74 ANNUAL llKl'OKTS OF I »K1*AU'JMI:NT OF AGRICULTUUK. 1937 
a loss of ulMiiit $10.0(M).(MMi ill Texas. It is l>cli<'\ ed that noriiially the annual 
infestation in Texas is ahcjut 1,(XH),(XX> cases, and that the weather during; 1930 
was somewhat more favorahle for serewworms than during a normal year. 
There were no extensive droughts and there seemed to be sufficient rainfall to 
keep wounds soft and attractive for screwworm flies, but not enough to result 
in drowning of immature stages in the soil. The cases in 1930 <K-curred at the 
average rate of S2T among l<i(),(KK> animals, and were estimated at 573.390 on 
the basis of 12r»,i:j4 reported infestations. It seems conservative to attribute 
the difference between this estimate and that of a normal infestation to results 
of screwworm control work. In addition to a reduction in the number of cases, 
there was also a reduction in the mortality among infested animals. During 
393.') the deaili rate was estimated at 14,732 among 100,(X>i> animals, and in 1930 
the mortalities were at an average rate of 9,410 among KKJ.OOO infested aitimals. 
They are still high enough to emphasize the need for adopting better methods 
of treating animals, and especially is this true for ca.ses occurring in sheep 
and goats. 
In other Southwestern States control work started during June and some 
educational phases were continued through the winter months. From June to 
December, inclusive, the following were the average rates of infi'sTations among 
10(),0(K) animals: Arizona 202, California 75, New Mexico 101, and Oklahoma 212. 
The infestations in all of these States were at the rate of only a fra<-tion of 
1 iK'rcent of the animal population. There was a wide variation in the mor- 
tality rates because in areas having a low incidence of cases there is a mori' 
tixed tendency of stockmen to use undiluted stoi k dips or other irritating mate- 
rials for killing screwworms in wounds. The average rates of animals dyinir 
among 100,000 infested animals were as follows: Arizona 2,722. California 1,070. 
New Mexico 3,107. and Oklahoma none. 
During the period when there was a good degree of contrt>l of screwworms 
in Texas and other Southwestern States, the pest was able to spread and cause 
at least 1,025 cases in Oklahoma, about 50 in Kansas, 25 in ^lissouri. about 100 
in Illinois, and approximately 1.000 in southwestern Tennessee. The.se tigures 
represent cases occurring during a dry year, in many of these areas, and a re- 
duction from reports of the previous year, when there were about 30.(^>t) cases 
in Kansas. 1.000 in Iowa, and 6,000 in Illinois. During 1930 workers in stock- 
yards at different places examined animals and .sent in si}ecimer.s for identifica- 
tion. The following collections of primary screwworms were made: At Kansas 
City, Mo., 10; at East St. Louis. III., 39: at Kaplan and Church Point, La.. 3: 
at New Orleans. La.. 10 (of 59 cases) : and at Nashville. Tenn.. 1. These records 
.show that there is an annual danger of introducing screwworms into uninfestetl 
States. 
PREVENTION AND SHEARING 
In the sheep- and goat-breeding area of southwestern Texas .screw w<u'ms are 
normally present when the .spring shearing begins, and they are able to spread 
rapidly across the area during the period required for .shearing operations. In 
the spring of 1937 supervisors were assigned to several counties so that they 
could work among owners of sheep, advising them of the importance of treat- 
ing shear cut.s. The owners were visit(Ml in advance of shearing, and screw- 
worm control workers urged that all sliear cuts be treated with pine tar oil 
to prevent infestation, and that juiimals liaving severe injuries be kejit in hold- 
ing i)astun^s and treated until healed. Tliis j^rocedun^ did not prev(>nt spread 
of the screwworms across the sheej)- and goat-breeding area but it was most 
helpful in maintaining a low screwworm ])oi)ulat ion. From June 2<"> to Divem- 
ber 31, 19.30, the average^ inf(>stntion in the sheep- and goat-breixling area was 
at the rate of 882 cases among 1(X>.000 animals. Following .spix'ial work in this 
area the average infestation in Texas for June 1937 was oidy 341 cases among 
100.000 aninials. Injuries of .sheep, such as sore mouth, pinkeye, boils, iirickly- 
l>ear injuries, and tliose caused by rams' fighting, are not easily avoided, but 
many animals escap(>d infestation because screwworms wtue at a low level. 
In the southeastern counties of New M<'xico the treatment of sliear cuts reduce<! 
screwworm infestations, but in (>uay Cotinty. where no siMH-ial work was done, 
an infestation of a]»ouf 2 percent of the animal population develoiH'd in the latter 
l»art of Jinie. 
SUMMARY 
The sc-rewworm control work of the year resulted in (11 rcMlucing infestations 
and death los.ses amojig livestock in Texas and other Southwestern States and 
further redueing cases nufl mortalities in the Southe.Mstern States: (2) effec- 
tively ]>reventlng the building up of large numbers of screwworms in different 
