Texas Department of State Health Services, Zoonosis Control Branch
Texas Oral Rabies Vaccination Program (ORVP) 1995 - 2013
Two rabies epizootics (epidemics in animals) began in Texas in 1988, one involving coyotes and dogs in South Texas and the other in gray foxes in West-Central Texas. The South Texas epizootic had resulted in 2 human deaths and necessitated the administration of thousands of post-exposure rabies treatments. In 1994 the public health threat created by these two expanding epizootics prompted then Governor Ann Richards to declare rabies a state health emergency in Texas. The two epizootics expanded to involve a total of 74 Texas counties (21 South Texas counties and 53 West-Central Texas counties).
In February 1995, the Texas Department of State Health Services (DSHS) initiated the ORVP as a multiyear program with a goal of creating zones of vaccinated coyotes and gray foxes along the leading edges of the epizootics, thereby halting the spread of the virus. The ORVP is a cooperative program involving DSHS; Texas Cooperative Extension Wildlife Services; US Department of Agriculture Wildlife Services; Texas Military Forces; Centers for Disease Control and Prevention; Merial Ltd.; Dynamic Aviation Group, Inc.; U.S. Army Veterinary Laboratory at Ft. Sam Houston, Texas; and other local, state, and federal agencies.
The aerial distribution of vaccine that occurs during each year involves approximately 250 separate flights by five King Air aircraft from the Dynamic Aviation Group, Inc. and annually results in a total flight distance equaling approximately 4 times around the world. Since 1995, the program has been responsible for the distribution of over 44.92 million individual doses of Raboral V RG, an oral rabies vaccine, over approximately 623,800 square miles of Texas.
The use of biomarker was discontinued after 2010. Results from the surveillance program conducted after the 2010 bait drop show 59% (75/126) of coyotes tested in the Gray Fox zone were positive for the biomarker that is indicative of bait acceptance. Of coyotes tested from the primary surveillance area (Coyote zone), 74% (85/114) developed an immune response to the vaccine, while in the secondary surveillance zone (Gray Fox zone) 67% (84/125) developed a titer. Canine rabies cases in South Texas have declined from 122 reported in 1994 (before the first year of the program) and 142 in 1995 to 20 in 1996, 6 in 1997, 5 in 1998, 10 in 1999, 0 in 2000, 1 in 2001, 0 in 2002 and 2003, 1 in 2004, 0 in 2005, 0 in 2006, 0 in 2007, 0 in 2008, 0 in 2009, 0 in 2010, 0 in 2011, 0 in 2012 and 0 so far through 2013. The 2001 and 2004 cases were both in Webb County. The 2012 immune response data (without biomarker correlation) demonstrated South Texas coyotes had 76% (79/103) positive and in West Texas 80% (46/57).
The gray fox program has shown similar success with 244 cases reported in 1995 (before the first program year), 101 in 1996, 24 in 1997, 36 in 1998, 66 in 1999, 58 in 2000, 20 in 2001, 65 in 2002, 61 in 2003, 22 in 2004, 8 in 2005, 45 in 2006, 62 in 2007, 11 in 2008, 2 in 2009, 0 in 2010, 0 in 2011, 0 in 2012, and 1 (bovine) in 2013 to date. Additionally, of foxes tested from the gray fox post-vaccination surveillance program in 2010, 36% (56/155) were bait biomarker positive and 85% (129/151) developed an immune response to the vaccine. The dramatic decrease in biomarker positive results reflects the expanded utilization of coated sachet baits that do not include the biomarker. Gray fox in 2012 West Texas surveillance collections had 93% (114/122) positive.
The Texas ORVP has achieved a level of success that could not have been anticipated during early development work done in 1993 and 1994. The South Texas ORVP has moved to a barrier strategy to prevent reintroduction of the virus. All available resources for the West-Central Texas ORVP will be applied in such a manner as to achieve the most effective and efficient outcome for the control of the rabies epizootic in gray foxes and the protection of the public's health.