were found in both the smear and digest slides. 

 Because of this factor, the total number of 

 positives recorded with both methods is great- 

 er than with either method separately. This is 

 shown in the last two columns, giving the num- 

 ber and percent of positive livers for both 

 methods combined. 



Out of a total number of 1,234 fish livers 

 examined, 41 or 3.3 percent were positive by 

 the smear method and 56 or 4.5 percent were 

 found positive by the digest-concentrate tech- 

 nique. This was a 36.4 percent increase in 

 positive of the latter method over the first. Of 

 greater significance, however, was the combina- 

 tion of both methods with a total of 77 positives 

 or 6.2 percent of the number examined. This 

 is an increase of 87.9 percent over the smear 

 method, and a 37.8 percent increase over the 

 digest-concentrate procedure. 



The smear slides, rated 1-5 with a com- 

 pletely arbitrary rating, could not be expected 

 to have a high correlation with the digest- 

 concentrate slides rated A-E which gives a 

 reasonably accurate bacterial density count per 

 gram . It can be noted, however, that within 

 limits of very high or very low bacterial count 

 there is a moderate degree of correlation. Part 

 of the cause for this low correlation of bacterial 

 count between the two systems lies in the char- 

 acteristic of the acid-fast bacteria to group in 

 nodules. If one nodule was selected when doing 

 a smear slide it might appear that the liver was 

 heavily infected and a rating of No . 5 would be 

 given; however, this same liver might be rated 

 as No. 1 or even negative if another part of the 

 liver was examined. 



Some of the hatcheries studied gave a 

 reversal in expected trend of larger percentage 

 of positives with the digest method. With 



Elokomin silvers, this was especially true . It 

 might be postulated that there are different 

 species, strains, or even cycles of acid-fast 

 bacilli infecting these fish and some of the types 

 will not withstand the rigorous physical treat- 

 ment of the digest -concentrate technique. 



Positive smears rated 1-5 after 5 minute exam- 

 inations are as follows: 



No. 1 Only 1-20 bacilli in entire preparation. 



No. 2 In excess of 20 in entire preparation 

 to less than 1/field. 



No. 3 About 1/field to 25/field. 



No. 4 About 25/field to 100/field. 



No. 5 In excess of 100/field. 



Positive digests rated A-E after examination of 

 1 sq. mm. of prepared area are as follows: 



A. 1-10 bacilli/sq. mm. = 1-10 million/gram 



of liver . 



B. 10-100/sq. mm. = 10-100 million/gram of 



liver . 



C. 100-1, 000/sq. mm. = 100 million -1 billion/ 



gram of liver . 



D. 1,000- 10,000/sq. mm. = 1 billion/gram of 



liver. 



E. 10,000-infinity/sq. mm. = 10 billion -infinity/ 



gram of Liver . 



16 



