Infectious bovine rhinotracheitis
The infectious bovine rhinotracheitis ( IBR ) is a virus-related infectious disease of cattle . The name results from the clinical appearance, a rhinitis (inflammation of the nose) and tracheitis ( inflammation of the windpipe). In the English-speaking world, the disease is also called "red nose". The disease is also known as letter disease or IBR-IPV , where IPV stands for Infectious Pustular Vulvovaginitis .
Cause and epidemiology
The IBR pathogen is the globally occurring Bovine Herpesvirus 1 (BHV1).
An introduction of the pathogen into BHV1-free farms usually takes place through the purchase of animals that are clinically healthy, but latently carry the virus . Indirect transmission through people, equipment and instruments is also possible.
In latently infected animals, reactivation and thus excretion of the virus can occur due to special circumstances. Such circumstances are e.g. B. calving, transport, bringing together many animals of different origins in a confined space (so-called crowding ), parasitosis , vaccinations and the administration of glucocorticoids .
Wild ruminants, among others, form a permanent reservoir of viruses.
Pathogenesis
The BHV1 is infected by droplet infection with infectious nasal secretions, tear secretions or saliva. During the incubation period of 2–6 days, the viruses multiply in the mucous membrane cells of the upper respiratory tract and thereby damage them. After 2–3 weeks, the virus is excreted through nasal secretions, lacrimal secretions and saliva. The virus reaches the ganglion of the trigeminal nerve along the nerves (neuroaxonal distribution) . The pathogen can z. B. get into the ovaries , placenta and udder and lead to cycle disorders, abortion / stillbirth or mastitis .
By attacking the mucous membranes with their damage, secondary infections are possible. Pasteurella , mycoplasma , parainfluenza-3 virus and BVDV are of particular importance here.
Surviving a BHV1 infection leads to immunity which protects against the clinical symptoms of IBR, but not against superinfection with BHV1. The animal remains latently infected persistently (withdrawal in nerves) and can become an intermittent shedder.
Symptoms
As a rule, the disease occurs as a disease and is benign. In the calf, however, infestation with secondary pathogens often leads to a severe course of the disease with diphtheroid- necrotizing laryngotracheitis .
IBR manifests itself through sudden loss of appetite , a drop in milk, high fever (42 ° C), nasal discharge and tears as well as profuse salivation. There is reddening and swelling of the conjunctiva as well as the mucous membrane of the mouth and the nasal entrance. There may be a cough and an increased breathing rate. In mildly ill animals, the fever subsides within 1–2 days. Complete healing occurs within 1–2 weeks. Seriously ill animals have persistent fever, foul-smelling mucopurolent nasal discharge (mucous- purulent ), mucosal ulceration and severe dyspnoea and stridor . Such animals can be sick for a long time, become uneconomical and also suddenly perish.
Abortions caused by BHV1 usually occur around the 6th – 8th Month of gestation , sometimes a few weeks to months after clinical IBR.
BHV1 infection of the calves is possible before birth in the womb, but more likely during or shortly after birth. A distinction is made between three forms of disease in calves. The respiratory form manifests itself in slimy-purulent ( mucopurulent ) nasal discharge, tears, coughing, abnormal breathing noises , difficult swallowing, fever and death within a few days. The digestive form is characterized by severe diarrhea with a high fever. A combination of the respiratory and digestive forms is called generalized form . It is particularly serious and can be fatal very quickly.
In unvaccinated dairy herds, a mean morbidity of 10 to 30% and a lethality of <3% are reported. In unvaccinated beef cattle, the morbidity is up to 100% and the mortality up to 10%. BHV1 infection is often fatal in newborns.
diagnosis
The pathogen is detected by nasal swabs or nasal rinsing samples from freshly diseased animals. Pharyngeal lymph nodes can be used as tissue samples, and liver tissue in calves. In aborted or stillborn calves, pathogens can be detected in the cotyledons . The detection takes place by means of ELISA , immunofluorescence or PCR .
Enzootic bronchopneumonia , BVD-MD , foot-and-mouth disease and malignant catarrhal fever come into question in the differential diagnosis . In calves, neonatal diarrhea , calf diphtheroid and septic bacterial infections such as colisepticemia must also be taken into account.
therapy
Parenteral antibiotics are given to prevent and treat secondary infections. High doses and repeated doses of anti-inflammatory drugs (especially glucocorticoids) should be avoided because of the associated risk of reactivating latent BHV1 infections.
prophylaxis
Animals should only be purchased from officially recognized free stocks. Optimized housing conditions prevent stress reactions and thus reactivation in latently infected animals. BHV1-positive reagents must not be given glucocorticoids. Regular vaccination with an officially approved BHV1 vaccine protects against the disease. For this purpose, a glycoprotein E (gE) deleted vaccine is used so that a differentiation between field virus and vaccine virus can be made with commercial ELISA test kits. A general vaccination ban against BHV-1 has been in effect in Saxony-Anhalt since April 1, 2012. In Lower Saxony, as part of the final renovation, a vaccination ban against BHV-1 was issued from November 1, 2014. The last BHV-1 reagents must be removed by May 1, 2015.
Significance / animal health regulations
In addition to respiratory illness, which can cause direct economic losses such as reduced production, treatment costs or even animal losses, fertility disorders are also important. A positive BHV1 status, whether through infection or vaccination, significantly reduces the commercial value of breeding animals.
IBR is a notifiable animal disease . The aim of the control program (based on the BHV1 regulation - see web links) is to create pathogen-free and seronegative cattle herds. Denmark, Austria, Finland, Sweden and the province of Bolzano in Italy currently have this status. In Germany, the federal states of Bavaria and Saxony-Anhalt are already well advanced with the BHV1 renovation.
literature
- Matthaeus Stöber: Infectious Bovine Rhinotracheitis. In: Gerrit Dirksen et al. (Ed.): Internal medicine and surgery of the cattle. 4th edition, Verlag Parey, Berlin 2002, pp. 278–283
