Page 792 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

Botulinum Neurotoxins Chapter | 55 751

VetBooks.ir organ tissues, milk, or feedstuffs. Due to the relatively that any bird carcasses are removed prior to spreading on
pasture, that cattle are withheld from grazing for at least
slower progression of clinical signs in cattle, diagnostic
21 days after application of poultry litter on to pastures
samples are often obtained long after ingestion of toxin.
Thus, the level of toxin in these samples may have fallen and that poultry litters are not used as cattle feeds.
below the level of detection. Specimens may also be cul-
tured to isolate C. botulinum. An ELISA test has been
Public Health
developed to detect botulinum toxin C and D in cattle;
however, this test is considered less sensitive than the The Food Safety Act of the United States (1990) requires
MBA. ELISA tests for the detection of antibodies to botu- that meat or milk products be withheld from market for a
linum toxins C and D in cattle have also been developed. minimum of 14 days after the onset of the last clinical
Supportive care is the core of therapy for bovine botu- case of botulism in an affected herd (Cobb et al., 2002).
lism, and treatment should only be pursued in standing However, the public health concern for transmission of
cattle. Affected cattle should be kept in confinement to toxins through milk appears to be minimal. No cases of
minimize movement and exertion. Dehydration, electro- human botulism acquired from the consumption of meat
lyte deficiencies, acid base abnormalities, and glucose or milk from botulism-affected cattle have been reported;
deficiencies should be managed with fluid therapy. Fluids furthermore, it does not appear that calves acquire botu-
can be administered orally (via an orogastric tube) or IV. lism through nursing from affected cows. Only a single
Mineral oil or sodium sulfate can be administered with study to date has been able to detect toxins in milk from a
care as cathartics to treat ileus; however, magnesium sul- dairy cow affected with botulism (Bo ¨hnel et al., 2005). In
fate should be avoided because it may potentiate muscle this study, botulinum toxin serotype B was isolated in
weakness. Rumen transfaunation may also be performed. milk collected from one udder quarter that was simulta-
Alfalfa gruels may be administered via an orogastric tube neously affected with mastitis. The toxin concentration in
4
to maintain caloric intake. Equine origin polyvalent anti- the milk was determined to be approximately 10 MU.
However, the milk did not test positive for C. botulinum
serum may be administered to cattle. However, antitoxin
bacteria. It is likely that the concurrent mastitis infection
therapy may be less efficacious in cattle because most of
enhanced the passage of the rather large toxin protein
the toxin will have been internalized into the neuron or
(150 kDa) across the normally protective blood:milk bar-
degraded by the time the diagnosis is made. Antibiotics
rier by altering its permeability. This is supported by a
may be administered for secondary complications such as
much earlier report from Moberg and Sugiyama (1980),
aspiration pneumonia; as in horses, those that produce
who isolated botulinum toxin in milk using an infected rat
muscle weakness should be avoided.
model. Other studies have not been able to detect the tox-
ins in milk from affected cows using either ELISA or
Prevention mouse bioassay techniques (Galey et al., 2000; Cobb
et al., 2002; Moeller et al., 2003). Regardless, the pasteur-
Although toxoid vaccinations for serotypes B, C, and D
ization process would likely denature any toxin protein
are the mainstay of treatment in many countries, there are
that was able to pass into milk, reducing the risk to the
no U.S. Food and Drug Administration-approved vaccina-
consumer. Note, however, that the potential for botulinum
tions for cattle in the United States. Animal carcasses
toxin contamination of milk may be more relevant in
should either be buried, or burnt and buried, or fenced off
regions where unpasteurized milk is available for public
so that cattle are unable to access the burial area. This
consumption.
will also reduce the risk of a botulism outbreak if cattle
were to chew on carrion or bones.
Other important preventative measures include: pro- Avian Botulism
viding nutritional supplements of protein and phosphorus
to reduce bone chewing among rangeland cattle, taking Avian botulism (limberneck, western bird disease) has
care with the harvesting and storage of feeds to reduce been a significant problem worldwide in both domestic and
the possibility of small animals contaminating feeds, wild fowl (Jensen and Price, 1987). The majority of the
checking water sources for organic matter contamination, natural outbreaks of avian botulism have occurred in fowl
and high moisture feeds such as silage or brewer’s grains (Lamana, 1987). Carnivorous, omnivorous, carrion scaven-
when allowed to rot rather than ferment can provide an gers, and insectivorous birds, as well as aquatic bottom-
ideal anaerobic environment for botulism growth. High feeding birds, are all susceptible to botulism. At least 117
mortality incidents have been associated with the use of avian species, including chickens, ducks, turkeys, phea-
mixing wagons for preparing dairy rations. This allowed sants, and ostriches are known to be susceptible. Carrion
the toxin to be evenly distributed throughout the mix. eating birds such as vultures are reputedly less sensitive to
Since poultry litter is used as fertilizer on many farms the toxins, possibly because healthy birds often have anti-
it is important that litter stores are not accessible to cattle, bodies to the toxins (Ohishi et al., 1979). Although broiler