Cattle Fever Ticks

by Hallie Hasel, DVM

Cattle fever ticks, known, also, as Rhipicephalus (Boophilus) annulatus and R. (B.) microplus, are the most dangerous cattle ectoparasites in the United States. These ticks have been a threat to American agriculture for generations as they are capable of transmitting the protozoa, or microscopic parasite, Babesia bovis or B. bigemina, the causative agent of Babesiosis or cattle fever. Fever ticks were introduced by the Spanish colonists and are a one host tick, meaning they develop through three life stages while on their single host, preferably cattle. Estimates from 2010 indicate costs of $1.2 billion in year one of an outbreak of fever ticks within their historic range along the southern border of the United States.

For more than 100 years, the Texas Animal Health Commission (TAHC) and the United States Department of Agriculture (USDA) have fought to eradicate the cattle fever tick back to Mexico, where the tick and babesiosis are endemic. Babesiosis is fatal in up to 90 percent of cattle with no immunity because the protozoan attacks and destroys the animals’ red blood cells, causing acute anemia, high fever, and enlargement of the spleen and liver. Since there is no vaccine or established treatment for animals infected with Babesia, the fever tick program is designed to eliminate the tick from the Texas environment.

In 1943, the Permanent Quarantine Zone (PQZ) was established along the southern border of Texas, from Del Rio to Brownsville, spanning over 500 miles. Employees of the USDA Cattle Fever Tick Eradication Program (CFTEP) patrol the PQZ, performing river range inspections, controlling livestock movement, scratching/dipping livestock, apprehending stray animals, and performing systematic treatment of animals on infested premises. During a fever tick outbreak, analysis estimates that a representative 500 cow-calf ranch in Texas would incur costs following a nine month dipping protocol of $250 per cow, experience a 47-percent increase in cash expenses and an 80-percent decline in net cash farm income.

The potential hosts for cattle fever ticks include, but are not limited to, cattle, horses, white-tailed deer, and exotic hoofstock, such as nilgai antelope and red deer. Movement restrictions of infested and exposed hosts and routine surveillance are critical to stopping the spread of the ticks to new areas. When infested hosts are found on a premises, a quarantine is issued for both the premises and the livestock. Quarantines require systematic treatment of infested and exposed livestock and wildlife hosts, which results in the removal of ticks not only from the animals, but ultimately the environment. Surveillance allows both USDA and TAHC to monitor the effectiveness of eradication efforts.

Unlike most other livestock diseases, a fever tick quarantine includes not only the infested and exposed animals, but the premises where these animals are or were located and the surrounding premises. This is a result of the fever tick’s cycle and that female ticks can lay up to 4,000 eggs in the environment, which may lay dormant for up to nine months before larvae hatch and find a new host.

Many factors have changed since the original eradication of fever ticks in the 1940s, which complicate eradication efforts today. These factors include increased population densities of wildlife capable of sustaining and perpetuating cattle fever ticks, limited or no cattle fever tick treatment modalities for some of these wildlife species, and shifting land use resulting in decreased numbers of cattle that can undergo systematic inspection and treatment.

Failure to contain and eradicate current cattle fever tick outbreaks could have a potentially devastating impact on the Texas cattle industry, which contributes more than $10 billion annually to the state’s economy. Texas A&M University’s Agricultural Food and Policy Center 2010 Economic Impact of Expanded Fever Tick Range estimates that three non-contiguous fever tick outbreaks would cost $123 million in the first year. Annual costs after the first year are estimated to total $97 million per year.

There are currently approximately 2,400 premises under some level of fever tick quarantine statewide, with eight counties (Cameron, Kleberg, Live Oak, Maverick, Starr, Webb, Willacy and Zapata) having active fever tick infestations.

For more information regarding the fever tick program and current infestations, please visit www.tahc.texas.gov/animal_health/cattle/#ticks, or contact the USDA CFTEP Laredo Office at 956.726.2228.