A Disease That Just Won't Go Away
My July 2007 column was titled "Taking Another Look at Bovine Tuberculosis." I was prompted to write that article because of a news item that had garnered much media attention at the time. At the time of the report a person who was reported to have had a multi-drug resistant strain of human tuberculosis exposed passengers on two international flights. Even more recently, a passenger tested positive for tuberculosis after sitting next to someone who had drug-resistant human tuberculosis on a flight from India. That occurred in April of 2008.
While the focus of this article is not exposure to tuberculosis while on international flights, it does serve to remind us that tuberculosis refuses to go away—in fact, in many areas it is on the rise. And while human tuberculosis and bovine tuberculosis are not the same disease, there are similarities in the rise of prevalence of these two related diseases.
Here in the United States, we are fortunate that human tuberculosis has been on the decrease since 1993. The rate of decrease has, however, slowed in recent years. Still there were 13,299 newly diagnosed cases of human tuberculosis in the U. S. in 2007. There were also 644 deaths caused by tuberculosis in 2007 compared to 1202 deaths in 1996. The slowing in the decline of the disease in our country can be attributed to many factors including increased international travel and an increase of people with compromised immune systems like HIV patients and organ transplant recipients.
Bovine tuberculosis, however, is on the rise here in this country. At a recent U.S. Animal Health Association Meeting, the State Veterinarians from each state met on Saturday afternoon. Several topics of current interest were covered. However, one topic kept coming up throughout the day. That subject was bovine tuberculosis. States like Michigan, Wisconsin and New Mexico reported on the disease in their state and how they were handling it. Dr. David Fly, New Mexico’s State Veterinarian, reported that in his state he had no field staff, so he and his Associate State Veterinarian along with federal USDA Veterinary Services personnel were doing the work. I made one of those off-the-cuff comments about "if you need any help, just holler." A couple of weeks after the meeting was over, Dr. Fly called to find out when I was coming out to help with their TB situation. I told him that if New Mexico would foot the bill, we would be more than happy to come out and help.
As they say, be careful what you wish for or offer. Actually, travelling to New Mexico was a great opportunity to work in a disease response detail. We have had several response exercises in Alabama, but I had rather do the real thing in someone else’s state. We were working with the New Mexico Livestock Board in partnership with USDA Veterinary Services in response to TB in the state’s dairy herd. The disease has shown up in cull dairy cows at slaughter and the state has received cows exposed to TB from other states.
Accompanying me on the trip to New Mexico were Dr. Chris Bishop, Veterinary Medical Officer from Alabama, and Joe Dickerson, animal health technician. Upon arriving in Albuquerque, we met Dr. Fly, who gave us a map and directions. We drove three hours to Roswell in the high desert part of the state. (No, we did not see any UFOs). The next morning at 6:00 we met a veterinary medical officer from New Mexico and ventured another 30 miles to a dairy in Artesia. The dairy milks 2,500 cows twice daily and is considered a small dairy for New Mexico. The average size dairy is 7-8,000, with the largest being about 14,000.
The protocol was to inject 0.1 cc of tuberculin into a skin fold at the base of the tail and in 72 hours to examine the injection site for any swelling. Those with any detectable swelling were considered to be suspects and blood samples were drawn to confirm if they were infected. After a brief orientation with the state and federal officials at the dairy, it was off to the races. We began helping with the injections. The cows were all standing side-by-side at open stations, divided into several pens. Bear in mind I am from Brewton, Alabama, and I had never seen a sight like this. It seemed like Holsteins and a few Jerseys as far as I could see.
One unique element was the use of RFID (radio frequency identification) electronic tags used in these cattle. The tags were read with a hand-held wand reader that immediately transferred the information about the cow to a small PDA (computer-type) device. This allowed information to be confirmed or entered immediately. I suppose there are still kinks to be worked out, but it’s a far cry from the days of wiping manure off tags and test charts to be able to check a cow’s identity. Dr. Fly also wanted a metal tag in each animal. Experiencing the use of this type of equipment will be very valuable if we ever find ourselves in a similar situation.
Our work detail was a complete success in all areas. We were able to observe and physically participate in a major disease response complete with an electronic ID database system. The experience will prove invaluable. My hat is off to Dr. Fly, his staff and the USDA folks that are getting the job done out there. And, at least for now, I can be thankful we were dealing with the disease in New Mexico and not in Alabama.