Economics of BluetongueWritten by John Ritten
A study by recent UW graduate student Tris Munsick, with Drs. Dannele Peck in the Department of Agricultural and Applied Economics, Myrna Miller in the Veterinary Sciences Department and myself calculates the cost of bluetongue outbreaks on Wyoming sheep operations. The analysis is covers flock sizes from 256 to 1,440 ewes, with varying severities of potential outbreaks and timing of recurrences over a suite of prices. The results should be of interest to most sheep producers across the state.
The costs of an outbreak are manifested in a variety of ways, including the costs of caring for sick ewes – both the labor and feed costs associated with tube-feeding, drug costs and the loss of revenues due to both death loss and lower lamb weights due to delayed breeding.
Estimating the impacts of an outbreak can be challenging, as not all flocks respond similarly.
For example, we would expect flocks in the eastern part of the state to have lower costs as compared to flocks in the western part of state, mainly because outbreaks occur more commonly in the east and, therefore, flocks will likely have some form of existing immunity. When naïve populations are infected, we expect the impacts to be more dramatic and, therefore, more costly. To account for this variability, the costs were estimated over a suite of morbidity, or sickness, rates, and mortality, or death loss, rates, as well as lamb and ewe prices.
For brevity, I will only report the results from a hypothetical 640 flock. For an “average” outbreak with 21 percent morbidity, 12 percent mortality and lamb prices at the 20-year average, the total cost of a single bluetongue outbreak would be over $36,000. This represents a case in that just over one in five ewes is actually infected, and just over one in 10 dies. In the “worst-case” scenario, with 36 percent morbidity, 20 percent mortality and lamb prices at the peak of observed prices over the last 20 years, the total cost exceeds $72,000 for a single outbreak. In this case, over one-third of the flock is infected and one in five ewes dies.
The costs of an outbreak are obviously fairly high.
The study goes on to calculate the cost of vaccinating against bluetongue. I’ll report the costs associated with using a killed virus vaccine, which can be special-ordered to match the serotype in your region. If you are interested, talk to your vet or the Wyoming State Veterinarian. The assumptions regarding vaccination used in the study assume two doses are required at a cost of $1.20 per dose and that the vaccine is administered when animals are already being handled to minimize additional labor costs. While the vaccines are safe to use any time of the year, the study assumes vaccinations are done prior to summer grazing by June 1, so the flock is protected when returning to lower elevations in the late summer or early fall, when infection is most likely.
The study calculates the costs associated with various vaccination strategies, but given the fact that some protection remains for a period of two years, I will present the results from a strategy that vaccinates the entire flock every two years, and only lambs will need to be vaccinated in the other years. The annual cost associated with this strategy for a flock consisting of 640 ewes is $2,731 per year. This seems very cheap compared to the cost of an outbreak. However, this cost must be incurred every year, while outbreaks tend to occur less frequently. However, if an “average” outbreak occurs every five years, this strategy realizes a net benefit of almost $5,000 per year, even in years between outbreaks. Even if an average outbreak occurs only every 20 years, this strategy still has a net benefit of over $2,000 per year.
Results also show that the greatest cost factor associated with an outbreak is the mortality rate. Keeping ewes alive should greatly reduce the cost of the outbreak as it keeps breeding stock in the flock, reducing the need to buy or retain replacements.
The second biggest factor in terms of outbreak cost is lamb prices. Results suggest that vaccinating in years of high prices is a better investment than in years with low prices. However, we rarely know in advance exactly what prices will be in the fall, so I would recommend vaccination regardless of the price forecast.
Morbidity rate is the third most important factor, however the impact is only a third as large as mortality rate.
When making decisions regarding vaccinations, it is also important to understand the impact of location on the benefits of vaccination. In areas where bluetongue is more rare, we would expect higher morbidity and mortality rates as the flock has had less exposure, and therefore less existing immunity, to an outbreak. Areas that experience more frequent outbreaks tend to have lower morbidity and mortality, therefore the consequences of infection are less severe.
For example, if an area experiences a severe outbreak every 10 years, with 36 percent morbidity and 20 percent mortality, and assuming 20-year average lamb prices, the annual benefit to vaccination exceeds $6,000.
However, if a location experiences an mild outbreak every five years with only a nine percent morbidity rate and a six percent mortality rate, the annual net benefit of vaccination is only a little over $900 per year. In this case, even though outbreaks happen more frequently, the fact that they are less severe results in lower benefits of vaccination.
It’s important to consider a lot of factors when determining the larger benefit we see from vaccination. The more severe an outbreak is, the benefits of vaccination are larger. The more frequent an outbreak is, the larger the benefits of vaccination are, although only for outbreaks of equal severity.
Often, as outbreaks become more frequent, severity tends to decrease, decreasing the benefits of vaccination. The benefits of vaccination are also larger if an outbreak occurs in years of high prices. Further, there will likely be a lot of stress and emotional costs associated with an outbreak that are not included in these results.
Care and cleaning of syringes and needles important for quality assuranceWritten by Heather Smith Thomas
Beef Quality Assurance (BQA) guidelines stress the use of clean syringes and needles for any type of injection to minimize the risk of contamination or infection at the injection site.
Sterile, disposable syringes and needles that are used just once, on only one animal, are the safest, but most producers are processing multiple animals at once and utilize multi-dose syringes.
If care is taken when filling syringes, using a sterile needle each time to draw the product from the bottle, and if the needles on the syringes are changed each time they are refill, contamination is kept to a minimum.
It is also important to properly clean syringes after use.
Rachel Endecott, Extension beef cattle specialist at Montana State University in Bozeman, Mont., says that when producers finish giving injections, the sooner they can rinse out the syringes, the better.
“It will be easier to get everything out. Don’t leave syringes on the counter for a week or until next year and then try to clean them. The sooner we can get them clean, the better – even if it’s just a quick rinse and then a more thorough cleaning later that day when we have more time,” she says, adding, “Leaving residue in there to dry and solidify makes it more challenging when we try to clean it.”
In years past, with the old, glass syringes, people just took them apart to boil all the pieces, and this still works, she adds.
“I think the newer syringes with nylon/plastic barrels are also durable enough to withstand boiling water,” says Endecott.
The important thing is to not use any soaps or disinfectants because any residue from those can inactivate modified live vaccines.
“Instead, producers should use very hot water. My tip for cleaning syringes is to clean it until we think it’s clean and then do it one more time – like that last rinse when washing dirty clothes,” says Endecott.
Nora Schrag, DVM and assistant clinical professor at Kansas State College of Veterinary Medicine, says the multi-dose syringe guns are a little difficult to clean, but they always need to be cleaned.
“A good rule of thumb is to clean them with regular soap and hot water on the outside and hot water on the inside. If a producer has used a vaccine that’s very thick, take the syringe apart completely and clean it with soap and water, and then rinse thoroughly with clean water,” says Schrag.
Using distilled water to clean syringes is also important.
“Many people have hard water with minerals in it, and modified live virus (MLV) vaccines are very sensitive to mineral deposits and disinfectants,” she explains. “The minerals in hard water will mix with the components of the vaccine sometimes and cause some problems.”
She adds, “Never clean a syringe with disinfectant and then use it for a MLV vaccine, or the vaccine will be deactivated.”
“The final step is to boil some distilled water or heat it in a microwave for two minutes to get it boiling. Put the recently cleaned syringe back together. Then, suck up the boiling water and blow it out the end of the syringe three times. After we’ve done that, the syringe is not perfectly sterile, but it is very clean and safe to use to vaccinate cattle,” she explains.
“After the syringes are thoroughly rinsed with boiling water, we put them in Ziploc bags to store in a cabinet, so they won’t get dusty. Don’t tighten the Ziploc or it will seal dampness inside,” Shrag says.
Bags should be left open for the syringe to dry, and then they can be sealed.
“Then we can put that syringe in our treatment box, or wherever we will be using or storing it until the next use. When we pull it out, it’s clean and ready to go,” she says.
Sometimes after many uses, the plungers need some lubrication.
“We’ve gone away from using mineral oil for lubrication because mineral oil tends to break down the O-rings over time,” says Endecott. “Glycerin or vegetable oil are the most recommended lubricants these days.”
Heather Smith Thomas is a correspondent for the Wyoming Livestock Roundup. Send comments on this article to firstname.lastname@example.org.
Research looks at economic impact of vaccinating for bluetongueWritten by Saige Albert
Riverton – When bluetongue hit in the Big Horn Basin in 2007, it had severe impacts on sheep producers.
“Our research looks at deciding if vaccinating for bluetongue virus in domestic sheep flocks in Wyoming is a viable option for the future,” said University of Wyoming graduate student Tris Munsick at Fremont County Farm and Ranch Days on Feb. 10. “Currently, we don’t vaccinate. We looked at the economic impacts of vaccinating, and examined the costs and benefits of vaccinating in the regions affected by bluetongue.”
Munsick partnered with producer Randall Jones of Otto to investigate the question, and his research is guided by UW Professors Dannele Peck and John Ritten in agricultural and applied economics and Myrna Miller in veterinary sciences.
The 2007 outbreak in the Big Horn Basin was devastating for producers.
“The Big Horn Basin has no history of bluetongue before, and producers like Randall Jones who got the disease in their herds were nearly devastated by it,” he commented.
Jones explained that the outbreak started in his herd at the end of September.
“I’ll remember that outbreak for my entire life,” Jones said. “I had no idea what bluetongue was prior to getting it. The first thing I noticed was a lamb that acted like it had something in its mouth. Its tongue was swollen.”
He continued, “Two days later, I cut over 100 head from the main herd that were showing symptoms.”
Because the disease is viral, Jones said supportive care was his only option. He fed hay and intubated the affected sheep to provide sustenance in the form of a gruel. They also gave the sheep a painkiller to attempt to influence them to eat.
“It took about 10 days before they died,” he said. “It was miserable and hard to watch.”
“Over the course of six weeks, we lost one in every six of our sheep,” Jones said. “It didn’t matter whether we were talking about the stoutest rams or the skinniest ewes.”
Jones also noted that the infections continued until late October when a hard freeze killed the midges.
During the 2007 outbreak, Jones mentioned vaccine wasn’t available at the time.
“The only place we could find vaccine was from the California Wool Growers, but federal laws prohibited it from coming across state lines,” he explained.
Current work to develop a vaccine is being conducted by Miller in the Wyoming State Vet Lab.
Jones added that insecticide is also useful for controlling midges, but using an insecticide dip is both time consuming and labor intensive. Insecticide must be re-applied every three weeks.
“We have to cover every area that the skin does not have wool with insecticide,” he said. “I’m convinced it will have an impact on controlling the midge, thus controlling the transmission of bluetongue, but I prefer vaccine.”
“Working with Randall and Dr. Jim Logan has been great,” Munsick said. “We looked at the economics of vaccinating based on the 2007 bluetongue outbreak.”
Munsick looked at Jones’ herd of 1,400 sheep, 500 of which were affected. Of the affected sheep, 275 died, for a mortality rate of nearly 20 percent.
Using four methods and four scenarios, Munsick looked at the economic impacts of vaccinating
“There are four scenarios that can happen with a bluetongue outbreak,” he said. “We can not vaccinate and not get the disease, not vaccinate and get the disease, vaccinate and not get the disease or vaccinate and get the disease.”
Additionally, in his research, Munsick looked at the worst-case scenario, assuming naïve sheep populations, 100 percent certainty of disease contraction and 84 percent efficacy of the vaccine.
Munsick also used a herd of 1,400 sheep for his calculations, reflecting Jones’ herd from 2007.
In the worse case scenario, Munsick totaled the cost of an outbreak at over $72,000. Costs included supportive care, pharmaceuticals, death loss, sickness and labor costs.
“These costs don’t count for intangible costs,” he said. “This number is also variable depending on lamb prices and feed costs. We used prices for 60- to 90-pound feeder lambs in Fort Collins, Colo. from November 2014.”
When looking at vaccines, Munsick considered both modified live virus (MLV) vaccine, at a cost of 32 cents per dose, and killed virus vaccine, at $1.20 per dose.
Total MLV vaccine cost would reach $497.51 for the herd, and killed vaccine cost would be $3,499.93.
“We looked at breakeven costs,” Munsick explained. “How much would the outbreak have to cost to justify vaccinating every other year?”
He continued, “If the outbreak hits every five years, an outbreak would need to cost $1,478.92 if we use MLV or $10,403.89 if we use killed vaccines. If an outbreak hits every 10 years, it would need to cost $3,553.18 for MLV and $24,995 if we used killed vaccines.”
Munsick added that the maximum time between outbreaks to justify the use of MLV vaccine and killed vaccine is 48 and 18 years, respectively.
“If we see outbreaks less than every 48 years, we can justify the cost of MLV vaccine, and we if we an outbreak less than every 18 years, we can justify the cost of killed vaccines,” Munsick commented.
Munsick’s research will be finalized within the next four months. The Wyoming Agriculture Producer Research Grant Program, UW Ag Experiment Station and two private UW College of Agriculture donors funded the project.
Calfhood vaccinations provide longer lasting immune healthWritten by Heather Smith Thomas
Newborn calves gain temporary or passive immunity from disease when they ingest colostrum from the dam since this “first milk” contains maternal antibodies. After a few weeks or months this temporary protection begins to wane, however, and calves must build their own immunities.
Vaccinating calves at the proper time can help protect them until weaning age. Vaccinating them too soon, however, may not stimulate much immune response. If the calf still has maternal antibodies in his system, these tend to interfere with building the calf's own immunities. The immune system sees no need to respond.
Chris Chase, who works in the Veterinary and Biomedical Sciences Department at South Dakota State University, says there are several considerations that producers need to keep in mind.
“When maternal antibody protection begins to wane, we can probably get a good response to vaccinations by about three months of age. It all depends on how much protection the calf received at birth – how much colostrum, how soon for maximum absorption of antibodies and how good it was,” he explains.
“In most herds, we won’t find 100 percent of the calves fully protected. It’s more like 70 to 80 percent. When developing calf vaccination programs, we need to know what disease problems are going on in the herd,” he adds.
If it’s a herd that has had issues with bovine respiratory syncytial virus (BRSV), for instance, this will necessitate a different plan than if the herd has not had problems.
“BRSV is notorious for having maternal interference at low levels that can last for a long time,” says Chase.
If the calf received some antibodies against BRSV from colostrum, the calf may not gain much immunity from an injected vaccine, unless it is adjuvanted, until those maternal antibodies are gone from his system.
“Producers need to have a plan for their own situation. There are many protocols, and a rancher might decide to give their calves vaccinations for IBR (infectious bovine rhinotracheitis) and BVD (bovine viral diarrhea), but in reality those two diseases are generally not an issue in young calves,” Chase says, adding that ranchers need to be more concerned with these diseases as calves approach weaning age.
“Some herds, however, have trouble with summer pneumonia in young calves, and BRSV is a problem. In these cases we can use the intranasal vaccine,” says Chase.
“The intranasal vaccine does have the ability to get around maternal antibodies. The other thing a producer can do is use an adjuvanted vaccine. In most cases people think that only an inactivated vaccine is adjuvanted, but we do have some adjuvanted modified-live vaccines,” he explains.
“If we know we have a summer pneumonia problem, BRSV is usually the culprit. There’s no vaccine just for BRSV, however. We have to use the combination product, even though at this age in calves the BRSV is the only thing we are really worried about,” he says.
“Producers need to know what they are dealing with. There are some tests, using deep pharyngeal swabs and some other ways to get material from deep in the back of the throat, to get a more accurate diagnosis,” Chase says.
A diagnosis is important to know what diseases should be included in a vaccination program.
“At this point in time, the intranasal vaccine will give the most likelihood of success and the least likelihood of failure in that age group. From two weeks up to three months, this makes the most sense, particularly if producers are worried about BRSV. The adjuvanted modified-live vaccine, where we give a single dose, also has some usefulness, but I haven’t seen enough data yet in young calves with agents other than BVD,” he says.
For calves, depending on what the producer must deal with, there are also seven-way clostridial vaccines that can be given at a young age.
“The interesting thing with these is that the literature tells us that if there are maternal antibodies present, they might not work, but field experience shows that those vaccines definitely have some efficacy. This is especially true if we are looking at C. perfringens in young calves, or blackleg,” he says.
“We can give these vaccines and not have to worry about problems with maternal antibody interference. Part of the reason is that with Clostridia we are actually vaccinating against an exotoxin. This is a simpler antigen, and it’s easier for the immune system to see and attack, compared with some of the viruses,” explains Chase.
If a producer is having problems with enterotoxemia, for instance, calves can be vaccinated at a very young age, even if the cows were vaccinated during pregnancy to stimulate high levels of maternal antibodies in the colostrum.
As a rule of thumb, most western ranchers give calfhood vaccinations at branding time.
“When vaccinating calves at this age, the goal is often just to prepare them for whatever they will encounter at weaning time,” says Chase.
It’s like a set-up vaccination that will then be boostered at weaning. If producers want to give a vaccination just prior to or at weaning, it’s good to have this initial shot at an earlier age, he adds.
Maternal antibodies tend to interfere longer with some of the viral diseases, compared with some of the bacterial infections that create toxins.”
“The viruses are big proteins and have to be broken down and processed by the immune system to be fully recognized and attacked,” he says.
Plague vaccine aims to support prairie dog populationsWritten by Saige Albert
Meeteetse – Black-footed ferrets were thought to be extinct until the 1980s when ferrets were found outside Meeteetse.
“In 1979, the last Black-footed ferret perished in South Dakota,” said Wyoming Game and Fish Director Scott Talbott. “In 1982, they were found in Meeteetse.”
In 1984, 120 ferrets were located in the Meeteetse area, but canine distemper killed many of them. At the same time, sylvatic plague ran rampant through the white-tailed prairie dog population that provided the ferrets’ main food source.
Talbott noted, “In the mid-1980s, ferrets were taken into captivity, and there is a huge partnership of folks who have worked to help recover the species.”
Retired Wyoming Game and Fish Department Education Specialist Dennie Hammer noted, “Black-footed ferrets are still considered one of the rarest species in all of North America, and it is a tribute to Wyoming and all of the partners over the years that we can say we still have ferrets and the habitat they need to survive.”
On July 8, researchers, wildlife specialists and others gathered at the Pitchfork Ranch outside Meeteetse to hear about the latest developments in the path toward reintroducing Black-footed ferrets.
Researchers and Wyoming Game and Fish Department personnel described a current field trial to combat sylvatic plague that is being conducted at the ranch.
Prairie dog populations
To successfully reintroduce Black-footed ferrets on the landscape, thriving populations of prairie dogs are necessary. However, prairie dogs across the West continue to be decimated by sylvatic plague.
Over the last 15 years, Tonie Rocke of the University of Wisconsin-Madison has worked to develop a vaccine to combat sylvatic plague.
Wyoming Game and Fish Department Public Information Officer Renny McKay noted, “If this vaccine proves to be successful, it can be used in targeted places where we want to reintroduce Black-footed ferrets on the continent.”
Over the last three years, Roche’s vaccine has been utilized in field trials across the West.
“Pitchfork Ranch is one of 29 sites that has hosted research on sylvatic plague vaccine,” explained McKay.
In its third season of field trials, many of those involved are optimistic about the potential success of the vaccines.
“Right here on Pitchfork, we have a colony of prairie dogs with two plots that are our study area,” explained Jesse Boulerice, nongame biologist for the Wyoming Game and Fish Department. “Each plot is 40 acres.”
Boulerice continued, “One plot will receive a bait that contains the vaccine for plague, and the other receives a placebo bait.”
The study is blind, meaning that researchers on-the-ground conducting the study do not know which plot is receiving vaccine and which is receiving placebo baits.
The vaccine is delivered in a peanut butter-flavored bait that also has a biomarker to determine whether the prairie dogs have received the vaccine.
“After the animal ingests the biomarker, it marks the hair and whiskers. If we pull a whisker and look at it under ultraviolet light, it fluoresces,” Rocke said.
Prairie dogs are captured and tagged, giving each animal an individual identification. When they are captured, hair and whisker samples are taken, and the prairie dogs are combed for fleas.
“We can send the fleas to the lab to identify the species and see if the flea is carrying plague,” Boulerice said.
The animals are sedated for the process to reduce stress.
Though the study is only three years into a four-year project, Rocke says that preliminary results have shown that 90 percent of prairie dogs are eating the bait.
“We see the biomarker in the hair of almost every prairie dog we capture,” she said. “They eat it readily, and we think that they are getting used to it over time.”
Laboratory trials are also very encouraging, with 95 percent survival rates after a challenge with the oral vaccine after two treatments.
“We don’t know anything about the success rates yet,” Rocke said, “and we won’t know until we get our data in, un-blind the study and look at the data.”
Over the next year, researchers will continue to collect data, hoping for positive results at the end of the study.
“There are a couple of things that are limiting in the recovery of the Black-footed ferret – one being plague that takes over prairie dog town and eliminating the food source for ferrets,” said Mark Sattleberg of U.S. Fish and Wildlife Service. “This vaccine is a hope in the recovery of the Black-footed ferret.”