Parvoviruses (canine parvovirus -2) September 7-8, 2010.

Parvoviruses(canine parvovirus -2)

September 7-8, 2010

First reports of CPV enteritisAn enteric disease of dogs resembling feline panleucopenia.W.R. Kelly, Aust. Vet Jn. 54:593. 1978

Canine gastroenteritis associated with a parvovirus-like agent. G.W. Thompson and A.N. Gagnon. Can. Vet Jn.19:346. 1978

W.R. Kelly. 1978. An enteric disease of dogs resembling feline panleucopenia. A.V.J. 54:593

Kelly, 1978

intestinal crypts normal

suspected viral enteritis

bone marrow

First reports of CPV myocarditisDiffuse subacute myocarditis of possible viral aetiology:A cause of sudden death in pups. W.R. Kelly.Aust. Vet Jn 55:36. 1979

Sudden death in puppies associated with a suspected viral myocarditisR.B. Atwell et al. Aust. Vet Jn 55:37. 1979

Kelly,1979

The evolution of CPVFeline parvovirus

Fox parvovirus

Raccoon parvovirus

Carnivore (?) parvovirus

1970,74-76

CPV-2 CPV-2a CPV-2b

1979 1987

cats

?

?

?

?(10-20% of cats with parvoenteritis)

~1900

?

CPV-2c

2004

The virus

dimple

canyon

neutralizing epitopes,host-range mutations

Kennedy et al. 1995. Virucidal efficacy of the newer quarternary ammonium compounds. JAAHA 31:254

Kennedy et al ‘95

American Jn of Inf. Control2006, 34:269-273

1000 ppm is equivalent to approx. 2% solution of household bleach

Parvovirus in the scheme of things

Circoviridae

Parvoviridae

porcine circovirus

canine parvovirus-2feline panleukopenia virus

porcine parvovirus (SMEDI)

Viruses with single stranded DNA

Replicative cycle

• Attachment

• Requirement for dividing cells

• Intranuclear inclusion bodies

• Release by lysis - death of cell

CPV attaches to cells using transferrin receptor (host

tropism)The natural host-range shift and subsequent evolution of canine parvovirus resulted from virus-specific binding to the canine transferrin receptor. Hueffer et al. 2003 J. Virol 77; 1718-1726

transferrin receptor

Pathogenesis

• infection– fecal-oral route

• Virus extremely stable (> 6 months)– Inactivated by 4% solution of bleach

– Most “virucidal” disinfectants not effective

– access to lymphatic nodules in tonsils or gut (M-cells)

Entry at mucosal surfaces (M cells)

M cell

Entry at mucosal surfaces (M cells)

M cellTransport across M cell

Entry at mucosal surfaces (M cells)

InfectedLymphoid cell

spread

Spread of virus in the body

mesenteric, systemiclymph nodes, bone marrow(lymphoid and myeloid precursors)

crypt cellsno epithelial replacement,collapse of lamina propria

virus in feces

Actively dividing cells in gut

Peyer’spatches

crypt cells

Damage to the gut

collapsed crypts

depleted Peyer’s patches

Incubation period and duration of shedding

infection

virus shedding

clinical signs

day 0

4-14 days

incubation period

After challenge

incubation period

vaccination does not provide “sterile immunity”

Ron D. Schultz

What happens to the sick dog

• depression• diarrhoea and vomiting• fever• leukopenia, neutropenia• secondary bacterial infections• dehydration, shock• long term sequelae

Response to infection - asymptomatic ->death

Depends on:

• immune status of dog– Immune or able to make antibodies

• individual variation– Intestinal and lymphoid cell turn-over

• genetic susceptibility

• variation among virus strains

Risk factors for parvovirus enteritis

• season - 3 times more likely - July to Sept

• breeds - Rottweilers, Dobermans, Shepherds

• sex - intact dogs four times more likely

• no vaccination - 13 times more likely

Risk factors associated with parvovirus enteritis in dogs:283 cases - D. M. Houston et al. JAVMA 208:542-546. 1996

Most likely clinico-path findings

• lethargy and vomiting - 84-87%• diarrhoea - 60%• leukopenia (at some time) - 45%• neutropenia (at some time) - 51%• fever (>39.5) - 24%

Risk factors associated with parvovirus enteritis in dogs:283 cases - D. M. Houston et al. JAVMA 208:542-546. 1996

 Vet Rec. 2010 Aug 7;167(6):196-201.Epidemiology of canine parvovirus and coronavirus in dogs presented with severe diarrhoea to PDSA PetAid hospitals.Godsall SA, Clegg SR, Stavisky JH, Radford AD, Pinchbeck G.

Correlates with detectable CPV2 in feces of dogs with diarrhoea:•Lack of vaccination in young dogs (<30 months)•Vomiting, depression and diarrhoea

No correlation with:•Vaccination status in older dogs•Breed•Severity of diarrhoea, heamorrhage•Mortality

Myocarditis

Diagnosis of parvovirus enteritis

• Clinical signs and clinico-pathological parameters– why are these not sufficient to make a

definitive diagnosis

Some infectious causes of enteritis in dogs

• Parvovirus

• Distemper virus

• Coronavirus

• Rotavirus (<2weeks)

• Salmonella

• Campylobacter

• Clostridium

• Yersinia

• Neorickettsia

• Histoplasmosis

Virus isolation

• fecal suspension treated with chloroform

• inoculate feline kidney cells

• incubate 3-5 days•stain with parvo-virus antibody+fluoroscene

Haemagglutination (HA)

virus No virus

HaemagglutinationDilution

2 4 8 16 32 64 128 256 512

prozone titre

1024Novirus

Comparison of sensitivity

dilution 0 1/10 1/100 1/1000 ..…….. 10-7

IDEXX

Virus isolation

HA 1/8192 (HA titre during peak clinical signs is 1,000 -10,000)

Incubation period and duration of shedding

infection

virus shedding

day 0

4-14 days

incubation period clinical signs

Haemagglutination inhibition (HAI)

• heat to inactivate complement in serum

• adsorb to RBC, then remove

• dilute (1/20, 1/40 etc)

• add virus

• incubate

• add RBC

• incubate

HAI Serumdilution

1/20

1/40

1/80

1/160

1/320

1/6401/1280

-ve control

1 wk8 wksVirusHA

Protection of animals (vaccination)

• by itself or as component of combined vaccine (DA2PPv)

• attenuated or inactivated

Interference by maternal antibodies

2 4 6 8 10 12

**

**

*

*

pass

ive

anti

body

weeks after birth

minimum level needed for protection

interferes withvaccination

window ofsusceptibility

HAI - 80

HAI - 10 to 20Puppies canOnly beVaccinatedBelow this level

J Vet Med B Infect Dis Vet Public Health. 2000 May;47(4):273-6.Immunization of pups with maternally derived antibodies to canine parvovirus (CPV) using a modified-live variant (CPV-2b).Pratelli A, Cavalli A, Normanno G, De Palma MG, Pastorelli G, Martella V, Buonavoglia C.

Passive antibody decreases vaccine efficacy

Strategies for reducing/overcoming risk of maternal interference

• biweekly vaccinations

• low passage, high titre vaccines

Low-passage, high-titre vaccines

• Pfizer - Vanguard puppy

• Schering-Plough - Galaxy

• Merial - Canine Parvo XL

Vaccines should contain CPV2a and CPV2b

CPV vaccination: comparison of neutralizing antibody responses in pups after inoculation with CPV2 or CPV2b modified live vaccines. Pratelli et al. 2001. Clin. Diag. Lab. Immunol. 8: 612-615

Debate on frequency of vaccination

How long does antibody last?

Vet Ther. 2004 Fall;5(3):173-86. Evaluation of the efficacy and duration of immunity of a canine combination vaccine against virulent parvovirus, infectious canine hepatitis virus, and distemper virus experimental challenges.Abdelmagid OY, Larson L, Payne L, Tubbs A, Wasmoen T, Schultz R.

Parvovirus vaccines licensed in Canada

• modified-live alone or in various combinations

CFIA

Potential antiviral therapy

Vet Rec. 2003 Jan 25;152(4):105-8. Treatment of canine parvoviral enteritis with interferon-omega in a placebo-controlled field trial.de Mari K, Maynard L, Eun HM, Lebreux B.

J Vet Pharmacol Ther. 2010 Aug;33(4):352-6.Hematologic improvement in dogs with parvovirus infection treated with recombinant canine granulocyte-colony stimulating factor.Duffy, A, Dow S, Ogilvie G, Rao S, Hackett T.

Other parvoviruses of veterinary importance

• feline panleukopenia virus (related carnivore parvoviruses)

• porcine parvovirus

• aleutian mink diseases

• human parvovirus B19

Feline parvovirus

normal

cerebellar

hypoplasia

from:Veterinary VirologyMurphy et al.

CzarMr. S brought Czar, a 7 month old Rottweiler, to the WCVM clinic on August 30. Czar had had severe vomiting and diarrhea for the previous two days. He had vomited two or three times on the previous evening and once that morning. The diarrhea was watery with no blood. Czar had not eaten in the two days prior to presentation.

Czar did not have a history of raiding garbage cans and Mr. S thought it unlikely that Czar had eaten anything unusual. The dog was fed a commercial puppy chow and there had been no change in his diet.

Czar’s vaccinations were up to date with extra parvovirus boosters up to 20 weeks of age. According to the WCVM records Czar had been vaccinated at 8, 12, 16 and 20 weeks with a vaccine containing distemper virus, parvovirus and adenovirus-2.

The attending veterinarian found Czar to be listless and quiet. The dog was anorexic and slightly dehydrated. There appeared to be no discomfort on palpation.

His temperature was 39oC (N 37.2 – 39.2), pulse was 116 (N 70 – 160) and respiration was 32 (N 10 -30).

1. You suspect that Czar has parvovirus enteritis. What tests would you request to confirm (or refute) your suspicions?

2. What are your reasons for requesting these tests? What would you expect the tests to show?

3. Would you treat Czar with antibiotics? Why?4. If you requested a complete blood count (CBC) for Czar, what might the

CBC pattern be? How might you expect the pattern to change over the next few days?

5. Which tissues is the parvovirus most likely to affect? What changes would you expect in these tissues?

6. Assume that Czar has parvovirus enteritis. Why do you think he became sick despite your having vaccinated him against parvovirus?

7. Are any of Mr. S’s family members likely to be infected by Czar’s virus? Is there a human parvovirus? How is it related to canine parvovirus 2?

8. Can Czar pass parvovirus on to the family cat?9. What advise would you give Czar’s owner about disinfecting areas

contaminated with Czar’s feces?10. Czar was hospitalized but a week later he had recovered and was sent home.

Would you expect Czar to be “contagious” at that time?

Questions 1 and 2: Liz Andree – Colleen ChanQuestions 3 and 4: Sydney Chow – Shannon GruenQuestions 5 and 6: Amber Hamilton – Angela LeQuestions 7 and 8: Ellen Littley – Janine RegehrQuestions 9 and 10: Dane Richardson – Anita Yee

Blood was taken for CBC, a faecal sample was submitted for bacteriological analysis and a ParvoCITE test was performed. On the basis of the ParvoCITE test, which was strongly positive, a diagnosis of parvovirus enteritis was made.

Czar was put in an isolation ward and started immediately on IV fluids. Ampicillin as well as gentamicin were administered. Over the next 3 days Czar's condition deteriorated. Diarrhea became bloody. The IV fluids and antibiotics were continued. On the fourth day after admitting, the diarrhea appeared to stop. Although weak, Czar seemed willing to walk around. The dog's condition improved steadily over the next few days. By day 6 Czar was able to drink without vomiting and a day later he ate small amount of Hill's I/D diet.

Once it was established that he could maintain his body's fluid levels he was weaned off the I.V. fluids. Eight days after being admitted to hospital he was sent home.

What happened