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The profound dermatological manifestations of COVID-19 Part VI: Going to the dogs


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By Warren R. Heymann, MD
July 29, 2020
Vol. 2, No. 30

Disclaimers: This commentary was written on July 12, 2020 for a publication date of July 29, 2020. The issues related to the COVID-19 pandemic are changing rapidly. The content included in this commentary may no longer be factual or relevant by the publication date. The reader is encouraged to stay abreast of developments via the CDC and local government and institutional health care authorities. The AAD has instituted the valuable resource “Protecting your patients and practice during the COVID-19 outbreak.”

Compare your life now to what it was like six months ago. Could you ever have envisioned wearing masks for every patient encounter? Having your front desk staff behind plexiglass shields? Texting patients, informing them in their car that they are ready to be seen? Unquestionably your personal life has been upended and altered. When our Iceland adventure was canceled, my wife and I realized that, in all probability, we will not be traveling for some time. We are not alone in realizing that this is the perfect time to adopt a pet. Meet Marti — our Cockapoo puppy (age 9 weeks in the image)!

Dr. Heymann and his new puppy, Marti.

Even if you are not a dog lover, inevitably many of your patients are. This commentary will be divided in three sections: 1) What every dermatologist must know; 2) Current issues in canine dermatology; and 3) Canines and COVID-19.

What every dermatologist must know. Dogs can ingest medication by licking the sites where the medication was applied (I love when Marti gives me kisses!), licking their fur if the owner inadvertently transferred the medication, or by biting the ointment tube. This is vitally important for patients with actinic keratoses treated with topical 5-fluorouracil (5-FU) and psoriatic patients prescribed calcipotriene. (1) In humans, toxicity from oral ingestion of 5-FU is characteristically related to bone-marrow suppression; in dogs the most common severe effects are seizures and vomiting. Of 72 cases of fluorouracil toxicity reported to the Animal Poison Control Center, the onset of signs was usually within 30 minutes of ingestion; death occurred as quickly as within 7 hours; 66 of the 72 dogs eventually died. (2) Within 24 to 72 hours of calcipotriene ingestion, dogs may exhibit anorexia, hematemesis, diarrhea, polydipsia, polyuria, depression, and weakness. Hypercalcemia can lead to renal failure and soft tissue mineralization. (1)

Current issues in canine dermatology. The subspecialty of veterinary dermatology is as advanced (perhaps even more so — read on) than the human counterpart. The progress is summarized in the delightful reflections of Danny Scott, who looked back on his career in researching canine health, upon receiving a Lifetime Achievement Award from the Kennel Club Charitable Trust. As he stated, 45 year ago, there was “no food allergy, autoimmune dermatoses, or Malassezia dermatitis; no lasers.” (3)

There are approximately 300 board-certified veterinary dermatologists worldwide. The American College of Veterinary Dermatology (ACVD) confers diplomate (board certification) status in veterinary dermatology by requiring completion of a 2-3 year approved residency training program, an original research project, publication in a scientific journal, and successful completion of the certification examination.

A perusal of recent canine dermatological literature is most impressive. The following is a sampling of some hot topics in the discipline published this year.

Canine atopic dermatitis has been defined by the ACVD task force as a genetically predisposed inflammatory and pruritic allergic skin disease with characteristic clinical features, most commonly associated with IgE antibodies to environmental allergens. (4) While we anxiously await newer treatments for atopic dermatitis in our patients who are unresponsive to standard therapy, I was dumbfounded to learn of the availability for JAK1 inhibition with oclacitinib (Apoquel) and the anti-IL-31 monoclonal antibody lokevetmab (Cytopoint), both of which have positive effects on skin barrier parameters. (5)

Malassezia pachydermatis is associated with ceruminous otitis externa and a “seborrheic” dermatitis. Although treatment is usually with topical or systemic azoles, emerging azole resistance due to mutations or quadruplication of the ERG11, have increased interest in alternative antifungal agents, such as chlorhexidine and various essential oils. (6) Demodex mites can live in the skin either as a harmless commensal organism or as a pathogenic agent. In dogs, generalized demodicosis often associated with immunosuppression caused by disease or therapy. Generalized demodicosis (GD) is potentially life-threatening, due to septicemia from secondary severe deep pyoderma; euthanasia is often considered due to poor treatment response and/or incurable infestations. (7) According to our expert, Dr. Kathryn Rook, isoxazolines (which are common flea and tick preventatives) successfully treat dogs with GD.

My late parents adopted a beautiful Wire Fox Terrier (named Perry) when they became empty-nesters. My mother told me that he developed lupus and was placed on steroids. When visiting, I looked at Perry and told my mother “If Perry was human, I would have diagnosed him with pemphigus. Please ask the vet when you go back.” Two weeks later, my mother called to tell me that yes, Perry, did indeed have pemphigus. When my mother asked the vet why he did not tell her that in the first place, he responded, “People heard of lupus — nobody knows about pemphigus — I use the same steroids anyway, so I just say the dog has lupus.” I will not comment further other than acknowledging that the field has come a long way. Although it is an uncommon disease, pemphigus foliaceus is probably one of the most common cutaneous autoimmune canine diseases. Most cases display autoantibodies directed against desmocollin-1 with a minority of cases against desmoglein-1. Standard therapy is with steroids and other immunosuppressive agents; a Bruton’s tyrosine kinase inhibitor may have beneficial effects. (8). I was surprised that in my PubMed search I did not find reports of utilizing rituximab — Dr. Rook informed me that rituximab, as a human monoclonal antibody, is risky in dogs. Studies in dogs have also shown that it is not as effective in depleting B-cells as in humans.

Canines and COVID-19. Please read the following abstract by Sit et al: “SARS-CoV-2 emerged in Wuhan in December 2019 and caused the pandemic respiratory disease, COVID-19. In 2003, the closely related SARS-CoV had been detected in domestic cats and a dog. However, little is known about the susceptibility of domestic pet mammals to SARS-CoV-2. Two out of fifteen dogs from households with confirmed human cases of COVID-19 in Hong Kong SAR were found to be infected using quantitative RT-PCR, serology, sequencing the viral genome, and in one dog, virus isolation. SARS-CoV-2 RNA was detected in a 17-year-old neutered male Pomeranian from five nasal swabs collected over a 13-day period. A 2.5-year-old male German Shepherd dog had SARS CoV-2 RNA on two occasions and virus was isolated from nasal and oral swabs. Both dogs had antibody responses detected using plaque reduction neutralization assays. Viral genetic sequences of viruses from the two dogs were identical to the virus detected in the respective human cases. The animals remained asymptomatic during quarantine. The evidence suggests that these are instances of human-to-animal transmission of SARS-CoV-2. It is unclear whether infected dogs can transmit the virus to other animals or back to humans.” (9)

I will conclude on an optimistic note. The charity Medical Detection Dogs is working with the London School of Hygiene and Tropical Medicine to intensively train dogs to detect COVID-19 by having the dogs detect the odor of the virus. If successful, this could provide a rapid, noninvasive screen at airports (or elsewhere) with subsequent standard confirmation. (10) Research in this endeavor is also performed at Penn Vet.

Point to Remember: With the pandemic, more people are adopting dogs and other pets. Regarding the SARS-CoV-2 virus itself, much remains to be learned about the relationship between the virus, humans, and their best friends.

Our expert's viewpoint

Kathryn A. Rook, VMD
Diplomate, American College of Veterinary Dermatology

Many scientists believe that the novel coronavirus, SARS-CoV-2, originated from either bats or pangolins in China. (11, 12) And while we know that this virus is zoonotic in origin, as veterinarians, we are often asked how this virus can impact our pets and our interactions with pets at home. Fortunately to date, according to the United States Department of Agriculture (USDA), there have been very few domesticated animals that have been reported to have been infected with SARS-CoV-2 (13) and even fewer with clinical signs. (Because of my particular interest as a veterinary dermatologist, I am not aware of any reports of infected animals with dermatologic signs.) With this knowledge, pets are not believed to play a major role in transmission of this particular coronavirus to humans. What is more likely is that infected humans are transmitting this virus to the animals with which they come in contact. Why some pets and animals become infected and develop clinical signs is not yet clear. However, the few cats that have developed clinical signs have been reported to have respiratory signs. Pet owners should be aware that if they contract COVID-19, they should isolate themselves from their pets (and other humans) to minimize the risk of transmission to animals in their home. If their pets do become ill, they should have their pet evaluated by a veterinarian, but should have a healthy individual bring their pet to the veterinary hospital. Excellent resources exist for pet owners including the Center for Disease Control COVID-19 website which has entire section on “Pets & Other Animals” (14) and the Worms and Germs Blog from the Ontario Veterinary College which is also a resource for other zoonotic diseases of pets. (15)

  1. Asad U, Boothe D, Tarbox M. Effect of topical dermatological medications in humans and household pets. Proc (Bayl Univ Med Cent). 2019;33(1):131-132.

  2. Snavely NR, Snavely DA, Wilson BB. Toxic effects of fluorouracil cream ingestion on dogs and cats. Arch Dermatol 2010; 146: 1195-1196.

  3. Scott DW. Looking back on 45 years of canine dermatology. Vet J 2020;257:105438

  4. Flanagan S, Schick A, Lewis TP. A pilot study to identify perceived barrier and motivating factors of primary veterinarians in the USA for specialty referral and management of atopic dermatitis with allergen-specific immunotherapy [published online ahead of print, 2020 May 16]. Vet Dermatol. 2020;10.1111/vde.12862. doi:10.1111/vde.12862

  5. Marsella R, Ahrens K, Wilkes R, Trujillo A, Dorr M. Comparison of various treatment options for canine atopic dermatitis: a blinded, randomized, controlled study in a colony of research atopic beagle dogs [published online ahead of print, 2020 Apr 17]. Vet Dermatol 2020;10.1111/vde.12849.

  6. Guillot J, Bond R. Malassezia Yeasts in Veterinary Dermatology: An Updated Overview. Front Cell Infect Microbiol 2020;10:79. Published 2020 Feb 28. doi:10.3389/fcimb.2020.00079

  7. Foley R, Kelly P, Gatault S, Powell F. Demodex: a skin resident in man and his best friend [published online ahead of print, 2020 Apr 15]. J Eur Acad Dermatol Venereol. 2020;10.1111/jdv.16461. doi:10.1111/jdv.16461

  8. Goodale EC, Varjonen KE, Outerbridge CA, Bizkova P, et al. Efficacy of a Bruton's Tyrosine Kinase Inhibitor (PRN-473) in the treatment of canine pemphigus foliaceus [published online ahead of print, 2020 Jan 3]. Vet Dermatol. 2020;10.1111/vde.12841. doi:10.1111/vde.12841

  9. Sit THC, Brackman CJ, Ip SM, Tam KWS, et al. Infection of dogs with SARS-CoV-2 [published online ahead of print, 2020 May 14]. Nature. 2020;10.1038/s41586-020-2334-5. doi:10.1038/s41586-020-2334-510.

  10. Mills G. Sniffing out Covid-19 BMJ Vet Record 2020 http://dx.doi.org/10.1136/vr.m1753

  11. Wu D, Wu Tiantian, et al. The SARS-CoV-2 outbreak: What we know. Int J Infect Dis 2020; (94): 44-48.

  12. Wang H, Li, X, et al. The genetic sequence, origin, and diagnosis of SARS-CoV-2. Eur J Clin Micro Inf Dis 2020.

  13. USDA (2020, July 16) Confirmed Cases of SARS-CoV-2 in Animals in the United States. Retrieved from https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/sa_one_health/sars-cov-2-animals-us

  14. CDC (2020, June 24) Coronavirus Disease 2019, Pets and other Animals. Retrieved from https://www.cdc.gov/coronavirus/2019-ncov/animals/pets-other-animals.html

  15. Weese S. 2020, April 24. Commentary for owners: Risk of COVID-19 from pets. Retrieved from https://www.wormsandgermsblog.com/files/2020/04/OVMA-risk-of-COVID-19-from-pets-20200424.pdf


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