Notes. 395 



the earlier observations of fanners and others can be explained on 

 this assnniption. The actnal species that transmits horse-sickness is 

 not yet known, bnt there are many good I'easons for snspecting 

 mosqnitoes. One g-enns that appears to be particnlarly suspicions is 

 Ochlerotatns, and observations in regard to its life-cycle and mode 

 of living accord very well with the established facts regarding- the 

 appearance and spread of horse-sickness. 



The question of tlie virus reservoir has not yet been settled. It 

 appears that in some instances the immune horse may still harbour 

 the infection. Possil)ly donkeys, dogs, and goats also serve as 

 carriers. 



The patliological changes in the various forms of horse-sickness 

 are very fully described. Separate sections are devoted to the 

 pulmonaiy or dunkop form, the cardiac or dikkop form, and the 

 mixed form. 



A further section deals with the clinical symptoms of the disease. 

 Four types of horse-si(d<ness are distinguished ; the first type is the 

 horse-sickness fever. The temperature curve is typical, but, ai)art 

 from that, the animals show practically no clinical symptoms. The 

 second type is the puknonary or dunkop horse-sickness, which must 

 be considered as the nn)st dangerous form. The most striking 

 symptom is the accelerated respiration. The third type is the 

 oedematous or cardiac or dikkop form of horse-sickness, which is 

 generally less deadly than the former type. This form owes its name 

 to the swellings which appear on the head (especially above the eyes) 

 and sonn^times on the body. The fourth type, which is fortunately 

 rare, is simply a combination of the two preceding types, and almost 

 invariably ends fatally. Very full accounts of the symptoms in these 

 diiferent forms of the disease will be found in the article. 



Complications are sometimes encountered in cases of horse- 

 sickness. One of the commonest is a paralysis of the gullet 

 (oesophagus) ; in severe cases the animals are entirely unable to 

 swallow. Other complications are colics and paralysis of the optic 

 nerve. The disease may be further complicated by an attack of 

 biliary fever. 



The nature of immunity in horse-sickness is very fully discussed, 

 and mention is made of the breakdowns in immunity (relapses or 

 aanmanings) that are of frequent occurrence. This question has 

 received very careful attention, and the results of numerous experi- 

 ments are detailed. It is of interest to note that even the so-called 

 hyperimmune horses, i.e. horses that have received at least 10 litres 

 of virus, may show relapses and about 5 per ciMit. of them may die. 

 In the case of ordinary immune horses the nuntulity is higher (7.3 

 per cent.). The main difficulty in this connection is that immunity 

 against one virus will not always protect an animal against another. 

 A horse that has had a relapse (aanmaning) is better salted than one 

 that has had only one attack of horse-sickness. 



Treatment of horses with drugs has very little chance of success. 

 As a matter of fact, it seems to be extremely advisable to leave the 

 sick animal severely alone; such animals frequently clioke when 

 drenching is attempted. 



The preventive treatment is of far greater importance. Two 

 ways can be followed : (1) Precautions may be taken to prevent horses 

 being bitten by infected carriers (possibly mosquitoes), or (2) the 



