Fungal and Parasitic Infections in Cats



Question: Dear Dr. Richards:

I'm back to you with our old problem, our Siamese cat Mikko's cough. As I previously wrote to you, Prednisone relieved his coughing for a period of time, and we were even able to stop giving him pills for a few weeks. In your reply, you indicated that this would be an ongoing problem and that we would have to go back to giving him prednisone when the coughing re-occurred. You were right, and he started coughing again, and we started giving him a pill every other day, even though we missed a few days a couple of times, we have been treating him about three weeks now. Only it seems that the coughing is getting worse, especially at night, when it is frequent and lasts for long periods of time. Are my husband and I worrying too much, or is there something else we could be doing. Our Mexican vet has no ideas. As usual, your advice will be most welcome. P.

Answer: P. -

Recently, I have become aware of another cause of coughing in cats that may be worth checking out in Mikko's case. The fungal disease cryptococcosis usually causes upper respiratory signs in cats (nasal discharge, sneezing, etc.) but a couple of people have written me recently about their cats with this disorder and these cats had only coughing and weight loss as clinical signs. It is something to consider, especially with the poor response to corticosteroids.

Usually this disease is tested for by examining nasal exudates for the organism but since that isn't possible unless there is a nasal exudate you can do serum testing to see if there is a titer to the organism. If so, it might be worth considering further testing, again. Cryptococcosis might show up on X-rays (actually it probably will but they can be hard to interpret) and the odds of finding it are greater if the X-rays are reviewed by a radiologist.

There is also the possibility that this is asthma but that there is now a secondary bacterial infection. This situation occurs occasionally in asthmatic cats and usually the combination of a corticosteroid and antibiotic will resolve the situation. It doesn't make the asthma go away, so there is still the need for therapy when signs occur in the future.

I'd really think about getting new chest X-rays and possibly looking into serology or other testing for cryptococcosis, if there is any question of a problem on the radiographs.

Mike Richards, DVM 10/22/99


Q: My Mothers cat was diagnosed with Histoplasmosis. What is this disease? What are its signs and symptoms? Will her cat recover from it?---------------------------------

A: Histoplasmosis is a fungal infection caused by Histoplasma capsulatum. Most animals affected by this fungus probably have inapparent or very mild clinical signs and recover without treatment. A few animals have major problems with this organism. This infection can occur almost anywhere but is more prevalent in humid moist areas and is most commonly a problem in the Mississippi and Ohio River areas. The infection primarily affects the lungs and gastrointestinal systems so clinical signs tend to be associated with these sites -- coughing, tiring easily, weight loss, lethargy and diarrhea. Many other signs are possible if the infection spreads to other organs. This is usually diagnosed by transtracheal wash samples from the lungs or biopsy of the intestines. It is usually treated with ketaconazole for a minimum of three months and sometimes longer.

Mike Richards, DVM


Q: Dr. Richards, I have a precious beauty female cat who was adopted by me in 1986 in the Virgins Islands, I brought here with me back to Texas and live on a very large ranch, with cows,pigeons,bats,peacocks,geese, and ducks,goats etc... Last year my cat began limping as if to have distemper, however after three vet visits and lots of blood work I was sent to a feline speclist,who exspatated (?) her rear lymp notes,and found that she did indeed has histo, I treated here with human spronax n the am and pm for 6months!!! It is my understanding that I have only put this disease into remisson,and that the longest remisson has only been 2 years. It has been about that long now,but have had lung xrays and there is no sign yet of it returning. I would lke to know your thoughts, I have been told that she probably picked this up from some pigeon or bat dropping,whiich she licked off her paws, and that it may be in the soil, I have not brought amy new pets into my home. My cat is a Ragdoll (siamese) and is probably about 14 yrs old.

Thank You Very Much for your time. Debbie

A: Debbie-

Histoplasmosis is relatively uncommon but is reported more frequently in cats than in dogs. I have no experience treating this disease but the cure rate in at least one study by Dr Clinkenbeard and associates reported in the Compendium on Continuing Education in October of 1989 suggested that the cure rate was about 33% and the newer antifungal agents seem to be even a little better based on my impression of correspondence on the Veterinary Information Network. Histoplasmosis is supposed to more common in young cats than in older ones so I guess there would be reason to worry that your cat may have some sort of immune system problem or contributing disease making it easier for the fungus to infect her. All in all, though, with the current lack of clinical signs I'd be pretty hopeful that the problem is behind her.

Mike Richards, DVM

Toxoplasmosis - Pregnancy risk with cats

Q: We recently moved from an apartment to a house with a backyard. My two cats (two year old male and one year old female - both 'fixed') made the transition ok (the female was scared for awhile, but the male seemed excited/happy). Now that it's getting sunny, we've been letting them explore the backyard a bit, but don't want them to stay outdoors (I am pregnant, and would feel safer keeping them away from other cats and 'diseases' until after the baby is born). do you have any suggestions on the indoor/outdoor situation? (ie. should we keep them inside only until the baby's born?) Thank you for all the help, RL

A: The most serious problem during pregnancy that involves cats is an infection with toxoplasmosis during pregnancy acquired by contact with the stool from an infected cat. The risk to the baby increases the later in the pregnancy the new infection is acquired. Since cats are normally infected when they hunt and catch small rodents, it is less likely that one would be infected if it is an inside cat. In addition, the most common site for humans to come into contact with the cat's stools outside is probably in the garden -- cats like to bury their bowel movements in the soft soil in the garden. So keeping the cats in reduces the chance of accidentally coming in contact with cat feces. So I vote for keeping the cats indoors and having your husband do the litterpan cleaning until after the baby is born. Wear gloves while gardening. Be very careful not to eat undercooked meat (a more common route for infection) and wear gloves or carefully wash your hands after handling raw meat.

Mike Richards, DVM

Last edited 09/23/02


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...