Common, Emerging, Vector-Borne and Infrequent Abortogenic Virus Infections of Cattle

Abstract

This review deals with the aetiology and the diagnosis of bovine viral abortion. While the abortion rates on beef and dairy cattle farms usually do not exceed 10%, significant economic losses because of abortion storms may be encountered. Determining the cause of abortions is usually a challenge, and it generally remains obscure in more than 50% of the necropsy submitted foetuses. Bovine viral diarrhoea virus and bovine herpesvirus-1 are the most common viruses causally associated with bovine abortions in farmed cattle globally. Rift Valley fever virus and bluetongue virus are important insect-transmitted abortogenic viruses. The geographic distribution of these two viruses is primarily dependent on the distribution of the insect vector, but direct transmission is possible. Recent global warming and subsequent insect vector expansion, coupled with the increase in international trade of animals and animal products, have been important factors in recent geographic advances of those two viruses. Bovine herpesviruses-4 and 5 in cattle, as well as other less frequent vector-borne viruses including epizootic haemorrhagic disease virus, Aino virus, Wesselsbron virus and lumpy skin disease virus, are discussed.

Epidemiology and Emergence of Schmallenberg Virus Part 1: Origin, Transmission and Differential Diagnosis

“…Although clinical presentations depend on several factors, such as on strain of virus, species of host, immune status of host, reproductive status of host, age of host, concomitant infections and time of gestation [49], BVD virus is known to produce from subclinical infections (persistently infected animals) to a large number of diverse diseases, including reproductive disorders (decrease in conception rate and pregnancy rate, increased embryonic mortality), early embryonic death, foetal reabsorption abortion, stillbirths, central nervous system defects (microencephaly, cerebellar hypoplasia, hydranencephaly, hydrocephalus, hypomyelinogenesis, hypomyelination, cerebellar-ocular agenesis, ocular abnormalities), ocular abnormalities (microphthalmia, cataracts, retinal degeneration, optic neuritis), musculoskeletal deformities (brachygnatism), thymic aplasia, hypotrichosis, alopecia, pulmonary and renal hypoplasia [29,50], growth retardation [29], enteritis and mucosal disease [51][52][53]. The most dramatic clinical symptoms are associated with the peracute form of the disease that is characterized by a sudden decrease in milk production, fever, watery and bloody diarrhoea, dehydration, tenesmus, tachypnea, tachycardia, drooping ears, anorexia, excessive lacrimation, nasal discharge, hypersalivation, petechial and ecchymotic haemorrhages of the visible mucosa, and development of ulcers of the nares, muzzle, lips and oral cavity [54] mucous membranes as well as skin lesions around the inguinal and perineal regions, the inner thighs and inside the ears [55].…”

“…Only the non-cytopathic, which is ubiquitous in nature, has the ability to establish persistent infection, once this type crosses the placenta invades the foetus and establishes persistent infection due to the non-recognition of the virus, at the age of infection, by the immature immune system. This condition is determinant for the spread of the virus [50,51]. Cytopathic bovine viral diarrhoea virus (BVDV) is rare and seldom isolated unless accompanied by non-cytopathic BVDV.…”

“…This virus affects sheep, goats and sporadically cattle [50,111]. Infection in adult animals and calves is usually subclinical or inapparent [112][113][114], although in sheep with preexisting liver disease clinical findings can be more expressive and severe.…”

“…BHV-1 shares antigenic and genetic close relationships with other ruminant alphaherpesviruses [64]: BoHV-5, caprine herpesvirus-1, cervid herpesvirus-1 (red deer), cervid herpesvirus-2 (reindeer), bubaline herpesvirus-1 and elk herpesvirus-1 [65]. The virus has been associated with a wide range of clinical symptoms, including rhinotracheitis, abortion, infertility and occasionally encephalitis in calves [50,66]. However, the clinical symptoms may be mild and localized or include severe generalized disease, leading eventually to death [67].…”

“…BoHV-1 is a member of the genus Varicellovirus, which belongs to the Herpesviridae family, subfamily Alphaherpesvirinae [50,64]. BHV-1 shares antigenic and genetic close relationships with other ruminant alphaherpesviruses [64]: BoHV-5, caprine herpesvirus-1, cervid herpesvirus-1 (red deer), cervid herpesvirus-2 (reindeer), bubaline herpesvirus-1 and elk herpesvirus-1 [65].…”