Virological and molecular biological investigations into equine herpes virus type 2 (EHV-2) experimental infections.

Two 18-month-old naturally reared ponies were used to investigate the pathogenicity of EHV-2. After dexamethasone treatment, pony 1 was inoculated intranasally with EHV-2 strain T16, which has been isolated from a foal with keratoconjunctivitis superficialis and pony 2 was similarly inoculated with strain LK4 which was originally isolated from a horse with upper respiratory tract disease. Following virus inoculation, pyrexia was not detected in either pony but both developed conjunctivitis, lymphadenopathy, and coughing. EHV-2 was detected in nasal mucus samples up to day 12 post infection (p.i.), in eye swabs up to day 10 p.i., and in buffy coat cells throughout the investigation in both animals. EHV-2-specific antibody titres were raised significantly 18 days p.i. Following the administration of dexamethasone, 3 months p.i., infectious virus was again detected in nasal mucus and conjunctival swabs from both ponies for 7 days. The tissue distribution of EHV-2 genome was studied post mortem, by means of a nested PCR. EHV-2 was detected in lymphoid tissues, lung, conjunctiva, trigeminal ganglia and olfactory lobes of pony 2, whereas in pony 1 only the conjunctiva of the left eye was PCR positive.

[Recent information about the etiopathogenesis of paretic-paralytic forms of herpesvirus infection in horses]. / Neuere Erkenntnisse zur Atiopathogenese der paretisch-paralytischen Verlaufsform der Herpesvirusinfektion des Pferdes.

From spring 1990 to summer 1991 we investigated 21 horses with clinical symptoms of EHV-infection by means of serological and virological methods including DNA-hybridization to identify the causative agents. The results indicated that, as already reported by us, EHV4 may also cause the paralytic form of the infection. The possibility of double infection with EHV4 and EHV1 cannot be excluded. In 3 out of 21 affected horses we could investigate brain tissue and/or spinal fluid by Dotblot hybridization with EHV1 and EHV4-DNA. The investigated samples of all three horses showed hybridization with EHV4-DNA, without or with less pronounced reaction with EHV1-DNA. The results were confirmed by serological investigation. Brain tissue and cerebrospinal fluid from two horses with paretic or paralytic disorders (1979 and 1980) was also investigated by DNA hybridization. In the liquor of one horse--a 5-month-old foal with neonatal ataxia--we detected EHV1-DNA. The other horse showed a strong reaction with EHV1 and a weaker reaction with EHV4 in its brain material and no hybridisation in the cerebrospinal fluid. The results are discussed.

[Foal diseases and foal loss]. / Untersuchungen von Fohlenerkrankungen und Fohlenverlusten.

An investigation was carried out upon occurrence and course of infectious and non infectious diseases as well as the mortality in foals born and raised at the State Stud Marbach/Lauter between 1982 and 1991. The foals have been investigated from birth to weaning, they consisted of 177 Thoroughbred Arabians and 285 German Warmblood foals (total 462 foals). The diseases were divided into pre-, peri- and postnatal according to their known or assumed cause and onset. There was a preponderance of prenatal diseases (11.25%) whereas the perinatal rate was 1.30% and the postnatal rate of diseases was 8.66%. The rate of infectious diseases increased from the pre- to the postnatal period of life. A comparison between the two breeds showed that 9% of the Arabian foals suffered from infectious diseases whereas only 4.9% of the Warmblood foals were similarly affected. This is probably linked to the lower level of colostral immunoglobulins in the Arab herd, as previously shown by us. The measurement of mare colostral and foal serum IgG as well as the paramunisation of neonatal and weaned foals are important factors in the prevention of infectious diseases.

[Effect of a paramunity inducer on the incidence of diseases and the plasma cortisol content in Thoroughbred foals before and after weaning]. / Einfluss eines Paramunitätsinducers auf die Inzidenz von Erkrankungen und die Plasmakortisolgehalte bei Vollblutfohlen vor und nach dem Absetzen.

The effect of the prophylactic application of the paramunity inducer Baypamun on the incidence of diseases among foals (n = 63) in four Thoroughbred studs was evaluated. In a blind study, 38 of the foals received 2 ml of Baypamun intramuscularly while 25 of the foals received a placebo at six and four days before weaning and on the fifth day post-weaning. During the observation period of three weeks, beginning with the first and ending ten days after the last application, 7.9% of the foals treated with Baypamun (3 out of 38) suffered from respiratory infections compared to 24% of the foals treated with placebo (6 out of 25). The blood plasma cortisol concentrations were also measured in 53 of the foals of three studs before and 24 hours after weaning. The cortisol concentration increased in all the foals. However, the increase was significant only for the Baypamun treated foals of one stud while it was significant for the placebo treated foals of all studs (p < 0.01).

The genome of equine herpesvirus type 2 harbors an interleukin 10 (IL10)-like gene.

A gene was identified within the DNA sequences of the EcoRI DNA fragment N (4.3 kbp) of the genome of equine herpesvirus type 2 (EHV-2) coding for a protein (179 amino acid residues) homologous to the cytokine synthesis inhibitory factor (CSIF; interleukin 10) of the human and mouse, and to the Epstein-Barr virus (EBV) protein BCRF1. This finding is further significant evidence that the interleukin 10 (IL-10) and/or IL-10-like gene can indeed be present in the genomes of members of the herpesviral family.

[The effectiveness of the paramunity inducer Baypamun (PIND-ORF) for the prevention and metaphylaxis of an experimental infection with the infectious bovine rhinotracheitis virus in cattle]. / Wirksamkeit des Paramunitätsinducers Baypamun (PIND-ORF) zur Prophylaxe und Metaphylaxe einer experimentellen Infektion mit Virus der Infektiösen Bovinen Rhinotracheitis beim Rind.

Efficacy of the paramunity inducer Baypamun (PIND-ORF) was evaluated by an IBR challenge trial in cattle, as one model for infectious diseases in bovine. Prophylactic treatment with Baypamun protected cattle against manifestation of clinical symptoms after experimental IBR infection. The degree of protection depended on the time between paramunization and challenge infection. Even in metaphylactically paramunized cattle Baypamun reduced the IBR symptoms. In correlation to the reduction of clinical symptoms paramunization also reduced virus excretion by more than 99% in treated cattle compared to non paramunized animals. The induction of interferon following IBR infection was investigated in paramunized cattle. Application of Baypamun enabled treated animals to react faster with interferon synthesis following IBR infection than control animals did. The demonstration of the status of paramunity following Baypamun application in cattle provides a concept in the prevention of infectious disease in the practice.

[Infection with equine herpesvirus and its manifestation in the central nervous system of the horse]. / Infektion mit equinen Herpesviren und Manifestation am Zentralnervensystem beim Pferd.

Infections with EHV1 can lead to manifestation at the CNS of horses followed by encephalomyelitis and "equine stroke". Horse experiments could confirm the clinical picture and gave links to the potential pathogenesis of the disease. We also have been in the position to isolate and characterize an EHV4 virus out of the brain of a horse with CNS disorders. The two viruses carry different biological properties which obviously dominate the pathogenesis. These properties as well as experimental and field cases are described and different diagnostic tests are discussed.

Rapid method for the identification and screening of herpesviruses by DNA fingerprinting combined with blot hybridization.

Rapid characterization of herpesvirus isolates exemplified by equine herpesviruses is described. Total DNAs were isolated from virus infected small scale cell cultures. The DNA fragments obtained after restriction enzyme digestion were separated on agarose gels, transferred and immobilized on filter membranes. A radioactively labelled probe derived from the purified DNA of an EHV-1 reference strain was used for hybridization in order to detect the restriction fragments of different EHV-1 field isolates. This method allows the typing of many isolates within a short period of time.

[Current virus diseases in horses. Diseases in foals and respiratory tract infections]. / Aktuelle Viruskrankheiten des Pferdes. Fohlenkrankheiten und Atemwegsinfektionen.

At the moment, horse praxis is confronted by two disease complexes which are difficult to fight against as well in prophylaxis as in therapy, but which get an increasing importance. First they concern virus infections of the foals and second primary virus-caused respiratory diseases. Foals get infected during the embryonal/fetal development, in the perinatal or postnatal period. Normally the infection is caused by latent infected, clinical healthy mares, or in the postnatal period by ubiquitous, normally opportunistic socalled problem-viruses, i.e. equine herpes-viruses 1 and 2, rota-, corona- and adenoviruses. Primary responsible for the virus infections of the respiratory tract are the rhinopneumonitis- and influenza-A-virus, the reo- and rhinoviruses and the arteritis-virus.

Infection of the central nervous system of horses with equine herpesvirus serotype 1.

During the last 2 years different equine herpesviruses serotype 1 strains have been isolated from cases of paretic or paralytic disease among horses in the Federal Republic of Germany. In this paper the available information is collated and briefly reviewed. A short description of the symptoms and the possible mechanism of the pathogenesis are given.