Case Report: Parvovirus

This case report was written by NJVTA member Tina DeVictoria, BS, CVT.   She is employed by The Animal Hospital at Kingston and Blawenburg.

This was previously printed in the May/June 2012 NAVTA Journal.

SIGNALMENT

            Charlie: 8 week old male mix-breed dog, 2.9kg, June 1, 2011, from log #3.

PRESENTING COMPLAINT/HISTORY

            Charlie was a new pet and was brought home 2 days prior to presentation. He presented with a 24 hour history of vomiting, watery diarrhea, and lethargy. He received a DA₂PP vaccine 7 days prior as well as a deworming treatment with pyrantel pamoate.

PHYSICAL EXAM FINDINGS/OBSERVATIONS

            On physical exam his abdomen was uncomfortable with fluid-filled small bowel loops, his muscle mass was poor, he was dehydrated, and there was a small amount of flea dirt present.

PROBLEM LIST/DIFFERENTIAL DIAGNOSIS

            Charlie’s problem list includes dehydration, lethargy, vomiting, and diarrhea. His differentials were intestinal parasitism, viral disease such as parvovirus, dietary indiscretion, or foreign body obstruction.

DIAGNOSTIC APPROACH

            The diagnostics began with an in-house ELISA test for parvovirus. The test indicated a strong positive, although at the time we could not rule out a false positive due to his vaccination 7 days prior. We proceeded with in-house bloodwork, including a 12-panel chemistry, CBC/differential and electrolytes. Charlie’s chemistry panel was normal, but his CBC showed leukocytosis with a white blood cell count of 19.26 K/µL (normal 5.5 – 16.9) and neutrophils at 16.52K/µL (normal 3.0 – 12.0). His electrolytes were normal with low normal potassium.

TREATMENT PLAN

            Charlie was treated aggressively with hospitalization for several days on IV fluids. He was maintained in isolation with strict isolation protocols due to the likelihood of contagious disease. He was initially started on 120ml/kg/day of Plasmalyte IV fluids that was supplemented with potassium using Scott’s Sliding Scale (16mEq/L). On day 1 he was given a topical flea treatment, but we postponed oral deworming medications due to his history of vomiting, and 1 episode of vomiting a few hours after admission. He was given ampicillin 22mg/kg IV slowly q8hrs, metronidazole 15mg/kg IV slowly q12hrs, famotidine 0.5mg/kg IV slowly q12hrs and maropitant citrate 1mg/kg SQ q24hrs. He was NPO for the first 24 hours in the hospital.

            On day 2, Charlie seemed better hydrated, although his gums were paler. His abdomen was more comfortable as well. We checked his PCV/TP, and his PCV did drop by 10% and TP by 1.0g/dL. We also checked his electrolytes, and his potassium level was improved. We continued with his prescribed plan from the previous day but also gave praziquantel/pyrantel pamoate/febantel (Drontal) orally as a dewormer and collected a sample of feces to screen for ova/parasites and giardia. His PCV/TP was repeated 12 hours later and was stable. We started offering small amounts of bland food as well, and while not interested at first, he did start to eat later in the day. Charlie had several episodes of diarrhea through the day, including one sample with adult roundworms in it. His fecal sample did come back positive for roundworm eggs, but negative for other ova and giardia cysts.

            Charlie had 2 episodes of vomiting overnight into day 3. We pursued radiographs at this point to rule out an obstruction or other cause of the vomiting. The x-rays showed a small amount of effusion that was consistent with his age, gas in his colon, and mild dilated small bowel loops likely from ileus. No obvious obstruction was seen. His ampicillin was discontinued in the event it was contributing to the vomiting, and he was transitioned onto PO famotidine. He was continued on metronidazole and maropitant citrate and also received a dose of pyrantel pamoate and prochlorperazine/isopropamide as a motility-modifying drug. His electrolytes remained normal, and his PCV was slightly improved. Through the day, though, Charlie continued to decline. He vomited a total of 5 times through the day, his energy level was down and his hydration was worse at his evening physical exam.

            Into day 4 Charlie had no episodes of vomiting or diarrhea. He was continued through the day on PO famotidine, IV metronidazole, prochlorperazine/isopropamide, and another dose of pyrantel. He had his IV catheter replaced since his first catheter had been placed 72 hours prior. He was syringe fed bland food as his appetite was poor. He had good progression from day 3 to 4, with only one episode of vomiting mid-day on day 4.

            On day 5 he had no episodes of vomiting or diarrhea. We repeated his CBC/differential, and his white blood cell counts had plummeted to 1.46K/µL (neutrophils, monocytes and eosinophils were all low). His anemia was stable. We resumed treatment with ampicillin and added gentamicin as an additional antibiotic. We continued IV metronidazole, prochlorperazine/isopropamide, and PO famotidine. He was syringe fed through the day, and his IV fluids were also supplemented with 2% dextrose (50%).

            On day 6, Charlie was eating and drinking well and had no episodes of vomiting and diarrhea. He did develop a fever of 104.8ºF that fluctuated up to 106.8, clear nasal discharge, an oral ulcer on his tongue, and a cough. His white blood cells had dropped to 1.14K/µL. His medication regimen was continued. Carafate was added for the oral ulcer and azithromycin as a macrolide antibiotic to treat for possible pneumonia/CIV/bordetella. To ensure that the catheter was not contributing to his fever, his IV catheter was removed and he received SQ fluids. 

            On day 7, Charlie had his IV catheter replaced and was re-started on fluids due to his persistent fever. His GI signs and appetite were improved. He was transitioned onto all PO medications; famotidine 0.5mg/kg PO q24hrs, carafate ¼ gram in slurry to tongue q6hrs, enrofloxacin 10mg/kg PO q24hrs, azithromycin 10mg/kg PO q24hrs and metronidazole 10mg/kg PO q 12hrs. His plan included nebulizing and coupaging lightly, and he did have productive coughs after coupage. His fever did break mid-day and came down to 100.7ºF.

            On day 8 Charlie’s white blood cell count was dramatically improved at 6.95K/µL. His temperature was normal, his appetite was good, and he had a normal bowel movement. His temperature fluctuated mildly through the day, but was normal before discharge. Charlie was discharged with his regimen of PO medications and bland diet.

FINAL DIAGNOSIS

            Canine parvovirus (CPV) and pneumonia versus CIV versus bordetella.

OUTCOME

            Charlie had very waxing/waning clinical signs throughout his hospital stay. He also developed an upper respiratory infection that may have been due to immunosuppression, aspiration pneumonia, or he may have contracted CIV or bordetella prior to admission. All of his clinical signs improved well with appropriate treatments, and his recheck appointment 5 days and 11 days after discharge showed him to be doing well. At the 11 day recheck, his white blood cell count was elevated, but at recheck 3 weeks later showed they were normal.

CONCLUSION

            CPV is a contagious virus causing enteritis in dogs. Signs usually begin 5-12 days after infection via oral-fecal route and hallmark signs involve destruction of intestinal crypts. The virus invades and destroys rapidly dividing cells, such as bone marrow progenitors and intestinal epithelium, causing villus collapse, vomiting, diarrhea, intestinal bleeding, and bacterial invasion.¹ CPV is generally seen in puppies under 6 months of age, and commonly between 6 and 20 weeks.² It has been reported that Doberman Pinschers, Rottweilers, Pit Bulls and Labrador Retrievers may be more susceptible than other breeds.¹

            Common clinical presentation includes lethargy, anorexia and vomiting. Diarrhea often develops later in the course of the disease, between 24 and 48 hours. The diagnostic approach should begin with a parvovirus ELISA. The ELISA can be affected by vaccination within 5-15 of testing, but a positive ELISA paired with appropriate clinical signs can still give the presumptive diagnosis. Neutropenia on bloodwork is often suggestive, but not diagnostic of parvovirus, and is seen in less than 50% of infected dogs.² Other bloodwork abnormalities that can be seen with both general enteritis cases and parvovirus include; hypoproteinemia secondary to fluid loss from vomiting/diarrhea and electrolyte derangements such as hypokalemia, hypernatremia, and hyperchloremia. In advanced cases, hypoglycemia can be seen secondary to inappetance and/or sepsis. Hypercoagulability has also been noted due to hyperfibrinogenemia. Radiographs are often pursued to rule out other causes of gastrointestinal upset, such as foreign body obstruction, surgical ileus, or intussusception.

            Like most other enteritis cases, treatment involves symptomatic supportive care with fluids, antibiotics, and antiemetics. Fluid therapy should begin with an isotonic crystalloid such as Plasmalyte, although colloid therapy may be required for patients with hypoproteinemia or septic shock. Whole blood may be necessary as well if the enteritis progresses to hemorrhagic and severe anemia is present. Potassium chloride is often required to counter hypokalemia, and glucose supplementation may be added as well due to inappetance or sepsis.

Antibiotic therapy is indicated in patients with evidence of pyrexia, neutropenia, or sepsis. Aminopenicillins and aminoglycoside penicillins such as ampicillin and gentamicin are often used. Proper hydration/perfusion are necessary when using aminoglycosides due to potential nephrotoxic side-effects.³ Metronidazole is a good antibacterial and antiprotozoal agent as well. Flourquinolones such as enrofloxacin can be used with ampicillin, although adverse effects can be seen on growing puppies.² Antiemetics are also an important therapy as vomiting contributes to dehydration and esophagitis. H₂ receptor antagonists such as famotidine and neurokinin receptor antagonists such as maropitant citrate are a good combination for treatment.³ Prognosis is generally good if treatment is initiated quickly, especially if patients survive the first 4 days of clinical signs.¹ CPV can, though, be fatal, particularly if treatment is not initiated quickly before the patient becomes hypovolemic from fluid loss.

            CPV patients should be isolated to avoid transmission to other patients in the hospital. After discharge, CPV-infected dogs should be kept away from other dogs initially, as they have been shown to shed the virus for up to 39 days post infection.² Bleach is one of the only known disinfectants to properly disinfect hard surfaces and bedding. Patients with CPV are also severely immunocompromised, and the isolation serves to protect them as well.

DISCUSSION

            Charlie’s case management was complex and prolonged, but his clinical signs all improved before discharge and he recovered well. His symptoms waxed and waned over the first several days which lead to other diagnostic testing to ensure his disease was not complicated by other processes. His immunocompromised state made him susceptible to upper respiratory infection, which could have been due to viral pneumonia, aspiration pneumonia, or CIV/bordetella. These signs began at day 5, which would be consistent with when the clinical signs of viral/bacterial tracheobronchitis usually commence. Some of Charlie’s treatments were controversial, such as maropitant citrate use before the age of 16 weeks as well as early use of enrofloxacin. In his case, the doctors felt the benefits outweighed the risks.

REFERENCES

1.     Nelson RW, Couto CG, eds. Infectious Diarrhea: Canine Parvoviral Enteritis. Small Animal Internal Medicine. 3^rd ed. St. Louis: Mosby Inc, 2003; 433-435.

2.     Hopper K, Silverstein DC, eds. Canine Parvovirus Infection. Small Animal Critical Care Medicine. 1^st ed. St. Lous: Saunders, 2009; 482-485.

3.     Plumb DC, ed. Plumb’s Veterinary Drug Handbook. 6^th ed. Ames, IA: Wiley-Blackwell; 2008: 122, 77, 457, 562, 751, and 819.