169 



without showing any symptom of ilhiess. It was not understood that 

 immunity has attained such a degree among Paraguayan cattle that 

 it forms a permanent barrier to any fatal invasion of the disease, which 

 in the country under review takes the form of a slight enzootic, only 

 occasionally appearing as a severe epizootic. It is a matter of common 

 experience in Paraguay that cattle reared on tick-free farms and 

 brought into the country almost invariably contract piroplasmosis. 

 On tick-infested farms young cattle that have a certain degree of 

 inherited resistance are observed to suffer from a primary attack 

 which confers a more or less lasting immunity in proportion to the 

 gravity of the infection, each re-infection renewing the immunity. 

 This resistance has undoubtedly saved Paraguayan cattle from 

 destruction far more than any prophylactic measures that the 

 Government could have devised. The widespread occurrence of the 

 tick in the country, however, constitutes an obstacle to the progress 

 of cross-breeding and the importation of the finer European breeds. 

 The absence of any official action has been the cause of the extensive 

 distribution of the tick in Paraguay ; according to historical informa- 

 tion, during the colonial period, particularly in the time of the Jesuits, 

 who possessed extensive ranches, ticks were unknown on the stock- 

 farms. Apparently the tick was introduced into the country in 1838 

 on cattle imported from Brazil. Since the colonisation period, the 

 principal source of wealth in Paraguay has been its cattle ; the presence, 

 therefore, of a dangerous enzootic which impedes the development of 

 its stock is of the most serious importance. While the acclimatisation 

 of the best British breeds is a complex problem, by far the greatest 

 obstacle is the tick, which is responsible for the deaths of 80 or 90 per 

 cent, of imported cattle. The efforts of private individuals having 

 proved ineffectual in controlling the tick, the Government has begun 

 to institute public dipping tanlcs similar to those in use in the 

 Argentine. The ports of exportation for cattle have been fixed by the 

 Government and are enumerated in this paper ; a dipping-tank has 

 been established at each and a veterinary officer is present, who is 

 entrusted with the inspection of the animals and the supervision of 

 the dipping-tanlis. A conference of delegates from the neighbouring 

 republics is to be held under the auspices of the Sociedad Ganadera 

 del Paraguay, for the purposes of studying the occurrence and means 

 of eradicating the tick, when its exact geographical distribution will 

 be determined and the question of establishing a convenient sanatorium 

 for promoting international exchange of stock will be discussed. It 

 is hoped that public and private action will combine to transform 

 present conditions and promote the development of the country's 

 resources. 



Beyro (A. F.). Perjuicios causados por la Garrapata del Ganado 

 Vacuno : Inmunizaci6n contra la Tristeza : Lo que se hace en 

 Estados Unidos. [Losses of Cattle caused by Ticks : Immunisa- 

 tion against Tick-fever : What is being done m the United States.] 

 — Anales Soc. Rural Argentina, Buenos Aires, li, no. 4, June 1917, 

 pp. 329-333, 1 fig. [Received 12th September 1917.] 



It is estimated that stock-breeders in the southern United States 

 lose some £8,000;000 annually owing to ticks, besides the loss of 



