Published Date: 2012-10-07 19:27:49
Subject: PRO/AH/EDR Anthrax, bovine – USA (08): (CO)
Archive Number: 20121007.1329339
ANTHRAX, BOVINE – USA (08): (COLORADO)
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: 4 Oct 2012
Source: Journal Advocate [edited]
Last week, the Colorado Department of Agriculture’s State Veterinarian’s Office announced that no premises remain under quarantine in the Logan County anthrax outbreak. At a Rotary Club meeting on Wednesday [3 Oct 2012], Richanne Lomkin, veterinary medical officer for northeastern Colorado, explained why it took so long to diagnose anthrax and what occurred after the diagnosis.
Part of the reason anthrax didn’t come up as a possibility right away is because Colorado hadn’t seen a case of anthrax in more than 30 years, and there was no written record of anthrax ever being found in Logan County [Note the word "written." - Mod.MHJ]. “There was a reason why it took so long to figure this out: Nobody was thinking anthrax,” Lomkin said.
Anthrax is very fond of alkaline soils, which are common in Colorado. “It’s actually surprising that we don’t have more anthrax cases here, considering that we do have some of the environmental factors that it really likes,” Lomkin said.
In order for anthrax to cause infection, it enters its victim by ingestion, inhalation or open wounds. “I feel that we probably saw some fly spread on our outbreak in northeastern Colorado, but that’s my opinion, I don’t have any true documented evidence to back that up,” Lomkin said. She explained that flies could gather the spores on a carcass’s body, move to a living animal, and if they find an open wound, get anthrax in it and cause infection.
The cattle may also have ingested anthrax spores that got onto the grass they were eating, since they were eating closer to the ground due to drought conditions. “That certainly helped make this happen as badly as it did.”
Inhalation of the anthrax was unlikely. “None of us truly were at all concerned about inhalation anthrax in this outbreak,” Lomkin said. She explained that cattle wouldn’t have inhaled anthrax unless maybe they were wallowing in a dust hole where there were anthrax spores, and conceivably they could have inhaled enough to cause an infection [At best, this is an hypothetical source of infection. - Mod.MHJ].
Lomkin said 6 people were originally exposed to the anthrax: her and those who handled a dead carcass or helped in the corrals where a lot of cows were dying, and it was very dusty.
The outbreak started on 20 Jul 2012 when a rancher found 8 adult cows dead in one pasture. The pasture was below drainage from an irrigated field, and there were leaves and other items in the drainage, so the rancher thought some kind of toxicity caused the deaths. All cows were moved off the pasture that day into a corral, but they kept dying. The rancher called a local veterinarian, who necropsied 2 cows, collected samples, and sent them to the diagnostic lab, and they came back inconclusive.
On 2 Aug 2012, 5 adult cows were found dead in a different pasture. The rest of the cows were moved off the pasture and put into different corrals, but they continued to die. “If it had been a plant toxicity, they should have stopped dying once they moved them off those pastures and put them in corrals and started feeding them hay,” Lomkin said. Cows continued to die through 7 Aug 2012.
The rancher took 4 cows, 2 different groups, to the CSU diagnostic lab. During that time, a 3rd pasture was affected.
A determination couldn’t be made with the 1st 2 [carcasses] because they had pretty much melted by the time CSU got them. But on 7 Aug 2012, they were able to diagnose anthrax with the other 2, thanks to a vet student.
Even the clinician at CSU, who is from Egypt and has seen anthrax, wasn’t thinking of anthrax. “Cows in Egypt have been exposed to enough anthrax that when they got it, they had enough time that their spleens got really large,” Lomkin said. “These cows, never having been exposed to anthrax at all, literally were dying before you could have any clinical signs.”
Once the preliminary diagnosis was made, CSU called the state veterinarian, who then called Lomkin. There were more than 40 dead cows at that point. “I had not heard anything about this yet before then,” she said. “There’s a question as to whether I should have or not.”
The morning of 8 Aug 2012, Lomkin met with the Logan County Commissioners, local veterinarian representatives, and emergency responders to discuss what to do. The state veterinarian was also involved in the meeting via phone.
By noon on 8 Aug 2012, Lomkin and the emergency responders were at the ranch planning how to destroy the affected carcasses. She said they wanted to get these carcasses destroyed as fast as possible and didn’t want them to reappear 50 years from now when somebody comes in with an oil rig or something digs the area up and exposes that dirt to the environment and to future grazing. “Burning is our best thing that we can do with these carcasses,” she said. Carcasses were burned from 9-11 Aug 2012.
Lomkin thanked the volunteer fire department and Logan County Road and Bridge Department for their help with the fire, which was done in a pit that was already there.
“One of the concerns was that we really had to get these burned very well, because we’re going to get some drainage through this pit obviously,” Lomkin said. “We needed to make sure that if we were going to burn these cattle in this pit that we were going to burn them to the point where we wouldn’t have any anthrax spores left that could wash out of there.”
There were 3 neighboring premises that each had one cow die of anthrax, probably because they didn’t vaccinate and treat the cattle soon enough. All the affected pastures on those 3 other premises were quarantined for 30 days, after they either completed vaccination and treatment or 30 days after the last death. As of 23 Sep 2012, all of those quarantines have been released.
Some question whether the county should have spent that much money when only one ranch was affected. “My answer is yes, because if we don’t get that under control with the one person, we could end up with a huge number of ranches affected,” Lomkin said.
– Communicated by: ProMED-mail firstname.lastname@example.org
[There were, in the end, some 60 cases on the index ranch and single cases in 3 adjoining ranches. To have burnt this many carcasses in 3 days demonstrates a high level of efficiency. All concerned are to be congratulated.
This is being posted as this account brings up a number of useful points:
- Just because you have not observed any anthrax cases in past years is no reason to dismiss the possibility, especially when your stock are on alkaline soils. Also, gossip has it that sporadic deaths had possibly been ignored and the carcasses dumped off to the pasture margins.
- Corralling stock may be the correct action when threatened by a plant poisoning, but with anthrax, it grossly increases the chances of the other stock having access to any blood extravasated from an affected anthrax carcass and dying, the same scenario responsible for the excess sheep deaths in San Angelo, Texas earlier this year (2012).
- All in all, some 20 days passed between the 1st cases and burning started. Thus, there was a serious risk of ground contamination. Some can be shoveled up and thrown into the burn pit and some disinfected, but in reality, much will have remained. This surface soil can stay contaminated for up to 3 years or more. Thus, both from an appreciation of a possible return from the original unrealised source and from where dead cows had lain, this herd must be revaccinated each spring for a minimum of 5 years, and preferably 10 years. - Mod.MHJ
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