From veterinarian to forensic detective: Solving a mysterious swine disease

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In fall 2019, a client called into Four Star Veterinary Service clinic in Mexico, Indiana, and reported the loss of a lot of sows. Daniel Gascho, DVM, knew the client and headed out to the business site, which was a buying station.

On the way there, Gascho said he had several ideas of what could cause the sow mortalities before arriving. But once he was on site, he knew he was wrong.

“It’s really a good reminder that no matter how many times you think you know all the diseases…Then you get there and it wakes you up and reminds you, ‘Oh, there’s stuff out there you’ve never seen before,’” Gascho said.

Heavy death loss

The first clue of an unusual situation was the high number of mortalities. Gascho estimated a capacity of about 1,000 hogs at the site. About 500 head died in a week.

“If that many pigs are dying that fast, I initially wasn’t thinking a pathogen…because in this country we don’t have many diseases that kill pigs that fast, that many,” Gascho explained.

Then he explored the possibility of other “one-off stuff that they mention in vet school that you almost never actually see.” One was a lightning strike but that didn’t make sense. The other was a toxin in the water or feed.

“But the odd thing was, at the same buying station were multiple species. They were not affected. If it was something in the water, it’s pig specific.”

Next, he checked out the feed for the possibility of botulism, excess ionophores or anything else. But he learned the company bringing in the feed takes the exact same diet to other finishers in the area, and no other site was affected. He also looked at other environmental issues like stray voltage, ventilation failure or pit gases. These were dead ends too.

Forensic investigation

“I felt like a forensic investigator,” Gascho said. “I’m taking feed samples and water samples, checking other species, checking the environment and just really scratching my brain.”

During the first visit to the site, Gascho did report the situation to the authorities in case it turned out to be a foreign animal disease. He also took a full set of samples for testing at Iowa State University’s (ISU) diagnostic lab.

“Of course, they tested for everything under the sun,” he said. “Negative, negative, negative.”

Smoking gun

Gascho was called out to the buying station again. This time, the client had brought in 500 to 600 feeder pigs for a roaster market. The pigs were in perfect health, but half of the pigs died within 48 hours of arrival.

“It was still a disaster at this point,” he said. “I’m standing in a pen…and pigs were literally dying in front of me.”

Gascho again collected sets of tissues from multiple pigs as well as samples of feed, water, etc. He sent everything off to the ISU lab for more testing.

Eventually, the lab noticed an unusual pattern with a pathogen that normally causes disease in horses and not swine. But in every sample cultured from the sick pigs, the same pathogen showed up.

S. zooepidemicus

The mystery was soon solved. Repeated lab tests showed the pigs were dying from Streptococcus equi ssp. zooepidemicus. It was the first diagnosis of the disease in swine in the US.

“It’s just an extremely acute, full-bodied systemic bacterial sepsis, raging inflammation of every organ, organ failure and death,” Gascho explained.

There was a silver lining to the diagnosis. “It was susceptible to about every readily available product we have,” he added. And the pathogen also did not appear to aerosolize.

Gascho and the client were able to depopulate pens, clean and disinfect them, and successfully move new pigs in without any further problems.

Mystery solved.

 

Inadequate iron supplements lead to subclinical anemia in young pigs

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A field trial evaluating iron supplementation for baby pigs found the typical 200 mg iron shot at birth is not enough. The trial was prompted by a client who wanted to compare different iron supplementation methods, reported Brittney Scales, DVM, Four Star Veterinary Service in Mexico, Indiana.

Using a handheld device called a HemoCue, Scales was able to easily test pig hemoglobin levels during the trial. The device identified subclinical anemia in pigs that were not exhibiting signs of anemia.

“A lot of farmers think if they don’t have pale pigs, then they don’t have a problem with anemia,” Scales said. “We just take an ear prick [with HemoCue] and get a blood sample really quick…and actually have a concrete number to show [the producers] that their pigs are subclinically anemic.”

Field trial results

The three iron-supplement treatment groups used in the field trial include:

  • One 200 mg iron shot at day 1
  • One 100 mg iron shot at day 1 and a second 100 mg shot at day 10
  • One 200 mg iron shot at day 1 and oral iron 7 days pre-weaning

The best outcome came from the 200 mg iron shot followed by oral iron, a protocol her client requested. However, Scales prefers to use a second 200 mg shot at 10 days of age.

“We’re finding in a lot of research that two 200 mg injections are best…with over 70% of the pigs in the optimal range of hemoglobin,” she explained.

The protocol producing the worst outcome was the one 200 mg shot with no iron follow-up. The protocol with two 100 mg shots spaced apart did better, with higher levels of iron.

“When you break up that iron, you get better results,” Scales said. “We found if you do two shots of iron, whether that’s 100 mg or at best 200 mg shots twice, that is where we find the best results in pigs.”

Two-shot iron extra labor

“The first shot is typically within the first day or so of age,” she explained. “Depending on how labor is on the farm, we’d like for the follow-up shot to be over a week past the first shot. I think there are producers who still do just one shot because of labor costs and not having enough labor to pick up those pigs the next time.”

The cost of not following up with the later, second shot may be more expensive than previously thought.

“When the piglet’s blood is low in iron, the red blood cells do not do as well carrying oxygen throughout the body,” Scales said. Adequate levels of iron are required to optimize growth and support a healthy immune system. This means downstream, these subclinically anemic pigs will have lower weights and lower average daily gain than pigs that are not anemic.

“It’s a very costly, well-hidden problem that we don’t even recognize,” she added.

 

Don’t forget rodent, insect control during biosecurity checks

By Brad Schmitt, DVM, Four Star Veterinary Service, LLC

Biosecurity in a hog operation usually focuses on people and practices like showering in, UV irradiating supplies and filtering incoming air. But rodents and insects can bypass all those critical control points on a hog farm.

Biosecurity is only as good as its weakest link, so pest control needs to be a top priority, whether you’re operating a genetic multiplier, sow farm or a wean-to-finish barn.

Spread disease, damage property

Brad Schmitt, DVM

Rodents and insects act as mechanical vectors to introduce new pathogens into naïve populations from the outside world. These pests will spread dormant viruses from a manure pit to the pig level. The viruses may include porcine reproductive and respiratory syndrome, porcine epidemic diarrhea, sapelovirus and teschovirus.

The pests can also track bacterial pathogens like Lawsonia and Brachyspira (swine dysentery) from pen to pen or crate to crate.

Rodents and insects including ticks, lice and biting flies also propagate diseases like leptospirosis, Mycoplasma suis, swine pox and African swine fever.

Rodent populations, when left unchecked, can cause significant damage to swine facilities. They can quickly deteriorate curtains, walls and insulation, leading to costly, ongoing repairs. In addition, ventilation and temperature controls are compromised when buildings deteriorate, which negatively impacts pig performance.

Feed waste erodes workplace

Feed wastage occurs from rodents eating and digging through feeders and pushing feed into the pit. This may not seem like a big deal, but a large population of rodents can really amplify the issue. In today’s economic climate, every penny counts.

In addition, pest infestations make for undesirable working conditions. In an era where steady farm labor is hard to secure, it’s important to provide an optimal work environment.

If you’ve ever inhaled a swarm of gnats, donned a mouse-inhabited boot or showered-in with cockroaches, you’ll understand the impact that pest control can have on workplace satisfaction.

Setting up effective rodent control

Effective rodent control starts with a rodent audit to assess the situation, sometimes employing the use of infrared surveillance cameras to monitor night-time activity. This process determines points of entry, heavily infested areas and paths most travelled. Once these are determined, bait stations can be strategically placed inside and outside of barns. Spacing and location of bait stations will depend on mouse versus rat infestation in addition to other factors.

Bait-station maintenance should be done on a regular basis, with frequency depending on the severity of infestation. One or two people should be designated to this task, as giving ownership of the process helps with compliance. Ongoing assessment of bait disappearance will determine if bait rotation, supplementation or adjustment of stations is necessary.

Bait rotation important

Bait rotation is periodically used to change the active ingredient, flavor and texture. Doing so prevents monotony and promotes bait intake, which prevents resistance. This can also be accomplished by rotating between anticoagulant and neurotoxin-type baits, especially in cases where the resident population becomes resistant to one mechanism of action. For example, as anticoagulant resistance starts to build, neurotoxin baits are implemented to reduce the resistant population, then anticoagulants again become an effective mode of control.

Just because one particular bait has been effective on your farm in the past does not mean it should be used continuously. Rotation of baits will preserve that efficacy for the long-term future.

While rodenticide can be an effective means of rodent control, prevention must also be practiced. Management practices to eliminate rodent habitats and feed sources are an integral part of keeping the population to a manageable level.

By removing debris and vegetation from the building perimeter and creating a 3-foot-wide buffer zone with coarse gravel, rodents are deterred from entering or burrowing under the barn. In addition, timely clean-up of feed spills and maintaining leak-free bins and augers prevent the rodent population from flourishing.

Insect-control tips

Much like rodent control, an insect-control plan starts with identifying the target and being familiar with its life cycle. Some insects such as flies lay eggs and persist in the environment, while mites and lice require a host to survive.

Insect life cycles and hatch times dictate control strategies and dosing frequencies. When selecting insecticides, look for those with a longer residual effect, reducing the need for frequent application.

Many great insecticides exist, but none are effective at killing all species. For this reason, multiple products and routes of exposure may be warranted. Combinations of premise sprays, injectables, pour-ons and feed-grade insect growth regulators may be used in addition to proper sanitation.

Sanitation is crucial as flies and other insects are attracted to manure. By thoroughly cleaning and disinfecting barns between turns, minimizing manure build-up while pigs are present and keeping pits pumped down to acceptable levels, fewer insects will reside at animal level.