Naturally occurring Sarcocystis neurona-like infection in a dog with myositis

Tissue stages similar to those of Sarcocystis neurona, the causative agent of equine protozoal myeloencephalitis, were identified in skeletal muscles of a dog. The dog, a 6-year-old Labrador retriever, was seropositive for Toxoplasma gondii infection and euthanized due to a history of polymyositis and progressive muscular atrophy. Histologically, 30, variably sized, microscopic, intracellular sarcocysts were observed in 60 sections of skeletal muscles taken from the neck, fore limbs and hind limbs. The cysts were only observed in inflamed skeletal muscles, but were mostly in myocytes at the periphery of areas infiltrated with leukocytes. Ultrastructurally, the cyst wall had villar protrusions consistent with sarcocysts. Immunohistochemistry with monoclonal S. neurona antibodies demonstrated positive labeling of zoites in merozoites or schizonts in the skeletal muscle interstitium, but no labeling of the sarcocysts. Initial PCR analysis with primers amplifying a genetic sequence encoding Apicomplexan 18s rRNA, and subsequent PCR analysis with differentiating primers indicated that the genetic sequences had 100% identity with sequences reported for S. neurona.     

Hematologic values in calves infected with Sarcocystis cruzi

Calves were inoculated with 2 X 10(5) Sarcocystis cruzi sporocysts. Red cell mass decreased dramatically between Days 21 and 35 post-infection and plasma volume increased concurrently, so that blood volume did not change significantly. Mild reticulocytosis and increased pyrimidine 5' nucleotidase activity in erythrocytes occurred between Days 35 and 42. Antiglobulin tests with anti-bovine IgG, IgM and C3 were negative, with the exception of a positive test for C3 in 1 of 6 infected calves.     

Immune response to Sarcocystis neurona infection in naturally infected horses with equine protozoal myeloencephalitis

Equine protozoal myeloencephalitis (EPM) is one of the most common neurologic diseases of horses in the United States. The primary etiologic agent is Sarcocystis neurona. Currently, there is limited knowledge regarding the protective or pathophysiologic immune response to S. neurona infection or the subsequent development of EPM. The objectives of this study were to determine whether S. neurona infected horses with clinical signs of EPM had altered or suppressed immune responses compared to neurologically normal horses and if blood sample storage would influence these findings. Twenty clinically normal horses and 22 horses with EPM, diagnosed by the presence of S. neurona specific antibodies in the serum and/or cerebrospinal (CSF) and clinical signs, were evaluated for differences in the immune cell subsets and function. Our results demonstrated that naturally infected horses had significantly (P<0.05) higher percentages of CD4 T-lymphocytes and neutrophils (PMN) in separated peripheral blood leukocytes than clinically normal horses. Leukocytes from naturally infected EPM horses had significantly lower proliferation responses, as measured by thymidine incorporation, to a non-antigen specific mitogen than did clinically normal horses (P<0.05). Currently, studies are in progress to determine the role of CD4 T cells in disease and protection against S. neurona in horses, as well as to determine the mechanism associated with suppressed in vitro proliferation responses. Finally, overnight storage of blood samples appears to alter T lymphocyte phenotypes and viability among leukocytes.     

Further studies of naturally occurring latent bovine herpesvirus infection

Attempts were made to enhance the isolation rate of latent bovine herpesviruses from trigeminal ganglia by using a fibroblastic fetal bovine kidney cell line, in addition to Madin-Darby bovine kidney cells, and by superinfecting with a temperature-sensitive helper strain of bovine herpesvirus-1 (BHV-1). Four isolates of latent BHV-1 were obtained from 44 pairs of trigeminal ganglia--thus reflecting no increase in isolation rate over that previously observed. Two isolates of a latent bovine herpesvirus-3 strain DN599 were also obtained. Analysis of plaque morphology of BHV-1 isolates obtained in this and a previous study indicated that several biologically heterogeneous strains were capable of establishing latent infections.     

Types of myofibers parasitized in experimentally induced infections with Sarcocystis cruzi and Sarcocystis capracanis

Eighteen calves were orally inoculated with either 200,000 or 225,000 sporocysts of Sarcocystis cruzi. Eight goats were orally inoculated with 20,000 sporocysts of S capracanis. Calves and goats were euthanatized at various times after inoculation, and portions of their right and left biceps femoris, right and left longissimus dorsi, myocardium, and tongue were frozen at -150 C in precooled isopentane and stored at -70 C. Frozen sections of these muscles were stained with hematoxylin and eosin, modified Gomori's trichrome, nonspecific esterase, diphosphopyridine nucleotide tetrazolium reductase, and adenosinetriphosphatase at pH 10.4 and 4.6. Muscle from the same locations was fixed in 10% neutral buffered formalin, processed for paraffin embedding, sectioned, and stained with hematoxylin and eosin. Microscopic examination of both calf and goat tissue indicated that both type I and type II muscle fibers were equally infected and that infected myofibers showed no apparent damage other than displacement by sarcocysts. Occasionally, muscle fibers within the muscle spindles contained sarcocysts.     

Canine viral enteritis. II. Morphologic lesions in naturally occurring parvovirus infection.

The morphologic lesions associated with naturally occurring canine parvovirus infection are described. The disease is characterized by necrosis of crypt epithelium in the small intestine and of lymphoid tissue in Peyers patches, lymph nodes, spleen and thymus.     

Bovine leptospirosis: some clinical features of serovar hardjo infection

During an investigation of natural in utero infection of cattle by Leptospira interrogans strains, infection (almost entirely caused by serovar hardjo) was diagnosed in 57 per cent of 505 calves (472 aborted fetuses, 20 stillborn calves and 13 perinatal deaths) examined over a six-year period. The prevalence of leptospire-infected fetuses showed a seasonal increase in September, October and December and was significantly higher in fetuses aborted by dairy cows than in fetuses aborted by beef cows. The majority of infected fetuses were aborted from the sixth month of gestation onwards. Cows which aborted infected fetuses had not previously exhibited overt signs of agalactia. There was an association between leptospiral infection and retention of fetal membranes.     

Ultrastructural and transmission evidence of Sarcocystis cruzi associated with eosinophilic myositis in cattle.

Skeletal muscle, diaphragm, tongue, esophagus and heart of beef carcasses that were condemned for eosinophilic myositis and those that were unaffected were collected at an abattoir in Colorado and studied to determine the involvement of Sarcocystis spp. All affected carcasses contained similar granulomatous lesions with adjacent infiltrations of leukocytes. Intact or fragments of sarcocysts were found within 32 of 363 granulomas, and whole sarcocysts were present in nearby unaffected muscle cells. Light and electron microscopic examinations revealed that sarcocysts, affected or unaffected by cellular response in condemned carcasses, as well as those found in unaffected carcasses, were consistent with those of S. cruzi. Transmission experiments confirmed that S. cruzi were present in all carcasses, and that dogs, but not cats, were the definitive hosts. The results of pepsin-HCl digestion assays showed that unaffected carcasses that were approved for human consumption generally contained more infective parasites than carcasses that were condemned for eosinophilic myositis. This study provides evidence to support the suggestion that dogs, rather than cats, and unaffected rather than eosinophilic myositis-affected carcasses, have greater potential for contributing to the perpetuation of eosinophilic myositis in the cattle industry.     

Mortality of one-week-old chickens during naturally occurring Marek's disease virus infection

Marek's disease (MD) is a disease of chickens that occurs worldwide and has serious economic consequences. MD can present as one of several forms, with the most commonly occurring forms being the lymphoproliferative diseases. Under experimental conditions, an early mortality syndrome has been recognized following infection by some but not all strains of MD virus (MDV). This is the first report of a confirmed case of mortality due to naturally occurring MDV infection in 1-week-old, nonvaccinated, chickens. Necrotizing lesions were observed in the bursa of Fabricius, lung, duodenum, jejunum, and proventriculus, and large intranuclear inclusion bodies were a striking feature in tissues with lesions in all birds. Immunohistochemical staining for the pp38 protein of MDV revealed abundant pp38 antigen in the affected tissues, confirming the presence of MDV within the lesions. PCR yielded an amplicon with 97% homology to the meq gene of MDV. No evidence of co-infection by either of the immunosuppressive agents chicken anemia virus and infectious bursal disease virus was detected.     

Corneal ulceration associated with naturally occurring canine herpesvirus-1 infection in two adult dogs

CASE DESCRIPTION: An 8-year-old Labrador Retriever with diabetes mellitus in which bilateral phacoemulsification had been performed 3 weeks earlier was evaluated for acute onset of blepharospasm, and a 7-year-old Miniature Schnauzer with chronic immune-mediated thrombocytopenia was reevaluated for keratoconjunctivitis sicca that had been diagnosed 4 weeks earlier. CLINICAL FINDINGS: Dendritic corneal ulcerations were detected in both dogs. Canine herpesvirus-1 (CHV-1) was isolated from corneal swab specimens obtained during the initial evaluation of each dog and during recheck examinations performed until the ulcerations were healed. Canine herpesvirus-1 serum neutralization titers were detected in both dogs. Results of virus isolation from oropharyngeal and genital swab specimens were negative for both dogs. The isolated viruses were identified as CHV-1 via immunofluorescence, transmission electron microscopy, PCR assay, and gene sequencing. Negative controls for PCR assay and virus isolation included conjunctival swab specimens from 50 dogs without extraocular disease and corneal swab specimens from 50 dogs with corneal ulcers, respectively. TREATMENT AND OUTCOME: Lesions resolved in both dogs after topical administration of idoxuridine or trifluridine and discontinuation of topically administered immunosuppressive medications. CLINICAL RELEVANCE: To the authors' knowledge, this is the first report of corneal ulcerations associated with naturally occurring CHV-1 infection and may represent local ocular recrudescence of latent CHV-1 infection. The viruses isolated were identified as CHV-1, and the morphology, antigenicity, and genotype were similar to those for CHV-1 isolates obtained from a puppy that died from systemic CHV-1 infection.     

Pulmonary ultrasonographic abnormalities associated with naturally occurring equine influenza virus infection in standardbred racehorses

The purpose of this investigation was to determine if naturally occurring acute infectious upper respiratory disease (IRD) caused by equine influenza virus is associated with ultrasonographically detectable pleural and pulmonary abnormalities in horses. Standardbred racehorses were evaluated for signs of IRD, defined as acute coughing or mucopurulent nasal discharge. For every horse with IRD (n = 16), 1 or 2 horses with no signs of IRD and the same owner or trainer (n = 30) were included. Thoracic ultrasonography was performed within 5-10 days of the onset of clinical disease in horses with IRD. Horses without IRD were examined at the same time as the horses with IRD with which they were enrolled. The rank of the ultrasound scores of horses with IRD was compared to that of horses without IRD. Equine influenza virus was identified as the primary etiologic agent associated with IRD in this study. Mild lung consolidation and peripheral pulmonary irregularities were found in 11 (69%) of 16 of the horses with IRD and 11 (37%) of 30 of control horses. Lung consolidation (median score = 1) and peripheral irregularities scores (median score = 1) were greater in horses with IRD compared to horses without IRD (median score = 0; P < .05). Pleural effusion was not observed. Equine influenza virus infection can result in abnormalities of the equine lower respiratory tract. Despite the mild nature of IRD observed in this study, lung consolidation and peripheral pulmonary irregularities were more commonly observed in horses with clinical signs of IRD. Further work is needed to determine the clinical significance of these ultrasonographic abnormalities.     

Egg transmission of avian adenovirus-associated virus and CELO virus during a naturally occurring infection.

Both avian adenovirus-associated virus (A-AV) and CELO virus were isolated from the embryonating eggs of 25-week-old black sex-linked hens during a naturally occurring infection. In the first 7 days of egg collection, A-AV was isolated from 10 of 43 (23.2%) embryonating eggs, and CELO virus was isolated from 8 of 43 (18.6%) embryonating eggs. Both viruses were isolated from six eggs. In the next 16 days of egg collection, A-AV and CELO virus were coisolated from 1 of 127 (0.8%) eggs; all other samples were negative for both viruses. All six hens transmitting A-AV to eggs and 5 of 6 hens transmitting CELO virus showed seroconversions (fourfold increase in antibody concentrations). Viruses were not isolated from eggs after the hens showed a fourfold increase in antibody concentrations.     

Molecular epidemiology of Streptococcus zooepidemicus infection in naturally occurring equine respiratory disease

The objective of the study was to characterise the molecular epidemiology of Streptococcus zooepidemicus infection among isolates collected sequentially from recently weaned, pasture maintained Welsh mountain ponies with naturally occurring respiratory disease. Weekly nasopharyngeal and tracheal lavage samplings over a 10-week period were conducted in 29 ponies. Two PCR typing methods based on characterisation of the M-protein hypervariable (HV) region and the 16S-23S rRNA gene intergenic spacer were then applied to isolates of S. zooepidemicus recovered from nasopharyngeal swab and tracheal wash samples. S. zooepidemicus infection was highly prevalent during the study, being isolated from 94% of tracheal washes and 88% of nasopharyngeal swabs. Among 39 different S. zooepidemicus types isolated, more were isolated from the trachea (n=33) than the nasopharynx (n=27). There was evidence from temporal patterns of infection for clonal succession over time by the more prevalent S. zooepidemicus types. Novel S. zooepidemicus types were identified, including previously untyped HV regions and intra-strain multiples of both the HV region and intergenic spacer types.