
Chemical Analyses 
During fiscal year 1972, the Chemical Section of the Veterinary Services Diagnostic 
Laboratory at Beltsville actively supported field activities and, in addition to tissue residue work, 
performed quantitative analyses on the following samples:' 
Toxaphene - 9,330 (Field Samples) Delnav - 354 Dursban - 9 
Toxaphene - 920 (Emulsion Concentrate) Imidan - 114 Ronnel - 6 
Co-Ral - 996 Ciodrin - 15 Arsenic - 3 
In addition, chemicals for 11,880 arsenical field tests and 140 lime-sulfur tests were prepared, 
standardized, packaged, and mailed to the field. Emulsion stability tests were run on seven 
toxaphene concentrates. 
Active Program Continues in Texas 
Because the territory in Mexico along the lower Rio Grande River is tick-infested, ticks carried 
by Mexican animals illegally entering the United States, reinfest Texas regularly. The River, as the 
international boundary, is not an effective barrier against such illegal movements (see table 2). 
The systematic eradication area, under Federal and State quarantine, extends from Del Rio, 
Tex., to the Gulf of Mexico, approximately 500 miles. This zone is patrolled by Veterinary Services 
inspectors who, in cooperation with the Texas Animal Health Commission, work to reduce the 
introduction and prevent the dissemination of the ticks. The areas under quarantine in Texas 
include parts of Cameron, Hidalgo, Kinney, Maverick, Starr, Val Verde, Webb, and Zapata Counties. 
Of the 51 tick-infested herds in the systematic aréa, 22 were found by apprehension and 
inspection of stray livestock; 11 at dipping and/or inspection prior to movement; three through 
14-day or other routine inspections; two as a result of mingling of livestock; six by pasture 
inspection; four by chute inspection; and three by pen inspection. 
Of these 51 infestations, 22 resulted from tick-infested livestock straying from Mexico and one 
from intermingling of livestock. It was not possible to identify the source of 28 infestations. 
Of the 10 infested herds found in the final area (outside the area under Federal quarantine), 
three were found on pasture inspection; one on 14-day or other routine inspection; four on dipping 
or inspection prior to movement; one by tracing from infected or exposed premises; and one on 
continual surveillance of premises released from quarantine. The source of the 10 infestations in the 
final area was not determined. 
There were 1,173 lots of ticks submitted to the Parasitology Section of the Veterinary 
Services Diagnostic Laboratory for identification; 6 skin scrapings and 369 lots of screwworm 
larvae were also submitted by the tick force. Of the ticks submitted, 115 were B. microplus. 
'Trade names are used in this publication solely for the purpose of providing specific information. Mention of a trade name 
does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture. 
