
Never let your dog swim in water with obvious toxic algae bloom. By: pet1
Dangers in the Water
What bugs could be lurking in less-than-fresh water? Quite a few, as it happens.
1. Giardia
This single-celled parasite may be better known to you as “traveler’s diarrhea.” (Yes, it can infect people too, not just pets.)
Giardia is shed in feces inside a hardy oocyst. The latter is tough and can survive for long periods of time in warm, humid conditions and thrives in water. When a dog drinks infected water, the parasite passes into their gut. Some dogs show no symptoms, but others can develop sickness and weight loss in addition to diarrhea.
A diagnosis is made by examining a fecal sample under the microscope. Most cases respond well to a 3- to 10-day course of fenbendazole (Panacur) or metronidazole.
2. Cryptosporidium
Cryptosporidium is similar to giardia but a whole lot tougher. Indeed, cryptosporidium is so tough that it can survive chlorine treatment. Similar to giardia, oocysts are passed in feces that, if they get into water, are a source of infection for animals and birds.
Again, the treatment is fenbendazole or metronidazole to kill the parasite in the gut. Also, bathe and shampoo the dog on the last day of treatment to wash away any oocysts clinging to the coat. Not doing so risks reinfection should the dog lick their fur.

If your pet is ailing after a swim, don’t wait — see the vet immediately. By: Pixabay
3. Leptospirosis
Leptospirosis is a particularly nasty infection with the potential to kill. It’s also a devious infection because signs can range from mild stomach upsets that last for weeks to months to acute liver and kidney failure that are fatal in hours.
Other symptoms include:
- Fever
- Muscle weakness
- Blood in the urine
- Loss of appetite
- Vomiting
- Diarrhea
- Collapse due to organ failure
Leptospirosis can be spread by rat urine and especially loves water sources such as standing water, puddles and bird baths. The unpredictable nature of leptospirosis means prevention is the best policy. Happily, there are vaccines available. If you live in a risk area for lepto, then your vet will advise giving the vaccine.
A word of caution, though: The vaccine must be given yearly, as immunity is often gone completely 12 months after the previous dose. Oh, and pets can pass lepto to people. If your dog shows similar symptoms to those above and you feel unwell, see your physician as a matter of urgency.
4. Blue-Green Algae
You may be aware that dogs shouldn’t swim in water with an obvious algal bloom, but do you know why?
Cyanobacteria, also known as blue-green algae, are a toxin-producing form of bacteria. This toxin can affect any mammal (including people), causing nerve and liver damage. Signs of toxicity include:
- Weakness
- Muscle tremors
- Drooling
- Vomiting
- Diarrhea
- Breathing difficulties
- Collapse and death
There is no antidote to blue-green algae poising. Treatment includes rinsing out the stomach to remove contamination and supportive care with intravenous fluids.
So don’t let your dog swim in dirty water or drink from containers of “old” water — give them the fresh stuff.