Infectious Diseases of Dogs


Canine Influenza

Canine influenza has been in the news lately. At the present time this appears to be an adaptation of equine influenza that can infect dogs and spread from one dog to another. It has been seen in Florida, Wisconsin and New York, so the odds are good that it has spread widely in the U.S. at this time or that it will soon. In most dogs it is a mild upper respiratory virus that may be associated with a fever and nasal discharge. In more severely affected dogs there can be high fevers and signs of pneumonia, such as difficulty breathing.  Canine influenza can be fatal. The current estimate is that 1 to 5% of dogs infected with canine influenza virus will die from complications of the infection

In as situation somewhat similar to cats with upper respiratory viral infections there is a need to use antibiotic therapy when dogs have influenza virus. Even though antibiotics do not kill viruses or even weaken them in most cases, certain viruses are more likely to be accompanied by secondary bacterial infections. This is especially true of infections affecting the upper respiratory system. So if your vet suspects canine influenza it is likely that antibiotics will be administered even though this is a viral infection rather than a bacterial infection.

This infection is a low risk to individual dogs in private households but is a bigger risk where dogs congregate, such as dog shows, shelters and kennels. There is no preventative vaccine at the present time but it is likely that vaccine companies are already hard at work coming up with a vaccine. Treatment is supportive since antiviral medications have not been widely used in dogs and it is not known if they would be helpful or harmful. It is unusual for influenza virus to jump from one species to another and then to be contagious among members of the new species.  This is the scenario that worries human public health officials over bird flu but there is no evidence currently of any risk to people from this new canine influenza outbreak.

Most dogs suspected of having influenza at the present time will turn out to have something else, such as Bordetella infections ( one cause of kennel cough). Despite this it is worthwhile to keep in mind the possibility that this viral infection may be present and to keep your dog home from obedience classes, kennels or other areas that dogs congregate until your dog is completely recovered. This may take several days.

If you have the need to confirm this infection  it is possible to test for this virus. Cornell University’s diagnostic lab has testing information. The URL for their site is

Dr Mike Richards, DVM

The AVMA updates their Canine influenza page as the CDC and Cornell provide data as the Flu spreads and is confirmed in different states. Please check that page for the latest updates as well.  

Leptospirosis (Zoonotic)

Q:  I don't understand what Leptospirosis is so this article is not clear for me. Can you tell me what it is?

Fort Dodge Animal Health has updated its Duramune line of vaccines to include the serovars (types) of leptospirosis that have been incriminated in most of the recent outbreaks. If you live in an area in which leptospirosis is a concern (the latest outbreaks were on Long Island and in California), it would be worthwhile to ask your vet if vaccination with these new vaccines would be prudent. These vaccines are manufactured using "sub-unit" technology that should help reduce reactions to the vaccines, which has previously been a problem with leptospirosis vaccinations. The two serovars added to the vaccine are grippotyphosa and pomona.    

A: Your question is a good one. In one of the older issues of the VetInfo Digest, available in the subscriber area (October 1998), this article explains leptospirosis:


Leptospirosis is a hot topic at dog shows and other competitions now. There has been an epidemic of leptospirosis in Long Island, NY now for a couple of years. It seems like there is an upward trend in the number of diagnosed cases across the country, although that isn’t certain since no one really keeps statistics on the number of cases of diseases in dogs and cats. This has occurred concurrently with recognition among veterinarians that leptospirosis is the portion of the combined canine vaccines that is most likely to cause reactions. So many vets are not vaccinating for this disease. That sounds pretty bad but the new cases of leptospirosis being reported are from Leptospirosis species that the vaccines do not protect against. At present there is no vaccine for the two strains causing most of the current problems, L. grippotyhosa and L. pomona. A third type (serovar) of Leptospira, L. bratislava is reported to be on the rise as well.

Leptospirosis is a water-borne bacteria. It is spread most commonly by contamination of water sources by infected urine of wildlife and domestic animals. It can live in the environment long enough to spread effectively. Leptospirosis is most commonly associated with kidney disease but some of the strains of the organism can cause liver damage, induce bleeding disorders, cause neurologic signs or uveitis (eye inflammation).

Leptospirosis is difficult to diagnose with certainty because the organism doesn’t grow well in cultures. Serum titers are useful in making a diagnosis but it often takes paired samples to demonstrate a rise in titer. In the meantime, it is important to treat for the organism to try to limit the damage that it does. Leptospirosis organisms are susceptible to penicillins, which should be used for at least two weeks if infection is suspected. It is also important to treat for any damage that is occurring to organs and to control any developing bleeding disorders. Kidney damage and bleeding disorders often require very aggressive treatment in order to achieve a successful outcome so this is a situation in which long-term hospitalization may be appropriate and necessary.

Leptospirosis is especially scary because the bacteria can infect humans. It is important to observe good rules of hygiene, such as hand washing after handling the pet and even wearing latex or vinyl gloves when cleaning up urine or other body fluids. Pets suspected of having this illness should be quarantined from contact with other pets or any household members incapable of maintaining good hygienic practices.

People who own pets that congregate in spots such as parks, dog shows, sporting  competitions and other events should be careful about exposing their pets to places where water may be contaminated with urine or where there may be enough urine contamination to pose a risk. This can be very difficult to manage. It would be nice if there were an effective vaccine for the current crop of leptospirosis infections but there is not. If the older strains of this disease begin to reappear as vaccinations are no longer given it may be necessary to reconsider the risk/benefit ratio of those vaccines as well.

It is very likely that one of the vaccine manufacturers is working on a new leptospirosis vaccination but I have no way of knowing whether that is the case. It would be worthwhile to check with your vet occasionally to see if there is a vaccination available if your pet fits the "high risk" profile of a dog or cat that is exposed to potentially contaminated water sources or is frequently in contact with large numbers of pets from all over the country.

All in all, leptospirosis is still pretty rare. It is still a good idea to consider it whenever kidney disease occurs in a young to middle aged pet or when uveitis (ocular inflammation) occurs for no known reason.

The new vaccines do protect against the two strains causing most of the recently recognized cases of leptospirosis.

Leptospirosis should also be considered when signs of liver disease are present. Due to the water-borne nature of this bacteria, it is especially important to remember it as a cause of problems after flooding or extraordinarily heavy rains.

Hope this clears things up a little.

Mike Richards, DVM

Rabies Transmission

Q: Been meaning to ask this question: I did read your paper on Rabies & remember the time frame for the bite transference, but is it possible to transfer the virus via salvia without a bite? I.E. two animals hissing at each other? And left behind in salvia on something such as a dish or rug or concrete? If so, how long does the virus live on these items?

I live in a semi-wooded area full of darling, displaced raccoons, possum and fox, and many others. (housing construction.....damn the developer to hell anyway for not giving one single bit of consideration to the animals!).

My boys are strictly house-bound, but I do like to let them out on the porch for air and sun.

When you have time...........thanks so much!

Best Regards, Lyn

A: Lyn-

It is possible to transmit rabies through saliva entering a pre-existing wound. There are rare cases in which the virus is aerosolized and enters wounds, as well. I know this has happened at least once in a laboratory. However, the risk of rabies transference in either of these cases is pretty low, since it circumstances have to be just right. Rabies virus does not survive outside the body for more than few seconds, in most cases. If an animal dies of rabies, the rabies virus may survive for up to two days in the body, though. This is a good reason to keep pets away from dead raccoons, opossums, ground hogs, etc.

There has not been a case of rabies, with the currently available vaccines, in a properly vaccinated pet. I am hoping that record is never broken.

I think your guys are safe from rabies. We have seen some nasty bite wounds from raccoons, though. So do continue to be cautious, as you have been.

Mike Richards, DVM

Rabies Information in Virginia  -Possible Infection from Pet

Q: Hi, I recently lost my 15mo. old Scottish Fold. I rose to find he had been sick all night & vomited repeatedly through out the house. He would try to drink & immediately bring it back up. I rushed him to the vet. The vet could not find anything wrong but gave medication for the vomiting & an antibotic. Vomiting stopped & he seemed okay, eating & playing.

Three days later, I rushed him to the vet with a sudden, severe respiratory problem. Given short & long reacting Cortisone shots & antibotics. I was much more worried than the vet seemed to be because it just seemed so severe. He then hid in a corner and wouldn't move for anything, nor would he take food or water. I stayed by him all night trying to keep my eye on him. At 2am he rose to go to the litter box. I followed. It took him forever & he layed down to go, just the tiniest squirts. He was far too weak for just one day without food & water! Leaving the box, he stumbled & fell. Then I bend down to pet him & barely touched his back & his hind legs slipped out from under him! His eyes were too big, dialated & glossy looking. I rushed him immediately to the vet. A steady body tick developed in his hind legs. Broad spectrum antibotics, anti- inflammatories for throat swelling, etc. with no improvement.

He quit all food & water intake & was on IVs. Later, on one side of face & tail, twitching & started "foaming at the mouth." Vet & 2 universities consulted with, came up with toxoplasmosis or rabies. (Surprise, the previous vet didn't vaccinate for rabies! I had previously quit that office because too busy, confusion & disorganized! Cat raised indoors strickly! Only allowed out in back yard after 1yr old & for short durations. Not exposed to other animals!) Finally, the toxo.test result came back...negative! We had to put him down. Then rabies, negative. His blood work was clear, no evidence of disease in organs or tissue samples. State Health Dept. distroyed brain tissue, in error, that was to go for further testing. The vet now says he doesn't have a clue. If he had to say something, he would say viral meningitis. He does seems to be quite sure it was a virus of some sort. This cat's litter mate has started showing signs of illness but quite different. This cat is choking & gaging during & after eating. He is eating well though & somewhat active. He was started on the broad spectrum antibiotics immediately.


  • Do you think viral meningitis? Zoonotic?
  • Are most viruses zoonotic?
  • The health dept. said to me, "We keep a small frozen tissue sample, for a year, incase someone dies, we can retest." Ahhh! How accurate is this test?!
  • As soon as the toxo. came back negative, I contacted the state health dept., the rabies anti-serum is only available though them. They denied saying it couldn't be rabies, besides if it was I would have months, no rush. How wrong! They wouldn't even listen to how I was exposed! However, to the vet they had a different story & told him he had to put down this animal.
  • Wouldn't it be against state & federal laws to deny the anti-serum under these circumstances?
  • I would be a class III exposure according to the CDC. Who would you contact regarding this?

FYI, Two days after the negative diagnoses, the newspaper headlines were: "Rabid Cat Infects Family" According to the article this area has been under an rabies alert since april. I find myself worring about my daily headaches that have started at this time. They could be tension or stress, I don't know, I don't normally get them but this has been stressful. Karen    

A: Karen- I wish that I could help supply some insight as far as a diagnosis goes but in reading your note I was thinking in such a totally different direction that I think I must have misunderstood part of it. My thoughts were of urinary blockage and pleuritis or other respiratory illness. These almost certainly would have shown up on an autopsy, though. Farther into the letter it did seem more like rabies or toxoplasmosis would be good diagnostic rule-outs. Rabies would be the major zoonotic concern. I can't think of another cat virus that has the potential to infect humans.

There are several tests for rabies but the most commonly used one is the fluorescent antibody test. I could not find specific data on the accuracy of this test but I remember seeing something on this and there was a small margin of error (I think it was about 2%). I can't say this is true everywhere but our health department is pretty careful about any possible case of rabies in which saliva could have contacted an open wound. If you think this is possible I'd call your physician. Again, I can't say this is true everywhere but I don't recall a case in which the health department was not cooperative when a local physician felt that rabies exposure was possible even when testing was negative. I do not recall the health department using rabies serum, though. I only remember a couple of clients being vaccinated with the three or five dose regimens.

The state lab and the local health departments often have differing views on how to handle these cases so if you have only spoken with the state level health department you might want to try your local one.

In Virginia our best reference for rabies information is Dr. Suzanne Jenkins of the state health department. She is considered an expert on rabies and may be a good source of information for your physician or veterinarian. Dr. Deborah Brigss at Kansas State is also supposed to be a leading expert on this disease if you live nearer to Kansas than Virginia.

It may be reassuring to know that of the rabies cases in humans in the United States in the last few years 15 out of 17 cases involved exposure from bats -- only two exposures resulting in rabies occurred from other animal bites. The testing must be pretty accurate if all possible exposures resulted in only two cases of rabies.

I have sweated out this situation personally. I know the anxiety it can cause to be bitten by a potentially rabid animal. Keep working with your vet and your physician to understand the situation fully and to develop an appropriate plan of action.

Mike Richards, DVM       

HIV AIDS- Can Dogs and Cats Get Infected  

Q: I am looking to find some information with regard any truth that cats and dogs are getting HIV AIDS due to used syringes in parks and streets. I have not heard this and am trying to track information to veryify this one way or another.

thank you


A: Angela-

It is always hard to be absolutely certain that there is no truth at all behind a rumor like this. However, there are no reports that I am aware of in the veterinary or the human literature suggesting that either dogs or cats can be infected by the human immunodeficiency virus. Therefore, it seems to be almost impossible that this could be happening.

There is some confusion regarding the difference between human immunodeficiency virus (HIV) and feline immunodeficiency virus (FIV). These are entirely different viruses and there has been no indication in the literature that these strains of virus can cross react. The FIV virus has been used as a model for studying the human infection and this research has been published. One example was the recent "Lessons from the cat: feline immunodeficiency virus as a tool to develop intervention strategies against human immunodeficiency virus type 1",  by Elder et. al, AIDS Res Hum Retroviruses, June 1998. It can be hard for people to accept that such closely related viruses do not cross species lines but that appears to be the case based on studies to date.

If dogs have a retroviral infection similar to HIV it has not been identified. There is some suspicion that they do and a recent paper "Possible relationships between canine hematopoietic neoplasia, other malignancies and immune mediated diseases" by G. Theilen, in Leukemia April 1997 suggested that there may be an unidentified retrovirus infecting some dogs. However, it has not been suggested that this is human immunodeficiency virus.

Dogs and cats are both being used in studies relating to the control or cure of HIV but these studies do not involve infection of dogs or cats with the HIV virus. They relate to things like immunosuppression of T cells with cyclosporin or similar treatments that are studied in dogs or cats in the hope that the information will apply to human patients who actually are infected with HIV.

You can search for information on HIV at the PubMed site:

I hope this helps to set your mind at ease.

Mike Richards, DVM 

Distemper Possible

Q: I am still at loss what really killed my 9 yrs old dog. I had brought a puppy home from the pound unknowing it had distemper, I found this out on a routine checkup and the 6week pup went into seizures, The vet put her down. Now my other dog who was exposed to this pup <whom I just received from my mom > unknown which shots she received became sick too, I took her to the vet, she was throwing up yellow mucus, not eating and  panting real hard and had discharge from her eyes,, I was convince it was distemper.. my vet after series of test, x-rays  bloodworks, told me he did not think she had distemper  but had heartworms but was not to bad to save. To my surprise. he put her on some antibiotics  for her eyes worming meds for whipworm and hook worm and another anti cephalexin. told me she had some heart damage and lung disease but should be okay,, So I took her home on thurs and brought her back in sat morn cos she was not eating or drinking and panting harder, he did some more test said c cells was OK but he thought she may now have a bateria infection,, he put her on an IV cos she was so dehydrated,, I said  I think she should be put down, he said no  thought we could try and if she was not eating or drinking anything by Mon morn.. we would has to cross that told us to try to get her to eat anything.. I was skeptical.. 5 hrs later she died in my arms.. she was panting so hard I thought she was going to explode. he still can't tell me what killed her. I don't know what to think. Either he was going way out to save her  or to add to his pocket book, I think what I am looking for did she die from heart failure or distemper.

I have another puppy at home who I am scared to death may loose too cos he is too young to have all shots. Is there anything else can kill a dog like this besides distemper or not? My puppy has a runny nose but I was told it has an upper resp cold and is on antibiotics I am wondering am I in for an another cleaning or not??    

A: S-

I think that I would be suspicious of distemper with the clinical signs that you note, but it is not possible to be certain unless an autopsy was done. Distemper is very hard to diagnose with certainty in many cases and it is not that unusual for a dog to die from it before a definite diagnosis can be made. Heartworms can produce severe illness rather suddenly in some cases (when the heartworms cross over into the venous circulation from the liver) and this could have been the problem, as well. There are unfortunately a lot of possibilities.

I wish that I could help more. I hope that the puppy is doing better by now. Sometimes even if distemper is the problem the maternal antibodies will protect a puppy long enough for the distemper virus to be cleared from the environment.  Clean what you can with chlorine bleach diluted about 1:30 to lessen the risk of exposure. Vaccinate the puppy according to your vet's advice. I know that you have had a rough time but perhaps luck will go your way, this time.

Mike Richards, DVM  

Possible Distemper - Possible Zoonotic

Q: Dear Dr. Mike, my family recently rescued a dog from a local animal shelter. About 6-8 days after having the dog, he started with a dry cough (a choking sound). He was seemingly in good spirits, besides a lot of sleeping, he was fine. A day or two later, I noticed a greenish discharge from his nose. I plan on a trip to the vet, but i was hoping for a quick reply from you to end this wondering & worrying. I appreciate your time. Thanks. M-

A: Sometimes I got too much email for quick replies. I hope that you did take your dog to your vet. The symptoms you are seeing could be signs of distemper virus infection, which is serious. I hope it is something less dramatic, like tracheobronchitis, though.

You definitely need your vet's help, though.

Mike Richards, DVM      


Giardia is a protozoan parasite that lives in the intestine of affected animals. It is unclear whether there are several species of this parasite or whether there is one species that affect several different animals, including people. These small parasites are very easy to miss on a fecal exam and may not be present in the stool of animals infected with the organism. Repeated fecal exams are sometimes necessary to identify this parasite. Not all animals in which infection can be demonstrated have clinical signs. This leads some people to believe that the parasite may not cause disease . Most vets think that there may just be other factors, like the animal's immune response to the parasite that cause some animals to develop disease and not others. Clinical signs of giardia include weight loss, inability to gain weight appropriately during growth, diarrhea, vomiting, lack of appetite and greasy appearing stools. Them most commonly used medication for giardia infection is metronidazole (Flagyl). The organisms come from the environment and live in moist to wet areas. They are susceptible to quatenary ammonium disinfectants, Lysol and dilute chlorine bleach. Keeping the dog's environment dry helps a lot.

This disease may be contagious to people from infected dogs so good sanitary practices, like washing your hands after handling an infected puppy, are very important. If a family member develops similar clinical signs, a physician should be consulted.

Mike Richards, DVM


Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...