Mycotic tonsillitis and cervical lymphadenitis in finisher pigs

Maria Spinato, Josepha DeLay, Clint Lichty

Animal Health Laboratory, University of Guelph, ON (Spinato, DeLay); South West Veterinary Services, Stratford, ON (Lichty)

AHL Newsletter 2020;24(1):8-9.                                                                

A farrow-to-finish swine operation of approximately 100-150 sows and 800 grower/finishers developed a problem affecting approximately 10% of animals in the finishing barn. Pigs presented with variably-sized serous-filled cutaneous swellings that were restricted to the cervical region, measuring up to 15 cm in diameter. No bedding was used in the finishing barn, and the feed was mixed on site. One of the affected pigs was euthanatized and samples were collected from internal viscera (no gross abnormalities noted), as well as the cervical cutaneous nodules. These were submitted to the Animal Health Laboratory for histopathologic examination and bacterial culture.

Significant histologic lesions were restricted to the sections of tonsil and cervical cutaneous lesions. Tonsillar architecture was partially effaced and parenchyma expanded by focally extensive accumulations of infiltrating leukocytes that included eosinophils, lymphocytes, neutrophils and numerous multinucleated giant cells that often contained cross-sections of bulbous fungal hyphae (Fig. 1). Sections of the cutaneous nodules were indeterminate regarding site; however, the presence of a distinct capsular boundary was most consistent with lymph node origin. These sections contained extensive foci of necrosis and numerous clusters of karyorrhectic leukocytes. A few scattered multinucleated giant cells containing fungal hyphae were also present. Fungal hyphae were accentuated in a PAS-stained section (Fig. 2). A Ziehl Neelsen-stained section was negative for the presence of acid fast bacteria. A diagnosis of granulomatous tonsillitis and cervical lymphadenitis with intralesional fungal hyphae was made. 

Bacterial culture of the cervical nodules isolated mixed and variable growths of Staphylococcus aureus, E. coli, Streptococcus suis and S. dysgalactiae subsp. equisimilis. Since numerous fungal hyphae were seen on routine wet mount of the affected tissues, mycotic cultures were also set up. Geotrichum spp. was isolated from 3 out of 3 samples; Mucor spp. was also isolated from 1 of the 3 tissues. A search of the veterinary literature revealed a single case report of mycotic tonsillitis in a free-ranging weaner pig from Australia due to Geotrichum candidum . Geotrichum spp. is a saprophytic fungus found on fruits, vegetables, and dairy products. The authors of this report speculated that the feeding of macadamia nut trash may have inoculated the tonsils of this pig with this uncommon organism. Sporadic cases of geotrichosis in other species, including humans, are often linked to immunosuppression.

Additional history was obtained from the herd veterinarian in this case. The presumed source of infection was poor quality, moldy ensiled high moisture corn. Tonsillar inoculation by fungi following oral exposure with subsequent dissemination to cervical lymph nodes was the probable mechanism for development of the cervical cutaneous nodules.  AHL

Reference

1. Lee, EJ et al. Tonsillitis in a weaner pig associated with Geotrichum candidum. J Vet Diagn Invest 2011;23:175-177.