VN May 2021

Vetnuus | Mei 2021 34 Infectious Pustular Vulvovaginitis (IPV) The genital form is mostly caused by a different subtype as the respiratory form, but vesicular lesions remain the main clinical symptom due to the lysis of mucosal cells. IPV develops 1 – 3 days after mating, with the first clinical signs being frequent urination and an elevated tail (as a result of pain, affected cows are reluctant to have contact between the tail and the vulva). Pyrexia, depression, decreased feed intake and anorexia are typical symptoms, along with pustules and ulcers in the superficial genitalia. Most of these lesions heal 10 – 14 days after their onset, but there are some cases that may produce a purulent vaginal discharge for several weeks. Similar to IBR there is always a possibility of secondary bacterial infection, that may progress to metritis. Infectious Pustular Balanoposthitis (IPB) This is basically the male form of IPV, with similar lesions in the mucosa of the penis and prepuce. The recovery period is also 10 - 14 days for visible lesions, but it is important to note that it might take several weeks for full recovery and ability to return to mating. Again, secondary bacterial infection can complicate the healing process and is quite common. If a bull contracts IPB during the mating season, it is important to withdraw the bull from the cow herd. If the bull is allowed to continue mating, not only does it potentially spread the disease, but it might result in scar tissue formation that can have various negative sequalae such as adhesions, annular constriction and penile distortion. Encephalitis The neurologic form of the disease is caused by BHV-5, that used to be classified as subtype BHV-1.3 and is usually seen in calves. The virus is presumed to infect the animal via the respiratory route, from where it travels through the trigeminal ganglion to the central nervous system. General neurological symptoms such as ataxia, tremors, recumbency with paddling and opisthotonos are observed. Prognosis is poor and coma and death can be expected 4 days after the onset of clinical symptoms. Animals that do recover are often blind. Other Generalised neonatal disease has been described where various mucosal organs are affected, resulting in respiratory disease, conjunctivitis and diarrhoea. This form is usually fatal to the neonate and it has been observed that it often coincides with abortion storms in a naïve herd. Summary BHV-1 is a double stranded DNA virus capable of infecting various cells, with proliferative reproduction taking place in epithelial cells of mucosal surfaces. The virus can enter either a lytic pathway , where cell lysis leads to the vesicular lesions commonly observed, or a latent pathway in which the host immune system is evaded which leads to infected animals becoming life-long carriers. Infection with BHV-1 can lead to various diseases, depending on the route of infection (e.g. respiratory or reproductive), although most of these syndromes share certain clinical signs due to similar cellular destruction caused by the virus. Immunosuppression leading to secondary bacterial infection is a frequent complication. Part two of this series will delve deeper into the host immune response to BHV-1, vaccinology and control measures to mediate the disease. The author can be contacted for a full list of references. v Dr. Schabort Froneman (BSc, BVSc) | Technical Manager: Ruminants Zoetis SA (Pty) Ltd PostNet Suite 53, Private Bag 9976, Sandton, South Africa, 2146 Office : (+27) 011 245 3320 Mobile : (+27) 082 348 2306 Email : schabort.froneman@zoetis.com Regulars I Zoetis Livestock Column