EQUINE VETERINARY EDUCATION / AE / JULY 2012 357 Original Article Equine mammary gland disease with a focus on botryomycosis: A review and case study E. Smiet*, G. C. M. Grinwis†, J. G. B. van den Top and M. M. Sloet van Oldruitenborgh-Oosterbaan Department of Equine Sciences and †Department of Pathobiology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands Keywords: horse; equine udder; mastitis; botryomycosis; bacterial granulomatous disease; mastectomy; Staphylococcus aureus Summary stained with Gram’s stain – is indicated for the diagnosis of acute inflammation and tentative identification of Mammary gland problems occur incidentally in horses and bacterial organisms prior to culture and antibiotic one of the rarer conditions is botryomycosis (bacterial susceptibility results being available (McCue and Wilson pseudomycosis, bacterial granuloma, staphylococcal 1989). Ultrasonographic examination of the mammary pseudomycetoma). This article includes a short review gland is a useful adjunctive diagnostic modality (Spadari of equine mammary gland problems inappropriate et al. 2008) that provides excellent visualisation of the lactation, mastitis and neoplasia and botryomycosis, and glandular parenchyma and allows efficient, noninvasive additionally 2 clinical cases of botryomycosis of the udder evaluation of mammary enlargement (Brendemuehl 2008). resulting from Staphyloccocus aureus infection will be Cell counts in excess of 100 x 106 cells/l during lactation discussed. Both cases involved nonpregnant, nonlactating and 400 x 106/l during involution are regarded as mares referred for chronic mammary inflammation with pathological (Böhm et al. 2009). draining abcessation. In both mares, botryomycosis In chronic problems, histological examination of a caused by S. aureus was confirmed by histopathology and biopsy of abnormal tissue is required to establish a definitive a bacterial culture. Both mares recovered fully after diagnosis. Fine needle aspiration biopsies are often surgical hemimastectomy under general anaesthesia. unrewarding and thus a wedge biopsy or a hollow needle (Trucut) biopsy is required (Brito et al. 2008; Shank 2009). Introduction Botryomycosis, also called bacterial granuloma or staphylococcal pseudomycetoma, is most commonly In horses, diseases of the mammary glands are uncommon encountered in the scrotal region after castration when compared to dairy cattle and other ruminants (Knottenbelt 2009) or after skin lacerations on the limbs or (McGladdery 1998). Galactorrhoea, mastitis, neoplasia the chin and lip (Knottenbelt 2003, 2009). Occasionally and chronic infections occur occasionally (Knottenbelt botryomycosis occurs in the tissues and skin of the udder 2003; Bader and Busch 2006). Trauma may also be a cause (Weber 2006). for udder enlargement but usually resolves quickly with This article gives a brief review of the literature on the hydrotherapy alone (Knottenbelt 2003). most common equine mammary gland disorders and on Examination of a mare with a unilateral or bilateral botryomycosis in general. Two clinical cases of enlargement of the udder should include a thorough history botryomycosis in the equine mammary gland are and a careful general clinical examination (Brendemuehl described in depth, including diagnosis, treatment and 2008). Thereafter the mammary gland should be observed, outcome. palpated and a sample of the secretion should be Review expressed from the teat (Brendemuehl 2008). Aseptic collection of milk or mammary exudate is necessary for Inappropriate lactation cytological examination and bacterial culture (McCue and Wilson 1989). The microscopic evaluation of a thin smear – Inappropriate lactation, also known as galactorrhoea and *Corresponding author email: [email protected] witch’s milk, occurs rarely and is seldom reported. Although © 2012 EVJ Ltd 358 EQUINE VETERINARY EDUCATION / AE / JULY 2012 several different clinical entities are included in this broad Most often, equine mastitis is caused by Streptococcus term (Knottenbelt 2003), variable mammary swelling with spp. Böhm et al. (2009) and McCue and Wilson (1989) inappropriate lactation is the most common clinical finding reported involvement of coagulase-negative in horses presented at the University Equine Clinic in Utrecht Streptococcus equi ssp. zooepidemicus. Bostedt et al. for investigation of udder problems (van der Kolk 2000). (1988) found that 51% of the cases were associated with Inappropriate lactation may occur in mature mares Streptococcus spp. with 70% of the cases being for several reasons. In pregnant mares it is usually a sign beta-haemolytic Streptococcus spp. In The Netherlands of impending abortion, fetal death, early placental the most common organisms found in equine mastitis are separation or placentitis (Knottenbelt 2003; Bader and Streptococcus and Staphylococcus spp. (van der Burg Busch 2006). In nonpregnant mares inappropriate lactation et al. 2011). Other agents found are Corynebacterium spp. and swelling of the udder may be associated with pituitary and Gram-negative bacteria including Escherichia coli, pars intermedia dysfunction (PPID/Equine Cushing’s Pseudomonas spp. and Klebsiella spp. (Bostedt et al. 1988; disease) (Knottenbelt 2003). If this condition is diagnosed McCue and Wilson 1989; Knottenbelt 2003; Bader and and (temporarily) treated, the udder swelling will often Busch 2006). Anaerobic mammary infections are resolve and lactation will cease (Knottenbelt 2003). uncommon (McGladdery 1998). Sometimes unilateral or bilateral udder swelling with It is important, however, to realise that examination of lactation is present without any clear underlying cause and milk samples of healthy mares during the first 7 days after this is called ‘witch’s milk’. In human medicine, witch’s milk delivery showed that over 40% of the mares and over 20% is fairly common in normal newborn infants and is of the milk samples were bacterially contaminated characterised by breast nodules and lactation up to age 2 (Bostedt et al. 1988). months. The condition is usually attributed to maternal The diagnosis of mastitis should be established using prepartum circulating hormones (Madlon-Kay 1986). A clinical signs and macroscopic examination of any very similar state may occur in newborn foals. abnormal mammary secretion. Cell counts and bacterial In a nonpregnant mature mare, the intake of cultures with antibiotic sensitivity, are especially important phyto-oestrogens may be a cause of the inappropriate for appropriate adjustment of therapy (Knottenbelt 2003; lactation but often no underlying cause is found Bader and Busch 2006). (Knottenbelt 2003). The majority of cases of mammary Therapy consists of frequent hand milking (‘stripping swelling with inappropriate lactation of unknown origin out’), cold water hydrotherapy of the oedematous udder, resolve spontaneously within several weeks to months. nonsteroidal anti-inflammatory drugs and systemic broad-spectrum antibiotics (McCue and Wilson 1989; Mastitis Knottenbelt 2003; Bader and Busch 2006). Trimethoprim-sulphonamide (TMPS) or a combination of The incidence of mastitis in the mare is low compared to penicillin and aminoglycoside are rational choices for initial that in cows (McCue and Wilson 1989; Knottenbelt 2003; antibiotic therapy until the results of bacterial culture are Bader and Busch 2006). However, in breeding mares the known. Antibiotic treatment based on the culture and incidence has been estimated to be as high as 5% in sensitivity results should be continued for at least 5–7 days normal breeding farms and 10% in problem herds (Böhm (McCue and Wilson 1989; McGladdery 1998). et al. 2009). Data from a group of 33 mares with mastitis Since the teats of horses have 2 or even 3 canals, each showed that 27.3% of cases occurred before parturition, of which is associated with separate compartments of 24.2% immediately after delivery, 12.1% during the middle glandular tissue, the use of intramammary antibiotics is and late stages of lactation, 9.1% immediately after controversial. Additionally, many teat injectors are too weaning of the foal and additionally 27.3% of cases large and can cause damage to the teat canal occurred outside the lactation period in nonpregnant (Knottenbelt 2003; van der Burg et al. 2011). In cases of mares (Bostedt et al. 1988). In the majority of cases both mastitis unresponsive to the treatment, neoplastic disease halves of the udder were affected (Bostedt et al. 1988). should be considered as part of the differential diagnosis Clinical signs of mastitis include a painful, swollen, firm (Knottenbelt 2003). and warm udder, with or without purulent discharge (Bader and Busch 2006). Oedema of the mammary gland and the Neoplasia of the mammary glands ventral abdomen is often present (Knottenbelt 2003; van der Burg et al. 2011). The udder may be so painful that The incidence of mammary neoplasia in horses is very low physical examination requires sedation (McGladdery (Hirayama et al. 2003; Knottenbelt 2003; Reesink et al. 1998). Mastitis can be accompanied by signs of systemic 2009). Quite often tumours are not diagnosed at first and disease such as fever, anorexia and even lameness will usually have been treated as mastitis (Reppas et al. (McCue and Wilson 1989). Some cases show no systemic 1996; Brito et al. 2008; Shank 2009). Affected mammary disease in spite of severe localised inflammation glands may be painful on palpation and warm. Often (Knottenbelt 2003). Unilateral atrophy or abcessation may there