Rickettsial Infection In Dogs

Dogs who live in tick-infested areas are at risk for Rickettsial infections since ticks are the most common vectors of the diseases. The tick-borne culprits are Rickettsiae or genus of the Rickettsia — tiny bacteria that behave more like viruses than bacteria and are transmitted to dogs through infected tick bites.

Common Rickettsial diseases are Rocky Mountain spotted fever and Ehrlichiosis, in which the bacterium in virus-like fashion invades and inhabits white blood cells while rapidly multiplying. In the process of these diseases, the bacteria destroy the dog's cells causing acute, sub-clinical and chronic stages of the disease.

Engorged Tick
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Overview of Ehrlichiosis and Rocky Mountain spotted fever.

In Ehrlichiosis, the bacteria Ehrlichia canis is the most diagnosed form of Ehrlichiosis and is spread by the brown dog tick. The bacteria Ehrlichia lewinii is spread by the Lone Star tick. Known as a zoonotic disease, Ehrlichiosis is transmissible to humans.

In Rocky Mountain spotted fever (RMSF), the microorganisms transmitted from infected Rocky Mountain wood ticks, American dog ticks, and the brown dog tick attack the dog's blood vessels causing "spots" or areas of hemorrhage. In severe cases, RMSF affects the heart, brain, and kidneys making it a life-threatening and even fatal disease.

Medical form with diagnosis Ehrlichiosis in a hospital.
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Symptoms of the three types of Ehrlichiosis.

Non-specific and vague, the symptoms of Rickettsia infections in diseases such as Ehrlichiosis and Rocky Mountain spotted fever may present few clinical signs of illness. However, in some cases, obvious signs of illness will occur.

In the acute stage, symptoms of Ehrlichiosis, which present from one-to-three weeks after a bite from an infected tick, include:

  • Swollen lymph nodes
  • Weakness
  • Lethargy
  • Depression
  • Lack of appetite
  • Difficulty breathing
  • Fluid build-up in the legs (edema).

In the sub-clinical stage, the bacteria remain in the body without producing any clinical signs of illness for months or even years.

In the chronic stage, symptoms of Ehrlichiosis include:

  • Abnormal bleeding
  • Nosebleed
  • Severe weight loss
  • Fever
  • Respiratory difficulty due to inflammation of the lungs
  • Joint inflammation and obvious pain
  • Seizures may occur
  • Lack of coordination
  • Tilting of the head
  • Eye pain
  • Anemia
  • Kidney failure
  • Paralysis
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Diagnosis of Rickettsial infectious diseases Ehrlichiosis and Rocky Mountain spotted fever.

The diagnosis of Rickettsial infections such as Ehrlichiosis is initiated by your veterinarian gathering pertinent information such as if and when your dog was bitten by a tick, your observation notes concerning the onset of any symptoms and their severity, an overview of your dog's activities and the environment he spends time in, and a review of his medical history.

Exploratory diagnostics include a complete physical examination in which your vet will be looking for signs of hemorrhages within the retina of the eyes, inflammation of the lungs, an enlarged spleen, and inflammation of the brain or spinal cord. If your dog presents with seizures, a lack of coordination, or any nervous symptoms, your vet may take a sample of cerebrospinal fluid (CSF) for further evaluation.

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Preliminary diagnostic steps are followed by standard fluid tests including blood tests such as complete blood count (CBC), biochemistry profile, and urinalysis. Your vet will also need to do Polymerase Chain Reaction (PCR) testing to isolate the DNA of _E. canis_ for a definitive diagnosis. Finally, a test for antibodies of the Ehrlichiosis infection will be conducted.

Treatment for Ehrlichiosis.

Antibiotics are typically used to treat Rickettsia infections such as Ehrlichiosis and Rocky Mountain spotted fever, but must be used as soon as possible after onset.

Rickettsia test
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