The clinical diagnosis of equine sarcoids—Part 2: Assessment of case features typical of equine sarcoids and validation of a diagnostic protocol to guide equine clinicians in the diagnosis of equine sarcoids

A randomized placebo-controlled double-blinded study comparing oral and subcutaneous administration of mistletoe extract for the treatment of equine sarcoid disease

BACKGROUND

Equine sarcoids (ES) are the most common cutaneous tumors in equids. Systemic treatment options are sparse. Subcutaneous (SC) injections of Viscum album extract (VAE) demonstrate efficacy as a systemic treatment directed against ES.

OBJECTIVES/AIM

To critically assess the therapeutic efficacy of orally administered VAE.

ANIMALS

Forty-five ES-affected, privately owned, 3-12 year-old horses.

METHODS

A 3-armed randomized placebo-controlled, double-blinded study was conducted in a double-dummy design. Horses were subjected to oral administration and SC injections of either VAE or placebo (VAE oral/placebo SC, VAE SC/placebo oral, placebo oral/placebo SC) over a 7-month treatment period. Primary endpoint was the change of baseline of a composite index of ES number and ES area after 14 months. Second endpoint was the clinical response.

RESULTS

No statistically significant difference in the composite endpoint between the 3 study arms was found. The primary endpoint showed 4 (27%) horses in the VAE oral group with complete ES regression, 3 (21%) in the VAE SC injection group, and 2 (13%) in the placebo group. The clinical response revealed complete or partial regression in 6 horses of the oral VAE group (40%), 4 of the SC injection group (29%), and 4 of the placebo group (25%). Direct comparison of oral VAE and placebo showed an odds ratio, stratified for prognosis of 2.16 (95%-CI: 0.45-10.42) and a P-value of 0.336.

CONCLUSION AND CLINICAL IMPORTANCE

Oral administration of VAE is well tolerated. No statistically significant difference in the effectiveness of systemic VAE versus placebo against ES was found.

Longitudinal pilot study examining the effect of punch biopsy on equine sarcoid growth dynamics

BACKGROUND

Nonexcisional tissue biopsies facilitate pre-operative confirmation of equine sarcoid yet fear of lesion deterioration currently limits its use in the diagnostic workup.

OBJECTIVES

To evaluate the effect of a single punch biopsy on tumour growth dynamics [thickness, area, circumference, viral load (VL) and Visual Analog Scale (VAS)].

ANIMALS

Six client-owned horses with 11 sarcoids of various classification.

MATERIALS AND METHODS

Growth dynamics were recorded on a weekly basis, 12 weeks pre- and 24 weeks post-biopsy. The effect of a single punch biopsy on growth dynamics was estimated by linear mixed-effect models. Spearman's rank correlation coefficient (SRCC) was calculated to investigate correlations with the number of weeks before and after the intervention.

RESULTS

While statistically significant post-biopsy changes were recorded for all parameters except VL, no parameter was consistently increased after the biopsy intervention. In two of 11 sarcoids, the VL correlation pattern revealed significant strong correlations: sarcoid 6 (pre: r = -0.66, p < 0.05; post: r = 0.81, p < 0.001), increased VL; and sarcoid 8 (pre: r = 0.85, p < 0.001; post: r = 0.17, p > 0.05), no further increase after biopsy.

CONCLUSIONS AND CLINICAL IMPORTANCE

Our results indicate that post-biopsy lesion deterioration is not a general concept that applies to all sarcoids, and both deterioration or improvement are possible outcomes over a 24-week period. Further clinical studies with a larger sample size are needed before a definitive conclusion can be made.

Complete genomic characterization of bovine papillomavirus type 1 and 2 strains infers ongoing cross-species transmission between cattle and horses

Infection with bovine papillomavirus (BPV) types 1 and 2 results in the most common skin tumor of horses, termed equine sarcoid. The persistent and recurrent nature of this tumor stands in contrast to the regressive nature of BPV-1/- 2 induced cutaneous papillomas in cattle. The circulation of horse-specific BPV-1/- 2 variants within equine populations has been suggested as a possible explanation for the difference in clinical presentation of BPV-1/- 2 infection between horses and cattle. In order to investigate this hypothesis, we identified 98 complete BPV-1/- 2 genomes using a Nanopore sequencing approach. Separate BPV-1/- 2 alignments were used to infer Bayesian phylogenetic trees. Phylogeny-trait association concerning host species was investigated using Bayesian Tip-association Significance software (BaTS) Overall, 179 unique BPV-1 and 128 BPV-2 substitutions were found. The E2 coding region in the viral genome exhibited an exceptionally high rate of non-synonymous mutations (81 %, n = 13/16). Interestingly, extensive deletions in the L1/L2 region (up to 1.5 kb) were found exclusively in horse-derived samples. Nevertheless, the most frequently detected single nucleotide polymorphisms were shared between equine and bovine hosts, which is in agreement with BaTS results indicating no phylogeny-host correlation. We found indications that horse-specific mutations might exist in subpopulations of equine derived BPV-1/- 2, but these did not result in horse-adapted genetic variants. Based on these observations, cross-species transmission from cattle to horses seems to be an ongoing process, rather than an ancient occurrence that has been followed by the circulation of horse-adapted BPV variants in the horse population..

Histological evidence of superficial inflammation is associated with lower recurrence of equine sarcoids following surgical removal: A follow-up study of 106 tumours in 64 horses

Although the equine sarcoid is the most common skin neoplasm in domesticated horses, histopathological characteristics have not previously been evaluated for association with recurrence. The aim of this retrospective cohort study was to investigate clinical and histopathological features of excised equine sarcoids and to evaluate their association with recurrence at the original surgical site and at new sites. Clinical records and excisional biopsies from 106 equine sarcoids from 64 horses referred to Leahurst Equine Hospital, University of Liverpool, between March 2010 and February 2015 were retrieved. Biopsies were re-evaluated histologically. Clinical data were obtained from hospital records, and owner-reported follow-up data were obtained by telephone questionnaire. Associations between clinical and histopathological features of sarcoids and their recurrence at the surgical site were determined using uni- and multivariable mixed effects logistic regression. Recurrence of sarcoids at the surgical site occurred in 30 horses (46.9%). Sarcoids developed at a distant site in 21 horses (32.8%). In the final mixed effects logistic regression model, only superficial inflammation was associated with reduced odds of recurrence at the surgical site (adjusted odds ratio, 0.32; 95% confidence intervals, 0.10-0.96; P = 0.04). This suggests that the inflammatory process may play a role in protecting horses against the recurrence of sarcoids.

Immunogenicity analysis of BPV-1 positive equine sarcoid-derived cultured fibroblasts

Sarcoids are the most common equine skin tumours Although they do not metastasize, they can be locally aggressive and cause significant clinical symptoms in affected horses. Despite being common, very little is known about the host immune response and the biological mechanisms underlying persistence and recurrence of equine sarcoids. The latter reflects the need for further research in this field. This in-vitro study used sarcoid explants from horses with naturally occurring sarcoids (n = 12) to evaluate the induction of a humoral immune response directed against equine sarcoid-derived bovine papilloma-virus (BPV)- 1 infected fibroblasts using a flow cytometric crossmatch assay. The presence of antibodies against exogenous bovine serum albumin (BSA) and fibroblast-like mesenchymal stromal cells (MSCs) was also evaluated by ELISA and flow cytometry, respectively. The viral load in the sarcoid explants, the corresponding cultured sarcoid fibroblasts, and matched peripheral blood mononuclear cells (PBMCs) from affected horses were determined by quantitative BPV-1/- 2 PCR analysis. Antibodies against autologous sarcoid cells were present in six out of twelve sarcoid-affected horses. Serum from all horses showed cross reactivity with allogeneic sarcoid cells, while only a part reacted with BSA or MSCs. Screening of host PBMCs demonstrated the absence of BPV E1 nucleic acids. Statistical analysis revealed a significantly higher mean viral load in the parental sarcoid tissue compared to the low passage fibroblasts (P < 0.001). These results support the hypothesis that sarcoid-affected horses may develop antibodies recognizing tumour-specific antigens. In contrast to sarcoid explants, equine PBMCs do not seem to contain complete BPV genomes. These results provide a basis for future investigations on the clinical relevance of these antibodies.

Patho-histological features of fibroblastic sarcoid in horses

Sarcoid is one of the most common skin tumours, which is diagnosed in various breeds of horses at any age regardless of the animal’s sex. Such fibroblastic neoplasm manifests itself in several clinical ways with its specific morphological features. As a rule, it metastasizes rarely but can be locally invasive. The disease’setiology is multifactorial and includes the confirmed role of the bovine papillomavirus and genetic and environmental factors. The article introduces the results of a retrospective study of horses of the Ukrainian riding breed with a fibroblastic sarcoid type, which was localized mainly in the area of the external thoracic vein. Neoplasms were represented by two types. The first one included broad base neoplasms without a pronounced pedicle but with signs of hyperkeratosis. Massive rounded dense formations with an ulcerated surface refer to the second type. To verify the studied types of sarcoid, wide surgical excision of the lesion’svisible parts was performed, followed by the selection of fragments for the pathohistological diagnosis. Also, additional staining methods were used to detect the connective and muscle tissue (Van Gieson’s staining) and elastic fibers (Weigert’s resorcin-fuchsin staining). Microscopically, the neoplasm without a visible pedicle showed signs of hyperkeratosis and acanthosis in the peritumoral epidermal layer. Epidermis desquamation with a significant amount of oxyphilic detritus, diapedesis hemorrhages, and dilated vessels was also detected in some areas. Chaotic placement of fibroblasts and fibrocytes was noted, to a greater extent, subdermally. Anisocytosis and anisokaryosis were expressed moderately. Sarcoids, macroscopically presented in the form of massive dense formations with an ulcerated surface, were histologically characterized by the replacement of the epidermis with cellular elements, subdermal hemorrhages, and the characteristic perpendicular orientation of coarse collagen fibers towards the basement membrane. Closely spaced spindle-shaped cells with fibers forming moiré structures were visualized in the deep dermis layers. Nuclei were hyperchromic and elongated in shape, no atypical mitoses were noted. Pathohistological examination during the identification of a sarcoid type for diagnostic purposes can cause rapid growth and formation of an ulcer. The final diagnosis regarding equine sarcoid can be made based on a combination of clinical signs, histopathological examination, and molecular genetic testing with the isolation of BPV DNA.

Cross-sectional comparison of superficial swab and fine-needle aspiration: Improving the diagnostic workup of horses with sarcoids

Although bovine papillomavirus (BPV)-induced equine sarcoids are often identified solely by clinical examination, 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.

New approach for genomic characterisation of equine sarcoid-derived BPV-1/-2 using nanopore-based sequencing

BACKGROUND

Bovine papillomavirus (BPV) types 1 and 2 play a central role in the etiology of the most common neoplasm in horses, the equine sarcoid. The unknown mechanism behind the unique variety in clinical presentation on the one hand and the host dependent clinical outcome of BPV-1 infection on the other hand indicate the involvement of additional factors. Earlier studies have reported the potential functional significance of intratypic sequence variants, along with the existence of sarcoid-sourced BPV variants. Therefore, intratypic sequence variation seems to be an important emerging viral factor. This study aimed to give a broad insight in sarcoid-sourced BPV variation and explore its potential association with disease presentation.

METHODS

In order to do this, a nanopore sequencing approach was successfully optimized for screening a wide spectrum of clinical samples. Specimens of each tumour were initially screened for BPV-1/-2 by quantitative real-time PCR. A custom-designed primer set was used on BPV-positive samples to amplify the complete viral genome in two multiplex PCR reactions, resulting in a set of overlapping amplicons. For phylogenetic analysis, separate alignments were made of all available complete genome sequences for BPV-1/-2. The resulting alignments were used to infer Bayesian phylogenetic trees.

RESULTS

We found substantial genetic variation among sarcoid-derived BPV-1, although this variation could not be linked to disease severity. Several of the BPV-1 genomes had multiple major deletions. Remarkably, the majority of them cluster within the region coding for late viral genes. Together with the extensiveness (up to 603 nucleotides) of the described deletions, this suggests an altered function of L1/L2 in disease pathogenesis.

CONCLUSIONS

By generating a significant amount of complete-length BPV genomes, we succeeded to introduce next-generation sequencing into veterinary research focusing on the equine sarcoid, thus facilitating the first report of both nanopore-based sequencing of complete sarcoid-sourced BPV-1/-2 and the simultaneous nanopore sequencing of multiple complete genomes originating from a single clinical sample.

Diagnostic and prognostic potential of eight whole blood microRNAs for equine sarcoid disease

MicroRNAs have been proposed as biomarkers for equine sarcoids, the most prevalent equine skin tumors globally. This study served to validate the diagnostic and prognostic potential of whole blood microRNAs identified in a previous study for long-term equine sarcoid diagnosis and outcome prediction. Based on findings of a clinical examination at the age of 3 years and a follow-up following a further 5–12 years, 32 Franches-Montagnes and 45 Swiss Warmblood horses were assigned to four groups: horses with regression (n = 19), progression (n = 9), new occurrences of sarcoid lesions (n = 19) and tumor-free control horses (n = 30). The expression levels for eight microRNAs (eca-miR-127, eca-miR-432, eca-miR-24, eca-miR-125a-5p, eca-miR-134, eca-miR-379, eca-miR-381, eca-miR-382) were analyzed through reverse transcription quantitative polymerase chain reaction in whole blood samples collected on initial examination. Associations of sex, breed, diagnosis, and prognosis with microRNA expression levels were examined using multivariable analysis of variance. Sex and breed influenced the expression level of five and two microRNAs, respectively. Eca-miR-127 allowed discrimination between sarcoid-affected and tumor-free horses. No variation in microRNA expression was found when comparing horses with sarcoid regression and progression. Expression levels of eca-miR-125a-5p and eca-miR-432 varied in male horses that developed sarcoids throughout the study period in comparison to male control horses. While none of the investigated miRNAs was validated for predicting the prognosis of sarcoid regression / progression within young horses with this condition, two miRNAs demonstrated potential to predict if young male (though not female) tumor-free horse can develop sarcoids within the following years. Sex- and breed- biased miRNAs exist within the equine species and have an impact on biomarker discovery.

EQUINE SARCOIDS IN CAPTIVE WILD EQUIDS: DIAGNOSTIC AND CLINICAL MANAGEMENT OF 16 CASES-A POSSIBLE PREDISPOSITION OF THE EUROPEAN COHORT OF SOMALI WILD ASS (EQUUS AFRICANUS SOMALIENSIS)?

Equine sarcoids (ES) were diagnosed in 12 Somali wild asses (SWA) (Equus africanus somaliensis) from 10 different institutions of the SWA European Endangered Species Programme from 1976 to 2019. Samples of surgically excised masses, biopsies, or necropsy samples were submitted for histologic and virologic analysis. In addition, tissue samples from one onager (Equus hemionus onager), one kulan (Equus hemionus kulan), and two Hartmann's mountain zebras (HMZ) (Equus zebra hartmannae) were examined. Histology confirmed the diagnosis of ES exhibiting the typical microscopic features. Polymerase chain reaction detected bovine papillomavirus type 1 (BPV1) DNA in eight SWA samples and bovine papillomavirus type 2 (BPV2) DNA in one SWA sample. The onager, kulan, and one HMZ sample tested positive for BPV1. The other HMZ tested positive for BPV1 and BPV2. This is the first report of ES in an onager. Surgical excision was the treatment elected by most veterinarians. A follow-up survey of the cases over several years after clinical diagnosis and therapy revealed variable individual outcome with ES recurrence in four cases. Three SWA and the kulan were euthanized due to the severity of the lesions. Nine affected SWA were males with seven having a sarcoid located at the prepuce. Because a genetic disposition is a risk factor for the development of ES in horses, this may also be true for endangered wild equids with few founder animals in their studbook history. Innovative approaches regarding therapy and prevention of ES in wild equids are therefore highly encouraged.

Diagnostic potential of three serum microRNAs as biomarkers for equine sarcoid disease in horses and donkeys

BACKGROUND

MicroRNAs (miRNAs) are potential biomarkers for equine sarcoids (ES).

OBJECTIVES

To assess eca-miR-331, eca-miR-100, and eca-miR-1 as serum biomarkers for ES disease.

ANIMALS

Sixty-eight ES cases (56 horses, 12 donkeys), 69 tumor-free controls (60 horses, 9 donkeys), and 20 horses with other skin tumors.

METHODS

For this case-control study, expression of serum eca-miR-331, eca-miR-100, and eca-miR-1 in ES-affected equids was compared to tumor-free age-, sex-, and breed-matched control horses and donkeys with other skin tumors using reverse transcription quantitative PCR (polymerase chain reaction) for relative miRNA quantification. Biological, preanalytical, and clinical variable influences on miRNA expression were examined. Receiver operator characteristic (ROC) curve analyses were used to determine differences in miRNA expression between groups.

RESULTS

The expression of eca-miR-100 was affected by age (P = .003) and expression of eca-miR-100 and eca-miR-1 were affected by hemolysis (both P < .001). Eca-miR-331 was unaffected by biological variation, hemolysis, ES type, and disease severity. Eca-miR-331 concentrations were higher in ES-affected compared to tumor-free controls (P = .002). The ROC curve analysis indicated an area under the curve of 0.65 (P = .002) with a sensitivity of 60%, specificity of 71%, and positive and negative likelihood ratios of 2.1 and 0.56, respectively, to diagnose ES. Eca-miR-331 expression did not discriminate between horses with ES and other skin tumors. Expression of eca-miR-100 and eca-miR-1 was not different between groups.

CONCLUSIONS AND CLINICAL IMPORTANCE

Serum eca-miR-331 expression is neither sensitive nor specific enough as a single ES biomarker. If combined with other miRNAs, it may be helpful for ES diagnosis.

Molecular approaches to equine sarcoids

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.