Immunohistochemical identification of a malignant catarrhal fever virus in cattle with renal diseases from Paraná state, Southern Brazil: a retrospective epidemiological study

Malignant catarrhal fever (MCF) is a viral infectious disease caused by specific members of the Macavirus genus that are referred to as the MCF virus (MCFV) complex group. This study determined the prevalence of MCFV-associated infections in cattle within the mesoregions of the state of Paraná, Southern Brazil, by analyzing the histopathologic patterns of renal lesions in association with positive immunoreactivity to intralesional antigens of MCFV. Intracytoplasmic MCFV antigens were identified in 41.7% (48/115) of the kidneys of cattle evaluated. Lymphocytic interstitial nephritis, vascular degeneration, and ballooning degeneration of the renal tubules were the principal histopathological findings associated with positive immunoreactivity to MCFV. The results indicate that MCFV infections are endemic within the state of Paraná and suggest that the kidney can be of diagnostic value in suspected cases of MCF-associated infections in cattle. Furthermore, the utilization of an in situ diagnostic technique resulted in the detection of a greater number of cases of infections by MCFV than previously identified using other diagnostic methods. Additionally, degenerative vascular lesions of the kidney should be considered during the establishment of a histological diagnosis of MCFV-induced infections in cattle in the absence of fibrinoid change or necrotizing vasculitis.

First identification and characterization of ovine gammaherpesvirus type 2 in horses and artiodactyla from an outbreak of malignant catarrhal fever in Mexico

Ovine gammaherpesvirus 2 (OvHV-2), a member of the genus Macavirus, causes sheep-associated malignant catarrhal fever (SA-MCF), a fatal lymphoproliferative disease affecting a wide variety of ungulates in addition to horses. This study described an outbreak of SA-MCF in Mexico and the identification of the OvHV-2 virus in primary rabbit testis cultures through the generation of intranuclear inclusion bodies, syncytia, immunofluorescence (IF), immunocytochemistry (ICC), immunohistochemistry (IHC), endpoint polymerase chain reaction (PCR), and partial sequencing of the ORF75 gene. The animals involved in this outbreak showed mucogingival ulcers in the vestibule of the mouth and tongue, hypersalivation, corneal opacity, reduced food consumption, and weight loss of variable severity. These clinical signs and the histopathological findings suggested the diagnosis of SA-MCF. Buffy coat fractions from the anticoagulated blood samples of ill animals were collected and analyzed by PCR. Positive buffy coats were used to inoculate the primary cell cultures of rabbit testis to identify the virus. Small clusters of refractile cytomegalic cells, characteristic of viral cytopathic effects, were observed between 48 and 72 h post-infection. Furthermore, intranuclear acidophilic inclusion bodies (IBs) were identified in the inoculated primary culture cells, and the cytoplasm showed immunoreactivity with hyperimmune rabbit serum against OvHV-2. Moreover, in the liver histological sections from sick deer, immunoreactive juxtanuclear IBs were identified with the same rabbit hyperimmune serum. The obtained sequences were aligned with the OvHV-2 sequences reported in GenBank and revealed a nucleotide identity higher than 98%. Based on the evidence provided in this study, we conclude that the outbreak of SA-MCF in the municipality of Tequisquiapan in the state of Queretaro, Mexico, was caused by OvHV-2. This is the second study reporting that horses are susceptible to OvHV-2 infection and can develop SA-MCF. We identified for the first time in Mexico, the presence of OvHV-2 in buffy coats from horses and Artiodactyla.

Wildlife: topical issues, recent cases

This focus article was prepared by Paul Duff, Paul Holmes and Alex Barlow of the APHA Wildlife Expert Group.

An Outbreak of Sheep-Associated Malignant Catarrhal Fever in Bison (Bison Bison) after Exposure to Sheep at a Public Auction Sale

An outbreak of malignant catarrhal fever (MCF) among bison sold at an auction market was studied for an 18-month period. Forty-five of 163 bison submitted for sale from 8 different bison farms died on 7 other destination farms. The outbreak began on day 50 after the sale, peaked between days 60 and 70, and ended on day 220. Twenty-one dead bison were confirmed to be MCF cases by clinical histories, pathology, and detection of ovine herpesvirus-2 DNA in their tissues with polymerase chain reaction assays. Twenty-four dead bison were classified as suspect MCF cases from clinical histories. No cases of MCF were observed among bison remaining on originating farms or resident bison mixed with sale bison on destination farms. There were no sheep reported within 3 km of originating or destination farms, limiting bison exposure to sheep to the auction facility, where sheep were present for less than 1 day. The outbreak provides an illustration of the temporal distribution of MCF mortality expected in bison and an estimate of the time from exposure until death from MCF after a single short exposure to sheep. The study provides evidence that bison with MCF do not transmit MCF to other bison.

An observational study of mortality on bison farms in Saskatchewan with special emphasis on malignant catarrhal fever

In December 2011, the Malignant Catarrhal Fever (MCF) Task Force in Saskatchewan recommended that research be conducted on the relationship between the proximity of bison and sheep under typical commercial production settings and bison deaths due to MCF. The objective of this study was to evaluate all causes of death in bison herds and compare the incidence of MCF in herds at varying distances of exposure from sheep operations. Necropsies were completed on 76 of 133 bison reported to have died during the 18-month study period. A total of 7 MCF deaths was reported from 2 large herds within 1.0 km of sheep operations. Although there was a greater risk of MCF deaths in bison herds within 1.0 km of sheep operations than in herds more than 1.0 km away, the overall incidence of MCF deaths within the study period was very low. Most deaths were attributed to non-infectious causes, including copper deficiency.

Alcelaphine Herpesvirus-1 (Malignant Catarrhal Fever Virus) in Wildebeest Placenta: Genetic Variation of ORF50 and A9.5 Alleles

Alcelaphine herpesvirus–1 (AlHV-1), a causative agent of malignant catarrhal fever in cattle, was detected in wildebeest (Connochaetes taurinus) placenta tissue for the first time. Although viral load was low, the finding of viral DNA in over 50% of 94 samples tested lends support to the possibility that placental tissue could play a role in disease transmission and that wildebeest calves are infected in utero. Two viral loci were sequenced to examine variation among virus samples obtained from wildebeest and cattle: the ORF50 gene, encoding the lytic cycle transactivator protein, and the A9.5 gene, encoding a novel polymorphic viral glycoprotein. ORF50 was well conserved with six newly discovered alleles differing at only one or two base positions. In contrast, while only three new A9.5 alleles were discovered, these differed by up to 13% at the nucleotide level and up to 20% at the amino acid level. Structural homology searching performed with the additional A9.5 sequences determined in this study adds power to recent analysis identifying the four-helix bundle cytokine interleukin-4 (IL4) as the major homologue. The majority of MCF virus samples obtained from Tanzanian cattle and wildebeest encoded A9.5 polypeptides identical to the previously characterized A9.5 allele present in the laboratory maintained AlHV-1 C500 strain. This supports the view that AlHV-1 C500 is suitable for the development of a vaccine for wildebeest-associated MCF.

The economic impact of malignant catarrhal fever on pastoralist livelihoods

This study is the first to partially quantify the potential economic benefits that a vaccine, effective at protecting cattle against malignant catarrhal fever (MCF), could accrue to pastoralists living in East Africa. The benefits would result from the removal of household resource and management costs that are traditionally incurred avoiding the disease. MCF, a fatal disease of cattle caused by a virus transmitted from wildebeest calves, has plagued Maasai communities in East Africa for generations. The threat of the disease forces the Maasai to move cattle to less productive grazing areas to avoid wildebeest during calving season when forage quality is critical. To assess the management and resource costs associated with moving, we used household survey data. To estimate the costs associated with changes in livestock body condition that result from being herded away from wildebeest calving grounds, we exploited an ongoing MCF vaccine field trial and we used a hedonic price regression, a statistical model that allows estimation of the marginal contribution of a good's attributes to its market price. We found that 90 percent of households move, on average, 82 percent of all cattle away from home to avoid MCF. In doing so, a herd's productive contributions to the household was reduced, with 64 percent of milk being unavailable for sale or consumption by the family members remaining at the boma (the children, women, and the elderly). In contrast cattle that remained on the wildebeest calving grounds during the calving season (and survived MCF) remained fully productive to the family and gained body condition compared to cattle that moved away. This gain was, however, short-lived. We estimated the market value of these condition gains and losses using hedonic regression. The value of a vaccine for MCF is the removal of the costs incurred in avoiding the disease.

Malignant catarrhal fever: understanding molecular diagnostics in context of epidemiology

Malignant catarrhal fever (MCF) is a frequently fatal disease, primarily of ruminants, caused by a group of gammaherpesviruses. Due to complexities of pathogenesis and epidemiology in various species, which are either clinically-susceptible or reservoir hosts, veterinary clinicians face significant challenges in laboratory diagnostics. The recent development of specific assays for viral DNA and antibodies has expanded and improved the inventory of laboratory tests and opened new opportunities for use of MCF diagnostics. Issues related to understanding and implementing appropriate assays for specific diagnostic needs must be addressed in order to take advantage of molecular diagnostics in the laboratory.

Long distance spread of malignant catarrhal fever virus from feedlot lambs to ranch bison

Malignant catarrhal fever (MCF) caused by OvHV-2 occurred in ranch bison herds separated by significant distances from feedlot lambs. Mortality rates correlated with distances: 17.5%, 6.1%, and 0.43% at approximately 1.6, 4.2, and 5.1 km, respectively. The study further defines the importance of distance of species separation for MCF control.

Malignant catarrhal fever associated with ovine herpesvirus-2 in free-ranging mule deer in Colorado

Malignant catarrhal fever (MCF) was diagnosed in four free-ranging mule deer (Odocoileus hemionus) in January and February of 2003. Diagnosis was based on typical histologic lesions of lymphocytic vasculitis and PCR identification of ovine herpesvirus-2 (OHV-2) viral genetic sequences in formalin-fixed tissues. The animals were from the Uncompahgre Plateau of southwestern Colorado. Deer from these herds occasionally resided in close proximity to domestic sheep (Ovis aries), the reservoir host of OHV-2, in agricultural valleys adjacent to their winter range. These cases indicate that fatal OHV-2 associated MCF can occur in free-ranging mule deer exposed to domestic sheep that overlap their range.

[Large outbreak of malignant catarrhal fever in cattle]

The prevalence of clinical malignant catarrhal fever (MCF) is low in the Netherlands, and at a farm level the disease is usually restricted to a single animal. This casereport describes an outbreak of MCF that killed 18 animals (39% of the cattle on the farm). The probable source of infection were 10 hand-reared lambs that were on the farm for a few months.

Malignant catarrhal fever in free-ranging cervids associated with OvHV-2 and CpHV-2 DNA

Pathologic lesions were summarized in 18 free-ranging cervids (15 moose [Alces alces], two roe deer [Capreolus capreolus], and one red deer [Cervus elaphus]) diagnosed with malignant catarrhal fever (MCF) after examination at the National Veterinary Institute, Oslo 1982-2005. Eye lesions (conjunctivitis, corneal opacity, fibrin clots in the anterior eye chamber) were the most frequent gross finding. Erosive-ulcerative mucosal lesions in the nose and mouth were also commonly found. Histopathology revealed a nonpurulent vasculitis and perivasculitis in the central nervous system (CNS) typical of MCF in 16 of the cases. The diagnosis in the remaining two animals was based upon histologic eye lesions consistent with MCF (CNS not available for examination). Polymerase chain reaction was run on samples from 15 individuals for evidence of MCF-virus DNA, and ovine herpesvirus-2 (OvHV-2) DNA was detected in five moose, one roe deer, and one red deer, and caprine herpesvirus-2 (CpHV-2) DNA was detected in two moose and one roe deer. Sera from 1,000 free-ranging cervids were tested for specific antibodies to MCF-associated viruses (MCFV) by competitive inhibition enzyme-linked immunosorbent assay. The seroprevalences were: red deer 5%, reindeer (Rangifer tarandus) 4%, roe deer 2%, and moose 0.4% (n = 250 for all four species). The results indicate that sheep and goat MCFV may cause serious disease in wild moose, roe deer, and red deer. The seropositive cervids most likely represent individuals infected with either OvHV-2 or CpHV-2, but may also reflect infections with other related MCFV.

A devastating outbreak of malignant catarrhal fever in a bison feedlot

In early 2003, an outbreak of malignant catarrhal fever (MCF) occurred in a bison feedlot in southern Idaho. The outbreak resulted in a 51.2% (n = 825) mortality rate among bison, which had been exposed to sheep for 19 days. Diagnosis was made by detection of ovine herpesvirus 2 (sheep-associated MCF virus) DNA in tissues or peripheral blood by polymerase chain reaction (PCR), and by histological examination of tissue lesions. Peak losses occurred between 41 and 55 days postmean exposure time (PME), and reached a maximum of 41 head per day. No known cases of MCF were observed among the 177 head of bison that arrived in the lot 3 1/2 weeks after the departure of the sheep. Of the several thousand head of beef cattle in the lot during the outbreak, only a single case of MCF was identified. This outbreak illustrates the devastating impact the MCF virus can have on bison under certain exposure conditions, the high threat posed by adolescent lambs to susceptible species, the significantly greater susceptibility of bison than beef cattle to MCF, and the lack of horizontal transmission from clinically affected bison to herdmates.

Molecular epidemiology of ovine herpesvirus type 2 infection in Kashmir, India

The aims of this investigation were to determine the prevalence of ovine herpesvirus type 2 (OvHV-2) (the causative agent of malignant catarrhal fever) infection in cattle, the carrier status of sheep and goats, and to define the pattern of acquisition of OvHV-2 in lambs under natural flock conditions in Kashmir, India. None of the buffy coat samples from 21 lambs contained OvHV-2 DNA sequences up to 28 days after birth, only one lamb had sequences of OvHV-2 DNA as early as 29 days after birth, and they were detected in the other 20 lambs when they were between 43 and 94 days of age. Sequences of OvHV-2 DNA were detected in buffy coat samples from 28 (85 per cent) of 33 adult sheep and in 16 (61 per cent) of 26 samples from adult goats by hemi-nested PCR. Seventeen (31 per cent) of 55 cattle with malignant catarrhal fever-like clinical signs had sequences of OvHV-2 DNA in their blood, and nine of the 17 died, all of them during the months of April to November, between November 2002 and March 2004. No clinical cases of sheep-associated malignant catarrhal fever was recorded during the months of December to March. The overall prevalence of OvHV-2 infection in the cattle in the region was estimated to be less than 1 per cent.

Maasai perception of the impact and incidence of malignant catarrhal fever (MCF) in southern Kenya

We investigated the perceived impact of malignant catarrhal fever (MCF) to pastoralists in Isinya Division, a wildlife dispersal area of Nairobi National Park, and used a range of participatory epidemiology methodologies. We compared the relative importance, incidence and impact of MCF compared to other locally defined important diseases with a total of 158 respondents in 11 group meetings and 21 household meetings in July 2004. Direct losses due to disease were investigated through lowered prices as a result of the emergency sale of disease-infected animals. Overall, Maasai in Isinya Division perceived east coast fever (ECF) to be the most important cattle disease and to have the highest incidence. Anthrax was considered to have the largest impact. In areas within or adjacent to the wildebeest calving zone, MCF was perceived to be the most important cattle disease and also to have the largest impact. Outside the calving zone, MCF was considered the fourth-most important disease with the fourth largest impact, and these were areas where wildebeest were less common. MCF was also the fourth-most common disease, and across the Division incidence was estimated at 5% in calves and 10% in adults. However, MCF incidence varied greatly throughout the study area, from 3% to 12%, and the highest incidence risks were found in areas where wildebeest came to calve. The percent drop in sale price per animal infected with MCF was estimated at 50% for MCF for the year 2003-2004. Forced avoidance movements away from wildebeest calves were reported to decrease livestock production due to loss of access to prime grazing sites. As suggested by pastoralists in this study, the development of compensation schemes or incentives from wildlife would reduce the conflict between livestock keeping and wildlife conservation.

Malignant catarrhal fever in pigs and a genetic comparison of porcine and ruminant virus isolates in Finland

An outbreak of the sheep-associated form of malignant catarrhal fever (MCF) in a Finnish sow herd was diagnosed by histopathology and confirmed by PCR. Several gilts and sows were suffering from high fever and anorexia and had aborted, and six of them had died. Typical signs of lymphoproliferation and vasculitis were observed histologically in several tissues, including the uterus. Ovine herpesvirus-2 (OvHV-2) was detected by PCR in two sows. Sequences of the OvHV-2 tegument protein gene obtained from the sows and from three cases of sheep-associated mcf in Finnish cattle were compared and found to be identical. These are the first confirmed cases of mcf in pigs in Finland.

Occurrence of ovine herpesvirus type-2 infection in sheep and cattle in Samsun Province, Turkey

July 2004, a cow with clinical signs of ovine herpesvirus type-2 infection which is known as sheep associated malignant catarrhal fever (SA-MCF) was reported in Samsun Province in Turkey. Blood samples were collected from the suspected cow, 10 sheep housed with it, and from 150 healthy sheep and 29 healthy cattle randomly selected from different places in Samsun Province. Nested polymerase chain reaction (n-PCR) was used to detect ovine herpesvirus type-2 (OvHV-2) DNA in the suspected cow and competitive- ELISA (c-ELISA) kits were used to detect antibodies against OvHV-2. The suspected cow was found to be n-PCR positive and c-ELISA negative. The serological results were as follows: All 10 (100%) of sheep housed with the suspected cow and 18 of 29 (62%) of the randomly selected cattle were found seropositive. All 150 randomly selected healthy sheep were seronegative. The overall percentage of seropositivity was 14.7% (28/190). OvHV-2 DNA was detected in the peripheral blood leucocyte (PBL) samples of the cow and of the 10 sheep housed with the suspected cow.

Evidence of Three New Members of Malignant Catarrhal Fever Virus Group in Muskox (Ovibos moschatus), Nubian ibex (Capra nubiana), and Gemsbok (Oryx gazella)

Six members of the malignant catarrhal fever (MCF) virus group of ruminant rhadinoviruses have been identified to date. Four of these viruses are clearly associated with clinical disease: alcelaphine herpesvirus 1 (AlHV-1) carried by wildebeest (Connochaetes spp.); ovine herpesvirus 2 (OvHV-2), ubiquitous in domestic sheep; caprine herpesvirus 2 (CpHV-2), endemic in domestic goats; and the virus of unknown origin found causing classic MCF in white-tailed deer (Odocoileus virginianus; MCFV-WTD). Using serology and polymerase chain reaction with (degenerate primers targeting a portion of the herpesviral DNA polymerase gene, evidence of three previously unrecognized rhadinoviruses in the MCF virus group was found in muskox (Ovibos moschatus), Nubian ibex (Capra nubiana), and gemsbok (South African oryx, Oryx gazella), respectively. Base on sequence alignment, the viral sequence in the muskox is most closely related to MCFV-WTD (81.5% sequence identity) and that in the Nubian ibex is closest to CpHV-2 (89.3% identity). The viral sequence in the gemsbok is most closely related to AlHV-1 (85.1% identity). No evidence of disease association with these viruses has been found.

Sheep-associated malignant catarrhal fever involving 3-5-week-old calves in Saudi Arabia

Between late December 1999 and late April 2000, three locally bred Friesian calves (ageing 25, 28 and 35 days) in a dairy farm, at Al-Ahsa locality of the eastern region of Saudi Arabia showed dullness and inappetence. Their rectal temperatures ranged between 41 and 41.5 degrees C. One to 2 days later and onwards, the calves showed lacrimation, nasal discharge, salivation, oedema of the head, conjunctivitis, exo-ophthalmia and corneal opacity. One calf showed diarrhoea. The superficial lymph nodes were oedematous and swollen. The calves died after 7, 5 and 8 days, respectively, following the onset of the disease. Calves and rabbits were experimentally infected with materials from the naturally infected calves. The rabbits showed fever, mild conjunctivitis and one rabbit showed wet faeces. The experimentally inoculated calves showed rise in temperature and mild symptoms but none of them died. The virus from the naturally infected calves and from the experimentally infected rabbits was identified as malignant catarrhal fever (MCF) virus using both the complement fixation test and the fluorescent antibody test, employing a reference anti-serum against the WC 11 strain of MCF virus. Serological survey for MCF antibodies in cattle, sheep and goats from the affected farm revealed that 54% of the examined animals were positive. The situation of MCF in Saudi Arabia was discussed in relation to sheep and wild game. This paper constitutes the first report of MCF in Saudi Arabia and the Gulf region.

[Porcine malignant catarrhal fever: diagnostic findings and first detection of the pathogenic agent in diseased swine in Switzerland]

For the first time Ovine Herpesvirus 2 (OvHV-2) was identified in Swiss pigs as the causative agent of Porcine Malignant Catarrhal Fever (MCF). Diseased animals from two farms were observed to show weakness, anorexia, fever up to 41 degrees C, and neurological symptoms, i.e. ataxia, convulsions and hyperesthesia, erosion on the snout and in the oral and nasal mucosa, as well as multiple skin lesions. Histopathological findings included severe non-purulent inflammation with mononuclear cell infiltration in several organs. Most dominant were meningo-encephalitis, disseminated nephritis as well as purulent catarrhalic bronchopneumonia. The findings were quite reminiscent of the lesions due to MCF in cattle and give therefore substantial proof to use Porcine Malignant Catarrhal Fever as the term for the disease. Identification of the causative agent was done with a quantitative PCR specific for OvHV-2. Different tissues from diseased animals were positive. Furthermore, one animal which had been ill for more than five days tested positive for antibodies against an epitope conserved among MCF viruses. Serum samples from diseased animals reacted negative towards Classical Swine Fever- and Pseudorabies virus antigen. A weakly positive reaction against porcine enterovirus type I argued against the involvement of enteroviruses in the observed disease. Moreover, by means of different conventional PCRs, we detected the newly discovered porcine lymphotropic herpesviruses for the first time in Switzerland and could at the same time exclude their involvement in Porcine Malignant Catarrhal Fever.

Outbreak of malignant catarrhal fever in Welsh Black cattle in Carmarthenshire

An outbreak of malignant catarrhal fever (MCF) resulted in the deaths of 12 cattle in a herd of 77 animals during seven weeks in 1999; in addition, one cow developed a milder disease which was confirmed as MCF by PCR for ovine herpesvirus 2 DNA and an immunofluorescent antibody test for antibodies to the virus, but recovered. Further PCR and serological testing revealed the infection in three other animals, none of which developed clinical disease. Hypocuprosis and the possibility of a genetic predisposition were identified as factors which may have contributed to the outbreak.

Malignant catarrhal fever-like disease in Barbary red deer (Cervus elaphus barbarus) naturally infected with a virus resembling alcelaphine herpesvirus 2

Eight Barbary red deer (Cervus elaphus barbarus) developed clinical signs suggestive of malignant catarrhal fever (MCF) over a 28-day period. These animals were housed outdoors with four other species of ruminants. Affected red deer had lethargy, ocular signs, and nasal discharge and were euthanatized within 48 h. Lesions included ulcers of the muzzle, lips, and oral cavity associated with infiltrates of neutrophils and lymphocytes. Serologically, six of seven red deer tested during the outbreak were positive by competitive enzyme-linked immunosorbent assay for antibodies to a shared MCF virus antigen. PCR using oligonucleotide primers designed for a conserved protein of alcelaphine herpesviruses 1 (AlHV-1) and 2 (AlHV-2) and for conserved regions of a herpesvirus DNA polymerase gene was positive for tissues from all eight clinically affected animals and negative for eight out of eight red deer without clinical signs of MCF. DNA sequencing of PCR amplicons from the diseased red deer indicated that they were infected with a novel herpesvirus closely related to AlHV-2; immunohistochemistry using polyclonal anti-AlHV-2 serum and in situ hybridization demonstrated the presence of virus within salivary glands adjacent to oral lesions of affected animals. A survey of other ruminants near the outbreak subsequently showed that normal Jackson's hartebeest (Alcelaphus buselaphus jacksoni) that were cohoused with the diseased red deer were infected with the same virus and were shedding the virus in nasal excretions. These findings suggest that a herpesvirus closely related to AlHV-2 caused the MCF-like disease epizootic in Barbary red deer and that the virus may have originated from Jackson's hartebeest.

Serum antibody prevalence of malignant catarrhal fever viruses in seven wildlife species from Alaska

Blood samples were collected from seven species of free-ranging ungulates in Alaska. Sera were tested for evidence of exposure to malignant catarrhal fever viruses (MCFV) by means of a competitive enzyme-linked immunosorbent assay. Antibody prevalences were as follows: muskox (Ovibos moschatus) 100 positive samples of 104 tested (96%); Dall sheep (Ovis dalli) 212 of 222 (95%); elk (Cervus elaphus) 14 of 51 (27%); bison (Bison bison) 34 of 197 (17%); caribou (Rangifer tarandus) nine of 232 (4%); Sitka black-tailed deer (Odocoileus hemionus sitkensis) one of 49 (2%); and moose (Alces alces) three of 219 (1%). Antibody prevalence in a bison population from the Interior was stable over a 5 yr period. These results indicate that at least one virus in the MCF group is enzootic in Dall sheep and muskox in Alaska. Lower antibody prevalences in the other species in this survey suggest that MCFV are latent or subclinical in these free-ranging ruminants. Whole blood samples were collected from 14 Dall sheep and subjected to a polymerase chain reaction assay. Fragments of ovine herpesvirus-2 DNA were detected in six of the samples. The significance of these findings for the health of free-ranging ungulates in Alaska is unknown.

Malignant catarrhal fever in a bison (Bison bison) feedlot, 1993-2000

A fatal enteric syndrome was identified in American bison (Bison bison) at a large feedlot in the American Midwest in early 1998. An estimated 150 bison died of the syndrome between January 1998 and December 1999. The syndrome was identified as malignant catarrhal fever (MCF), primarily the alimentary form. Clinical onset was acute, and most affected bison died within 1-3 days; none recovered. Consistent lesions were hemorrhagic cystitis, ulcerative enterotyphlocolitis, and arteritis-phlebitis. Vasculitis was milder and more localized than that in cattle with MCF, and in contrast to the situation in cattle, lymphadenomegaly was minimal. Virtually all affected bison examined were positive for ovine herpesvirus 2 (OvHV-2) by polymerase chain reaction (PCR) assay. A retrospective study of archived tissues established that MCF occurred in the yard as early as 1993. A prospective study was undertaken to establish the importance of MCF relative to other fatal diseases at the feedlot. The fate of a group of 300 healthy male bison in a consignment of 1,101 animals was followed for up to 7 months to slaughter. At entry, 23% (71/300) of bison were seropositive for MCF viruses, and 11% (8/71) of these seropositive bison were PCR positive for OvHV-2. Forty seronegative bison were selected at random from the group, and all were PCR negative for OvHV-2. There was no change in seroprevalence in the group during the investigation. The minimum infection rate for MCF virus was 36.3% (93/256). Twenty-two (7.3%) of the 300 bison in the feedlot died. Of these, 15 had MCF, 4 had acute or chronic pneumonia, and 3 were unexamined. Losses in the entire consignment were higher (98/1,101; 8.8% death loss); 76% of deaths were attributable to MCF. The study failed to reveal a relationship between subclinical infection and development of clinical disease.

[Malignant catarrhal fever in Switzerland. 1.Epidemiology]

Malignant catarrhal fever (MCF) is a usually fatal infectious disease of cattle with global distribution. Based on the recent introduction of a diagnostic PCR assay and a competitive inhibition ELISA (ciELISA) epidemiological data were collected on field cases in Switzerland. Throughout a three-year period, an MCF incidence of 0.6@1000 was observed, with a gradient of cases from Eastern to Western Switzerland. While the cantons Wallis, Vaud and Geneva reported no and the remaining western cantons only reported a few cases, the highest incidence was observed in the cantons Appenzell Innerrhoden, Lucern, Glarus, Grison, St. Gallen, Schwyz, and Thurgau. MCF occurred seasonally and an age-related clustering was also observed. About 50% of all cases and all outbreaks with more than one animal in a single herd occurred between April and June. Animals between six months and two years were strongly over represented. Observations on four surviving cattle showed that the outcome of the disease is not invariably fatal and that these persistently infected cows can produce healthy negative calves. Investigations on the aetiology indicate that the main reservoir for OvHV-2 is in sheep and possibly goats, while cattle do not normally harbor the virus. An OvHV-2 negative sheep herd was raised from lambs, which were reared colostrum-free and in isolation from their mothers. The success rate clearly indicated that vertical intrauterine infection is not the main mode of transmission among sheep. Therefore, horizontal, seasonally occurring transmission of OvHV-2 among sheep has to be assumed.

Recognition of another member of the malignant catarrhal fever virus group: an endemic gammaherpesvirus in domestic goats

A novel gammaherpesvirus in goats that is herein tentatively designated as caprine herpesvirus-2 was identified based on the sequence of a fragment from the herpesvirus DNA polymerase gene. Sequence alignment analysis revealed that the virus sequence isolated from goats was 67% identical to the homologous sequence from alcelaphine herpesvirus-1, 71% identical to ovine herpesvirus-2 and 73% identical to a recently recognized herpesvirus causing malignant catarrhal fever in white-tailed deer. Combined serological and PCR-survey data demonstrated that this virus is endemic in goats and its transmission pattern may be similar to that of ovine herpesvirus-2 in sheep.

Epizootic malignant catarrhal fever in three bison herds: differences from cattle and association with ovine herpesvirus-2

Three bison herds in Colorado experienced high mortality from malignant catarrhal fever (MCF). In comparison with cattle, the bison had a more rapidly progressive disease, fewer clinical signs, and milder inflammatory histologic lesions. There was consistent association with ovine herpesvirus-2 (OHV-2). Contact with sheep was not consistent. Of 17 animals in herd A, 15 died of acute MCF; 1 was slaughtered while healthy; and 1 developed clinical signs of MCF, was treated with corticosteroids and antibiotics, and died of fungal abomasitis and rhinitis after 5 months. In herds B and C, approximately 300 of 900 and 18 of 20 died of MCF following brief clinical disease. The nearest sheep were 1 mile away from herd A, but direct contact with sheep could be documented in herds B and C. Complete gross and histologic examinations were conducted on 34 animals, including all animals in herd A, and MCF was diagnosed in 31. In addition, field necropsies were performed on all dead animals in herd B and most in herd C and MCF was diagnosed on the basis of the gross lesions in most animals. Clinical signs of each animal in herd A were recorded. Illness was brief, usually 8-48 hours. Clinical signs were subtle; separation from the herd was often observed. In all 3 herds, hemorrhagic cystitis and multifocal ulceration of the alimentary tract were consistently found at necropsy. Mild lymphocytic vasculitis was present in multiple organs. Ovine herpesvirus-2 was found by polymerase chain reaction (PCR) in 71 of 105 formalin-fixed tissue specimens from 29 of 31 animals with MCF. In herd A, blood samples from 13 animals were collected at 5 time points and tested by PCR for the presence of OHV-2 viral sequences in peripheral blood leukocytes. Nine bison with a positive PCR test and 4 with negative results prior to clinical illness died of MCF.

Sheep-associated malignant catarrhal fever in a petting zoo

In a privately owned petting zoo in Arizona, 17 deer from five different species, white-tailed deer (Odocoileus virginianus), Reeve's muntjac (Muntiacus reevesi), mule deer (Odocoileus hemionus), reindeer (Rangifer tarandus), and axis deer (Axis axis), died of suspected malignant catarrhal fever (MCF) over a period from late 1992 to early 1995. A PCR assay specific for ovine herpesvirus 2, the putative causative agent of sheep-associated MCF, and a competitive-inhibition enzyme-linked immunosorbent assay based on a monoclonal antibody specific to an epitope conserved among all known MCF viral isolates were used to investigate the outbreak. Ovine herpesvirus 2 DNA sequences were detected by PCR from fresh-frozen and/or formalin-fixed, paraffin-embedded tissue samples in seven deer out of eight available animals previously suspected as cases by histopathology. A high seroprevalence to the virus was found among mouflon (Ovis musimon, 80%) and pygmy goats (Capra hircus, 61%), both of which were present on the farm during the outbreak. Sixteen percent of fallow deer (Dama dama) were also seropositive to the virus. After removal of the mouflon and positive pygmy goats, no further MCF cases occurred on the farm, confirming the importance of careful management to avoid mixing clinically susceptible species with carrier species. Until better control measures are available, adherence to this practice is necessary if MCF is to be prevented in intense exposure environments such as zoos and densely populated animal parks.

Malignant catarrhal fever caused by ovine herpesvirus-2 in pigs in Norway

This paper describes the first cases of malignant catarrhal fever (MCF) in pigs in which the diagnosis was verified aetiologically by polymerase chain reaction (PCR) and DNA analysis and by the demonstration of antibodies. Three pigs on two separate premises showed clinical signs, gross pathological and histopathological lesions which were in many respects similar to those of MCF in ruminants. The pigs were housed adjacent to sheep and DNA of ovine herpesvirus-2 (OHV-2) was detected by PCR in tissues of all the pigs. In addition, antibody to alcelaphine herpesvirus-1 was detected in the serum of the pigs and in five in-contact sheep. It is concluded that the disease described is MCF of pigs caused by OHV-2.

Serosurvey for antibodies to malignant catarrhal fever-associated viruses in free-living and captive cervids in Germany

A total of 486 serum samples collected from several species of both free-living and captive cervids in Germany was examined for antibodies against malignant catarrhal fever (MCF)-associated viruses (MCFV) by a competitive-inhibition enzyme-linked immunosorbent assay (CI-ELISA). Eleven (2%) of these samples were positive for antibodies against MCFV. Among 157 serum samples collected from 16 different species of captive deer including four (7%) of 54 fallow deer and one (7%) of 14 sika deer (Cervus nippon) were seropositive. Among 329 samples from three species of free-ranging deer, including 253 roe deer (Capreolus capreolus), 22 red deer (Cervus elaphus) and 54 fallow deer (Cervus dama), only fallow deer were antibody-positive. Of the 25 fallow deer samples collected between 1990 and 1993, four (16%) were seropositive. Among 29 free-ranging fallow deer samples collected in the hunting period 1996-1997, antibodies to MCFV were detected in two (7%) of these sera. All of these fallow deer samples were collected from a circumscribed area in northern Germany. In the same area a high seroprevalence (72%) to MCFV was observed in domestic sheep (n = 50). Among 20 sheep samples (buffy coat) and 15 fallow deer samples (spleen or lymph nodes) examined for ovine herpesvirus 2 (OvHV-2) by PCR, all 20 sheep samples examined were OvHV-2 positive, but all of the 15 fallow deer samples, including seven seropositive deer, were OvHV-2 negative.

[Malignant catarrhal fever in zoo ruminants]

An outbreak of malignant catarrhal fever (MCF) in Indian gauer (Bos gaurus gaurus) and Javan banteng (Bos javanicus javanicus) occurred in the year 1964 and killed almost all animals of the groups of these species kept at the Munich zoo at that time. In the consecutive years at highly irregular intervals cases of the head-and-eye-form of MCF occurred sporadically at the zoo in European and American bison (Bison bonasus, B. bison' bison, B. bison athabascae), elk (Alces alces), red deer (Cervus elaphus), Père David's deer (Elaphurus davidianus) and again in gaur and banteng. The clinical and pathomorphological observations, including those of prophylactic and tentative treatment are reported. The subspecies of caprinae and alcelaphinae potentionally latently infected with viral agents of MCF kept at the zoo over the reported period are listed. Some details concerning housing, taking care of the animals etc. of the latently infected carriers of the family caprinae and the susceptible species of bovidae and cervidae are also given as far as they are of epidemiological interest. The results of the retrospective analysis and the results of testing paraffin-embedded tissue samples for the presence of ovine herpesvirus-2 (OHV-2)-specific DNA and alcelaphine herpesvirus-1 (AHV-1)-specific DNA from 1964 up to 1997 are discussed. The negative results for OHV-2-specific DNA suggest that MCF at Munich zoo until 1979 could have been "wildebeest-associated", also because until 1974 blue wildebeest (Connochaetes taurinus taurinus) and until 1983 white-tailed gnu (Connochaetes gnou) were kept. However, positive results for OHV-2-specific DNA in the tissues collected from 1985 onwards, strongly suggest the "sheep-associated" MCF.

An outbreak of malignant catarrhal fever in young rusa deer (Cervus timorensis)

On the basis of clinical signs and histological findings eight 9-month-old male rusa deer (Cervus timorensis) were diagnosed with sheep associated-malignant catarrhal fever. Following a variable course involving rectal temperatures around 40.5 degrees C, depression, inappetence, diarrhoea, corneal opacity and hypopyon all animals died or were euthanased over a 5-week period. Severe multifocal vasculitis, mainly periglomerular and in the arcuate vessels were consistent histological findings which in the past have been adequate to confirm clinical diagnosis of sheep associated-malignant catarrhal fever. A nested polymerase chain reaction test has been used to detect a sheep associated-malignant catarrhal fever PRC product, 238 base-pairs in size, in DNA extracted from lymphocyte preparations. The result supported the diagnosis of sheep associated-malignant catarrhal fever in these deer.

Molecular and clinicopathological diagnosis of malignant catarrhal fever in cattle, deer and buffalo in New Zealand

Fresh and formalin-fixed tissues and blood samples in ethylenediaminetetraacetate were collected from cattle, deer and buffalo with clinical signs suggestive of malignant catarrhal fever (MCF). In addition, formalin-fixed, paraffin-embedded tissue blocks collected from these animals and retrospectively from field cases of MCF were examined. DNA samples extracted from these samples were analysed by polymerase chain reaction (PCR) assay using primers specific for the sheep-associated (SA)- and wildebeest-associated (WA)-MCF viruses. Both the SA-MCF virus and WA-MCF virus PCR yielded positive results which were in nearly complete agreement with the histopathological diagnoses of MCF in fresh and formalin-fixed, paraffin-embedded tissue from 29 cattle, 24 deer and three buffaloes. Some blood samples tested by the two assays indicated that some of the infected cattle were possible carriers.

Prevalence of antibody to malignant catarrhal fever virus in wild and domestic ruminants by competitive-inhibition ELISA

A competitive-inhibition ELISA (CI-ELISA), based on a monoclonal antibody to an epitope conserved among malignant catarrhal fever virus (MCFV) strains of both wildebeest and sheep origin, was used to determine the prevalence of antibody to MCFV in selected domestic and wild ruminants, both free-ranging and captive, from the USA. We evaluated 2528 sera from 14 species between 1990 and 1995, including 80 pronghorn antelope (Antilocapra americana), 339 bighorn sheep (Ovis canadensis), 103 biston (Bison bison), 17 black-tailed deer (Odocoileus hemionus columbianus), 395 domestic cattle (Bos taurus), 291 domestic goats (Capra hircus), 680 domestic sheep (Ovis ammon), 323 elk (Cervus elaphus), 41 llamas (Lama glama), 21 mouflon sheep (Ovis musimon), 54 mountain goats (Oreamnos americanus), 101 mule deer (Odocoileus hemionus), 20 muskox (Ovibos moschatus), and 63 white-tailed deer (Odocoileus virginianus). A high seroprevalence (37 to 62%) was observed in domestic sheep, domestic goats, muskox, and some bighorn sheep populations. Seroprevalence in these species was generally age-related: a very low seroprevalence was present in these animals under one year of age. A low seroprevalence (2% to 13%) was found in clinically-susceptible species such as domestic cattle, deer, elk and bison, supporting the concept that significant numbers of non-lethal infections occur among clinically susceptible ruminants.

Chronic generalized obliterative arteriopathy in cattle: a sequel to sheep-associated malignant catarrhal fever

Malignant catarrhal fever (MCF) in cattle is generally associated with a short clinical course and a high case fatality rate (90-95%). The lesions in cattle that survive acute MCF for a prolonged period or appear to recover have not been documented. In a naturally occurring outbreak of MCF in a herd of beef cattle in Wyoming, 7 of 84 yearling heifers (8.3% of replacement herd) and 2 of 230 cows (0.9% of cow herd) developed clinical signs of pyrexia, mucopurulent discharge, bilateral keratitis, and weight loss following contact with ewes that had lambed 34-62 days earlier. Six of 9 affected cattle were examined postmortem following clinical signs (CS) that developed 2-150 days earlier. Three cattle with CS for < or = 39 days had lesions of regional lymphadenopathy and widespread severe segmental lymphoid arteritis-phlebitis that were typical of acute MCF, and proliferative intimal lesions were present in a small proportion of arteries at days 20 and 39 of CS. By contrast, 3 cattle that survived to 90, 105, and 150 days after clinical onset had distinctive arterial lesions in multiple organs, characterized by proliferative concentric fibrointimal plaques, disrupted inner elastic lamina, focally atrophic tunica media, and vasculitis of variable severity. Immunohistochemical and ultrastructural examination of intimal plaques identified the predominant cellular component to be smooth muscle cells with a contractile phenotype. No viral structures were seen. Serologic studies, using a competitive inhibition enzyme-linked immunosorbent assay (CI-ELISA) that detects antibody to an epitope broadly conserved among isolates of the MCF virus, found that 2 chronically affected cattle were serologically positive between days 42 and 100 of CS, with seroconversion in 1 animal between days 52 and 73 of CS. Seroprevalence was 7.9% in the 76 remaining healthy animals of the replacement heifer herd and 40% (75% in adult sheep and 4% in lambs) in the in-contact sheep flock 77 days after onset of CS in the index case. This episode suggests that, in addition to the common and well recognized acute form of MCF in cattle, this viral infection encompasses a disease spectrum that includes chronic disease and partial to "complete" clinical recovery, and in recovered animals chronic obliterative arteriopathy is the preeminent lesion.