Why is this Question-Mark-Shaped Pathogen Hurting Dogs in San Francisco?

Record-breaking rainfall in the San Francisco Bay Area has helped California emerge from the drought that has plagued the state for several years. However, this welcomed downpour has caused an unwelcomed fear in pet owners in San Francisco, Pacifica, Petaluma, Sonoma, Rohnert Park, and across the state. The constant moisture leaves behind puddles of seemingly harmless standing water, which dogs find irresistible! However, these innocuous puddles of standing water are not as safe as they may appear. A unique bacteria called Leptospira can survive in standing water or soil for months and infect dogs upon contact. The most common form of Leptospira is Leptospira interrogans, whose name was inspired by the question mark it resembles due to its characteristic hooked ends. Leptospira causes Leptospirosis, which has already taken the life of multiple dogs in the Bay Area this year.1

Puddle Pointer Pet Animal Water Hunting Dog    3.Leptospira Interrogans Strain RGA 01[2] Copy        2. Dog 1212400 1920 Copy

Dogs can be exposed to Leptospira by drinking or contacting infected water, or through the urine of an infected dog or wild animal. The bacteria will travel throughout the bloodstream and multiply in organs including the kidney, liver, and central nervous system.2,3 A highly infected dog may experience fever, weakness, loss of appetite, and thirst, among other possible symptoms.4 Healthy dogs can naturally produce antibodies to clear some of the bacteria from its system; however, Leptospira will often survive in the kidney long after initial symptoms have disappeared and may continue to be excreted in the urine.2 Leptospirosis can quickly result in kidney failure, which is what caused the Bay Area dogs’ unfortunate deaths.

Leptospirosis, a zoonotic disease, can be transferred from animals to humans. The infection can be transmitted to humans if infected urine or blood penetrates the skin or a mucous membrane, such as the eyes, nose, or mouth. Even a seemingly healthy dog can still transmit Leptospira to its owner through excretion of the kidney-dwelling bacteria. Human-to-human transmission is extremely rare. Humans experiencing Leptospirosis may experience fever, headaches, chills, or muscle aches. 2,4,5

In both humans and dogs, Leptospirosis can be treated with antibiotics such as doxycycline, tetracycline, and penicillin G.2,4 Currently, no vaccine is available for humans in the United States due to the multitude of pathogenic strains of Leptospira. Dogs can be vaccinated to prevent Leptospirosis; however, the vaccine is not 100% effective against all strains of the vaccine. The Centers for Disease Control and Prevention advises getting dogs vaccinated repeatedly throughout their lifetime for best protection. According to the CDC, the simplest way to prevent infection in both pets and humans is to avoid standing water and muddy soil that may be contaminated.

So what can we take away from the premature death of these Bay Area dogs? Leptospira is a real threat, facing not only the bay area but any water-logged environment. However, fear of infection shouldn’t force us to keep our pets locked indoors. Get your pets vaccinated and be aware of your pet’s behavior. Most importantly, be sure to spread the word and inform other pet owners of this microscopic menace.

About the Author:

Alicia Luhrs holds a M.S. in analytical chemistry and is a Research Associate at Emery Pharma.


  1. NBC Bay Area News
  2. Johnson RC. Leptospira. In: Baron S, editor. Medical Microbiology. 4th edition. Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Chapter 35. Available from:
  3. Mohammed H, Nozha C, Hakim K, Abdelaziz F, Rekia B (2011) LEPTOSPIRA: Morphology, Classification and Pathogenesis. J Bacteriol Parasitol 2:120. doi: 10.4172/2155-9597.1000120
  4. Centers for Disease Control and Prevention (CDC).

Image: Protein Abundance Database:


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