Case report

Clostridium botulinum

in a bachelor herd of elephants

Date: 2017

Place:Spain (zoo)

History

A group of 6 juvenile Asian elephants had been kept under Mediterranean climate conditions for several years without major disease issues. During springtime, 5 out of these 6 elephants fell ill within 1 week and died days after showing first signs of illness. The major clinical signs consisted of gradually increasing general weakness, shivering, mild salivation, inability to stand and proper use of the trunk. Three of the affected elephants died within 3 days after onset of clinical signs. The other 2 elephants were humanely euthanized as there were unable to stand up.

The animals were fed ryegrass silage, grass and pellets. Clean drinking water was available, but the animals had also access to pools with water of questionable quality.

The only unaffected elephant was the subordinate animal in the group, having less access to favorite food items.

Blood parameters were within normal ranges.

Several zebras that were kept in another part of the zoo showed neurological symptoms (shivering, shaking, paresis, inability to stand) and some of them had died too. 

One of the affected elephants leaning against the wall in the early stage of the disease.

Zebra at the same zoo in the same period suffering of ataxia, trembling and paresis after feeding on ryegrass silage contaminated with Clostridium botulinum.

Paralytic Asian elephant in lateral recumbancy, unable to bring food items into its mouth after feeding on ryegrass silage contaminated with Clostridium botulinum

Treatment

Symptomatic treatment was given in the form antibiotics, IV infusions and rectal water administration.

The diagnose could only be made several days after necropsy, as the toxicology samples had to be sent abroad.  

Diagnostic results

Necropsy results:
Multifocal hemorrhages, edema in the heart. No evidence of virus infection. No pathogenic bacteria found.

Toxicological examination of the silage revealed the presence of vomitoxin and zearalenor (see below). 

​Toxicology results:

Silage:

  • Sulphite reducing Clostridium: 800 cfu/gr

  • Vomitoxin: pos.

  • Aphlatoxin: neg.

  • Fumotoxin: neg.

  • Ocratoxin: neg.

  • Zearalenor: low pos.

  • Toxin T2: neg

Stomach and intestinal content:

Clostridium botulinum toxin found in stomach contents of elephants and zebras and silage (mouse bio-assay)

Subtyping of the strain was not performed.