The Case of the Downer Horses

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PREVENTING AND TREATING TETANUS

In general, horses, goats and sheep are more susceptible to tetanus than cattle (dogs and cats rarely get it) and they should be given an annual injection of a tetanus toxoid. Whenever animals suffer a skin wound (including punctures or sole abscesses), a booster injection is necessary. Also, if any medical procedures such as castration or tail-docking are needed, they must be done using good sterile technique.

In horses, the tetanus toxoid is usually combined with other yearly vaccines, such as equine encephalitis and rhinopneumonitis. In ruminants, the toxoid is combined with Clostridial C and D vaccines, which also prevents a potentially devastating intestinal toxemia.

When Dr. Sandigo discovered the stricken lamb, he isolated it in a dark stall to minimize external stimulus and immediately vaccinated it with the tetanus toxoid. After administering an appropriate dose of antitoxin he proceeded to clean up the infected stump where the tail had been docked. Finally, he injected a hefty dose of penicillin.

Aside from bacterial infection in the spine and brain, animals can lose control of the muscles around the mouth (better known as lockjaw) and die of malnutrition. The owner of the infected lamb would feed the animal a high-calorie gruel through a stomach tube that he had fashioned from a section of garden hose.

While Dr. Sandigo recognized similar symptoms in the stricken horses, he feared that botulism was the cause of their demise. What puzzled him was that if all four horses had succumbed to botulism in four separate locations, where had they contracted the disease?

BOTULISM AND THE CASE OF THE DOWNER HORSES

Driving through the sheep pastures and dry washes of Arroyo Hondo about three miles from the last infected horse, Dr. Sandigo passed a group of crows and ravens that had stopped to feast on some carrion. A crude burial pit of dead cattle, horses and other animals was now exposed, revealing hide, hair and bone fragments. Recent rains eroded the meager layer of soil covering the animal corpses, and the scavengers pecked relentlessly at the carcasses. Could this be the source of the Clostridium botulinum?

Dr. Sandigo obtained a fecal sample from one of the horses and mapped the locations of the other dead ones. Sure enough, the burial pit was equidistant from each of the farms. But unless each of the horses had come into contact with the area or with each other, thought Dr. Sandigo, how could they have contracted the same disease? Somewhere in the vicinity of the four farms there was a shared source of the botulism toxin that must have been in the feed source, in the water supply... or spread by another carrier.

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