ANNUAL REPORT, 1947-48 75 



(Dukes) during 1947. Both infectious bronchitis and Newcastle disease are 

 very prevalent in Massachusetts and represent a serious economic menace to the 

 industry. 



During 1947 a Newcastle disease immunization project was initiated. A 

 preliminary^ report of the results has been published as Contribution Number 

 645, Massachusetts Agricultural Experiment Station. The encouraging results 

 have permitted the development of a State-wide flock vaccination program on 

 an investigational basis. 



During the past year the viability of Newcastle virus in infertile eggs held at 

 incubator temperature (99° F.) and humidity (wet-bulb reading 90° F.) has been 

 investigated. Preliminary results reveal that the virus may remain viable under 

 those environmental conditions for at least 29 days. 



The resistance of the virus to formaldehyde fumigation was also investigated. 

 Preliminary results reveal that whole egg shells with only one end broken and 

 the outer surface contaminated with Newcastle virus require at least one hour 

 of triple strength fumigation (105cc. formalin and 523^ grams potassium per- 

 manganate per 100 cubic feet of space, at a temperature of 99° F. and a wet-bulb 

 thermometer reading of 86°) to destroy the virus. However, when egg shells 

 were finely crushed and contaminated with virus, one-hour fumigation was in- 

 sufficient to kill the virus. 



These investigations on the behavior of the virus under various physical, 

 chemical, and thermal influences are being continued. 



Mastitis Testing Laboratory. (W. K. Harris.) Laboratory examination of 

 milk samples for the diagnosis of bovine mastitis was first reported by the labora- 

 tory on samples received March 24, 1947. Following the examination of samples, 

 group segregation of the cows is recommended according to the results of the 

 test. The group numbers shown on the report of test and their significance are 

 as follows: 



Group I — Negative. 



Group n — Positive for mastitis not due to Str. agalacliae. Such cases are most 

 commonly due to infection with Staphylococci, Str. uteris, Str. dysgalactiae, or 

 coliform organisms. This group includes cows having non-infectious mastitis. 



Group HI — Positive for Str. agalactiae. 



During the period from March 24 to June 30, 1947, inclusive, 4,607 samples 

 from 1,166 head in 21 State-owned herds were tested. Of these, 691 cows were 

 placed in Group I, 236 in Group H, and 239 in Group HL No tests on private 

 herds were completed during the period. During the fiscal year of 1947-48 a 

 total of 13,645 milk samples was tested. There were 102 samples submitted 

 that were unsuitable for testing. From cows in State-owned herds 9,113 samples, 

 and from private herds 4,532 samples were examined. The above figures in- 

 clude both partial and complete herd retests. 



In order to determine the incidence of mastitis in the private herds tested, a 

 summary of the initial tests was made. Initial tests were made on samples from 

 1,157 head, representing 75 herds, of which 56 had less than 20 cows each and 

 19 had 20 cows or more. The percentage of cows found infected is shown as fol- 

 lows :- 



Herds Head 



Under 20 cows 56 465 



20 cows or more 19 692 



Combined 75 1,157 



