Performing Department
School of Food and Agriculture
Non Technical Summary
Farmers often purchase their problems. We see this frequently when new animals are added to a flock or herd without going through a screening process, and without implementation of quarantine and observation. Chronic, insidious diseases (internal parasites, footrot, and a host of bacterial and viral diseases) limit productivity and can become endemic on farms, creating a legacy of loss. As of 2016, New England had over 42,000 sheep, and a growing number of milk and meat goats (USDA NASS Sheep and Goat report, January 2016). Building on past work, we propose to conduct research to improve the health of sheep and goat flocks in Maine. We will continue investigation into improvements in diagnostic tools and their implementation in order to enhance farm biosecurity. We will continue to collaborate with Extension outreach efforts, and will provide workshops and presentations to producers, Extension and other livestock professionals, and veterinarians.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
Farmers often purchase their problems. We see this frequently when new animals are added to a flock or herd without going through a screening process, and without implementation of quarantine and observation. Chronic, insidious diseases (internal parasites, footrot, and a host of bacterial and viral diseases) limit productivity and can become endemic on farms, creating a legacy of loss. As of 2016, New England had over 42,000 sheep, and a growing number of milk and meat goats (USDA NASS Sheep and Goat report, January 2016). Building on past work, we propose to conduct research to improve the health of sheep and goat flocks in Maine. We will continue investigation into improvements in diagnostic tools and their implementation in order to enhance farm biosecurity. We will continue to collaborate with Extension outreach efforts, and will provide workshops and presentations to producers, Extension and other livestock professionals, and veterinarians.An example of a chronic condition with an impact on regional small ruminant production is caseous lymphadenitis (CL). CL is a highly contagious disease affecting sheep, goats, llamas, alpacas and occasionally cattle, horses and people. The bacteria that causes CL (Corynebacterium pseudotuberculosis or C. psTB) infects the lymphatic system, and causing abscesses in lymph nodes or internal organs. Either can detract from the value of the animal, or can cause death. Due to the inapparent nature of the disease early in the infection process, it can "sneak up" on a producer. C. psTB can survive for long durations in the environment, where it can be transmitted easily by contamination of small skin abrasions, such as by use of sheep dips, or by fencing, handling or shearing; internal abscesses of the lungs may be associated with respiratory spread. Once animals are infected with this bacterium they may harbor the bacterium for prolonged periods without abscess formation. While C. psTB is not generally associated with mastitis, CL abscesses in milking goats and sheep may be associated with shedding of the agent into the milk, and antibody detection in bulk tank milk has been reported as a detection method for carriers.Currently, there are vaccines for CL- but they may not be effective, may cause reactions, and also interfere with screening efforts. Optimally, detecting the disease before it gets into a herd, maintaining a disease-free herd by proper pasturing techniques, using disinfection practices effectively, and removing affected animals prior to spread of the disease may prevent or contain the problem. With a SARE-funded project between 2012 and 2016, we tested over 30 Maine small ruminant farms for exposure to CL. In the initial project, an outside lab was used to test sheep for CL. During this phase, 15 Maine farms and approximately 500 sheep were tested. Sheep on all but 3 farms were tested twice; on 2 farms sheep were tested 3 times. Of these 15 farms, 8 (53%) were positive for CL on at least one visit. Six remained seronegative on all repeated visits. After the initial year, we developed the same screening test in our lab, and continue to implement it.The farms fell into 3 patterns: tolerant of some positives, but making an attempt to avoid new cases; positive and not willing to do anything about it (overwhelmed); and either completely or almost negative (and determined to stay that way). The results suggested that for intensively managed flocks, where animals are used for fiber, producers may be aware of CL as a major issue, but are not willing to make the culling decisions required to contain it. In these flocks, vaccination may be needed, if excellent records are kept, frequent boosters are given, and vaccination status is clearly communicated to buyers. Vaccine options in the US are limited at this time to Case Bac (Colorado Serum Company). This vaccine stimulates antibodies to corynebacterial phospholipase D, which is also the target of the SHI test. Other difficulties in these flocks are lack of adequate quarantine facilities and having feeders/fencing that cannot be adequately disinfected, should abscesses occur. Given the persistence of CL in the environment and the expense of replacing infrastructure (wooden feeders/fences) it seems unlikely that complete eradication is possible without ongoing culling in these flocks.In a flock producing a combination of meat lambs and some specialized breeding stock, sheep had been obtained from multiple sites, and were moved into a number of configurations in the year to maximize access to pasture. Thus, mixing of animals was unavoidable in this flock, and follow-up testing was not possible. High seroprevalence was found at the initial (only) blood test. The history was unclear, and may have included vaccination (without current boosters). However, low to intermediate titers in a number of animals, as well as negative titers, suggested that natural exposure to the CL organism was present in this flock. Selling animals for meat would be appropriate, but selling animals for fiber or for breeding from this flock would be inappropriate without disclosure of the CL status.Finding either negative farms (47%; 7 of 15) or farms with very low numbers of positives was encouraging. On two farms, sheep had recently been returned to the home flock after flock sales that did not work out. On one farm, after reintroduction of animals that were offsite at initial testing, a third visit was made to test all sheep. All sheep were still seronegative. On another large farm, a "commercial" flock had been sold, moved offsite, but then returned to the farm after failure of the sale. In this case, the "home" animals, which were breeding/show stock, were initially all seronegative. The returned flock had one seropositive, which was discovered after the flock had already been returned to the farm. On the second test of the "home" flock, one animal had a low titer. Culling and quarantine was advised, and tougher biosecurity for show animals suggested. Both farms produce breeding stock, and much discussion about the critical role of biosecurity ensued. The farmers were encouraged to use CL seronegative status as a selling point for breeding stock.In summary, on several farms, we were able to assist farmers in identifying positive animals and eliminating them, while increasing their biosecurity to prevent any new cases. We produced materials for workshops and presentations to regional sheep producers, and developed a robust test, a version of the synergistic hemolysin inhibition (SHI) test, for low-cost screening of regional small ruminants for CL.We also expanded our efforts to include goat farms, a significant and growing sector of the small ruminant dairy business, and a resource for regional artisanal cheese production. Outreach to these producers has raised awareness of CL, and of the importance of screening herds prior to purchase.Several student projects investigating immune responses to C. psTB in sheep have been conducted in our lab. Current efforts in the lab are focused on identifying potential diagnostic targets in sheep and goat strains of C.psTB, based on reports of potentially immunogenic antigens in animal models.Ultimately, the ability of livestock producers to detect and prevent contagious diseases is dependent on testing, education, and on developing their own farm biosecurity programs. We propose to develop and communicate biosecurity plans to protect small ruminant herds from CL and other potential threats with similar modes of transmission. We will investigate new diagnostic and potential vaccine candidates for CL, and use the platform of CL screening to introduce screening for other common diseases, such as CAE and Johnes disease.a. Objective 1: Identify regional health threats to Northeastern US small ruminants.b. Objective 2: Investigate new and emerging methods for prevention or treatment of these threats.
Project Methods
a. Use surveys and selected disease and parasite screening for Maine's small ruminant farms (Caseouslymphadenitis and intestinal parasites) to evaluate health status and detect emerging threats.b. Develop improved detection and prevention/treatment methods (SHI test implementation andimprovement; bedding/compost/equipment optimization)