Cat Parasites


Bartonella henselae

Question: One of my cats has been diagnosed with Bartonella (level 4). As a foster home for rescued cats, I currently have 14 cats waiting to be adopted in my home. A few questions: 1) What does level 4 mean? 2) Can this cat give it to my other cats by sharing water and food - or does it have to be through a bite or grooming? 3) What would your recommendation be for my other cats. Should I just treat them all whether they are positive or not? 4) Is Zithromax the drug of choice? (If so, what dosage do you recommend ?) Any other suggestions greatly appreciated! Thank you! Audrey

Answer: Audrey- Bartonella henselae, which is the usual species of Bartonella in cat infections is currently thought to be transmitted mostly through flea bites. Strict flea control is thought to be the best way to control spread of the disease. It can also be spread by blood transfusion. With this in mind it seems likely that it can be spread through any method in which an exchange of blood occurs, so fighting among cats would seem to place them at risk, as well, although I can't recall seeing any proof for this mode of transmission. I really don't know what Level 4 means in the test results and you are the second person to ask me this, so it has to be something that one of the labs is reporting. The titer considered positive for infection is 1:64 at the NC State Vector Borne Disease Laboratory so that doesn't seem to correlate. Your vet should be able to find out from the testing laboratory what the level 4 designation refers to. There is a lot of disagreement over how often Bartonella causes disease in cats. When disease does occur the clinical signs are thought to be fever, lymph node enlargement, gum infections, eye inflammation (uveitis) and transient depression. These signs are possibly more likely to occur in cats with feline immunodeficiency virus (FIV). Whether Bartonella can cause serious disease by itself in cats is still open to some debate. Two classes of antibiotics seem to be most helpful, macrolides (erythromycin, azithromycin, clarithromycin) and combinations of a penicillin based antibiotic (ampicillin, amoxicillin, others) and a fluoroquinolone ( enrofloxacin (Baytril Rx), dicloxacin (Dicural Rx), others). I do not believe that the ability of any antibiotic or antibiotic combination to completely clear B. henselae from the blood stream of cats has been proven at this time, but I could be wrong. There are several recommended dosing schedules for azithromycin but we tend to use 5 to 15mg/kg every 24 hours for 3 days and then every 48 hours. It is necessary to treat for at least 6 weeks when treating for Bartonella henselae. Since it doesn't appear likely at this time that it is possible to completely eliminate B. henselae from the blood stream of cats with antibiotics it probably doesn't make a lot of sense to try to treat all the cats and it might not even make sense to treat the cat with the positive titer, unless it seems like B. henselae is actually causing disease symptoms at the present time. There is a good summary of B. henselae infection on the NC State web site --- Mike Richards, DVM 1/11/2005

Hole in cat (Fly larvae)

Q: I was at my friends house and I was petting her cat when I felt something wet on his stomach. I turned him over and there was a hole the size of a pencil head in the cat. It was clean and didnt seem infected. someone told me it was a cyst and common in cats. It was yukky and you could see inside the cat. Is this normal and what should she do? Thanks alot.. Wendy

A: Wendy- No holes through intact skin are normal. Your friend should definitely take her cat to the vet. This may be a "wolf" -- a fly larvae that is deposited under the skin, leaving a hole over a lump that contains the larvae, a ruptured abscess, a mammary tumor (more common in female cats), or it may be a skin cyst or tumor that has ruptured. In any case, it would be best to get a diagnosis and appropriate treatment.

Dr Mike Richards, DVM 8/20/2003


Hemobartonellosis (haemobartonellosis, feline infectious anemia) is caused by a rickettsial organism, Haemobartonella felis. Rickettsia are microscopic parasites.

A cat with hemobartonellosis experiences depression, weight loss, decrease in appetite and anemia. There may be jaundice associated with this and approximately one-third of untreated cats will die from the infection. Cats that "recover" are usually infected for life but the organism is suppressed by the cat's immune system. Subsequent immune compromise from viruses like feline leukemia, stress or administration of corticosteroids cause a recurrence of the infection. The disease is probably transmitted by blood sucking insects and from infected mothers to their kittens during pregnancy. It may be possible to transmit from bite wounds and blood transfusions as well.

The organism is visible in blood smears of infected cats but it has a tendency to come and go in the blood stream so it is sometimes necessary to make blood smears over the course of several days to identify the parasite.

It can be treated with tetracycline class antibiotics with good success but even treated cats should be considered to be carriers of the disease and may experience recurrences later. Supportive care is often necessary for several days in cats with this condition and during the acute infection if may be necessary to use corticosteroids despite the immune suppression associated with these medications. It is very important to control fleas and other blood sucking organisms in a multiple cat household in which one member is found to have hemobartonellosis. It is a good idea to occasionally do followup bloodwork to make sure anemia is not recurring. Mike Richards, DVM 8/5/2003

Treating fleas on Kittens

Question: Dear Dr.Mike,

Both our kittens have a pretty severe flea problem. I would like to use some type of flea product on them but everything I have read states "do not use on kittens under 12 weeks of age". We are not really sure just how old the kittens are but we do know they were born sometime in October,2000. Is there any of the "Control or Advantage" type products available for kittens of this age? It has been suggested that we use the commercial dishwashing detergent Dawn for flea bathing. Are you familiar with this practice and if so, do you reccomend it? In the meantime we are using Kitten shampoo but I am not too confident in the flea-killing properties of most of the kitten shampoos available.

Thank You for your assistance. Cordially, Larry

Answer: Larry-

I think that Frontline Topspot Plus (tm) is approved for kittens 8 weeks of age (I have to rely on my memory as it will be several days before I get back to the clinic). It is a good flea control product. Frontline is usually available only through veterinarians, so check with your vet to see if he or she uses this product. If not, my guess is that they have a method for dealing with fleas on young kittens that they can help you implement.

Dishwashing detergent will kill adult fleas if the lather is left on kittens for ten minutes or so, but it is a very inefficient flea killer and it can cause drying of the skin. Flea and tick shampoos work well to kill fleas that are on the kitten at the time the shampoo is applied but have no residual effect, so it is hard to eliminate fleas with these products, too.

Mike Richards, DVM 12/24/2000

Cheyletiella species mites

Question: Dear Dr. Richards,

I will be very happy if you can help me,.One of my female brings me after she has been covered mites, if I am not wrong they are "cheletelya parasiti vorax" as we say in French. A few year ago one my female had these mites and my friend of Canada send my a shampoo in two washing it dessapeared. But now He stops breeding, I am unable to get the name of these shampoo. Now I have myself about 60 bites all ower my body except in the face, but arms, shoulders, legs have small bottoms I get mad with theses itches. Please could you help me telling what I can make to avoid these little mites. Thank you. Kind regards from Switzerland. M.

Answer: M.-

Cheyletiella species mites are usually pretty easy to kill using products that will kill fleas. It is necessary to use a shampoo or topical product several times at weekly intervals to be sure that the mites are killed. Since Cheyletiella mites can live in the environment for up to ten days, it is necessary to treat the house to keep the mites from returning. Standard flea control treatments for the house will usually work to kill the mites. It may be necessary to treat the house more than once in some cases. If this approach doesn't work, giving ivermectin orally at a dose rate of 200 to 300ug/kg three times at 14 day intervals will usually control the infestation.

If this is a dog, you might be dealing with sarcoptic mange. This will respond to topical medications in many cases, too. People can be affected by this mite and it does cause very severe itchiness in humans. We usually use ivermectin for this disease at the present time, because it is easier for the clients and because it works well. Your vet can probably provide this medication after confirming the diagnosis.

I don't treat people, but it is my understanding that the itching can be relieved with medications, if you have contracted this mite. The infection is self-limiting in humans and will go away two or three weeks after you successfully rid the dogs of the infection and are not picking up more mites from them.

Hope this helps some.

Mike Richards, DVM 8/7/2000

Ringworm, cheyletiella mites or what

Question: Hello Dr. Richards,

My question is about ringworm..maybe! About a year ago, I inadvertantly transmitted ringworm spores to my 3 cats by picking up a kitten that belonged to a neighbor and then picking up my cats. It was diagnosed because I got it on my arm and one of them lit up green on a wood's lamp, as well as a positve culture. Two were only carriers, but one was very affected. She and I took griseofulvin for 6 weeks. Lyme dips for all three every 5 days and the house was vacuumed twice a day and all material was washed in hot water and covered in sheets which were changed daily. In other words, a very aggressive approach. During that time, we transferred from humid coastal Florida to Gulfport Miss for the summer into a corporate rental (so no furniture was brought and contamination was nil) and there we all recovered and had no symptoms. At the end of summer we transferred to our final destination in Monterey Ca, which is much drier and cooler. After 3 months all the winter things, which had been previously intensely decontaminated, were brought out and within one month, the female cat which had been so affected before, began making that same itchy face again, and pulling her hair out. These are the same things she did when she had ringworm. I got a box of vitus tests from the vet and did it, and lyme dipped her. The test came up with nothing for 21 days then it turned red. It was fairly covered in some sort of growth for about 10 days before turning red. I did more tests, each at 7 day intervals before lyme dipping her, and so far there is no reaction, but they aren't that reliable anyway. The problem is, she is literally covered in dander on her back by the 5th day after dipping and is yanking her hair out on her back. She has a suspicious round absence of hair on the back of her leg as well, which is now filling in again. And the way she yanks her hair out is so random. There are some pertinent asides to this though. She is quite overweight and short in stature (she was the runt). I bottle fed all three of them from 10 days old on and she didn't take to the bottle very well. She is nervous, but very loving and happy when all things remain stable. After moving twice and all those weekly visits to the vet, she got so demented and violent the vet put her on kitty "prozac" for several weeks and she regained her normal personality after a while. This time, she is being treated at home to avoid this bizarre reaction. So she does have a predisposition to nervous behavior. As for fleas, they are all treated with frontline topspot each month. None of them goes outside, but the carpets are treated with 12 month treatment since you never know about fleas. I have seen no evidence of fleas since her outings to the vet in Miss. That includes with combings. The only other variable is that now we have a gas fireplace that remains on almost all the time. She likes to lay in front of it and it is warm and perhaps she is drying out her skin or something. The other two cats remain healthy and with only a little bit of dander, which I have seen on them before when it is cold. No excessive itching or spots. Her first bout with ringworm was very obvious. Round scaly patches with no hair in those spots, not hidden at all. This time it is general loss of hair on back and yanking, but with loads and loads of dander. There is no sign of any other crawly under a microscope. I have read all your posts on this subject and tried to answer all the questions you have posed to others. I am truly at a loss here! I have heard about horror stories of ringworm lasting for years as the spores can live for so long, but aside from burning everything I own, I have done all that can be done, including moving! I haven't got ringworm spots this time, and I am one of those unlucky people that gets it by looking at something with ringworm. Could this be nerves? Dandruff to the umph degree? Something dietary? She has been eating the same food, no changes,for her entire life. Vitamin deficiency? Lunacy? Will that vitus test turn red without ringworm present? I hate to put her on griseo again, because of the liver involvement. Any thoughts at all would be so welcome. I love the little troublemaker and want her to be happy and healthy. Thanks! C. B. -

Answer: C.B.-

Fungal cultures which use a change to a red color as an indication of the presence of ringworm have to be interpreted carefully. Many fungi can cause color change on these cultures if they grow long enough, so it is very important to watch for growth of an organism and then to determine if there is an immediate color change. If the color changes very close to the initial growth of the fungus it is usually a dermatophyte (ringworm). If the color change occurs later, especially ten days later, it is unlikely that the fungus growing on the culture plate is a ringworm organism. It is probably just a contaminant.

Unfortunately, that doesn't mean that ringworm isn't present -- it just means that particular culture didn't grow it. If signs suspicious of ringworm persist it is best to do another culture. If there isn't a really tempting area to culture (one that looks like a ringworm lesion). we like to do "toothbrush cultures", in which a brand new toothbrush, fresh from its packaging, is used to brush the haircoat over a wide area. Then the bristles are cultured to see if a ringworm organism has been picked up.

We don't see cheyletiella mites here in rural Virginia very often, but your description of really severe dandruff sounds like the descriptions of skin disease associated with this mite. If this mite is present you should be able to see the mites with a magnifying lens of some type, if you look carefully at the dander. These are supposed to be pretty mobile mites and it may be hard to find them on a microscope without using a "scotch tape" preparation -- catching the mite on scotch tape by pressing it over an area with dander. Of course, this is NOT the voice of experience -- I am just relaying my understanding of what I read about this mite. It might be worth checking into this. I'm sure that a veterinarian in an area in which this mite is more common would be able to help determine if they are a problem.

Another mite possibility that could be hard to find without skin scrapings would be Demodex mites. These are not as common a problem for cats as for dogs but demodecosis can occur in cats. Skin scrapings or skin biopsies may be necessary to find this mite.

Dry air from force air heating does cause dandruff in the winter in a lot of cats. So that is a possibility, too. Bathing and using a moisturizing conditioner or using a spray on conditioner without bathing, may help if this is the problem.

Cats that are obese sometimes don't groom well enough to keep dander down. They usually have dander mostly around their lower back and tail area, though. Really really obese cats may have dander or oily hair on most of their trunk, as they sometimes have difficulty grooming at all.

Repeating the ringworm culture, skin scrapings and a "Scotch tape" test for cheyletiella mites all seem worth considering, to me. From that point, skin biopsies might be the next logical diagnostic test but you also might want to consider asking about referral to a veterinary dermatologist for help.

Good luck with this.

Mike Richards, DVM 12/8/99

Cat demodex mites - transmissible to humans or not

Q: Dear Dr. Mike Richards:

My cat inadvertantly passed on to me the demodex mite. This condition, began as a dark, waxy exudate in both his ear canals. Another sign that came with his condition was this. With very little effort a slight tugging of his hairs pulled them out. They looked as if they had been cut with a pair of scissors. He had gone through molting in the past, and his hairs, those that came away from his body through moulting, all looked old and withered. And all of them were curled or wrinkled at the tips or ends. And on parting the hairs of my cat, many hairs too numerous to mention had tiny white specks attached to them. These two peculiar conditions were indicative of a generalized population of mites on his body. Not, I might add, a localized population. Please warn all of your subscribers and non-subscribers that this is a very serious and dangerous condition, both to pets and humans. For these reasons, a.) it is not being taken seriously by professionals in the field of dermatology, even though the condition has been well researched and documented. And is known to pass from pets to humans. Doctors are disregarding this fact. And citing other reasons for the pain and suffering in humans from this and other mites that clearly do pass from pets to humans under the heading Demodetic Mange. And b.) if they contract one of the mites under the heading Demodetic Mange, there are no drugs available to fight these conditions, since doctors, vets, and drug companies are reluctant to pass on the benefits being given to animals who passed on these conditions in the first place. This, of course, I know is a national scandal since drugs are as a general rule, tried and tested on animals first in order that they might one day, if proven in the field of dermatology, be beneficial to humans for human conditions. However, these drugs do work, and I firmly believe they should be benefiting humans right now for the same conditions that animals are suffering from. I have one more thing to say; it is this: Demodecosis is not rare in cats as you have now discovered in your recent research. The reason is patently clear: it is because doctors, for whatever reason, are failing to pick up on it, and that it can and does, and I might add, has passed successfully on a number of occasions from pets to humans.

Sincerely, Rodney

A: Rodney-

I can not find any references to transmission of demodex mites from cats to humans. The demodex mite of cats is a surface dwelling mite, which is unusual for demodex species and it is conceivable to me that there could be temporary transfer of the mite to a human, similar to the situation that occurs with sarcoptic mange mites. Demodex mites are considered to be species specific, which means that the demodex mite of dogs infects dogs, the mite of cats infects cats and the human mite infects humans. People do have a naturally occurring species of demodex mite, which is fairly common on humans if it is looked for through skin scrapings or other diagnostic techniques. If you have information that contradicts the notion that demodex mites are species specific, I would really like to know about it.


Mike Richards, DVM 7/12/99

The difference between fleas and lice

Q: If you could please send me some more information regarding lice it would be appreciated. Alecsis

A: Alecsis-

Lice are small light colored (white to cream colored) parasites. The lice themselves are visible to the naked eye but can be hard to find as they are pretty small. Examination of debris from the haircoat with a magnifying lens might help in identifying them. Their eggs (nits), which are attached to hair shafts, are often much easier to find than the lice themselves. The look like little white to yellow lumps on the hair and are often deposited along the whole length of hair shafts that have nits. They can infect both dogs and cats but are not commonly seen in veterinary practices in most of the U.S. Lice are susceptible to many of the products that kill fleas but it may be necessary to clip mats from the haircoat and to use insecticidal products for several weeks (4 minimum) to totally eliminate the lice.

Fleas are larger, reddish-brown to brown to black parasites that are very mobile are often easy to find in the haircoat of pets that are infested with them -- but which can be present on the pet or in the environment without being easy to find due to the ability of pets to chew or scratch fleas out of their haircoat. The new flea products, Frontline (TM), Advantage (TM) and Program (TM) are all very effective in reducing flea populations in pets and it is finally possible to almost do away with this problem in most households.

Mike Richards, DVM

Haemobartonella in Kitten

Q: Dear Dr. Mike,

Thanks to a vet that is willing to go the extra mile, we have a preliminary diagnosis. Equus has Hemobartinella parasites in his blood smears.

I read the information you have on hemobartinella, but am curious what the long-range prognosis is. Do cats with this parasite live a standard length of time if treated?

We are much relieved to have a diagnosis, even though it sounds scary. Again, I should mention, he tested negative for both FIV and Feline Leukemia -- is this a for sure thing? I've been reading that these two can run in conjunction with each other (I am guessing much like human aids and particular pneumonias?) This is the third time he's been tested for FIV and Feline Leuk and he's always come back negative. He is an exclusively indoor cat as well.

Is it possible that both Equus and Elijah got this from their mother when they were young and have carried it the whole time? If so, would Equus' weight loss after the dental surgery have compromised his immune systme enough to cause this parasite to begin spreading? Because the shelter we got them from keeps good contact with their adopters, should we let them know so that this won't be passed on?

Again, we have a very good vet whom I plan on asking these same questions, but a second opinion would be great.

Thanks again, Stephanie

A: Stephanie-

It can be hard to find Haemobartonella organisms on a blood smear so it is good that your vet was able to do this.

Tetracycline type antibiotics (oxytetracycline and doxycycline) are reported to be very effective in eliminating the clinical signs of disease when given for three weeks. Enrofloxacin (Baytril Rx) may also be effective for this disease.

Even though most cats respond well to treatment they remain infected with the Haemobartonella organism in most cases. In theory they could have a recurrence of the disease later, due to stress or other immune system suppression. This is apparently not too common, though. It appears that the cat's immune system learns to suppress the organism but just can't eliminate it. I don't know about Equus, but I find dental work pretty stressful so perhaps it is a severe enough stress to disturb the balance between his immune system and this blood parasite.

There are reports of a higher incidence of haemobartonellosis in feline leukemia (FeLV) infected cats but it can and does occur without FeLV infection. When there is severe anemia and it doesn't respond to standard treatment for haemobartonellosis it may be worthwhile to do a bone marrow aspirate and test that for FeLV.

It would be a good idea to maintain effective flea control with Frontline (TM) or Advantage (TM) as there is some chance that haemobartonellosis may be transmitted through flea bites, making it possible that Elijah could be infected if he is not already and fleas are present.

It seems very likely that the cats were infected prior to the time you acquired them. It would be a good idea to contact the shelter, just to let them know that the problem occurred in case someone else calls them for information on a possible cause of fever in a cat adopted at about the same time. Not likely, but it wouldn't hurt for them to know.

Hope this helps some. The good news is that most cats do respond well to treatment.

Mike Richards, DVM

Mites (Notoedres)

Q: I have 18 cats, some who are wild. We have been dipping the ones we can handle in a lime sulfur dip every 5 days. The ones that we can't touch we trap and take to the vet, they then put them to sleep and then dip them, this is getting very expensive. It feels like a circle we get one cleared up then another shows signs. Is there any other way to treat the mites. Is there a oral medicine or injection that we can give to everyone. This has been going on for 5 months. I live in Pt. Hueneme Ca., our vet said this mite is not common to our area, but its spreading like crazy, any information or advise would help. Thank You A: S-

I have heard persistent anecdotal endorsements of fipronil (Frontline spray and Frontline Topspot, Rx) for use against various mites, including Notoedres cati. This should be very safe but I am not aware of any scientific studies supporting the effectiveness of this therapy yet. In addition, many veterinarians use ivermectin for the treatment of notoedric mange in cats. This is an effective treatment but there have been some anecdotal reports of toxic reactions to ivermectin in cats. I have heard enough of these reports to warrant some caution when using ivermectin to treat mites in cats but it may be justified in your circumstance, since all cats could easily be treated at one time and the cost would not be exorbitant. Frontline would be safer but probably more costly. It does also control fleas and ticks, though.

Mike Richards, DVM

Mites in Cats

Q: Dear Dr. Mike,

We need help. Our beloved Gator (a Cat but like a son to us) has a bad case of mites. The vet has Lime dipped him twice and the second one really made him sick, the vet didn't understand why the dip would make him sick. He has lost a lot of his coat. Our thinking is that given the fact that his coat is almost gone possibly the lime dip seeped through his skin and made him sick. In any event, we need help.

Currently he is taking Clavamox and the vet is thinking about oral cortisone?

Do you think milbemycin (Interceptor Rx) could be used for Gator??

Any thoughts would be greatly appreciated.

A: Rick-

There are four species of mites that are known to affect cats, that I am aware of. The two most common are Cheyletiella blakei and Notoedres cati. Over the last few years more and more cases of Demodex sp. (there appear to be two species of Demodex that infect cats) have been recognized. Finally, there is a mite, Lynxacarus radovski, that is seen commonly in Hawaii and Australia and occasionally in Florida, according to Dr. Sousa in the Veterinary Clinics of North America, Feline Dermatology, July 1995.

I think we can safely rule out Lynxacarus based on your location.

That leaves Notoedres, Cheyletiella and Demodex mites. From your description, I am most suspicious of the notoedric mange but can not be sure so it is probably best just to cover all three here.

Notoedric mange is an itchy infection that often has a lot of scabbiness or crustiness associated with it. It usually starts on the cat's head but can spread elsewhere, especially around the paws. Usually, the mites are easy to find on a skin scraping. It is contagious to cats, dogs and people. When treating for notedric mange it is important to treat all pets in the household since an early infection in another pet may go unnoticed and lead to reinfection of the whole household. Lime sulfer (LymDyp Rx) is usually effective if affected cats are dipped weekly for 6 to 8 weeks and is considered to be among the safest treatments. Ivermectin (Ivomec Rx) is used frequently, although it is not approved for use in cats, and is often effective if two doses are given two weeks apart. It seems to be pretty safe, as well. Amitraz (Mitaban Rx) has been used in cats at a lower dose (0.025% solution) than is used in dogs. It is also reported to be effective but is probably not as safe as either lime sulfer dip or ivermectin. Fipronil (Frontline Topspot Rx) has been reported anecdotally to be effective against these mites but I do not know how effective. Treatment for secondary bacterial infections with antibiotics may be necessary and it seems to be OK to use cortisones to control itching without seriously affecting the effectiveness of the mite medications.

Cheyletiella mites are large mites that are sometimes referred to as "walking dandruff" as they can be seen by many people without magnification. Cats are efficient at removing these mites and it may take a persistent effort to find them in some cases, though. They can be found on skin scrapings and sometimes show up in fecal samples from affected cats who have ingested them. Infection with Cheyletiella mites produces variable itchiness, dander flakes that are white or cream colored and sometimes scabbiness. These mites are easy to kill but getting rid of an infestation can be difficult because these mites can live in the environment for a while and commonly affect all the cats in a household. Treating the house with flea control products will usually kill the mites in the environment. Lime sulfer dips, most flea control products, ivermectin and amitraz will all kill these mites. Ivermectin should be given three times at two week intervals for cheyletilliosis.

Demodex mites are being reported more commonly now than in the past in cats. It is unclear why there is an increase in cases. Demodecosis in cats may be associated with persistent accumulation of waxiness or liquid consistency exudate in the ears, hair loss, scabby skin lesions, and secondary skin infections. In our practice we have seen this primarily as hair loss with itchiness but not much other sign of skin disease or as persistent ear infections. There doesn't seem to be a clear consensus as to the best method of treating demodecosis in cats. We have used ivermectin at two week intervals for several injections and seemed to have success with this as far as eliminating mites from skin scrapings but we had one cat that still exhibited pruritis and hairloss in the same pattern despite the fact that we couldn't find mites anymore. Skin biopsies of this cat were not diagnostic of any other skin condition nor of demodecosis but we had treated the cat prior to the biopsy. I would probably try amitraz as a second choice for treatment and this is another mite that may be susceptible to fipronil based strictly on anecdotal reports. I suspect that milbemycin would be effective but have not seen any reports of anyone actually trying it. It would be a very good idea to contact the manufacturer to make sure that there is not a known adverse reaction in cats prior to using this product. I am not aware of one but the pharmaceutical companies often receive reports of problems when their products are used in unapproved species.

That covers the mites.

I can not explain the reaction to lime sulfer dip that your cat experienced as it is reported to be very safe in cats. There are occasional reports of problems with lime sulfer dip in rabbits and I have seen at least one reference to a problem in a cat on a veterinary bulletin board on the Veterinary Information Network. Since ivermectin is pretty safe and probably effective for all three types of mites it seems like a reasonable alternative to me. If it isn't effective, then I'd probably try fipronil and amitraz, in that order. If all of that didn't work, I'd call Novartis and see if there was any problem with using milbemycin that they were aware of and give it a try if it seemed reasonable to do so after talking to them.

Persistent mite infections may be associated with feline leukemia virus infection or feline immunodeficiency virus infection. If treatment is not successful it may be worth checking for these viruses. It is pretty easy to confuse several other diseases with mite infestation, including atopy, phemphigus, food allergies, ringworm, bacterial skin infections and flea allergy dermatitis. If the mites clear up but the problem doesn't it would be a good idea to consider the possibility that there is a secondary infection.

Lastly, when we have real difficulty with a skin case we refer the patient to a veterinary dermatologist. We are fortunate enough to have one within a reasonable driving distance from our hospital. If this is possible in your area it is also something to consider if the response to treatment continues to be disappointing.

Good luck with this.

Mike Richards, DVM

Hole in kitten's foot - cuterebra or fly larvae

Q: We have 3-4 week old kittens and only one has small round "holes" or lesions on its paw, and on its back. We had to shoo bees from landing on the sores. What could this be and how come the others don't have it and we have never seen it before? The paw in question has concave pads and is swollen. Its very sad and we are trying to find out if there is anything we can do. Thanks for your help.

A: It is possible if the paw is swollen this could be an abscess or some type of infection. The other possibility is cuterebra or fly larvae and the "hole" you are seeing is actually a fly larvae. Your vet should be able to help with the problem if he/she has not done so already.

Michael Richards, DVM

Liver Flukes

Q: I live in South Florida and have two cats. They have both been diagnosed with liver flukes. My vet explained that this is caused by catching and eating the lizards in the area. Unfortunately it difficult to keep lizards out of the house so even though I try they do manage to catch a few. My cats have been treated on more than one occasion for this disease. My problem is that I don't know if they keep getting new infections or if original infection has not been cured. The cats have no outward signs of infection ( jaundice etc.). I have consulted with another vet and his prescribed treatment is different from my vets'. I am looking for another opinion so I can get a consensus and feel comfortable with the treatment I'm getting for my cats.

A: I do not practice in an area in which liver flukes are found, so I can only report on the treatments listed in the references I have on hand. Sometimes practical experience is better, so be a little cautious of worrying too much about a discrepancy in what I find and what your vet is saying. He or she has the practical experience I don't have. The information below is from Dr. Todd Tams, writing in "The Cat, Clinical Diseases and Management" edited by Robert Scherding. A little of it is from a conversation with another vet about a patient who had liver flukes and moved here from Florida (denoted by personal conversation notation). I am sorry, but I can't remember the name of the vet in Florida who I spoke with.

There are several species of liver flukes that have been found in cats but the most commonly recognized one is Platynosomum concinnum. The fluke requires two intermediate hosts, a snail and a lizard (or gecko, toad or skink). It only takes a week for the flukes to show up in the bile ducts after ingestion of an infected lizard. Eggs will show in the stool after 12 weeks and are found in greatest numbers from 12 to 16 weeks after infection. Signs of infection include lethargy, depression, weight loss, vomiting, diarrhea, jaundice and abdominal distension. The most common client complaint at the time of diagnosis is reduction in appetite, though, according to Dr. Tams. I got the impression that a lot of these cats aren't seen until they turn yellow from jaundice from the vet I spoke with, though. Sometimes there are not sufficient quantities of eggs in the stool to make a diagnosis. Ultrasound examination can be helpful in deciding if this problem might be present and diagnosis can be made by exploratory surgery in difficult to diagnose cases. If surgery is done, it may be helpful to bypass the bile ducts and make a new connection between the gall bladder and the intestine (cholocystoduodenotomy). There is no treatment which has been scientifically validated, to the best of my knowledge. Praziquantel (Droncit Rx) at high dosages for 3 to 5 days is the most commonly recommended treatment. Fenbendazole (Panacur Rx) is also reported to be effective when given twice a day for five days. If severe liver inflammation is present at the time of treatment or develops during treatment, administration of prednisone may be necessary to control this and it must be used long term sometimes.

I didn't find much information on success rate of treatment nor on the recurrence rate in infected cats. I am assuming that if the lizard catching behavior continues that reinfection is certainly likely, though. There is some question as to whether a lot of cats get infected but only a few react or if only a few cats get infected. As more research is done this question may be answered.

Hope this helps.

Michael Richards, DVM Flea Life Cycle

Understanding the life cycle of the flea is necessary in order to control it. The flea has several stages to its life cycle. Adult fleas spend most of their time on the dog or cat - they must be dislodged to leave since they will not do so voluntarily. Despite this, when the flea population on the dog becomes excessive humans tend to be an acceptable alternative to the flea. The average lifespan of an adult flea is probably about 6 weeks - but fleas can live as long as a year under certain conditions. A female flea can lay 20 to 28 eggs a day. She may lay several hundred eggs over her lifespan. These eggs fall off the pet and develop where they land. They are small and can even develop in the cracks in wood floors or other small crevices. A larvae hatches from the flea egg. It takes as few as 9 days to as long as 200 days to go through its growth stages. At this time is forms a pupae and waits for the right time to hatch. Fleas prefer temperatures of 65 to 80 degrees and humidity of 75 to 85 per cent. This range determines the period of time that fleas are a problem in your particular area. For some areas of the country, this is all year. In others, the flea season is relatively short. It is estimated that for every adult flea found on the pet, there are about 10 developing fleas in the pet's environment.

Michael Richards, DVM

Flea Control

Since we know that the flea lays her eggs on the pet and they fall off, it is obvious that they fall off where the pet goes. This means that you must treat your house if your pet comes inside. Many people resist doing this, explaining that they never see fleas in the house. The flea egg does not move and it is very hard to see. The flea larvae does not have legs so it has limited movement. The pupal stage of the flea does not move at all. It is not likely that you would be aware of immature fleas --- until they grow into adults. At this point you will be overwhelmed and the problem will be very hard to control. It is possible to kill the pre-adult stages of the flea in the house. Outside, the flea eggs fall off in areas where the pet does things that dislodge them, like jumping around, sitting and scratching, etc. If these areas are warm and moist throughout the day, the flea can reproduce there. It is not necessary to treat large expanses of lawn that dry out during the day -- concentrate on areas the dog spends time, that stay moist and warm. Make sure you treat around the doors in and out of the house, where your dog or cat is likely to be waiting around and where flea eggs are likely to drop off.

There are now several "once a month" flea control medications for pets. Lufenuron (Program - tm), makes control of preadult fleas easier than it has been in the past. This medication is approved for both dogs and cats. It is administered once a month and is active in the body for that entire time. At the present time there are no known side effects of the medication other than a small percentage of pets who are nauseous after administration of the pill. It may be administered when other medications are being used. The pill does not affect adult fleas at all. Therefore it is important to start this pill before the flea season or to treat for adult fleas as necessary. There are also "once a month" adult flea control medications. Advantage (tm) and FrontLine (tm) are two new medications that provide long lasting adult flea control. Advantage works for about one month to kill fleas and FrontLine works for one month in cats and up to three months in dogs. These are very effective products. While these products may be combined with Program (tm), their ability to kill adult fleas effectively may make it un-necessary. There are many other products that will kill the fleas on the pet. Shampoos, powders, and sprays tend to kill only the fleas present on the pet at the time of application. Mousses (flea foams) and flea creme rinse products tend to have some residual effect. Dips, which are usually used as pour-on products, have a slightly longer residual effect and are more likely to be associated with toxicity. Proban, an orally administered flea killing pill has short duration of action but is made to be given twice weekly. There are "spot on" products as well, which have may have a longer duration of action. However, all of these products are more toxic and/or less effective than FrontLine (tm) and Advantage (tm).

Treating the house should involve a two pronged approach. To kill the pre-adult fleas it is necessary to use methoprene (Precor). This can be done by using this product alone, or in combination sprays with an adult killing ingredient. The ingredients that kill preadult fleas are generally effective for 3 to 4 months, indoors. Killing adult fleas can be accomplished using any of the pyrethrins (tetramethrin, pyrethrin, permethrin, etc.), or an organophosphate. The adult flea killing ingredients do not have a residual effect and retreatment every 2 to 3 weeks until the fleas are gone is usually necessary. These products come in sprays and aerosols (foggers). It is very important to read the directions, figure out the square footage you are attempting to treat and use these products properly. Foggers generally are ineffective unless one is placed in each room, so small size foggers may be the most economical approach. An alternative to this approach is to use a sodium borate product for flea control - such as FleaBusters. Some people use diatomaceous earth (food grade) in the house to control fleas.

Flea treatment in the yard can be accomplished using one of the yard sprays specifically made for this purpose. There is a new approach, in which a nematode (worm) that lives on flea larvae is spread in the yard. This is non-toxic and appear to be effective. These worms are sold by various companies. One brand name is Interrupt, available through veterinarians. Remember, it is only necessary to treat areas which stay warm and moist. For some people this will be the whole yard. For others, treatment of much less than the whole yard will be effective.

Prior to this year (1996), we felt that effective flea control meant that you needed to treat the pet, the house and the yard. Not treating any one of these could lead to perpetual flea problems. It appears that FrontLine (tm), Advantage (tm) and Program (tm) may change that situation and allow control of fleas with treatment of the pet, only.

Flea control can be accomplished if you are careful to take a few steps to ensure that your plan works. Treat your pet with one of the new flea control products. If you elect to treat the house, to it right. Measure your house and figure out the square footage -- then apply a proper amount of flea control product. If you are using foggers, make sure that they will cover the area you anticipate -- don't expect them to treat two rooms by placing one in the hall, for instance. Get a fogger for each room. If you use a professional exterminator, make sure they use a product that kills preadult fleas as well as an adulticide. Pay them to come back in 2 weeks the first time, rather than waiting a month. Keep up the treatment until you see no fleas, then use the preadult products 2 or 3 times a year to keep the problem from coming back.

Fleas can be controlled. It can be expensive to take care of a flea infestation but it is usually cheaper than dealing with the complications to your pet's health that fleas can bring about.

Michael Richards, DVM

Last edited 01/11/05


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...