APHIS plans actions on cattle fever ticks, screwworms

APHIS plans actions on cattle fever ticks, screwworms
Published on
information-circle This article is more than 3 years old

U.S. Department of Agriculture authorities plan to develop areas in Mexico that are free of cattle fever ticks, and an anti-tick vaccine could be available in the U.S. this fall.

Other USDA officials will prepare for potential screwworm outbreaks in Central and North America, and those preparations could aid eventual efforts to eliminate the worms on Caribbean islands.

Cattle at an APHIS fever tick treatment bath in McAllen, Texas (Photos courtesy of USDA ARS)

The USDA Animal and Plant Health Inspection Service plans to work with foreign entities to keep those pests, certain pests of plants, and invasive species out of the U.S., as the agency describes in a five-year plan published earlier this year.

Cattle fever ticks

Dr. Michael A. Carter, assistant director of APHIS’ Surveillance, Preparedness, and Response Services Cattle Health Center, said APHIS will work with state authorities in Texas to maintain the current cattle fever tick quarantine zone that extends about 500 miles along the U.S.-Mexico border, starting at the Gulf of Mexico, in addition to working toward creating cattle fever tick–free zones in Mexico where cattle would be held prior to export to the U.S.

APHIS officials are working with the USDA Agricultural Research Service on a cattle-use vaccine, and Dr. Carter hopes the vaccine will be available in fall 2015. He also said APHIS was working with the Food and Drug Administration and a private company to make available an antiparasitic-treated molasses that could be distributed to cattle while they are on ranges.

Cattle fever ticks carry protozoa for Babesia bovis and B bigemina. Texas Animal Health Commission information indicates infections can cause fever, anemia, enlargement of the spleen and liver, and, for about 90 percent of susceptible naive cattle, death.

Efforts to eradicate cattle fever ticks from the U.S. started in 1906, and only isolated cases remained in a quarantine zone along the Mexican border by 1943, APHIS information states. The ticks were declared to be eliminated from the U.S. by 1961.

But outbreaks still occur in the 500-mile quarantine zone, and infestations require quarantines of at least six months. An outbreak confirmed in October 2014 near the Gulf of Mexico had extended past the quarantine zone; in response, the quarantine zone was expanded in one border county.


Murali Bandla, associate deputy administrator for APHIS’ International Services program, said APHIS is trying to improve on the screwworm eradication program that already has been “one of the most successful pest eradication programs in the world.”

A screwworm larva

The U.S. and Panamanian governments collaborate on a project of producing and releasing more than 2 billion sterile screwworm fly pupae each year near the border between Panama and Colombia, an effort to maintain a barrier to keep the flies from spreading from South America into Central America. New World screwworms, the larvae of screwworm flies, infect open wounds in warmblooded animals, mostly livestock but also including humans, APHIS information states.

Self-sustaining screwworm populations were eliminated from the U.S. by 1966, and Mexico has been free of them since 1991, APHIS information states. Two dogs infected with screwworm larvae entered the U.S. in 2007 and 2010 from Trinidad and Tobago and from Venezuela, respectively. Veterinary practitioners identified the infections in both cases.

Information from the World Organisation for Animal Health (OIE) indicates screwworm has been eliminated from North America and Central America, Puerto Rico, the Virgin Islands, and Curacao. The flies are still present in South America, particularly in northern countries, and an eradication program in Jamaica failed “due to complex management and technical difficulties.”

Bandla said APHIS plans to develop surveillance and emergency response plans in Central America and Mexico as well as improve the business, energy, and production efficiency of the Panama screwworm-growing facility. That includes developing technology that could double production capacity, improving delivery without adding more production modules, he said.

Screwworms persist in some Caribbean islands, including those that trade with Central American countries, Bandla said. Better understanding of emergency needs and sterile fly production capacities could help APHIS make further plans to eradicate screwworms from the Caribbean, he said.