January 11, 2013 · 5:07 pm

Canine Respiratory Coronavirus: Part of the CIRD complex

Canine infectious respiratory disease (CIRD) is a complex, multi-factorial disease process of dogs. Previously named infectious tracheobronchitis (or more commonly, kennel cough), this disease is composed of numerous viral, bacterial and mycoplasmal organisms. In most cases more than one of these organisms is implicated in the infection.

The main viruses involved in CIRD include Canine Adenovirus Type 2 CAV-2), Canine Parainfluenza Virus (CPIV), Canine Influenza Virus (CIV), Canine Respiratory Coronavirus (CRCoV), Canine Distemper Virus (CDV), and Canine Herpesvirus (CH). The main bacterium involved is Bordetella bronchiseptica; however, Streptococcus equi subsp zooepidemicus has been implicated in a severe hemorrhagic pneumonia which may contribute to the disease complex. A mycoplasmal species (M.cynos) may be involved as well.

The purpose of today’s blog is to talk a bit more about CRCoV, one of the newer viruses implicated in the CIRD complex. This virus is genetically different from the canine enteric coronavirus that most practitioners may be more familiar with. In fact, this divergent strain is most similar genetically to bovine coronavirus. This virus was discovered in 2003 and is typically associated with more mild cases of CIRD and occurs during the early stages of the disease. Early infection with CRCoV may predispose dogs to other viral or bacterial pathogens, thus protentiating more serious respiratory disease. CRCoV has tropism for the upper respiratory tissues including the nares and trachea; however, infection can also be established in the lower airways. It has also been positively identified in rectal swabs but its role in enteric disease is unknown. CRCoV has been shown to be present in Europe, North America and Asia.

There is no specific treatment for CRCoV and spontaneous resolution is common. Most healthy dogs recover within 2 weeks without medical intervention. Co-infection with a number of other viruses and bacteria is common. For uncomplicated cases, antibiotics are generally not indicated, but for more severe cases (fever, lethargy, dyspnea, or progression of disease despite rest) antibiotics may be indicated to combat secondary bacterial pathogens. If bronchopneumonia, interstitial pneumonia or sepsis is suspected, IV antibiotics and hospitalization are indicated.

Dogs that are housed in shelters, kennels or high density housing situations are at a greater risk. Other risk factors include immunocompromise and stress.  Seasonality may play a role, as many infections are diagnosed in the fall and winter when outdoor temperatures are cooler. Age may also play a role with CRCoV infection, with dogs that are less than a year of age generally being seronegative for the virus, and dogs 1-9 years of age having an increased seroprevalence.

Supportive care is the best approach to CIRD and may include:

Hospitalization and fluid therapy: For animals with severe respiratory compromise, hospitalization may be required. In general, hospitalization is avoided due to the highly contagious nature of CIRD. If the animal is severely dyspneic, oxygen therapy is indicated, which must be delivered in a hospital setting. Many of these severely affected animals will be dehydrated and additionally require IV fluid therapy.

Antitussives: The evidence to support the use of antitussives for CIRD is lacking despite their regular use. Over the counter products are likely ineffective. Hydrocodone and butorphanol may provide some relief, but the risks of respiratory depression and reduced clearance of bacteria (secondary to decreased expectoration) need to be weighed against the benefits. In general, antitussives are not recommended for coughs due to an infectious cause unless quality of life issues are a concern.

Bronchodilators: are again often reported in the literature, but there is little to evidence of their effectiveness for CIRD.

Glucocorticoids: have also been used for reducing inflammation associated with cough. The use of these drugs is controversial as they can exacerbate disease, and the evidence to support their use is lacking.

Nebulizers: For dogs with excessive tracheal and bronchial secretions, aerosol therapy may be beneficial. Aerosols may help loosen respiratory secretions to facilitate expectoration. Aerosols can be composed of steam or saline, or can contain NSAIDs or antibiotics.

Contraindications: There are no studies that support the administration of intranasal vaccination in the face of infectious respiratory disease in the canine patient. Administering intranasal vaccinations to clinically ill patients is generally not recommended. Additionally, there are no approved or effective anti-viral products for the use in dogs with CIRD. Expectorant therapies (mucolytics) are also not recommended for routine use in CIRD patients as they have not been shown to be of benefit.

No vaccine is currently available for CRCoV and there is likely no cross protection from enteric canine coronavirus vaccines. This virus may be one of the reasons that traditional vaccines against kennel cough (which confer partial protection against CAV-2, CPIV, and Bordetella) are failing to work in certain situations.

~Heather

Further Reading:

  1. Ford RB. Canine Infectious Respiratory Disease. In: Greene CE. Infectious Diseases of the Dog and Cat (2012). 4. St Louis, Missouri, USA: Elsevier Saunders, 2012; 55-65
  2. Fenwick B. Evidence-based diagnosis, treatment, and prevention of canine infectious respiratory disease. North American Veterinary Conference (2008). January 19-23, 2008; Orlando, Florida, USA
  3. Erles K & Brownlie J. Canine respiratory coronavirus: an emerging pathogen in the canine infectious respiratory disease complex. Veterinary Clinics of North America: Small Animal Practice2008; 38(4): 815-825 [PubMed Abstract]
  4. Erles K, Toomey C, Brooks HW, et al. Detection of a group 2 coronavirus in dogs with canine infectious respiratory disease. Virology 2003; 310(2): 216-223 [PubMed Abstract]
  5. Mitchell JA, Brooks HW, Szladovits B, et al. Tropism and pathological findings associated with canine respiratory coronavirus (CRCoV). Veterinary Microbiology 2012; in press [PubMed Abstract]

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Filed under Repiratory, Virology

January 3, 2013 · 3:50 pm

Fever of Unknown Origin: Diagnostic Challenges and Therapeutic Trials

Fever of unknown origin is a frustrating condition in cats and dogs. Unfortunately, there are no specific guidelines for defining FUO in veterinary medicine, and no evidence based diagnostic or therapeutic recommendations when FUO exists. In cats, infections are the most common causes of FUO, whereas in the canine patient, FUO is commonly infectious, immune mediated or neoplastic. Most cases of FUO are due to unusual manifestations of common diseases. Thus, a thorough diagnostic approach is indicated, and when extensive in nature, the cause can often be determined.

In the study by Chervier et al, an average of 10 separate diagnostic tests was performed per canine patient with FUO. In 28% of the animals in that study, no final diagnosis was achieved. The mean time to reach a diagnosis in that study was approximately 11 days. This study was conducted at a referral center, but illustrates the point that clients must be made aware of the extensive diagnostics that may need to be undertaken, and that a final diagnosis may take a significant period of time to be ascertained (when it is achieved). Additionally, this process can be expensive. In another study by Battersby et al, the mean cost of investigation of FUO at a referral center in 2006 was £1434.50 (more than $2300 USD). Owners should be comforted by the fact that fever (unless severe) is rarely harmful to the patient, and that it is possible in many cases to achieve a diagnosis and treat/manage the disease.

In cases; however, where client or patient factors limit an extensive diagnostic process or where this process fails to produce a definitive diagnosis, therapeutic trials may be indicated.

Therapeutic trials include:

Antibiotic trials: This is the most common therapeutic trial. Antibiotic selection should be based on C&S results; however, when these are not available, a broad spectrum, combination antibiotic protocol that addresses anaerobic, aerobic, gram-positive, and gram-negative bacterial infections is typically indicated. Antibiotic resistance is the most common negative outcome associated with antibiotic therapeutic trials. Common protocols include a penicillin or cephalosporin combined with an aminoglycoside (use with caution in dehydrated animals) or a fluoroquinolone. If a rickettsial disease is suspected, doxycycline is the treatment of choice. If toxoplasmosis or neosporosis are suspected, clindamycin or sulfa drugs are generally used. If there is no response to an antibiotic trial within 72 hours of initiating medications, a second trial with different antibiotics that cover a different spectrum of bacteria can be instituted.

Antifungal trials: are generally only initiated if a systemic mycosis is suspected.

Anti-inflammatory/immunosuppressive trials: before starting immunosuppressive therapeutic trials it is of the utmost importance to have ruled out an underlying infectious disease, or severe exacerbation of disease which may result in death can occur. Glucocorticoid use can also interfere with diagnostic tests resulting in a delayed diagnosis. Owners must be warned about these possible negative aspects of a glucocorticoid therapeutic trial.  When glucocorticoids are employed, a dramatic improvement should be noted within 24-48 hours if FUO is immune-mediated. Initial improvements; however, do not necessarily correlate to successful resolution, as many conditions initially improve with steroids.

Antipyretic trials: In general, these should be reserved for animals who have a fever greater than 41°C (106°F) or whose quality of life is significantly affected by the fever. Fever has a physiological purpose and disrupting that mechanism may exacerbate or prolong disease; however, fevers greater than 41.1°C (106°F) are known to cause CNS damage, DIC and death. Cats are not as susceptible to this as dogs are. The most common antipyretic drugs are NSAIDs including meloxicam, ketoprofen, aspririn, carprofen, deracoxib, and firocoxib. Acetaminophen is commonly advocate, although it is not a true NSAID and is significantly toxic to cats. Its efficacy in dogs is largely unproven.

An important point: If the condition of the patient necessitates referral to a specialist, it is advised to discontinue all drug therapies for a minimum of 24 hours prior to referral in order to improve the time to diagnosis upon referral.

Want more information of FUO? Come visit us at IntuitiveVet and sign up for our beta test.

~Heather

Further Reading:

  1. Chervier C, Chabanne L, Godde M, et al. Causes, diagnostic signs, and the utility of investigations of fever in dogs: 50 cases. Canadian Veterinary Journal 2012; 53(5): 525-530 [PubMed Abstract]
  2. Battersby IA, Murphy KF, Tasker S, et al. Retrospective study of fever in dogs: laboratory testing, diagnoses and influence of prior treatment. Journal of Small Animal Practice 2006; 47(7): 370-376 [PubMed Abstract]
  3. Dunn KJ & Dunn JK. Diagnostic investigations in 101 dogs with pyrexia of unknown origin. Journal of Small Animal Practice 1998; 39(12): 574-580 [PubMed Abstract]
  4. Flood J. The diagnostic approach to Fever of unknown origin in cats. Compendium: Continuing Education for Veterinarians 2009; 31: 26-31 [PubMed Abstract]
  5. Flood J. The diagnostic approach to Fever of unknown origin in dogs. Compendium: Continuing Education for Veterinarians 2009; 31: 14-21 [PubMed Abstract]

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Filed under Polysystemic

December 21, 2012 · 10:31 am

West Coast Vets….Is Salmon Poisoning on Your Radar?

I lived and worked on Canada’s West Coast for 4 years, and I’ve got a confession; I had never heard of Salmon Poisoning Disease (SPD). It wasn’t until I was doing research for IntuitiveVet that I came across this disease and wondered, “Why wasn’t Salmon Poisoning on my radar?” It should have been, and for that reason I decided to write about it, in hopes that it increases awareness of this life-threatening, but treatable disease for my BC (and West Coast) friends.

Every fall, we’d visit GoldstreamPark (just outside of Victoria, BC) to watch the incredible Salmon Run. It’s an amazing thing to see (and smell!); hundreds of thousands of salmon, swimming upstream to spawn and then die. The banks of the river were littered with carcasses. In retrospect, I wonder how many of these were carrying the causative organism of SPD (Neorickettsia helminthoeca)? And how many dogs got into those dying fish for a snack and an unexpected illness?

SPD is a rickettsial infection of dogs caused by Neorickettsia helminthoeca, which is transmitted by the helminth vector, Nanophytes salmincola. This disease is associated with ingestion of raw fish on the Pacific coast of Canada and northwestern United States. Snails, fish and mammals or birds are required for the trematode to complete its life cycle and thus all must be present in the environment for the disease to persist.  Larvae leave the snail, enter the fish and are then ingested by mammals and birds that feed on the fish. Most animals have subclinical infections; however, dogs and wild canids appear to be end-stage hosts and become severely ill and often die after infection. Cats are not clinically affected.

In dogs, the infection begins in the intestines and then spreads hematogenously throughout the body. The actual mode by which the organism causes death is unknown; however, GI hemorrhage is characteristic and secondary bacterial infections and sepsis are common.

Clinical signs usually develop 5 to 7 days after eating raw fish but can occur later. Inappetance or anorexia is a common presenting complaint. Most dogs are depressed. These signs are due to a markedly elevated body temperature. Weight loss, diarrhea and vomiting may also be present. Another common complaint is increased thirst. Some animals show neurological signs.

The disease is diagnosed via fecal examination (looking for the eggs of the trematode vector, N. salmincola) and cytology of lymph node aspirates (looking for intracytoplasmic rickettsial organisms). PCR testing is also available and can be performed on rectal swabs or lymph node aspirates.

Affected animals require hospitalization and should be treated with doxycycline (which is considered to be the treatment of choice) and clinical signs begin to improve within 24-72 hours. Animals with secondary sepsis may require extensive care. Praziquantel is often given in addition to doxycycline to eliminate the fluke from the body.

Keeping dogs from feeding on raw fish is a key preventative measure. Smoking the salmon does not kill the organism. Fish must be well cooked or deep frozen.

So for those of you on the West Coast of Canada and the USA, it’s time to add another question to your arsenal when you’re obtaining a history. “Has your dog gotten into raw fish or salmon in the last few weeks?”

~Heather

PS: I’d love to hear from you. Have any of you working in BC, Washington, Oregon or California seen any cases of SPD in your practices?

Further Reading:

  1. Sykes JE, Marks SL, Mapes S, et al. Salmon poisoning disease in dogs: 29 cases. Journal of Veterinary Internal Medicine 2010; 24(3): 504-513 [PubMed Abstract]
  2. Headley SA, Scorpia DG, Vidotto O, et al. Neorickettsia helminthoeca and salmon poisoning disease: A review. The Veterinary Journal 2011; 187: 165-173 [PubMed Abstract]
  3. Johns JL, Strasser JL, Zinkl JG, et al. Lymph node aspirate from a California wine-country dog. Veterinary Clinical Pathology 2006; 35(2): 243-246 [PubMed Abstract]

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Filed under Gastroenterology, Polysystemic

December 19, 2012 · 8:39 pm

Histoplasmosis: Evidence For a More Cost-Effective Treatment

If you don’t live in an endemic area for histoplasmosis infection, than this post may not be terribly interesting, but did you know that histoplasmosis has been diagnosed in parts of Canada and a large part of the USA? Histoplasmosis was recently treated here in PEI in 2007 in a dog from NB, so wherever you are, it should be on your radar.1

The reason for today’s post is to talk about treatment options for histoplasmosis. In case you need a refresher, this disease can cause a systemic fungal infection in dogs, cats and people. The organism lives in the soil and grows in warm, moist, humid climates. Histoplasmosis is an uncommon condition, but is the second most common systemic fungal disease in cats (cryptococcosis is the most common). Animals in contact with soils contaminated by bat and bird feces are at a greater risk of infection. Potted plants and unfinished basements may serve as a source of infection for animals that are housed exclusively indoors.2 People can also be infected with this organism. There is no known direct transmission from infected animals to people, thus animals serve as sentinels for the presence of the organism in the environment.

The treatment of choice is itraconazole, which brings us to the point of today’s topic. While itraconazole is widely considered to be the most appropriate therapeutic approach, it is an expensive drug and some clients simply cannot afford it. In the past, when costs were an issue, ketoconazole was recommended. The issue is that ketoconazole can have side effects (especially in cats) and the evidence does not show it to be very effective in clearing histoplasmosis. The mindset has traditionally been that ketoconazole is better than nothing (or than euthanasia). But new research exists that shows another possible alternative for cats. Again, this is not disputing itraconazole as the treatment of choice, but rather when itraconazole is too expensive, or if it is causing severe drug reactions, fluconazole may be just as good. The study, by Reinhart et al, found that of the 30 cats treated for histoplasmosis with either itraconazole (n=13) or fluconazole (n=17) that there was no significant difference in terms of outcome or recurrence of disease.2 Costs of treatment; however, were significantly different. Itraconazole costs for one month were $212.85 versus fluconazole costs of $18.60. Considering that this disease is typically treated for a minimum of 4-6 months (and in some cases upwards of a year) this can add up quickly! While the drug has not been evaluated similarly in dogs (an isolated case study exists where fluconazole was used when side effects from itraconazole were too severe)3, it might be an alternative worth considering for clients that simply can’t afford itraconazole (considering that the drug is dosed by body weight, it can cost more than $1000 to treat a medium to large-sized dog on a monthly basis). It’s great to see research out there that can be helpful for the average client and that can help save them money. In the tough economic times that we are in, owners are more frequently electing to euthanize pets with treatable diseases due to the high costs of diagnostics and therapeutics. If we can prevent this from happening, we should, and the result of this study may help to do just that!

~Heather

Further reading:

  1. Tyre E, Eisenbart D, Foley P, et al. Histoplasmosis in a dog from New Brunswick. Canadian Veterinary Journal 2007; 48(7): 734-736 [PubMed Abstract]
  2. Reinhart JM, KukanichKS, Jackson T, et al. Feline histoplasmosis: fluconazole therapy and identification of potential sources of Histoplasma species exposure. Journal of Feline Medicine and Surgery 2012; 14(12): 841-848 [PubMed Abstract]
  3. Clemans JM, Deitz KL, Riedesel EA, et al. Retroperitoneal pyogranulomatous and fibrosing inflammation secondary to fungal infections in two dogs. Journal of the American Veterinary Medical Association 2011; 238(2): 213-219 [PubMed Abstract]
  4. Brömel C & Sykes JE. Histoplasmosis in dogs and cats. Clinical Techniques in Small Animal Practice 2005; 20(4): 227-232 [PubMed Abstract]
  5. Aulakh HK, Aulakh KS & Troy GC. Feline histoplasmosis: a retrospective study of 22 cases (1986-2009). Journal of the American Animal Hospital Association 2012; 48(3): 182-187 [PubMed Abstract]

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Filed under Polysystemic

December 12, 2012 · 10:12 am

A Few Tips on Preventing Post-Operative Infections in Orthopedic Patients.

I’ve just finished up the orthopedic system updates for IntuitiveVet, and wrote up a section on orthopedic surgery prophylaxis. While most of it was intuitive and taught during veterinary college, there were a couple of “aha” moments that I stumbled upon that I thought I’d share with you.

Firstly, the benefit of using prophylactic antibiotics must be weighed against the risks of creating antimicrobial resistance, adverse reactions (including diarrhea) and drug costs. Several studies have shown a protective effect against post-operative infections associated with orthopedic surgery when prophylactic antibiotics are used. In general, prophylaxis is not indicated for clean procedures; however, there are some patients that should receive prophylactic antibiotics during clean orthopedic surgeries, which include:

  • Animals undergoing procedures with bone incision or extensive soft tissue dissection
  • Animals undergoing procedures with medical implants
  • In patients or in locations where an infection would be catastrophic
  • In high risk patients (concurrent systemic disease or infection, immunosuppression)
  • Animals undergoing  surgeries that are longer than 90 minutes

Patients with clean contaminated to dirty surgeries should all receive prophylactic antibiotics (and in some cases, therapeutic antibiotics). For maximum effect IV administration 20-30 minutes prior to surgery is recommended and then continued every 90-120 minutes during the surgical procedure. Cefazolin is the most commonly prescribed antibiotic for orthopaedic prophylaxis.

Secondly, antibiotic prophylaxis may be the least important aspect of prevention of post-operative infection. Here are some other factors to consider:

Aseptic technique: This may seem like a no-brainer, but so often we fail at one or more aspects of this. Stringent asepsis during surgery is necessary to prevent contamination. This requires that surgical implants and surgical instruments be autoclaved properly (cold sterilization is not adequate), surgical garb including cap, mask and gown should be worn, and proper cleaning and surgical scrubbing of hands prior to surgery with gloving (optimally double gloving) needs to be performed. Patients need to be adequately prepared for surgery with clipping cleaning and disinfecting. Clipping should occur after induction, as clipping prior to induction is associated with increased infection rates (This was an “Aha!” moment for me). Patients should be draped with large overhanging drapes and care taken to prevent strike-through on the drapes.

Bandaging: Should be performed for a period of approximately 24-48 hours post-operatively to reduce contamination of the incision site. After that time there is little benefit in bandaging and the bandage can result in complications if left on long term (with the exception of open wounds which may require extensive bandaging and bandage changes). Bandage changes should be performed in an aseptic manner. Elizabethan collars are advised to prevent post-surgical self-trauma and licking by the patient which may promote infection.

Analgesia: Orthopedic surgeries are associated with significant post-operative pain.  Post-operative pain is associated with increased infection rates. Analgesia is required and should be multimodal in its approach. The use of pre- and intra-operative analgesia is desirable and includes epidurals, CRIs, premedications, opiates, NSAIDs and various other drugs.

Antibiotic impregnated implants: may help to prevent biofilm formation and post-operative infection after orthopedic surgery. In one study by Huneault et al, the use of ciprofloxacin impregnated implants resulted in prevention of experimental induction of osteomyelitis compared to control animals.

Weight management: Increased body weight has been associated with a poorer outcome and increased infection rates after orthopedic procedures in dogs.  Given this information, and the fact that exercise needs to be restricted, caloric reduction is required in order to maintain current weight or to promote weight loss.

Post-operative antibiotic use: In one study by Fitzpatrick et al, it was determined that the use of post-operative antibiotics after orthopedic surgery significantly reduced the rate of surgical site infections in dogs. Post-operative antibiotics for clean surgeries are typically contraindicated as they can result in resistance, adverse effects and increased and unnecessary costs. While a protective effect was noted, the use of post-operative antibiotics is likely not indicated except for select cases. It should be noted that the use of antibiotics post-operatively can result in resistance in cases where infections do occur, thus making these infections more challenging to treat.

No one likes to encounter post-operative infections, especially in orthopaedic patients, as disastrous results can ensue; however, it is impossible and impractical to attempt to achieve a 0% post-operative complication/infection rate. The goal should be to minimize those events using the above recommendations.

~Heather

Further Reading:

  1. Whittem TL, Johnson AL, Smith CW, et al. Effect of perioperative prophylactic antimicrobial treatment in dogs undergoing elective orthopedic surgery. Journal of the American Veterinary Medical Association 1999; 215(2): 212-216 [PubMed Abstract]
  2. Wosar M. Preventing infection in orthopedic Surgery. North American Veterinary Conference (2007). January 13-17, 2007; Orlando, Florida, USA
  3. Fitzpatrick N & Solano MA. Predictive variables for complications after TPLO with stifle inspection by arthrotomy in 1000 consecutive dogs. Veterinary Surgery 2010; 39(4): 460-474 [PubMed Abstract]
  4. Huneault LM, Lussier B, Dubreuil P, et al. Prevention and treatment of experimental osteomyelitis in dogs with ciprofloxacin-loaded crosslinked high amylose starch implants. Journal of Orthopaedic Research 2004; 22(6): 1351-1357 [PubMed Abstract]
  5. Weese JS. A review of post-operative infections in veterinary orthopaedic surgery. Veterinary Comparative Orthopaedics and Traumatology 2008; 21(2): 99-105 [PubMed Abstract]
  6. Nelson LL. Surgical site infections in small animal surgery. Veterinary Clinics of North America: Small Animal Practice 2011; 41(5): 1041-1056 [PubMed Abstract]

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Filed under Musculoskeletal

December 6, 2012 · 11:51 am

L-Lysine for FHV-1: Is it all it’s cracked up to be?

I have to admit that while doing research for IntuitiveVet’s Feline Herepesvirus section, I was disappointed to discover that L-lysine may not be as beneficial as I had touted it to be to my clients. I honestly thought that L-lysine was a savior for my feline herpes patients and I espoused its many virtues (including reduced viral replication and reduced frequency or severity of outbreaks) when prescribing it. It turns out that I may have been wrong.

In a review of the literature, I was not able to find convincing proof for L-lysine’s use for FHV-1 patients. In fact, one expert (Gould) went so far as to say that,

“There is no evidence of the benefit of dietary L-lysine supplementation, and its addition may paradoxically increase disease severity and viral shedding.”1

Wow! I was stunned. Not only, was I finding out that L-lysine may not help, but in some situations it may make things worse. Gould went on to summarize several studies and found that the only papers that supported the use of L-lysine were small studies with low patient numbers. One clinical trial with 8 cats (which was designed as a randomized, blinded, placebo controlled study, albeit with only 4 cats in each group) did find that L-lysine reduced clinical signs; however, the L-lysine was given to the cats before infection with FHV-1.2 In clinical practice we tend not to use lysine this way. We tend to give it to cats after they have already been infected and showing clinical signs. Gould reported one other small study that showed that viral shedding was reduced but no impact on clinical signs had been noted.

And then came the bad news. The next three studies that Gould reported all indicated that the L-lysine either had no effect in reducing viral shedding or clinical signs, or even worse, that L-lysine had actually increased the severity of disease and DNA detection rates! One of those studies was done by Maggs et al in 2007.3 He and his team found that the mean disease score for cats fed L-lysine supplemented diet was actually higher than those fed a placebo diet. These results were confirmed in a 2009 study. Both of these studies; however, were not representative of the general feline population (as the first was conducted in an experimental colony and the other took place in a shelter situation).

Interestingly, Maggs and many other experts still advocate the use of L-lysine despite the lack of definitive proof. These experts typically recommend dosages of 400-500 mg total dose PO q12-24 on an as needed or indefinite basis.  Additionally, Maggs advises giving lysine as a bolus (and not mixed into food) at a dose of 500 mg total PO q12h for client-owned animals. 4,5 Bolusing overcomes the requirement for the cat to eat the food, and as appetite tends to decrease when viral symptoms are at their worst, this may explain some of the poor study outcomes. It should be noted; however, that bolusing shelter cats is ill-advised as the added stress of medicating these animals may exacerbate clinical symptoms and spread disease and for this reason the use of L-lysine in shelter situations is controversial. 4,5

So, I guess the jury is still out on this one. Like so many aspects of veterinary medicine, the evidence for the use of L-lysine in FHV-1 patients is lacking. This is another example or where sound clinical judgement applied on a case-by-case basis is a necessity in determining whether or not to prescribe L-lysine to your FHV-1 patients.

 

~Heather

 

Further Reading:

  1. Gould D. Feline herpesvirus-1: ocular manifestations, diagnosis and treatment options. Journal of Feline Medicine and Surgery 2011; 13(5): 333-346 [PubMed Abstract]
  2. Stiles J, Townsend WM, Rogers QR, et al. Effect of oral administration of L-lysine on conjunctivitis caused by feline herpesvirus in cats.American Journal of Veterinary Research 2002; 63: 99-103 [PubMed Abstract]
  3. Maggs DJ, Sykes JE, Clarke HE, et al. Effects of dietary lysine supplementation in cats with enzootic upper respiratory disease. Journal of Feline Medicine and Surgery 2007; 9(2): 97-108 [PubMed Abstract]
  4. Maggs DJ. Antiviral therapy for feline herpesvirus infections. Veterinary Clinics of North America: Small Animal Practice 2010; 40(6): 1055-1062 [PubMed Abstract]
  5. Maggs DJ. Diagnosis and Treatment of FHV-1 Infections. North American Veterinary Conference (2012). January 14-18, 2012; Orlando, Florida, USA

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Filed under Virology

December 4, 2012 · 12:03 pm

Canine Herpesvirus: It’s Time to Start Looking!

Every one of us in the veterinary profession is familiar with feline herpesvirus. This nasty virus is ubiquitous in the environment and affects kittens and cats throughout the world with severe upper respiratory and ocular signs. In some cases these infections are life threatening. Most of us do not have its cousin, canine herpesvirus, on our radar, and we should. Canine herpesvirus is genetically related to feline herpesvirus and causes respiratory, ocular, urogenital and systemic disease in dogs. It is most known for it severe and often fatal manifestation in neonates, in which a severe hemorrhagic disease results, but this is relatively uncommon and mostly isolated to breeding facilities.

Perhaps more importantly, are its ophthalmic signs. Conjunctivitis is extremely common in dogs, and often an underlying cause cannot be determined. This may be one of those case; however, where not looking for something, means not finding it. Conjunctivitis and ulcerative keratitis have both been associated with primary CHV infection in dogs.

On physical examination, blepharospasm, conjunctivitis, mucoid to mucopurulent ocular discharge, keratitis (ulcerative or non-ulcerative) and dendritic ulcers may be present.  Conjunctivitis is the most common finding and is often bilateral. Conjunctival petechiation may be present and is highly suggestive of CHV associated conjunctivitis. Dendritic ulcers are also highly suggestive of this condition many of which have club-shaped terminal end-bulbs. Generally, ocular lesions are self-limiting in immunocompetent animals; however, Immunocompromised animals can exhibit severe ocular lesions.

In these patients, a full ophthalmic exam is indicated, including Schirmer tear testing, fluorescein dye staining, tonometry, direct/indirect ophthalmascopy, and conjunctival scrapings or swabs to submit for PCR testing. CHV is readily diagnoses via PCR testing. Currently, the most sensitive and specific method for detecting CHV DNA is a probe-based real-time PCR.

In general, there is no effective known treatment for CHV, and symptomatic and supportive care is indicated, but this is not the case with ocular CHV infection.  Cidofovir and trifluridine topical antiviral ophthalmic preparations have both been shown to be effective.

It’s high time we stop practicing medicine based on hunches and start practicing based on the evidence.  Throwing broad spectrum antibiotic preparations at our patients with conjunctivitis without appropriate diagnostics, is likely a disservice. Swabbing for CHV in canine conjunctivitis patients is valuable and will give us more information about the prevalence of this disease. In addition, knowing that your patient is affected with CHV is important, even if the signs are mild. CHV can lead to serious symptoms in immunocompromised, stressed and debilitated animals, and like all herpesviruses can remain latent in the body for the life of the patient. Thus it is critical to identify these animals and mark their records as CHV-infected to optimize patient health, provide appropriate future treatment options, and improve client education.

If we don’t start looking for CHV, we’re never going to find it. Happy swabbing!

~Heather

Further Reading:

  1. Gervais KJ, Pirie CG, Ledbetter EC, et al. Acute primary canine herpesvirus-1 dendritic ulcerative keratitis in an adult dog. Veterinary Ophthalmology 2012; 15(2): 133-138 [PubMed Abstract]
  2. Evermann JF, Ledbetter EC & Maes RK. Canine reproductive, respiratory, and ocular diseases due to canine herpesvirus. Veterinary Clinics of North America: Small Animal Practice 2011; 41(6): 1097-1120 [PubMed Abstract]
  3. Ledbetter EC, Kim SG, Dubovi EJ, et al. Experimental reactivation of latent canine herpesvirus-1 and induction of recurrent ocular disease in adult dogs. Veterinary Microbiology 2009; 138(1-2): 98-105 [PubMed Abstract]
  4. Decaro N, Martella V & Buonavoglia C. Canine adenoviruses and herpesvirus. Veterinary Clinics of North America: Small Animal Practice 2008; 38(4): 799-814 [PubMed Abstract]
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