer to 

 sheep as kept in South Africa under different climatic conditions 

 from those of this country. Shilston especially recommends the June 



