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Botulism as likely cause of paralysis and death

Unusual presentation:

Ongoing, unexplained deaths in disease investigations from two independent practices.

CASE A: Twelve of 370 brahman bullocks die over several weeks.

Time and location: September 2018, mid-north NT.

Case definition: Two-year old bullocks in good condition, that gradually develop signs over several days of paralysis, inappetence and inability to swallow, then become recumbent and die.

Gross findings: On examination, a downer steer in excellent body condition had no fever (37.7oC), paresis, tongue didn’t retract when pulled out. This steer was euthanased and no abnormalities were seen at autopsy. A field diagnosis of botulism was made on basis of clinical signs and history. Bloods, organs, brain, rumen contents, a fresh rib and urine were sent to the laboratory.

Laboratory findings: No haemoparasites seen on blood smear. Blood profile showed high neutrophils, low lymphocytes and evidence of dehydration. No abnormalities were seen on histo. Serology was positive for BEF. Bone analysis is pending.

Animal / management / environment risk factors: Many wallabies shot in the paddocks and carcasses left to break down. Cattle have been seen consuming the carcasses, despite being given supplementary feed and having access to Kinofos lick. Half the mob vaccinated with Singvac about one year ago, the others 2 years ago. The steers were given 5-in-1, Dectomax and Multimin injections at the time of vaccination.

Recommendations to the producer: Vaccinate; supplement and hay; and remove shot wallabies from paddock.

CASE B: Sixteen of 600 brahman cows die over several weeks, with deaths increasing from one a month to a few a week.

Time and location: August 2018, northwest NT,

Case definition: Breeder cows in with a body condition score of about 2.5 become lethargic, lie down and die within a couple of days. Deaths occur in one paddock (100 km2) within the vicinity of one particular watering hole.

Disease mapping: Bodies were found around a turkey nest with evidence of predation. The diagram shows a spatial map of the cases.

a map of cases around the turkey nest

Gross findings:  A cow that had been dead for 25 hours was examined. She was about 6.5 months pregnant and her rumen contained fibrous feed typical of northern pastures. The body was too autolysed to collect samples. A differential list based on clinical signs and disease mapping was botulism, water contaminant or plant poisoning (botulism being the most likely). The vet organised for a local stock inspector to autopsy another cow that became sick 2 weeks later.

Laboratory findings:  No abnormalities were noted on histopathology.

Animal / management / environment risk factors: Most of the cows that were put in the paddock remained near a particular waterhole. There were no deaths in mob that had been pushed to a different water hole. The cattle were vaccinated for botulism. No supplement was being given.

Recommendations to the producer: Remove the dead bodies; start supplementation, especially phosphorous; contact vet as soon as see another sick cow; instruct how to take samples; and have bloods taken from other cows.