Histopathologic evidence for parvovirus infection in dogs

Two dogs kenneled at a commercial establishment died of a disease manifested as severe hemorrhagic diarrhea. Histopathologic findings in both dogs bore a striking resemblance to those typical of feline infectious enteritis. Viral particles resembling members of the Parvoviridae family were observed in the contents of the small intestine of one of the dogs. The disease was similar to the recently recognized canine gastroenteritis associated with a parvovirus-like agent.     

A longitudinal serological survey of parvovirus infection in dogs

Serum samples collected from dogs routinely presented at a clinic between June 1974 and October 1980 were tested for the presence of haemagglutination inhibition (HI) titres to canine parvovirus. The first positive titre (>1:320) was demonstrated in serum collected in October 1979. The first confirmed clinical case of canine parvovirus enteritis was diagnosed by the authors in July 1979. In addition, between 1st December 1980 and 1st March 1981, serum samples were collected from 106 healthy dogs which were presented for canine parvovirus vaccination for the first time. Twenty-four dogs (approx. 23%) showed HI titres >1:320 indicating probable previous canine parvovirus infection. Therefore approx. 80% of dogs in the clinic area were at risk at that time and vaccination should have protected them from infection.     

Escherichia coli associated endotoxemia in dogs with parvovirus infection

Escherichia coli bacteremia and endotoxemia were observed in 3 adult mongrel dogs which had been prediagnosed as canine parvoviral disease. The endotoxin level was 46.5 pg/ml in the plasma of clinical cases, while 2.3 pg/ml in healthy controls. The microflora of the feces was confused in the clinical cases. The percentage of E. coli was major in the feces. Serologically similar strains were isolated from the blood. These strains did not produce enterotoxins such as heat-stable enterotoxin (ST) and heat-labile enterotoxin (LT). Histopathologically, the lesions in the small intestine consisted of epithelial degeneration and necrosis. Viral inclusion bodies were frequently observed in the epithelial cells. Disseminated intravascular coagulation was observed in various tissues including the liver and small intestinal submucosa. After experimental infection with CPV, all dogs showed various clinical signs. CPV was positive in the feces. Endotoxin level in the plasma gradually increased and high level continued for long period from 10 to 30 days. Mean maximum level of endotoxin in the experimental dogs was 73.6 pg/ml. These results indicate that intestinal flora plays a important role in the pathogenesis of CPV infection and that endotoxin is one of the factors which predispose to severe disease after the infection.     

Experimental parvovirus infection of puppies: immunohistological findings

Formalin-fixed tissue samples obtained from puppies experimentally infected with canine parvovirus type 2 (CPV-2) were investigated immunohistologically with the direct immunoperoxidase method. Besides cardiac muscle and lymphatic tissues, bone marrow, intestine, liver, kidney, pancreas and to a lesser degree lung stained positive for viral antigen and are considered as sites of viral replication. The distribution of viral antigen reveals a tropism of CPV-2 to numerous organs in puppies infected during the first week of life.     

Maternal antibody, vaccination and reproductive failure in dogs with parvovirus infection

Summary. The maternal antibody (MAb) titre to canine parvovirus (CPV) was determined on consecutive serums from 39 puppies in 7 litters. Vaccination with inactivated CPV was performed at a variety of ages and the response of the puppies determined. Transfer of MAb was demonstrated in 71% (5/7) of the litters and persisted for up to 10 weeks in some litters. MAb titres of >20 precluded a vaccination response by puppies. Sixty- one per cent (8/13) of puppies responded to vaccination when the MAb titre was <20. However, no anamestic response occurred and in some cases a decrease in antibody titre was observed following a second vaccination. During an outbreak of canine parvovirus enteritis (CPE) in the kennel, 33 puppies developed clinical signs of enteritis. Of these puppies 85% (28) had MAb titres of <80 at the onset of clinical signs. Fifty per cent (4/8) of the puppies which responded to vaccination developed CPE, whereas 100% (5/5) of those that did not respond to vaccination developed CPE.
The results indicate that MAb may persist for up to 10 weeks and puppies with MAb in the titre range >20 to <80 do not respond to vaccination but are still susceptible to infection. It is also apparent that a significant minority of puppies with MAb <20 do not respond to vaccination.
An examination of the breeding records of the kennel for the 7 year period 1973–1981 demonstrated a sudden decrease in reproductive efficiency during and subsequent to 1978. This coincided with the recognition of cases of CPV infection in the kennel. It is suggested that further investigation is required into the possible role of CPV in reproductive failure.
The authors would like to thank H. Findlay, P. Hinchliffe, G. Griffiths and S. MacPhail for technical assistance and Dr G. Wilcox and R. Flower for helpful discussion and advice.     

Experimental infection of Japanese encephalitis virus in dogs

A previous serosurvey of Japanese encephalitis virus (JEV) among dogs suggested that dogs are well suited for use as sentinels for assessing the risk of JEV transmission to humans. To examine the clinical symptoms and duration of anti-JEV antibodies in dogs, three dogs were experimentally challenged with JEV. All JEV-infected dogs did not show any clinical signs or abnormal blood tests, except for C-reactive protein. Virus-neutralization titers rapidly increased and were maintained until 70 days postinfection, and neither the virus nor the viral genome was detected in blood. Thus, since dogs live in close proximity to humans as companion animals, they are well suited for use as sentinels for surveying the human risk of JEV infection.     

Experimental infection of equine herpesvirus 9 in dogs

Equine herpesvirus 9 (EHV-9), a new neurotropic equine herpesvirus, was inoculated intranasally at 107 plaque-forming units in five dogs to assess its pathogenicity. Dogs showed weight loss, pyrexia, anorexia, and neurologic signs on the fourth day. The EHV-9 virus was recovered from the examined brains. Histologically, dogs had a fulminant nonsuppurative encephalitis characterized by severe neuronal degeneration and loss, with intranuclear inclusions, slight glial reactions, perivascular cuffing, and multifocal hemorrhage. The olfactory bulb and the frontal and temporal lobes were predominantly affected. Immunohistochemistry revealed reactivity for EHV-9 antigen in neurons. All dogs had mild bronchopneumonia and various degrees of lymphoid necrosis. These findings indicate that dogs are fully susceptible to EHV-9 and that EHV-9 can cause fulminant encephalitis with high mortality in dogs, as in gazelles and goats.     

Experimental Paragonimus kellicotti infection in dogs

The life cycle of Paragonimus kellicotti was studied in dogs fed 25 or 50 metacercariae obtained from the hearts of naturally infected crayfish. Young flukes excysted in the intestines and appeared in the peritoneal cavity within 7–14 days after inoculation (DAI) and in the pleural cavity from 7 to 43 DAI. Immature flukes penetrated the pulmonary parenchyma between 7 and 10 DAI and became sexually mature between 28 and 35 DAI. Virtually all growth of the flukes occurred in the lungs. Eggs first appeared in feces 30 DAI. Pulmonary lesions were caused by the penetration and growth of flukes and the lesions were first detected by thoracic radiography 3 weeks after inoculation. Clinical signs were generally mild and consisted of an intermittent cough. Two dogs died suddenly of pneumothorax due to the rupture of cysts 32 and 35 DAI, respectively.     

Canine parvovirus infection

Extract

Sir — Referring to M. H. Blunt's letter to the Journal for December, 1980 regarding canine parvovirus disease, I would like to take issue with several points.     

Experimental infection of dogs with Campylobacter jejuni

Three groups of conventional puppies were inoculated orally with Campylobacter jejuni biotype 2 which had been isolated from the small intestine of a dog with enteritis. Mild enteric disease was observed in one group. There was superficial intestinal colonization by the organism but penetration of intestinal epithelial cells was not apparent. C jejuni was isolated from the blood and viscera of inoculated dogs which showed no histological evidence of disease.     

Experimental infection of dogs with Brucella abortus

Thirteen female dogs, which included eight principals that were fed approximately 4.4 X 10(10) colony forming units (cfu) of Brucella abortus strain 2308 and five sentinels that were housed with the principals, were examined for serologic responses, blood culture, tissue distribution of the organisms and pathologic lesions. Serum samples from each dog were tested on the day of exposure and on post exposure days 5, 7, 10, 14, 21, 28, 35, 42 and 49 for antibodies to B. abortus, using the brucellosis card (BC), standard tube agglutination (STA), 2-mercaptoethanol (ME) and rivanol (RIV) tests. Antibodies were detected in the principals by day 5 and increased through day 21. The STA test was the first to become positive, followed by the BC, ME and RIV tests. After 28 days, the serologic titers receded. From day 14 through day 42, all principals had greater than or equal to 1:50 STA titers. On day 49, seven principals had greater than or equal to 1:50 STA titers and one had a 1:25 STA titer. The sentinels were negative for all tests, except sentinel number 9 which had STA titers ranging from 1:25 to 1:50 on day 14 through day 35. Blood cultures that were obtained from each principal at intervals from one hour after exposure through 49 days were negative. Brucella abortus was isolated from various lymph nodes of the eight principals and from sentinel number 9, which was apparently infected by ingesting brucellae contaminated feces from the principals. Microscopic lesions were not observed in the culture-positive tissues examined.     

Canine parvovirus infection in Nigeria

Pups of Nigerian mongrel dogs randomly bought from two village markets for experimental purposes at the University of Nigeria, Nsukka, were observed to be ill within 4 days of purchase. By 13 days after purchase 52.5 per cent of all the animals had died. All sick animals were anorectous and suffered from diarrhoea. The faeces were mostly dark yellow to light brown and a few contained spots of blood. Few animals responded to treatment with fluids, antibiotics and vitamins and death occurred within 24 hours of the onset of clinical signs. In most cases, post mortem and histopathological lesions were similar to those characteristic of canine parvovirus. The sera of the surviving animals tested for haemagglutination-inhibition antibodies to canine parvovirus, using porcine red blood cells, were positive.     

Suspected parvovirus infection in porcupines

During a 142-day period, 6 porcupines died or were killed after becoming moribund. Three had severe acute necrotizing enteritis; two had acute necrotizing myocarditis, one with concurrent lymphocytic-plasmacytic enteritis; and one had chronic enteritis. Histologically, the acute necrotizing enteritis was characterized by villous fusion, blunting, and crypt dilatation. Many dilated crypts contained necrotic debris and were lined by flattened enterocytes. Acidophilic intranuclear inclusions were in colonic epithelial cells in one of these animals. The myocardial lesions consisted of degenerating shrunken myofibers, with infiltrating neutrophils and lymphocytes. Myofiber mineralization was evident in one animal. Though the histologic findings were indicative of parvovirus infection, electron microscopic, serologic, and virologic studies failed to demonstrate parvovirus as the etiologic agent.