Equine Herpesvirus 2-Associated Granulomatous Dermatitis in a Horse

Generalized sarcoidosis associated with hypertrophic osteopathy in a Standardbred racehorse

A Standardbred racehorse was presented for exercise intolerance, weight loss, pyrexia and facial deformity. Radiography and ultrasonography revealed periostitis and regional soft tissue swelling of maxillary bones. Computed tomography excluded any dental or sinus origin of these abnormalities. Further deformities on distal limbs and skin lesions appeared during hospitalization. Radiography identified bilateral periostitis and soft tissue swelling in the distal radius and metatarsal bones, as observed in the head, suggestive of hypertrophic osteopathy (HO). Skin biopsies revealed granulomatous dermatitis, indicating equine sarcoidosis (ES). The horse was euthanized due to rapid deterioration of his condition. Post-mortem examination and histopathology revealed splenomegaly, several pulmonary nodules and disseminated granulomatous lesions. These findings confirmed the diagnosis of generalized ES, or equine idiopathic systemic granulomatous disease. The concurrent with HO was probably associated with the intrathoracic pathology. Polymerase chain reaction (PCR) on pooled tissues identified equine herpesvirus 5 (EHV-5) DNA.

Association of equine gammaherpesvirus-5 with facial lymphohistiocytic interface dermatitis in seven adult horses from the United States

Equine herpesvirus-5 (EHV-5) is commonly found in healthy asymptomatic horses worldwide. Although a cause-and-effect relationship has not been thoroughly determined, this virus has been associated with several disease conditions including equine multinodular pulmonary fibrosis (EMPF) and 1 case of interface dermatitis. The authors searched the New York State Animal Health Diagnostic Center database for cases of equine interface dermatitis between 2007 and 2022. Ten cases were identified and scrutinized for viral inclusion bodies which were present in 5 of 10 cases. Two similar cases with interface dermatitis and viral inclusion bodies, which were not part of a retrospective search, were from the Oregon Veterinary Diagnostic Laboratory. The authors describe a total of 7 horses with dermatitis characterized by crusted, alopecic, non-pruritic, non-painful, irregular to annular areas over the face, most commonly the muzzle, for up to several years duration. Histologically, there was a CD3+ T lymphocyte-dominated lymphohistiocytic interface dermatitis with hydropic degeneration, apoptotic keratinocytes, and pigmentary incontinence. Keratinocytes within the upper stratum spinosum and stratum granulosum had glassy pale basophilic intranuclear inclusion bodies consistent with herpesvirus. The presence of EHV-5 was confirmed by quantitative polymerase chain reaction (qPCR) and in situ hybridization in 7 horses and by electron microscopy in 1 horse. One horse later developed EMPF and was euthanized. EHV-5 was not detected with qPCR from 5 control horses and 5 horses with interface dermatitis without histologic evidence of viral inclusion bodies. These are the first cases of facial interface dermatitis associated with EHV-5 reported in the United States.

Potential outbreak by herpesvirus in equines: detection, clinical, and genetic analysis of equid gammaherpesvirus 2 (EHV-2)

BACKGROUND

Equid herpesvirus (EHV) commonly affects horses causing neurologic and respiratory symptoms beside spontaneous abortions, meaning huge economic losses for equine industry worldwide. In foals, the virus can facilitate secondary infections by Rhodococcus equi, important in morbidity and mortality in equines. A total of five genotypes of EHV were previously described in Brazil including EHV-1, EHV-2, EHV-3, EHV-4, and EHV-5. EHV-2 genotype had only been previously described in Brazil in asymptomatic animals. We report the investigation of the dead of 11 foals in Middle-west region of Brazil showing respiratory and neurological symptoms, as well as several abortions in mares from the same farm.

METHODS

Clinical and laboratory exams were performed in this case study. Lung, whole blood, serum, and plasma samples were analyzed by necroscopic and histopathologic techniques followed by molecular assays (conventional and qPCR and Sanger sequencing).

RESULTS AND CONCLUSION

Laboratory exams revealed neutrophilia leukocytosis. Necroscopic and histopathologic findings were suppurative bronchopneumonia and ulcerative enteritis. Molecular assays point to the absence of the bacteria Rhodococcus equi and other viruses (including other EHV). The presence of EHV-2 DNA was confirmed by sequencing in serum sample from one foal. This is the first confirmed outbreak of EHV-2 causing disease in Brazilian horses with confirmed presence of the virus, and which highlight the important role of EHV-2 in equine respiratory disease and spontaneous abortions in equid in Brazil.

Equine Idiopathic Systemic Granulomatous Disease With Manifestation in the Cerebellum Associated With Equid Gammaherpesvirus 2

Idiopathic systemic granulomatous disease (ISGD), also known as equine sarcoidosis is an uncommon disease of horses, manifesting in exfoliative dermatitis and granulomatous inflammation in various organs. The current report presents a case of a 15-year-old Hanoverian mare with a 4-month history of weight loss, recurrent fever, skin lesions, and movement disorders. Pathological examination revealed granulomatous and necrotizing inflammation in the skin, regional lymph nodes, and cerebellum. Based on histological, immunohistochemical, and microbiological findings, the diagnosis of ISGD was made. Sequencing of the polymerase chain reaction product of pooled brain tissue revealed the presence of equid gammaherpesvirus 2 DNA. This case is the first description of generalized ISGD with granulomatous dermatitis simultaneously affecting the skin and cerebellum.

Equine herpesvirus 1-associated ulcerative dermatitis in a horse

This case report describes the clinical and histopathological findings of an infection caused by equine herpesvirus-1 (EHV-1) in a horse showing respiratory signs and a papular, crusted and ulcerative dermatitis involving mucosae. This diagnosis was supported by real-time PCR positive for EHV-1 on nasal swabs and tissues.

Gammaherpesvirus infections in equids: a review

Although the first equine gammaherpesvirus was identified over 50 years ago, the isolation and characterization of other members of this virus group has been relatively recent. Even so, numerous clinical syndromes have been identified in equid species in association with these viruses. Equid gammaherpesviruses are a genetically heterogeneous viral subfamily, the function of which in host immune modulation and disease pathogenesis has not yet been elucidated. While they share similarities with gammaherpesviruses in humans, the role they play in their relationship with the host is the subject of continued interest and research. Their widespread presence in horses and other equid species provides a considerable challenge in linking them with particular clinical and pathological conditions and in defining their significance from a diagnostic and therapeutic viewpoint. The present review provides an update on the taxonomy, epidemiology, and clinical syndromes, especially respiratory, reported in association with gammaherpesvirus infection in horses, donkeys, and other equid species.

Detection of Equid herpesvirus type 2 and 5 DNA in uterine flushings of mares with reproductive disorders

In recent years, there has been increasing evidence of the potential pathogenic significance of equine gammaherpesviruses in the horse. In humans, cattle and mice, gammaherpesviruses have already been associated with uterine infection. The aim of the present study was to investigate the presence of gammaherpesviruses in uterine flushings of mares with reproductive problems and to evaluate if there was a possible statistical association with clinical and laboratory findings in these cases. A total of 80 uterine flushings were collected from 61 mares with different reproductive problems and these were tested for equine herpesviruses (EHV) 1-5 by PCR. In the case of each mare in the study, the age, history of infertility, presence of anatomical defects in the reproductive tract, presence of systemic or local disease at time of sampling, phase in the oestrous cycle, post-partum interval, nature of uterine lavage performed (low versus large volume lavage), cytological and bacteriological examination results from the uterine flushing, and PCR herpesvirus results were recorded. Univariate analysis and multivariable logistic regression models were used to identify possible statistical associations and risk factors. Nine out of 61 mares (14.7%) had EHV-5 DNA in their uterine flushings. Co-infections with EHV-1 and EHV-2 were present in two cases. Of all the variables analyzed, only the cytological examination findings were associated with EHV-5 PCR positive results, both on univariate and multivariable analysis, especially in cases with an inflammation score of 3. It is postulated that presence of EHV-5 infection in the non-pregnant uterus may have a role to play in reproductive dysfunction and have a negative consequence on the pregnant uterus. Additional studies involving both healthy mares and mares with reproductive problems need to be performed, however, to elucidate whatever role equine gammaherpesviruses may play in the reproductive tract. This would be very worthwhile, since reproductive problems can have a significant impact on the equine breeding industry. Gaining a greater understanding of its causes could lead to new approaches for prevention and treatment.

Equine gammaherpesviruses: perfect parasites?

The evolutionary success of the equine gammaherpesviruses (GHVs) is demonstrated by their consistent and widespread presence in horse populations worldwide. Equine GHVs establish infection in young foals and can be continually detected over the lifetime of the host either by recrudescence of latent infections or by re-infection. A definitive diagnosis of clinical disease in horses due to GHV infection remains challenging given the ubiquitous nature of the GHVs in horses without clinical signs, as well as in horses with clinical signs ranging from mild respiratory disease to severe equine multinodular pulmonary fibrosis. This review aims to examine what is known about equine GHV and explore the balance of the relationship that has evolved over millions of years between these viruses and their host.

Pyogranulomatous lesion causing neurological signs localised to the sacral region in a horse

This case report describes neurological signs associated with a pyogranulomatous lesion within the sacral vertebral canal of a horse. The clinical findings included urinary overflow incontinence and reduced anal, perianal and tail tone. The horse failed to respond to medical management and a guarded prognosis for return to athletic performance initiated the decision for euthanasia.

Genetic diversity of equine gammaherpesviruses (γ-EHV) and isolation of a syncytium forming EHV-2 strain from a horse in Iceland

The horse population in Iceland is a special breed, isolated from other equines for at least one thousand years. This provides an exceptional opportunity to investigate old and new pathogens in a genetically closed herd. Both types of equine gammaherpesviruses, EHV-2 and EHV-5, are common in Iceland. Genetic variation was examined by sequencing four genes, glycoprotein B (gB), glycoprotein H (gH), DNA polymerase and DNA terminase for 12 Icelandic and seven foreign EHV-2 strains. One Icelandic virus isolate, gEHV-Dv, induced syncytium formation, an uncharacteristic cytopathy for EHV-2 in equine kidney cells. When sequenced, the glycoprotein genes were different from both EHV-2 and EHV-5, but the polymerase and terminase genes had 98-99% identity to EHV-2. Therefore the gEHV-Dv strain can be considered a variant of EHV-2. Substantial genetic variability was seen within the EHV-2 glycoprotein genes but limited in the polymerase and terminase genes. The Icelandic EHV-2 strains do not seem to differ phylogenetically from the foreign viruses, despite isolation for over a thousand years.

Mycobacterium DNA detection in liver and skin of a horse with generalized sarcoidosis

Sarcoidosis is a rare equine skin disease characterized primarily by an exfoliative and granulomatous dermatitis but also presenting granulomatous inflammation of multiple systems. The current report presents the clinical and histopathological findings of sarcoidosis in a 16-year-old American Quarter Horse gelding with nested polymerase chain reaction Mycobacterium spp. DNA detection within hepatic and skin samples. Mycobacterium spp. may play a role in the pathogenesis of equine sarcoidosis as has been proposed for human sarcoidosis.

Equine gammaherpesviruses: pathogenesis, epidemiology and diagnosis

Equine gammaherpesviruses (γEHV) have been widely studied over the past 45 years and many isolates have been characterised. Despite this, the diagnosis of γEHV infection remains difficult to establish as its clinical manifestations lack specificity, ranging from mild respiratory signs in a small number of animals to outbreaks in large groups of young horses. This review focuses on the epidemiology, pathogenesis, clinical manifestations and diagnosis of equine herpesvirus (EHV)-2 and -5 infections, as well as on the genetic variation of these viruses. Study of these variations has resulted in hypotheses relating to viral re-infection and re-activation. Interestingly, the viruses were found to contain genetic sequences identical to those of eukaryotic cells which are considered central to the development of viral latency through interfering with host immune and inflammatory responses. Future molecular biological studies will further elucidate the virulence mechanisms of these equine pathogens.

Lack of detectable equine herpesviruses 1 and 2 in paraffin-embedded specimens of equine sarcoidosis

BACKGROUND

Equine sarcoidosis is a rare, multisystemic, noncaseating, granulomatous and lymphoplasmacytic disease of unknown etiology. A recent report described a horse with granulomatous skin disease displaying histologic, electron microscopic, and polymerase chain reaction (PCR) findings consistent with equine herpesvirus 2 (EHV-2).

OBJECTIVE

To investigate the presence of EHV-2 and equine herpesvirus 1 (EHV-1) in 8 horses with sarcoidosis.

ANIMALS

Eight horses with sarcoidosis, reported previously.

METHODS

Retrospective study. PCR assays of the tissues were performed to detect DNA associated with EHV-1 and EHV-2. For both herpesviruses the target was their respective glycoprotein B gene. Positive controls consisted of DNA from viral cultures of culturettes from naturally occurring respiratory infections of EHV-1 and EHV-2.

RESULTS

The PCR analyses for both equine herpesviruses' DNA were negative in all 8 horses.

CONCLUSION

The failure to detect DNA from EHV-1 and EHV-2 in paraffin-embedded skin of these 8 horses does not discount EHV-1 or EHV-2 as causing some cases of ES, but lends support to the presumably multifactorial etiologic nature of the disease.

Prevalence, number and morphological types of multinucleated histiocytic giant cells in equine inflammatory dermatoses: a retrospective light microscopic study of skin-biopsy specimens from 362 horses

REASONS FOR PERFORMING STUDY

Multinucleated histiocytic giant cells (MHGC) are seen frequently in skin-biopsy specimens from horses with inflammatory dermatoses. However, the prevalence, number and morphological types of these cells have not been reported.

OBJECTIVE

To determine the prevalence, number and morphological types of MHGC in equine inflammatory dermatoses, and the association of these cells with specific conditions.

METHODS

Skin-biopsy specimens from 335 horses with inflammatory dermatoses and from 27 horses with normal skin were evaluated for the prevalence, number and morphological types of MHGC.

RESULTS

The prevalence and number of MHGC were greater in granulomatous dermatoses than in nongranulomatous dermatoses. Infectious and noninfectious dermatoses were not different in terms of prevalence or morphological types of MHGC. Foreign-body MHGC were the predominant type in almost all cases. MHGC were not seen in normal skin.

CONCLUSIONS

MHGC are seen in a wide variety of equine inflammatory dermatoses, especially those that are granulomatous. Number and morphological types of MHGC are of no apparent diagnostic significance.

POTENTIAL RELEVANCE

MHGC are frequently present in a wide variety of inflammatory dermatoses in the horse. Because the prevalence, number and morphological types of MHGC are of minimal diagnostic significance, special stains and tissue cultures are necessary to confirm specific diagnoses.

Equid Herpesvirus 2-Associated Oral and Esophageal Ulceration in a Foal

A case of a 1-month-old Thoroughbred foal with dysphagia, salivation, pyrexia, oral mucosal pustules, and esophageal ulceration is reported. Swabs from the ulcerated lesions yielded Equid herpesvirus 2 (EHV-2) in virus isolation assays, and histopathology of a biopsy from the esophageal lesion identified nuclear inclusions suggestive of herpesviruses. Immunohistochemical staining with antibodies specific for EHV-2 was positive for epithelial cells in the vicinity of the ulcer but not in more distant mucosa. Electron microscopic evaluation of the biopsy showed herpesviral particles in epithelial cells. The foal recovered over 5 days of supportive and gastroprotective therapy, and the esophageal ulcers healed. Serology and immunohistochemistry indicated that this foal likely had lesions associated with EHV-2 and not EHV-1, −4, or −5.

Study of equid herpesviruses 2 and 5 in Iceland with a type-specific polymerase chain reaction

The horse population in Iceland is a special breed, isolated from other horses for at least 1000 years. This provides an exceptional opportunity to investigate old and new pathogens in an inbred herd with few infectious diseases. We have developed a high sensitivity semi-nested PCR to study equid gammaherpesviruses 2 and 5 (EHV-2 and 5) in Iceland. The first PCR is group specific, the second type-specific, targeting a 113bp sequence in the glyB gene. DNA isolated from white blood cells and 18 different organs was tested for the presence of EHV-2 and 5. This was done in adult horses and foals, healthy and with various enteric infections. Both virus types were easily detected in all types of organs tested or EHV-2 in 79% cases and EHV-5 in 63%. In DNA from PBMC or buffy-coat EHV-2 was found in 20% cases and EHV-5 in 10%, all except one positive were foals. Co-culture of PBMC on fetal horse kidney cells was efficient for detecting EHV-2 but not for EHV-5. We verify here for the first time infections with EHV-2 and 5 in horses in Iceland and show that both viruses are common.

Isolation of a gammaherpesvirus similar to asinine herpesvirus-2 (AHV-2) from a mule and a survey of mules and donkeys for AHV-2 infection by real-time PCR

Equids are commonly infected by herpesviruses, but isolation of herpesviruses from mules has apparently not been previously reported. Furthermore, the genomic relationships among the various equid herpesviruses are poorly characterized. We describe the isolation and preliminary characterization of a mule gammaherpesvirus tentatively identified as asinine herpesvirus-2 (AHV-2; also designated equid herpesvirus-7 (EHV-7)) from the nasal secretions (NS) of a healthy mule in northern California. The virus was initially identified by transmission electron microscopic examination of lysates of cell culture inoculated with NS collected from the mule. A 913 nucleotide sequence of the DNA polymerase gene was amplified using degenerate primers, and comparison of this sequence with those of various other herpesviruses showed that the mule herpesvirus was most closely related to EHV-2 (AHV-2 sequences were not available for comparison). The sequence of a shorter portion (166 nucleotides) of the mule herpesvirus DNA polymerase gene was identical to that of the published sequence of an asinine gammaherpesvirus, previously designated as AHV-4-3 (AY054992). AHV-2 was detected by real-time polymerase chain reaction assay in the NS of approximately 8% of a cohort of 114 healthy mules and 13 donkeys.