November 1, 2007
Vet Diagnoses Rocky Mountain Spotted Fever in Local Canine
Mention a tick bite and most people are worried about Lyme disease. But one Scotland County family found out there can be worse, after a canine friend was struck by a much rarer disease courtesy of one of the nasty little parasites.
Rocky-Mountain Spotted Fever is not unheard of, but most Missourians are far more familiar with the sister malady, Lyme Disease.
According to the Centers for Disease Control and Prevention (CDC) Rocky Mountain spotted fever (RMSF) is the most severe tick-borne illness in the United States. This disease is caused by infection with the bacterial organism Rickettsia rickettsii.
The organism that causes Rocky Mountain spotted fever is transmitted by the bite of an infected tick. The American dog tick and Rocky Mountain wood tick are the primary transmitters of RMSF bacteria in the United States. The brown dog tick has also been implicated as a vector.
Initially, the dog in question suffered from seizures, leading its owners to seek medical treatment for what was believed to be epilepsy.
But after reading an article in Hounds & Hunting magazine, the owners diagnosed joint stiffness in the dog, which along with seizures are key symptoms of RMSF.
A trip to Lindquist Veterinary Clinic confirmed that the animal had been exposed to RMSF after complete review of the animal’s blood tests.
“We haven’t seen a whole lot of RMSF because the symptoms are fairly vague and a lot of animal owners may not realize their pet needs to be tested,” said Dr. Carla Miller. “I suspect it may be more common than we realize.”
Miller added that while a dog may test positive that doesn’t mean the animal is actually suffering from the disease.
“A lot of dogs may be exposed to it but are not actually diseased,” she said. “It is sort of like when someone has a cold and they sneeze on you. You have been exposed to the sickness, and it is in your body, where you begin to build antibodies to fight it. Sometimes you get diseased and suffer a cold and other times you do not succumb to the symptoms and your body fights it off.”
Miller said the test for RMSF confirms the presence in the blood of the antibodies that are made by the body to fight the disease.
While the outbreak of RMSF is scary thought for animal lovers, it has concerned physicians as well. The Missouri Department of Health issued a public health advisory on June 14 warning about an increase of tick-borne diseases in the state.
The DHSS report was issued following confirmation of a tick-borne disease-related fatality in a Missouri citizen. A northeast Missouri child died May 23, 2007. Diagnostic tests performed at St. Louis Children’s Hospital indicate the child was infected with Ehrlichia chaffeensis, a tick-borne rickettsia that causes human monocytic ehrlichiosis (HME). Missouri Department of Health and Senior Services (DHSS) and local public health disease investigators found that the child had been hospitalized with symptoms consistent with ehrlichiosis after apparently being bitten by a tick. The child died about 10 days after symptoms initially appeared despite intensive medical care.
The DHSS report stated that from January 1 to June 1, 2007, cases of suspected and confirmed tick-borne rickettsial diseases (TBRDs), including ehrlichiosis/anaplasmosis and RMSF, increased in Missouri compared to the previous five years.
The DHSS report revealed increased reports in 2007 of several TBRD, including RMSF. Provisional data showed that 16 cases of ehrlichiosis have been officially reported from January 1 to June 1, 2007, compared to an average of nine cases per year for the same periods of the past five years. In addition, 54 cases of RMSF have been reported from January 1 to June 1, 2007, compared to an average of 22 cases per year for the same periods of the past five years. Other, non-ricketsial, tick-borne diseases reported in Missouri in 2007 include two cases of tularemia and 10 cases of Lyme-like disease. (Some of these reported cases are still under investigation or in various stages of testing.)
Does a confirmed case of RMSF in a canine pose danger for humans? The CDC says “Yes, but not directly. People get this disease when they are bitten by a tick that is carrying the bacterium R. rickettsia. Because ticks on dogs can be infected with R. rickettsii, dogs and people can get Rocky Mountain spotted fever from the same ticks. These ticks can also bite other animals and pass Rocky Mountain spotted fever to them. When you remove ticks from any animal, the crushed tick or its parts can also pass this disease through any cuts or scrapes on your skin.”
The DHSS report warns individuals to beware of symptoms: acute onset of fever, headache, myalgia, and malaise. Nausea, and vomiting may be present in some cases. Severe manifestations of the disease may include prolonged fever, renal failure, adult respiratory distress syndrome, seizures, and/or coma. An estimated 2%-3% of ehrlichiosis patients die from the infection.
In RMSF the initial presenting symptoms are the same as for HME. The rash of RMSF occurs in about 90% of cases and it occurs sooner in the course of the illness, usually 2-4 days after onset of fever. The rash begins on the wrists and ankles. Eventually, the rash spreads to almost the entire body, including the palms and soles, but sparing the face.