Persistent infection of turkeys with an avirulent strain of turkey hemorrhagic enteritis virus

The Virginia avirulent strain (VAS) of turkey hemorrhagic enteritis virus (THEV), which is commonly used in live vaccines for commercial turkeys, was studied to determine characteristics of infection. It has been observed that turkeys infected with the VAS maintain protective antibody levels in excess of 20 wk postvaccination. It is theorized that this immune response is modulated by either a persistent or latent infection. A series of studies have been undertaken to determine changes in virus location and serology over time. A trial was also conducted to evaluate the effect of corticosteroid administration on viral recrudescence, and an attempt was made to isolate live virus from tissues of birds 10 wk postinfection (pi). Antibody titers were determined by enzyme-linked immunosorbent assay, and PCR was used to detect viral DNA. Histopathology was performed on formalin-fixed paraffinized tissues. Viral DNA was detected in various tissues through 15 wk pi in the presence of high antibody titers. Viral DNA was detected at 3-5 days pi in the spleens of susceptible turkeys inoculated with tissues collected from infected birds at 10 wk pi. It is unknown whether the viral DNA is associated with live virus or rather is the result of persistent maintenance of the viral genome within lymphoid/macrophage target cells. Future studies will test for viral RNA in order to confirm the presence of replicating THEV. Regardless of the actual status of the THEV DNA detected at 10-15 wk pi, it is clear that THEV does not cause a simple acute infection. The characteristics of THEV infection are identical to the nonlytic persistent infections seen in human adenoviruses, and therefore THEV may serve as a model for the study of virus-cell interactions mediating persistence.

Comparative pathogenesis in specific-pathogen-free chickens of two strains of avian hepatitis E virus recovered from a chicken with Hepatitis-Splenomegaly syndrome and from a clinically healthy chicken

Avian hepatitis E virus (avian HEV) is the primary causative agent of Hepatitis-Splenomegaly (HS) syndrome in chickens. Recently, a genetically unique strain of avian HEV, designated avian HEV-VA, was recovered from healthy chickens in Virginia. The objective of this study was to experimentally compare the pathogenicity of the prototype strain recovered from a chicken with HS syndrome and the avian HEV-VA strain in specific-pathogen-free chickens. An infectious stock of the avian HEV-VA strain was first generated and its infectivity titer determined in chickens. For the comparative pathogenesis study, 54 chickens of 6-week-old were assigned to 3 groups of 18 chickens each. The group 1 chickens were each intravenously inoculated with 5x10(2.5) 50% chicken infectious dose of the prototype strain. The group 2 received the same dose of the avian HEV-VA strain, and the group 3 served as negative controls. Six chickens from each group were necropsied at 2, 3 and 4 weeks post-inoculation (wpi). Most chickens in both inoculated groups seroconverted by 3wpi, and the mean anti-avian HEV antibody titers were higher for the prototype strain group than the avian HEV-VA strain group. There was no significant difference in the patterns of viremia and fecal virus shedding. Blood analyte profiles did not differ between treatment groups except for serum creatine phosphokinase levels which were higher for prototype avian HEV group than avian HEV-VA group. The hepatic lesion score was higher for the prototype strain group than the other two groups. The results indicated that the avian HEV-VA strain is only slightly attenuated compared to the prototype strain, suggesting that the full spectrum of HS syndrome is likely associated with other co-factors.

Vaccination with gamma-irradiated Neospora caninum tachyzoites protects mice against acute challenge with N. caninum

Neospora caninum, an apicomplexan parasite, is a leading cause of bovine abortions worldwide. The efficacy of gamma-irradiated N. caninum strain NC-1 tachyzoites as a vaccine for neosporosis was assessed in C57BL6 mice. A dose of 528 Gy of gamma irradiation was sufficient to arrest replication but not host cell penetration by tachyzoites. Female C57BL6 mice were vaccinated with two intraperitoneal inoculations of 1 x 10(6) irradiated tachyzoites at 4-wk intervals. When stimulated with N. caninum tachyzoite lysates, splenocytes of vaccinated mice, cultured 5 and 10 wk after vaccination, secreted significant (P<0.05) levels of interferon gamma, interleukin (IL)-10, and small amounts of IL-4. Antibody isotype-specific ELISA of sera from vaccinated mice exhibited both IgG1 and IgG2a isotypes of antibodies. Vaccinated mice were challenged intraperitoneally with 2 x 10(7)N. caninum tachyzoites. All vaccinated mice remained healthy and showed no obvious signs of neosporosis up to the 25th day post-challenge when the study was terminated. All unvaccinated control mice died within 1 wk of infection. Gamma-irradiated N. caninum tachyzoites can serve as an effective, attenuated vaccine for N. caninum.

Utility of diagnostic tests used in diagnosis of infection in dogs experimentally inoculated with a North American isolate of Leishmania infantum infantum

Eight female beagles were infected with 1 x 10(7) (low dose, LD) or 2 x 10(8) (high dose, HD) promastigotes of a North American isolate of Leishmania infantum infantum (LIVT-1 strain) isolated from naturally infected Virginia Foxhounds. Two female beagles served as negative controls and 2 male beagles chronically infected (> 3 years) with Leishmania infantum chagasi were positive controls. Bone marrow (BM) and lymph node (LN) aspirates were collected every 6-8 weeks for cytologic evaluation, parasite culture, and polymerase chain reaction (PCR). Serum samples were collected monthly for determination of serologic responses by indirect fluorescent antibody test (IFAT) and diagnostic rK39 antigen. Cultures of BM and LN aspirates and cytology evaluation were consistently positive in positive control dogs during the course of study. Negative control dogs were negative on BM and LN cultures and on cytologic evaluation of aspirates. Amastigotes were present on cytological examination of BM aspirates in 2 experimentally infected dogs. Cultures of LN aspirates were positive on 22 samples, whereas BM cultures were positive on 12 samples for all dogs. IFA titers ranged from 0 to 1 :400 in experimentally infected dogs during the course of the study. Recombinant K39 immunoassay tests were consistently positive in positive control dogs and in the HD dogs by approximately 8 weeks after infection. BM PCR products were identified more consistently in the HD dogs compared with the LD dogs. Kappa statistics indicated PCR correlated better with cultures and cytology than did IFAT or the rK39 immunoassay results in the experimentally infected dogs.

Systematic pathogenesis and replication of avian hepatitis E virus in specific-pathogen-free adult chickens

Hepatitis E virus (HEV) is an important human pathogen. Due to the lack of a cell culture system and a practical animal model for HEV, little is known about its pathogenesis and replication. The discovery of a strain of HEV in chickens, designated avian HEV, prompted us to evaluate chickens as a model for the study of HEV. Eighty-five 60-week-old specific-pathogen-free chickens were randomly divided into three groups. Group 1 chickens (n=28) were each inoculated with 5 x 10(4.5) 50% chicken infectious doses of avian HEV by the oronasal route, group 2 chickens (n=29) were each inoculated with the same dose by the intravenous (i.v.) route, and group 3 chickens (n=28) were not inoculated and were used as controls. Two chickens from each group were necropsied at 1, 3, 5, 7, 10, 13, 16, 20, 24, 28, 35, and 42 days postinoculation (dpi), and the remaining chickens were necropsied at 56 dpi. Serum, fecal, and various tissue samples, including liver and spleen samples, were collected at each necropsy for pathological and virological testing. By 21 dpi, all oronasally and i.v. inoculated chickens had seroconverted. Fecal virus shedding was detected variably from 1 to 20 dpi for the i.v. group and from 10 to 56 dpi for the oronasal group. Avian HEV RNA was detected in serum, bile, and liver samples from both i.v. and oronasally inoculated chickens. Gross liver lesions, characterized by subcapsular hemorrhages or enlargement of the right intermediate lobe, were observed in 7 of 28 oronasally and 7 of 29 i.v. inoculated chickens. Microscopic liver lesions were mainly lymphocytic periphlebitis and phlebitis. The lesion scores were higher for oronasal (P=0.0008) and i.v. (P=0.0029) group birds than for control birds. Slight elevations of the plasma liver enzyme lactate dehydrogenase were observed in infected chickens. The results indicated that chickens are a useful model for studying HEV replication and pathogenesis. This is the first report of HEV transmission via its natural route in a homologous animal model.

Complex vertebral malformation in a holstein calf: report of a case in the USA

Complex vertebral malformation (CVM), a familial syndrome of Holstein calves, has been reported in aborted fetuses and in prematurely born, stillborn, and neonatal calves. Affected calves have anomalies in the vertebral column, including hemivertebrae, fused and misshapen vertebrae and ribs, scoliosis, and vertebral synostosis. Concurrent low body weight, symmetrical arthrogryposis, and cardiac anomalies have been documented in affected calves. The syndrome was identified and characterized in Holstein cattle in Denmark; however, a global distribution of this genetic disorder is likely based on identification of common ancestral sires widely used for artificial insemination. This is the first documented case of CVM in a Holstein calf in the USA.

Molecular characterization of a Cryptosporidium isolate from a black bear

To further validate the observation of the existence of host-adapted strains of Cryptosporidium parvum, we genetically characterized an isolate of Cryptosporidium parasite from a black bear. Sequence analysis of the ribosomal RNA small subunit and the 70-kDa heat shock protein (HSP70) showed that this parasite represents a new genotype of C. parvum and is related to the C. parvum dog genotype. This finding is helpful for clarifying Cryptosporidium taxonomy.

Neospora hughesi: experimental infections in mice, gerbils, and dogs

Neospora hughesi is a recently described cause of equine protozoal myeloencephalitis (EPM). A rodent model for pathogenicity would facilitate development of therapies to be used in horses. In the present study, we examined the susceptibility of BALB/c gamma-interferon gene knockout (gamma-INFKO), BALB/c, CD-1, and C57BL/6 strains of mice and gerbils to infection with tachyzoites of the Nh-A1 strain of N. hughesi isolated from a horse from AL, USA. Only the gamma-IFNKO mice developed severe clinical disease following infection with N. hughesi and died 19-25 days after infection and exhibited severe cardiac lesions. In contrast, experimental infection of gamma-INFKO mice with tachyzoites of the NC-1 or NC-Liverpool strains of Neospora caninum resulted in deaths 8-10 days after infection. The most severe lesions were in the livers, spleens, and lungs of these mice. Gerbils inoculated with N. hughesi did not develop clinical disease, had few microscopic lesions, but did seroconvert. Two dogs fed the brains of mice, shown to contain N. hughesi tissue stages by cell culture and gamma-IFNKO mouse bioassay, did not shed N. caninum-like oocysts over a 23 days observation period. The marked difference in pathogenicity between the two species of Neospora in gamma-IFNKO mice, and lack of oocyst excretion by dogs fed N. hughesi infected mice provide additional evidence that the species distinction between N. caninum and N. hughesi is valid.

Acute sarcocystosis in a captive white-tailed deer in Virginia

A 19-mo-old female captive white-tailed deer in a public wild animal park in Richmond (Virginia, USA) was necropsied and evaluated histologically following spontaneous death after a 1 wk period of lethargy in a captive herd of 22 deer. An acute necrotizing pneumonia was associated with intraendothelial protozoal schizonts that were identified immunohistochemically as Sarcocystis spp. This is the first confirmed report of acute sarcocystosis in a wild ruminant.

The gastroduodenal effects of buffered aspirin, carprofen, and etodolac in healthy dogs

Twenty-four healthy mixed-breed dogs were divided into 4 groups. Group 1 received a placebo p.o. q12h, group 2 received an average of 16.5 (15.1-17.8) mg/kg buffered aspirin p.o. q12h, group 3 received an average of 2.2 (2.0-2.4) mg/kg carprofen p.o. q12h, and group 4 received an average of 12.8 (11.7-13.8) mg/kg etodolac p.o. q24h (with a placebo in the PM). All treatments continued for 28 consecutive days. Gastroduodenal endoscopy was performed on days -9, 0, 5, 14, and 28. Multiple gastric biopsies were obtained endoscopically on day -9 to determine each dog's Helicobacter infection status. Four regions in the stomach and 1 region in the proximal duodenum were evaluated endoscopically, and each was assigned a score from 1 to 11. Scores for each region then were summed to give a total score for each endoscopic evaluation. Erosions and submucosal hemorrhages were seen in all dogs receiving aspirin. Only minor gastric lesions were observed in the carprofen, etodolac, and control groups. No adverse clinical signs were noted in any dog given any treatment. Median total score on days 0, 5, 14, and 28, respectively, were as follows: group 1: 5.0, 5.0, 5.0, 5.0; group 2: 5.0, 27.0, 26.0, 27.5; group 3: 5.0, 5.0, 6.0, 5.0, group 4: 5.0, 7.0, 5.0, 5.0. There was no significant difference among dogs receiving carprofen, etodolac, or placebo. The administration of carprofen, etodolac, or placebo to healthy dogs resulted in significantly less gastroduodenal lesion development than in dogs receiving buffered aspirin.

Characterization of metastatic intestinal adenocarcinoma with differentiation into multiple morphologic cell types in a Virginia opossum

A captively maintained mature male opossum (Didelphis virginiana) utilized in a research protocol was presented with clinical signs of chronic diarrhea and severe muscle wasting. At necropsy, there was multifocal mural gastric, intestinal, and urinary bladder thickening, concurrent bilateral hydroureter and hydronephrosis, and extensive fibrous abdominal adhesions. Histologic evaluation revealed intestinal adenocarcinoma with coelomic metastasis to the stomach and urinary bladder. The adenocarcinoma was evaluated using histochemistry and electron microscopy. Paneth, enteroendocrine, and goblet cell differentiation was documented in primary and metastatic sites. This unique presentation of intestinal adenocarcinoma has not previously been reported in the opossum or any other animals. Intestinal neoplasia with Paneth cell differentiation is extremely rare and has been reported in humans with familial adenomatous polyposis.

Analysis of ruminant respiratory syncytial virus isolates by RNAse protection of the G glycoprotein transcripts

Two different respiratory syncytial virus (RSV) radiolabeled probes were used to characterize the genetic heterogeneity of 25 ruminant RSV isolates by the ribonuclease protection assay. A 32P-radiolabeled antisense RNA probe was transcribed from cloned ovine and bovine RSV G glycoprotein genes and then hybridized with total RNA isolated from infected cells with various ruminant RSV isolates. The results of this study, along with previously published nucleotide sequence data of the ovine RSV G glycoprotein gene, suggest the presence of at least 2 ruminant RSV subgroups. One subgroup is represented by RSV isolated from respiratory disease outbreaks from calves and goats, and the other is represented by RSV isolated from sheep.

Confirmation that the dog is a definitive host for Neospora caninum

Two mixed-breed littermate dogs were fed mouse brains containing tissue cysts of the NC-beef isolate of Neospora caninum. Both dogs excreted N. caninum oocysts in their feces. Dog 1 which was given methylprednisolone acetate (MPA) prior to ingesting tissue cysts, excreted oocysts on days 5 to 10 inclusive and on day 17 after ingesting tissue cysts. Dog 1 had a serum antibody titer of 1:200 in the indirect fluorescent antibody test (IFAT) 35 days after it was fed tissue cysts. Dog 2, which was not treated with MPA, excreted oocysts on Day 6 and Day 9 after ingesting tissue cysts. Antibodies to N. caninum were not found in a 1:25 dilution of serum on any examination period for Dog 2 during the study. Neospora caninum was not found in the tissues of either dog by histological or immunohistochemical means following necropsy 42 days after being fed tissue cysts. The identity of the oocysts excreted in the feces of the dogs was confirmed by mouse inoculation studies.

Cryptosporidiosis in a black bear in Virginia

Cryptosporidiosis has not been previously reported in black bears in North America, either free-roaming or captive. However, oocysts have been documented in two captive Malayan sun bears (Helarctos malayanus) located in zoological parks in Taiwan. Developmental stages of Cryptosporidium parvum were observed in tissue sections from the small intestine of a black bear cub found dead in Virginia (USA).

Solitary osteochondroma of the nasal bone in a horse

A 3-year-old Appaloosa stallion with a 4 cm x 4 cm x 2.5 cm mass protruding from his nasal bone was evaluated. Radiographs revealed an osseous mass, with a radiopaque outer margin and several radiolucent areas within the body of the mass. The mass was surgically removed and evaluated histopathologically. The histopathological diagnosis was osteochondroma. This case represent the first reported occurrence of an osteochondroma arising from intramembraneous bone in the horse.

Antigenic diversity of respiratory syncytial viruses and its implication for immunoprophylaxis in ruminants

Bovine respiratory syncytial virus (BRSV) is a very important pathogen of cattle and perhaps other ruminants. It is a major contributor to the incidence of respiratory tract disease in nursing beef and feedlot and dairy calves. The genome of respiratory syncytial viruses encodes 10 proteins translated from 10 unique mRNAs. The major glycoprotein (G), fusion protein (F), 1A protein and the 22K protein are components of the viral envelope. The nucleocapsid contains the nucleocapsid protein (N), the phosphoprotein (P), and the large protein (L). The matrix protein (M) forms a structural layer between the envelope and the nucleocapsid. Antibodies to all the structural proteins develop in convalescent calves. However, evidence suggests that immunity develops primarily as a result of the antigenic stimulus by the major glycoprotein G and the fusion glycoprotein F. It is known also that activated cytotoxic T cells interact with N and F protein antigens and helper T cells interact with N, F, and 1A protein antigens. With the exception of the major glycoprotein, the respective proteins of various respiratory syncytial viruses share major antigenic domains. Based on antigenic differences of the major glycoprotein, at least 3 subgroups of RSV are recognized; human A, human B, and bovine RSV. Indirect evidence suggests that a second subgroup of BRSV exists. However, we have identified only one BRSV subgroup based on our work with RNase mismatch cleavage analysis of the G protein gene from a limited number of strains. Furthermore, our data indicated that a caprine RSV isolate is closely related to the bovine strains, but an ovine isolate is not. The latter may constitute yet another subgroup of RSV. These data affect decisions on optimization of immunoprophylaxis since evidence suggests that protection against a homologous RSV subgroup virus is superior to that against a heterologous strain in immune subjects.

Pulmonary hypertension in a group of dairy calves

An episode of pulmonary arteritis and sclerosis in twenty 5- to 6-month-old dairy calves was investigated. Sixteen of the calves died acutely, without marked premonitory signs of disease. Four calves evaluated clinically had lethargy, pallor, weakness, tachycardia, tachypnea, and jugular venous distention. Cardiac catheterization performed in 3 of the calves revealed pulmonary hypertension; 1 of these calves survived. Necropsy findings in 19 calves included pale lungs and excess free fluid in the pleural and abdominal cavities. In addition, 13 of 19 calves had a dilated and thin-walled right ventricle; 4 of the calves had right-sided cardiac hypertrophy, and 2 had dilatation of the pulmonary artery. Microscopically, pulmonary arteritis and sclerosis of the small to medium-sized arteries were evident in all calves submitted for necropsy. A lung biopsy specimen from a surviving calf had similar lesions. Centrilobular hepatic necrosis was found in 17 of 19 calves. Investigation of the disease episode, including feed analysis for toxins and serologic and microbiological studies of clinically affected calves and clinically normal in-contact penmates, failed to reveal any associated risk factor. The pulmonary arterial changes in the calves were similar to lung lesions in rats fed monocrotaline.

Fatal lungworm infection in an opossum

A 3-mo-old male, feral opossum (Didelphis virginiana) was presented to the University of Tennessee College of Veterinary Medicine (USA) for evaluation of prolonged dyspnea. The animal died shortly after examination and a necropsy was performed. The cause of death was attributed to a verminous pneumonia, associated with numerous intrabronchial and intrabronchiolar nematodes, subsequently identified as Didelphostrongylus hayesi.

Malleus handle probe: a middle ear diagnostic procedure

Manual probing of the malleus handle (MH) of 477 patients suggests a protective middle ear reflex with a variable tonic contraction of the tensor tympani muscle (TTM). The degree and type of MH retraction suggests three stages of progressive middle ear inflammation. Prediction accuracy of 250 myringotomy findings was 60% with impedance audiometry and 92% with MH probing. Mechanical pressure gauge readings (grams) of 202 ears correlated with finger pressure estimations. The TTM tendons were sectioned in ten children with persisting otitis media with effusion (OME) and seven obtained benefit. The three diagnostic methods, pneumatic otoscopy, impedance audiometry and MH probing, assess similar and separate perimeters and are complementary. Malleus handle probing alone detects attic loculation of OME, 54 of 954 ears (5.6%). it extends the diagnostic range to the TTM activities.

Bony auditory tube and otitis media with effusion

The author has for 25 years manually probed the malleus handle for indications of middle ear pathology. Dissection of the bony auditory tube (BAT) and isthmus comprised 120 fresh autopsy and 26 anatomically prepared temporal bones. The semicanal lamina was not completely ossified in all infants and children and 52% of adults. The tensor tympani muscle was edematous and prolapsed into the superior portion of the BAT in eight ears with otitis media with effusion. Infants and children have the tendon of the tensor tympani muscle inserting into the neck of the malleus at an angle of 60 degrees or greater, possibly explaining the relatively large muscle bulk. It is suggested from these autopsy findings that the BAT and isthmus lumen is a functional 2-way channel for air superiorly and mucus streaming inferiorly. Manual palpation of the cartilaginous auditory tube in infants did not suggest malacia.

Otolaryngeal allergy in Wellington. 1971-1975

Two thousand and twenty-nine patients received allergic therapy 1971-1975. Nine hundred and eighty-nine were followed up six to 24 months later. All received Rinkel's inhalant skin titration method. The first group 1971-1972 of 309 patients were investigated with Lee's food provocation method and useful relief of symptoms occurred in 27.6 per cent of patients. The second group 1973-1975 of 680 patients were investigated with Bryan's cytotoxic food test, 60 percent reported very good relief and 26 percent useful relief of symptoms. Successfully treated patients were able to curtail or abandon drug therapy and the frequency of surgery was decreased. The authors believe allergic symptoms are of common occurrence in patients frequently seeking medical attention.