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Potential cat disease increases tick concerns

By Patti Drapala
MSU Ag Communications

MISSISSIPPI STATE -- Mississippi State University veterinarians are urging pet owners to practice effective tick control on cats after the emergence of a fatal feline disease in the state.

Examinations of several domestic cats suffering unexplained deaths in the state and a recent cat patient that died at the MSU College of Veterinary Medicine's Animal Health Center revealed cytauxzoonosis, a parasitic blood infection that is a “death sentence.” 

“The key to protecting your cat is prevention because there is no cure for this disease,” said Dr. Sharon Grace, clinical professor and feline specialist. “Owners need to apply a topical product that will kill ticks that carry the pathogen.”

Grace said the product must contain fipronil for tick control to be effective. People who also have dogs should practice tick control on those pets and examine themselves for ticks as well. The tick that carries the disease, the American dog tick, or Dermacentor variabilis, can hitchhike from dogs or humans to cats, even those that live inside.

“This terrible disease is difficult to diagnose and treat, fatal in most cats, and hard to observe in a patient dying of it,” Grace said. “The goal is to identify the disease early enough so that the veterinarian can humanely euthanize the cat to prevent further suffering.”

A microscopic protozoan (Cytauxzoon felis) causes cytauxzoonosis (pronounced “sy-toe-zo-ono-sis”) when it reproduces within the inside lining of blood vessels and ultimately blocks the flow of blood to vital organs. The organism usually lies dormant in its natural host, which is the bobcat, and causes no health problems in that species.

Cytauxzoon behaves as a pathogen after being ingested by the American dog tick. If the tick picks up the organism from a bobcat and then attaches to a domestic cat for a blood meal, it injects a parasite that quickly becomes virulent in the cat's system. The animal suffers an agonizing death within a short time from the start of the infection, Grace said.

Dr. Mark Russak, a primary care veterinarian at the Animal Health Center, was the clinician on duty when the sick cat was brought in for examination. The cat died less than 24 hours after being admitted.

“Cats are notorious for hiding their symptoms because it is their feline nature to behave in this manner,” Russak said. “They can look perfectly healthy but be gravely ill.”

Cytauxzoonosis runs its course in two phases. In the tissue phase, the pathogen rapidly reproduces within the blood vessels and obstructs blood flow. This process leads to organ death, and the cat goes into shock, which ends its life.

Once the tissue stage concludes, the terminal phase begins as red blood cells rupture and release parasites throughout the cat's bloodstream. At this stage, a blood-smear sample will reveal the parasites on the red blood cells.

Cats usually show symptoms within several days to two weeks of being bitten by a carrier tick. They become depressed and listless, and they refuse to eat and drink. They look jaundiced and have a paleness around their gums, nose and eye tissue.

The most observable sign of the disease is an extreme fever as high as 108 degrees. The sick cat may radiate heat to the touch and loudly vocalize its constant pain.

Even though the American dog tick is a carrier, dogs cannot contract the disease and neither can humans. There also is no threat to other animals such as cattle, horses, birds and wildlife. Infected cats cannot give the disease to other cats.

“The tick has to pick up the pathogen from the bobcat, and the cat has to be bitten by the tick,” Grace said. “This is why tick control is so important for pet owners.”

Cytauxzoonosis, commonly referred to as “bobcat fever” in the Midwest, was first discovered in Missouri and eastern Oklahoma about 1973. The seasonal movement of bobcats and ticks has distributed the disease through much of the South and onward to the eastern seaboard of the United States. There is evidence the disease is also moving north, Grace said.

Symptoms can be confused with those of other feline diseases such as Mycoplasma, toxoplasmosis and feline infectious peritonitis (FIP). Researchers at Oklahoma State University have theorized that the pathogen overwhelms the cat's immune system, and it cannot produce enough antibodies to fight it. Without antibodies, detection with a blood test is not possible.

 

Contact: Dr. Sharon F. Grace (662) 325-3432

Released: August 2, 2007
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