Fleas are not only pesky critters that can drive your dog crazy, they can also carry secondary diseases that can harm your dog’s health and potentially your health as well. Managing them can be a challenge too, so to help you maintain your dog's overall wellbeing, understanding the most common flea-related diseases in dogs and knowing how to treat them are vitally important.
Flea bite allergies
For dogs that have an allergy to flea saliva, even one flea can send your dog into a scratching and chewing frenzy. Signs of flea bite allergy in dogs include excessive itching, scratching and chewing — sometimes severe enough to cause localised hair loss, redness and local oozing skin infections. You must watch out for this, as dogs with a flea bite allergy can cause significant damage to their skin in minutes. They will typically chew their hind end right above, or to the side, of their tail. Additionally, they can scratch the sides of their faces enough to cause local ‘hot spots’: skin that is red, raw, oozing and infected.
Hot spots caused by fleas are typically treated on an outpatient basis. Your veterinarian will clip the affected area, clean it with an antibacterial solution and subsequently apply a medicated ointment. The most important aspect of treating flea bite ‘hot spots’ is to stop the itch and eliminate the bacterial infection. Most commonly, this is accomplished with a steroid injection and antibiotics, however newer treatments, including oclacitinib, may be prescribed instead, as oclacitinib can stop the itching without the negative side effects often associated with steroids. Your veterinarian may also prescribe an Elizabethan collar to stop the dog from chewing on themselves.
What about diseases?
Fleas are known to harbour diseases that range from severe to mild. Fleas can carry plague, typhus, tapeworms and bartonella (the cause of cat-scratch fever). Each of these diseases can be transmitted to dogs and can also be contagious to humans.
Signs of typhus can include fever, headaches and a rash. It’s generally diagnosed by blood work, and treated with supportive therapy (IV fluids) if the animal is dehydrated, as well as antibiotic therapy with doxycycline or minocycline.
An infestation of tapeworms can cause weight loss if severe enough and tapeworm segments that look like grains of rice may be noted in the stool or around the dog’s anus. They’re easily killed with a dose of praziquantel. What's more, tapeworm segments are not infectious to humans or other dogs. Tapeworms require fleas as part of their life cycle: a dog or human must ingest a flea infected with tapeworms in order to acquire a tapeworm infestation.
Bartonella, bacteria carried by fleas, can cause cat scratch fever. Signs of cat scratch fever include loss of energy, swollen lymph nodes, aching joints, neurological abnormalities, rashes and fever. Like typhus, Bartonella is diagnosed through blood work and is treated with supportive care and antibiotics.
Bubonic plague is caused by bacteria called Yersinia pestis and is very serious in dogs. It’s carried by wild rodents: squirrels, mice, rats and prairie dogs, for example. It is very rare in dogs because they tend to be immune to plague, however, it can cause painful swollen lymph nodes, fever, inflammation, depression, vomiting, dehydration, diarrhoea, enlarged tonsils and severe weight loss.
The head and neck area will swell considerably and a dog’s lymph nodes may abscess and then rupture and drain. Should the dog contract plague, it’s often fatal. You can, however, treat it with antibiotics and supportive care, although dogs with plague typically need to be hospitalized. In certain countries, plague is considered a reportable disease and if a dog has been infected with plague, care must be taken to not come into contact with any fleas or bodily fluids from the animal.
While tapeworms are generally not considered an emergency situation, these other flea-borne diseases are considered emergencies and of significant concern to human health. If you see any of these symptoms, take your dog to the veterinarian as soon as possible.
For all of the conditions discussed, removal of fleas from your dog is an important part of therapy as well. There are many products available that will kill and prevent flea infestations on your dog and in your home. When you’re treating fleas, it is important to treat the infected animal and all other cats and dogs in your home. It’s also crucial to check your home for flea eggs, larvae and pupae, as fleas hatch in the environment, not on pets. A reputable pest control agency can help you determine if you have fleas in your environment and a veterinarian can advise you on the best flea treatments for your pets. Never apply flea treatments that are licensed for dog-use on a cat as this can cause serious side effects and be cautious with over-the-counter flea products containing permethrins, as many animals are sensitive to them.
Author info: Sarah Wooten is a small animal veterinarian and certified veterinary journalist. She is a 2002 graduate of the prestigious School of Veterinary Medicine at University of California in Davis. She practices in Greeley, Colorado part time at Sheep Draw Veterinary Hospital and writes for multiple online and print publications.