Case Descriptions of Virulent Systemic Feline Calicivirus

Meliasa Robinson

When should you suspect something more than the traditional FCV??

Feline Calicivirus is an important pathogen with regards to feline upper respiratory disease. When a relatively young cat is presented for upper respiratory systems (especially a kitten) the top two differentials are usually Feline Herpesvirus (FHV) and Feline Calivirus (FCV). You may consider also want to include Chlamydophila or Bordetella but they are not as common as the viruses. Both viruses involve some component of nasal discharge and sneezing, typical upper respiratory signs. FHV tends to have more of an ocular component including corneal ulcers, while FCV has more of an oral component with oral ulcers and may also present with concurrent limping. FCV may involve conjunctivitis but does not typically cause corneal ulcers like FHV. Based on signs you can usually differentiate the two pretty easily but if you are unsure running a PCR on nasal swabs or having virus isolation to differentiate the two are viable options. Keep in mind that PCR will be positive if the cat was vaccinated for FHV. FCV is usually treated symptomatically but many cats clear the virus on their own.

In a brief description FCV doesn’t sound that bad, it is highly contagious but not very fatal. So in an otherwise healthy kitten who gets good supportive are can be a good turnout. This is not the case with Virulent Systemic Feline Calicivirus (VSFCV). VSFCV is a severely virulent and contagious strain that results in significantly higher mortality rates than the traditional FCV, not to mention it does not discriminate between vaccinated and non-vaccinated pets (N.C. Pedersena, 2000). VSFCV is associated with more systemic signs such as involvement in the lungs and vascular system. It is important to differentiate early between VSFCV and traditional FCV as treatment needs to more aggressive and systemic in one versus the other. An epizootic of highly fatal FCV infection was described in the paper “An isolated epizootic of hemorrhagic-like fever in cats caused by a novel and highly virulent strain of feline calicivirus”. To better illustrate how severe VSFCV can be the index case and two of the severe resulting cases from the index will be described in detail. For a detailed account of the entire outbreak please see the paper.

In this epizootic there were a total of 7 cases. The index cat was a 4 month old shelter kitten brought in for severe upper respiratory signs on Sept 12th and spent a total of 40 days at the hospital for treatment. One of the veterinary assistant’s cats Ria, 6 year old female was brought in for a dental Oct 8th and returned four days later with signs of swelling and lethargy that eventually turned into crusting. Two other cats in Ria’s household, her sons Ari and Ian, which were not directly exposed to the hospital came up with signs similar to mom. Ari’s signs were first noted on Oct 19th; they were more severe and will be detailed further. Ian’s was brought in for signs on Oct 21st but eventually made a recovery. A client’s cat came into the hospital for castration on Oct 12 and like Ria returned 4 days later with signs of depression and lethargy that later turned into ulcerative lesions. A house mate of this cat came in Oct 16 for conjunctivitis and 2 weeks later had alopecia and crusty lesions similar to those of the other cats. Both cases made an uneventful recovery. The last case was the cat of a veterinary technician at the same hospital. That cat was brought in Nov 6th with signs but was ultimately euthanized Nov 9th due to a progressive decline. All the cases can be traced back to some contact or spread from the index case; also all cases were FELV and FIV negative. Only two cases had virus isolation of FCV which were determined to be the same strains.



The Index Case:

Female kitten from shelter, 4 months old with severe upper respiratory infection. The infection develops to crusty lesions on the face and oral vesicles. The kitten was treated for a total of 40 days before being well enough to be adopted. After adoption the kitten died 1 week later from intussuception.



Ria:

Ria, 6 year old female spayed domestic feline, strictly indoors vaccinated on the tenth of April with FPHCV. Ria was brought in on October 8th for a dental cleaning procedure. On Oct 12 Ria returned with lethargy, anorexia, fever, and slight swelling over the dorsal muzzle. Hair over the right side of muzzle was epilated revealing 5 mm erythematous patch with a dark center. Ria was sent home for observation but returned two days later with additional focal crusting, erythema epilation over right and left medial canthi and margins of pinnae. Ria also had diffuse cutaneous edema of the face extending down the limbs. A biopsy of the muzzle and pinna revealed multifocal neutrophilic/lymphoplasmacytic perivascular dermatitis, extensive ulceration, superficial dermal necrosis, with underlying vasculitis. No infectious organisms were cultured. Ris was treated with prednisone and antibiotics. Over the next couple of days her appetite was normal again, and her lesions were beginning to heal.




Ari:

Ari was the son of Ria, 3.5 year old neutered male indoor only, vaccinated on tenth of April with FPHCV. Ari was brought in on Oct 19th with history of acute lethargy, anorexia of two days with right forelimb lameness noted 2 days prior but had since resolved. Physical exam detected a fever, crusty lesion on lower lip. Ari was sent home for observation but returned on Oct 21st with diffuse facial edema, dehydration, anorexia, and central ulceration over muzzle and left pinna. Focal crusting lesions were also noted on lower and upper lips. Over the next two days Ari stayed afebrile had facial swelling, forepaw edema, and the ulcerative lesion had less exudative discharge. Ari was transferred to UC Davis VMTH on Oct 23. Blood work showed an elevation in bilirubin, a coagulopathy, moderate decrease in protein, and an increase creatine phosphokinase (CPK). FCV was isolated in cell culture from the blood and nasal samples taken. On Oct 24 Ari’s entire face became edematous, the lesions on his face coalesced to form large crusts on both sides of the muzzle, and his mucous membranes were icteric. A nasoesophageal feeding to was placed as Ari was still anorectic. On Oct 26th Ari was given 1 unit of blood and started on low heparin therapy to combat DIC. A blood analysis later that day still showed decreased HCT, hypoproteinemia, and increased ACT but Ari was alert and responsive. On Oct 27th he was given another unit of cross matched blood, he also had increased RR. Thoracocentesis yielded yellow transudate. On Oct 28th Ari was given a 3rd unit of blood and had a thoracostomy tube placed to continuously remove pleural fluid. Ari’s condition slowly declined and he died Nov 8th from complications of Pneumothorax, shock and arrest. FCV was recovered from blood and tissue samples post mortem.



These cases were reported in 1998, but VSFCV has been seen in some private practices since then. If VSFCV is suspected it is important to take extreme care and caution not to spread the virus to other felines in the clinic. Whatever exam is used for the suspect case should be bleached and closed for at least 24 hours (N.C. Pedersena, 2000). If the patient must be hospitalized an isolation ward should be devoted to that patient. If the resources are not available then the pet should be taken to a facility that can properly isolate. The main signs that will help point to VSFCV are edema of the face and limbs, crusty lesions over face, muzzle, and pinna, treatment is more chronic than with traditional FCV and lung involvement is a greater possibility.

Works Cited 

N.C. Pedersena, J. E. (2000). An isolated epizootic of hemorrhagic-like fever in. Veterinary Microbiology , 73, 281-300.