Ivermectin sensitivity in dogs

 When you decided to welcome furry furriends to your family, many of you would have researched about breed specific health issue so you know what you should be keeping eyes on and what health issue your dog’s breed is most prone to.

 Breed specific health issue is not the only issue you should be keep an eyes on.

 For example, in the previous entry titled “Tick/flea control for dogs“, and “Tick/Flea control for dogs Part II“, I wrote about how you can control flea/ticks naturally without monthly tick/flea control spot on, how to remove ticks, blood test for ticks,and also about tick/flea monthly spot on ingredients and flea/tick monthly preventive study for dogs that was done in 2011 March by North
Carolina University.

 In case you have missed the entry,the University has released the publication on the study of
monthly flea/tick preventative that contains Amitraz. They have studied
22 dogs, and all of them developed pemphigus foliaceus;autoimmune
disorder of the skin.

 The study says that 8
dogs out of 22 dogs developed lesions restricted to only on the
application site, and the other 14 dogs have developed lesions on the
application site plus non contagious areas.

 If you apply monthly
topical application to your dogs, check the ingredients and if you see
Amitraz in the list, talk to your vet about other options for the
flea/tick treatment.

 We tend to give preventative pills without much thought, and your vet might suggest you to give monthly preventative for flea,tick,and heartworm to your dogs.

 Have you ever take a moment and wonder how monthly heartworm pills work?

 To know how it works, you should know what heartworm is,and how dogs get infected with heartworm first.

What is heartworm?

 Heartworm are parasite that is spread by mosquito bites.

 Mosquito must bite a dog that has already being infected with heartworm first to be a carrier of heartworm.

How the mosquito become infected with heartworm?

 According to American Herartworm society, heartworm positive dog’s blood has microfilaria. Then,when mosquito bites the heartworm positive dog and taking blood meal, the mosquito is taking the microfilaria also.

 This step is the first step.

 Then, after about 10-14 days, the microfilaria mature into infective larvae inside the mosquito body.

 This is the second step.

 The same mosquito bites your dog and transmit the heartworm larvae, and after 6 months, this larvae matures and becomes infective adult heartworm.

 In other word, it takes 6 months since the day your dog get bitten by heartworm positive mosquito to be a heartworm positive dog.

 It also means that it takes 6 months to be able to test for the heartworm microfilaria in your dog’s bloodstream.

 When we take Palette the Corgi to our vet for annual exam, we ask for Snap4Dx test which test for major tick disease and heartworm.

 Since our area is not the warm area where temperature stays above 57F days and nights all the time, we just give heartworm pill with extended period;every 45 days,and check heartworm every year.

 If we lived in the area where temperature is warm all the time, we may check her blood for once in 5-6 months probably.

 There is antigen test,which can detect microfilaria and adult heartworm both by taking blood sample from your dogs,but heartworm association says that the test can detect microfilaria and adult heartworm both consistently only after 7 months since the infection occurred.

 That being said, with common sense, without already infected mosquito around your dog, your dog cannot get heartworm.

 Therefore, researching the life of mosquito becomes important part of the decision as to when to start giving heartworm preventative pills and when to stop.

 According to Citadel Tibetan Mastiff website, heartworm larvae require 30 consecutive days of 60 F whether when temperature do not drop below 57F to reach the stage where mosquito becomes heatworm positive mosquito.

 Therefore, if one of the 30 days had below 57F temperature, the mosquito’s heartworm larvae cycle gets broken and it starts all over again.

 The Citadel Tibetan Mastiff website has USA map with average temperature of each state for you to determine when to start giving heartworm preventative and when to stop.

 To see the area map for heartworm at Citadel Tibetan Mastiff website,please click here.

 To read full article on heartworm life cycle at heartworm association,please click here.

 To protect your dogs from heartworm, vet suggests dog owners to give preventative pill monthly,but do you know how it works?

How heartworm preventative pill works?

 If you have pulled heartworm preventative medication information sheet out from the monthly preventative pills package, and read how it works, you know by now that this pill does not prevent the heartworm from occurring at all, but rather pills kill the already existing microfilaria to cut off the life cycle of heartworm larvae that was transmitted by heartworm positive mosquito.

Also, vet and preventative pill box may say to give monthly but, did you know that this 30 days rule was implemented for us to remember the frequency easily?

 In naurality, the pill is good for 45 days. That is why, I give Palette heartworm pill every 45 days.

 On the talk of monthly preventative pill for heartworm, this is where you have to know more about your dogs’ breed.

 Many heartworm pill’s active ingredient is medication called “Ivermectin” and, this drug can cause problems in some herding breed such as collies.

Ivermectin sensityvity in dogs..

 According to petside website, researchers first saw reaction in collies to ivermectin back in 1983.

 If you give enough of ivermectins, these ivermectin sensitive breeds like collies get reactions by drooling,stumbling,blindness,coma,respiratory problems etc.. at the dose of 1/200 dose of medication that would be enough to cause problems in other breed.

 You can read full article at petside website here.

 Washington University studied about this peculiar reaction to “iverectin” by collie and breeds that are related to collies and found out about mutation in the gene called MDR1 genes (Multi Drug Resistance gene) in the breed.

 These MDR1 gene forms the protein and help flashing out the drug from the brain. When these gene could not function as it should and could not help flashing out the drug from the brain, then,medication can build up in the brain and cause problems.

 If you have herding breed or have breed that are known to have mutant MDR1 gene, you should consult with your vet when surgeries and find the other option of drugs.

 Breeds known to have high rate of mutant MDR1 gene are collies,but some other breed are also being reported as well. To be sure whether your dog does have mutant MDR1 gene,you can test for it.

 Laboratory can test the DNA by cheek swab or blood sample with roughly 2 weeks wait.

 You can read more on how to test your dog for mutant MDR1 gene here.

 You can see the list of breed that has been reported to have mutant NDR1 gene here.

is a list of drugs that can cause problems for dogs with mutant MDR1 gene.
Some of them are not in the heartworm pills but other drugs such as
sedative drug (anesthesia).

** Anti parasite agent; ivermectin,selamectin, bilbemycin,moxidectin

** Tranquilizer/pre-anesthetic agent; Acepromazine

** Analgetic/pre-anesthetic agent; Butorphonol  

** Deworming agent; Emodepside

** Antibiotic; Erythromycin

** Anti-diarrhea agent found in imodium for example; Loperamide

** Chemotherapy drug agent; Vincristine,vinblastine,doxorubicin

 Incidentally, the other day, I was reading dog magazine and there was an article written by a vet on mutant MDR1 gene.

 In it, he wrote he did not know about this mutant MDR1 gene until his client brought a copy of paper about the mutant MDR1 gene and drugs that are known to cause problems in dogs with mutant MDR1 gene.

 I was under impression that dog health professional would know about those kind of things but it seems,not all vet knows about it.

 Therefore,if you have herding breed like collies or related breed to collies, I would encourage you to print out about the mutant MDR1 gene and drugs that are known to cause the problems in dogs with mutant MDR1 gene and pass it to your vet and let them know what drugs are bad for them.

 Sometimes, for dogs with mutant MDR1 gene, dosage used for other breed can be too much and reduced dosage or altered drugs can be recommended.


Dec 01, 2011 | 0 | Uncategorized

Leave a Reply