NCBA Cattle Herd Security/BVD Working Group
HoBi viruses and trichomoniasis take center stage in working group session.
SAN DIEGO, Calif. (Jan. 28, 2016) — A full agenda faced National Cattlemen’s Beef Association (NCBA) members attending the Cattle Herd Security/BVD Working Group meeting during the 2016 Cattle Industry Convention in San Diego, Calif. Cattlemen in attendance heard presentations addressing an emerging disease, HoBi-like viruses, and an old foe, trichomoniasis.
Unable to attend in person, USDA-ARS National Animal Disease Control Center microbiologist Julia Ridpath provided background on the so-called HoBi-like viruses via telephone. Ridpath said scientists are tracking new pestivirus species that are related to those responsible for bovine viral diarrhea (BVD). Originally found in South America, HoBi-like viruses have since been associated with disease outbreaks in Southeast Asia and more recently in Europe. Signs of infection include slowed growth, reduced milk production, higher rates of reproductive and respiratory diseases, and a higher incidence of death among young animals.
“If HoBi gets to the U.S., problems could be greater than BVD currently causes. Studies suggest a high level of susceptibility among livestock in the U.S.,” said Ridpath, explaining that U.S. researchers are engaged in international collaborative studies, including potential development of preventive vaccines.
Trichomoniasis update
Four guest speakers addressed trichomoniasis, a venereal disease causing abortions and infertility among infected cattle. Leading off, University of Nebraska clinical veterinarian Jeff Ondrack provided an overview of “trich,” the causative protozoan organism (Tritrichomonas foetus) and the disease’s impact. Ondrack said reproductive losses in infected herds can run as high as 50%. Most cows clear the infection within a few months, but some become carriers and remain capable of infecting bulls. Once infected, bulls carry the disease for life.
Ondrack said state trich control programs rely heavily on testing of bulls, by collecting samples of smegma from the epithelial folds of a bull’s penis and prepuce. Samples are sent to a laboratory for analysis. Results are then returned to the veterinarian responsible for testing.
Control programs have sometimes been hampered by testing errors, and laboratories are often blamed. However, according to Ondrack, 90% of errors occur during the “pre-analytical phase” of the testing process. In other words, most errors are the result of mistakes made during collection or handling of samples prior to the time they reach a laboratory.
The timing of sample collection matters. Ondrack said studies suggest optimum results may be achieved when samples are collected after bulls have experienced at least 17 days of sexual rest. Sample collection technique is a contributing factor, so Ondrack advises veterinarians to become proficient with their preferred implement for smegma collection. He also advised careful introduction to an appropriate media prior to shipment and avoidance of heat or cold extremes prior to and during shipping.
Veterinarian Kris Clothier of the California Animal Health and Food Safety Laboratory explained the technical aspects of sample analysis, a process involving multiple steps. She echoed Ondrack’s call for care during sample collection and preparation for shipment to a lab.
“We’ve got to have a quality sample in the first place,” stated Clothier.
John Davidson, a professional services veterinarian with Boehringer Ingelheim Vetmedica Inc., said producers and their consulting veterinarians must have a plan of response to positive test results. He advised producers to “update their trich IQ,” be aware of the local risk of infection and work closely with their veterinarian. Davidson stressed the importance of pre-purchase testing of bulls and, in some cases, annual prebreeding season testing. For herds that have been infected, testing bulls after the breeding season may be advisable.
“Recordkeeping is important,” Davidson added. “If you have trich in the herd, you need to know which cows were exposed to infected bulls.”
Regarding use of trich vaccine, Davidson recommended familiarity with vaccine limitations. Two doses are required, and vaccination is no guarantee against infection. However, it can help when used as part of a management plan.
Speaking about the regulatory side of trich control was Dee Ellis, retired state veterinarian for Texas. Citing his own state’s program as an example, Ellis emphasized that a control program won’t work unless it is industry driven. He said programs usually start with mandatory testing requirements for bulls entering the state, followed by intrastate requirements. The logical progression, said Ellis, is to progress from a control program to an eradication program.
“We focused on the pre-analytical phase (of testing), emphasizing veterinarian training, use of ‘official’ labs and setting a limit for sample shipping time,” said Ellis.
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