Jorge L. Colón, DVM THERIOGENOLOGY (MARE)

Transcription

1 Trans-Rectal Ultrasonographic Appearance of Abnormal Combined Utero-Placental Thickness in Late-Term and its Incidence During Routine Survey in a Population of Thoroughbred Mares ( ) Jorge L. Colón, DVM Diagnosis and treatment of placentitis early in the course of the disease process is essential to the success of producing a full-term viable foal. Early diagnosis can be achieved through routine survey of the transrectal combined utero-placental thickness () during late-term gestation of Thoroughbred mares in clinical practice. Author s address: PO Box 11631, Lexington, KY 40576; [email protected] AAEP. 1. Introduction Early detection of placental failure in the mare has been deemed essential for the successful management and treatment of mares affected with placentitis. 1 4 Attempts to treat mares after they have started to show external clinical signs of placental failure are often disappointing. 2 Clinical observations of vaginal discharge and premature udder development often imply that the disease process is past the early stage where it may have been more responsive to treatment. Most cases of placentitis in the mare originate from ascending infections through the cervix; the most common bacterial agents are Streptococcus equi subspecies zooepidemicus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and nocardioform species. 1,5 7 Increased combined utero-placental thickness () and evidence of placental separation with accumulation of hyperechoic fluid are ultrasonographic signs of placentitis. 1,8 11 Early and frequent trans-rectal ultrasonographic examinations of the placenta around the area of the cervical star will increase the clinician s ability to better detect early signs of placental inflammation before external clinical signs can be seen. 2,8,12,13 Several studies have established normal values for trans-rectal measurements of the in the mare in mid and late gestation. 2,14 16 Renaudin et al. 2 and Troedsson et al. 12 suggest that their obtained measurements combined with a 95% confidence interval (CI) may be used as a reference for clinical indication of placentitis and other placental abnormalities. Other studies have also suggested that deviations from these values are associated with placental failure and pending abortion, and suspicion of placentitis by detection of increased can be confirmed by histopathological examination of fetal membranes post-foaling. 12,17 NOTES AAEP PROCEEDINGS Vol

2 Fig. 1. Measurement of the in a normal mare just cranial to the cervico-placental junction in the ventral part of the uterine body dorsal to the middle branch of the uterine artery (cranial is to the left). In a retrospective study, Troedsson and Zent 9 reported a 3.1% rate of placentitis found by abnormal measurement, and 15.8% of the affected mares aborted despite medical treatment. The affected mares that carried to term had a mean gestation of days. Interestingly, the average birth weight of those foals born at term to affected mares was no different from the weight of those born to unaffected mares. Treatment strategies for the management of placentitis have been directed toward combating infection, reducing inflammation, and controlling myometrial activity. 1,3,6,18 21 The pharmacokinetics of trimethoprim-sulfamethoxazole (TMP-SMZ) and pentoxifylline (PTX) in allantoic fluid of pregnant mares has been studied by University of Florida researchers. 22 They have shown good uterine penetration for both drugs and a potential for downregulation of pro-inflammatory cytokines by PTX. 6 Several studies have reported increased success in the management of mares with placentitis when using a combination of TMP-SMZ, PTX, and altrenogest (ALT). 9,12,18,20,21 The data suggests that longterm combination treatment may delay the effects of placental failure in mares with placentitis, which can lead to a positive impact on pregnancy outcome. The anti-prostaglandin effect of progestins has been advocated as a means of reducing prostaglandininduced myometrial activity in the mare. Daels et al. 23 showed that progestin supplementation helped to prevent prostaglandin-induced abortion during the first trimester. Two reports by Bailey et al. 18,20 reported successful reduction of the effects of infection and inflammation in initiating pre-term labor with long-term treatment of placental infections with TMP-SMZ, PTX, and ALT. 18,20 The data showed that 83% of the live foals born to mares medically treated after undergoing experimentally induced placentitis had a negative blood culture at birth. The purpose of this study was to present fieldaccumulated data regarding the abnormal transrectal ultrasonographic combined utero-placental thickness measurement and appearance of early stage cases of placentitis obtained during routine survey of clinically normal Thoroughbred mares in late-term gestation. The goal of the study was to early diagnose potential cases of placentitis and to institute medical treatment in the early stages of disease to reduce or eliminate the incidence of fetal disease or death secondary to placental failure. 2. Materials and Methods Trans-rectal ultrasonographic measurement of the combined utero-placental thickness was performed by a single examiner on 106 Thoroughbred pregnancies at two private farms over three breeding seasons between 2005 and The was obtained just cranial to the placento-cervical junction in the ventral part of the uterine body just dorsal to the middle branch of the uterine artery as previously described (Fig. 1). 2 Measurements were performed at 270, 300, and 330 days gestation as defined by the number of days post-breeding. al length was defined as the number of days between foaling date and last breeding date. For the breeding season, only measurements at 300 and 330 days were obtained. Not all mares Vol. 54 AAEP PROCEEDINGS

3 Fig. 2. Abnormal in two separate cases (A and B) of placentitis with distinguishable demarcation between the chorioallantois and uterus (cranial is to the left). Fig. 3. Abnormal in two separate cases (A and B) of placentitis with pockets of placental separation containing hyperechoic material (cranial is to the left). were available for all measurements or for foaling-date data because of horse movement, sale, or other extraneous circumstances. An analog ultrasound with a 6.0/8.0-mHz linear transducer a was used for the first year of the study and a 7/3 mhz linear transducer b was used for the remainder of the study. If required, a Caslick s procedure was performed on all mares after confirmation of ovulation post-breeding. Abnormal was defined as those measurements that deviated from the 95% CI of previously defined normal values. 2 It was also defined as those that had a two-layer ultrasonographic appearance, which indicates a distinguishable demarcation between the chorioallantois and the uterus (Fig. 2, A and B). Presence of pockets within the layers and/or areas of placental separation were noted (Fig. 3, A and B). Based on treatment data provided by previous research, 18,20 all mares with abnormal were treated with TMP-SMZ c (30 mg/kg, q 12 h, PO), PTX d (8.5 mg/kg, q 24 h, PO), and ALT e (0.088 mg/kg, q 24 h, PO) until foaling. When an abnormal was observed, serial ultrasonographic examinations and measurements were carried out on a weekly to biweekly frequency until foaling. A necropsy was performed at the University of Kentucky Livestock Disease Diagnostic Center on the fetal membranes of mares who had an abnormal during routine survey. Neonatal examinations were performed, and the examiner obtained neonatal bloodwork profiles for all foals born at the farms in the study. Necropsy of fetal membranes, post-foaling uterine culture, and neonatal blood culture were performed on the six abnormal cases that foaled in A local laboratory was used for cultures and bloodwork. Using a personal weight scale, the birth weight of some of the foals and the weight of their corresponding fetal membranes were obtained within the first 12 h of life. AAEP PROCEEDINGS Vol

4 Table 1. Incidence of Normal and Abnormal Measurements at Different Stages of Late-Term During Routine Survey in a Population of Thoroughbred Mares Total Measurements At 270 days At 300 days At 330 days Normal 192 (85%) 60 (92%) 80 (85%) 52 (79%) Abnormal 33 (15%) 5 (8%) 14 (15%) 14 (21%) 3. Results One hundred and six pregnancies were examined on 77 different mares during the survey for measurement of the. Included within the group were 11 mares that were evaluated in two breeding seasons and 9 that were evaluated on all three seasons of the study. Overall, 16 pregnancies (15% [16/106] of total pregnancies) were found to have at least one abnormal measurement at some point during the study. The 16 abnormal pregnancies were carried by 15 mares. One mare was abnormal in two different seasons. Of those 15 mares, 2 were studied over two breeding seasons, and 5 were studied over three breeding seasons. A total of 225 individual measurements were performed during the study. Eighty-five percent of the total measurements (192/225) were considered normal, and 15% (33/225) were considered abnormal (Table 1). Of the 192 normal measurements, 60 were obtained at 270 days gestation with an average of cm, 80 were obtained at 300 days with an average of cm, and 52 were obtained at 330 days with an average of cm. An average gestation of days was obtained from the records of 81 of these cases (Table 2). Of the 33 abnormal measurements, 5 were obtained at 270 days gestation with an average of cm, 14 were obtained at 300 days with an average of cm, and 14 were obtained at 330 days with an average of cm. An average gestation of days was obtained from the records of 15 of these cases (Table 3). Of the 16 cases that were diagnosed with abnormal, 5 had evidence of placental separation with accumulation of hyperechoic fluid. Medical treatment was instituted at the first observation of abnormal. All five cases found with abnormal at 270 days gestation were still abnormally increased at 300 days. Nine of twelve cases abnormal at 300 days had a reduced measurement by day 330; of those, six had returned to normal levels but still had an abnormal ultrasonographic appearance, and they were, therefore, considered abnormal. The distinguishable line of demarcation between the chorioallantois and uterus was observed on all abnormal. Four cases, observed with normal at 270 days, had abnormal at 300 days. One case was normal at 270 and 300 days but abnormal at 330 days. One case was normal at 300 days but abnormal at 330 days. Of the 16 cases placed on medical treatment, 4 were started day 270 and treated for an average of days, 8 were started day 300 and treated for an average of days, and 2 were started day 330 and treated for an average of days (two horses were lost from the study because of sale). Ninety-six foals, including 15 from abnormal cases, were born within the study. All pregnancies in the study were carried to term an average of days. Eighteen foals of the normal cases had an average foal birth weight of lbs (51.9 kg) and an average fetal membranes weight of lbs. (7.1 kg; Table 2). Five foals of the abnormal cases had an average foal birth weight of lbs (51.8 kg) Table 2. Averages of Normal Measurements and Their Corresponding 95% CI and Standard Deviation (SD) During Different Stages of Late-Term, Together With Average and Weights of Foals and Fetal Membranes Born to Unaffected Mares 270 day 300 day 330 day Foal Weight (lb) Fetal Membranes Weight (lb) N Average Median SD % confidence interval Vol. 54 AAEP PROCEEDINGS

5 Table 3. Averages of Abnormal Measurements and Their Corresponding 95% CI and SD During Different Stages of Late-Term, Together With Average and Weights of Foals and Fetal Membranes Born to Affected Mares 270 day 300 day 330 day Foal Weight (lb) Fetal Membranes Weight (lb) N Average Median SD % confidence interval and an average fetal membranes weight of lbs. (7.4 kg; Table 3). Necropsies of fetal membranes of 11 of the mares with abnormal revealed 3 cases where no disease process was identified. Six cases were diagnosed as placental edema, one case was diagnosed as mild multifocal chronic placentitis, and one case was diagnosed as moderate, chronic multifocal suppurative placentitis. Of the six abnormal cases foaled during 2008, four had a negative post-foaling uterine culture with a negative blood culture on the respective foals. Two cases that were treated since day 270 of gestation had a methycillin-resistant Staphyloccocus aureus on the uterine culture; the first case had a Staphyloccocus aureus on the foal s blood culture, and the second case had no growth on the foal s blood culture. Neither one had any pathogenic bacteria isolated from the culture of the placenta at necropsy. 4. Discussion Routine survey of trans-rectal in a population of Thoroughbred mares revealed early ultrasonographic signs of placentitis before external clinical signs were evident. Placental edema was noted in all 16 of the affected cases, and 5 of them had evidence of pockets of separation between the chorioallantois and uterus that contained hyperechoic material. Treatment with TMP-SMZ, PTX, and ALT since the early stages of the disease process seemed to be successful in the maintenance of fullterm pregnancy in all abnormal cases despite the presence of placentitis as confirmed by histopathology of fetal membranes. PTX treatment was performed q 24 h at the beginning of the study period because of the long-term economics of q 12 h treatments. The examiner elected to continue this once a day treatment based on the empirical observations and results obtained. Whether or not the pharmacokinetics of once a day PTX treatment is adequate cannot be corroborated by the present study and would have to be the subject of future experimentation. The successful management of placentitis presented in the study at hand, however, concurs with the referenced reports that affirm that long-term combination treatment with TMP-SMZ, PTX, and ALT delays the effects of placental failure in mares with placentitis, which leads to a positive impact on pregnancy outcome. All abnormal cases carried their pregnancies to term and delivered a live foal. As reported by histopathologic findings, the gross and histologic lesions observed on the fetal membranes examined were most likely a result of a chronic process consistent with the history of placentitis that had, for the most part, resolved because of prolonged medical treatment. The Staphyloccocus aureus organism obtained from the blood culture of one foal was consistent with the microbiologic appearance of what the laboratory considers skin contaminant, and although it could not be eliminated as a causative organism in the case, it was not recovered from either the uterus or placenta. The methycillin-resistant Staphyloccocus aureus cultures obtained from the uterus of two cases were attributed to prolonged antibiotic treatment (63 and 72 days) that led to bacterial resistance. Again, the organism was not recovered from the foal s blood culture or the placenta in either case. Eighty-three percent (5/6) of the cultured foals born to affected mares in the current study presented a true negative blood culture after being treated in utero; the one positive culture was most likely caused by a contaminant. Measurements of normal values in this study were consistent with those previously reported by Renaudin et al. 2 in More importantly, this study presents actual measurement values for abnormal and associated 95% CI and SD for measurements during different stages of late-term gestation. A distinguishable edematous line of demarcation between the chorioallantois and uterus was consistently observed ultrasonographically on those cases of abnormal. This differs from the findings of the 1999 case report by Renaudin et al. 17 where the clinicians were able to distinguish between uterus and chorioallantois in a case of experimentally induced placentitis but not in a naturally occurring case of placentitis defined by abnormal (0.95 cm at 303 days gestation). AAEP PROCEEDINGS Vol

6 The greater percentage of abnormal measurements observed at 300 days gestation occurred for two reasons: all abnormal cases at 270 days were still abnormal at 300 days despite being on treatment, and there were abnormal cases noted at 300 days that were normal at 270 days. Only two cases were originally observed to be abnormal at 330 days gestation after having been normal previously. Those mares that were started on treatment before 300 days gestation showed measured improvement at 330 days; however, the abnormal edematous ultrasonographic appearance persisted until foaling. Medical treatment reduced the measurement in 75% (9 of 12) of the cases by day 330, which includes six (50%; 6 of 12) that had returned to normal values by 330 days gestation. The obtained data for the average abnormal at 330 days was lower than expected (but with a higher SD) because of the positive effects of medical treatment. The two cases that were originally found abnormal at 330 days had measurements of 1.4 cm and 2.2 cm (average cm); in comparison, the other 12 cases that had previously been started on treatment had an average of cm at 330 days. The persistent abnormal ultrasonographic manifestation of placentitis implies that the visual appearance of placental edema is just as important as increased measurement in the early diagnosis of placentitis and that treatment should not be terminated when values return to normal levels in the face of abnormal ultrasonographic appearance. The current study presents three main points that deviate from previously reported findings. 9,12 First, this study showed that 15% of cases examined (16/106) had signs of abnormal (compared with 3.1% reported). This much higher figure points to a higher incidence of disease than that previously observed; this is probably because the whole population of horses was surveyed and not just the ones that might have been deemed at risk. Second, none of the abnormal cases in this study failed to carry a foal to term compared with the 15.8% pregnancy loss previously reported; presumably, this is because of the implementation of treatment earlier in the disease process. Last, foals from abnormal cases were carried longer to an average of days (versus 327 days as reported), which is consistent with full-term gestation of normal mare. The one constant between this study and the reports referenced was that the comparable average birth weight of those foals born to affected mares was no different from the weight of those born to unaffected mares. The data acquired suggest that survey measurements should be started 270 days gestation, treatment should be initiated when placentitis is first diagnosed, and treatment should be continued until foaling occurs. Economic and logistic factors must be studied before deciding to diagnose and treat a potential placentitis for 20% of the gestation period (before day 270). This study also suggests that all mares in a population should be surveyed; the common thought that placentitis mares are at risk for future episodes is not supported by the presented data, because only 1 of 20 mares studied over more than one season was a repeat case of abnormal. This study supports the fact that diagnosis and treatment of placentitis early in the course of the disease process is essential to the success of producing a full-term viable foal. The incidence of placentitis in a field setting seems to be much greater than previously reported. The ultrasonographic appearance of chorioallantoic edema, premature separation of fetal membranes, and accumulation of purulent material between the membranes and uterus can easily and consistently be observed in cases of abnormal. More importantly, this study proves that early diagnosis and medical management of placentitis can be achieved through routine survey during late-term gestation of the trans-rectal of Thoroughbred mares in clinical practice. References and Footnotes 1. Macpherson ML, Troedsson MHT. Diagnosis and treatment of equine placentitis, in Proceedings. 2nd West Coast Equine Reproduction Symposium 2005; Renaudin CD, Troedsson MHT, Gillis CL, et al. Ultrasonographic evaluation of the equine placenta by transrectal and transabdominal approach in the normal pregnant mare. Theriogenology 1997;47: Macpherson ML. Diagnosis and treatment of equine placentitis. Vet Clin North Am [Equine Pract] 2006;22: Vaala W. New perspectives on the late-term mare and newborn foal, in Proceedings. 53rd Annual American Association of Equine Practitioners Convention 2007; Giles RC, Donahue JM, Hong CB, et al. Causes of abortion, stillbirth, and perinatal death in horses: 3,527 cases ( ). J Am Vet Med Assoc 1993;203: Macpherson ML. Treatment strategies for mares with placentitis. Theriogenology 2005;64: Calderwood Mays MB, LeBlanc MM, Paccamonti D. Route of fetal infection in a model of ascending placentitis. Theriogenology 2002;58: Kelleman AA, Luznar SL, Lester GD, et al. Evaluation of transrectal ultrasonographic combined thickness of the uterus and placenta (CTUP) in a model of induced ascending placentitis in late gestation in the pony mare. Theriogenology 2002;58: Troedsson MHT, Zent WW. Clinical ultrasonographic evaluation of the equine placenta as a method to successfully identify and treat mares with placentitis, in Proceedings. Workshop on the Equine Placenta 2004; Reef VB, Vaala WE, Worth LT, et al. Transcutaneous ultrasonographic assessment of fetal well-being during late gestation: a preliminary report on the development of an equine biophysical profile, in Proceedings. 42nd Annual American Association of Equine Practitioners Convention 1996; Reef VB, Vaala WE, Worth LT, et al. Ultrasonographic assessment of fetal well-being during late gestation: development of an equine biophysical profile. Equine Vet J 1996; 28: Troedsson MHT, Renaudin CD, Zent WW, et al. Transrectal ultrasonography of the placenta in normal mares and in mares with pending abortion: a field study, in Proceedings. 43rd Annual American Association of Equine Practitioners Convention 1997; Sheerin PC, Morris S, Kelleman A, et al. Diagnostic efficiency of transrectal ultrasonography and plasma progestin Vol. 54 AAEP PROCEEDINGS

7 profiles in identifying mares at risk of premature delivery, in Proceedings. 49th Annual American Association of Equine Practitioners Convention 2003; Bucca S, Fogarty U, Collins A, et al. Assessment of fetoplacental well-being in the mare from mid-gestation to term: transrectal and transabdominal ultrasonographic features. Theriogenology 2005;64: Renaudin CD, Troedsson MHT, Gillis CL. Transrectal ultrasonographic evaluation of the normal equine placenta. Equine Vet Edu 1999;11: Barnes M, Fite C, Tibary A. Trans-rectal ultrasonographic evaluation of the placenta in Arabian and pony mares in mid-to-late gestation. Theriogenology 2005;64: Renaudin CD, Troedsson MHT, Schrenzel MD. Transrectal ultrasonographic diagnosis of ascending placentitis in the mare: a report of two cases. Equine Vet Edu 1999;11: Bailey CS, Macpherson ML, Graczyk J, et al. Treatment efficacy of trimethoprim sulfamethoxazole, pentoxifylline, and altrenogest in equine placentitis. Theriogenology 2007; 68: Blanchard TL, Varner DD, Schumacher J, et al. Management of the pregnant mare. In: Manual of equine reproduction, 2nd ed. St. Louis: Mosby, 2003; Bailey CS, Macpherson ML, Graczyk J, et al. Treatment efficacy of trimethoprim sulfamethoxazole, pentoxifylline, and altrenogest in equine placentitis, in Proceedings. 53rd Annual American Association of Equine Practitioners Convention 2007; Macpherson ML. Identification and management of the high risk pregnant mare, in Proceeding. 53rd Annual American Association of Equine Practitioners Convention 2007; Rebello S, Macpherson ML, Murchie T, et al. The detection of placental drug transfer in equine allantoic fluid. Theriogenology 2005;64: Daels PF, Besognet B, Hansen B, et al. Effect of progesterone on prostaglandin F-2 alpha secretion and outcome of pregnancy during cloprostenol-induced abortion in mares. Am J Vet Res 1996;57: a Pie Medical 485 Anser with 6.0/8.0-mHz linear transducer, Classic Medical, Mona Rd #105, Tequesta, FL b TeraVet 2000 PC Notebook with 7L3 (7/3-mHz) linear transducer, Classic Medical, Mona Rd #105, Tequesta, FL c SMZ-TMP, Interpharm, Hauppauge, NY d Pentoxifylline Oral Gel, Hagyard, Davidson & McGee Pharmacy, Lexington, KY e Regu-Mate, Intervet, Millsboro, DE AAEP PROCEEDINGS Vol