Detection of equine herpesvirus type 1 by real time PCR

Clinical impact, diagnosis and control of Equine Herpesvirus-1 infection in Europe

Equine herpesvirus-1 (EHV-1) can affect the entire equine sector in EU, and the large outbreak reported in 2021 in Spain drew attention to the needs of the European Commission for scientific advice for the assessment of EHV-1 infection within the framework of Animal Health Law. EHV-1 is considered endemic in the EU; its main risk is linked to the characteristic of producing latent life-long infections. These can reactivate producing clinical disease, which can include respiratory, abortive and possibly fatal neurological forms. From the epidemiological and genomic viewpoint, there are no specific neuropathogenic EHV-1 strains; the respiratory, reproductive and neurological signs are not found to be strain-specific. This was also the case of the virus that caused the outbreak in Valencia (Spain) in 2021, which was genetically closely related to other viruses circulating before in Europe, and did not present the so-called neuropathogenic genotype. The outbreak reported in Valencia was followed by wide geographic spread of the virus possibly due to a delay in diagnosis and late application of biosecurity measures. The recommended and most sensitive diagnostic test for detecting EHV-1 is PCR performed on swabs collected according to the type of clinical signs. Serological assays on paired blood samples can help to detect a recent infection, while no diagnostic methods are available to detect EHV-1 latent infections. Safe movements of horses can be ensured at premovement phase by testing and issuing health certificates, and by isolating animals upon arrival at new premises with regular health monitoring. In case of suspicion, movements should be forbidden and EHV-1 infection early detected/confirmed by validated diagnostic tools. During outbreaks, no movements should be allowed until 21 days after the detection of the last case. In general, vaccination against EHV-1 should be promoted, although this offers limited protection against the neurological form of the disease.

Viral infection and allergy - What equine immune responses can tell us about disease severity and protection

Horses have many naturally occurring diseases that mimic similar conditions in humans. The ability to conduct environmentally controlled experiments and induced disease studies in a genetically diverse host makes the horse a valuable intermediate model between mouse studies and human clinical trials. This review highlights important similarities in the immune landscape between horses and humans using current research on two equine diseases as examples. First, equine herpesvirus type 1 (EHV-1) infection initiates a series of innate inflammatory signals at its mucosal entry site in the upper respiratory tract. These inflammatory markers are highly synchronized and predictable between individuals during viral respiratory infection and ultimately lead to adaptive immune induction and protection. The timing of early inflammatory signals, followed by specific adaptive immune markers correlating with immunity and protection, allow accurate outbreak tracking and also provide a foundation for understanding the importance of local mucosal immunity during other viral respiratory infections. Second, rare peripheral blood immune cells that promote allergic inflammation can be analyzed during Culicoides hypersensitivity, a naturally occurring type I IgE-mediated allergic disease of horses. Rare immune cells, such as IgE-binding monocytes or basophils, can be studied repeatedly in the horse model to unravel their larger mechanistic role in inflammation during allergic and other inflammatory diseases. We conclude with a survey of all other common equine inflammatory conditions. Together, this review serves as a reference and rationale for the horse as a non-rodent model for immunological research.

Fetal lesions of EHV-1 in equine

EHV-1 infection is responsible for huge economic losses in equines due to abortion and neonatal mortality. In this study, we describe 4 cases of abortion and neonatal deaths from pregnant mares and a she-donkey from different localities in Egypt during the period from May 2015 to October 2017. Attempts were made to isolate and identify EHV-1, in addition to compare the different pathological lesions in various tissues of the necropsied cases. EHV-1 was successfully isolated from two aborted fetuses and one dead neonatal foal from mares, beside one aborted fetus from a she-donkey. The positive cases showed cytopathic effect on embryonated chicken eggs scattered on chorioallantoic membrane. Moreover, PCR was applied for the pock lesions and revealed positive results for EHV-1. Interstitial pneumonia, bronchopneumonia and necrosis of hepatic, myocardial, microcotyledonary tissues besides disseminated thrombi were the main encountered lesions. Intranuclear inclusion bodies were demonstrated in brain, liver, placenta and pulmonary tissues. Here, we describe EHV-1 induced brain lesions represented by degenerated neurons, vascular endotheliosis with intranuclear inclusion bodies in the aborted she-donkey fetus. Lesions were more sever in the aborted fetuses from mares than the one from the she-donkey. EHV-1 antigen was detected by immunohistochemistry staining.

An Equine Herpesvirus Type 1 (EHV-1) Ab4 Open Reading Frame 2 Deletion Mutant Provides Immunity and Protection from EHV-1 Infection and Disease

Equine herpesvirus type 1 (EHV-1) outbreaks continue to occur despite widely used vaccination. Therefore, development of EHV-1 vaccines providing improved immunity and protection is ongoing. Here, an open reading frame 2 deletion mutant of the neuropathogenic EHV-1 strain Ab4 (Ab4ΔORF2) was tested as a vaccine candidate. Three groups of horses (n = 8 each) were infected intranasally with Ab4ΔORF2 or the parent Ab4 virus or were kept as noninfected controls. Horses infected with Ab4ΔORF2 had reduced fever and nasal virus shedding compared to those infected with Ab4 but mounted similar adaptive immunity dominated by antibody responses. Nine months after the initial infection, all horses were challenged intranasally with Ab4. Previously noninfected horses (control/Ab4) displayed clinical signs, shed large amounts of virus, and developed cell-associated viremia. In contrast, 5/8 or 3/8 horses previously infected with Ab4ΔORF2 or Ab4, respectively, were fully protected from challenge infection as indicated by the absence of fever, clinical disease, nasal virus shedding, and viremia. All of these outcomes were significantly reduced in the remaining, partially protected 3/8 (Ab4ΔORF2/Ab4) and 5/8 (Ab4/Ab4) horses. Protected horses had EHV-1-specific IgG4/7 antibodies prior to challenge infection, and intranasal antibodies increased rapidly postchallenge. Intranasal inflammatory markers were not detectable in protected horses but quickly increased in control/Ab4 horses during the first week after infection. Overall, our data suggest that preexisting nasal IgG4/7 antibodies neutralize EHV-1, prevent viral entry, and thereby protect from disease, viral shedding, and cell-associated viremia. In conclusion, improved protection from challenge infection emphasizes further evaluation of Ab4ΔORF2 as a vaccine candidate.IMPORTANCE Nasal equine herpesvirus type 1 (EHV-1) shedding is essential for virus transmission during outbreaks. Cell-associated viremia is a prerequisite for the most severe disease outcomes, abortion and equine herpesvirus myeloencephalopathy (EHM). Thus, protection from viremia is considered essential for preventing EHM. Ab4ΔORF2 vaccination prevented EHV-1 challenge virus replication in the upper respiratory tract in fully protected horses. Consequently, these neither shed virus nor developed cell-associated viremia. Protection from virus shedding and viremia during challenge infection in combination with reduced virulence at the time of vaccination emphasizes ORF2 deletion as a promising modification for generating an improved EHV-1 vaccine. During this challenge infection, full protection was linked to preexisting local and systemic EHV-1-specific antibodies combined with rapidly increasing intranasal IgG4/7 antibodies and lack of nasal type I interferon and chemokine induction. These host immune parameters may constitute markers of protection against EHV-1 and be utilized as indicators for improved vaccine development and informed vaccination strategies.

Intranasal IgG4/7 antibody responses protect horses against equid herpesvirus-1 (EHV-1) infection including nasal virus shedding and cell-associated viremia

Equid herpesvirus-1 (EHV-1) outbreaks continue despite widely used vaccination. We demonstrated previously that an ORF1/ORF71 gene deletion mutant of the EHV-1 strain Ab4 (Ab4ΔORF1/71) is less virulent than its parent Ab4 virus. Here, we describe the Ab4 challenge infection evaluating protection induced by the Ab4ΔORF1/71 vaccine candidate. Susceptible control horses developed respiratory disease, fever, nasal shedding, and viremia. Full protection after challenge infection was observed in 5/5 previously Ab4 infected horses and 3/5 Ab4ΔORF1/71 horses. Two Ab4ΔORF1/71 horses developed short-lasting viremia and/or virus shedding. Protective immunity in the respiratory tract was characterized by pre-existing EHV-1-specific IgG4/7 antibodies, the absence of IFN-α secretion and rapidly increasing IgG4/7 upon challenge infection. Pre-existing systemic EHV-1-specific IgG4/7 highly correlated with protection. T-cell immunity was overall low. In conclusion, protective immunity against EHV-1 infection including prevention of viremia was associated with robust systemic and intranasal IgG4/7 antibodies suggesting immediate virus neutralization at the local site.

The deletion of the ORF1 and ORF71 genes reduces virulence of the neuropathogenic EHV-1 strain Ab4 without compromising host immunity in horses

The equine herpesvirus type 1 (EHV-1) ORF1 and ORF71 genes have immune modulatory effects in vitro. Experimental infection of horses using virus mutants with multiple deletions including ORF1 and ORF71 showed promise as vaccine candidates against EHV-1. Here, the combined effects of ORF1 and ORF71 deletions from the neuropathogenic EHV-1 strain Ab4 on clinical disease and host immune response were further explored. Three groups of EHV-1 naïve horses were experimentally infected with the ORF1/71 gene deletion mutant (Ab4ΔORF1/71), the parent Ab4 strain, or remained uninfected. In comparison to Ab4, horses infected with Ab4ΔORF1/71 did not show the initial high fever peak characteristic of EHV-1 infection. Ab4ΔORF1/71 infection had reduced nasal shedding (1/5 vs. 5/5) and, simultaneously, decreased intranasal interferon (IFN)-α, interleukin (IL)-10 and soluble CD14 secretion. However, Ab4 and Ab4ΔORF1/71 infection resulted in comparable viremia, suggesting these genes do not regulate the infection of the mononuclear cells and subsequent viremia. Intranasal and serum anti-EHV-1 antibodies to Ab4ΔORF1/71 developed slightly slower than those to Ab4. However, beyond day 12 post infection (d12pi) serum antibodies in both virus-infected groups were similar and remained increased until the end of the study (d114pi). EHV-1 immunoglobulin (Ig) G isotype responses were dominated by short-lasting IgG1 and long-lasting IgG4/7 antibodies. The IgG4/7 response closely resembled the total EHV-1 specific antibody response. Ex vivo re-stimulation of PBMC with Ab4 resulted in IFN-γ and IL-10 secretion by cells from both infected groups within two weeks pi. Flow cytometric analysis showed that IFN-γ producing EHV-1-specific T-cells were mainly CD8⁺/IFN-γ⁺ and detectable from d32pi on. Peripheral blood IFN-γ⁺ T-cell percentages were similar in both infected groups, albeit at low frequency (~0.1%). In summary, the Ab4ΔORF1/71 gene deletion mutant is less virulent but induced antibody responses and cellular immunity similar to the parent Ab4 strain.

Deletion of the ORF2 gene of the neuropathogenic equine herpesvirus type 1 strain Ab4 reduces virulence while maintaining strong immunogenicity

BACKGROUND

Equine herpesvirus type 1 (EHV-1) induces respiratory infection, abortion, and neurologic disease with significant impact. Virulence factors contributing to infection and immune evasion are of particular interest. A potential virulence factor of the neuropathogenic EHV-1 strain Ab4 is ORF2. This study on 24 Icelandic horses, 2 to 4 years of age, describes the infection with EHV-1 Ab4, or its deletion mutant devoid of ORF2 (Ab4ΔORF2) compared to non-infected controls (each group n = 8). The horses' clinical presentation, virus shedding, viremia, antibody and cellular immune responses were monitored over 260 days after experimental infection.

RESULTS

Infection with Ab4ΔORF2 reduced fever and minimized nasal virus shedding after infection compared to the parent virus strain Ab4, while Ab4ΔORF2 established viremia similar to Ab4. Concurrently with virus shedding, intranasal cytokine and interferon α (IFN-α) production increased in the Ab4 group, while horses infected with Ab4ΔORF2 expressed less IFN-α. The antibody response to EHV-1 was evaluated by a bead-based multiplex assay and was similar in both infected groups, Ab4 and Ab4ΔORF2. EHV-1 specific immunoglobulin (Ig) G1 was induced 8 days after infection (d8 pi) with a peak on d10-12 pi. EHV-1 specific IgG4/7 increased starting on d10 pi, and remained elevated in serum until the end of the study. The intranasal antibody response to EHV-1 was dominated by the same IgG isotypes and remained elevated in both infected groups until d130 pi. In contrast to the distinct antibody response, no induction of EHV-1 specific T-cells was detectable by flow cytometry after ex vivo re-stimulation of peripheral blood mononuclear cells (PBMC) with EHV-1 in any group. The cellular immune response was characterized by increased secretion of IFN-γ and interleukin10 in response to ex vivo re-stimulation of PBMC with EHV-1. This response was present during the time of viremia (d5-10 pi) and was similar in both infected groups, Ab4 and Ab4ΔORF2.

CONCLUSIONS

ORF2 is a virulence factor of EHV-1 Ab4 with impact on pyrexia and virus shedding from the nasal mucosa. In contrast, ORF2 does not influence viremia. The immunogenicity of the Ab4ΔORF2 and parent Ab4 viruses are identical. Graphical abstract - Deletion of ORF2 reduces virulence of EHV-1 Ab4. Graphical summary of the main findings of this study: ORF2 is a virulence factor of EHV-1 Ab4 with impact on pyrexia and virus shedding from the nasal mucosa.

High mortality in foals associated with Salmonella enterica subsp. enterica Abortusequi infection in Italy

Salmonella enterica subsp. enterica serovar Abortusequi is frequently reported as a cause of abortion in mares and neonatal septicemia and polyarthritis in Asian and African countries, but only sporadically in Europe and the United States. We report an outbreak of S. Abortusequi in foals in Italy, characterized by high mortality. In a herd of Murgese horses, 10 of 34 newborns died at birth and a further 7 died, after developing severe clinical signs, during the first 10 d of life. Tissue specimens from different organs of 2 dead foals, synovial fluids from 4 sick foals, and vaginal and rectal swabs from their dams were cultured. A total of 16 isolates, all as pure cultures, were obtained and identified as Salmonella. The isolates exhibited the same antimicrobial resistance pattern and the same sequence type, ST251, a type that has been associated with S. Abortusequi. Six of 16 isolates were serotyped and found to be S. Abortusequi 4,12:-:e,n,x. Equine practitioners should be aware of S. Abortusequi infection as a cause of neonatal mortality in foals.

Neonatal Immunization with a Single IL-4/Antigen Dose Induces Increased Antibody Responses after Challenge Infection with Equine Herpesvirus Type 1 (EHV-1) at Weanling Age

Neonatal foals respond poorly to conventional vaccines. These vaccines typically target T-helper (Th) cell dependent B-cell activation. However, Th2-cell immunity is impaired in foals during the first three months of life. In contrast, neonatal basophils are potent interleukin-4 (IL-4) producers. The purpose of this study was to develop a novel vaccine triggering the natural capacity of neonatal basophils to secrete IL-4 and to evaluate if vaccination resulted in B-cell activation and antibody production against EHV-1 glycoprotein C (gC). Neonatal vaccination was performed by oral biotinylated IgE (IgE-bio) treatment at birth followed by intramuscular injection of a single dose of streptavidin-conjugated gC/IL-4 fusion protein (Sav-gC/IL-4) for crosslinking of receptor-bound IgE-bio (group 1). Neonates in group 2 received the intramuscular Sav-gC/IL-4 vaccine only. Group 3 remained non-vaccinated at birth. After vaccination, gC antibody production was not detectable. The ability of the vaccine to induce protection was evaluated by an EHV-1 challenge infection after weaning at 7 months of age. Groups 1 and 2 responded to EHV-1 infection with an earlier onset and overall significantly increased anti-gC serum antibody responses compared to control group 3. In addition, group 1 weanlings had a decreased initial fever peak after infection indicating partial protection from EHV-1 infection. This suggested that the neonatal vaccination induced a memory B-cell response at birth that was recalled at weanling age after EHV-1 challenge. In conclusion, early stimulation of neonatal immunity via the innate arm of the immune system can induce partial protection and increased antibody responses against EHV-1.

High-throughput Detection of Respiratory Pathogens in Animal Specimens by Nanoscale PCR

Nanoliter scale real-time PCR uses spatial multiplexing to allow multiple assays to be run in parallel on a single plate without the typical drawbacks of combining reactions together. We designed and evaluated a panel based on this principle to rapidly identify the presence of common disease agents in dogs and horses with acute respiratory illness. This manuscript describes a nanoscale diagnostic PCR workflow for sample preparation, amplification, and analysis of target pathogen sequences, focusing on procedures that are different from microliter scale reactions. In the respiratory panel presented, 18 assays were each set up in triplicate, accommodating up to 48 samples per plate. A universal extraction and pre-amplification workflow was optimized for high-throughput sample preparation to accommodate multiple matrices and DNA and RNA based pathogens. Representative data are presented for one RNA target (influenza A matrix) and one DNA target (equine herpesvirus 1). The ability to quickly and accurately test for a comprehensive, syndrome-based group of pathogens is a valuable tool for improving efficiency and ergonomics of diagnostic testing and for acute respiratory disease diagnosis and management.

Respiratory Disease: Diagnostic Approaches in the Horse

Evaluation of the upper and lower respiratory tract of horses requires strategic selection of possible diagnostic tests based on location of suspected pathologic lesions and purpose of testing and must also include consideration of patient status. This article discusses the various diagnostic modalities that may be applied to the respiratory system of horses under field conditions, indications for use, and aspects of sample collection, handling, and laboratory processing that can impact test results and ultimately a successful diagnosis in cases of respiratory disease.

Comparison of four methods to quantify Equid herpesvirus 1 load by real-time polymerase chain reaction in nasal secretions of experimentally and naturally infected horses

The objective of the current study was to compare the performance of 4 methods to quantify Equid herpesvirus 1 (EHV-1) by real-time polymerase chain reaction (PCR) in nasal secretions from experimentally and naturally infected horses. Nasal secretions were collected on the challenge day and daily thereafter for 13 days from 4 experimentally infected horses. Additional nasal swabs were collected from 30 horses with clinical signs consistent with natural EHV-1 infection. Absolute quantitation of EHV-1 target molecules was performed using standard curves for EHV-1 and equine glyceraldehyde-3-phosphate dehydrogenase, and DNA yield, and was expressed as EHV-1 glycoprotein B (gB) gene copies per million nucleated nasal cells, EHV-1 gB gene copies per entire swab, EHV-1 gB gene copies per 1 microl of purified DNA, and EHV-1 gB gene copies per 1 ng of template DNA. The study results showed that all 4 calculation methods yielded comparable results between experimentally and naturally infected horses, and that the different methods were significantly correlated with each other. Reporting of quantitative results for EHV-1 viral load in nasal swabs collected from infected horses constitutes an important advance in both the research and diagnostic fields, allowing one to determine the infectious risk of affected horses, disease stage, or response to antiviral therapy. However, protocols that normalize the PCR results against a preselected volume of DNA or nasal secretions are likely to be more prone to variations than protocols that calculate the load for the entire swab, incorporate a housekeeping gene, or use a constant amount of extracted DNA.

Meningoencephalitis in a Polar Bear Caused by Equine Herpesvirus 9 (EHV-9)

A 12-year-old female polar bear ( Ursus maritimus) developed a sudden onset of muscle tremors, erratic circling, increased blinking, head shaking, and ptyalism, which progressed to partial and generalized seizures. Ancillary diagnostic tests were inconclusive, and the only significant laboratory finding was nonsuppurative pleocytosis of cerebrospinal fluid. Euthanasia was elected. Microscopic evaluation demonstrated multifocal, random nonsuppurative meningoencephalitis involving most prominently the rostral cerebral cortex, as well as the thalamus, midbrain, and rostral medulla. Lesions consisted of inflammation, neuronal necrosis, gliosis, and both neuronal and glial basophilic intranuclear inclusion bodies. Immunohistochemistry with a polyclonal antibody reactive to several equine herpesviruses was positive within affected areas of the brain, and polymerase chain reaction conclusively demonstrated the presence of only equine herpesvirus 9. The clinical and morphologic features of this case resemble other fatal herpesvirus encephalitides derived from interspecies transmission and underscore the need for extreme caution when managing wild or captive equids.

Equine herpesvirus-1 myeloencephalopathy: a review of recent developments

Equine herpes myeloencephalopathy (EHM), although a relatively uncommon manifestation of equine herpesvirus-1 (EHV-1) infection, can cause devastating losses on individual farms or boarding stables. Although outbreaks of EHM have been recognized for centuries in domestic horse populations, many aspects of this disease remained poorly characterized. In recent years, an improved understanding of EHM has emerged from experimental studies and from data collected during field outbreaks at riding schools, racetracks and veterinary hospitals throughout North America and Europe. These outbreaks have highlighted the contagious nature of EHV-1 and have prompted a re-evaluation of diagnostic procedures, treatment modalities, preventative measures and biosecurity protocols for the disease. This review concentrates on these and other selected, clinically relevant aspects of EHM.

Duplex Real-Time Polymerase Chain Reaction for Simultaneous Detection and Quantification of Anaplasma Marginale and Anaplasma Centrale

Anaplasma marginale and Anaplasma centrale are rickettsial pathogens responsible for acute disease and mild infections, respectively, in cattle herds. A duplex real-time polymerase chain reaction (PCR) assay with probes labeled with different fluorophores was developed for simultaneous detection and quantification of A. marginale and A. centrale DNA in bovine blood samples. The assay was able to detect as few as 101 and 102 DNA copies for A. marginale and A. centrale, respectively, with optimal specificity and reproducibility. Analysis by real-time and nested PCR carried out on 54 samples previously tested by reverse line blot hybridization showed that the established duplex real-time PCR assay can detect and quantify the 2 Anaplasma spp., even if present simultaneously in the same blood samples. Such an assay could be used in pathogenesis studies on bovine acute anaplasmosis.

Detection of equine herpesvirus-1 in nasal swabs of horses by quantitative real-time PCR

BACKGROUND

Early identification of inhalation-transmitted equine herpesvirus type 1 (EHV-1) infections has been facilitated by the availability of a number of real-time quantitative PCR (qPCR) tests. A direct comparison between nasal swab qPCR and traditional virus isolation (VI) requires a method for normalizing the qPCR samples and controlling for PCR inhibitors present in some clinical samples.

OBJECTIVES

To quantify EHV-1 shedding in viral swabs using an internal control and to compare fast qPCR to VI for the detection of EHV-1 in nasal swabs from horses.

ANIMALS

Fifteen horses experimentally infected with EHV-1.

METHODS

Experimental study: Nasal swab samples were collected daily after experimental infection for up to 21 days. VI was performed by conventional methods. The DNA was prepared for qPCR with the addition of a known quantity DNA of Marek's disease virus as an internal control. qPCR was performed.

RESULTS

The qPCR method detected virus up to day 21 after challenge, whereas VI detected virus only to day 5. The median Kaplan-Meier estimates for EHV-1 detection were 12 days for qPCR and 2 days for VI (P< .0001). When compared with VI, the sensitivity and specificity of qPCR were 97 (95% CI: 86-100) and 27% (95% CI: 20-35).

CONCLUSIONS AND CLINICAL IMPORTANCE

We conclude that fast qPCR of nasal swab samples should be chosen for diagnosis and monitoring of herpesvirus-induced disease in horses. Recommended reference ranges of C(T) values are provided as well as justification of a minimum 10-day quarantine period.

Detection of equine herpesviruses in aborted foetuses by consensus PCR

The major role of EHV-1 in equine abortion is widely reported in the literature but the contribution of EHV-2, EHV-3, EHV-4 or EHV-5 remains less well documented. The objective of this study is to evaluate the contribution of these five different EHVs to equine abortion in a variety of biological tissues using a consensus polymerase chain reaction (PCR). The test was validated for specificity and sensitivity in horses before screening specimens from 407 foetuses, stillbirths and premature foals collected over a 2.5-year interval. Positive results obtained with this assay were compared to other EHV type-specific PCR or by sequencing. EHV-1 was identified as the major cause of abortion in French mares (59/407 cases). However, there was evidence to suggest some variation in the potential of EHV-1 strains to induce abortion. Indeed, DNA samples from EHV-2 (in three cases) and EHV-5 (in one case) inferred a role of these viruses in abortion. The presence of viral DNA from EHV-3 or EHV-4 strains was not detected in the specimens studied. The data obtained suggest that the consensus herpesvirus PCR is an efficient screening tool. In association with a specific PCR, the test provides a rapid identification of the type of herpesvirus involved in abortion and is useful for routine diagnostic tests as it allows the identification of herpesviruses other than the EHV-1 strain.

Equine multinodular pulmonary fibrosis: a newly recognized herpesvirus-associated fibrotic lung disease

Pulmonary fibrosis and interstitial lung disease are poorly understood in horses; the causes of such conditions are rarely identified. Equine herpesvirus 5 (EHV-5) is a gamma-herpesvirus of horses that has not been associated with disease in horses. Pathologic and virologic findings from 24 horses with progressive nodular fibrotic lung disease associated with EHV-5 infection are described and compared with 23 age-matched control animals. Gross lesions consisted of multiple nodules of fibrosis throughout the lungs. Histologically, there was marked interstitial fibrosis, often with preservation of an "alveolar-like" architecture, lined by cuboidal epithelial cells. The airways contained primarily neutrophils and macrophages. Rare macrophages contained large eosinophilic intranuclear viral inclusion bodies; similar inclusion bodies were also found cytologically. The inclusions were identified as herpesviral-like particles by transmission electron microscopy in a single horse. In situ hybridization was used to detect EHV-5 nucleic acids within occasional macrophage nuclei. With polymerase chain reaction (PCR), the herpesviral DNA polymerase gene was detected in 19/24 (79.2%) of affected horses and 2/23 (8.7%) of the control horses. Virus genera-specific PCR was used to detect EHV-5 in all of the affected horses and none of the control horses. EHV-2 was detected in 8/24 (33.3%) of affected horses and 1/9 (11.1%) of the control horses. This disease has not been reported before, and the authors propose that based upon the characteristic gross and histologic findings, the disease be known as equine multinodular pulmonary fibrosis. Further, we propose that this newly described disease develops in association with infection by the equine gamma-herpesvirus, EHV-5.

Detection and quantification of Anaplasma marginale DNA in blood samples of cattle by real-time PCR

A TaqMan-based real-time PCR assay was developed for the diagnosis of Anaplasma marginale infection of cattle. The established assay was proven to be highly specific, since no cross-reactions were observed with other Anaplasma species of ruminants, including the closely related Anaplasma centrale, or other haemoparasites of ruminants (Anaplasma bovis, Anaplasma ovis, Anaplasma phagocytophilum, Babesia bovis, Babesia bigemina, Theileria annulata and Theileria buffeli). The detection limit was equal to that of nested (n)PCR (10(1) copies of standard DNA and 3 x 10(1) infected erythrocytes ml(-1) of blood). The assay was also reproducible, as shown by satisfactory low intra-assay and inter-assay coefficients of variation. Fifty-four blood samples of ruminants (cattle, n = 51; sheep, n = 2; goats, n = 1), that had been tested previously by reverse line blot (RLB) hybridisation, were subjected to an nPCR assay and the newly established real-time PCR assay. By using real-time PCR, A. marginale DNA was detected in 39/51 bovine samples, with DNA titres ranging from 3.60 x 10(3) to 5.70 x 10(8) copies ml(-1) of blood, whereas sheep and goat samples tested negative. The concordance with nPCR was 100%, whereas a unique sample that had tested negative by RLB gave positive results by nPCR and real-time PCR. The established assay could overcome the limitations of existing diagnostic methods, allowing for simultaneous detection and quantification of the A. marginale DNA in bovine blood, that is essential to support the clinical diagnosis, to assess the carrier status of the animals and to evaluate the efficacy of vaccines and antirickettsial drugs.