Canine Parvovirus | Can a dog recover from Parvo enteritis?

Canine parvovirus is a highly contagious viral infection of young or older unvaccinated dogs. Any dog with GIT signs must be tested for parvovirus. However, no specific treatment is available for parvovirus infection in dogs, but with supportive therapy, the survival rate of dogs is 68 to 92 percent, and most puppies that survive the first three-to-four days can make a complete recovery. This article is going to cover in-depth canine parvovirus infection in dogs.

Cause of Canine Parvovirus in Dogs

The cause of canine parvovirus infection in dogs is CPV (Canine parvovirus). This virus belongs to the family Parvoviridae. It is thought to have originated from the feline panleukopenia virus, while its exact origin is unclear.

Some Characteristics of CPV

• It is a linear single-stranded DNA virus
• Parvovirus virions are 23–28 nanometers (nm) in diameter
• It is non enveloped and the capsid is icosahedral
• Resistant to disinfectants as well as to pH & temperature fluctuations

(“Parvoviridae”, 2022)

Host Susceptibility

This virus is not limited to dogs infact some wildlife species like foxes, raccoons, and wolves are also susceptible. As it is not a zoonotic disease so humans are not susceptible, but in regions where parvovirus infections in dogs are more, humans are at elevated risk of acquiring other zoonotic diseases.

Young (6 weeks to 6 months old), unvaccinated, or incompletely vaccinated dogs are most susceptible. Some breeds of dogs are more susceptible to parvo infection than others (AKC Canine Health Foundation). Those breeds are listed below

• Rottweilers
• Doberman Pinschers
• Labrador Retrievers
• German Shepherds
• Bull Terrier breeds
• Alaskan sled dogs

Note: The dogs that are more than 6 months of age, more cases were reported in male dogs than in female dogs.

Transmission & Pathogenesis of Canine Parvovirus

Infected dogs shed the virus in their feces even before the onset of clinical signs. The dogs continue to shed the virus in their fecal material, even for more than 10 days after the clinical recovery. Healthy dogs acquire infection either through direct contact with the virus particles (oral-fecal route) or through indirect contact (fomites).

After getting an entry, the virus first replicates in the lymphoid tissues of the oropharynx. The virus then causes the destruction of rapidly dividing cells of small intestinal crypts epithelium, lymphopoietec tissues, and bone marrow.

This destruction of small intestinal crypts is responsible for villous atrophy, the necrosis of intestinal epithelium, loss of absorptive function of the intestine, and disruption in gut barrier function. The loss of barrier function leads to more chances for secondary bacterial infections.

According to (Meunier et al., 2016) when hematopoietic progenitor cells in the bone marrow and lymphopoietic organs are destroyed, lymphopenia and neutropenia result.

Clinical Signs & Symptoms of Canine Parvovirus in Dogs

The incubation period of parvoviral enteritis is 5-7 days but can range from 2-14 days. The clinical findings of parvo infection in dogs are

• Fever, lethargy, anorexia, and depression
• Vomiting
• Diarrhea with blood (Hematochezia)
• Dehydration
• Increase CRT
• Tachycardia and poor pulse rate
• Intussusception may occur in severe cases

Note: In some cases, blood in diarrhea can be absent.

According to (Schaudien et al., 2010) parvovirus replication was reported in the brains of five 6-week-old Cretan hound puppies suffering from puppy shaker syndrome and leukoencephalopathy.

Postmortem Findings of Parvo infection in Dogs

• A thickened and discolored intestinal wall
• Watery, mucoid, or hemorrhagic intestinal contents
• Edema and congestion of abdominal and thoracic lymph nodes
• Thymic atrophy
• If a dam is infected with CPV, then puppies born to such dam have a greater risk of myocarditis so pale color streaks in the myocardium observe during post-mortem examination

Diagnosis of Canine Parvovirus in Dogs

Diagnosis of canine parvovirus in dogs is done on the basis of

• History
• Clinical signs and Clinicopathological findings
• Laboratory confirmatory tests like Fecal parvoviral antigen test or viral PCR

Note: Any unvaccinated dog with a history of vomiting and bloody diarrhea should be tested for Parvo enteritis.

Clinicopathological findings of Parvoenteritis

The predominant hematological anomaly in canine PVE is leukopenia caused by neutropenia and/or lymphopenia because of the death of bone marrow precursors, the depletion of lymphoid organs, and the increased demands of the severely inflamed digestive tract.

Despite the fact that hypoproteinemia, hypoalbuminemia, and hypoglycemia (or mild-to-moderate hyperglycemia), reflect the interaction of severe malnutrition, septicemia, and/or the stress-induced activation of catecholamines. Hypocalcemia, and electrolyte abnormalities like hypokalemia, hyponatremia, hypochloremia, and hypomagnesemia, are nonspecific serum biochemistry abnormalities that frequently occur. Prerenal azotemia can also happen, although less commonly. Hyperbilirubinemia or elevated liver enzyme activity can indicate SIRS- or hypoperfusion-induced liver injury.

Detection of viral antigen or DNA in feces

The tests like ELISA, immunomigration assays, and immunochromatography assays applied to fecal or rectal swab samples are the most economical assays for virus identification. False-negative results can be caused by intermittent or diminished viral shedding in the early or late stages of infection, the interaction of serum-neutralizing antibodies with antigens in the intestinal lumen, or the dilutional effect of diarrhea.

Differential Diagnosis

The canine parvovirus in dogs must be differentiated from other similar diseases like canine distemper, and infectious necrotic hepatitis.

Note: In canine distemper along with GIT signs, respiratory signs, and neurological signs are present. Also, hematochezia is absent in canine distemper whereas, in parvo infection, bloody diarrhea is present in a majority of cases.

Treatment of Canine Parvovirus in Dogs

Treatment for PVE is largely supportive and symptomatic. The principal components of treatment include

1-Fluid therapy

2- Antibiotic treatment

3- Antiemetic treatment

4- Nutritional support

Fluid therapy

For the correction of acid-base and electrolyte disturbances, fluid therapy must be done. Typically, a balanced isotonic crystalloid solution (such as Lactated Ringers) is the preferred fluid for early rehydration and restoration of intravascular volume.

• Ringer Lactate 15ml/kg IV

Antibiotic therapy

Due to the significant danger of septicemia brought on by the collapse of the mucosal barrier and the accompanying profound neutropenia, parenteral administration of broad-spectrum bactericidal antibiotics is necessary for dogs with severe PVE. Ampicillin and cefoxitin as single-agent treatments or in combination with enrofloxacin (Mylonakis et al., 2016)

Note: Don’t use aminoglycosides in dehydrated dogs because of nephrotoxic effects. However, it’s safe to use in well-hydrated animals.

• Ampicillin 20–40 mg/kg/8 hours IV
• Cefoxitin 20–30 mg/kg/8 hours IV
• Enrofloxacin 5–10 mg/kg/24 hours IV

Antemetic therapy

Although antiemetic medication is unquestionably necessary for PVE, many affected dogs continue to vomit for a long time even after taking antiemetics. Various antemetic drugs are available like chlorpromazine, Acepromazine, Prochlorperazine, Aminopentamide, Dimenhydrinate, Diphenhydramine, and Maropitant, etc.

• Acepromazine (0.025–0.2 mg/kg, IV, IM, SC, maximum 3 mg; 1–3 mg/kg, PO)
• Chlorpromazine (0.5 mg/kg, IV, IM, SC, tid-qid)
• Aminopentamide (0.022 mg/kg, PO, SC, or IM, bid-tid)
• Dimenhydrinate (4–8 mg/kg, PO, tid)
• Diphenhydramine (2–4 mg/kg, PO, tid)
• Maropitant (2 mg/kg, PO or 1 mg/kg/day, SC, for up to 5 days)

Nutritional therapy

Improved mucosal integrity, quicker healing, and a consequent decrease in the likelihood of bacterial translocation are all linked to enteral feeding.

Antiviral therapy

Oseltamivir, a neuraminidase inhibitor, has attracted attention for the treatment of PVE. In a previous study, the use of oseltamivir (2 mg/kg, per os, for 5 days) improved body weight and hematological parameters in dogs with PVE.

Note: For pain, or fever, choose any analgesic or antipyretic like ketoprofen, flunixin meglumine, etc

(Mylonakis et al., 2016)

Prevention of Canine Parvovirus in Dogs

Canine parvovirus infection can be prevented by effective immunization of puppies at 6–8 weeks of age, and then every 2–4 weeks until 16 weeks of age or older with a modified live virus vaccine. Modified live vaccines (MLVs) are currently used worldwide affording prolonged 7 years or longer immunity

Conclusion

• Canine parvovirus is a highly contagious cause of acute GI disease in young, unvaccinated dogs.
• Diagnosis is based on signalment, history, presenting signs, and fecal viral antigen testing or viral PCR testing.
• Treatment requires supportive care with fluids, antiemetics, antibiotics, and nutritional support.

References

Meunier, P. C., Cooper, B. J., Appel, J. G., Lanieu, M. E., & Slauson, D. O. (2016). Pathogenesis of Canine Parvovirus Enteritis: Sequential Virus Distribution and Passive Immunization Studies. Veterinary Pathology. https://doi.org/10.1177/030098588502200617

Mylonakis, M. E., Kalli, I., & Rallis, T. S. (2016). Canine parvoviral enteritis: an update on the clinical diagnosis, treatment, and prevention. Veterinary Medicine : Research and Reports, 7, 91-100. https://doi.org/10.2147/VMRR.S80971

Parvoviridae. (2022, September 25). In Wikipedia. https://en.wikipedia.org/wiki/Parvoviridae