T.A. Bryan^1*, D. Hermes², T.A. Hooper¹, C. L. Kanitz³, T.L. Lin³, D.A. Murphy¹,

R.E. Porter³, Jr., D.L. Schrader³, H. L. Thacker³, M.M. Woodruff³

Enteritis in southern Indiana turkeys had been a serious problem in Dubois County. Summer after summer affected flocks were shrill and uneasy, marching the house, refusing feed and water, acting chilled, but managing to impact their gizzards with litter. Dead birds were dehydrated, light in weight, with dark beaks and shanks. Grossly the cecae were distended with pale, syringable fluid. Usually young flocks were affected. The size uniformity in the flock quickly disappeared. It was noted by Dr. Hermes that flocks on crumbles had much lower mortality but similar morbidity than those fed mash. In the fall and winter mortality was not a problem but weight gain and feed conversion were economically unacceptable.

For a number of years, enteric virus detection has depended upon electron microscopy. In our experience, electron microscopy yielded varying results. There was no consistency within a flock. Electron microscopy results improved when naïve, test poults were exposed to field cecal material, followed by harvest of cecal contents after 2-3 days. Poult inoculation definitely improved electron microscopy results.

A literature search of Minnesota's TCE experience suggested an avenue for FA work that Dr. Kanitz had initiated at ADDL-SIPAC for other species. Dr. Y.M. Saif of OSU provided TCE antisera produced in SPF turkeys. Tom Hooper adapted the test procedure for use in several trials with inoculated and uninoculated poults of 5-7 days of age. In the direct immunoflorescence procedure composite sections of fresh frozen intestines taken from the yolk stalk to cecal pouch were stained with conjugated antisera. TCE FA+ diagnosed flocks continued to provide FA+'s for about 4 weeks after the first FA+ result.

For handling large numbers of serological tests, Tom Hooper propagated known antigen into 24 day old turkey embryos, harvested intestines 2 days later, and mounted the frozen intestine sections on glass slides. By testing convalescent sera from 6 poults within a suspect flock, incubating with previously prepared intestinal slides, washing, and staining with conjugated goat anti-turkey globulin, lab time was reduced as well as providing a greater window of opportunity for testing convalescent, suspect flocks.

In conclusion, our experiences suggest that the IFA test for turkey coronavirus has advantages over the EM and FA tests for diagnosing TCE because it produces more consistent results and is less labor intensive.

*Presenter

¹Animal Disease Diagnostic Laboratory, Purdue University, Southern Indiana Purdue Agricultural Center, Dubois, Indiana.

²Perdue Farms, Inc., Washington, IN 47501.

³Animal Disease Diagnostic Laboratory, Purdue University, West Lafayette, IN 47907.

NCCVLD ABSTRACT

Equine Protozoal Myelitis: Current Knowledge About Etiologic Agent Life Cycle, Prevalence, Diagnosis and Treatment

M. Levy^1*

EPM is a debilitating neurologic disease of horses. It can affect the brain, brainstem, spinal cord or any combination of these three areas of the central nervous system. Clinical signs may suggest focal or multifocal disease, which means the disease may affect a very small (focal) part of the central nervous system (CNS) or many parts of the CNS (multifocal). Therefore, the disease may present itself with a variety of different clinical signs, dependent on the location of the damage caused by the organism within the CNS.

Although EPM has been recognized since the 1970's, it was not until 1991 that the organism (protozoan parasite) was cultured from a horse and given the name Sarcocystis neurona. Opossum feces (definitive host) are the source of the infection for horses. Opossums acquire the infection by eating infected birds (intermediate host).

EPM occurs in much of North America. Surveys conducted in central Kentucky, one county in Pennsylvania and the entire states of Ohio and Oregon have revealed that approximately 50% of the horses have been exposed to this parasite. We know that a positive serum test indicates exposure to the parasite not necessarily the presence of disease.

EPM can affect a horse of any age, breed, or sex. The youngest horse reported affected was 2 months of age, and the eldest in its 30's. Clinical signs may be triggered or worsened by physiologic stress or the administration of corticosteroids. In most cases, affected horses are bright and alert with a normal appetite although some horses are dysphagic and may act as if they are choked.

Ante mortem diagnosis of EPM is based on clinical signs and on testing of the horse's cerebrospinal fluid (CSF) by the western blot test. If blood contaminates the CSF sample, a false positive test may result.

Treatment of horses with EPM is expensive. The average range of treatment is 90 to 120 days, and may exceed 6 months in some instances. The current approaches to treatment for EPM includes pyrimethamine in combination with a sulfonamide antimicrobial with or without trimethoprim. It would appear that early detection and therapy increases the chance of successful treatment.

*Presenter

¹Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Purdue University, West Lafayette, IN.

NCCVLD ABSTRACT

Defining Proliferative Enteritis As A Cause of Protein Losing Enteropathy in Foals

C. Fishman^1* and C. Gebhart²

Lawsonia intracellularis (LI) is an obligate intracellular, bacillary bacterium which has been established as the cause of proliferative enteritis (PE) in swine. PE associated with LI infection has been documented as an uncommon to rare disease in the hamster, guinea pig, rabbit, ferret, dog, fox, horse, deer, ostrich and non-human primate. There are currently two published reports describing the pathology of PE in the foal. There are no reports describing the clinical aspects of PE in foals, and reviews of causes of enteritis in foals do not include this disease. PE as the cause of protein losing enteropathy was diagnosed in a six month old, quarterhorse colt presented to the Animal Disease Diagnostic Laboratory at Purdue University, West Lafayette, IN. The animal had been admitted to the Large Animal Teaching Hospital, School of Veterinary Medicine at Purdue University with the clinical history of sudden onset of diarrhea and anorexia. The animal was febrile and dehydrated. Clinical laboratory data revealed hypoproteinemia with comparable decreases in albumin and globulin, mild normocytic, normochromic anemia, mild leukocytosis with neutrophilia, left shift and toxic neutrophils and lymphocytosis with reactive lymphocytes, hyperfibrinogenemia, mild azotemia, hypocalcemia, hypomagnesemia, hyponatremia and metabolic acidosis with compensatory respiratory alkalosis. The animal failed to respond to treatment, which included plasma transfusions, intravenous fluids, corticosteroids, bismuth subsalicylate and cimetidine, and over a three week period became increasingly cachectic, developed subcutaneous, dependent edema and was euthanized. Gross necropsy revealed diffuse thickening of the jejunum and ileum with a variably corrugated or multinodular expansion of the mucosa, submucosal edema and muscular hypertrophy. The affected mucosa was multifocally ulcerated, and in one focus, a transmural ulcer resulted in intestinal perforation and septic peritonitis. The microscopic lesions in the affected small intestine closely resembled that of porcine PE, including villous blunting and deepening of crypts which were tortuous with complex branching patterns. Crypts were lined by crowded, multilayered enterocytes with vesicular nuclei containing prominent nucleoli and a moderate amount of cytoplasm with increased basophilia and a lack of mucus vacuoles. A Warthin-Starry stain revealed myriads of curved bacilli in the apical cytoplasm of the hyperplastic enterocytes. The mitotic index in crypt enterocytes was increased. Crypts were "herniated" into the submucosa, particularly in the area of Peyer's patches. In ulcerated foci, the intestinal wall was partially to fully replaced by granulation tissue. Immunohistochemical stains of paraffin-fixed tissue were positive for LI using a specific monoclonal antibody. The DNA of the bacterium in this case was shown to be homologous to that of swine isolates using extraction, PCR amplification and gel electrophoresis. Transmission electron microscopy revealed bacillary bacteria, measuring 2-4 x 0.2 microns, with a wavy trilaminar cell wall, free within the apical cytoplasm of enterocytes and often adjacent to mitochondria. The clinical signs and response to therapy of this foal were inconsistent with other commonly reported causes of enteritis. If an index of suspicion of PE exists, LI can be detected using PCR on feces and by serum antibody tests. Ante mortem identification of PE cases in foals will allow for estimates of prevalence and will provide epidemiologic information. This is the first case report to correlate clinical and clinical pathologic findings with gross and microscopic morphology in a horse with LI infection.

*Presenter/Graduate Student

¹Animal Disease Diagnostic Laboratory, Purdue University, West Lafayette, IN 47907.

²Department of Veterinary Pathobiology, University of Minnesota, St. Paul, MN 55108.

NCCVLD ABSTRACT

Pneumonic Pasteurellosis Associated with Pasteurella hemolytica Biotype A6 in American Bison (Bison bison)

N.W. Dyer^1* and Alton C.S. Ward²

Three buffalo bulls (Bison bison) with a clinical history of respiratory distress and sudden death were submitted to the North Dakota State University Veterinary Diagnostic Laboratory (NDSU-VDL) for post mortem examination. The owner maintained a herd of forty-eight animals to which he had recently added twenty, sale-purchased, eight month old bull calves. The first calf died on December 25, 1996 followed by a second on December 27. Formalin-fixed and fresh tissues from the second calf reached the NDSU-VDL on December 30. In addition, the carcasses of a calf which developed signs of respiratory disease on December 29, and a calf which died acutely on January 1, 1997, were submitted on January 3. Grossly, lung tissue showed variable amounts of bilateral, cranioventral hemorrhage and consolidation, pleural adhesions, and diffuse fibrinous pleuritis and pericarditis. Histologically, the pleura and interlobular septa were markedly expanded by focally intense clusters of neutrophils, fibrin strands and extravasated red blood cells. A similar inflammatory exudate was diffusely present within alveoli, bronchioles and bronchi. Curvilinear bands of streaming leukocytes frequently outlined these areas of fibrinosuppurative inflammation. Numerous pulmonary vessels showed vasculitis and thrombosis. Fluorescent antibody examination of lung tissue from all three animals was negative for IBR, BVD, BRSV and PI3. Culture of lung tissue from all three animals yielded a moderate to heavy growth of Pasteurella hemolytica biotype A serotype 6.

*Presenter

¹Departments of Veterinary and Microbiological Sciences, North Dakota State University, Fargo, ND.

²Caine Veterinary Teaching and Research Center, University of Idaho, Caldwell, ID.

NCCVLD ABSTRACT

Case Report: Atypical PRRS Outbreak in Illinois Swine Herd

Dale M. Webb^1*

A well-managed, 2,200 sow herd began experiencing illness characterized by inappetence, lethargy, fever, abortion, stillbirths, and sow death in early June, 1996. The average parity in the herd at the time of the outbreak was 3.2. Illness did not correlate with parity nor was it correlated with stage of gestation. Moving or treating sick animals resulted in exacerbation of clinical signs and, in some cases, death of the sow. The herd had prior natural exposure to porcine reproductive and respiratory syndrome (PRRS), and was routinely vaccinated with RespPRRSâ (NOBL Laboratories). Abortions occurred in 8-10% of the affected sows and sows that did not abort had a high occurrence of stillbirths and mummified fetuses. Live-born piglets were often small and weak. Abortions and stillbirths also did not appear to correlate with parity.

Transmission of the disease was slow with neighboring sows becoming ill as long as several weeks apart. Affected animals generally returned to feeding and normal activity within 72 hours of first showing signs of illness. A few sows did not return to normal feeding and activity quickly. These animals were often found not to be pregnant even though they did not appear to cycle. The referring veterinarians² indicated the disease appeared to have affected 95% of the sows in the facility by the end of July (8-9 weeks from the onset of disease in the first animals).

Early in the course of the outbreak, two sows were submitted alive to the Illinois Department of Agriculture Animal Disease Laboratory in Galesburg, IL, for necropsy. The sows were in excellent physical condition and pregnant with near-term fetuses. There were no significant grossly evident findings. No bacterial growth was obtained from aerobic cultures of brain, lung, and pooled liver, kidney, and spleen. Salmonellae were not isolated from culture following enrichment techniques (tetrathionate broth). Both sows were leukopenic and had slightly increased hematocrits and total proteins, suggesting mild dehydration. Fibrinogen was less than 400 mg/dl in both animals, and total protein/fibrinogen ratios were 21 and 27, respectively. No antibody titers were detected to the routinely pathogenic serovars of Leptospira interrogans, except one sow ha a 1:100 titer against the brataslava serovar. One sow was seropositive for exposure to encephalomyocarditis virus at 1:32. One sow had a PRRS ELISA S/P ratio of 0.62; the other sow was seronegative.

Significant histologic alterations were limited to the lung and liver. The lungs had mild diffuse interstitial pneumonia. The liver had randomly distributed, disseminated foci of hepatic necrosis involving small groups of hepatocytes with variable (generally minimal), accompanying inflammatory infiltrates consisting of macrophages, lymphocytes, and neutrophils.

Attempts at virus isolation were unsuccessful at our laboratory (MARC 145 cells, swine testicular cells, and baby hamster kidney cells), the National Veterinary Services Laboratory (NVSL; fetal porcine kidney cells, swine testicular cells, and MARC 145 cells), and Iowa State University (ISU). Subsequent passage of liver homogenate into cesarean-derived , colostrum deprived piglets resulted in all piglets producing PRRS virus antibodies and PRRS virus was isolated from all piglets.³

Based on these findings, this diagnostically challenging case was eventually believed to be an atypical PRRS-virus infection. A novel feature of the disease in this herd was the presence of necrotizing hepatitis, which had not been described previously, but has been seen subsequently in other outbreaks of atypical PRRS. Why this (and other) well-vaccinated herd broke with clinical disease is currently under further investigation at ISU and NVSL.

*Presenter

¹Illinois Department of Agriculture, Animal Disease Laboratory, Galesburg, IL.

²Terry L. Bolton, DVM and James R. Lehman, DVM, Bolton and Lehman, Ltd., Atlanta, IL.

³Thanks to Pat Halbur, Veterinary Diagnostic Laboratory, Iowa State University, and Kelly Lager, National Veterinary Services Laboratory, Ames, IA.