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Bacterial Infection (Tularemia) in Dogs

Francisella tularensis in Dogs

Tularemia, a zoonotic bacterial illness occasionally observed in dogs, is linked with various animal species, including humans. It can be contracted through contact with infected animals, earning it the moniker “rabbit fever” due to its primary transmission route. While capable of infecting multiple animal types, the bacteria can also spread through contaminated water or contact with infected soil, where it remains infectious for months.

Infection often occurs when dogs ingest tissues from infected mammals during hunting, encounter contaminated water sources, or through bites from ticks, mites, fleas, or mosquitoes, all capable of carrying and transmitting the bacteria. The bacterium can also enter a dog’s system through the skin, airways, eyes, or gastrointestinal tract.

Tularemia is prevalent across much of the world, including continental Europe, Japan, China, and the former Soviet Union. In the United States, it is most frequently reported in Arkansas and Missouri but can be found in many regions nationwide. Seasonally, the risk increases notably from May to August and during the winter rabbit hunting season in areas where it’s common.

Ticks, such as the American dog tick, Lone Star tick, and Rocky Mountain wood tick, are among the primary vectors for transmitting F. tularensis, along with other types of ticks.

Symptoms and Types

  • Abrupt onset of fever
  • Fatigue
  • Dehydration
  • Loss of appetite (anorexia)
  • Swelling of the lymph nodes
  • Tender abdomen
  • Enlargement of the spleen or liver
  • White patches or sores on the tongue
  • Jaundice, possibly characterized by yellowing of the eyes

Causes

  • Bacterial infection (Francisella)
  • Contact with an infected source

Diagnosis

To accurately diagnose your dog’s condition, provide your veterinarian with a detailed history of its health and recent activities, including boarding, outings, trips, tick encounters, and interactions with other animals or pests.

Your veterinarian will conduct a thorough physical examination of your dog. Standard laboratory tests will encompass a blood chemical profile, complete blood count, electrolyte panel, and urinalysis. While the presence of F. tularensis may not always be indicated, the complete blood count might reveal an elevated white blood cell count (WBCs). Platelet levels (thrombocytopenia), crucial for blood clotting, could also be lower than normal.

The biochemical profile might detect elevated bilirubin levels (hyperbilirubinemia) and decreased sodium and glucose levels in the blood. Elevated bilirubin levels, an orange-yellow pigment found in bile, may suggest liver damage, often accompanied by jaundice symptoms. Additionally, the urinalysis might reveal heightened bilirubin and blood levels in the urine.

Your veterinarian might seek assistance from a specialized laboratory service for a definitive diagnosis. In cases where the diagnosis isn’t straightforward, samples may need to be collected and sent for culture testing, involving controlled growth in a laboratory setting to identify the causative organism.

Advanced molecular techniques like polymerase chain reaction (PCR), which detects the presence of disease based on genetic code, are accessible in reference laboratories. Microbiologists need to be notified when tularemia is suspected because F. tularensis necessitates special media for cultivation, such as buffered charcoal and yeast extract (BCYE). Routine culture media cannot isolate it due to the requirement for sulfhydryl group donors like cysteine. Serological tests, which detect antibodies in the patients’ serum, are also available and commonly utilized. However, cross-reactivity with brucella may complicate result interpretation, underscoring the importance of not relying solely on serology for diagnosis.

Treatment

Timely intervention is crucial for effectively resolving and curing the symptoms. Patients not receiving early treatment often face a high risk of mortality. Your veterinarian will administer antibiotics to manage the infection and associated symptoms. Your dog might require antibiotic therapy for several days to ensure complete alleviation of the symptoms.

Living and Management

The overall prognosis is bleak, particularly for animals not promptly treated at the onset of the disease.

As mentioned earlier, F. tularensis is a zoonotic infection, capable of transmission between different species. If your dog contracts this bacterium, you must take special precautions to shield yourself from infection. The bacteria typically enter the body through compromised skin and mucous membranes or via inhalation. Humans are most commonly infected through tick bites or by handling an infected animal. Tularemia can also be contracted through inhalation, with instances reported during dog grooming and among hunters who may inhale bacteria during skinning. Ingesting contaminated water, soil, or food can also lead to infection. Additionally, there have been cases where inhalation of particles from an infected rabbit or other small rodent, such as those ground up by a lawnmower, led to infection.

F. tularensis is an intracellular bacterium, capable of parasitizing host cells. It primarily targets macrophages, a type of white blood cell, thus evading the immune system’s efforts to eliminate it. The progression of the disease hinges on the organism’s ability to spread to various organ systems, including the lungs, liver, spleen, and lymphatic system.

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