The Armed Forces Institute of Pathology Department of Veterinary Pathology WEDNESDAY SLIDE CONFERENCE 2007-2008 Conference 4 3 October 2007 Moderator: Shelley Honnold, DVM, Diplomate ACVP CASE I – 07L-1736 (AFIP 3066074). interstitial, predominantly lymphocytic and histiocytic infiltration with occasional scattered plasma cells and Signalment: 6-week-old, female, Bulldog, canine neutrophils, together with mild to moderate interstitial fibrosis. The myocardial fibers exhibit moderate diffuse History: This animal is from a litter of 5 puppies which anisocytosis and multifocal loss of striation, with cyto- had recurrent diarrhea and chest problems from birth. plasmic eosinophilia and occasional fragmentation. Mul- Three siblings had died in a period of 9 days. Death was tifocally, single, large (up to approximately 20x40 µm), described as sudden, occasionally preceded by rigidity homogeneous and occasionally stippled, basophilic, and vocalisation. The mother was fully vaccinated. ______________________________________________ 1-1 Heart, dog. Cardiomyocyte nuclei contain basophilic Gross Pa thology: The heart was diffusely pale and inclusion bodies which obscure and peripheralize chro- moderately enlarged and a mild pericardial effusion was matin (arrows). (H&E 400X) observed. The lungs were markedly and diffusely oede- matous and the liver was severely congested. Laboratory Results: Immunohistochemistry for canine parvovirus was performed on sections of myocardium, lung, stomach, small intestine, colon, liver, pancreas, gall bladder, spleen, thymus, and bone marrow. Positive im- munolabelling was observed in the intranuclear inclusion bodies of the cardiac myocytes. Histopathologic D escription: Conference slides vary and include sections of left ventricle, septum and right ventricle but similar histological changes are consistently seen throughout. There is moderate to severe, multifocal to coalescing, WSC 2007-2008 Conference 4 mostly elongated, intranuclear inclusion bodies (fig. 1- 1) are observed in myofibers. In the cells containing in- CPV type 2 was found to be unable to infect cats al- clusion bodies, the nuclear chromatin is clumped at the though it was able to replicate in vitro in feline cells.13 nuclear membrane. As opposed to this, FPV was found able to replicate in vivo in the canine thymus but unable to replicate in vitro Contributor’s Morphologic Diagnosis: Heart, myocar- in canine cultured cells. dium: Myocarditis, diffuse, moderate, lymphohistiocytic, necrotizing, subacute to chronic, with intranuclear inclu- The CPV type 2 strain was soon replaced, worldwide, by sion bodies, Bulldog, canine. two new lineages: CPV2a, identified in 1980, that later gave rise to CPV2b, identified in 1984, both with the Contributor’s Comment: added ability to replicate in cats and produce clinical Canine Parvovirus (CPV) is a non-enveloped single- signs in experimentally infected cats.12,18 In Italy, Viet- stranded DNA virus grouped informally in the Feline nam and Spain, a third type, CPV2c has been identified.10 Parvovirus subgroup of the genus Parvovirus This antigenic drift is accompanied by successive re- (Parvoviridae family).6,16 placement of prevalent strains by newer serotypes.13 This is exemplified by the gradual disappearance of CPV2b Parvoviridae are amongst the smallest DNA viruses, the from the dog population in Italy6,10 and the replacement virion being 18 to 26 nm in diameter, and are composed of CPV2a by CPV2b in the UK.5 entirely of protein and DNA.11 The lack of fatty compo- nents, typically present in viral envelopes, makes these The mutations occur at the level of the VP1/VP2 gene viruses stable under diverse environment conditions and (encoding capsid proteins) and the new serotypes have an difficult to eliminate through disinfection. They can improved binding ability to its receptor, the canine trans- however, be inactivated by bleach, formalin and ferrin receptor.17 sunlight.7 CPVs require host cells to be in the S-phase to replicate The host range is one of the widest, the subfamily Parvo- as they are unable to induce it. They replicate within the virinae infecting vertebrates, including humans and the nuclei of infected cells and are highly dependent on the subfamily Densovirinae infecting insects. cellular function.11 CPVs infect domestic dogs and several species of wild Pathology and clinical signs are dependent on the time of canids, including coyotes, bush dogs, gray wolves, ra- infection and which cells are in a highly mitotic rate at coon dogs and manned wolves. Presently two autono- that particular moment within the host. Infection occurs mous parvoviruses are known to infect dogs: CPV type 1 oronasally and disease develops after 3 to 10 days of in- and CPV type 2. cubation.6 After faeco-oral infection, the virus is taken up by the epithelium over the tonsils and Peyer’s patches. CPV type 1 was initially named Minute Virus of Canines In 1 to 2 days after experimental inoculation, the virus and was first identified in 1970.1 It was proven to cause can be found in the mesenteric lymph nodes. Further enteritis and diarrhoea in neonatal canines. It appears to dissemination of virus particles into other central or pe- be highly related to the Bovine Parvovirus14 and is anti- ripheral lymphoid tissues occurs via infected lym- genically unrelated to CPV type 2. To date, only few phoblasts. Following the lysis of infected cell, viruses cases have been reported. are released and contribute to elevate the viremia which is only terminated if neutralising antibodies appear, typi- On the other hand, CPV type 2 appeared as a pandemic cally 5 to 7 days post infection. Moderate pyrexia usu- disease and presented characteristics of an epidemic in- ally occurs.2 fection affecting dogs of all ages. Although there is no specific data to support this, we can assume from the low If the infection takes place up to two weeks postnatally mortality rate, that death was mostly restricted to canines and the puppies do not have sufficient neutralising anti- less than 4 months old.3 It was first detected in 1978 but bodies, nonsuppurative myocarditis is the most common is estimated to have emerged up to 10 years before.10 condition. On the other hand, if infection occurs later than these two weeks, due to the fast replication of the CPV type 2 is thought to result from mutations of feline epithelia of the small intestines and bone marrow granu- panleukopenia parvovirus (FPV), with which it shares lopoiesis, hemorrhagic gastroenteritis with lymphoid more than 98% of the DNA sequence4 or from a closely depletion is the pathological picture. The two forms of related carnivore parvovirus.12 the disease rarely occur at the same time in an individual 2 WSC 2007-2008 Conference 4 or group of animals. When nonsuppurative myocarditis tonella elizabethae occurs, it is usually detectable between the third and Fungal/Algae like: Prototheca sp. eighth week of life, but can be asymptomatic until ani- Spirocheatal: Borrelia burgdorferi mals are six months old. Puppies frequently succumb to sudden death but can also present symptoms of conges- Other parvoviruses in animals include porcine parvovirus tive heart failure due to myocardial scarring or conduc- (SMEDI); feline parvovirus (feline panleukopenia); rat tion failure. Grossly, the main findings are cardiomegaly parvovirus (Kilham rat virus); minute virus of mice; and lesions in the myocardium, more pronounced in the goose parvovirus; and two genetically and antigenically left atrium and left ventricle. Pericardial and pleural ef- distinct parvoviruses in mink (mink enteritis virus, which fusions, ascites and hepatomegaly can also be observed. causes similar lesions as feline parvovirus, and Aleutian In the myocardium lesions are pale and streaky and often mink disease virus, which causes immune complex accompanied by multifocal petechial.8 Microscopically, glomerulonephritis and arteritis).16 single, homogeneous, basophilic or amphophilic, roun- dish to elongated, intranuclear, Feulgen-positive inclu- sion bodies are observed.2, 8 The chromatin is clustered Contributor: Department of Veterinary Pathology, at the nuclear membrane. Inclusion bodies are more fre- Faculty of Veterinary Science, University of Liverpool, quent in late incubation, before extensive exfoliation (in Crown Street, Liverpool L69 7ZJ, United Kingdom the intestinal form) or infected cell lysis. In animals 4 to http://pcwww.liv.ac.uk/vets 7 weeks old, separation of the thin myocytes by extracel- lular oedema, histiocytes, fibroblasts and fibrous tissue is References: seen. Myocytes appear granulated and with fragmented 1. Binn LN, Lazar EC, Eddy GA, Kajima M: Recovery cytoplasm. In animals 6 to 9 weeks old, inflammation is and characterization of a minute virus of canines. Infect more severe and mainly lymphoplasmacytic. In juvenile Immun 1:503-508, 1970 animals, 14 to 24 months old, inflammation is milder, 2. Brown CC, Baker DC, Barker IK: Alimentary system. histiocytes and fibroblasts are more frequent, and fibrosis In: Jubb, Kennedy, and Palmer’s Pathology of Domestic more extensive. Animals, ed. Maxie MG, 4th ed., vol. 2, pp. 177-178. Elsevier Limited, St. Louis, MO, 2007 AFIP Diagn osis: Heart: Myocarditis, lymphohistio- 3. Carmichael L: An annotated historical account of ca- cytic, chronic, multifocal, moderate, with necrosis and nine parvovirus. J Vet Med B Infect Dis Vet Public loss and basophilic intranuclear inclusion bodies, Bulldog Health 52:303-311, 2005 (Canis familiaris), canine. Conference Comment