An unusual outbreak of malignant catarrhal fever in a beef herd in Israel

Identification of gammaherpesvirus infection in free-ranging black bears (Ursus americanus)

Herpesvirus infection was investigated in black bears (Ursus americanus) with neurological signs and brain lesions of nonsuppurative encephalitis of unknown cause. Visible cytopathic effects (CPE) could only be observed on days 3-5 post-infection in HrT-18G cell line inoculated with bear tissue extracts. The observed CPE in HrT-18G cells included syncytia, intranuclear inclusions, and cell detachments seen in herpesvirus infection in vitro. Herpesvirus-like particles were observed in viral culture supernatant under the electron microscope, however, capsids ranging from 60 nm to 100 nm in size were often observed in viral cultures within the first two passages of propagation. Herpesvirus infection in the bear tissues and tissue cultures were detected by PCR using degenerate primers specific to the DNA polymerase gene (DPOL) and glycoprotein B gene (gB). DNA sequencing of the amplicon revealed that the detected herpesvirus has 94-95% identity to Ursid gammaherpesvirus 1 (UrHV-1) DNA sequences of DPOL. Phylogenetic analysis of DPOL sequences indicates that black bear herpesviruses and UrHV-1 are closely related and have small distances to members of Rhadinovirus. Interestingly, black bear herpesvirus infections were also found in bears without neurological signs. The DPOL DNA sequence of black bear herpesviruses detected in neurological bears were similar to the those detected in the non-neurological bears. However, the gB DNA sequence detected from the neurological bear is different from non-neurological bear and has only 64.5%-70% identity to each other. It is possible that at least two different types of gammaherpesviruses are present in the U. americanus population or several gammaherpesviruses exist in ursine species.

Cross-sectional study indicates nearly a quarter of sheep population in Karnataka state of India is infected with ovine herpesvirus 2

In a cross-sectional study, prevalence of ovine herpesvirus 2 (family: Herpesviridae, subfamily: Gammaherpesvirinae, genus Macavirus and species: Ovine herpesvirus 2) infection was estimated in sheep population of Karnataka state in India. Based on the three stage cluster sampling method, whole blood samples (356) of sheep were collected from 11 sheep-dense districts of the state. The samples were tested for presence of OvHV-2 genome by recommended hemi-nested polymerase chain reaction (PCR) test. The true prevalence of OvHV-2 infection in sheep population of Karnataka was 24.44 %. Of the 11 district surveyed, highest true prevalence of 42.42 % (CI 25.56-59.29) was found in Raichur followed by Tumkur (39.02 %, CI 24.09-53.96). Inverse distance weighted interpolation of prevalence indicated that OvHV-2 prevalence within a given district is not uniform and there are areas of varied prevalence. The nucleotide sequence of the 422 bp DNA fragment, amplified in PCR, matched 99 % with OvHV-2 reference sequence and other sequences reported from India. Grouping of OvHV-2 sequences obtained from Karnataka with those from Andhra Pradesh, Tamil Nadu and Jammu and Kashmir in the neighbour joining tree indicated a close relationship among the OvHV-2s circulating in India. This is the first study in the country where systematic screening of sheep population of a state for the presence of OvHV-2 infection has been carried out, which indicated a widespread prevalence calling for an urgent need for policy measures to prevent economic losses due to the disease in susceptible cattle and buffalo species.

Serological survey to determine the occurrence of malignant catarrhal fever infection in the Japanese small ruminant population from northern districts

Ovine herpesvirus 2 (OvHV-2) causes sheep-associated malignant catarrhal fever (SA-MCF), and is responsible for economic losses in cattle and other susceptible species around the world. A survey of 154 serum samples from 14 flocks in 3 Japanese prefectures (Hokkaido, Aomori and Iwate) was undertaken between 2007 and 2008 to test for antibodies to OvHV-2. OvHV-2 was present in 56 sheep and 2 goats, with 37.66% of samples having a positive reaction using a serum neutralization test. The immune reaction reported in goats could result from Caprine herpesvirus-2. These results indicate that sheep are reservoirs for OvHV-2 in the field in Japan, and they might transmit the virus to susceptible cattle and wild fauna.

Clinical syndromes associated with the circulation of multiple serotypes of bluetongue virus in dairy cattle in Israel

From 2008 to 2011, seven distinct bluetongue virus (BTV) serotypes (BTV-2, BTV-4, BTV-5, BTV-8, BTV-15, BTV-16 and BTV-24) have been identified to be circulating in diseased sheep and cattle in Israel. This paper describes the array of clinical manifestations caused by BTV in cattle in Israel. Each set of clinical manifestations has been categorised as a syndrome and six distinct clinical syndromes have been observed in dairy cattle: 'footrot-like syndrome', 'sore nose syndrome', 'subcutaneous emphysema syndrome', 'red/rough udder syndrome', 'bluetongue/epizootic haemorrhagic disease systemic syndrome' and 'maladjustment syndrome'.

Examination techniques and therapeutic regimens for the ruminant and camelid eye

A step-wise procedure and necessary equipment for examination of the ruminant and camelid eye are detailed. Restraint techniques and usage of local anesthetics to facilitate examination are described. Common examination findings and their significance are discussed. Finally, therapeutic options for keratoconjunctivitis and uveitis are explored. A complete ocular examination of ruminants is often not performed in the field because of lack of time, lack of appropriate facilities, and/or lack of equipment. Although individual ophthalmic examinations are not frequently performed as part of a herd health program, they can be of value in select cases. Ocular manifestations of systemic diseases may assist the clinician in establishing a diagnosis on the farm and for little additional cost. For patients with a specific ocular complaint, a complete ophthalmic examination is critical. After completion of the examination and arrival at a diagnosis, one must also be cognizant of the therapeutic regimens that are appropriate for use in ruminants, particularly animals that may be used for meat or milk.

Outbreak of malignant catarrhal fever among cattle associated with a state livestock exhibition

CASE DESCRIPTION

Severe disease and death were identified in cattle exhibited at a state fair that were naturally infected with ovine herpesvirus type 2 (OvHV-2).

CLINICAL FINDINGS

Most affected cattle had anorexia, signs of depression, diarrhea, fever, and respiratory distress ultimately leading to death. Mean duration of clinical signs prior to death was 6 days (range, 1 to 26 days). Mean number of days between apparent exposure and death was 71 days (range, 46 to 139 days).

TREATMENT AND OUTCOMES

19 of 132 cattle cohoused in 1 barn died of malignant catarrhal fever (MCF). The diagnosis of sheep-associated MCF was confirmed on the basis of results of an OvHV-2-specific PCR assay performed on tissue samples obtained from affected cattle. The disease was associated but not significantly with distance from the center of the barn and was not associated with distance from the center of the sheep pens.

CLINICAL RELEVANCE

Outbreaks of MCF in cattle are unusual, particularly in association with livestock exhibitions. Because the clinical signs may be similar to those of some transboundary diseases, cases of MCF should be reported and investigated. Findings for this outbreak provided evidence to suggest that fair boards and veterinarians should reexamine biosecurity recommendations for livestock exhibitions.

Malignant catarrhal fever: a review

Malignant catarrhal fever (MCF) is a fatal lymphoproliferative disease of cattle and other ungulates caused by the ruminant gamma-herpesviruses alcelaphine herpesvirus 1 (AlHV-1) and ovine herpesvirus 2 (OvHV-2). These viruses cause inapparent infection in their reservoir hosts (wildebeest for AlHV-1 and sheep for OvHV-2), but fatal lymphoproliferative disease when they infect MCF-susceptible hosts, including cattle, deer, bison, water buffalo and pigs. MCF is an important disease wherever reservoir and MCF-susceptible species mix and currently is a particular problem in Bali cattle in Indonesia, bison in the USA and in pastoralist cattle herds in Eastern and Southern Africa. MCF is characterised by the accumulation of lymphocytes (predominantly CD8(+) T lymphocytes) in a variety of organs, often associated with tissue necrosis. Only a small proportion of these lymphocytes appear to contain virus, although recent results with virus gene-specific probes indicate that more infected cells may be present than previously thought. The tissue damage in MCF is hypothesised to be caused by the indiscriminate activity of MHC-unrestricted cytotoxic T/natural killer cells. The pathogenesis of MCF and the virus life cycle are poorly understood and, currently, there is no effective disease control. Recent sequencing of the OvHV-2 genome and construction of an AlHV-1 bacterial artificial chromosome (BAC) are facilitating studies to understand the pathogenesis of this extraordinary disease. Furthermore, new and improved methods of disease diagnosis have been developed and promising vaccine strategies are being tested. The next few years are likely to be exciting and productive for MCF research.

Seroprevalence of malignant catarrhal fever-related gammaherpesviruses in domestic ruminants in Turkey

The prevalence of malignant catarrhal fever (MCF) virus infection in cattle, sheep and goat populations and also the prevalence of recovered and chronic MCF cases in north-western Turkey are reported. A total of 600 animals, 200 individuals of each species, located in four provinces were sampled between December 2003 and July 2005. A monoclonal antibody-based competitive inhibition (ci) ELISA were used to detect infection status of the animals. Detected antibody prevalence was 97.5%, 96.0% and 15.0% in sheep, goats and cattle, respectively. These results showed that MCF related gam-maherpesvirus infections are common in north-western Turkey. There was no significant difference between prevalences detected in sheep and goats, as well as various breeds of these species. There was also no significant difference among locations. Results of this study show that sheep and goats may equally be important in the epidemiology of MCF in Turkey. Seropositivity against MCF agents among cattle was 15.0%. The results indicate that MCF infections may be maintained in intensively managed cattle herds having no close contact with small ruminants.

Experimental aerosol infection of cattle (Bos taurus) with ovine herpesvirus 2 using nasal secretions from infected sheep

Infection of clinically susceptible ruminants, including domesticated cattle and American bison, with ovine herpesvirus 2 (OvHV-2) can result in the fatal lymphoproliferative and vasculitis syndrome known as malignant catarrhal fever (MCF). A reliable experimental infection model is needed to study the pathogenesis of MCF and to develop effective vaccination strategies to control the disease. An experimental aerosol infection model using sheep, the natural carriers of OvHV-2, has been developed (Taus et al., 2005). Using the protocol and OvHV-2 inoculum established in the previous study, eight calves were nebulized with four different doses of OvHV-2 in nasal secretions from infected sheep. Two control calves were nebulized with nasal secretions from uninfected sheep. Infection status of all calves was monitored using competitive inhibition ELISA, PCR and clinical parameters. Six of eight nebulized calves became infected with OvHV-2. One calf receiving the highest dose of virus developed typical clinical, gross and histological changes of MCF. This study showed that nasal secretions collected from sheep experiencing OvHV-2 shedding episodes were infectious for cattle and capable of inducing MCF. The data also indicate that cattle are relatively resistant to disease following infection. The use of more susceptible species as experimental animal models, such as bison and selected cervid species should be examined.

Development of an enzyme-linked immunosorbent assay for the detection of antibodies against malignant catarrhal fever viruses in cattle serum

Malignant catarrhal fever (MCF) is a sporadic but fatal lymphoproliferative viral disease of cattle, deer and other ruminants. The causative agents are highly-cell-associated herpesviruses of the subfamily gammaherpesvirinae. In this study, an ELISA (WC11-ELISA) was developed to detect antibody to malignant catarrhal fever virus (MCFV) in cattle serum and compared to the commercially produced competitive-inhibition ELISA (CI-ELISA). Crude lysate antigen from alcelaphine herpesvirus-1 strain WC11 was bound to 96-well microplates and used to capture antibodies to MCFV. Dilutions of test sera were added to wells containing bound MCF antigen and control wells containing uninfected cell lysates. A horseradish peroxidase-labelled rabbit-anti-bovine IgG conjugate detected antibodies to MCF, and the results were expressed as absorbance readings at 450 nm. Samples were selected blind from cattle sera which had been sent to the laboratory for diagnostic testing for MCFV antibodies and were tested in both the WC11-ELISA and the CI-ELISA. Good agreement between the WC11-ELISA and CI-ELISA test (k=0.86, n=95) results was found.

Evaluation of ovine herpesvirus type 2 infections, as detected by competitive inhibition ELISA and polymerase chain reaction assay, in dairy cattle without clinical signs of malignant catarrhal fever

OBJECTIVE

To monitor ovine herpesvirus type 2 (OvHV-2) infection status and the association between OvHV-2 infection and development of clinical signs of malignant catarrhal fever (MCF) in cattle.

DESIGN

Longitudinal study.

ANIMALS

30 mature adult cows and 18 cattle submitted for necropsy.

PROCEDURE

Blood and milk samples were collected at monthly intervals from 30 adult cows for 20 consecutive months. Nasal and ocular swab specimens were also collected during months 9 through 20. Polymerase chain reaction (PCR) assay for detection of OvHV-2 was performed on blood, milk, nasal swab, and ocular swab specimens. Competitive inhibition ELISA (CI-ELISA) for detection of antibodies against MCF viruses was performed on serum samples obtained prior to study initiation and monthly during the last 12 months. Tissues obtained from herdmates without clinical signs of MCF that were submitted for necropsy were analyzed for OvHV-2 DNA via PCR assay for possible sites of latency.

RESULTS

Initially, 8 of 30 cows had positive CI-ELISA results. Seroconversion was detected in 4 cows. Ovine herpesvirus type 2 DNA was intermittently detected in blood, milk, nasal secretions, or ocular secretions from 17 of 30 cows. Twenty-one cows had positive CI-ELISA or PCR assay results. No cattle in the study developed clinical signs of MCF. Results of PCR assays performed on tissue samples from 2 of 18 animals submitted for necropsy were positive for OvHV-2. CONCLUSIONS AND CLINICAL RELEVANCE; OvHV-2 infection can occur in cattle without concurrent development of clinical MCF. Ovine herpesvirus type 2 DNA was detected intermittently, suggesting fluctuating viral DNA loads or reinfection in subclinical cattle. A definitive site of latency was not identified from tissues obtained during necropsy.