Rocky Mountain Spotted Fever (RMSF) is a tick-borne bacterial disease commonly seen in dogs and humans that is rarely found in cats.
• RMSF transmission occurs through bites from infected ticks
• Prevalence of RMSF depends on geographic location, with most cases found in temperate climates in North and Central America
• Symptoms of RMSF in cats include poor appetite, weight loss, vomiting, diarrhea, lethargy, fever, and lameness
• Investigation of RMSF involves physical examination, blood work, and diagnostic imaging
• Treatment options include antibiotics alongside supportive care such as fluid therapy
• Prognosis depends on the extent and duration of organ damage
• Mild cases, given prompt treatment, can recover completely
• Severe cases are sometimes fatal or result in conditions such as chronic kidney disease
Rocky Mountain spotted fever is transmitted to cats by infected ticks. The most common ticks that carry RMSF are the American dog tick, the Rocky Mountain wood tick, and, less commonly, the Brown American tick. This limits exposure of RMSF to the geographical location of these ticks, which includes temperate climates in North and South America. In the USA, the most common locations are the southern atlantic states and southern central states. There are pockets of infection in other states such as the Pacific northwest states and Arizona. Only a small minority of cases are found in the Rocky Mountains, despite the name of the disease.
RMSF affects the cells lining the walls of blood vessels, which means the disease can affect all organs in the body. Symptoms vary depending on the body system impacted. Most cases present with lethargy and fever.
RMSF is primarily a canine disease and is very rare in cats.
In addition to geographical distribution, ticks are more active between April and September. Indoor cats are very unlikely to be exposed to ticks.
While rare, RMSF is sometimes a severe condition in cats and suspected cases require prompt veterinary attention.
RMSF results from infection with the bacteria Rickettsia rickettsii, which primarily infects cells in the walls of blood vessels. Transmission of R. rickettsii occurs via tick bites. Not all tick species carry RMSF, and ticks must feed on an infected animal for some time in order to spread the disease.
Symptoms of RMSF vary, but include:
• Poor appetite • Weight loss • Lethargy • Fever
• Swollen lymph nodes • Lameness • Joint pain
• Difficulty breathing • Vomiting • Diarrhea • Seizures
Further investigation of RMSF includes:
• History of tick exposure in an endemic area
• Physical examination
• Blood work
Definitive diagnosis of RMSF involves detection of R. rickettsii on blood or tissue culture.
Treatment options for RMSF include:
• Fluid therapy
• Pain medication
• Blood transfusions
• Treatment of specific symptoms associated with organ infections
R. rickettsii is highly susceptible to antibiotics, and recovery from RMSF is often rapid, particularly with early initiation of treatment.
Cases where treatment is delayed carry a poorer prognosis, due to the effects on multiple organ systems. Long-lasting organ damage is a common outcome, with a minority of cases being fatal.
RMSF is a vector-borne disease where infection requires a bite from an infected tick. Transmission of RMSF between cats (or between species) is not seen.
Prevention of RMSF involves control of exposure to ticks. Effective control requires year-round use of veterinary-approved antiparasitic preparations effective at preventing attachment and feeding of ticks. Other control methods involve:
• Removal of tick habitat around the home such as leaf litter, long grass and large bushes
• Use of fencing to exclude wildlife from the property
• Daily grooming to identify and remove ticks
• Keeping cats indoors to prevent exposure to ticks
RMSF is very rare in cats.
• Fluid therapy
• Treatment of symptoms associated with organ infection
• External parasite control
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