Field observations during the bluetongue serotype 8 epidemic in 2006. I. Detection of first outbreaks and clinical signs in sheep and cattle in Belgium, France and the Netherlands

Starting August 2006, a major epidemic of bluetongue (BT) was identified in North-West Europe, affecting The Netherlands, Belgium, Germany, Luxemburg and the North of France. It was caused by BT virus serotype 8 (BTV-8), a serotype previously unknown to the European Union (EU). In this outbreak, the virus caused clinical disease in a few individual animals within cattle herds, whereas overt clinical disease was usually restricted to sheep. Investigations in Belgium suggested that the first clinical signs of BTV-8 appeared mid July 2006 in a cattle herd, while the first suspicion of a BT-outbreak in Belgium was reported on 17 August 2006. In the first 10 BTV-8 outbreaks in the Netherlands, the owners indicated that the first clinical signs started approximately 12-17 days before a suspicion was reported to the veterinary authorities via a veterinary practitioner. In BTV-8 affected sheep flocks, erosions of the oral mucosa, fever, salivation, facial and mandibular oedema, apathy and tiredness, mortality, oedema of the lips, lameness, and dysphagia were among the most frequent clinical signs recorded. The most prominent clinical signs in BTV-8 affected cattle herds were: crusts/lesions of the nasal mucosa, erosions of lips/crusts in or around the nostrils, erosions of the oral mucosa, salivation, fever, conjunctivitis, coronitis, muscle necrosis, and stiffness of the limbs. Crusts/lesions of nasal mucosa, conjunctivitis, hyperaemic/purple coloration and lesions of the teats, and redness/hypersensitivity of the skin were relatively more seen on outbreak farms with cattle compared to sheep. Mortality, oedema of the head and ears, coronitis, redness of the oral mucosa, erosions/ulceration of tongue mucosa, purple coloration of the tongue and tongue protrusion and dyspneu were relatively more seen on outbreak farms with sheep compared to cattle.     

Bluetongue and related viruses in Nigeria: Experimental infection of West African dwarf sheep with Nigeria strains of the viruses of epizootic haemorrhagic disease of deer and bluetongue

West African dwarf sheep were inoculated by the subcutaneous route with epizootic haemorrhagic disease of deer (EHD) virus or bluetongue (BT) virus. No clinical disease was observed following primary EHD or BT infection, or subsequent challenge with either homologous or heterologous virus. However, viraemia was detected in non-immune sheep exposed to BT virus, but not in BT- or EHD-immune sheep challenged with either virus, or in non-immune sheep exposed to primary EHD virus infection. Complement fixing antibodies developed against both EHD and BT viruses following the primary infection with either virus, or subsequent challenge with homologous or heterologous virus. Following a primary infection, virus-neutralising (VN) antibodies developed only against the inoculated virus, while the detection of VN antibodied to both viruses followed the challenge of an EHD- or BT-immuned sheep with either the homologous or heterologous virus. These findings further support previous reports of a relationship between EHD and BT viruses. between EHD and BT viruses.     

Nonlethal experimental inoculation of Columbia black-tailed deer (Odocoileus hemionus columbianus) with virus of epizootic hemorrhagic deer disease.

Intramuscular or intravenous inoculation of 5 Columbia black-tailed deer (Odocoileus hemionus columbianus) with virus of epizootic hemorrhagic deer disease (EHD) did not produce overt clinical disease. Two white-tailed deer (Odocoileus virginianus) exposed identically died in 5 to 6 days. There were no significant lesions in 1 black-tailed deer euthanatized on postinoculation day 5. The EHd virus was not isolated from the spleen of that deer. Seroconversion occurred in black-tailed deer, from zero EHD virus antibody titer before inoculation to titers of 1:128 to 1:256 after inoculation.     

Sheep pox: experimental studies with a west african isolate

Under conditions of a maximum security laboratory, four cross-bred sheep were inoculated intradermally only or intradermally and intratracheally with a West African isolate of sheep pox virus. All sheep had increased temperature and depression by the fourth or fifth day after infection. Nasal and lacrimal discharge and coughing occurred in all sheep but were more severe in sheep receiving the virus via the tracheal route. From the fifth day after infection, numerous papular erythematous skin lesions developed at the inoculation sites. These were 3-7 mm in diameter and gradually became nodular. Some of these lesions healed and others coalesced to form tumorlike masses. In one sheep, euthanized 14 days after intradermal and intratracheal inoculation, nodular lesions were found in the skin around the eyes, nostrils, oral and perianal regions, the mucosa of the rumen and throughout the lungs. Histologically, skin nodules were characterized by ischemic necrosis, vasculitis, microvesicualtion, eosinophilic cytoplasmic inclusions in the dermal epithelial cells and vacuolar nuclear degeneration. The pulmonary lesion was that of proliferative alveolitis with occasional cytoplasmic inclusions in the alveolar cells and macrophages. Ultrastructurally, large cuboidal virus particles were found both in the skin lesion and inoculated tissue cultures. The sheep pox virus structure was easily distinguished from contagious ecthyma virus, a parapoxvirus which causes sporadic disease in Canada. Serum neutralizing antibodies developed in all the sheep by 14 days postinfection.

The clinical and pathological characteristics of experimental sheep pox produced with this West African isolate were similar to those caused by Neethling virus of lumpy skin disease in cattle.

     

Incursion of epizootic hemorrhagic disease into the Okanagan Valley, British Columbia in 1999

In September 1999, unusually high mortality rates in white-tailed deer and California bighorn sheep occurred in the southern Okanagan Valley. Necropsy and histopathologic findings were compatible with epizootic hemorrhagic disease (EHD); the presence of virus was not demonstrated. Subsequent serologic and polymerase chain reaction assays on sentinel cattle suggested an EHD virus incursion.     

A practitioner's primer on foot-and-mouth disease

Foot-and-mouth disease (FMD) is caused by an RNA virus of the genus Aphthovirus; 7 immunologically distinct serotypes of the virus have been identified. Susceptible species are mainly domestic and wild even-toed ungulates, such as cattle, sheep, goats, pigs, bison, and deer. All body fluids of infected animals can contain the virus and are considered infective. The primary mode of transmission is animal-to-animal transmission through inhalation or ingestion of aerosols containing the virus. The virus can also be spread mechanically by contaminated organic debris and fomites and can survive for 48 hours on human oral and nasal mucosa and be spread to uninfected animals in this manner. There is a rapid progression of clinical signs after an animal becomes infected, and the virus spreads rapidly throughout a herd. Clinical signs include excessive salivation; fever; vesicles and erosions of the oral and nasal mucosa, coronary band, interdigital area, and teats; lameness; sloughing of claws; reluctance to move; anorexia; mastitis; decreased milk production; and abortion or weak newborns. In mature animals, FMD has high morbidity and low mortality rates. Infected animals can become inapparent carriers of the virus.     

A Comparison of Bluetongue Virus and EHD Virus: Electronmicroscopy and Serology

Bluetongue virus, BT₈, and the virus of epizootic hemorrhagic disease (EHD) of deer, NJ-55, were plaque purified and compared electronmicroscopically and serologically. The latter included a plaque reduction neutralization test, the agar gel precipitin test, and the complement fixation test. The viruses were indistinguishable morphologically, but antigenically different. A plaquing technique was described for EHD virus.     

MALIGNANT CATARRHAL FEVER IN FARMED RUSA DEER (CERVUS TIMORENSIS): 2. Animal Transmission and Virological Studies

SUMMARY A disease with clinical signs and histological lesions similar to malignant catarrhal fever in cattle was transmitted from Rusa deer (Cervus timorensis) to rabbits. This was accomplished on 3 separate occasions, and the disease was serially passaged in rabbits up to 11 times. The clinical signs in affected rabbits were pyrexia, depression, anorexia, mucopurulent conjuctivitis, nasal discharge and diarrhoea. These signs were seen in 27 of 38 inoculated rabbits with the mean incubation period being 12 days (range 8 to 20 days). Histologically, affected rabbits exhibited mononuclear perivascular cuffing and vasculitis in the brain, heart, liver and kidney. Lymph nodes and spleen showed destruction and loss of mature lymphocytes and lymphoid follicles and an increased number of large lymphoblastoid cells. These clinical signs and lesions were not detected in control rabbits. The disease was not transmitted to cattle, sheep, guinea pigs or mice, nor was an agent isolated in cattle, deer or rabbit tissue cultures, or in chicken embryos.     

Performance of clinical signs to detect bluetongue virus serotype 8 outbreaks in cattle and sheep during the 2006-epidemic in The Netherlands

The performance of clinical signs as a diagnostic test for the detection of BTV-8 outbreaks during the 2006-epidemic in The Netherlands was evaluated by constructing and analysing receiver operating characteristic (ROC) curves. The area under the ROC curve of the BT-associated clinical signs in cattle was 0.77. An optimal efficient test (maximising both sensitivity and specificity) in cattle herds combined a sensitivity (Se) of 67% with a specificity (Sp) of 72%, comprising the following clinical signs: ulcerations and/or erosions of oral mucosa or erosions of lips/crusts in or around nostrils or oedema of the nose or hyperaemic/purple coloration of tongue, tongue protrusion or coronitis or apathy/tiredness or muscle necrosis, stiffness of limbs or loathing or refusal to move, prostration or torticollis or anoestrus. The area under the ROC curve of the BT-associated clinical signs in sheep was 0.81. The optimal efficient test in sheep flocks combined a Se of 76% with a Sp of 72%, comprising the following clinical signs: ulcerations of oral mucosa or serous nasal discharge or erosions/ulceration of tongue mucosa or hypersensitivity of the skin or muscle necrosis, stiffness of limbs or coronitis or grinding of teeth or salivation or weakness/paresis.     

Malignant catarrhal fever-like disease in sheep after intranasal inoculation with ovine herpesvirus-2.

A malignant catarrhal fever (MCF)-like disease was induced experimentally in 3 sheep after aerosol inoculation with ovine herpesvirus-2 (OvHV-2). Each of 3 OvHV-2-negative sheep was nebulized with 2 ml of nasal secretions containing approximately 3.07 X 10(9) OvHV-2 DNA copies from a sheep experiencing an intensive viral-shedding episode. Ovine herpesvirus-2 DNA became detectable by polymerase chain reaction in the peripheral blood leukocytes of all 3 sheep within 3 days, and all 3 seroconverted between 6 and 8 days postinfection (PI). The sheep developed clinical signs, with copious mucopurulent nasal discharge and fever around 14 days PI. One of the 3 clinically affected sheep was euthanized at 18 days PI. Major lesions at necropsy were multifocal linear erosions and ulcers in mucosa of the cheeks, tongue, pharynx, and proximal esophagus and mild disseminated pneumonia. Microscopically, there was extensive moderate superficial histiocytic-lymphocytic rhinitis with epithelial dissociation and degeneration. Moderate multifocal histiocytic bronchointerstitial pneumonia was associated with loss of terminal bronchiolar epithelium. Lymphocytic vasculitis was present only in the lung. The remaining 2 sheep recovered clinically, approximately 25 days PI. The study revealed that clinical signs and lesions resembling MCF can develop when uninfected sheep are exposed to a high dose of aerosolized OvHV-2.     

The development of oral lesions in lambs naturally infected with orf virus

Stomatitis in sheep caused by orf virus can be confused with lesions of more economically significant diseases, including foot-and-mouth disease, but there is no published account of the sequential development of oral orf lesions in the sheep. This report describes the clinical appearance of such lesions during a natural outbreak of the disease in young lambs. Lesions were seen on the gingiva, the tongue and the dental pad/hard palate, and progressed from small erythematous papules to larger, often coalescing papules that in some cases were ulcerated. Resolution started within seven days and was complete within 22 days. The lambs continued to suck and thrive throughout the infection. Lesions at all stages were proliferative, providing a major differentiating factor between orf and other causes of stomatitis in sheep.     

Sheep pox disease outbreaks in Madras Red and Mechery breeds of indigenous sheep in Tamilnadu,India

Sheep pox disease outbreaks were recorded among Madras Red (n = 145) and Mechery (n = 80) breeds of indigenous sheep on three farms in Tamilnadu. Over both breeds, adult mortality rate ranged from 2.66% to 37.5% and lamb mortality ranged from 10% to 17.33%. However, mortality was more in Mechery sheep (50% overall; 37.5% adults, 12.5% lambs) than in Madras Red sheep (24.28% overall; 10.34% adults, 13.79% lambs). The clinical signs observed were high fever, anorexia, respiratory distress, mucopurulent nasal discharge and in a few cases diarrhoea. Cutaneous lesions were mainly observed around nostrils, eyes, lips, ears and in the abdomen. Most of the lesions were covered with purulent materials and on cleaning with sterile swabs, fresh wounds were observed. Dry scabs were also observed over the oral commissure and maxillary areas, which on removal exposed fresh wounds. Important observations on necropsy were severe nodular lesions in the lungs and intestine. The disease was diagnosed as sheep pox by agar gel immunodiffusion test, isolation of virus and its neutralization in BHK₂₁ cells by specific antiserum and by electron microscopy.     

Detection of enzootic nasal tumor virus (ENTV) in a sheep flock in southern Brazil

Enzootic nasal tumor (ENT) is a contagious neoplasm associated with enzootic nasal tumor virus (ENTV), which may induce disease in sheep (ENTV-1) and goats (ENTV-2). This study aimed to describe the occurrence of ENT in two Texel sheep (Ovis aries) from a 75-sheep flock, located in the city of Gravataí, southern Brazil. Animals used to be purchased from different origins, and no specific tests for disease monitoring or quarantine procedure were performed. Affected animals presented respiratory distress, anorexia with severe weight loss, and mucopurulent unilateral nasal discharge. Necropsy was performed in both animals and nasal cavity masses were observed. Histopathological analysis demonstrated an epithelial neoplasm compatible with nasal adenocarcinoma. PCR using a protocol that amplifies a 591 bp sequence of 5’LTR-gag region of ENTV1 was performed followed by DNA sequencing. Both samples were positive, and the sequences obtained presented highest identity (97%) with ENTV strain TN28 (GenBank accession number MH899613) detected in a Texel sheep from Scotland. This is the first report of ENTV-1 leading to enzootic nasal tumor in sheep in Latin America, which confirms the presence of the retrovirus in sheep flocks in the Brazilian territory.

     

Experimental Bluetongue Disease in White-Tailed Deer

Nine white-tailed deer and six sheep were experimentally exposed to the California BTV-8 strain of bluetongue virus. The infections were fatal for seven of the nine deer. An additional deer died from exposure to an isolate of bluetongue virus from bighorn sheep. Clinical signs and lesions of bluetongue in deer were described. The incubation period, signs and lesions of bluetongue and epizootic hemorrhagic disease of deer appear to be similar. Virus isolations were made from the blood and a variety of tissues of exposed deer and identified as bluetongue virus. Neutralizing antibodies were detected in all of the convalescent sera.     

SEROLOGICAL METHODS IN THE DIAGNOSIS OF BLUETONGUE

The viral antibodies in the serum of cattle, sheep and deer are not detectable in the ordinary direct CF test. We have shown that the so-called "non complement-fixing" viral antibodies in the serum of these animal species can be demonstrated by the MDCF test. The MDCF test, as well as the micro AGP test, are group reactive, with all BT isolates studied. However, it is possible with these tests to differentiate antigenically BT virus from EHD virus. The FAT was also useful in differentiating BT virus grown in TC cells from the EHD virus. In the PRN test, all the BT virus isolates studied cross reacted and although quantitative differences were frequently observed, no obvious antigenic classification was possible with the antiserums used in this work. Reactions between the BT viral isolates and the EHD virus were all within the limits of what is presently considered to be non-specific inhibition.     

Antibodies against certain bluetongue and epizootic haemorrhagic disease viral serotypes in Indonesian ruminants.

The orbiviruses contain several important viruses of livestock including bluetongue (BT) and epizootic haemorrhagic disease of deer (EHD) which share some group antigens. Preliminary screening of sera for antibodies to orbiviruses by the agar gel immunodiffusion (AGID) test has previously revealed widespread infections with the BT group in Indonesia. However serum neutralization (SN) tests give a more accurate estimate of exposure to each serotype in the BT and EHD groups, and in this study were applied to sera that had reacted previously in the AGID test. Five different serotypes of BT and one serotype of EHD virus were studied. Reactors to BT serotype 20 were the most prevalent, followed by EHD type 5 and BT types 21, 12, 1 and 17. Antibodies against BT serotype 20 were present in cattle, buffaloes, goats and sheep, but were most common in buffaloes. Buffaloes showed the highest exposure to the BT serotypes tested. Antibody to EHD type 5 occurred most frequently in cattle. Antibodies against all BT and EHD serotypes tested were found in buffaloes and cattle while goats had antibodies against BT types 20, 21 and EHD type 5 and sheep had antibodies only against BT type 20.     

Sheep pox disease outbreaks in Madras Red and Mechery breeds of indigenous sheep in Tamilnadu, India

Sheep pox disease outbreaks were recorded among Madras Red (n=145) and Mechery (n=80) breeds of indigenous sheep on three farms in Tamilnadu. Over both breeds, adult mortality rate ranged from 2.66% to 37.5% and lamb mortality ranged from 10% to 17.33%. However, mortality was more in Mechery sheep (50% overall; 37.5% adults, 12.5% lambs) than in Madras Red sheep (24.28% overall; 10.34% adults, 13.79% lambs). The clinical signs observed were high fever, anorexia, respiratory distress, mucopurulent nasal discharge and in a few cases diarrhoea. Cutaneous lesions were mainly observed around nostrils, eyes, lips, ears and in the abdomen. Most of the lesions were covered with purulent materials and on cleaning with sterile swabs, fresh wounds were observed. Dry scabs were also observed over the oral commissure and maxillary areas, which on removal exposed fresh wounds. Important observations on necropsy were severe nodular lesions in the lungs and intestine. The disease was diagnosed as sheep pox by agar gel immunodiffusion test, isolation of virus and its neutralization in BHK(21) cells by specific antiserum and by electron microscopy.     

Horizontal transmission of Aujeszky's disease virus from sheep to pigs

Eight 2-month-old merino lambs were inoculated intranasally with different (10(2.0)-10(5.0)TCID50) amounts of Aujeszky's disease virus (ADV). Electron microscopic studies indicated that ADV replicated in extra-neural sites, in the epithelial cells of the mucosa of the upper and lower respiratory tract. Although the virus was excreted continuously in nasal discharges, horizontal transmission to contact lambs failed. The surviving exposed and contact lambs had no demonstrable antibodies against ADV and they were susceptible when challenged by ADV. However, the virus was transmitted to susceptible pigs in contact with the exposed lambs. One of the five contact pigs showed characteristic clinical signs of Aujeszky's disease, developed a nonsuppurative meningoencephalomyelitis and ADV was recovered from the brain, nasal discharge and other organs. Restriction enzyme analysis of DNA from this virus confirmed the sheep origin of the isolate. The other 4 pigs seroconverted. ADV infection in sheep is therefore a possible source of infection for pigs, but the lack of horizontal transmission in sheep was confirmed.     

Control of clinical paratuberculosis in New Zealand pastoral livestock

This review summarises current control measures for clinical paratuberculosis (Johne’s disease; JD) in New Zealand pastoral livestock. Most New Zealand sheep, deer, beef and dairy cattle herds and flocks are infected by Mycobacterium avium ssp. paratuberculosis (Map). Dairy cattle and deer are mostly infected with bovine (Type II), and sheep and beef cattle with ovine (Type I) strains. Control in all industries is voluntary. While control in sheep and beef cattle is ad hoc, the dairy and deer industries have developed resources to assist development of farm-specific programmes.

The primary target for all livestock is reduction of the incidence rate of clinical disease rather than bacterial eradication per se. For dairy farms, a nationally instituted JD-specific programme provides guidelines for risk management, monitoring and testing clinically suspect animals. While there is no formal programme for sheep farms, for those with annual prevalences of clinical disease >2%, especially fine wool breeds, vaccination may be a cost effective control option. The deer industry proactively monitors infection by a national abattoir surveillance programme and farmers with an apparent high disease incidence are encouraged to engage with a national network of trained consultants for management and control advice. Evaluation of the biological and economic effectiveness of control in all industries remains to be undertaken. Nevertheless, opportunities exist for farmers, who perceive significant JD problems in their herds/flocks, to participate in systematic best-practice activities that are likely to reduce the number of clinical infections with Map on their farms, and therefore the overall prevalence of JD in New Zealand’s farming industries.