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Simple Summary Equine sarcoids, caused by bovine papillomaviruses, are equine skin tumors of fibroblastic origin. It is well known that bovine papillomaviruses are able to interfere with the survival and proliferation of cells by regulating autophagy, a mechanism implicated in the breakdown and reuse of old and damaged cellular material. The present study focused on the evaluation in equine sarcoids and normal skins of the expression level of some of the main proteins involved in the autophagic pathway, such as Beclin 1, LC3 and P62, by immunohistochemical and biochemical techniques. Results obtained in equine sarcoids suggested an alteration of the autophagic process which could lead to a predominance of a particular population of fibroblast. Those fibroblasts could survive longer in a hypoxic microenvironment and produce more and/or altered collagen, giving an origin to the equine sarcoid. Abstract Background: It is well known that δ-bovine papillomaviruses (BPV-1, BPV-2 and BPV-13) are one of the major causative agents of equine sarcoids, the most common equine skin tumors. Different viruses, including papillomaviruses, evolved ingenious strategies to modulate autophagy, a complex process involved in degradation and recycling of old and damaged material. Methods: The aim of this study was to evaluate, by immunohistochemistry (IHC) and Western blot (WB) analysis, the expression of the main related autophagy proteins (Beclin 1, protein light chain 3 (LC3) and P62), in 35 BPV1/2 positive equine sarcoids and 5 BPV negative normal skin samples. Results: Sarcoid samples showed from strong-to-moderate cytoplasmic immunostaining, respectively, for Beclin 1 and P62 in >60% of neoplastic fibroblasts, while LC3 immunostaining was weak to moderate in ≤60% of neoplastic fibroblasts. Western blot analysis confirmed the specificity of the antibodies and revealed no activation of autophagic flux despite Beclin 1 overexpression in sarcoid samples. Conclusion: Results could suggest the activation of the initial phase of autophagy in equine sarcoids, and its impairment during the following steps. The impairment of autophagy could lead to a selection of a quiescent population of fibroblasts, which survive longer in a hypoxic microenvironment and produced more and/or altered collagen.

Although bovine papillomavirus (BPV)-induced equine sarcoids are often identified solely by clinical examina-tion, confirmation of the clinical diagnosis is essential for correct treatment selection. Only few approaches are presently available for this purpose. PCR-based screening for BPV in superficial swabs is widely-used to support clinical suspicion. While this method effectively detects sarcoid involvement in ulcerated lesions, sensitivity is lower in tumors with intact epithelium. This cross-sectional study compared the diagnostic characteristics of superficial swabs and fine-needle aspirates (FNA) with the aim to validate FNA as an alternative sampling method to detect BPV in suspect lesions. Among 63 lesions confirmed as sarcoids from 58 horses, compared to swabs FNA detected a greater proportion of BPV positives in general (swab, 70 %,;95 % confidence intervals [CI], 58.5 %-81.2 %; FNA, 98 %, 95 % CI, 95.3 %-100 %; P = 0.0001) and among a non-ulcerated subgroup (swab, 63 %, 95 % CI, 50.4 %-76.6 %; FNA, 98 %, 95 % CI, 91.4 %-100 %; P = 0.0001). Furthermore, the sensitivity, as well as the negative predictive value and accuracy of FNA for matched samples from 58 horses were superior to surface swabbing for the group of all horses and the subgroup that included only lesions with an intact epidermis (n = 48), with differences ranging from 23 % (95 % CI, 11.4 %-34.6 %) to 52 % (95 % CI, 25.9 %-78.1 %). Other advantages of FNA identified were a higher chance of adequate sampling and a reduced risk of unwanted detection of superficial contamination or latent BPV in keratinocytes. The ability to consistently detect BPV in all clinical lesion types indicates that FNA shows promise as a valid diagnostic tool to improve the consistency and quality of the diagnostic workup of equine sarcoids.

Simple Summary Equine sarcoids are common cancers of horses that are caused by bovine papillomaviruses (BPVs). Previous studies have suggested that most sarcoids are caused by either BPV1 or BPV2, with the proportion caused by each BPV type dependent on the country in which the horse lived. Additionally, some studies also suggest that other papillomavirus (PV) types could cause equine sarcoids. The study was comprised of 104 sarcoids from New Zealand horses and used both specific and consensus PCR primer sets. Overall, PV DNA was amplified from 90% of the sarcoids. Of the ones that contained BPV DNA, 88% contained only BPV2 DNA, 10% BPV1 and BPV2 DNA, and 2% only BPV1 DNA. Only the primers specific for BPV1 or specific for BPV2 amplified DNA and no other PV types were detected. There was little variability in the rates of detection between different regions of New Zealand and rates were consistent when two distinct time periods were compared. These results suggest that sarcoids from New Zealand horses are consistently most often caused by BPV2 and thus if vaccination is used to prevent these cancers, it will be important to use a vaccine that provides good protection against this BPV type. Abstract Equine sarcoids are common mesenchymal neoplasms of horses that are caused by cross-species infection by deltapapillomaviruses. While bovine papillomavirus (BPV) 1 and 2 are the most common causes, there are differences between countries regarding which of these BPV types cause the majority of sarcoids. Additionally, no causative PV can be detected in a subset of sarcoids, suggesting that other PV types could be rarer causes of these neoplasms. In the present study, consensus PCR primers and PCR primers specific for the five deltapapillomavirus types currently known to cause mesenchymal neoplasia (BPV1, BPV2, BPV13, BPV14, and Ovis aries PV2 DNA) were used to investigate the presence of PV DNA in 104 sarcoids from three defined regions in New Zealand and from two distinct time periods separated by 15 years. PV DNA was detected in 94 (90.4%) sarcoids. Of the sarcoids containing PV DNA, 83 (88.3%) contained only BPV2 DNA, 9 (9.6%) BPV1 and BPV2 DNA, and 2 (2.1%) only BPV1 DNA. No other PV types were detected. The predominance of BPV2 is consistent with studies of sarcoids from North America but dissimilar to studies of sarcoids from Europe and Australia. Detection rates of BPV1 and BPV2 were similar in sarcoids from different regions of New Zealand and in sarcoids from different time periods. These results suggest that most equine sarcoids in New Zealand are caused by BPV2 and thus if vaccines are developed to prevent sarcoids, vaccines that provide good protection against BPV2 will be required in this country.

Sarcoids are the most common cutaneous tumor of equids and are caused by bovine papillomavirus (BPV). Different clinical subtypes of sarcoids are well characterized clinically but not histologically, and it is not known whether viral activity influences the clinical or histological appearance of the tumors. The aim of this study was to verify whether the development of different clinical types of sarcoids or the presence of certain histological features were associated with BPV distribution within the tumor. The presence of BPV was assessed by polymerase chain reaction (PCR) and visualized in histological sections by chromogenic in situ hybridization (CISH) in 74 equine sarcoids. Furthermore, to better characterize the molecular features of neoplastic cells, immunohistochemistry for S100, smooth muscle actin-α (αSMA), and fibroblast-associated protein-α (FAPα) was performed. The presence of BPV was confirmed in all tissues examined by either or both PCR and CISH (72/74, 97% each). Of 70/74 CISH-positive cases, signal distribution appeared as either diffuse (61/70, 87%) or subepithelial (9/70, 13%); the latter was more frequently observed in the verrucous subtype. However, no statistically significant association was found between clinical subtypes and specific histological features or hybridization pattern. Moreover, CISH signal for BPV was not detected in the epidermis overlying sarcoids nor in the tissue surrounding the neoplasms. By immunohistochemistry, αSMA confirmed the myofibroblastic differentiation of neoplastic cells in 28/74 (38%) sarcoids. Using tissue microarrays, FAPα labelling was observed in neoplastic fibroblasts of all sarcoids, suggesting this marker as a potential candidate for the immunohistochemical diagnosis of sarcoids.

Equine clinicians and researchers often make the diagnosis of equine sarcoids (ES) on clinical assessment alone, without histopathological confirmation. However, the accuracy of the clinical diagnosis of ES has not been critically assessed. To assess sensitivity, specificity, positive and negative predictive values of the clinical diagnosis of ES, 40 clinical cases with histologically confirmed equine skin lesions (26 ES and 14 non-ES) were compiled in a representative online examination. For each case and lesion, at least one photograph and all relevant information were presented in a standardised format. This included the horse's signalment, lesion localisation, lesion progression, presence of other skin lesions, earlier treatments and response to treatment. No information relevant for the assessment of the lesion was intentionally withheld. Fourteen ES experts, 39 board-certified equine specialists, 103 equine practitioners and 25 novices categorised the cases into ES or non-ES and graded their level of diagnostic confidence on a scale from 1 to 6 for each case. The overall success rate was 82.0% while sensitivity and specificity were 83.3% and 79.6%, respectively. The positive and negative predictive values were 88.4% and 72.0%, respectively, in the tested population with a 66% prevalence of ES. However, less experienced veterinarians were frequently wrong in their clinical judgement despite a high level of diagnostic confidence. Therefore, the authors propose to develop a diagnostic tool to help clinicians optimise their selection of lesions requiring a biopsy. Ultimately, this will help reduce costs and morbidity generated by unnecessary diagnostic and therapeutic efforts.

Equine sarcoid is the most common skin tumor of horses. Clinically, it occurs as a locally invasive, fibroblastic, wart-like lesion of equine skin, which has 6 clinical classes: occult, verrucose, nodular, fibroblastic, mixed, and malignant. Sarcoids may be single but multiple lesions are more frequent. The typical histological feature is increased density of dermal fibroblasts which form interlacing bundles and whorls within the dermis. Lesions are mostly persistent, resist therapy, and tend to recur following treatment. In general, sarcoids are not fatal but their location, size, and progression to the more aggressive form may lead to the withdrawal of a horse from use and serious infringement of their welfare leading to the loss of valuable animals. Bovine papillomavirus (BPV) type 1 and less commonly type 2 contribute to the development of equine sarcoid. The viral genome and proteins are detected in a high percentage of cases. Furthermore, viral oncoprotein activity leads to changes in the fibroblastic tissue similar to changes seen in other types of tumors. Equine sarcoids are characterized by a loss of tumor suppressor activity and changes allowing abnormal formation of the affected tissue, as well as y immune defense abnormalities that weaken the host’s immune response. This impaired immune response to BPV infection appears to be crucial for the development of lesions that do not spontaneously regress, as occurs in BPV-infected cows.

Interleukin (IL)-2 stimulates antitumour immunity and is successfully used for the treatment of different neoplasias.Canarypox virus locally expressing feline IL-2 is safe and can be used to treat equine sarcoids.Twenty horses of different breeds with a median age of eight years (interquartile range 6.0-13.3 years) and a total number of 59 sarcoids were included in the study.In this prospective clinical trial, sarcoids were injected twice seven days apart, with a recombinant canarypox virus expressing feline IL-2. Complete blood counts (CBC) and fibrinogen levels were measured before treatment and on days 1, 2, 7 and 8.Complete regression was achieved in eight horses (40%) and partial regression in two horses (10%). No change in sarcoid size was observed in two horses (10%) and the disease progressed in five horses (25%). Sarcoids of three horses (15%) showed initial response followed by tumour growth. There were no significant changes in CBC and fibrinogen levels after either injection. One horse developed a mild fever the day after each injection, which subsided without treatment the following day.Treatment of equine sarcoids with recombinant canarypox virus expressing feline IL-2 seems to be a safe therapy option. Although the expression of IL-2 after vector injection and its biological activity in horses were not proven in this study, the treatment resulted in regression and partial regression in 50% of the cases. Further studies are necessary to verify these findings and to establish a treatment protocol.L’interleukine (IL)-2 stimule l’immunité anti-tumorale et est efficacement utilisée pour le traitement de différentes néoplasies. HYPOTHÈSES/OBJECTIFS: Canarypoxvirus exprimant localement IL-2 félin est sûr et peut être utilisé pour traiter les sarcoïdes équins.Vingt chevaux de différentes races avec un âge médian de huit ans (écart interquartille de 6.0-13.3 ans) et un nombre total de 59 sarcoïdes ont été inclus dans l’étude. MÉTHODES: Dans cette étude clinique prospective, les sarcoïdes ont été injectés deux fois à sept jours d’intervalle avec un canarypoxvirus recombinant exprimant IL-2 félin. Une formule sanguine (CBC) et les taux de fibrinogènes ont été mesurés avant traitement et à jours 1, 3, 7 et 8. RÉSULTATS: Une régression complète a été obtenue pour huit chevaux (40%) et une régression partielle pour deux chevaux (10%). Aucun changement de taille des sarcoïdes n’a été observé pour deux chevaux (10%) et la maladie s’est aggravée pour cinq chevaux (25%). Les sarcoïdes de trois chevaux (15%) ont montré une réponse initiale puis une croissance de la tumeur. Il n’y avait pas de changement significatif dans le CBC et les taux de fibrinogènes après chacune des injections. Un cheval a développé une fièvre modérée le jour après chaque injection, qui disparaissait sans traitement le jour suivant.Le traitement des sarcoïdes équins avec canarypoxvirus exprimant IL-2 félin semble être une option thérapeutique sure. Bien que l’expression d’IL-2 après injection du vecteur et son activité biologique chez les chevaux n’aient pas été prouvées dans cette étude, le traitement résultaient en une régression et une régression partielle dans 50% des cas. D’autres études sont nécessaires pour vérifier ces données et pour établir un protocole thérapeutique.INTRODUCCIÓN: la interleuquina 2 (IL-2) estimula la inmunidad antitumoral y se utiliza con éxito para el tratamiento de diferentes neoplasias. HIPÓTESIS/OBJETIVOS: El poxvirus de canarios que expresa localmente IL-2 felina es seguro y puede usarse para tratar sarcoides equinos. ANIMALES: se incluyeron en el estudio veinte caballos de diferentes razas con una mediana de edad de ocho años (rango intercuartílico 6,0-13,3 años) y un total de 59 sarcoides. MÉTODOS: en este ensayo clínico prospectivo, se inyectaron sarcoides dos veces con siete días de diferencia, con un poxvirus de canarios recombinante que expresaba IL-2 felina. Se midieron los recuentos sanguíneos completos (CBC) y los niveles de fibrinógeno antes del tratamiento y en los días 1, 2, 7 y 8. RESULTADOS: se logró una regresión completa en ocho caballos (40%) y una regresión parcial en dos caballos (10%). No se observó ningún cambio en el tamaño del sarcoide en dos caballos (10%) y la enfermedad progresó en cinco caballos (25%). Los sarcoides de tres caballos (15%) mostraron una respuesta inicial seguida de crecimiento tumoral. No hubo cambios significativos en los niveles de CBC y fibrinógeno después de cualquiera de las inyecciones. Un caballo desarrolló una fiebre leve al día siguiente de cada inyección, que remitió sin tratamiento al día siguiente. CONCLUSIONES: El tratamiento de los sarcoides equinos con el poxvirus de canarios recombinante que expresa IL-2 felina parece ser una opción terapéutica segura. Aunque la expresión de IL-2 después de la inyección del vector y su actividad biológica en caballos no se probaron en este estudio, el tratamiento resultó en regresión y regresión parcial en el 50% de los casos. Se necesitan más estudios para verificar estos hallazgos y establecer un protocolo de tratamiento.Interleukin (IL)-2 stimuliert die Antitumor Immunität und wird erfolgreich zur Behandlung verschiedener Neoplasien eingesetzt.Das Kanarienpoxvirus, welches lokal felines IL-2 exprimiert ist sicher und kann verwendet werden, um equine Sarkoide zu behandeln.Es wurden zwanzig Pferde verschiedener Rassen mit einem medianen Alter von acht Jahren (Interquartilsabstand 6,0-13,3 Jahre) und insgesamt 59 Sarkoide in die Studie aufgenommen.Eine völlige Remission wurde bei acht Pferden (40%) erzielt und eine partiale Remission bei zwei Pferden (10%). Es konnte bei zwei Pferden keine Veränderung der Sarkoidgröße beobachtet werden (10%) und bei fünf Pferden verlief die Erkrankung progressiv (25%). Die Sarkoide von drei Pferden (15%) zeigten anfangs eine Verbesserung, gefolgt von vermehrtem Tumorwachstum. Es gab nach der jeweiligen Injektion keine signifikanten Veränderungen bei Blutbild und Fibrinogenwerten. Ein Pferd hatte am Tag nach jeder Injektion ein mildes Fieber, welches ohne Behandlung am darauffolgenden Tag wieder verschwand.Eine Behandlung equiner Sarkoide mit rekombinantem Poxvirus, welches felines IL-2 exprimiert, scheint eine sichere Therapieoption darzustellen. Obwohl die Exprimierung von IL-2 nach einer Vektorinjektion und seine biologische Aktivität bei Pferden in dieser Studie nicht bestätigt werden konnten, resultierte die Behandlung ini 50% der Fälle in einer völligen bzw partialen Regression. Es sind weitere Studien nötig, um diese Befunde zu verifizieren und um ein Behandlungsprotokoll zu erstellen.背景: インターロイキン (IL)-2 は抗腫瘍免疫を刺激し、さまざまな腫瘍の治療に使用されている。 仮説/目的: ネコIL-2を局所的に発現するカナリアポックスウイルスは安全で、馬のサルコイドの治療に使用することができる。 被験動物: 年齢中央値が8歳 (中間値範囲6.0~13.3歳) の異なる品種の馬20頭、合計59のサルコイドを研究に含めた。 方法: 本前向き臨床試験では、サルコイドにネコIL-2を発現する組換えカナリアポックスウイルスを7日間隔で2回注射した。全血球計算(CBC)およびフィブリノーゲン値を治療前、治療後1、2、7、8日目に測定した。 結果: 8頭 (40%) の馬で完全退行が、2頭 (10%) で部分退行を達成した。サルコイドのサイズの変化は2頭 (10%) に認められず、5頭 (25%) で病状が進行した。3頭の馬 (15%) のサルコイドは初期反応を示し、その後腫瘍の増殖が認められた。いずれの注射を行ってもCBCおよびフィブリノゲン値に有意な変化はなかった。1頭の馬は各注射の翌日に軽度の発熱を示したが、翌日には治療せずに治まった。 結論: ネコIL-2を発現する組換えカナリアポックスウイルスを用いた馬のサルコイド治療は、安全な治療オプションの一つであると思われる。本研究では、ベクター注入後のIL-2の発現および馬における生物学的活性は証明されなかったが、治療により50%の症例で退行および部分的な退行が得られた。これらの知見を検証し、治療プロトコールを確立するためには、さらなる研究が必要である。.背景: 白细胞介素(IL)-2刺激抗肿瘤免疫, 并成功用于治疗不同的肿瘤。 假设/目的: 局部表达猫IL-2的金丝雀痘病毒是安全的, 可用于治疗马结节病。 动物: 研究纳入了20匹不同品种的马, 中位年龄为8岁 (四分位距6.0-13.3岁) , 共59种结节病。 方法: 在这项前瞻性临床试验中, 结节病每隔七天注射两次, 用表达猫IL-2的重组金丝雀痘病毒。在治疗前和第1、2、7和8天检测血常规 (CBC)和纤维蛋白原水平。 结果: 8匹马(40%)达到完全缓解,2匹马(10%)达到部分缓解。2匹马(10%)未观察到结节病大小变化, 5匹马(25%)疾病有所发展。3匹马(15%)的结节病显示初始缓解, 随后肿瘤生长。两次注射后,CBC和纤维蛋白原水平均无显著变化。1匹马在每次注射后第二天出现轻度发热, 第二天未经治疗退烧。 结论: 用表达猫IL-2的重组金丝雀痘病毒治疗马结节病,似乎是一种安全的治疗选择。尽管本研究未证实载体注射后IL-2的表达及其在马体内的生物活性, 但该治疗使得50%的病例缓解和部分缓解。有必要进行进一步研究,以验证这些结果并确立治疗方案。.A interleucina (IL)-2 estimula a imunidade antitumoral e é utilizada com sucesso no tratamento de diferentes neoplasias. HIPÓTESE/OBJETIVOS: O vírus canarypox que expressa IL-2 felina localmente é seguro e pode ser usado para tratar sarcóides equinos.Vinte cavalos de raças diferentes com idade mediana de oito anos (intervalo interquartil 6,0-13,3 anos) e um número total de 59 sarcoides foram incluídos no estudo. MÉTODOS: Neste ensaio clínico prospectivo, o vírus canarypox recombinante expressando IL-2 felina foi injetado nos sarcoides duas vezes em um intervalo de sete dias. Hemogramas completos (HM) e níveis de fibrinogênio foram mensurados antes do tratamento e nos dias 1, 2, 7 e 8.Regressão completa foi obtida em oito cavalos (40%) e regressão parcial em dois cavalos (10%). Nenhuma mudança no tamanho do sarcóide foi observada em dois cavalos (10%) e a doença progrediu em cinco cavalos (25%). Os sarcoides de três cavalos (15%) apresentaram boa resposta inicial seguida de crescimento do tumor. Não houve alterações significativas no hemograma e nos níveis de fibrinogênio após qualquer injeção. Um cavalo apresentou febre moderada no dia seguinte de cada injeção, que cedeu sem tratamento em um dia. CONCLUSÕES: O tratamento de sarcóides equinos com vírus canarypox recombinante que expressa IL-2 felina parece ser uma opção de terapia segura. Embora a expressão de IL-2 após a injeção do vetor e sua atividade biológica em equinos não tenham sido comprovadas neste estudo, o tratamento resultou em regressão e regressão parcial em 50% dos casos. Mais estudos são necessários para verificar esses achados e se estabelecer um protocolo de tratamento.

Background Bovine papillomavirus types 1 and 2 (BPV1/2) infection in horses has been associated with the development of equine sarcoids. Previous findings revealed the presence of sarcoid-associated BPV sequence variants that have been proposed as a key factor of cross-species infection in horses. To verify this hypothesis, sarcoid-associated BPV variants should be identified regardless of geographic location. Objectives Sequence analyses of BPV1/2 derived from both horses and cattle were conducted to clarify the sarcoid-associated sequence variants. The aim of this study was to clarify the correlation between BPV phylogeny and the geographic origin/host species. Study design Cross-sectional study. Methods Conventional PCR to detect BPV1/2 was performed with genomic DNA extracted from equine sarcoid (n = 10) and bovine papilloma (n = 10) samples collected in Japan. Direct sequencing results were compared between equine and bovine (equine/bovine)-derived BPV to identify sarcoid-associated variants of two early regions (E2, E5), one late region (L1) and the long control region (LCR). Phylogenetic and phylogeny-trait correlation were analysed using Bayesian Markov chain Monte Carlo (MCMC) method and Bayesian tip-association significance testing (BaTS). Results Seven BPV1 and three BPV2 were identified from equine sarcoids using PCR and direct sequencing. Sequence analysis of equine/bovine-derived samples showed no sarcoid-associated variants in four regions (E2, E5, L1 and LCR) of either BPV1 or BPV2. The phylogenetic tree of BPV1 E2, L1 and LCR tended to cluster within its geographic origins. BaTS analysis demonstrated that BPV1 sequence variability may be due to the geographic origin rather than host species difference. Main limitations There was a limitation in sample numbers. Conclusions This study supports the geographic-specific hypothesis of sequence variability, suggesting that BPV1 is shared between local equids and bovids. However, more extensively collected sequences worldwide and functional evaluations are needed to verify the geographic-specific sequence variability of BPV1/2 between equine- and bovine-derived sequence.

Sarcoids are the most commonly diagnosed skin tumours in equines. Bovine papillomaviruses (BPVs) are the primary causative agent of sarcoids. There has been intensive research to discover the molecular mechanisms that may contribute to the aetiopathogenesis of this disease and tumour suppressors and proto-oncogenes known to play a role in human neoplastic conditions have been investigated in equine sarcoids. Current approaches include the identification of gene expression profiles, characterising sarcoid and normal skin tissues, and an assessment of epigenetic alterations such as microRNA differential expression and DNA methylation status. This review focuses on selected groups of genes that contribute to the molecular mechanisms of sarcoid formation. These genes have the potential to complement current clinical examinations of equine sarcoid disease in diagnosis, prognosis, therapeutic response and screening.

Sarcoids are common equine skin tumors where the risk of recurrence after treatment is high, and better treatment options are warranted. Calcium electroporation is a novel anti-cancer treatment where lethally high calcium concentrations are introduced into the cells by electroporation, a method where short high-voltage pulses induce transient permeabilization of the cell membrane. This study investigated the safety and long-term response of calcium electroporation on sarcoids. Thirty-two sarcoids in eight horses were included. The study suggested that calcium electroporation is a safe and feasible treatment for sarcoids, including inoperable sarcoids. Horses were treated once (2/8) or twice (6/8) under general anesthesia, where sarcoids were injected with 220 mM calcium chloride followed by electroporation with 8 pulses of 100 &mu, s, 1 kV/cm, and 1 Hz. Biopsies were taken prior to treatment. The sarcoid size was monitored for 12&ndash, 38 weeks after the first treatment. Complete response was observed in 22% (6/27) of treated sarcoids, and partial response in 22% (6/27), giving a 44% total response. Treatment efficacy did not appear to be related to location, type, or size. In all non-biopsied lesions, a complete response was seen (4/4). In conclusion, in this small study, 44% of sarcoids responded with 22% of sarcoids disappearing.

Research has shown that the accuracy of the clinical diagnosis of equine sarcoids (ES) can be improved. Particularly, less experienced veterinarians are often mistaken in their clinical judgement despite a high level of diagnostic confidence. The aim of this study was to develop and assess the performance of a diagnostic protocol (DP) to improve diagnostic accuracy and identify diagnostically challenging cases. The design of the DP was based on typical clinical features of ES and its algorithm was optimised through repeated tests on clinical cases prior to validating its performance in a representative online examination. A total of 22 equine practitioners and 31 veterinary students used the DP to diagnose 40 standardised ES and non-ES cases in an online examination. Scores of these 53 respondents were compared to scores of 128 respondents of comparable levels of expertise, and 14 experts, all assessing the same cases without using the DP. Overall, respondents using the DP were significantly more likely (odds ratio (OR) 1.25; 95% confidence interval (95% CI) 1.09-1.43) to diagnose a case correctly compared to respondents not using the DP and felt significantly more confident of their diagnosis (OR 1.53; 95% CI 1.39-1.67). Thus, the DP proved to be a reliable tool to increase clinical diagnostic accuracy and diagnostic confidence. The DP algorithms may be further improved with experiences gained from its application in equine practice and clinicians will be able to optimise their diagnostic accuracy and selection of lesions requiring a biopsy.

In the recent years, particular attention was given to the research aimed at optimizing the use of tumour epigenetic markers. One of the best known epigenetic changes associated with the process of carcinogenesis is aberrant DNA methylation. The aim of the present research was to evaluate the methylation profile of genes potentially important in the diagnosis and/or prognosis of equine sarcoids, the most commonly detected skin tumours in Equidae. The methylation status of potential promoter sequences of nine genes: APC, CCND2, CDKN2B, DCC, RARβ, RASSF1, RASSF5, THBS1 and TRPM1, was determined using bisulfite sequencing polymerase chain reaction (BSP-CR). The results of this study did not reveal any changes in the level of DNA methylation in the analysed group of candidate genes between the tumour and healthy tissues. Despite numerous reports describing the aberrant methylation of the promoters of the analysed genes in human cancers, the data obtained did not confirm the existence of such relationships in the examined tumour tissues, which excludes the possibility of using these genes for the diagnosis of the equine sarcoid.

Bovine papillomavirus (BPV) types 1 and 2 are recognized as the main cause of equine sarcoids. However, some studies report that up to a quarter of these tumors do not contain detectible BPV1 or BPV2 DNA. The absence of detectible BPV1 or BPV2 in these sarcoids suggests the possible involvement of other papillomavirus types. Currently, five deltapapillomaviruses are recognized to cause mesenchymal neoplasia after cross-species infection. In addition to BPV1 and BPV2, BPV13 has been associated with equine sarcoids in Brazil, BPV14 has been associated with feline sarcoids, and Ovis aries papillomavirus 2 caused a sarcoid-like lesion in a pig. To investigate the cause of equine sarcoids, PCR primers were developed to specifically amplify each of the five different deltapapillomaviruses that have been associated with mesenchymal neoplasia. The specificity of these primers was confirmed using samples of formalin-fixed tissue known to contain each PV type. These primers allow rapid and sensitive detection of deltapapillomavirus DNA in equine sarcoids. As studies have revealed marked regional variability in the cause of equine sarcoids, these primers will be useful to determine the predominant PV type causing sarcoids in a region. Additionally, there is a single report describing mixed infections by BPV1 and BPV2 in equine sarcoids. The specific primer sets are expected to enable more sensitive detection of mixed infections in equine sarcoids. Determining the cause of equine sarcoids is important as vaccines are developed to prevent these common malignant neoplasms.

The equine sarcoid is a common, locally aggressive fibroblastic cutaneous skin tumour. It can appear anywhere on the body, but is most commonly found on areas where flies can land, such as the medial thigh or neck. There are six distinct forms of equine sarcoid and these range from less severe forms to more aggressive types. There are a number of treatment options, and the treatment will depend on the individual horse. This article describes the six types of equine sarcoids and discusses the treatment options available.

Equine sarcoids are the most commonly detected skin tumours in Equidae. In the present research, a comparative transcriptomic analysis was performed which aimed at looking inside a tumour biology and identification of the expression profile as a potential source of cancer specific genes useful as biomarkers. We have used Horse Gene Expression Microarray data from matched equine sarcoids and tumour-distant skin samples. In total, 901 significantly differentially expressed genes (DEGs) between lesional and healthy skin samples have been identified (fold change ≥ 2; P

Objective: To assess Equine Sarcoid: Epidemiology and its clinical impact in working donkeys in selected districts of central Ethiopia. Methods: A Cross sectional study was conducted between November, 2009 to April 2010 to assess the epidemiology and clinical impact of equine sarcoids in working donkeys. A structured questionnaire survey was also designed to collect data on current status of sarcoid on donkeys. A random sampling technique was used to select a total of 394 working donkeys in this study. Selected donkeys were clinically examined properly for visible skin lesion. Results: Among a total of donkeys observed during study period, 31 (7.9%) were diagnosed sarcoid positive. A Chi square analysis was used to determine degree of association between risk factors and prevalence of sarcoid infection. The analysis revealed that sarcoid in working donkeys were significantly higher (P

Resumo:Sarcoides são tumores fibroblásticos, considerados os tumores de pele mais comuns em pele de equinos e que raramente apresentam regressão espontânea. Papilomavírus bovino (BPV) tipos 1 e 2 são relacionados com a patogenia do sarcoide e, provavelmente, o BPV tipo 13 (BPV13), recentemente descrito, também pode estar associado com a formação dessa lesão. Neste estudo, 20 amostras de lesões cutâneas, sendo 12 constituídas por tecidos frescos e 8 amostras de tecido fixado em formalina e embebido em parafina, provenientes de 15 cavalos foram utilizadas para a identificação do DNA de BPV. A análise histopatológica (HE) confirmou todas as lesões como sarcoide. Para a amplificação do DNA de papilomavírus (PV) foram realizadas três reações de PCR. Como triagem, os primers IFNR2/IDNT2 foram utilizados para amplificar um fragmento da ORF L1 do PV. O segundo par de primersutilizado é complementar a sequência dos genes E5 e L2 de BPVs 1, 2 e 13. O terceiro par de primers(FAP59/FAP64) utilizado tem o gene L1 como alvo. A primeira e a segunda PCRs permitiram amplificar produtos em todas as amostras avaliadas. Entretanto, na terceira reação, na qual foram utilizados os primers FAP, foi possível amplificar produtos com tamanho molecular esperado somente nas amostras constituídas por tecidos frescos. O sequenciamento de nucleotídeos e as análises filogenéticas realizadas nos fragmentos E5L2 resultaram na identificação de BPV1, 2 e 13 em 14 (70%), 2 (10%) e em 4 (20%) amostras de sarcoides, respectivamente. As amostras de sarcoides de um dos animais continha somente o DNA de BPV1. Entretanto, nas amostras provenientes do segundo cavalo foi possível identificar o DNA de três tipos de Deltapapillomavirus bovino (BPV1, 2 e 13) em lesões distintas. Este estudo ratifica a presença do DNA de BPV1, 2 e 13 em lesões de sarcoides em equinos, além de identificar três tipos de BPVs em um mesmo animal e descrever pela primeira vez no Brasil a presença de BPV1 e 2 nesse tipo de lesão. Abstract:Sarcoids are fibroblastic lesions, which are considered as the most common skin tumors of horses; spontaneous regression rarely occurs. The bovine papillomavirus (BPV) types 1 and 2 may be involved in the pathogenesis of sarcoids, and probably the recently described BPV type (BPV13) might be associated with the pathogenesis of this lesion. This study characterized the DNA of BPVs in sarcoids from 15 horses from Brazil by analyzing 20 cutaneous lesions (12 recently collected; 8 from formalin-fixed paraffin-embedded (FFPE) tissues). Histopathology confirmed the proliferative lesions as sarcoids. Three PCRs were performed to amplify papillomavirus (PV) DNA. For screening, the primers IFNR2/IDNT2 were used to amplify a fragment of the PV L1 ORF. The second primer set was complementary to a common sequence of the E5L2 genomic region of BPV1, 2, and 13. The third primer pair (FAP59/FAP64) targeted a fragment of the PVs L1 ORF. The screening and E5L2 PCRs yielded amplicons in all samples evaluated. The FAP amplicons identified BPV1, 2, and 13 only from fresh tissue samples. The phylogenetic analyses of E5L2 resulted in the identification of BPV1, 2, and 13 in 14 (70%), 2 (10%), and 4 (20%) sarcoids, respectively. Two horses demonstrated multiple lesions: the sarcoids of one of these contained only BPV1 DNA and those of the other contained three types of bovine Deltapapillomavirus (BPV1, 2, and 13). This study confirmed the presence of BPV1, 2, and 13 DNA in equine sarcoids. Moreover, these findings represent the first description of three types of BPV diagnosed in the same horse, as well as the first confirmation of BPV1 and 2 in horses from Brazil.

Although they are the most common neoplasms in equids, sarcoids are not fully characterized at the molecular level. Therefore, the objective of this study was to characterize the landscape of structural rearrangements, such as copy number variation (CNV) and copy neutral loss of heterozygosity (cnLOH), in the genomes of sarcoid tumor cells. This information will not only broaden our understanding of the characteristics of this genome but will also improve the general knowledge of this tumor and the mechanisms involved in its generation. To this end, Equine SNP64K Illumina microarrays were applied along with bioinformatics tools dedicated for signal intensity analysis. The analysis revealed increased instability of the genome of sarcoid cells compared with unaltered skin tissue samples, which was manifested by the prevalence of CNV and cnLOH events. Many of the identified CNVs overlapped with the other research results, but the simultaneously observed variability in the number and sizes of detected aberrations indicated a need for further studies and the development of more reliable bioinformatics algorithms. The functional analysis of genes co-localized with the identified aberrations revealed that these genes are engaged in vital cellular processes. In addition, a number of these genes directly contribute to neoplastic transformation. Furthermore, large numbers of cnLOH events identified in the sarcoids suggested that they may play no less significant roles than CNVs in the carcinogenesis of this tumor. Thus, our results indicate the importance of cnLOH and CNV in equine sarcoid oncogenesis and present a direction of future research.

E quine sarcoids are a problematic and frustrating form of skin ‘cancer’ affecting all types of equid. Despite the availability of over 40 different treatment modalities, none provides a 100% cure. Inappropriate treatment is dangerous as it can trigger aggressive local expansion of the sarcoid, severely impacting the use and value of the animal. It is, therefore, imperative that owners seek prompt veterinary advice regarding diagnosis and treatment of sarcoids, and use the most appropriate treatment as the first-line option. Equine sarcoids have been recognised for thousands of years and are currently responsible for approximately 90% of the skin tumours recognised in horses and ponies across the world. They are associated with the presence of bovine papilloma-virus types 1 and 2, although the actual pathophysiology is complex and extremely unpredictable. Sarcoids occur in approximately 3–8% of horses, with often very variable appearances and behaviours. A clinically-based classification is described in Table 1. Each sarcoid type should be considered a form of equine skin cancer — a tumour of the fibroblast cells responsible for many structural aspects of the skin, including wound healing and scar tissue formation.

Bovine papillomavirus (BPV) types 1 (BPV-1) and 2 (BPV-2) are causally associated with the development of equine sarcoid tumors. Recurrence rates after surgical excision of sarcoids are estimated to be 30%–40%. We hypothesized that the presence of BPV DNA in histologically tumor-free surgical margins of sarcoids is associated with risk of recurrence, and increased quantity of BPV DNA is associated with increased risk of recurrence. Formalin-fixed sarcoids classified as “completely excised” histologically were obtained from two institutions. A total of 25 tumors were included, eight of which recurred within 1 year of excision. Qualitative and quantitative polymerase chain reaction (PCR) tests for detection of BPV-1 and BPV-2 were performed on neoplastic tissue and tumor-free surgical margins in formalin-fixed paraffin-embedded biopsy specimens following DNA extraction. Bovine papillomavirus-1 was found in all tumor samples and in histologically “clean” margins of 21 samples, whereas BPV-2 was found in only two tumor samples. Although quantitative PCR was more sensitive than qualitative PCR in detecting BPV DNA in surgical margins, there was no significant difference in the presence of BPV-1 or BPV-2 DNA in margins of tumors that recurred versus those that did not recur for either test. Although this study is limited by sample size, our results suggest that PCR analysis of surgical margins for BPV DNA is not a reliable method to predict equine sarcoid recurrence after resection.

Different types of sarcoid were recorded in 145 drafting equine animals admitted to Brooke mobile clinic in Delta region, Egypt during the period from 2016 to 2018. All cases were diagnoses based on the case history, clinical picture and histopathological examination. Animals suffered from granulomatous ulcerative lesions in head and neck region (n=63), hind limbs (n=25), fore limbs (n=42) and other sites as chest, trunk and perineal region (n=15). Lesions appeared spontaneously, and its size increased with time. Some of them were round firm pedunculated while others were non-pedunculated (sessile). Some of them had characteristic fleshy ulcerated appearance while others had rough ulcerated surface. The most common types of sarcoid recorded in this study were fibroblastic (n=103), verrucous(n=8), nodular (n=7), mixed (n=20) and occult (n=7).

The Papillomaviridae family comprises a large number of viruses that can infect a broad range of hosts including mammals, birds and reptiles giving rise to benign lesions of the skin or mucosal membranes. They are characterized by great genetic diversity yet adhere to common biological principles. In this review, we first describe the structure and function of the viral proteins encoded by papillomaviruses (PVs), with a particular emphasis on bovine papillomaviruses (BPV). We then discuss the role of BPV types 1 and 2 in the pathogenesis of equine sarcoids and present recent evidence implicating a novel equine papillomavirus (EcPV-2) in the pathogenesis of equine genital cancers.

Photodynamic therapy (PDT) holds great promise in treating veterinary and human dermatological neoplasms, including equine sarcoids, but is currently hindered by the amount of photosensitiser and light that can be delivered to lesions thicker than around 2 mm, and by the intrinsic antioxidant defences of tumour cells. We have developed a new PDT technique that combines an efficient transdermal penetration enhancer solution, for topical delivery of 5-aminolevulinic acid (ALA) photosensitiser, with acute topical post-PDT application of the glycolysis inhibitor lonidamine. We show that the new PDT combination treatment selectively kills sarcoid cells in vitro, with repeated rounds of treatment increasing sarcoid sensitisation to PDT. In vivo, ALA PDT followed by 600 μM lonidamine substantially improves treatment outcomes for occult, verrucous, nodular and fibroblastic sarcoids after 1 month (93% treatment response in 27 sarcoids), compared with PDT using only ALA (14% treatment response in 7 sarcoids).

Equine sarcoids develop upon bovine papillomavirus type 1 or 2 (BPV1, BPV2) infection in conjunction with trauma and represent the most common tumour disease in horses and other equids, including donkeys. In face of a sarcoid outbreak involving 12 of 111 donkeys and mules at the ‘Rifugio degli Asinelli’, a subsidiary charity organization of The Donkey Sanctuary, non-invasively collected sample material including crusts, dandruff, swabs and hair roots was collected from sarcoid-affected and 26 healthy donkeys, as well as dandruff from a grooming kit and tabanids caught from or in the vicinity of sarcoid patients. In addition five previously collected sarcoids stored in formalin were provided. DNA isolated from collected material was tested for the presence of the BPV1/2 E5 oncogene using PCR. Positive samples were further analysed by E2/E4 and LCR PCR and amplicon sequencing to determine a possible common source of infection via comparative alignment of intralesional BPV1/2 gene variants. IC/PCR was used to assess sample aliquots for the presence of BPV1/2 virions, and IHC to analyse five tumours for BPV1 E5 and L1 protein expression. All sarcoid-affected donkeys, two of 55 tabanids and dandruff from a curry comb tested positive for BPV1/2 E5, yet negative by IC/PCR. Healthy animals were BPV1/2-free. IHC revealed different levels of intralesional E5 and L1 expression. A series of BPV1 E5, E2, and LCR variants and BPV2 E5 were detected from donkeys, indicating that they had accidently developed sarcoids at about the same time rather than having acquired disease from each other.

Compared to other animals, especially companion animals like dogs, neoplasias of the external genitalia are rarely diagnosed in the horse. The most commonly occurring tumors are squmaous cell carcinomas and equine sarcoids; papillomas, melanomas, fibromas, fibrosarcomas or lymphomas are found more infrequently. Squamous cell carcinomas usually afflict older horses, mostly geldings and occasionally stallions, while younger horses tend to have a disposition towards developing equine sarcoids. Special attention should be paid to thorough diagnostics in order to initiate a precise therapy at an early stage, before the tumors are inaccessible due to invasive growth or even metastasis.

The enzyme cyclooxygenase-2 (COX-2) is expressed in some tumor and stromal tissues, and catalyzes production of prostaglandins with growth stimulatory, antiapoptotic, proangiogenic, and immunosuppressive properties. Pharmacologic inhibition of COX-2 is associated with antitumor activity in various human and canine malignancies. The purpose of this study was to assess COX-2 expression in a series of equine sarcoids, melanomas, and squamous-cell carcinomas (SCC). COX-2 expression was assessed in formalin-fixed paraffin-embedded tissues from 14 sarcoids, 11 melanomas, and 37 SCC that represent various anatomic sites by using standard immunohistochemical methods. COX-2 was expressed in 2 of 14 sarcoids, 7 of 11 melanomas, and 32 of 37 SCC, 56% of which demonstrated moderate-to-strong immunoreactivity. There were no differences in expression between anatomic sites. In conclusion, most equine SCC and many melanomas appear to express COX-2 and thus could respond to COX-2 inhibitor therapy.

Bovine papillomavirus type 1 or 2 (BPV-1, BPV-2) are accepted causal factors in equine sarcoid pathogenesis. Whereas viral genomes are consistently found and expressed within lesions, intact virions have never been detected, thus permissiveness of sarcoids for BPV-1 replication remains unclear. To reassess this issue, an immunocapture PCR (IC/PCR) was established using L1-specific antibodies to capture L1-DNA complexes followed by amplification of the viral genome. Following validation of the assay, 13 sarcoid-bearing horses were evaluated by IC/PCR. Samples were derived from 21 tumours, 4 perilesional/intact skin biopsies, and 1 serum. Tissue extracts from sarcoid-free equines served as controls. IC/PCR scored positive in 14/24 (58.3%) specimens obtained from sarcoid-patients, but negative for controls. Quantitative IC/PCR demonstrated

Topical acyclovir application is an owner-friendly treatment for occult equine sarcoids, without the caustic side-effects other topical treatments have. Variable clinical success rates have been described, but it is not known to what rate and extent acyclovir penetrates in and through equine skin from a topical formulation. In the current study, an in vitro Franz diffusion model was used to determine the permeation parameters for a generic 5% acyclovir cetomacrogol cream for both healthy and sarcoid equine skin. The distribution of acyclovir between different layers of both skin types was also evaluated. While acyclovir penetrated through both skin types, significantly less acyclovir permeated to the deep dermis of sarcoid skin (197.62ng/mm(3)) compared to normal skin (459.41ng/mm(3)). Within sarcoid skin samples, significantly higher acyclovir concentrations were found in the epidermis (983.59ng/mm(3)) compared to the superficial dermis (450.02ng/mm(3)) and the deep dermis. At each sample point, significantly more acyclovir permeated to the receptor fluid through normal skin compared to sarcoid skin, which is reflected in the significantly higher permeation parameters of normal skin. Normal skin was found to be more permissive for acyclovir, but even in sarcoid skin, enough acyclovir reached the deep dermis to treat a Herpes simplex virus infection. In the case of equine sarcoids, the treatment is aimed at the Bovine papillomavirus and no information is available on the susceptibility of the DNA polymerase of this virus for acyclovir. Therefore, further research is needed to determine the efficacy of acyclovir to treat equine sarcoids.

Imiquimod is an immune response modifier with potent antiviral and antitumour activity. The objective of this pilot study was to evaluate the efficacy of an imiquimod 5% cream (Aldaratrade mark: 3M, Saint Paul, MN, USA) as a topical treatment for equine sarcoids. Fifteen horses with a total of 19 tumours were enrolled, including mixed (7), fibroblastic (5), flat (3), verrucous (2), and nodular (2) types. Baseline data included history, physical examination, tumour location, measurement and digital photography. Imiquimod was applied by the owners three times a week until complete resolution of the tumour or 32 weeks, whichever occurred first. Tumours were measured and photographed every 4 weeks. Treatment efficacy was defined as 75% or greater reduction of tumour size by the end of the trial. Four sarcoids were withdrawn from the study. Twelve of the remaining 15 tumours (80%) showed more than 75% reduction in size and nine (60%) totally resolved between 8 and 32 weeks. The most common adverse effects of exudation, erythema, erosions, depigmentation and alopecia were limited to the tumour and adjacent areas. The results suggest that topical imiquimod is a therapeutic option for the treatment of equine sarcoids, although more detailed studies are required to corroborate these initial findings.

Summary Background Medical textiles offer a unique contact opportunity that could provide value-added comfort, reliability, and safety for light or laser-based applications. We investigated a luminous textile diffuser for use in photodynamic therapy. Methods Textile diffusers are produced by an embroidery process. Plastic optical fibers are bent and sewn into textile to release light by macrobending. A reflective backing is incorporated to improve surface homogeneity, intensity, and safety. Clonogenic assay (MCF-7 cells) and trypan blue exclusion (NuTu19 cells) tests were performed in vitro using 0.1 μg/ml m-THPC with three textile diffusers and a standard front lens diffuser. Heating effects were studied in solution and on human skin. PDT application in vivo was performed with the textile diffuser on equine sarcoids (three animals, 50 mW/cm 2 , 10–20 J) and eight research animals. Lastly, computer simulations were performed to see how the textile diffuser might work on a curved object. Results At low fluency rate, there is a trend for the textile diffuser to have lower survival rates than the front lens diffuser for both cell lines. The textile diffuser was observed to retain more heat over a long period (>1 min). All animals tolerated the treatments well and showed similar initial reactions. The simulations showed a likely focusing effect in a curved geometry. Conclusions The initial feasibility and application using a textile-based optical diffuser has been demonstrated. Possibilities that provide additional practical advantages of the textile diffuser are discussed.

The purpose of the present study was to examine whether bovine papillomavirus (BPV) DNA can be detected on the normal skin and in the habitual surroundings of horses with and without equine sarcoids by means of superficially taken swabs. In affected horses, no significant difference in presence of BPV-DNA could be observed between samples obtained from the equine sarcoid surface, from normal skin close to the tumour and from a normal skin site in direct contact with the tumour. From the group of healthy horses living in contact with affected horses, 44% were BPV-DNA positive. The surroundings of affected and non-affected horses are probably not a major source of BPV-DNA contamination. It can be concluded that BPV-DNA is present on the normal skin of horses affected by equine sarcoid and to a lesser degree, on the normal skin of horses living in contact with affected horses.

Ninety-five horses with sarcoids were subjected to three types of treatment: surgical excision (conventional or carbon dioxide laser), cryotherapy or local BCG vaccination. The type of treatment was selected on the basis of the size, location and clinical appearance of the tumours. The choice between conventional and laser excision was empirical. A successful outcome was obtained in 1 1 of 14 (79 per cent) of the horses treated by cryosurgery, 18 of 27 (67 per cent) treated by BCG vaccination, 18 of 22 (82 per cent) treated by conventional excision, and 20 of 28 (71 per cent) treated with a carbon dioxide laser. For both excision methods, rigorous measures were taken to avoid autoinoculation and to ensure a wide margin of normal skin. The probability of local recurrence after excision was significantly higher for large sarcoids and sarcoids which had previously failed to respond to treatment. In 10 of the 31 horses with remaining sarcoids, some or all of the untreated sarcoids were observed to regress spontaneously.

BPVs are double stranded DNA viruses that can infect several species other than the natural host, cattle, including equids. In equids, BPV-1, and, less commonly BPV-2, infection gives rise to fibroblastic tumours of the skin. Whilst a causal relationship between BPV-1/2 and equine sarcoids is now well established, how the disease is transmitted is not known. In this study we show BPV-1 DNA can be detected in flies trapped in the proximity of sarcoid-affected animals. Sequence analysis of the BPV-1 LCR from flies indicates that flies harbour BPV-1 LCR sequence variants II and IV which are commonly detected in equine sarcoids. These data suggest that flies may be able to transmit BPV-1 between equids.

Equine sarcoids are locally aggressive fibroblastic neoplasms considered to be the most common skin tumors of horses worldwide. Bovine papillomavirus types 1 and 2 have typically been associated with sarcoids in equids. Investigations aiming to identify papillomavirus strains, aside from bovine papillomaviruses 1 and 2, which might be associated with sarcoid lesions, have been lacking. The aim of this article is to report the identification of a third bovine papillomavirus type, bovine papillomavirus 13, associated with equine sarcoids. Six sarcoid lesions were collected from diverse anatomical sites on two horses from southern Brazil. To detect a broad spectrum of papillomavirus strains, eight degenerate primer pairs designed to detect conserved regions on the L1 and E1 genes were tested on the DNA samples. Direct sequencing was then performed on the obtained amplicons, and sequence identities were compared with sequences from all bovine papillomavirus types. The FAP59/FAP64, MY09/MY11, and AR-E1F2/AR-E1R4 sequences generated from the sarcoids were shown to present 99 to 100% identity with bovine papillomavirus 13, a new bovine papillomavirus type previously described in cattle. The results from this study suggest that there is a need to identify bovine papillomavirus type 13 and other papillomavirus strains that might be associated with sarcoids in diverse geographical areas; such investigations might establish the frequency of occurrence of this viral type in these common tumors of equids.