to learn more about the disease and its effect 

 on swine. 



ANAPLASMOSIS 



The early account 



Anaplasmosis is an infectious and transmis- 

 sible disease of cattle that apparently has been 

 in this country for many years. Some have 

 theorized that it was introduced with the first 

 cattle brought by the Spaniards. 



Theobald Smith and Fred L. Kilborne in 

 1893 made first mention of the disease in their 

 report on the cause and transmission of Texas 

 cattle fever. Frequently encountering another 

 entity, they questioned whether they were deal- 

 ing with Texas fever alone or with two dis- 

 tinct diseases. 



In 1910, Arnold Theiler, in South Africa, 

 presented evidence that two diseases were in- 

 volved, piroplasmosis and another which he 

 named, anaplasmosis. K. F. Meyer, in 1913, 

 confirmed observation of anaplasma-like bodies 

 in California cattle. Thereafter, little atten- 

 tion was given to the disease. Most people be- 

 lieved that it would be controlled with the 

 eradication of the fever tick. However, in 

 1921), Dai'lington reported that although ana- 

 plasmosis was a troublesome disease in south- 

 eastern Kansas, he had failed to find fever ticks 

 on infected animals. This was the first indica- 

 tion that eradication of the fever tick might 

 not eliminate anaplasmosis. Much has been 

 learned since then. 



Nature of the agent 



The causative agent of anaplasmosis is Ana- 

 pkisnia marginale, a parasite that destroys the 

 red blood cells of infected animals. Research 

 workers are not in complete agreement as to 

 the nature of the agent. During recent years, 

 a number of investigators have tried to show 

 that it is a filterable virus ; however, their woi-k 

 has been either negative or inconclusive. 



Recently, Espana and coworkers reported 

 that examination by phase contrast and elec- 

 tron microscopy of hemolyzed erythrocytes 

 from infected cattle showed the parasite to be 

 more complex than was generally believed. 

 Ring, match, comet, and dumbbell-like forms 



were observed. They found AnaplaJima mar- 

 (/ivale to be motile, a property not previously 

 described. This may be impoi-tant in cla.ssify- 

 ing the parasite as well as explaining the mech- 

 anism of cell penetration and the typical mar- 

 ginal position. They believe it is justifiable to 

 consider A. marginale a true parasite, prob- 

 ably belonging to the Protozoa. 



Antibiotics and insecticides 



Weapons have not yet been developed for 

 planned eradication or control of the disease 

 and anaplasmosis still costs the cattle indus- 

 try millions of dollars annually. Some prog- 

 ress has been made in combating bovine ana- 

 plasmosis on a herd basis. It was found that 

 several broad-spectrum antibiotics inhibit the 

 organism. Development of the comi)lement- 

 fixation test has given one of the best tools for 

 identification of infected or carrier animals. 

 Encouraging results in stemming transmission 

 of the disease by control of vectors have also 

 been obtained through the systematic use of 

 insecticides on infected herds. 



Anaplasmosis can be treated. But if tetra- 

 cycline antibiotic therapy is to be used bene- 

 ficially, it must be given early in the period 

 when anaplasma bodies are increasing in num- 

 ber. The antibiotic suppresses formation of 

 additional bodies. Blood transfusions are in- 

 dicated during the period of anemia and espe- 

 cially before the crisis is reached in RBC de- 

 -struction. 



Ticks in the west; fh'es in the south 



The anaplasmosis syndrome is similar wher- 

 ever the disease occurs. However, the vectors 

 thought to be chiefly responsible for the trans- 

 mission of the disease in the Southeast are dif- 

 ferent from those in the West. In the Rocky 

 Mountain and West Coast Regions, the natural 

 vectors of primary importance are believed to 

 be the spotted fever tick (Dermacentor ander- 

 s())ii), and the Pacific Coast tick {D. occiden- 

 tiilis) ; biting insects are considered of second- 

 ary importance. In the Southea.st, horseflies 

 and mosquitoes are believed to be the primary 

 vectors. Natural wild animal reservoirs have 

 not been implicated in this region as have deer 

 in California. 



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