Actinomyces hyovaginalis infections

M G COLLETT

GENERAL INTRODUCTION: IRREGULAR, NON-SPORING, GRAM-POSITIVE RODS

Introduction

Actinomyces-like bacteria isolated from purulent vaginal discharges, tissues from aborted foetuses, pyogranulomatous or necrogranulomatous lesions of the mammary glands and granulomas in the viscera of pigs differ from other Actinomyces spp.⁶ Although the cause of porcine actinomycosis had long been thought to be A. bovis, isolates from pigs have certain consistent differences.¹² Franke proposed the name Actinomyces suis.^{2, 3} This name was, however, non-official8 but it was used until the confusion surrounding the renaming of Eubacterium suis as Actinomyces suis (now Actinobaculum suis) was resolved by Collins, Stubbs, Hommez and Devriese (1993), who used comparative 16S rRNA gene sequence analysis and designated the organism as the new species, Actinomyces hyovaginalis.¹

Actinomyces hyovaginalis has been isolated from an aborted piglet in South Africa.⁵

Aetiology

The organisms are predominantly diphtheroidal and rods are arranged in clusters or V or Y forms; coccoid elements may occur. After anaerobic incubation, colonies are flat with outrunning edges. They are not haemolytic and are catalase negative. The natural habitat is the genital tract of pigs.^{1, 6} In routine diagnostic bacteriology, however, these bacteria may be incorrectly identified (based on slow growth and cell morphology after Gram’s staining) after one or two days’ incubation as Trueperella (Actinomyces) pyogenes.⁶ For more detail on the biochemical characteristics and distinguishing features, the reader is referred to Collins et al.¹

Clinical signs and pathology

Actinomycosis in pigs is characterized by a necrogranulomatous mastitis suspected of being initiated by trauma from the sharp teeth of suckling piglets.¹¹ Affected udders may have a large swelling, which may hang as far as the ground and which contains abscesses and draining sinuses. Actinomycotic mastitis in pigs should be differentiated from spirochaetal granulomas affecting the udder as well as from lesions caused by infections with Actinobacillus lignieresii, Staphylococcus spp. (botryomycosis) and Trueperella (Actinomyces) pyogenes.^{7, 9, 10} Affected sows should be culled.¹⁰ Prevention involves the clipping of the teeth of piglets shortly after birth.

The organism has been isolated following anaerobic culture of the stomach contents of aborted piglets. Affected foetuses had mild anasarca, ascites, hydrothorax with fibrin in the pleural fluid and a severe, diffuse pyogranulomatous bronchopneumonia.¹³

Actinomycotic granulomas have also been found in the lungs, spleen and kidneys of slaughter pigs.^{4, 12}

References

1. COLLINS, M.D., STUBBS, S., HOMMEZ, J. & DEVRIESE, L.A., 1993. Molecular taxonomic studies of Actinomyces-like bacteria isolated from purulent lesions in pigs and description of Actinomyces hyovaginalis sp. nov. International Journal of Systematic Bacteriology, 43, 471–473.
2. FRANKE, F., 1973A. Untersuchungen zur Ätiologie der Gesäugeaktinomykose des Schweines. Zentralbladt für Bakteriologie, Parasitenkunde, Infektionskrankheiten und Hygiene, 1 Abteilung Original A223, 111–124.
3. FRANKE, F., 1973B. Die mikrobiologische Diagnostik der Gesäugeaktinomykose des Schweines. Berliner und Münchener Tierärztliche Wochenschrift, <86, 428–432.
4. HAGA, M., OMURA, Y. & SUGANO, S., 1951. Pulmonary actinomycosis in cattle and swine. Japanese Journal of Veterinary Science, 13, 102–103.
5. HENTON, M.M., 1999. Onderstepoort Veterinary Institute, Onderstepoort. Unpublished data.
6. HOMMEZ, J., DEVRIESE, L.A., MIRY, C. & CASTRYCK, F., 1991. Characterization of 2 groups of Actinomyces-like bacteria isolated from purulent lesions in pigs. Journal of Veterinary Medicine Series B, 38, 575–580.
7. RADOSTITS, O.M., BLOOD, D.C. & GAY, C.C., 1994. Veterinary Medicine. 8th edn. London, Philadelphia: Baillière Tindall.
8. SCHAAL, K.P., 1986. Genus Actinomyces. In: sneath, p.h.a., mair, n.s., sharpe, m.e. & holt, j.g., (eds). Bergey’s Manual of Sytematic Bacteriology, Vol II. Baltimore, London: Williams and Wilkens.
9. SIMS, L.D., 1996. Mammary Glands. In: sims, l.d. & glastonbury, j.r.w., (eds). Pathology of the Pig—a Diagnostic Guide. The Pig Research and Development Corporation and Agriculture Victoria.
10. TAYLOR, D.J., 1995. Pig Diseases. 6th edn. Published by the author, 31 North Birbiston Rd, Lennoxtown, Glasgow, G65 7LZ, UK.
11. TIMONEY, J.F., GILLESPIE, J.H., SCOTT, F.W. & BARLOUGH, J.E., 1988. Hagan and Bruner’s Microbiology and Infectious Diseases of Domestic Animals. 8th edn. Ithaca and London: Comstock Publishing Associates.
12. VAWTER, L.R., 1946. Pulmonary actinomycosis in swine. Journal of the American Veterinary Medical Association, 109, 198–203.
13. YAMINI, B. & SLOCOMBE, R.F., 1988. Porcine abortion caused by Actinomyces suis. Veterinary Pathology, 25, 323–324.