Canine Parvovirus

This disease is caused by the canine parvovirus CPV2a or CPV2b, which invades and destroys actively dividing cells. The virus is transmitted via the oro-faecal route. It initially replicated in the lymphatic tissue of the oropharynx, mesenteric lymphoid nodules, and thymus, and then spreads to the lymph nodes of the small intestine and to the crypts of the intestinal epithelium.

Symptoms

Symptoms vary depending on the age of the animal and the type of cells that are actively dividing at the time of infection. In adult animals and puppies older than 2 to 4 weeks, the virus invades the intestinal crypt cells, leading to destruction of the villi. This causes bloody diarrhoea that may be accompanied by vomiting, dehydration, fever, anorexia, depression and abdominal pain. Animals with unstable intestinal flora are more severely affected due to the high rate of mitosis in intestinal cells. The virus may also invade bone marrow cells and lymph tissue, leading to lymphocytolysis and septic shock. In animals younger than 2 to 4 weeks, the virus invades myocardial cells, which can lead to fatal cardiomyopathy.

An accurate differential diagnosis must be performed to rule out other occasionally under-diagnosed pathologies that may also cause bloody diarrhoea, such as internal parasitosis (coccidia, giardia), other viral diseases (distemper, rotavirus, coronavirus), bacterial infection (campilobacter, salmonella), idiopathic haemorrhagic gastroenteritis, tumours, invaginations, foreign bodies, etc.

Considering canine coronavirus in the differential diagnosis is particularly important, since it invades and destroys mature intestinal villi cells. It is less pathogenic than parvovirus, but when both are present the gastrointestinal symptoms become more acute and the prognosis is reserved.

Interpretation of laboratory tests

General Tests

• Coprological examination:
  To detect internal parasites that cause or exacerbate gastroenteritis.
• Complete blood count:
  Haematocrit may be elevated due to dehydration, but anaemia and panleukopaenia lasting 3 to 6 days (but sometimes only 24 - 48 hours) post-infection are usually detected. Panleukopaenia can sometimes progress to reactive lymphocytosis.
• Biochemistry and serum protein:
  These tests can provide insight into the animal’s overall status. It is important to monitor total protein decline in puppies.

Specific tests

• Parvovirus in faeces:
  Faecal shedding begins around 2 days post-infection, peaks around the sixth day, and decreases between days 10 and 14 before reaching undetectable values. The samples that provide the most reliable results are those collected between the first and third day from the onset of symptoms. In some cases, viral shedding occurs intermittently over a longer period of time. In some cases, the formation of immune complexes in the intestine reduces viral shedding to undetectable levels, leading to false negatives.
  After vaccination, viral shedding occurs for between 3 and 7 days (up to 14 days according to some authors).
• Serum antibodies:
  High levels are indicative of disease in unvaccinated animals and of good protection in vaccinated animals. If low levels are detected in vaccination controls, the animal should be revaccinated. Abs appear approximately 3 days after vaccination or infection. Peak levels are obtained between the third and fourth week.

Health measures

The canine parvovirus can be inactivated using over-the-counter bleach (1:30) for approximately one hour or formalin. Other products are not effective. The virus can remain in the environment (cages, clothing, etc.) for more than five months.

Prophylaxis

Vaccination. In puppies, maternal Ab levels should be taken into account. Some live attenuated vaccines may cause transient lymphopaenia in the initial phase of active immune response; they do not cause immunosuppression. Animals that have recently been exposed to the virus cannot be immunised due to the coexistence of viral incubation and seroconversion.

Bibliography

• APPEL, M.J. (1987) Virus Infections of Vertebrates (Elsevier) pg.422-426.
• APPEL. M.J.G. (1998) Veterinary Medicine (April) pg.360-366.
• CASTRO, A.E. (1992) Veterinary Diagnostic Virology Mosby Year Book, pg. 150-154.
• COYNE, M.J. (2000) Journal of American Animal Hospital Association, vol 36, nº2, pg. 137-142.
• HALL, E.J. ( 1999) Veterinary Clinics of North America: Small Animal Practice, Vol 29, nº3, pg. 441-469.
• HIRASAWA. T. (1994) Veterinary Microbiology 41 pg. 135-145.
• HOSKINS, J.D. (1997) Veterinary Medicine, Vol. 92, nº8, pg. 694-709.
• HOSKINS, J.D. (1998) Informe Técnico nº1 INTERVET.
• HOSKINS, J.D. (1999) Canine Practice, Vol. 24, nº6, pg.16-22.
• HOSKINS, J.D. (2000) Canine Practice, Vol. 25, nº1, pg. 6-10.
• KOUTINAS, A.F. (1998) Veterinary Microbiology, vol. 63, pg. 109-116.
• LATOUR, S. (2000) VETOMECUM . nº 245, pg. 1-2.
• LEIB, M.S. (1997) Practical Small Animal Internal Medicine, W.B. Saunders. pg. 691-692, 695, 726-728.
• MARTIN, M. (1993) Medicina Veterinaria,Vol 10,nº 12, pg 670-674.
• MARTIN, M.(1993) Ciencias Veterinarias. Animales de Compañía, nº9, pg. 221-240.
• MINAGAWA, T. (1999) Veterinary Microbiology, Vol. 69, pg. 51-53.
• MOCHIZUKI, M. (1993) Research in Vererinary Science, 55, pg. 60-63.
• NELSON, R.W. (1995) Pilares de medicina Interna en Animales Pequeños (Mosby Year Book) pg. 257,260-261,312,319-339).
• PARRISH, C.R. (1999) Veterinary Microbiology, Vol. 69, pg. 29-40.
• PEREIRA, C.A.D. (2000) Veterinary Microbiology, Vol. 75, pg. 127-133.
• POLLOCK, R.V.M. (1993) Veterinary Clinics of North America, Vol 23, nº 3, pg. 555-568.
• PRATELLI, A. (2000) Journal of Veterinary Medicine B, Vol. 47, pg. 273-276.
• PRATELLI, A. (1999) Journal of Veterinary Diagnostic Investigation, Vol 11, nº4, pg. 365-367.
• PRATELLI, A. (1999) Journal of Veterinary Diagnostic Investigation, Vol 11, nº4, pg. 550-553.
• RIMMELZWAAN, G.F. (1990) Overgenomen unt The Veterinary Quarterly 1214. 21 pg 240-246.
• SIMARRO, I. (1996) Consulta de Difusión Veterinaria, nº1, pg. 5.
• SIMARRO, I. (1988) Medicina Veterinaria Vol. 5. nº4 pg.229-232.
• SODIKOFF, C.H. (1996) Pruebas diagnósticas y de laboratorio en las enfermedades de pequeños animales (Mosby) pg. 172-174, 374-375.
• TRUYEN, V. (1999) Veterinary Microbiology, Vol. 69, pg. 47-50.
• UWATOKO, K. (1995) Veterinary Microbiology, Vol 43, pg. 315-323.
• WHAN-GOOK, N. (1997) Journal of Veterinary Diagnostic Investigation, Vol. 9, pg. 255-260.