I was recently called to examine a first-lactation cow that had “gotten caught in between the free-stalls.” The farmers were able to easily free her and she walked to the bedded-pack sick pen. However, they noted she was weak, had a bit of a head tilt and wanted to turn in circles. They administered calcium, thinking she may have milk fever.
The following morning, she was down and had difficulty eating. On my examination, it was obvious that half of her head/face was paralyzed.
Uncommon, but not rare
Neurologic diseases in cows are not uncommon, but they are not something that we see every day. Often, when dairy producers find a cow with neurological signs they assume it is something very severe and elect to euthanize the cow. But, depending on the cause, we can treat quite a few of these cases successfully.
What are the causes?
• Metabolic: Cows can show neurologic signs from diseases that don’t directly relate to the brain. Low magnesium is sometimes seen in conjunction with milk fever. So, the suspicion that this cow could have milk fever was not too far off. Nervous ketosis can also cause neurological signs and is easily treated.
• Infection: Bacterial or viral brain infections are other common causes. Treatment success depends on the exact cause and an early treatment start. For example, Listeriosis is an infection of the brain caused by the bacteria Listeria. If treatment is started early, most cows will survive. Rabies is a deadly viral disease that bears serious consideration because of human implications. Although rare, we must also mention bovine spongiform encephalopathy (BSE).
• Toxins: These are less common in modern dairy operations but botulism, lead poisoning and ingestion of other toxins are additional causes.
Other possible causes include tumors, injury or abscesses.
In these cases, veterinarians use their knowledge of the nervous system to narrow down the search.
Is treatment warranted?
If the prognosis is often poor, why waste money on a vet call? A valid question, but remember that while some of these conditions may appear to be very serious the cow may still be able to recover. The cow in the above example, which was found down, went on to recover completely after treatment.
Another important reason to call the vet is to identify a possible case of rabies. Rabies is an important public health issue. If the cow in the above example had been infected with rabies and died or was euthanized on the farm, then we could have had a possible human exposure to the virus.
Animal welfare is the other aspect of most neurological diseases. If treatment is considered, then it must be carried out with the welfare of the cow in mind. When the prognosis is poor, then a timely decision to euthanize the cow must be made. (Make sure you have non-ambulatory cow and euthanasia protocols on your farm.)
So, even if the prognosis does not look good on your end, at least touch base with your veterinarian for advice, especially when there is rabies in your area or there has been human exposure. It may be a simple metabolic case that can respond quickly to treatment.
Mark J. Thomas is a veterinarian and partner in Countryside Veterinary Clinic, LLP in Lowville, N.Y.