typing, and staining of smears and histological 

 sections for evidence of acid-fast organisms. 



Isolations of soil acid-fast organisms are 

 capable of producing allergens which cross- 

 react with mammalian and avian strains. 

 These allergens usually produce low sensitivity 

 when injected intramu.-^cularly. Guinea pigs 

 inoculated intramusculai-ly with soil acid-fast 

 isolates were .still reacting 3'.j to 4 months 

 after inoculation; only avian and mammalian 

 tuberculin were used on the .second test. The 

 greatest reaction was obtained with avian tu- 

 berculin. Field evidence indicated the soil 

 acid-fast produced sensitivity may be of short 

 duration, and the time between exposure and 

 testing will be shortened to less than 2 months 

 in future laboratory trials. 



Microscopic .study of 417 cases of suspected 

 tuberculosis lesions on regular cattle kill was 

 made. Thirty-one percent were positive for 

 acid-fast bacteria, and another 10 percent con- 

 tained atypical acid-fast oi'ganism. Of the 

 remainder, 33 percent were mycotic, parasitic, 

 or neoplastic, and 26 percent were negative. 

 This compares favorably with lesions selected 

 from tuberculosi.s-reactor animals. Out of 160 

 such lesion cases, 23 percent showed typical 

 organisms and 17 percent showed atypical 

 acid-fa.st bacilli. Of other causes, 22 percent 

 were mycotic, parasitic, or neoplastic, and 38 

 percent were completely negative. While in- 

 dicating the general effectiveness of the tuber- 

 culosis control program, these figures reflect 

 the difficulties that will be encountered in the 

 final phase of tuberculosis control. They stress 

 the importance of careful meat inspection and 

 laboratory procedures in detecting tuberculous 

 animals on regular kill, and tracing them back 

 to source herds, which may then be tuberculin- 

 tested. 



Studies were completed on the use of media 

 versus laboratory animals for primary isola- 

 tion of acid-fast oi-ganisms from bovine tis- 

 sues. These studies revealed that certain 

 media are as good as laboratory animals, or 

 possibly better, for the primary isolation of 

 Mycobacterium tubercidosis organisms. This 

 has resulted in a saving of time and laboratory 

 animals. 



Brucellosis. — Correlation of .serological and 

 bacteriological results in reactor herds is in 

 progress. Attempted isolations from 63 vac- 



cinates in 10 herds were positive in 18 (29 

 percent) of the animals, although 4 of the 

 infected vaccinates were in the negative or 

 suspect serological range. In nonvaccinated 

 cattle, isolations were possible in 19 (46 per- 

 cent) of 41 animals in 8 herds, and only 2 

 of these were classed as suspects. In herds 

 containing both vaccinated and nonvaccinated 

 animals, 45 percent of the isolations were from 

 vaccinated cattle, while 5.5 percent were from 

 nonvaccinates. Only 1 of the 15 herds that 

 were shown to contain infected cattle had a 

 negative Brucella Ring Te.st (BKT) hi.story. 



An isolation of a Brucellalike organism 

 was made from tissues submitted by the New 

 Mexico field station from a ram with a history 

 of loss of viability of sperm. Preliminary 

 serological and biochemical studies revealed 

 that the organism has certain characteristics 

 of all three of the Brucella species but is dis- 

 similar to any one in particular. 



Trichinosis. — The cooking of garbage fed 

 to swine was initiated as a measure to control 

 vesicular exanthema; however, other diseases 

 are also reduced by this measure. One of 

 these is trichinosis. To evaluate the incidence 

 of Trichina, 64 lots of 1,896 diaphragms were 

 examined for the isolation of Trichinella 

 i^piralis. Trichina were found in 188 dia- 

 phragms of 21 of these lots. Since diaphragms 

 were submitted only from Northeastern States, 

 the study did not show national distribution. 



Scrapie. — Pathological evidence is used to 

 diagno.se scrapie, as no virological means are 

 available. Diagnosis is based on the history 

 and findings of characteristic vacuoles in the 

 brain. Twenty-seven laboratory confirmations 

 of the disease were made at the Ames Labora- 

 tory from January 1958, to August 4, 1960. 



Studies have been started to evaluate the 

 present methods of histopathological diagnosis. 



DIAGNOSTICIANS AND 

 EPIDEMIOLOGISTS 



Specialized training programs are being 

 utilized to e.stablish teams of diagnosticians 

 and epidemiologists for investigating and 

 studying animal di.sease outbreaks. These 

 groups w'ill function for field investigational 

 work when diseases of unusual nature or pro- 



41 



