Parasites - Ringworm


Lufenuron (Program Rx) for the treatment of Ringworm in dogs

Ringworm (dermatophytosis) can be treated with lufenuron (Program Rx).

Dr Ziony's recommendations are as follows:

Thank you for quoting my research (JAVMA publication, Nov 15, 2000) in your answers regarding the use of lufenuron for the treatment of fungal infections of dogs and cats. I would like to update you on certain innovations which I had the privilege to present at the Boston AAHA Annual meeting on March 26, 2002. Based on additional clinical experience the recommended dosages of lufenuron are as follows:

Cats and dogs: 80-100 mg/kg Cats in catteries: at least 100 mg/kg The treatment should be repeated once every two weeks until at least two consecutive fungal cultures are negative over a period of two weeks. In our JAVMA publication we reported on a mycological treatment study based o 23 cats and 16 dogs (a total of 39 animals). In addition 297 lufenuron-treated animals were included in the clinical study. The new data is based on the mycological examination of 59 cats and 47 dogs (a total of 106 animals). Cats (59). These were 56 cases of M. canis, 2 cases of T.mentagrophytes and one case of M. gypseum. Dogs (47). These included 28 cases of M.canis, 14 cases of M. gypseum and 5 cases of T.mentagrophytes. In JAVMA we reported mean recovery times of 8.3 days for cats and 14.5 for dogs. In the new study the range of recovery times for cats with M. canis and M. Gypseun is from 6 to 37 days with a mean of 13.7 days. For dogs the new values are 6 to 32 days with a mean of 16.7 days for M. canis and M. gypseum. For cases of T. mentagrophytes recovery takes a little longer: 16 days for cats and 18 for dogs. These times are based on the time taken for daily fungal cultures to be negative and remain negative for 6 to 8 weeks. times are based on the time taken for daily fungal cultures to be negative and remain negative for 6 to 8 weeks. Dr. Yair Ben Ziony DVM, (Also in the name of Dr. Boaz Arzi, DVM, and second Author of our JAVMA publication)

This is not an approved use for lufenuron in the United States. However, it does appear to be a relatively safe treatment for the condition and the ease of use is also a benefit.

Mike Richards, DVM 7/7/2002

Ringworm or skin infection

Q: Dear Doc, About a month and a half ago, I aquired a small mix breed dog. I took him to the vet to get wormed and rabies shot. a few weeks later I took him to see the vet for a foul odor that ran thru the house anywhere he went. The vet squeezed his anal gland and it did appear to be the same odor. A day and a half later (approx.), I saw one bald patch. I called the vet since he was going back in to be neutered. He thought that it was ringworm. How long does it take for ringworm to show up? He told me they are very contagious to humans. He was even reluctant to handle Boo himself. I need this infor asap. My children are out of town right now and when I pick them up we will be going on vacation with several other family members. I do not want to expose them if it is possible we are going to possibly infect them. Also I would like to know if it is possible he contracted them from the vets office. He is an indoor dog and only goes outside for walks and bathroom visits. He is bathed reguraly, and the vet saw no signs of this at the visit just a day and a half before. He said he saw no signs of fleas and his coat looked very good. Thanks, Rita

A: Rita- It is not possible to diagnose ringworm in a dog from the appearance of the sores. It is possible to be suspicious it is there -- but it takes a culture and/or careful examination of affected hairs to diagnose ringworm. I don't feel competent to examine hair shafts for the organism so I rely on culturing. Ringworm definitely occurs in dogs but it is not the most likely cause of odor from skin or even the most likely cause of small areas of hairloss. Did your vet test for this disease? If not, that would be a good first step in diagnosing the problem, along with skin scrapings to make sure it isn't from a parasitic infection.

I don't think of ringworm as highly contagious but it definitely is contagious. It will sometimes infect family members. It is most commonly picked up from the environment. Cats can be carriers of ringworm and show no clinical signs so they have to be considered as a source if you also have cats and this does turn out to be ringworm. There seems to be a lot of variation in susceptibility to this organism. I have been practicing veterinary medicine for 18 years and have never contracted ringworm. A technician who worked for us for several years used to get it everytime an animal came in the clinic who was infected. In fact, she would often get ringworm lesions before the cultures were positive! If your vet has this problem I can understand the reluctance to touch an animal that might be infected -- even if the risk of the disease is relatively low.

Anyway -- ringworm can be contagious to people but there is a very good chance that your dog has something other than ringworm. Please confirm this problem before getting overly worried about it. If it is present, vacum the house well and change the vacumn cleaner bag every day for a week or so. Clean surfaces you can with a disinfectant that will kill ringworm. Treat your dog with an oral medication (they cut out the contagiousness faster than trying to treat them topically). Make sure the kids wash their hands after playing with the dog.

Mike Richards, DVM


Q: When we bought Misty, a four-year-old Yorkie, from our neighbors last August, she had some crusting on her ear rims. We took her to the vet for a genenral checkup, and he diagnosed it as ringworm. He used an ultraviolet light and did some skin scrapings. He told the onsite groomer to try to get as many of the scales off as possible during bathing, to use a special shampoo and let it stay on her for 10 minutes before rinsing, and told her to sanitize everything after so as not to infect other animals there. He told me to go home and launder everything she comes in contact with in hot water and Clorox. He prescribed Tresaderm (15 ml), Fulvicin (125 mg), and Dermazole shampoo. I took her back to him one month later and he said she was progressing nicely, to continue the Tresaderm and Dermazole shampoos, and if her ears looked ok in a few weeks we would not have to come back for this problem. I liked this vet but he was a loooong drive from us. In the interim, a new vet opened shop in the new strip mall around the corner from us. When Misty developed a back problem and was in obvious pain ( to be addressed another time), I took her over there because I did not want her to have to suffer a long car ride at traffic time. For the ear problem, he renewed the prescription for the Tresaderm and also recommended I purchase Hesaseptic Flush Plus and use it twice a week to remove a little wax.

On December 10, vet #2 did a fungal culture that came up negative. He then prescribed Liquichlor ointment to be used on her ear rims and recommended that I remove as much of the crusting as possible. He also said to wash her in Nusal-T shampoo. His diagnosis was ear margin dermatosis (seborrhea). In March vet #2 spayed her and cleaned her teeth, which were slightly infected but not bad enough for her to lose any. Ten days later he took her stitches out and we noticed a little crusting/flaking on her chest. He said it was a staph infection and it looked like it was healing.

On April 10 we saw vet #2 again because the skin crusting was spreading. He said it was still the staph infection and prescribed Cefatabs (100 mg, one pill twice a day), and Hydroxyzine (10 mg, one pill twice a day). He advised us to return if it wasn't better in two weeks. This past Saturday night I felt a dry patch on my cheek while reading in bed. I had my suspicions. The next day, I saw a small circular flaky patch on my lower left cheek, just where her head rests when I carry her down and up the stairs to take her outside. I had been monitoring her all along and was restraining myself from taking her back to the vet before the meds had two weeks in which to work. By Sunday, the flakiness seemed to have spread and also risen in an upward fashion. Took her in Monday and he wasn't convinced it was ringworm until he used the ultraviolet light...boy did she glow green! My dermatologist will see me on Friday to treat my ringworm. The vet prescribed Fulvicin (250 mg, 1/4 pill twice a day) and Dermazole shampoo to be used every five days. He said to let it sit on her 15 minutes and then try to scrub the crusts away. (Unfortunately, she has longish hair and it's hard to know where they all are...and I don't think any groomer would want to htrim her now!) He also said to continue with the Cefatabs until they're gone (another 7 days) and to use the Hydroxyzine as needed to control her itching. We're to report back in three weeks.

I don't know what to do to prevent my husband from getting this and to prevent Misty and me from reinfecting each other and infecting him. Vet #1 said to was everything in hot water and Clorox. Vet #2 didn't seem to know what we should do. He did say to wash her feed bowls out with a water/Clorox solution, but to do that only once. Should I wash everything Misty (who sleeps with us) and I come into contact with, including sheets, pillow cases, quilts, towels, and all dog linens (bunkies, baby blankets and quilts, crate quilt, and three dog bed covers) in hot water and Clorox? If so, how often? Daily? Every five days when I shampoo her with the Dermazole? Once a week? And what do I do to "de-ringworm" the upholstered recliner we share along with the couch and loveseat she naps on and upon which she rubs her ringwormy face? Would a Lysol/water solution lightly sponged over the upholstered furniture take care of the ringworm spores and prevent us from reinfecting ourselves? If so, which Lysol product, the cleaner or the "straight" stuff, how much cleaner mix with how much water, and how often? I just do not know what to do. Our bed linens and towels will be destroyed with too much hot water and Clorox, and I don't think the upholstered furniture will fare too well if "washed" with Lysol too often...but if I must, then I must.

Also, do you think it is time to take Misty to a veterinary dermatologist? We're in Irving, Texas, and we have access to Texas A&M, but I do not know if a veterinary dermatologist and/or Texas A&M require a referral, which we do not have. Her ear rims did not glow, but, as I understand it, the ultraviolet light does not catch ringworm about 50 percent of the time. Wouldn't it be ironic if that's what she had all along and vet #1 was correct?

One more thing...I usually use tearless puppy shampoo on her head and face and whatever current medicinal shampoo prescribed for her on the rest of her body because I do not want to risk getting anything harsh in her eyes. Vet #2 said not to use the puppy shampoo, to use the Dermazole instead all over her, but to avoid getting it in her eyes (yeah, right) and to put a drop of mineral oil in each eye first. This sounds almost impossible. And I have to let it sit on her for 15 minutes before I rinse it off. Yet she does have this crud on her forehead. She's such a little thing and so sweet, and she gets scared very easily, as we all would if we lived in a world of benevolent giants who nonetheless imposed their will on us. My previous dog, a miniature poodle, seemed to intuitively know that anything uncomfortable I did to her was to help her. This one just gets scared. I've written you a small novel, and I apologize for that. There are a lot of questions buried in this narrative. Thanks for any help you can provide.

A: The most recent information I have seen on ringworm (dermatophytosis), a fungal infection, suggests that only systemic medications like griseofulvin are really effective in treating dermatophytosis. There is evidence that using anti-fungal shampoos is helpful, though. Griseofulvin stops the infectivity of the fungus pretty quickly but may take 6 weeks to clear the infection entirely.

Dilute bleach solutions are effective in killing residual ringworm but I read recently that the single most effective environmental control is vacuuming. By thoroughly vacuuming the house and then throwing away the vacuum cleaner bag each time for several weeks it is possible to lessen the number of fungal spores significantly. Clean the things you can with dilute bleach (like waterbowls) and then vacuum everything else well.

It would be a good idea to be sure you do have a ringworm infection, even though that does seem very likely. It isn't sufficient to do a Wood's lamp test in diagnosis of ringworm since there can be both false positive and false negative fluorescence. Fluorescent hairs should be cultured to confirm the ringworm.

It probably isn't necessary to go to Texas A&M at this point but that is a good option if the problem continues despite therapy.

Hope this helps. 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...