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Published Date: 2004-08-29 23:50:00
Subject: PRO/AH/EDR> Anthrax, bovine, deer - USA (TX) (02)
Archive Number: 20040829.2415

ANTHRAX, BOVINE, DEER - USA (TEXAS) (02)
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Date: 25 Aug 2004
From: Martin Hugh-Jones <mehj@mail.vetmed.lsu.edu>

During 18-24 Aug 2004, I visited west Texas, and, with the generous help of
local ranchers and veterinarians, was able to go to the anthrax-affected
areas and interview ranchers involved. The epidemiological patterns of
these outbreaks seem to differ from each other.
[1] Outbreak 15 miles NW of Uvalde: On 27 Jul 2004, the manager of Ranch-A
asked for advice from the manager of the neighboring Ranch-B because of
deaths in his White-tail deer breeding pen. The Ranch-A manager only visits
his ranch at 1-2 week intervals. During the invited visit by the Ranch-B
manager, a white-tail buck was seen to come up outside the pen obviously
intending to drink at the water trough. It was patently not well,
staggered, and fell over dead. The carcass was taken to the ranch
veterinarian in Uvalde, who diagnosed anthrax based on a positive result
using the US Navy field ELIZA test; this was later confirmed by the
diagnostic laboratory at Texas Veterinary Medicine Diagnostic Laboratory,
Texas A & M (Agricultural & Mechanical) College, (TVMDL TAMU) College
Station, Texas.
During the subsequent 7 days, Ranch-B staff found dead deer within 100
meters of their 8-foot-high boundary fence with Ranch-A (there are dirt
roads on either side of this fence, and the boundary strip is kept
reasonably clear of scrub and brush). The 2nd week started with 2 kudu does
found dead in the high-fenced easternmost pasture of Ranch-B. In the
following days, dead deer were found throughout Ranch-B, but, in the 3rd
week, no dead deer were found in the north-west boundary area with Ranch-A.
In all, from 27 Jul to 16 Aug 2004, Ranch-B lost 18 animals: Aoudad sheep
and white-tails, Kudu, Axis, Eland, Scymitar oryx, Fallow, and Black buck
deer. A bull Scymitar, dying on 30 Jul 2004, was laboratory-confirmed to
have died of anthrax, and, in spite of claims of only 2 females dying, in
fact, roughly equal numbers of males and females died. All carcasses were
burnt. The ranch has 2000 acres and 600 deer of various species, domestic
and foreign, in 5 high-fenced sections. Deaths occurred in all of the
sections. The ranch is purposefully over-stocked, and the intention is to
provide "sport" trophy-animals.
The owners of the 2 ranches to the immediate north of Ranch-A are
maintaining an unusual silence in response to queries by friends and
neighbors. A quarter-horse on the goat ranch, at the south-east corner of
Ranch-B, died 2 days after being vaccinated against anthrax. The cause of
death is unknown.
The pattern of spread is what would be expected if infection was spread by
tabanid flies. Samples were taken, where possible, to confirm the cause of
death. We are awaiting reports involving other animals, and await news of
further results. We are going to try to find out where all deaths occurred
on both Ranch-A and B. In 2001, Ranch-B lost more than 75 of the resident
white-tails. This was just before the ranch was purchased by the present
owners.
[2] Ranch-C, Loma Alta: This ranch had deer deaths during the 2001 anthrax
epidemic. For a long, but unknown, time, this ranch was used to carry
purchased yearling steers over the winter and then was sold in March-April
2004. Thus, for 7 months each year, the ranch only carried deer. These deer
were not, and are not, fed intensively. It is more in the nature of
bait-feeding to attract animals to the deer stands.
In November 2003, the grazing was leased on a year-round basis, and
stocking began with "ranching cattle," nondescript animals of no special
breed type, including bulls and cows both empty and pregnant. The cattle
were rotated through the various scrub-covered pastures making use of the
available grazing. Between November 2003 and March 2004, 12 animals are
known to have died, out of the 407 purchased. Deaths continued, and it was
decided to sell off those cows due to calve in September-October 2004. A
roundup was attempted, and abandoned, on 21-22 Jul 2004. It was restarted
on 27 Jul 2004, with the animals worked, vaccinated with Sterne and 7-Way
vaccines, and treated with a pour-on parasiticide on 30 Jul 2004. 3 animals
died near the holding pens during 27-30 Jul 2004 and a further 5 animals by
4 Aug 2004, after being released into a fresh pasture. Anthrax was
diagnosed and confirmed. No more deaths have occurred since 4 Aug 2004. The
carcasses are being burnt. The ranch is still under quarantine.
Since November 2003, 42 individual animals have been lost, but only 28
carcasses have been recovered. When visited, the stock were not in the
condition that would be expected, considering the steady rainfall in a
region that normally has little rain or drought. 90 percent were thin. The
calves were OK, but not in top condition, with a few in poor condition. No
deaths have been noted in the unvaccinated ranch sheep and Angora goats. 2
deer had died recently but at opposite ends of the ranch.
This is the 1st time in many years that cattle have been on this ranch
during the summer "anthrax season." Though the cattle owner claimed that
they had been vaccinated against anthrax on entry, their overall poor
condition would have negatively impacted the efficacy of the vaccination.
How many anthrax cases had occurred in June/July 2004, before the condition
was recognized, is unknown. The cluster of 8 cases would have been infected
around 20-22 Jul 2004, if, for example, they had found a fallen herd mate
with extravasated infected blood, frequently described in the textbooks,
but less often seen in the field. The owner presently has his ranch hands
out looking for this putative causal case in the pasture that the cows were
grazing in before the round-up and working began. Tabanid flies are not an
obvious problem on this ranch at this time.
An alternative, and speculative, hypothesis would be that the cattle had
latent infections from grazing contaminated land, and the disease was
facilitated by their poor condition and initiated by the stress of being
rounded up. It is poorly described in the literature, but the best
description of latent infections occurred 9 months after the widespread
commercial pig epidemic in 1952 in Iowa, Ohio, and Indiana, when enlarged
lymph nodes in healthy slaughtered pigs were found to contain viable
_Bacillus anthracis_. As an hypothesis, it would help explain the worldwide
distribution of _B. anthracis_ A-strains, and, the constancy of summer
outbreaks; the B strains are seldom found, and, normally restricted to high
pH soils. Texas only has A-strains.
[3] Elsewhere: No other outbreaks are known of, or suspected, at this time.
Of more concern is that the deer ranches in Val Verde and Uvalde counties
are now feeding chlortetracycline-laced deer feed. While that may protect
them, if fed in the proper amounts, some ranches only have bait-feeding,
which will result in low levels being ingested, and, will significantly
increase the risks of generating resistant strains of _B. anthracis_.
[4] Burning the carcasses ("British BBQ" (in contrast to the well known and
respected Texas BBQ): Burning the carcass of any animal is a slow and
expensive business. We found we could burn a white-tail deer carcass
successfully, quickly, and cheaply using charcoal briquettes. This was
carried out as an experiment on another deer ranch. You need three 20 lb
bags of cheap briquettes, plus one 10 lb bag, and 3-5 gallons of diesel
fuel (and one six-pack of a suitable rehydrating fluid for the burning
crew). If possible, the carcass should be burnt where it lies. If the
vegetation is highly flammable, do it elsewhere where it is safe. Lay out
the bags with the small bag positioned to take the head and neck. Slice the
bags open and slosh the briquettes with diesel. Place the dead deer on the
briquettes, pour some diesel on it, remove the diesel container a suitable
safe distance, and carefully ignite the carcass. The charcoal briquettes
allow a good draft in under the carcass. If the carcass was moved from
where it had originally been, take a shovel, and scrape up soil from where
the carcass had been, and put it on top of the carcass, after the diesel
flare has died down, so that the heat can kill any organisms in that soil.
All of this should take about 5 minutes. Watch the fire to make sure it
doesn't spread. We found that it took only 75 minutes to burn a
buzzard-eviscerated white-tailed doe. The Edwards Plateau White-tailed deer
are small, about the size of an adult greyhound. South Texas white-tails
are markedly larger and heavier. I estimate it would take 2 - 2 1/2 hours
to incinerate such a deer with all its organs. Using timber, it would take
half a day or longer. The briquettes cost less than USD 20.
--
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