Prospects for controlling or eradicating ana- 

 plasmosis are less encouraging in the Western 

 States than in the Southeast since the causative 

 agent can survive longer in the body of a tick 

 than in a i\y or mosquito. It also has been 

 shown that anaplasmosis may be transmitted 

 from one generation of ticks to the next and 

 then into a susceptible bovine host. 



The key to control 



Since the infection is easily spread by me- 

 chanical transfer of infected blood, man, 

 through carelessness in performing blood-let- 

 ting operations, becomes an important poten- 

 tial agent of conveyance. Prevention of nat- 

 ural, mechanical disease transmission is the 

 key to control. This, in turn, is conditioned by 

 four factors: (1) The infectivity level of the 

 blood of carrier cattle; (2) the biting insect 

 vector density population for any given area; 

 (3) the lapse of time between insect feeding 

 on infected and susceptible cattle; and (4) pre- 

 cautions against carelessness in blood-letting 

 operations. Control of any of these factors has 

 an immediate, favorable effect on reducing the 

 disease transmission rate. 



In certain areas of the country, herds have 

 been cleared of the disease by application of the 

 complement-fixation test and segregation or 

 disposal of reactors. If segregation is prac- 

 ticed, carrier or reacting animals should be 

 sufficiently I'emoved from the susceptible group 

 to insure that interrupted vector feedings are 

 not resumed on the susceptible animals. 



These practices have been found feasible in 

 Virginia, and the State is offering a voluntary 

 program to livestock owners. Suspect herds 

 are tested and owners given the choice of re- 

 moving reactors for immediate slaughter or 

 holding them under segregation pending 

 slaughter. A similar project on a limited scale 

 is being offered in Tennessee. No indemnity is 

 paid under the voluntai^j' programs. 



Halting the disease in Hawaii 



Hawaii has had a program since November 

 1955. It was initiated as a pilot project to see 

 if anaplasmosis could be eradicated by use of 

 the complement-fixation test. The essentials of 

 the program are — 



(1) Application of the complement-fixation 



test for the detection of carrier ani- 

 mals. 



(2) Identification and immediate slaughter 



of positive animals. 



(3) Testing of herds (including all cattle 2 



months of age and over) at not less 

 than 60-day intervals until two nega- 

 tive tests are obtained. 



(4) Testing of blood samples collected from 



all cattle slaughtered in the Islands 

 to detect foci of infection. 

 Since anaplasmosis was brought to the Is- 

 lands by importation of carrier animals from 

 the mainland, only animals negative to the com- 

 plement-fixation test are now permitted entry. 

 Cattle must pass two negative tests — one be- 

 fore shipment from the mainland and a second 

 on arrival, before release from quarantine. 

 They are retested 60 days after introduction 

 into a herd. In the absence of a serious vector 

 problem, Hawaii ofl[icials believe that their pro- 

 gram provides a practical means of eradicating 

 anaplasmosis. 



Field trials in Mississippi 



In January 1959, field trial studies were 

 started in the Delta Region of western Missis- 

 sippi. The situation there is different from 

 that in the Hawaiian Islands, in that biting 

 insect populations build up during the warm 

 months from spring to fall. Of the nearly 

 15,000 head of cattle tested in 79 herds in 16 

 counties, slightly more than 60 percent of the 

 animals were classed as reactors or suspects. 

 Individual herd incidence patterns varied from 

 no reactors in a few herds to almost 100-per- 

 cent reactors in several herds. 



Unfortunately, because of lack of funds, it 

 was necessary that owners pay for the collec- 

 tion of blood samples. Hence, herd retests gen- 

 erally were not made at desired intervals dur- 

 ing the nonvector winter months. Neverthe- 

 less, overall results, from the standpoint of 

 reduction of losses from anaplasmosis and new 

 transmission, were encouraging. 



During the summer of 1959, there were 

 fewer losses in herds in which control measures 

 were practiced than there had been the pre- 

 vious year. Some clinical cases appeared in 

 the susceptible segregation groups. But in 



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