Any of these stages could be infected with R. rickettsii and transmit Rocky Mountain spotted fever. The tick must be attached for a minimum of 5-20 hours for transmission of R. rickettsii to occur. Since it is transmitted by ticks, most cases of Rocky Mountain spotted fever occur during the tick season from April to September. In the subclinical stage, dogs are infected but do not show outward signs of the disease though they may have laboratory test abnormalities. These dogs may recover quickly.
Some animals develop pneumonia or heart arrhythmias which can lead to sudden death.
These signs appear 2 to 14 days after the tick bite. Some dogs develop ulcerations of the mucous membranes and extremities. Since we need to look for a change in the antibody levels, usually two tests will be done 2 weeks apart and the results compared. Dogs with an active infection will show a significant rise in the amount of antibody present. This test can become positive as early as 4 days after the tick bite.