Yellowstone Elk, Montana Cattle & Brucellosis

Posted by Jeffrey St. Clair on July 9th, 2008 | Link

There Is No Scientific Proof that Elk Infected Montana Cattle with Brucellosis
Comment by Robert Hoskins, Naturalist, GravelBar

Since the second discovery of brucellosis infected cattle in Montana’s Paradise Valley north of Yellowstone National Park over the last year, a discovery that has cost Montana its brucellosis free status, the livestock industry–especially the Montana Stockgrowers Association and the Montana Department of Livestock–has been quite vocal in blaming Yellowstone elk for allegedly transmitting brucellosis to cattle in both incidents. They are using this claim to demand the slaughter of elk in Yellowstone National Park. YELLOWSTONE NATIONAL PARK–ONE OF THE ECOLOGICAL CROWN JEWELS OF NORTH AMERICA. The authorities are already slaughtering Yellowstone bison by the hundreds and thousands, ostensibly to control the transmission of brucellosis to cattle–a policy that clearly has failed, as I argue in my letter on this thread at http://www.billingsgazette.net/articles/2008/07/06/opinion/letters/30-brucellosis.txt. Slaughtering elk to control brucellosis has even less chance of success than slaughtering bison.

Unfortunately, the various news stories on this Google thread have generously and unquestioningly printed this claim about elk. However, I do question it, since the authorities have offered no evidence, scientific or otherwise, for the claim.

Brucellosis is a bacterial disease that causes female ungulates (e.g.cattle, elk, bison) to abort their calves during the third trimester of pregnancy, which I call the “window of transmission.” With wild ungulates, this “window of transmission” occurs between late winter and early spring; this is the time when the risk for transmission of the disease among ungulates is the highest. The disease is transmitted when ungulates nuzzle or physically contact the aborted fetus and/or accompanying birth materials, generally on a feedline or in other high-density situations, such as on Wyoming’s elk feedgrounds. Approximately 50 per cent of female ungulates abort their first calves, but later births tend to proceed normally. Thus, it is not a biologically serious disease for ungulates; essentially, it is an “economic disease” for the livestock industry merely because it affects production of a profitable commodity–the calf. It has minor impact on productivity of wild ungulates.

Whether elk infected Montana cattle is a scientific, epidemiological question, and the answer requires scientific proof. However, to date, Montanan and federal livestock authorities have refused to release the results of their epidemiological investigations into these two brucellosis incidents. Their refusal to release information, which under both Montana and federal law is public information, raises questions about the veracity of the claims about wild Yellowstone elk as the source of the infections. They have provided no scientific proof that elk were the source or that cattle were not the source. Saying it’s so doesn’t make it so.

The epidemiological investigation for the first incident was botched from the beginning. We know that with this incident, the Morgan/Malcolm/Bridger outbreak, the authorities failed to secure tissue samples from six of the seven cattle that tested positive for brucellosis exposure before the cattle were butchered and sent into the food chain. Such samples, through a culture test, would have shown whether or not the cattle were actually infected with brucellosis and also would have provided DNA evidence from the cultured bacteria as to the source of the infection. The reason given for failing to secure these samples is remarkable, given the claim that brucellosis is a serious disease–the slaughterhouse owner refused to allow the authorities access to the slaughterhouse and the authorities, although they certainly had the right under federal law to go into the slaughterhouse to secure the samples, decided not to exercise their authority in “respect of private property rights.” (This decision alone raises questions about the claim about the severity of brucellosis; were brucellosis truly a serious disease, the authorities would have entered the premises regardless of the owner’s protests, because it is a commercial establishment explicitly subject to government regulation and inspection).

So, the authorities had only the single sample from the remaining cow. However, they have not released the results of either the culture test or the DNA test, assuming these test were done. It is not clear at present that these two tests were actually done.

However, to give the authorities the benefit of the doubt, let’s assume that they did complete an epidemiological investigation into this first incident–regulations set a deadline of 60 days to complete such an investigation–including culture and DNA tests. Now the question is, why haven’t they released the report or its supporting data, despite repeated requests from the public to do so?

Despite their refusal to release this information, the authorities nevertheless are claiming they could not establish a cattle source for the first incident, and that therefore they have concluded that elk were the source of the infection. Where’s the proof? To my mind, their refusal to release the report or the data on which the report is based raises serious questions as to the validity of their claims about elk. In comparison, when investigations into the brucellosis outbreaks among Wyoming cattle in 2004 were completed, the information was immediately released–no doubt because the investigation clearly pointed to an elk source. In Wyoming, the authorities had the “smoking gun” for an elk source–feedground elk. But do they have it in Montana?

The investigation into the most recent incident of brucellosis in Art Burns’ herd of Corriente cattle (best known as roping cattle for rodeos) is still ongoing, yet it is curious that the authorities have nonetheless once again blamed elk in numerous press releases and news stories even before the results are in.

I believe that if the authorities had the “smoking gun” in Montana to prove an elk source for the first incident, they certainly would have released the epidemiological report and supporting data to prove it. Their refusal to do so suggests to me that they can’t prove an elk source. And if they can’t prove an elk source, then it follows that the source must have been cattle. The same is true of the Burns incident.

What follows is my reasoning to suspect a cattle source for the Montana brucellosis incidents.

Scientifically, it is highly unlikely that Yellowstone elk infected Montana cattle in these two incidents. With the outbreaks of brucellosis in four Wyoming cattle herds in 2004, we know that both the following risk factors are necessary for elk to infect cattle with brucellosis. These two factors constitute a “threshold of infectiousness” for elk to cattle transmission of brucellosis. They are:

1) The elk must have a high prevalence of brucellosis (otherwise known as “hot” elk), as do the elk on Wyoming’s elk feedgrounds. High seroprevalence in Wyoming elk is the consequence of decades of artificially feeding elk at unnaturally high densities on the feedgrounds, most of which are less than 100 acres in size but confine hundreds of animals at a time and

2) Close and continuous contact between “hot” elk and cattle during the third trimester window of transmission for brucellosis.

In Wyoming, these risk factors existed; we know that “hot” elk were being fed in close proximity to cattle even though these risk factors are well known to ranchers and wildlife managers. In short, the Wyoming infections occurred due to the negligence of the landowner and the Wyoming Game & Fish Department when they allowed cattle and “hot” elk to mingle in close and continuous proximity during the “window of transmission” for the disease.

Neither one of these risk factors exists in Montana, much less both. The prevalence of brucellosis is known to be low in Yellowstone elk, and I have personally asked the Montana State Veterinarian, Dr. Marty Zaluski, whether elk were being fed in close proximity to cattle prior to the Malcolm/Morgan/Bridger incident. He said no. Nor has Dr. Zaluski or any other livestock official provided evidence that “hot” elk were being fed in close and continuous proximity to the Burns herd.

Because the “threshold of infectiousness” doesn’t exist in Montana, it is highly unlikely that elk infected cattle in either brucellosis incident.

Since it is unlikely that Yellowstone elk infected these cattle, the source must have been cattle. There is good circumstantial evidence for a cattle source. An interesting coincidence with both Montana incidents is that Corriente cattle were involved. The Corriente is a South and Central American/Mexican breed descended from Spanish cattle imported by the Conquistadors and Spanish colonists in the 16th century. Corrientes are horned and have become very popular on the rodeo circuit as roping animals. They are also being marketed, primarily in Texas and the American Southwest, as a desert- and drought-tolerant breed that can adapt to hotter and drier conditions caused by climate change. (A Native American friend of mine has, with tongue in cheek, described the Corriente breed as “the white man’s buffalo”).

The primary reason to suspect these Corriente cattle as the source of the Montana brucellosis incidents is their popularity as rodeo stock. Rodeo stock–cattle and horses–travel through many western states and have contact with other livestock in the rodeo corrals. Regulation of livestock in both intra- and interstate movement in the rodeo circuit is spotty at best and, because such animals do not change ownership (presumably) on the rodeo circuit, the usual disease testing requirements when ownership changes do not apply. And even if the requirements did apply, on the ground regulation on the rodeo circuit is so poor that many animals would slip through the cracks.

I strongly suspect that rodeo corrals, which are equivalent to feedlots, are a likely source of many livestock diseases in North America, including brucellosis. Rodeos deserve stronger scrutiny from livestock disease surveillance officials.

Thus, the rodeo circuit may be the source, via Corriente cattle, of Montana’s brucellosis outbreaks. A rigorous and honest epidemiological investigation would prove or disprove that suspicion. But as yet, we’ve seen no evidence that such an investigation took place, or if it did, whether it was done with scientific rigor and honesty. Instead, the authorities and the livestock industry are very quick to blame wild Yellowstone elk, and expect us to believe them without providing proof. But I don’t believe them.

In closing, I’d say that the epidemiology of both Montana brucellosis incidents should positively prove or disprove whether elk or cattle caused the infections. The technology certainly exists to provide that proof. DNA testing on brucella bacteria cultured from tissue samples of seroprevalent cattle in both incidents would certainly disclose the source of the infections, either elk or cattle, with a high degree of confidence.

So I call upon the authorities to release the results of their “investigations” with all supporting data. Given the contentiousness of wildlife-livestock politics in the Greater Yellowstone, they have a duty to do so. Failure or refusal to release this vital information is all the evidence I need to conclude that elk were not the source of these infections and that cattle were the source, no matter how loudly the authorities blame elk for reasons known only to themselves.

Quite frankly, the elk and bison of Yellowstone National Park are far more valuable than Montana’s cattle or cattle industry.