Schwarz et al. Porcine Health Management (2023) 9:17 Porcine Health Management https://doi.org/10.1186/s40813-023-00313-1 CASE REPORT Open Access A single, episodic event of unilateral/ bilateral scrotal swelling in a group of adult boars at an Austrian boar stud Lukas Schwarz1*, Sophie Dürlinger1, Vera Martin1, Herbert Weißenböck2, Rene Brunthaler2, Till Rümenapf3, Angelika Auer3, Igor Loncaric4, Irene Zimpernik5, Nicole Reisinger6, Bettina Behler‑Wöchtl7, Dragos Scarlet8,16, Gary Althouse9, Chris Kuster10, Johannes Kauffold15, Joaquim Segales11, Martine Laitat12, Pierre Thilmant13, Alexander Grahofer14 and Andrea Ladinig1 Abstract Background Scrotal swelling is a clinical situation which can be caused by different aetiologies. In this case report, we describe a multi-week episode of unilateral and bilateral scrotal swelling in boars at an Austrian boar stud and its diagnostic work-up. Case presentation In the summer of 2020, the herd veterinarian of an Austrian boar stud reported that over a period of six weeks, five out of 70 boars presented with unilateral severe swelling of the left scrotum and three out of 70 boars with bilateral severe swelling of the left and moderate swelling of the right scrotum, respectively. A complete history was obtained and an on-site evaluation of the facility was done. Five boars were necropsied, and a variety of samples harvested for further diagnostic investigations. Infectious differential diagnoses associated with unilateral swelling of the scrotum or the testis were excluded through serological and tissue testing. In three of the five boars, histopathology revealed complete acute haemorrhagic necrosis of the left testis concurrent with strongly congested blood vessels. Review of the collected information with a group of experts in the field of boar stud management resulted with consensus that, most likely, trauma was the etiologic event causing the clinical signs and pathology. Coincident with discussion of implementing video recording cameras in the boar housing area, no further clini‑ cal cases followed. As this case occurred during the first lockdown of the COVID-19 pandemic, we propose that the distress and travelling restrictions may have contributed to frustration among boar stud workers, which was conse‑ quently expressed as misbehaviour against boars. Conclusions Once all known infectious causes of unilateral swelling of the scrotum were excluded, a critical diagnos‑ tic work-up focused on non-infectious causes. Non-infectious causes, such as trauma, need to be carefully evaluated, as it may also include human misbehaviour against boars. Summarizing all findings of this case report, the authors hypothesize that a blunt trauma was the reason for the series of mainly unilateral swelling of the scrota of boars. Keywords Scrotal enlargement, Orchitis, Scrotal swelling, Swine, Boar *Correspondence: Lukas Schwarz Lukas.Schwarz@vetmeduni.ac.at Full list of author information is available at the end of the article © The Author(s) 2023. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://​creat​iveco​mmons.​org/​licen​ses/​by/4.​0/. The Creative Commons Public Domain Dedication waiver (http://​creat​iveco​ mmons.​org/​publi​cdoma​in/​zero/1.​0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Schwarz et al. Porcine Health Management (2023) 9:17 Page 2 of 10 Background semen quality, and genitalia problems) that represents Boar studs are closed husbandry systems designed for 23.7–26.4% of all cullings, followed by lameness/leg prob- semen production for artificial insemination of breeding lems (8.4–14.9%), and age (9.3–28.5%) [4–6]. Isolated sows. Management, veterinary support and animal care cases of boars with abnormalities may not be alarming in are generally done following higher standards compared regards of the whole herd, but if several cases with similar to conventional piglet producing farms, with all proce- clinical presentation occur over a short time period, this dures in boar studs being well structured and defined. is a sign that veterinary intervention is urgently required. This is an essential aspect because the health status of However, every single case needs urgent veterinary inter- boars used for semen production is reflected in the qual- vention as such isolated cases may be painful events. ity and quantity of their semen [1]. Regular monitoring In this case report we describe a multi-week episode of and surveillance of diseases and of semen quality aids unilateral and bilateral scrotal swelling in several boars at in quickly detecting abnormalities in a boars’ general an Austrian boar stud. health status [2]. In Austria, health monitoring in boar studs consists of routine serological profiling for detec- Case presentation tion of antibodies against infectious disease pathogens Anamnesis (in other words, classical swine fever virus, suid herpes- In the summer of 2020, the herd veterinarian of an Aus- virus 1, porcine reproductive and respiratory syndrome trian boar stud observed an abrupt onset of primar- virus (PRRSV), Brucella spp., Leptospira spp.), PCR- ily unilateral swelling of the left part of scrota and testis based investigations regarding PRRSV, and daily observa- of boars (~ 11.43%; 8/70 boars; Fig. 1) which extended tion of boar’s general behaviour and willingness to mount over a period of six weeks. Animal caretakers reported a phantom for semen collection. Apathy, anorexia or that the swelling of the scrota and testes developed over unwillingness to mount are strong indicators of sickness approximately one month until it reached its final size. due to various etiologic factors. Initially, the veterinarian suspected a recently introduced The establishment of quality assurance programmes infectious disease that was affecting the boars showing for boar health is essential for production of high-quality clinical signs. New boars were kept in a locally separated semen [3]. This implicates that in case of abnormalities, quarantine unit for a minimum of six weeks before they either in boars or in collected semen/ejaculates, actions were introduced into the resident herd. During quar- are required by the herd veterinarian(s) to re-establish antine and thereafter each boar of that stud got tested the quality standards in a boar stud. Primary reasons for serologically on a regular basis for notifiable diseases (in culling boars at stud include reproductive problems (for other words, African and classical swine fever, Aujesz- example, boar subfertility/infertility, low libido, poor ky’s disease, brucellosis) and for other diseases relevant Fig. 1 Selected boars with severely swollen left scrota. A Piétrain, boar 1 B Large White, boar 2 C Large White, boar 5 Schwarz et al. Porcine Health Management (2023) 9:17 Page 3 of 10 to pig reproduction (for example, PRRSV, leptospirosis, parenchyma, a thickened-hyperechoic testicular cover chlamydiosis). All boars were regularly vaccinated against surrounded by multiple, and irregular hypoechoic areas Erysipelothrix rhusiopathiae and porcine parvovirus. Out with echogenic particles (Fig. 2B, C). The cavum vagi- of the 70 boars kept in the resident stud, eight boars of nale was severely filled with fluid and separated by septa different breeds (Piétrain, Duroc, German Landrace and in caverns (Fig. 2B). The cauda epididymis correspond- Large White) and ages (one to seven years of age) were ing to the affected testis presented with a dilated ductus affected. Five boars showed unilateral swelling of the epididymis (Fig. 2D). scrotum, and three boars presented with bilateral swell- ing with a more pronounced swelling on the left side as Pathologic and histopathologic examination the main clinical sign, respectively, without expression For pathologic and histopathologic investigations, the of pain. Six out of the eight affected boars were held in five boars were anesthetized and euthanatized. Gross pens located in the same row at the stud. Initially, two pathologic lesions were mainly restricted to the scro- boars (two- and three-year-old Large White and Pié- tum and testicles. Dissection of severely swollen scrota train animals respectively) were forwarded by the herd (n = 3) resulted in the release of massive amounts of veterinarian to the University Clinic for Swine, Univer- blood-tinged fluid (Fig. 3A). In addition, fibrinous tags or sity of Veterinary Medicine Vienna, Vienna, Austria for incipient adhesions were detected between the testicles further investigation and a diagnostic work up. During a and scrotum (Fig. 3A and C; Additional file 1). Affected subsequent on-site visit to the boar stud by the Univer- testicles had central acute haemorrhage (Fig. 3B and D). sity Clinic for Swine, three additional boars with swollen The penis and the accessory sex glands of all necropsied scrota were observed and selected for a detailed diag- boars (n = 5) did not show any gross abnormalities. No nostic work up at the University of Veterinary Medicine puncture wounds were observed or detected, neither in Vienna, Vienna, Austria. Furthermore, ejaculates from the scrotal skin nor in the testicles. six of the affected boars showing various severity of scro- Histopathologic examination revealed complete acute tal swelling and from two boars with no obvious signs of haemorrhagic necrosis of the left testis in three boars scrotal swelling as controls were collected for evaluation (Fig. 4C and D), whereby the left epididymis also showed of sperm morphology. The “control” boars were kept in a complete acute tissue destruction with severe acute the same row, but never showed any signs of enlargement haemorrhages. The wall of the scrotum was highly thick- of the scrotum nor any other clinical signs and therefore ened due to an increased formation of connective tissue were selected as healthy controls. with partly dystrophic calcifications; this was accom- panied by an acute purulent inflammatory reaction as Clinical examination well as a significant oedema and blood congestion. In Clinically, all five examined boars showed mild (n = 1), one boar, only a left-sided oedema of the epididymis and moderate (n = 1) or severe (n = 3) swelling of the left spermatic cord as well as a hydrocele could be detected. scrotum accompanied by hyperaemia of the scrotal skin. The remaining urogenital tract (urinary bladder, kidneys, Three of these boars also presented with a mild swelling accessory sex glands, penis) of the four aforementioned of the right scrota. There were no obvious signs of pain or boars did not show any abnormal histopathology. One discomfort due to the swollen scrota in any of the boars. boar did not have lesions on the urogenital tract or other One Piétrain boar exhibiting scrotal swelling addition- organ systems. ally suffered from grade II lameness on both hind limbs and mild swelling of the tarsal joints. The willingness to Microbiologic investigations mount the phantom was present in all boars, except in Sera from the boars were tested for the presence of anti- the lame Piétrain boar. All other parameters of the clini- Brucella spp. antibodies using Rose-Bengal test and cal examination were in accordance with the physiologi- complement fixation test. Additionally, different organ cal norm (for detailed information see Additional file 1). samples (testes, epididymides and accessory sex glands) were investigated for the presence of cultivable stages Ultrasonographic examination of Brucella spp. All investigations for direct or indirect During ultrasonographic (US) examination of the detection of Brucella were negative. Scrotal aspirates, affected boars (Smart Scan (B), Wireless Vet Ultrasound, testicular tissue, epididymal tissue, tissue of acces- mechanical sector scan, 3.5 MHz, MS Schippers, Bladel, sory sex glands (bulbourethral, prostate and vesicular The Netherlands), the non-affected testes showed a nor- gland) and swabs of the urinary bladder were submit- mal homogenous parenchyma with hyperechoic medi- ted for bacteriological investigation. In addition to bac- astinum and septula of the testis (Fig. 2A). Images of teriological cultivation, PCRs of testicular tissue, scrotal the affected testis demonstrated a non-homogeneous aspirate, epididymal tissue and accessory sex gland Schwarz et al. Porcine Health Management (2023) 9:17 Page 4 of 10 Fig. 2 A Representative transversal ultrasound image of the non-affected testis with homogenous parenchyma and hyperechoic mediastinum from a case of unilateral scrotal swelling. Irregular hypoechoic areas in the lower right corner refer to the opposite site of the swollen scrotum. B and C Representative transversal ultrasound images of the affected testis with slightly inhomogenous parenchyma, thickened-hyperechoic testicular cover and surrounded by multiple, irregular hypoechoic areas with echogenic particles. D Representative ultrasound image of the cauda epididymis corresponding to the affected testis with dilated ductus epididymis tissue for Brucella spp., Leptospira spp., Chlamydia spp., atypical porcine pestivirus), PRRSV, porcine herpes- Glaesserella parasuis and Mycoplasma hyorhinis were viruses (including suid herpes virus 1) and flaviviruses performed. None of the five bacterial pathogens could (including Japanese encephalitis virus) using PCRs. In be detected in any of the animals. Cultivation of testicu- addition to the PCR-based investigations, attempts to lar and epididymal tissue revealed growth of sporadic/ isolate cytopathogenic viruses in an immortalized swine low grade E. coli, low grade Staphylococcus chromogenes, testicle cell line (ST-cells) were performed using serum sporadic Mammaliicoccus sciuri, low grade Streptococcus and tissue of testicles and epididymides. All virological suis and Streptococcus alactolyticus (overview on individ- investigations resulted in negative results. ual results see Additional file 1). The swabs of the urinary bladder also showed low levels of E. coli in three of five Inspection of boar stud and further investigations boars. However, urine of those boars did not exhibit any As the differential list of infectious agents possibly bacterial growth. The cultivation of the scrotal aspirate being involved in the aetiology of the swollen scrota resulted in no detection of cultivable bacteria. and testes was ruled out, the investigative team focused In addition, serological investigations of the examined on non-infectious causes during our on-site facil- boars and two additional animals for Leptospira spp. and ity inspection. To find out possible causes for techno- Chlamydia spp. was performed (Additional file 1), with pathic injuries and traumata, the whole boar stud was no remarkable findings. inspected for corresponding sources (for example, pen construction, facility design, barn equipment, doors, Virological investigations phantom, and semen collection rooms). Employees of All five necropsied boars were investigated for the the boar stud and the herd veterinarian described that presence of specific nucleic acids for African swine nothing was changed regarding the daily routine proce- fever virus, pestiviruses (classical swine fever virus, dures (for example, feeding, semen collection, cleaning Schwarz et al. Porcine Health Management (2023) 9:17 Page 5 of 10 Fig. 3 A High-grade swelling of the left scrotum with opened scrotal wall. Between the testicle and the scrotal wall there are multiple chambers, which were filled with large amounts of serous-bloody fluid and fibrinous tags or incipient adhesions; B Semi-circular incision through left testicle and epididymis. Necrosis of epididymal and testicular tissue with central acute haemorrhage; C High-grade enlargement of the left scrotum. The scrotal wall is open and shows a high degree of thickening due to connective tissue and oedema. The testicle is extensively adnate with the scrotal wall. In the gap between the testicle and the scrotal wall, there is a large amount of serous-bloody fluid and fibrinous tags or incipient adhesions; D Semi-circular incision through the testicle with high-grade, complete, acute haemorrhagic necrosis of barns, handling of boars, etc.) over the past five or maximum content for complete feed (Additional file 2) years. The investigation team could not find any points, [9–11]. neither technically nor procedurally, which would be Evaluation of sperm morphology was done on ejacu- a plausible source for traumata resulting in testicu- lates of four out of five necropsied boars, with abnormal lar swellings. During the team’s presence, handling of sperm morphology ranging from 34.5% to 92% (Addi- boars by animal caretakers and animal technicians dur- tional file 3). Semen was collected by the herd veterinar- ing guidance from the pen to the semen collection cen- ian at the boar stud prior to movement of boars to the tre and back were done very gently without any use of University Clinic for Swine. It was impossible to collect handheld technical devices. semen in the case of the fifth boar (with lameness), there- A commercial dry feed was used at the stud that was fore no semen analysis was conducted. As it was already of consistent feed formulation and was fed to all boars. known from semen analysis done by the responsible herd Given seasonal and regional differences in feed compo- veterinarian that semen quality of all affected boars was nents, it was the only factor that changed over time from not meeting standards to be used in a breeding program, batch to batch. Mycotoxins may have been involved in it was decided not to perform a more complete spermio- the aetiology of the case. Within mycotoxins, especially gram due to financial reasons. zearalenone (ZEN) is known to cause fertility issues in livestock including atrophy of boar´s testes [7]. There- Recommendation to the herd veterinarian fore, a feed sample was analysed for mycotoxins and All investigations regarding infectious and non-infectious survey program (Spectrum 380®) in the Centre for Ana- related metabolites in the framework of DSM mycotoxin causes for swollen scrota resulted in negative outcomes leading to inconclusive results of the investigations. In lytical Chemistry, University of Natural Resources and order to prospectively obtain data in the case of clinical Life Sciences, Vienna [8]. Results showed that mycotoxin sign reoccurrence, the recommendation for the respon- concentrations were below the European guidance level sible herd veterinarian was to install video recording Schwarz et al. Porcine Health Management (2023) 9:17 Page 6 of 10 Fig. 4 A and B Testicular tubules with mature spermatozoa in the lumen, which are partially filled by supporting cells and by cells of spermiogenesis. Leydig cells in the interstitial tissue; C and D Complete necrosis of the entire testicular tissue including the interstitium. Mature spermatozoa are still visible in the centre of some testicular tubules. Scale bar A and C 160 µm; B and D 80 µm cameras for the continuous observation and evaluation described [12, 13]. The purpose of this case report was of the boars’ health, after previously asking for a written to summarize the findings and current evident differen- consent of all employees to fulfil legislative requirements tial diagnoses to offer a scientific base for similar cases in of the Austrian data protection regulation. It was recom- future (Fig. 5). It rather should point out the necessity of mended to install cameras at least in the semen collec- collaboration in science locally and abroad to proceed in tion area and in the corridor of each row of boar pens. gaining knowledge, especially in the case of boar manage- ment. The decision tree in Fig. 5 should give an overview Discussion and conclusion of possible differential diagnoses and may help in similar This case report describes an episodic occurrence of uni- cases in future to clarify the aetiology. lateral/bilateral scrotal swelling in boars of an Austrian Scrotal swelling in boars may have different etiologic boar stud. To the authors’ knowledge, no scientific lit- reasons; it can develop due to infections, but may also erature describes the clinical and the pathologic presen- occur after traumatic injury [14–17]. Creating a list of tation of a group of adult boars exhibiting unilateral and differential diagnoses which may explain such clinical bilateral scrotal swelling. However, single cases have been signs is essential but might be difficult especially in the (See figure on next page.) Fig. 5 An overview and summary of differential diagnoses in case of unilateral enlargement of the scrotum. This decision tree is the base for similar cases in future to make the diagnostic workup of similar cases more systematic and complete. ° A proper clinical examination and knowledge is needed to get not misled from a physiologically sized testis and testis with a reduced size caused by different reasons. * Most frequent causes for scrotal involvement are due to infectious agents of the testicles. However, infection due to ubiquitous pathogenic agents only including the scrotum are possible Schwarz et al. Porcine Health Management (2023) 9:17 Page 7 of 10 Unilateral enlargement of scrotum° Only scrotal Scrotal and testicular involvement involvement Non-infectious Infectious* Non-infectious Infectious Anatomical Anatomical Hydrocele Injury/Trauma abnormalities or Epididymitis Orchitits Injury/Trauma abnormalities or deformities deformities Periorchitis Hydrocele Scrotal hemangioma Brucella suis Brucella suis Spermatocele Inguinal hernia Scrotal abscess Scrotal haematoma Varicocele Rubulavirus Rubulavirus Testicular torsion Testicular neoplasia Scrotal oedema Scrotal oedema Chlamydia spp. Chlamydia spp. Epididymitis Spermatocele Pseudorabies-Virus Pseudorabies-Virus Orchitis Varicocele Leptospira (mild and Leptospira (mild and Scrotal/Testicular temporary) temporary) haematoma Porcine reproductive Porcine reproductive and respiratory and respiratory syndrome Virus syndrome Virus Japanese Encephalitis Pseudomonas Virus pseudomallei Trypanosoma brucei Trueperella pyogenes brucei Mycobacterium Japanese Encephalitis tuberculosis Virus Staphylococcus spp. Trueperella pyogenes Mycobacterium Streptococcus spp. tuberculosis Staphylococcus spp. Streptococcus spp. Fig. 5 (See legend on previous page.) Schwarz et al. Porcine Health Management (2023) 9:17 Page 8 of 10 case of adult boars, as the scientific literature is limited results, the herd veterinarian decided to vaccinate boars [18, 19]. Therefore, personal experience shared by veteri- at this stud against leptospirosis in the future. narians working in boar studs is very valuable in helping During the inspection of the boar stud, sources of to create a robust list of differential diagnoses, especially potential technopathic injuries were evaluated, but since when the issue has barely been tackled in the scientific the daily routine procedure and the housing system did literature. This case report supports this latter statement, not change over at least five years and no obvious sources as only the connection to other researchers and experi- of technopathic injuries were observed by us at our visit, enced people in the field of boars/boar studs and/or the- we can only speculate about the definitive cause of the riogenology led to a complete differential diagnosis list swollen scrota. Animal induced trauma, such as boars where differentials were eliminated, leaving a final pre- scaling the solid pen wall followed by an accidental fall sumptive diagnosis of a blunt force trauma to the affected on the testes due to a slippery floor could be one expla- boars. nation for the swollen scrota. However, neither the floor During the diagnostic workup, it is necessary to care- and/or bedding material were slippery nor was scaling fully evaluate each result and to discuss its plausibility of the solid pen walls by boars observed by any work- and validity. Starting with one of the most plausible dif- ers in the boar stud. During our visit with the boar stud ferential diagnosis—porcine brucellosis—each further employees responsible for taking care of the boars, we differential diagnosis should be excluded step by step. found their interaction with the boars to be very pleasant A long list of differentials leads to high costs, therefore and gentle. This case occurred in 2020 when the global a stepwise diagnostic workup may help keeping costs coronavirus disease 2019 (COVID-19) pandemic started. lower. Rubula virus, which is known to cause testicular In Austria, as in many other countries all over the world, swelling was not investigated, because this viral disease is lockdowns were ordered by the government to reduce only described to occur in central Mexico and has never virus transmission through social distancing. Travelling been reported elsewhere [20]. In the diagnostic workup also became complicated compared to pre-pandemic of this case, we could not definitively identify any infec- times, as in the early phases of the first lockdown in tious or non-infectious agent known to cause scrotal or Austria, expensive PCR tests were needed to travel from testicular swelling in boars, despite the fact that acute one country to another. Workers in the boar stud were inflammatory reactions were observed via histopathol- of multiple ethnicities and have been working there for ogy of the scrotal wall. This finding is believed to be several years. Workers of the boar stud reported that they the consequence of chemo-attraction of neutrophils by were concerned and decided not to visit their homes in necrotic material [21]. Moreover, we even included infec- eastern European countries. This change in the travelling tious agents in the list of differential diagnoses, such as behaviour due to the pandemic situation led to psycho- Glaesserella parasuis and Mycoplasma hyorhinis, which logical distress in many people as recently reported [24, have not been definitively ascribed to scrotal swelling 25]. Mental impairment, such as depression and anxi- outcomes but, through their pathogenesis, may be pos- ety [26], combined with restrictions to public life and/or sible. This was due to the observed caverns filled with independence ordered by the government may have con- blood-tinged fluid in testicles/scrota during necropsy, as tributed to aggressive and frustrated behaviours in boar we could not exclude main polyserositis-causing agents stud workers. The responsible herd veterinarian, who [22] which may have led to fluid and fibrin accumulation was also the owner of the boar stud, reported that farm in the cavum vaginale of testicles/scrota. workers were frustrated at least to a certain degree, as In case of Leptospira microscopic agglutination test- they were isolated from their families and were not able ing (MAT), two boars showed titres against some sero- to visit their homes. vars at one time point. As boars were euthanized and After eliminating other differentials, the pathological no previously sampled sera were available at the time lesions observed in this case most likely were caused by when boars were investigated at the University of Vet- a traumatic event that led to a local hematoma and con- erinary Medicine Vienna, we were not able to conclude secutively to vascularization disorders finally resulting on the relevance of the measured Leptospira antibody in massive fluid accumulation in the cavum vaginale. As titres (1:100–1:200), as MAT is a method primarily devel- the herd veterinarian reported that no animal-induced oped for herd investigations or for investigating acute trauma events (for example, falling off the dummy or infections in single animals in case acute and convales- scaling pen walls) happened during semen collection and cent samples show a four-fold rise [23]. It is unlikely that no sources of technopathies could be detected, we specu- Leptospira spp. were involved in this clinical case, as only late that human mistreatment against boars may have two out of five investigated boars showed any antibody led to blunt traumata. Six out of eight boars were kept titres. Regardless, based on the non-negative Leptospira in pens of one row which had to be re-entered making a Schwarz et al. Porcine Health Management (2023) 9:17 Page 9 of 10 left turn. Before final entry into the pen the left scrotum/ Supplementary Information testicle was exposed. In case the boars may have stolidly The online version contains supplementary material available at https://​doi.​ re-entered, one may speculate that workers may have org/​10.​1186/​s40813-​023-​00313-1. inflicted a physical event to the rear of the boar using Additional file 1. Summary of all clinical and laboratory findings of the an object or body part (for example, feet) to accelerate investigated boars. the re-entry of the boar. Although we know that the lat- Additional file 2. Summary of the mycotoxicologic investigations of feed. ter statement is speculative, it cannot be excluded and Additional file 3. Results of semen analysis of collected semen. should be kept in mind. In case of suspected animal abuse validated, repeatable Acknowledgements and feasible animal-based measures have to be imple- We want to thank the herd veterinarian for involving us in this interesting mented in a farm to guarantee a high level of animal and informative case. We highly appreciate the willingness of the veterinar‑ welfare and to create awareness of animal welfare in all ian together with the workers to start a scientific discussion about such sensitive topics. We also want to thank Johannes Kauffold for his initiative in persons involved in handling of animals [27]. The respon- building the international network in this case with experts in boar health sible herd veterinarian was recommended to install video management. recording cameras for the observation and evaluation Author contributions of boars’ health. He only started the discussion process LS wrote the first draft of the manuscript; LS, SD, VM were involved in the of camera installation for health observation of boars clinical and diagnostic work-up; HW and RB performed pathoanatomic and together with the employees, but decided not to do so, histopathologic investigations; TR and AA performed virologic investiga‑ tions; IL performed microbiologic investigations; IZ performed investiga‑ as the workers were quite irritated and concerned about tions to exclude notifiable diseases especially brucellosis; NR and BBW were being observed. Indeed, such discussions need a high responsible for mycotoxicologic investigations; DS performed andrologic and grade of tactfulness and discretion as it may be evaluated ultrasonographic investigations; GA, CK, JS, ML, PT and AG gave important intellectual input during the diagnostic work-up; LS and AL supervised the by workers as lack of confidence. However, after having case; all authors contributed to write the manuscript and all proof-read the discussions with the workers regarding the process of manuscript. camera installation, no further incidents of unilateral/ Funding bilateral swollen scrota have occurred at this stud to date. This case was conducted under the responsibility of the University Clinic for Due to the fact, that we started to confirm or exclude Swine without any funding. brucellosis as the first suspected diagnosis, we may have Availability of data and materials been misled by infectious causes in our diagnostic work- All data generated or analysed during this case report are included in this up. For the future, practitioners may follow a proper clin- published article or are available as supplementary data. ical examination including available medical data existing in literature about imaging methods such as ultrasonog- Declarations raphy. This might have brought more insights into trau- Ethics approval and consent to participate matic events as a possible cause of scrotal swelling prior Not applicable. to necropsy of boars [28–30]. Including different imag- ing techniques may have resulted in blunt trauma as sus- Consent for publication Not applicable. pected diagnose earlier, which might have enabled us to also investigate blood for break down products of hae- Competing interests moglobin and for iron storage capacity. The authors declare that they have no competing interests. Although our diagnosis was through both gross and Author details histopathologic findings along with differential list exclu- 1 Department for Farm Animals and Veterinary Public Health, University Clinic sion of known causes of unilateral swollen scrota and for Swine, University of Veterinary Medicine Vienna, Vienna, Austria. 2 Depart‑ ment of Pathobiology, Institute of Pathology, University of Veterinary Medicine necrosis of testicles, we think that this case report is very Vienna, Vienna, Austria. 3 Department of Pathobiology, Institute of Virology, important for future similar cases. It will serve both as University of Veterinary Medicine Vienna, Vienna, Austria. 4 Department a guideline for differential diagnoses in case of scrotal of Pathobiology, Institute of Microbiology, University of Veterinary Medicine Vienna, Vienna, Austria. 5 Austrian Agency for Health and Food Safety, Institute swelling and as a base for discussion of the role of pos- for Veterinary Disease Control, Mödling, Austria. 6 DSM Austria GmbH, Getzers‑ sible human misbehaviour in boar studs. dorf, Austria. 7 DSM, BIOMIN Research Center, Tulln an der Donau, Austria. 8 Obstetrics, Gynaecology and Andrology, Department for Companion Animals and Horses, University of Veterinary Medicine Vienna, Vienna, Austria. 9 Depart‑ Abbreviations ment of Clinical Studies‑New Bolton Center, School of Veterinary Medicine, MAT Microscopic agglutination test University of Pennsylvania, Philadelphia, USA. 10 Kuster Research and Consult‑ PCR Polymerase chain reaction ing, Inc., Atkinson, USA. 11 Unitat Mixta d’Investigació IRTA‑UAB en Sanitat PRRSV Porcine reproductive and respiratory syndrome virus Animal, Centre de Recerca en Sanitat Animal (CReSA), and Departament de SARS-CoV-2 South Asian respiratory syndrome coronavirus 2 Sanitat i Anatomia Animals, Facultat de Veterinària, Campus de la Universitat ST-cells Swine testicle cells Autònoma de Barcelona (UAB), 08193 Bellaterra, Catalonia, Spain. 12 Clinic ZEN Zearalenone for Swine, Faculty of Veterinary Medicine, University of Liège, Liège, Belgium. 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In: Zimmerman JJ, Karriker LA, Ramirez A, Schwartz KJ, Stevenson GW, Zhang J, editors. • thorough peer review by experienced researchers in your field Diseases of swine. Hoboken NJ: Wiley Blackwell; 2019. p. 778–91. https://​ • rapid publication on acceptance doi.​org/​10.​1002/​97811​19350​927.​ch50. • support for research data, including large and complex data types 15. Thilmant P, Cassart D, Laitat M. Bilateral scrotal swelling in a boar. In: Proceedings of the 24th IPVS. vol. 374, 2016. • gold Open Access which fosters wider collaboration and increased citations 16. Zheng B, Wang X, Liu Y, Li Y, Long S, Gu C, et al. Japanese Encephalitis • maximum visibility for your research: over 100M website views per year Virus infection induces inflammation of swine testis through RIG-I-NF-ĸB signaling pathway. Vet Microbiol. 2019;238:108430. https://​doi.​org/​10.​ At BMC, research is always in progress. 1016/j.​vetmic.​2019.​108430. 17. Mettenleiter TC, Ehlers B, Müller T, Yoon K-J, Teifke JP. Herpesviruses. Learn more biomedcentral.com/submissions In: Zimmerman JJ, Karriker LA, Ramirez A, Schwartz KJ, Stevenson GW,