Inhibition of 7,12-dimethylbenz(a)anthracene-induced tumors in Syrian hamsters by prior infection with H-1 parvovirus

Hamsters, given injections s.c. at birth of H-1 parvovirus and 1 month later given a single injection of 7,12-dimethylbenz(a)anthracene, had a 38% tumor incidence compared with a 95% incidence in animals receiving 7,12-dimethylbenz(a)anthracene alone. Thus, H-1 which, it has already been shown, invokes a resistance to the incidence of spontaneous and adenovirus-induced neoplasms in hamsters also produces a suppression of a carcinogen-induced tumor in these animals; this suggests that the H-1-induced barrier to successful oncogenesis by these diverse agents has a common mechanism which, present experiments indicate, is not related to a positive or negative H-1 serology. The pathology of the 7,12-dimethylbenz(a)anthracene-induced tumors was similar for both control and H-1-infected hamsters. Although all but one of the primary neoplasms were anaplastic fibrosarcomas as reported previously by others, 25% of the affected females had, in addition, mammary adenocarcinomas, an extremely rare tumor in hamsters.

Canine parvovirus infection in Australia during 1980

A questionnaire sent to all veterinary practitioners in Australia and many in New Zealand asking for details of their experience with canine parvovirus infections in 1980 elicited the following information. In 1980 explosive outbreaks of disease occurred in most parts of Australia. There was no obvious pattern of spread over the continent as a whole. In many cases outbreaks in country areas occurred after dog shows. Canine parvovirus enteritis affected all age groups with an overall mortality of 16 per cent. While the death rate in the young was high, most dogs responded well to fluid therapy. Canine parvovirus did not appear to be associated with clinical entities other than gastroenteritis and myocarditis. No connection with reproductive problems was established. Killed canine parvovirus vaccines were used extensively after the initial release for sale in July 1980. The vaccines appeared to be safe and effective at least in the short term. Problems arose only in vaccination of very young animals.

[Parvovirus enteritis and myocarditis in a confined colony of beagles. (The 1st detection of parvovirus infection in Czechoslovakia]

A description of the findings in a parvoviral epizooty, having occurred in a confined colony of 250 Beagle dogs in the autum and winter 1979-1980 and in 1981, is presented. 5 of the four month-old and older dogs perished in the course of an enteritic form of infection; 5 puppies, younger than 3 months, belonging to a group of 12 puppies derived from two infected litters, died in consequence of a parvoviral myocarditis. The simultaneous occurrence of myocarditis and enteritis was observed in a 9 day-old puppy. Among the seven remaining animals, two dogs were sacrificed at the ages of 18 and 23 months, respectively. Scars were found in the wall of the left ventricle of both of them. Parvoviral enteritis preceded the occurrence of parvoviral myocarditis. Characteristic intramuscular inclusions were demonstrated both in the enterocytes and in the myocardial cells. Electronmicroscopically particles of the size of the parvoviruses could be demonstrated in the nuclei of the myocardial cells, on one hand, and regressive changes of the nuclear components observed on the other hand.

[Acute viral enteritis in dogs]

The results of a post-mortem examination of 15 dogs suffering from acute viral infection probably of parvoviral etiology, are described. The characteristical finding was an acute catarhally hemorrhagic or even a hemorrhagically necrotic enteritis, eventually a colitis with isolated intranuclear inclusions in the epithelium of the crypts, there was also a marked depletion of lymphocytes in the lymphatic organs and some atrophy of the bone marrow.

Experimental infection of conventional dogs with canine parvovirus

Four 6-week-old conventional pups were inoculated with a parvovirus (PV) isolated from the feces of a dog with naturally occurring enteritis. Blood for hematologic studies, virus isolation (VI), and antibody titration and feces for VI and negative-contrast electron microscopy were collected on day 0 and daily until necropsy. Beginning at postinoculation day 2, necropsies were done and specimens were collected for immunofluorescence, VI, and light microscopic examination. The PV infection was confirmed by VI, immunofluorescence, electron microscopy, and seroconversion. Clinical illness was not observed in inoculated pups, although mild intestinal lesions similar to those of naturally occurring PV enteritis were found. The failure to elicit severe disease in conventional pups indicates that one or more factors, such as intercurrent enteric or systemic infections, immune status, age, nutrition, virulence of virus, dose of infectious virus, and route of inoculation influence the clinical and pathologic manifestations of PV infection.

Canine parvovirus infection potentiates canine distemper encephalitis attributable to modified live-virus vaccine

Twelve gnotobiotic dogs from 2 litters were allotted to 3 groups. Group A dogs received a modified-live polyvalent (canine distemper, adenovirus type 2, and parainfluenza virus and Leptospira -canicola-icterohemorrhagiae bacterin) vaccine 3 days prior to oral inoculation with canine parvovirus (CPV). Group B dogs received CPV alone. Group C dogs received 1 dose of vaccine only. In none of the 9 CPV-inoculated dogs did clinical signs of CPV infection develop, although high serum antibody titers for CPV developed in all of them. However, in 2 of the 5 CPV-inoculated vaccinates, canine distemper virus encephalomyelitis subsequently developed. The results suggested that CPV exerts an immunomodulating effect on canine immune responses and may be responsible for vaccination failures in dogs.

Radiographic appearance of canine parvovirus enteritis

Sixty dogs with serologically proved parvovirus infection were radiographically evaluated for signs of gastrointestinal disease. Patient grouping was based on duration of illness, which correlated generally with severity of clinical signs. Early in the disease, the radiographic appearance usually was normal. As the disease progressed, abnormal gas and fluid distention of the small bowel became evident. Contrast radiographic findings usually were normal early in the disease but became abnormal as the disease progressed. Vomiting of the contrast agent, delayed gastrointestinal transit time, flocculation, and abnormal bowel patterns were observed frequently. It was concluded that noncontrast radiographic features of canine parvovirus enteritis often were similar to those identified in other gastrointestinal disorders and, therefore, were not always specific for the disease. Results of contrast radiography, however, were highly specific for parvovirus enteritis. Intestinal contrast examination was believed to be a reliable means of differentiating parvovirus enteritis from clinically similar disorders and in ruling out primary or secondary intestinal obstruction. The duration of illness was correlated with the number, severity, and nature of radiographic signs.

Toxigenic Clostridium perfringens from a parvovirus-infected dog

A strain of Clostridium perfringens, type A, has been isolated from the intestine of a dog which died from parvovirus infection. This Clostridium strain produces a toxin which can be detected by counterimmunoelectrophoresis, using C. difficile antitoxin, and produces cytotoxicity in WI-38 cell culture. Cytopathology can be blocked by C. difficile antitoxin. Its role in canine parvovirus infection is unknown.

Reproductive performance of gilts exposed to porcine parvovirus at 56 or 70 days of gestation

A total of 18 pregnant gilts, which were free of antibody for porcine parvovirus (PPV), were exposed oronasally to PPV on either the 56th day (9 gilts) or 70th day (9 gilts) of the gestation to determine whether infection at these times would affect their reproductive performance. The gilts were either necropsied late in gestation or allowed to farrow, and their fetuses and pigs were tested for evidence of infection. Gilts remained clinically healthy throughout the experiment, and none farrowed prematurely. litters of 7 of 9 gilts exposed to PPV at 56 days of the gestation were infected transplacentally, and PPV caused death of fetuses in 5 of the infected litters. These litters comprised 29 dead fetuses (2 to 12/litter) and 31 live fetuses or pigs (1 to 10/litter). In addition, PPV may have been directly or indirectly responsible for an increased frequency of stillbirth and neonatal death, but the role of PPV in these conditions was difficult to assess. Litters of 6 to 9 gilts exposed to PPV at 70 days of the gestation also were infected transplacentally, but in contrast to earlier infection, PPV did not cause fetal death in these litters.

Activity of some enzymes involved in "adenylate cycle" in rat embryo cells infected with parvoviruses (X14, H-1)

In rat embryo cell cultures infected with X14 or H-1 parvovirus and in mock-infected cell cultures the activity of some enzymes involved in purine nucleotide interconversion and in "adenylate cycle" was determined. The enzymatic activities have been assayed on 100,000 x g supernatant by spectrophotometric methods, measuring the absorbance variation in U.V. and by radiometric methods, resolving the radioactive products of reaction by TLC on PEI cellulose. The results indicated a decrease of the enzymatic activities that degrade purine nucleosides and nucleotides in infected cells compared to the controls. Some different behaviour patterns showed the enzymes involved in base salvage pathway; adenine phosphoribosyltransferase did not show a significant modification of activity, whereas hypoxanthine (guanine) phosphoribosyltransferase increased slightly in X14 virus-infected cells. The behaviour of the above mentioned enzymatic activities may be considered as a mechanism of purine nucleotide saving, coupled to an active salvage pathway for the synthesis of nucleotides required for the viral replication.

Pool and synthesis of phosphoribosylpyrophosphate in rat embryo cells infected with X14 or H-1 parvovirus

In rat embryo cell cultures infected with X14 or H-1 parvovirus the PRPP pool and the PRPP synthetase activity have been assayed. A radiometric method, prepared by Authors, based on the conversion of [6-14C) orotate to [6-14C) UMP by the mixed enzyme orotate phosphoribosyltransferase and orotidylate decarboxylase and on the separation of UMP by ascending chromatography, has been utilized. The PRPP pool and te PRPP synthetase activity appeared nearly unmodified in the cells infected with X14 or H-1 parvovirus compared to the mock-infected cells. Therefore, the lowered pyrimidine nucleotide synthesis in infected cells, shown in previous studies, may depend, rather than on the diminished PRPP pool, on the lower PRPP utilization; in fact, some inhibition by metabolites, that may be removed by added PRPP, might occur in the infected cells.

Outbreak of aplastic crises in sickle cell anaemia associated with parvovirus-like agent

Since 1952, 112 children with sickle cell anaemia (SCA) in Jamaica have had an aplastic crisis. Outbreaks occurred in 1956, 1960, 1065-67, 1971-73, and 1979-80. Most cases occurred in children under 10 years of age, and an aplastic crisis in a patient over the age of 15 years is rare. There were 38 cases in 1979-80 and stored serum specimens from 28 of these were available for virus studies. Evidence for infection with a parvovirus-like agent was found in 24 of these 28 cases. Viral antigen was detected in 2 patients, both of whom demonstrated seroconversion. Seroconversion during 1980 was detected in a further 7, increasing amounts of antibody during the convalescent period were found in 5, antibody was found in 2 of 4 patients from whom only an acute phase specimen was available and the remaining 10 were antibody positive in the only convalescent phase sample available for testing. Antibody was found in 4 of 94 controls with the SS genotype (in retrospect 2 of these may have had an aplastic crisis) and in 17% of 48 controls with a normal haemoglobin (AA) genotype. The results accord with the possibility that the parvovirus-like agent is the principal cause of aplastic crisis in SCA.

Secondary infection of rat lungs with Pasteurella pneumotropica after Kilham rat virus infection

Lung congestion was observed after an outbreak of Kilham rat virus infection (KRV) in a rat colony, previously free of all rat viruses. A high proportion of congested lungs contained Pasteurella pneumotropica suggesting that KRV might have caused primary damage to the alveoli (hitherto not recorded) which allowed the secondary bacterial colonization. Experimental infection of rats with KRV caused acute damage to the lung alveoli. Since KRV infection is very common in animal facilities it could therefore be a significant agent in the development of respiratory disease.

Experimental parvovirus infection in dogs

Five eight week old dogs were inoculated orally and intranasally with cell culture origin canine parvovirus. Three dogs became depressed and anorectic and developed a mild (one dog) to severe diarrhea five days postinfection. The remaining dogs had subclinical infections but developed a lymphopenia followed by a transient lymphocytosis. The ill dogs developed mild (one dog) to severe neutropenia and a moderate lymphopenia. One died nine days postinfection. Recovery was associated with cessation of viral excretion and with lymphocytosis and antibody production. Two of three dogs challenged intragastrically developed mild clinical signs and a moderate panleukopenia four to eight days postinfection. The pathological changes of the experimental disease were very similar to that of spontaneous disease. Bone marrow changes included a severe granulocytic and mild erythroid depletion. The pathogenesis of canine parvovirus infection is discussed.