Evaluation of a New Strategy for Control of Bovine Tuberculosis in Michigan White-Tailed Deer: Year 1 Progress Report

The State of Michigan is striving to eliminate bovine tuberculosis (Tb) infection among free-ranging white-tailed deer in the northeastern Lower Peninsula of the state. Aggressive reduction in the overall deer population abundance may help to further reduce TB prevalence, but this course of action is unacceptable to many hunters and landowners. Targeted culling of sick deer would likely be far more acceptable to these stakeholders, so in the winter of 2003 the Michigan Department of Natural Resources pilot-trialed a new strategy based on live-trapping and Tb-testing of wild deer. The field study was conducted in a township with relatively high TB prevalence within Deer Management Unit 452 in the northeastern Lower Peninsula. Over a 2-month trapping period, 119 individual deer were live-trapped, blood sampled, fitted with a radio-collar, and released. A total of 31 of these deer were subsequently classified as Tb-suspect by at least one of five blood tests employed (however there was a low level of agreement among tests). A delay in testing meant that only six of these suspect deer were culled by sharpshooters before pre-programmed release of their radio-collars, after which they could no longer be located. Mycobacterium bovis was cultured from one of these six suspect deer; the other five were negative on culture. All target deer were located to within shooting range with 1 – 2 days of effort, and all the radio-collars on the apparently-healthy deer dropped off after the intended 90-day interval, and were thereafter recovered for re-use. There was considerable support for this pilot project among hunters, farmers, state and federal agriculture agencies, the media and the general public, and so we recommend that further field trials be undertaken using this technique. The initial focus of these trials should be on improving the efficacy and reliability of the blood testing procedure.

Bovine Tb Eradication Project – Recognizing Hot Button Issues

The Michigan Departments of Agriculture, Community Health, and Natural Resources, US Department of Agriculture (USDA) and Michigan State University work cooperatively together as the bovine TB eradication project partners. The interagency group combines expertise in epidemiology, veterinary and human medicine, pathology, wildlife biology, animal husbandry, regulatory law and policy and risk communications. The stakeholders, those impacted by the disease, include agriculture and tourism industry representatives, “Mom-and-Pop” businesses, hunters, wildlife enthusiasts, farmers, Local Health Departments and legislators. The regulatory agencies are the above mentioned project partners, excluding MSU and USDA Wildlife Services, both of which offer services to agencies and stakeholders. Eradicating bovine TB would not be difficult if there were no social issues surrounding it. The economy, hunting traditions, animal management, tourism and human health are all impacted by regulatory response to the disease. Often the social issues play a large role in decision making, therefore it is important to understand your clientele and anticipate public reaction to policy changes and requirements.

Taking an Endemically Infected Bovine Tb Area Through to Livestock Clearance. A Case Study of West Taupo, New Zealand

The Pest Management Strategy for Bovine Tuberculosis (Tb) in New Zealand aims to achieve efficient freedom from Tb by 2013 and to eradicate the disease from livestock and wildlife. The West Taupo area, in the central North Island of New Zealand, was chronically infected with Tb in both domestic livestock herds (cattle and deer) and within wildlife populations (brushtail possum, ferret, feral deer and pigs). Through the development and implementation of a technically innovative management plan, this area is now approaching Tb free status. The case study / management plan reported here discusses the operational techniques and strategies that were implemented to achieve Tb clearance in the livestock herds and the possibilities of eradication from wildlife species. It particularly identifies the variations in control strategies that are required as population densities reduce and the challenges of maintaining strong effective control at low densities of some wildlife species, whilst not needing to control other species that were initially clinically diagnosed with Tb control. Use of diagnostic tools and education as an area moves through the cycle towards Tb freedom are as essential as the physical control activities. The use of intensive monitoring of both livestock and wildlife species as trend and performance indicators and the need to educate farmers, hunters and other land use groups become increasingly important.

The Eradication of Bovine Tuberculosis From Infected Wildlife Populations: A New Zealand Scenario

The Animal Health Board (AHB) is the agency responsible for controlling bovine tuberculosis (Tb) in New Zealand. In 2000, the AHB embarked on a strategy designed to reduce the annual period prevalence of Tb infected cattle and farmed deer herds from 1.67% to 0.2% by 2012/13. Under current rules of the Office International des Epizooties (OIE) this would allow New Zealand to claim freedom from Tb. The epidemiology of Tb in New Zealand is largely influenced by wildlife reservoirs of infection and control of Tb vector populations is central to the elimination of Tb from New Zealand’s cattle and deer herds. The AHB has classified New Zealand’s land area into Vector Risk Areas (VRAs) where Tb is established in wildlife (currently 39%) and Vector Free Areas (VFAs) where the disease is not established (61%). Within the VRAs the introduced Australian brushtail possum (Trichosurus vulpecula) is the primary wildlife maintenance host and the main source of infection for domestic cattle and deer herds. Southland is a region of New Zealand with a long history of wildlife associated Tb. Progress in reducing infected herd numbers has been impressive in recent years, primarily due to an intensive possum control program. As a result of this reduction, the focus is now shifting to that of providing increasing levels of confidence that Tb is absent from the remaining susceptible wildlife. High levels of confidence of Tb freedom in wildlife will allow the AHB to reduce the wildlife control programs and ultimately cease control altogether, with minimal risk of Tb reemerging. This paper examines the strategies being utilized to provide that confidence. The types of data, the format in which it is collected and the methods of analysis and review are outlined.

INFLUENCE OF TYPE 2 BOVINE VIRAL DIARRHEA VIRUS NPRO ON ENHANCEMENT OF BOVINE RESPIRATORY SYNCYTIAL VIRUS REPLICATION MEDIATED BY ANTAGONISM OF HOST CELL INTERFERON TYPE I RESPONSES

Bovine viral diarrhea virus (BVDV) is a member of the genus Pestivirus, Family Flaviviridae. The virus can infect many species of animals of the order Artiodactyla. The BVDV genome encodes an auto protease, Npro, that degrades interferon regulatory factor-3 (IRF-3) reducing type I interferon (IFN-I) production from host cells. Bovine respiratory syncytial virus (BRSV) is a member of the genus Pneumovirus, Family Paramyxoviridae. Concurrent infection with BVDV and BRSV causes more severe respiratory and enteric disease than infection with either virus alone. Our hypothesis was that Npro modulates the innate immune responses to BVDV infection and enhances replication of BVDV or BRSV co-infection. The noncytopathic BVDV2 viruses NY93/c N- Npro 18 EGFP (a mutant with modified Npro fused with enhanced green fluorescent protein), NY93 infectious clone (NY93/c), wild-type NY93-BVDV2 (NY93-wt), and BRSV were evaluated in this study. The objectives of this study were: (1) to characterize the replication kinetics and IFN-I induction in Madin-Darby bovine kidney (MDBK) cells following infection with each of the BVDV isolates, and (2) to characterize the influence of BVDV-mediated IFN-I antagonism on enhancement of BRSV replication in bovine turbinate (BT) cells. NY93/c N- Npro 18 EGFP replicated 0.4 – 1.6 TCID50 logs lower than NY93-wt in MDBK cells. NY93/c N- Npro 18 EGFP-infected MDBK cells synthesized IFN-I significantly higher than NY93/c- and NY93-wt-infected MDBK cells. BT cells co-infected with NY93/c N- Npro 18 EGFP/BRSV or NY93-wt/BRSV were evaluated to determine the effects of co-infection on BRSV replication and IFN-I induction in BT cells. BRSV RNA levels in NY93-wt/BRSV co-infected BT cells were 2.49, 2.79, and 2.89 copy number logs significantly greater than in NY93/c N- Npro 18 EGFP/BRSV co-infected BT cells on days 5, 7, and 9 post-infection, respectively. BVDV RNA levels in NY93/c N- Npro 18 EGFP-infected BT cells were 1.64 – 4.38 copy number logs lower than in NY93-wt-infected BT cells. NY93/c N- Npro 18 EGFP single and co-infected BT cells synthesized IFN-I significantly higher than NY93-wt single and co-infected BT cells. In summary, these findings suggest: (1) NY93/c N- Npro 18 EGFP BVDV2 induced higher levels of IFN-I than BVDV2-wt and may be useful as a safer, replicating BVDV vaccine, and (2) Enhancement of BRSV infection by BVDV co-infection is mediated by antagonism of IFN-I.

BLOOD AND TISSUE IDENTIFICATION OF SELECTED BIRDS AND MAMMALS, PART II: Cross Reaction Patterns of Birds and Mammals, Using Deer, Bovine, Raccoon, Chicken and Mallard Duck Antiserum, part 5

Part 5 (pp. 114-117) References Appendix