Detection and characterisation of sheep-associated malignant catarrhal fever infection from ruminants by using tegument and gB gene sequences of OvHV-2.

In this study, positive blood and organ samples were obtained from different mixed herds of sheep and cattle against ovine herpesvirus 2 (OvHV-2) infection. Target-positive DNA was sequenced and compared with worldwide distributed OvHV-2 sequences. Tegument gene (422 base pairs) and glycoprotein B (gB) gene (2800 base pairs) amplicons of OvHV-2 genome were used for understanding of epidemiology of malignant catarrhal fever (MCF) infection in Turkey. The results of nucleotide sequencing of polymerase chain reaction (PCR) products indicated presence of sheep-associated form for MCF infection in Turkey. Although the obtained sequences were genetically different from each other, it was found that genetic variations were limited.

A review of the epidemiological, clinical, and pathological aspects of malignant catarrhal fever in Brazil.

Sheep-associated malignant catarrhal fever (SA-MCF), the form of MCF that occurs in Brazil, is a severe, frequently fatal, infectious disease caused by ovine gammaherpesvirus-2 (OvHV-2), in which sheep are the asymptomatic hosts and cattle and other cloven-hoofed animals are the accidental hosts. This review provides a critical analysis of the historical, epidemiological aspects and the estimated economic impacts associated with SA-MCF in Brazil. Moreover, the clinical manifestations and pathological lesions associated with SA-MCF in cattle are reviewed and discussed and the phylogenetic distribution of OvHV-2 in Brazil is presented. OvHV-2 is the only MCF virus identified in animals from Brazil. It is recommended that a histopathologic diagnosis of SA-MCF be based on all aspects of vascular disease in the affected animal and not only lymphocytic/necrotizing vasculitis and/or fibrinoid change. Conformation of the intralesional participation of OvHV-2 in these alterations can be achieved by immunohistochemistry and/or in situ hybridization assays. Additionally, it is proposed that OvHV-2 should be considered as a possible infectious disease agent associated with the development of bovine respiratory disease in cattle. Furthermore, the possible role of the small intestine in the dissemination of OvHV-2 is discussed.

Ibex-Associated Malignant Catarrhal Fever in Duikers (Cephalophus Spp).

Eight duikers, representing 3 different species cohoused in a single zoological collection, died in a 10-month period. Black, red-flanked, and yellow-backed duikers were affected, appearing clinically with a combination of anorexia, diarrhea, ataxia, tremors, and/or stupor, followed by death within 72 hours of onset of clinical signs. Consistent gross findings were pulmonary ecchymoses (8/8), generalized lymphadenomegaly (6/8), ascites (5/8), and pleural effusion (4/8). Dense lymphocyte infiltrates and arteritis affected numerous tissues in most animals. Ibex-associated malignant catarrhal fever (MCF) viral DNA was detected in all cases by polymerase chain reaction and in situ hybridization. Identical ibex-MCF virus sequence was detected in spleen of a clinically healthy ibex (Capra ibex) housed in a separate enclosure 35 meters away from the duikers.

Ovine Herpesvirus 2 Encodes a Previously Unrecognized Protein, pOv8.25, That Targets Mitochondria and Triggers Apoptotic Cell Death.

Malignant catarrhal fever (MCF) is a rare but frequently lethal disease of certain cloven-hoofed animals. At least 10 different viruses, all members of the Macavirus genus in the subfamily Gammaherpesvirinae, are known as causative agents of MCF. Among these, ovine herpesvirus 2 (OvHV-2) is the most frequent and economically most important MCF agent. Phenotypically, MCF is characterized by severe lymphocytic arteritis-periarteritis, which leads to the accumulation of activated lymphocytes accompanied by apoptosis and necrosis in a broad range of tissues. However, a viral factor that might be responsible for tissue damage has not yet been identified. We have studied a seemingly intergenic locus on the OvHV-2 genome, which was previously shown to be transcriptionally highly active in MCF-affected tissue. We identified by 5' and 3' rapid amplification of cDNA ends (RACE) a conserved, double-spliced transcript that encoded a 9.9-kDa hydrophobic protein. The newly detected gene, Ov8.25, and its splicing pattern were conserved among OvHV-2 strains of different origins. Upon transient expression of synthetic variants of this gene in various cell types, including bovine lymphocytes, the protein (pOv8.25) was shown to target mitochondria, followed by caspase-dependent apoptosis and necrosis. Notably, a deletion mutant of the same protein lost these abilities. Finally, we detected pOv8.25 in brain-infiltrating lymphocytes of cattle with MCF. Thus, the cell death-causing properties of pOv8.25 in affected cells may be involved in the emergence of typical MCF-associated apoptosis and necrosis. Thus, we have identified a novel OvHV-2 protein, which might contribute to the phenotype of MCF-related lesions.IMPORTANCE Ovine herpesvirus 2 (OvHV-2) circulates among sheep without causing disease. However, upon transmission to cattle, the same virus instigates a frequently lethal disease, malignant catarrhal fever (MCF). While the cause of death and pathogenesis of tissue lesions are still poorly understood, MCF is characterized by the accumulation of lymphocytes in various tissues, associated with vasculitis and cell death. As infectious virus is hardly present in these lesions, the cause of cell death cannot be explained simply by viral replication. The significance of our research is in identifying and characterizing a previously overlooked gene of OvHV-2 (Ov8.25), which is highly expressed in animals with MCF. Its encoded protein targets mitochondria, causing apoptosis and necrosis, thus contributing to an understanding of the source and nature of cell death. As the corresponding genetic locus is also active in the context of MCF due to a different macavirus, we may have detected a common denominator of the disease phenotype.

Immunohistochemical Detection of Intralesional Antigens of Ovine Gammaherpesvirus-2 in Cattle with Sheep-associated Malignant Catarrhal Fever.

Sheep-associated malignant catarrhal fever (SA-MCF) is a severe lymphoproliferative disease of ruminants caused by ovine gammaherpesvirus-2 (OvHV-2). Since the initial identification of SA-MCF there has been extensive research related to the pathogenesis of OvHV-2, based primarily on serological and molecular assays associated with typical histopathological findings. The monoclonal antibody (MAb-15A) binds to a common epitope in MCF viruses and is used frequently in serological investigations. However, the utilization of this antibody to detect antigens of OvHV-2 in tissues has not been examined. Accordingly, this study standardized an immunohistochemical assay using MAb-15A to identify antigens of OvHV-2 in tissues of cattle (n = 5) with SA-MCF. All animals developed acute neurological signs, without ocular and nasal manifestations, and had nucleic acids of OvHV-2 in brain tissue detected by polymerase chain reaction. The principal histopathological findings were lymphocytic nephritis (n = 5), widespread arterial proliferation and vasculitis (n = 5), lymphocytic portal hepatitis (n = 3), non-suppurative meningoencephalitis (n = 2) and atrophic enteritis with cryptal necrosis and dilation (n = 2). Intralesional intracytoplasmic antigens of OvHV-2 were identified within multiple epithelial cells of the kidneys of all animals, the intestines of animals with and without atrophic enteritis, and within epithelial cells of bile ducts in animals with lymphocytic hepatitis. Additionally, there was positive intracytoplasmic immunoreactivity within histiocytes and lymphocytes in several tissues. These findings suggest that the MAb-15A detects antigens of OvHV-2 within epithelial cells and leucocytes in several organs. Moreover, this assay would contribute significantly towards understanding of the pathogenesis of SA-MCF and may be used for retrospective studies. Additionally, angiopathy in SA-MCF may be a progressive lesion, which may terminate in luminal occlusion and probably occurs irrespectively of the eye and head form of MCF.

Malignant catarrhal fever: An emerging yet neglected disease in captive sika deer (Cervus nippon) herds in China.

Malignant catarrhal fever (MCF) is a fatal lymphoproliferative disease that represents a serious problem in the deer-rearing industry. To better understand an MCF-like disease that has emerged in northern China since 2015, we investigated ten cases by documenting clinical and epidemiological data and analysing causative agents and histopathological changes. In addition, a retrospective screen for Macavirus DNA and a questionnaire-based survey were conducted. Epizootic MCF in Chinese sika deer herds has emerged with a low morbidity of 3.8% (95% CI: 2.5%-5.1%) and a high mortality of 93.2% (95% CI: 86.6%-99.9%). The disease course varied from 3 to 12 days. Aetiologically, OvHV-2 was predominant in the MCFV, accounting for most MCF cases (21/23). In contrast, only two CpHV-2 isolates were phylogenetically closely related to CpHV-2. Diarrhoea and nasal discharges were the most frequent manifestations, although clinical signs varied in some cases. Pathologically typical lesions of haemorrhage, necrosis and lymphoid cell infiltration were readily observed in a variety of organs. Vasculitis caused by vascular and perivascular lymphoid cell infiltration was common. The retrospective survey suggested a low positive rate (3/275) of MCFV DNA in peripheral blood lymphocytes (PBL). The questionnaire-based survey suggested the disease was neglected by local veterinarians, who did not acknowledge the risk of co-rearing deer with reservoir species. Collectively, the emerging epizootic MCF in Chinese sika deer herds remains neglected, emphasizing the urgency of initiating full-field diagnoses and control strategies.

GENETIC DIVERSITY of OVINE HERPESVIRUS 2 STRAINS OBTAINED FROM MALIGNANT CATARRHAL FEVER CASES in EASTERN TURKEY.

Malignant Catarrhal Fever (MCF) is a generalized, definitive lethal disease affecting the epithelial and lymphoid tissues of the respiratory and digestive tract, mainly cattle and some wild ruminants such as deer, buffalo or antelope. The sheep-related form of MCF is known to be present in Turkey and is caused by ovine herpesvirus 2 (OvHV-2). The aim of this study was to reveal the genetic diversity of OvHV-2 strains obtained from MCF cases in Eastern Turkey where the livestock industry has an important impact on economic activities. For this purpose, RTA (Replication and transcription activator), FGARAT (formylglycineamide ribotide amidotransferase) and some of glycoprotein genes (Ov7, Ov8 ex2, ORF27 and Ov9.5) were investigated in blood samples from 24 cattles, clinically diagnosed with MCF. Genomic data of chosen samples were furthermore used to characterize and undergo combined phylogenetic analysis to determine possible alleles and subvariants. The results showed that high level of OvHV-2 diversity existed in selected genes and strains carrying allelic variants might circulate both in two geographically distinct regions and in a region itself. Moreover, three different OvHV-2 types and various subtypes were identified based on multi locus approach. This study provides important data to epidemiological research and thereby helps to determine the source of the virus and understand the spread of the disease.

A randomised vaccine field trial in Kenya demonstrates protection against wildebeest-associated malignant catarrhal fever in cattle.

Wildebeest-associated malignant catarrhal fever (WA-MCF), a fatal disease of cattle caused by alcelaphine herpesvirus 1 (AlHV-1), is one of the most important seasonal diseases of cattle in wildebeest endemic areas, with annual incidence reaching 10%. Here we report efficacy of over 80% for a vaccine based on the attenuated AlHV-1 C500 strain, in preventing fatal WA-MCF in cattle exposed to natural wildebeest challenge. The study was conducted at Kapiti Plains Ranch Ltd, south-east of Nairobi, Kenya. In 2016, 146 cattle were selected for a randomised placebo-controlled trial. Cattle were stratified according to breed and age and randomly assigned to groups given vaccine or culture medium mixed with Emulsigen®. Cattle received prime and boost inoculations one month apart and few adverse reactions (n = 4) were observed. Indirect ELISA demonstrated that all cattle in the vaccine group developed a serological response to AlHV-1. The study herd was grazed with wildebeest from one month after booster vaccination. Three cattle, two that received vaccine and one control, succumbed to conditions unrelated to WA-MCF before the study ended. Twenty-five cattle succumbed to WA-MCF; four of the remaining 71 cattle in the vaccine group (5.6%) and 21 of the remaining 72 control cattle (29.2%; χ2 = 13.6, df = 1, p < 0.001). All of the WA-MCF affected cattle were confirmed by PCR to be infected with AlHV-1 and in 23 cases exhibited histopathology typical of WA-MCF. Vaccine efficacy was determined to be 80.6% (95% CI 46.5-93.0%). Hence, the AlHV-1 C500 vaccine is a safe and potentially effective novel method for controlling WA-MCF in cattle. The implementation of this vaccine may have significant impacts on marginalised cattle keeping communities.

Field validation of clinical and laboratory diagnosis of wildebeest associated malignant catarrhal fever in cattle.

BACKGROUND: Wildebeest associated malignant catarrhal fever (WA-MCF) is a fatal disease of cattle. Outbreaks are seasonal and associated with close interaction between cattle and calving wildebeest. In Kenya, WA-MCF has a dramatic effect on cattle-keepers who lose up to 10% of their cattle herds per year. The objective of this study was to report the impact of WA-MCF on a commercial ranch and assess the performance of clinical diagnosis compared to laboratory diagnosis as a disease management tool. A retrospective study of WA-MCF in cattle was conducted from 2014 to 2016 at Kapiti Plains Ranch Ltd., Kenya. During this period, 325 animals showed clinical signs of WA-MCF and of these, 123 were opportunistically sampled. In addition, 51 clinically healthy animals were sampled. Nested polymerase chain reaction (PCR) and indirect enzyme linked immunosorbent assay (ELISA) were used to confirm clinically diagnosed cases of WA-MCF. A latent class model (LCM) was used to evaluate the diagnostic parameters of clinical diagnosis and the tests in the absence of a gold standard. RESULTS: By PCR, 94% (95% C.I. 89-97%) of clinically affected animals were positive to WA-MCF while 63% (95% C.I. 54-71%) were positive by indirect ELISA. The LCM demonstrated the indirect ELISA had poor sensitivity 63.3% (95% PCI 54.4-71.7%) and specificity 62.6% (95% PCI 39.2-84.9%) while the nested PCR performed better with sensitivity 96.1% (95% PCI 90.7-99.7%) and specificity 92.9% (95% PCI 76.1-99.8%). The sensitivity and specificity of clinical diagnosis were 99.1% (95% PCI 96.8-100.0%) and 71.5% (95% PCI 48.0-97.2%) respectively. CONCLUSIONS: Clinical diagnosis was demonstrated to be an effective method to identify affected animals although animals may be incorrectly classified resulting in financial loss. The study revealed indirect ELISA as a poor test and nested PCR to be a more appropriate confirmatory test for diagnosing acute WA-MCF. However, the logistics of PCR make it unsuitable for field diagnosis of WA-MCF. The future of WA-MCF diagnosis should be aimed at development of penside techniques, which will allow for fast detection in the field.

In Situ Hybridization for Localization of Ovine Herpesvirus 2, the Agent of Sheep-Associated Malignant Catarrhal Fever, in Formalin-Fixed Tissues.

A constraint on understanding the pathogenesis of malignant catarrhal fever (MCF) is the limited number of tools to localize infected cells. The amount of detectable virus, visualized in the past either by immunohistochemistry or in situ hybridization (ISH), has been modest in fixed or frozen tissues. This complicates our understanding of the widespread lymphoid proliferation, epithelial necrosis/apoptosis, and arteritis-phlebitis that characterize MCF. In this work, we developed a probe-based in situ hybridization assay targeting 2 ovine herpesvirus 2 (OvHV-2) genes, as well as their respective transcripts, in formalin-fixed tissues. Using this approach, OvHV-2 nucleic acids were detected in lymphocytes in MCF-affected animals following both natural infection (American bison and domestic cattle) and experimental infection (American bison, rabbits, and pigs). The probe did not cross-react with 4 closely related gammaherpesviruses that also cause MCF: alcelaphine herpesvirus 1, alcelaphine herpesvirus 2, caprine herpesvirus 2, and ibex-MCF virus (MCFV). No signal was detected in control tissues negative for OvHV-2. ISH will be of value in analyzing the natural progression of OvHV-2 infection in time-course studies following experimental infection and in addressing the pathogenesis of MCF.

MOOSE ( ALCES ALCES) MORTALITY ASSOCIATED WITH CAPRINE HERPESVIRUS 2 (CPHV-2) IN A ZOOLOGICAL COLLECTION.

Malignant catarrhal fever (MCF) can affect both domestic and wild artiodactyls. In a zoological setting, in which subclinical carriers and susceptible species are often housed in close proximity, the disease can prove fatal. This report describes a case of goat-associated MCF in a captive moose ( Alces alces). The diagnosis was confirmed by histopathology, which showed lymphocytic vasculitis in the brain and panuveitis, and by detection of caprine herpesvirus 2 DNA in tissues. Identical viral DNA sequences amplified from the clinically affected moose and from domestic, petting goats ( Capra aegagrus hircus) housed in the zoo suggest that the goats were the source for the virus transmutation. This is the first report, to our knowledge, of confirmed goat-associated MCF in any moose in North America and of the surveillance measures and procedures put in place to prevent additional spread of the disease.

Seroprevalence of malignant catarrhal fever virus in captive wildebeest (Connochaetes sp.) in France.

Alcelaphine herpesvirus 1 (AlHV-1) is a gammaherpesvirus carried asymptomatically by wildebeests (Connochaetes sp.) in sub-Saharan Africa. Although asymptomatic in wildebeest, AlHV-1 infection in a number of other ruminant species causes a severe and fatal lymphoproliferative disease named wildebeest-derived malignant catarrhal fever (WD-MCF). Several endangered species of captive ruminants are highly susceptible to developing WD-MCF if infected by AlHV-1, which is a critical concern in zoos, game reserves and wildlife parks where wildebeests are also kept in captivity. Here, we investigated the seroprevalence of AlHV-1 in 52 captive wildebeests randomly sampled from five different zoos in France. We found 46% (24/52) seropositive animals and detected AlHV-1 DNA in one of them, demonstrating that AlHV-1 infection is present in captive wildebeests in France. In an interesting manner, the repartition of seropositive wildebeests was not homogenous between zoos with 100% (20/20) of seronegative animals in three parks. These results further highlight the importance of considering WD-MCF as a threat for clinically susceptible species and encourage for testing AlHV-1 infection in captive wildebeests as a management control strategy.

High copy number of ovine gammaherpesvirus 2 DNA associated with malignant catarrhal fever-like syndrome in a lamb.

Domestic and wild sheep are the natural reservoirs for ovine gammaherpesvirus 2 (OvHV-2), the causative agent of sheep-associated malignant catarrhal fever (SA-MCF). Virtually all adult sheep are infected with OvHV-2 under natural flock conditions, and infection is normally subclinical. MCF-like clinical signs and typical histologic lesions in sheep have been linked during case investigations at veterinary diagnostic laboratories; however, the confirmation of naturally occurring MCF in sheep is problematic. To date, the assays for detection of OvHV-2-specific antibodies or DNA are usually positive in sheep, regardless of health status, so mere detection of antibodies or the agent is of minimal diagnostic significance in this species. We document herein a naturally occurring MCF case in a 4-mo-old domestic lamb and demonstrate that the affected animal had 100-1,000 times more OvHV-2 copy numbers in tissues than in healthy adult and age-matched sheep. These results indicate that high copy numbers of viral DNA in tissues associated with characteristic lesions can be used to confirm the diagnosis of MCF in sheep.

Caprine herpesvirus 2-associated malignant catarrhal fever of captive sika deer (Cervus nippon) in an intensive management system.

BACKGROUND: Caprine herpesvirus 2 (CpHV-2) infection usually induces chronic malignant catarrhal fever (MCF) in sika deer (Cervus nippon), with the primary signs of weight loss, dermatitis and alopecia. CASE PRESENTATION: Here, we report a case of CpHV-2-associated acute MCF in a sika deer herd raised in an intensive management system distant to the reservoir goats. Affected deer developed clinical signs of high fever (41 °C) followed by nasal discharge and lameness. Severe lesions of hemorrhage, necrosis and infiltration of lymphoid cells could readily be observed in the lung, kidney, heart valves and subcutaneous tissue surrounding a tendon. Etiologically, identical CpHV-2 specific DNA sequences were detected in peripheral blood lymphocyte (PBL) from the affected deer and reservoir goats. CONCLUSION: In summary, domestic goats were the reservoir of the CpHV-2, which is the causative agent of the outbreak of MCF in the three hinds. The disease was probably transmitted via aerosol infection. In addition, necrosis and inflammation in subcutaneous tissue surrounding a tendon was the reason for lameness. Therefore, MCF should be put into a differential diagnostic list when similar disease occurs in sika deer herds.

Alcelaphine gammaherpesvirus 1-induced malignant catarrhal fever in a Watusi ( Bos taurus africanus) steer in a North American game park.

A 10-y-old Watusi ( Bos taurus africanus) steer housed at a drive-through game park in Winston, Oregon developed severe clinical illness including fever, marked nasal discharge, injected scleral and conjunctival membranes, plus oral hemorrhages and erosions. The animal responded poorly to supportive treatment and was euthanized. Additional gross findings at postmortem examination included papules and erosive lesions on the tongue, hemorrhagic large intestine, and multifocal cardiac hemorrhages. Histopathologic findings included multifocal lymphoplasmacytic vasculitis plus fibrin exudation in heart and tongue. Total DNA obtained from the splenic samples was positive for alcelaphine gammaherpesvirus 1 (AlHV-1) as tested by a multiplex PCR for malignant catarrhal fever (MCF) viruses. The AlHV-1 detection was further confirmed by amplification and sequencing of a viral DNA polymerase gene fragment, which was identical to AlHV-1 sequences in GenBank. This was the first diagnosis of clinical wildebeest-associated MCF on these premises, although wildebeest have been held at the park for over 25 y. This disease is sporadic in North America and should be considered as a differential diagnosis for febrile illness with ulcerative oral lesions in ruminants.

Genetic characterization of ovine herpesvirus 2 strains involved in water buffaloes malignant catarrhal fever outbreaks in Southern Italy.

Ovine herpesvirus 2 (OvHV-2) was responsible for two outbreaks of malignant catarrhal fever (MCF) on two water buffalo farms in Southern Italy. In this study, the presence of this virus in the nasal swabs from sick animals as well as in the organs of dead buffaloes was ascertained by a Real-time PCR assay. Positive samples also underwent a relative quantitative analysis of the viral DNA in them. All the dead animals had the highest relative viral quantities, while buffaloes recovering from the virus had intermediate quantities, and asymptomatic OvHV-2-positive sheep had the lowest relative quantities (as compared with the calibrator). The strains involved in the MCF outbreaks underwent genetic characterization by sequencing segments of their ORF50, ORF75 and Ov9.5 genes. The results showed that the outbreaks were caused by two specific genetic variants of OvHV-2, and that these variants exhibit nucleotide differences at the loci analysed. Sheep living in the surrounding farms, as well as sheep kept with buffaloes, were also investigated as possible transmitters of the virus. In this regard, local strategies for the control of MCF should consider separating reservoir species from susceptible animals.

The efficacy of alcelaphine herpesvirus-1 (AlHV-1) immunization with the adjuvants Emulsigen® and the monomeric TLR5 ligand FliC in zebu cattle against AlHV-1 malignant catarrhal fever induced by experimental virus challenge.

Malignant catarrhal fever (MCF) is a fatal disease of cattle that, in East Africa, follows contact with wildebeest excreting alcelaphine herpesvirus 1 (AlHV-1). Recently an attenuated vaccine (atAlHV-1) was tested under experimental challenge on Friesian-Holstein (FH) cattle and gave a vaccine efficacy (VE) of approximately 90%. However testing under field conditions on an East African breed, the shorthorn zebu cross (SZC), gave a VE of 56% suggesting that FH and SZC cattle may respond differently to the vaccine. To investigate, a challenge trial was carried out using SZC. Additionally three adjuvant combinations were tested: (i) Emulsigen®, (ii) bacterial flagellin (FliC) and (iii) Emulsigen®+bacterial flagellin. We report 100% seroconversion in all immunized cattle. The group inoculated with atAlHV-1+Emulsigen® had significantly higher antibody titres than groups inoculated with FliC, the smallest number of animals that became infected and the fewest fatalities, suggesting this was the most effective combination. A larger study is required to more accurately determine the protective effect of this regime in SZC. There was an apparent inhibition of the antibody response in cattle inoculated with atAlHV-1+FliC, suggesting FliC might induce an immune suppressive mechanism. The VE in SZC (50-60%) was less than that in FH (80-90%). We speculate that this might be due to increased risk of disease in vaccinated SZC (suggesting that the vaccine may be less effective at stimulating an appropriate immune response in this breed) and/or increased survival in unvaccinated SZC (suggesting that these cattle may have a degree of prior immunity against infection with AlHV-1).

An Acute Multispecies Episode of Sheep-Associated Malignant Catarrhal Fever in Captive Wild Animals in an Italian Zoo.

In July 2011, in a zoological garden in Rome, Italy, malignant catarrhal fever (MCF), a fatal, systemic disease of Artiodactyla, was suspected on the basis of neurological signs and gross lesions observed in a banteng, the first animal to die of this infection. An MCF type-specific PCR with subsequent sequencing of the PCR amplicon confirmed the aetiological agent as ovine herpesvirus-2 (OvHV-2). Biological samples were collected from the dead animals for gross, histological, bacteriological, virological and serological examinations. An epidemiological investigation was conducted to identify the source of the outbreak, as further deaths due to OvHV-2 still occurred after the removal of the acknowledged reservoirs, domestic sheep and goats. For this purpose, samples from other susceptible species and reservoir hosts were collected for virological and serological analysis. In conjunction, a retrospective sero-investigation was conducted on sera collected between 1999 and 2010 from some of the species involved in the present episode. In total, 11 animals belonging to four different species (banteng, Himalayan tahr, Nile lechwe and sika deer) died between July 2011 and October 2012. The severe gross and histological lesions were consistent with the disease, namely haemorrhages and congestion of several organs as well as lymphoid cell infiltrates and vasculitis of varying severity. The virological tests confirmed that all animals had died of sheep-associated MCF. The investigation indicated that the OvHV-2 infection could have been due to the arrival of sheep in the petting zoo, with cases commencing after first lambing and subsequent shedding of virus. This was also supported by the serological retrospective study that indicated limited previous MCF virus circulation. Further MCF cases that occurred even after the removal of the domestic sheep and goats were attributed to the mouflon. This episode confirms the importance of biosecurity measures in zoos, which house MCF susceptible species, especially those endangered.

Wildebeest-associated malignant catarrhal fever: perspectives for integrated control of a lymphoproliferative disease of cattle in sub-Saharan Africa.

Wildebeest-associated malignant catarrhal fever (WA-MCF), an acute lymphoproliferative disease of cattle caused by alcelaphine herpesvirus 1 (AlHV-1), remains a significant constraint to cattle production in nomadic pastoralist systems in eastern and southern Africa. The transmission of WA-MCF is dependent on the presence of the wildlife reservoir, i.e. wildebeest, belonging to the species Connochaetes taurinus and Connochaetes gnou; hence, the distribution of WA-MCF is largely restricted to Kenya, Tanzania and the Republic of South Africa, where wildebeest are present. WA-MCF is analogous to sheep-associated MCF (SA-MCF) in many aspects, with the latter having sheep as its reservoir host and a more global distribution, mainly in developed countries with intensive livestock production systems. However, unlike SA-MCF, the geographic seclusion of WA-MCF may have contributed to an apparent neglect in research efforts aimed at increased biological understanding and control of the disease. This review aims to highlight the importance of WA-MCF and the need for intensified research towards measures for its integrated control. We discuss current knowledge on transmission and geographical distribution in eastern and southern Africa and the burden of WA-MCF in affected vulnerable pastoral communities in Africa. Recent findings towards vaccine development and pertinent knowledge gaps for future research efforts on WA-MCF are also considered. Finally, integrated control of WA-MCF based on a logical three-pronged framework is proposed, contextualizing vaccine development, next-generation diagnostics, and diversity studies targeted to the viral pathogen and cattle hosts.

Cross-Reactivity of Neutralizing Antibodies among Malignant Catarrhal Fever Viruses.

Some members of the gamma herpesvirus genus Macavirus are maintained in nature as subclinical infections in well-adapted ungulate hosts. Transmission of these viruses to poorly adapted hosts, such as American bison and cattle, can result in the frequently fatal disease malignant catarrhal fever (MCF). Based on phylogenetic analysis, the MCF viruses (MCFV) cluster into two subgroups corresponding to the reservoir hosts' subfamilies: Alcelaphinae/Hippotraginae and Caprinae. Antibody cross-reactivity among MCFVs has been demonstrated using techniques such as enzyme linked immunosorbent and immunofluorescence assays. However, minimal information is available as to whether virus neutralizing antibodies generated against one MCFV cross react with other members of the genus. This study tested the neutralizing activity of serum and plasma from select MCFV-infected reservoir hosts against alcelaphine herpesvirus 1 (AlHV-1) and ovine herpesvirus 2 (OvHV-2). Neutralizing antibody activity against AlHV-1 was detected in samples from infected hosts in the Alcelaphinae and Hippotraginae subfamilies, but not from hosts in the Caprinae subfamily. OvHV-2 neutralizing activity was demonstrated in samples from goats (Caprinae) but not from wildebeest (Alcelaphinae). These results show that neutralizing antibody cross reactivity is present to MCFVs within a virus subgroup but not between subgroups. This information is important for diagnosing infection with MCFVs and in the development of vaccines against MCF.