166 
The Cure of Sheep Scab. 
the sheep being placed in, and taken out of, the bath. Never allow 
the sheep to be exposed to rain for at least one day after dressing. 
(Signed) P. R. Gordon, . 
Chief Inspector of Stock in Queensland. 
Office of Chief Inspector of Sheep, 
Brisbane, November l.S, 1877. 
[In addition to the information contained in Mr. Gordon’s com- 
munication, flock-masters may be further interested in the follow- 
ing details, which are taken from Dr. Cooper Curtice’s work. The 
Animal Parasites of Sheep, published by the United States Depart- 
ment of Agriculture at Washington. 
Scab is a disease due to the presence of minute creatures which 
lead a parasitic life on the skin of their hosts. It is caused by the 
inflammation they excite in penetrating the skin, which they do in 
order to procure food, and also to find suitable conditions for the 
reception and hatching of their eggs. There are at least three 
species of these parasites, which are known as Acari, the disease they 
cause being called vlcariasis. The species which attack sheep include : — 
Sarcoptes scabiei, de Geer, var. ovis, causing head scab ; 
Psoroptes communis, Fiirst, var. ovis, causing common scab ; 
Chorioptes communis, Verheyen, var. ovis, causing foot scab. 
The life-history of these parasites is in general very similar. 
They attack the external skin of the animals in which they live by 
biting it. Soon after scabs are formed. Under these scabs the 
pests lay their eggs, which hatch out after two or three days, the 
progeny becoming adult in fifteen days. Each mature female is 
estimated to lay about fifteen eggs, two-thirds of which produce 
females. When hatched, the young invade fresh skin and repeat 
the life of their parents. The extension of scab disease is due to 
the migration and rapid propagation of the scab parasites. On the 
individual sheep the disease usually spreads as a constantly growing 
patch. The infected .animal sometimes scatters the scabs by 
scratching, and thereby originates new centres of infection. The 
multiplication of the pests ceases only at the death of the sheep, or 
by killing the parasites by means of suitable remedies. 
As common scab is the most frequent form of the disorder, and is 
that treated of by Mr. Gordon, the remaining remarks refer exclu- 
sively to it. 
Common scab is caused by a parasite known as the scab-mite or 
itch pest — Psoroptes communis, Fiirst., var. ovis. It is much larger 
than the Sarco^Jtes, which causes head scab, being visible to the 
unaided eye. 
Disease. — Of the diseases of sheep, scab is one of the most feared 
by the flock-master. So insidious is its attack, so rapid its course, 
so destructive its effects, and so difiicult is it to exterminate, that 
it has justly earned the distinction of being more injurious than any 
other disease caused by external parasites. Scab alone, of the para- 
sitic diseases, has become the subject of legislation in most countries, 
