pawing the ground in the afternoon and eve- ning and was found dead the ... parasite that has been cultivated in embryo- nated eggs only and not artificial ...
TYZZER'S DISEASE IN THE FOAL: CASE REPORTS AND REVIEW G. W. THOMSON, R. W. WILSON, E. A. HALL AND P. PHYSICK-SHEARD* Introduction Since its first description as a disease of mice in 1917 (13), Tyzzer's disease has been recognized in a wide range of rodents. More recently, it has been documented in rhesus monkeys (7), cats (5, 6, 10) a dog (9) and also horses (2, 3, 4, 8, 11). The following report appears to be the first description of the disease in horses in Canada. History and Clinical Signs A three week old Arabian foal in a paddock with its dam appeared to be.normal in the early morning in July 1975. Less than one hour later, it was found in lateral recumbency breathing rapidly. Clinical examination revealed pale mucous membranes, rapid heart rate, gasping respiration, blindness and severe depression. The foal died within thirty minutes despite intensive treatment including artificial respiration and corticosteroid therapy. The second case involved a three week old Hunter foal that was noticed depressed and pawing the ground in the afternoon and evening and was found dead the following
FIGURE 1. Focal hepatic necrosis in the Hunter foal with Tyzzer's disease. Note cellular reaction bordering multiple focal areas of necrosis. H & E. x33.
lobules. Within central portions of necrotic areas sinusoids were dilated with red blood cells and few intact hepatocytes remained. Reticuloendothelial cells and few pyknotic cells were prominent in necrotic areas. At the periphery of the lesions were moderate numbers of inflammatory cells, predominantly neutrophils, with moderate numbers of small round cells with dark pyknotic nuclei. Hepatocytes bordering necrotic areas were moderately vacuolated and had light basophilic cytoplasm. Very few portal triads were identifiable in these islands of intact hepatocytes though in some, central veins were present. In H and E stained sections many of these basophilic hepatocytes contained faint basophilic lines crisscrossing the cytoplasm. A Warthin-Starry stain revealed bacilli that were aligned in parallel with haphazard crisscross patterns (Figure 2). Individual organisms were about 8 to 10 microns long, straight to slightly curved bacilli with blunt or rounded ends. No spores were detected. On the basis of the liver lesions and staining characteristics and morphology of the bacilli both cases were diagnosed as Tyzzer's disease.
morning.
Gross Pathology
The Arabian foal was necropsied in the paddock immediately following death. Edema and hemorrhage were present in the right jugular groove and there was a blood clot in the trachea. The myocardium was pale with epicardial hemorrhages. The meninges were congested. The Hunter foal's lungs were congested and edematous. The liver was swollen and had numerous very fine pinpoint pale foci on the surface. The spleen and kidney were enlarged.
Histopathological Findings Lesions were confined to the livers and they were similar in both foals. Virtually all lobules contained large irregular areas of necrosis separated by islands of intact congested hepatic parenchyma (Figure 1). These necrotic foci often were confluent with those of adjacent 'Veterinary Services Laboratory, Ontario Ministry of Agriculture and Food, Box 3612, Guelph,
Discussion
Bacillus piliformis, the causative agent of Tyzzer's disease is a gram-negative sporebearing bacillus. It is an obligate intracellular
Ontario (Thomson and Wilson), R.R. 4, Owen Sound, Ontario (Hall) and R.R. 4, Guelph, On-
tario (Physick-Sheard).
41 CAN. VET. JOUR., vol. 18, no. 2, February, 1977
CANADIAN VETERINARY
JOURNAL
TABLE I
EQUINE TYZZER'S DISEASE Author and Reference Swerczek et al (11) Hall and Van Kruiningen (2) Pulley and Shively (8) Harrington (3) Harrington (4)
Date
Reported
Number of Cases
Breed
(Days)
1973 1974 1974 1975 1976
23 1 1 3 2
Thoroughbred Morgan Quarter 9uarter 'Paint", Arabian
9-31
Age
42 17 21,28,42 21, 24
bacteria, parallel or in crisscross fashion, which were felt to have the morphological charac-
teristics of BaciUus piliformis. Four additional reports (Table I) have all been from the United States. The oldest affected foals have been 42 days of age. As in
o.
the present case, all foals were either found dead or comatose with death ensuing within a few hours, often in spite of intensive therapy. Necropsy findings were mild to severe icterus, hepatic enlargement with or without focal pale areas and enlarged edematous to hemorrhagic abdominal lymph nodes. Diffuse serosal hemorrhage of small intestine and small colon was noted in "some cases" reported by Swerczek et al (11). Focal and diffuse reddening of the mucosal surface of the small intestine was present in two of three
FIGURE 2. Clusters of bacilli in the liver of the Hunter foal with Tyzzer's disease. Note haphazard crisscross arrangements. Warthin-Starry. x390.
parasite that has been cultivated in embryonated eggs only and not artificial media (1). Episodes of diarrhea, debility and high mortality in young animals characterize the disease in all species: enzootics occur in laboratory animals and losses may be extensive (1). Diagnosis of Tyzzer's disease is based upon demonstration of typical organisms in hepatocytes at the periphery of areas of hepatic necrosis. Typical organisms are best demonstrated by silver stains (1). Organisms are pleomorphic 0.5 by 8-10 bacilli which lie in parallel or haphazard crisscross patterns in viable hepatocytes. Some organisms may have bulbar or fusiform swellings and on Giemsa staining may present a beaded or banded appearance in association with alternate light and dark staining zones. With both cases, difficulty was encountered in demonstrating the organisms by Warthin-Starry stains. The modified Warthin-Starry method stained the organisms distinctly (12). A number of reports have appeared on Tyzzer's disease in the horse in the past few years (Table I). In 1973 a series of cases of focal bacterial hepatitis in foals was described from the University of Kentucky (11). Over a period of nine years, 23 foals from four stud farms were affected, 13 of which were diagnosed at necropsy during the 1973 foaling season. Hepatocytes at the periphery of lesions contained gram negative, filamentous, beaded
cases
reported by Harrington (3). Intussuscep-
tion of 30 cm of mid-ileum was found in the Morgan (2). In all cases, final diagnosis was based upon the demonstration of typical or-
ganisms associated with diffuse hepatic necrosis. Nothing is known about the source of infection or pathogenesis of the disease in horses. In one occurrence a pool inhabited by muskrats was present in the paddock in which a foal died and Tyzzer's disease had been diagnosed in muskrats within 15 miles of the farm (2). Nevertheless, spontaneous interspecies transmission has not been documented. Outbreaks of Tyzzer's disease in laboratory rodents are closely linked to stressful manipulations, to environmental buildup of spores, and to altered immune mechanisms in the host (1). The premises on which the Arabian foal died was a boarding stable with a constant turnover of horses. Fifty horses were kept in two barns with paddocks. No ponds were present in paddocks and nothing specific was known about rodent or wildlife populations on the farm. Eight foals were born and raised successfully on the farm during 1975. The Hunter foal was one of about 40 to 50 horses on a premise that boarded and dealt in horses and gave riding instructions. In this case, two possible sources of infection were
,
42
TYZZER S DISEASE
recognized. About 20 rabbits were kept in a separate shed on the property. There had been no disease problems in these rabbits. A large amount of the hay kept for the horses was contaminated with rat feces. Both potential sources are presently under investigation. Although Tyzzer's disease is probably rare, clinicians should consider it as a cause of acute disease and death of foals. Liver and colon should be included in all tissue submissions if Tyzzer's disease is a possibility. Pathologists should consider the modified Warthin-Starry stain in attempts to demonstrate the organism.
2. HALL, W. C. and H. J. VAN KRUININGEN. Tyzzer's disease in a horse. J. Am. vet. med. Ass. 164: 1187-1189. 1974. 3. HARRINGTON, D. D. Naturally-occurring Tyzzer's disease (BaciUus piliformis infection) in horse foals. Vet. Rec. 96: 59-63. 1975. 4. HARRINGTON, D. D. Bacillus piliformis infection (Tyzzer's disease) in two foals. J. Am. vet. med. Ass. 168: 58-60. 1976. 5. KOVATCH, R. M. and G. ZEBARTH. Naturally occurring Tyzzer's disease in a cat. J. Am. vet. med. Ass. 162: 136-138. 1973. 6. KUBOKAWA, K., M. KUBO, Y. TAKASAKI, Y. OGHISo, K. SATO, Y-S LEE, N. GOTO, R. TAKAHASHI and K. FUJIWARA. Two cases of feline Tyzzer's disease. Jap. J. exp. Med. 43: 413-421. 1973. 7. NIVEN, J. S. F. Tyzzer's disease in laboratory animals. Z. Versuchstierk. 10: 168-174. 1968. 8. PULLEY, L. T. and J. N. SHIVELY. Tyzzer's disease in a horse: Light-and electron-microscopic observations. Vet. Path. 11: 203-211. 1974. 9. QURESHI, S. R., W. W. CARLTON and H. J. OLANDER. Tyzzer's disease in a dog. J. Am. vet. med. Ass. 168: 602-604. 1976. 10. SCHNECK, G. Tyzzer's disease in an adult cat. Vet. Med. small Anim. Clin. 70: 155-156. 1975. 11. SWERCZEK, T. W., M. W. CROWE, M. E. PRICKETT and J. T. BRYANS. Focal bacterial hepatitis in foals: preliminary report. Mod. vet. Pract. 54: 66-67. 1973. 12. THOMPSON, S. W. and R. D. HUNT. Selected Histochemical and Histopathological Methods. 2nd Printing. pp. 1048-1049. Springfield, Illinois: Charles C. Thomas. 1966. 13. TYZZER, E. E. A fatal disease of the Japanese Waltzing Mouse called by a sporebearing bacillus (Bacillus piliformis N.sp.). J. med. Res. 37: 307-338. 1917.
Summary Tyzzer's disease was diagnosed in two 21 day old foals that died of acute disease. Diagnosis was based upon demonstration of typical Bacillus piliformis organisms in areas of hepatic necrosis. A modified Warthin-Starry stain was found to be necessary for definitive demonstration of the organism. Five reports of Tyzzer's disease in the foal have been reported from the United States. This appears to be the first report from Canada. Resume Les auteurs ont diagnostique la maladie de Tyzzer chez deux poulains ages de 21 jours et qui avaient succombe a une maladie aigue. Ils baserent leur diagnostic sur la demonstration de Bacillus piliformis, dans des foyers de necrose hepatique. Une modification de la coloration de Warthin-Starry s'avera necessaire pour demontrer le microbe de fagon non equivoque. A cinq reprises, des auteurs Americains ont rapporte des cas de la maladie de Tyzzer, chez le poulain. Les deux cas presents semblent constituer le premier rapport de la maladie, au Canada.
Addendum Since submission of this paper a further case has been brought to our attention by Dr. D. E. Galt, Veterinary Services Laboratory, Brighton, Ontario.
References 1. GANAWAY, J. R., A. M. ALLEN and T. D. MOORE. Tyzzer's disease. Am. J. Path. 64: 717-730. 1971.
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