Aeromonas hydrophila bacteria not ruled out as Alabama Rot cause has covered reports about Aeromonas hydrophila here, here and here. Vet Fiona Macdonald hypotheis is that Aeromonas hydrophila bacteria may be a factor in triggering Alabama Rot when conditions are rainy and cold.

The Vet Times report:

Specialist vet studies bacteria cause of Alabama rot Vet Fiona Macdonald is researching whether Aeromonas hydrophila is a link to identifying cause of deadly canine disease. A specialist fish vet is investigating an organism described as “a possible stepping stone” to identifying the cause of one of the UK’s most baffling and lethal canine diseases.

Fish vet Fiona Macdonald is researching whether Aeromonas hydrophila, a heterotrophic, Gram-negative, rod-shaped bacterium, present in water sources and soil, might be involved in the aetiology of CRGV.

In a document sent to Veterinary Times entitled “CRGV (Alabama rot) – an organism of interest?”, Dr Macdonald explained: “There is a suspicion initial cases of CRGV occurred in areas with substantial amounts of water as a result of unusually high rainfall; both running and standing water was close to 4°C for some weeks around the time of the cases.

“To date, dogs appear to be the only species affected, with no reported cases in wild ponies, foxes, cattle or deer. There have been recorded cases of infection with A hydrophila in dogs, which mirrored Leptospira infections, and this pathogen has been on the list of possible causes of CRGV since early manifestations of the problem.”

Dr Macdonald is receiving funding for her work from the New Forest Dog Owners Group, and is appealing for help from UK vets.

She said: “I want blood samples from suspected CRGV cases and I’m happy to send out swabs along with a sampling protocol to any vet for them to swab any suspicious lesions. Email me at”

David Walker, from Anderson Moores Veterinary Specialists, and the UK’s leading authority on CRGV, said: “It’s a nice piece of work… I’m hoping she publishes because it’s a possible stepping stone for either her, or others, to take on the work and truly include or exclude this organism in the Alabama rot investigation.””

The International Animal Health Journal (1) said:

“A bacterium that causes ulcerative skin lesions and kidney failure in fish could be linked to cases of Alabama rot in UK dogs, current research suggests.

Fish vet Dr Fiona Macdonald is co-ordinating a study into whetherAeromonas hydrophila could be a possible cause of cutaneous and renal glomerular vasculopathy (CRGV), also known as Alabama rot.”

The cause is not known yet…

“While the cause is not yet known, it appears to have a seasonal aspect, with most cases occurring between November and June. Initial cases occurred in areas with substantial amounts of water, as a result of unusually high rainfall, during cold weather. Both running water and standing water were 4ºC for some weeks at the time of the cases.”

Does A hydrophila grow in skin lesions causing Alabama Rot?

“A hydrophila was first recorded in dogs in 1995. It is known to cause ulcerative skin lesions in both ornamental and farmed fish, with subsequent kidney failure. The UK strains prefer cold, which could be why it grows in the skin lesions – as they are cooler than the rest of the body.”

A test for A hydrophila antibodies

“Diagnostic laboratory BioBest, in Edinburgh, developed a specific test for A hydrophila antibodies in serum. Dr Macdonald says a significant number of blood samples submitted from suspected CRGV cases, strongly indicated an immune response to the organism. The samples came from dogs living in rural areas across the UK, from southern Scotland to Devon.”

But the evidence for A hydrophila is weak with only one case

“Specialist transport medium swabs have also been sourced to sample skin lesions on first presentation to a veterinary surgeon. These are subjected to specific culture conditions for Aeromonads. So far, Dr Macdonald says there has been only one positive isolation of the organism from a swab taken from a suspect lesion. This dog also produced a positive antibody response to the organism.”

Research thus far has also involved testing canine kidney cells in tissue culture to determine if there are any effects associated with the A hydrophila. Dr Macdonald says the theory is that toxins from the organisms cause kidney problems in affected dogs, rather than direct infection by the organism itself. This could explain why the organism has never been isolated so far in affected dog kidneys.

Results show that both the medium in which the organism has been grown, and the inactivated organism, killed the dog kidney cells in tissue culture – even after significant dilution. Dr Macdonald says this goes a long way to confirming the involvement of bacterial toxins.

Going forward, the project needs many more samples to draw firm conclusions, but the early results have been described as ‘very promising’.


  1. 1) International Animal Health Journal (accessed 30th January 2018)

One Reply to “Aeromonas hydrophila bacteria not ruled out as Alabama Rot cause”

  1. I doubt it. If you take any notice of Wikipedia (some say you should not):

    Aeromonas hydrophila is…mainly found in areas with a **warm** climate (asterisks mine).

    What seems unlikely is not that the strain might destroy a dog’s kidneys without going anywhere near them (none were found in the kidneys), not that it survives and even thrive in this predominantly cool or cold climate, or even that it would have to jump from fish to dogs. The most dubious postulation is that a heat-loving organism would be at its most potent here when the weather here is at its coldest. I don’t see anything above that addresses this contradiction.

    I am amazed at the attention these seemingly unlikely causes are receiving when the dogs’ tissues do not appear to have been screened for all possible contaminants – radiation and whatever else that offer a perfectly reasonable explanation for both the symptoms and the seasonality of CRGV.

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