Bovine respiratory disease (BRD) is the most common and economically devastating infectious disease affecting beef cattle in the world. [1] It is a complex, bacterial or viral infection that causes pneumonia in calves which can be fatal. It also affects many other species of feedlot animals like sheep and pigs, but is most prominent in calves. [2] The infection is usually a sum of three codependent factors: stress, an underlying viral infection, and a new bacterial infection. [3] The diagnosis of the disease is complex since there are multiple possible causes and cattle are reluctant to display any indications of pain. [4]
The disease manifests itself most often in calves within four weeks of weaning, when calves are sorted into groups of roughly 10-15 in number, and sold to different feedlots via train, tractor trailer, and truck. [5] Because of this, BRD is most commonly referred to as "shipping fever". [2] It is not known whether the stress itself, co-mingling, or travel conditions are at most to blame, and while studies have identified general stressing factors like transport and cold weather conditions, there is still no conclusive evidence on more specific factors (e.g. distance, transport mode, temperature, or temperature volatility). [6]
BRD is a "multi-factorial syndrome" that is dependent on a number of different causes. [5] The pathologic condition commonly arises where the causative organism becomes established by secondary infection, following a primary bacterial or viral infection. [5]
There are many stressors that can help induce BRD, the main one being transportation. During transit, cattle are exposed to many factors such as dehydration and. exhaustion that can lead to anxiety. Poor ventilation and overcrowding also allow bacteria to spread more easily between the calves.
Source: [5]
Fall is the most prominent season for beef cattle, so it is during that time of year when the majority of cattle are grouped together in larger amounts. This increases the risk for BRD along with fluctuations in weather. Studies show that they years with the highest risks for BRD were associated with severe weather environments, rather than average conditions. [5]
BRD often develops within 4 weeks of cattle transport. [7] Symptoms include: [8] [9] [10]
Because of the number of possible viral/bacterial precursors to BRD, there are a number of treatment options circling around the three main aggravators of the disease: Viruses, Bacteria, and Stress.
Vaccinations exist for several biological BRD precursors, but the multitude of possible precursors complicates the process of choosing a vaccine regime. [9] Additionally, vaccines are not completely effective in stopping the disease, but are merely helpful in mitigation. [11] Many of the problems with vaccine effectiveness rest with improper use, such as failing to time vaccine doses appropriately, or not administering them before shipping. [12] Vaccines are available for a number of viral/bacterial agents and are often sold in combination with each other.
Calves are often bought unvaccinated, so antibiotics can help combat the bacterial factors of the disease. These are given orally, or in the forms of injections, pastes, or electrolytes. [13] The Virginia Cooperative Extension recommends the following antibiotics: [10]
Aside from the strict use of drugs, there are other natural ways to help calves recuperate. Ensuring that they are fed good quality feedstuffs consisting of materials like grass to coax them into consuming the most amount of nutrients possible. [10] Additionally, they should refrain from staying in an area of poor ventilation with fluctuating temperatures to ensure that the infection does not grow worse.
However, multi-drug resistance has become more prevalent, requiring further studies to target the gene responsible for the resistance. [14]
Stress often serves as the final precursor to BRD. The diseases that make up BRD can persist in a cattle herd for a long period of time before becoming symptomatic, but immune systems weakened by stress can stop controlling the disease. Major sources of stress come from the shipping process [15] and from the co-mingling of cattle. [9]
Pestivirus is a genus of viruses, in the family Flaviviridae. Viruses in the genus Pestivirus infect mammals, including members of the family Bovidae and the family Suidae. There are 11 species in this genus. Diseases associated with this genus include: hemorrhagic syndromes, abortion, and fatal mucosal disease.
Bovine alphaherpesvirus 1 (BoHV-1) is a virus of the family Herpesviridae and the subfamily Alphaherpesvirinae, known to cause several diseases worldwide in cattle, including rhinotracheitis, vaginitis, balanoposthitis, abortion, conjunctivitis, and enteritis. BoHV-1 is also a contributing factor in shipping fever, also known as bovine respiratory disease (BRD). It is spread horizontally through sexual contact, artificial insemination, and aerosol transmission and it may also be transmitted vertically across the placenta. BoHV-1 can cause both clinical and subclinical infections, depending on the virulence of the strain. Although these symptoms are mainly non-life-threatening it is an economically important disease as infection may cause a drop in production and affect trade restrictions. Like other herpesviruses, BoHV-1 causes a lifelong latent infection and sporadic shedding of the virus. The sciatic nerve and trigeminal nerve are the sites of latency. A reactivated latent carrier is normally the source of infection in a herd. The clinical signs displayed are dependent on the virulence of the strain. There is a vaccine available which reduces the severity and incidence of disease. Some countries in Europe have successfully eradicated the disease by applying a strict culling policy.
Aujeszky's disease, usually called pseudorabies in the United States, is a viral disease in swine that is endemic in most parts of the world. It is caused by Suid herpesvirus 1 (SuHV-1). Aujeszky's disease is considered to be the most economically important viral disease of swine in areas where classical swine fever has been eradicated. Other mammals, such as cattle, sheep, goats, cats, dogs, and raccoons, are also susceptible. The disease is usually fatal in these animal species.
Feline viral rhinotracheitis (FVR) is an upper respiratory or pulmonary infection of cats caused by Felid alphaherpesvirus 1 (FeHV-1), of the family Herpesviridae. It is also commonly referred to as feline influenza, feline coryza, and feline pneumonia but, as these terms describe other very distinct collections of respiratory symptoms, they are misnomers for the condition. Viral respiratory diseases in cats can be serious, especially in catteries and kennels. Causing one-half of the respiratory diseases in cats, FVR is the most important of these diseases and is found worldwide. The other important cause of feline respiratory disease is feline calicivirus.
Bovine malignant catarrhal fever (BMCF) is a fatal lymphoproliferative disease caused by a group of ruminant gamma herpes viruses including Alcelaphine gammaherpesvirus 1 (AlHV-1) and Ovine gammaherpesvirus 2 (OvHV-2) These viruses cause unapparent infection in their reservoir hosts, but are usually fatal in cattle and other ungulates such as deer, antelope, and buffalo. In Southern Africa the disease is known as snotsiekte, from the Afrikaans.
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Lumpy skin disease (LSD) is an infectious disease in cattle caused by a virus of the family Poxviridae, also known as Neethling virus. The disease is characterized by fever, enlarged superficial lymph nodes, and multiple nodules on the skin and mucous membranes, including those of the respiratory and gastrointestinal tracts. Infected cattle may also develop edematous swelling in their limbs and exhibit lameness. The virus has important economic implications since affected animals tend to have permanent damage to their skin, lowering the commercial value of their hide. Additionally, the disease often results in chronic debility, reduced milk production, poor growth, infertility, abortion, and sometimes death.
Bovine viral diarrhea (BVD), bovine viral diarrhoea or mucosal disease, previously referred to as bovine virus diarrhea (BVD), is an economically significant disease of cattle that is found in the majority of countries throughout the world. Worldwide reviews of the economically assessed production losses and intervention programs incurred by BVD infection have been published. The causative agent, bovine viral diarrhea virus (BVDV), is a member of the genus Pestivirus of the family Flaviviridae.
Bovine leukemia virus (BLV) is a retrovirus which causes enzootic bovine leukosis in cattle. It is closely related to the human T‑lymphotropic virus type 1 (HTLV-I). BLV may integrate into the genomic DNA of B‑lymphocytes as a DNA intermediate, or exist as unintegrated circular or linear forms. Besides structural and enzymatic genes required for virion production, BLV expresses the Tax protein and microRNAs involved in cell proliferation and oncogenesis. In cattle, most infected animals are asymptomatic; leukemia is rare, but lymphoproliferation is more frequent (30%).
Pradofloxacin, sold under the brand name Veraflox among others, is a third-generation enhanced spectrum veterinary antibiotic of the fluoroquinolone class. It was developed by Elanco Animal Health GmbH and received approval from the European Commission in April 2011, for prescription-only use in veterinary medicine for the treatment of bacterial infections in dogs and cats.
Influenza, commonly known as the flu, is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms begin one to four days after exposure to the virus and last for about two to eight days. Diarrhea and vomiting can occur, particularly in children. Influenza may progress to pneumonia from the virus or a subsequent bacterial infection. Other complications include acute respiratory distress syndrome, meningitis, encephalitis, and worsening of pre-existing health problems such as asthma and cardiovascular disease.
Bovine immunodeficiency virus (BIV) is a retrovirus belonging to the genus Lentivirus. It is similar to the human immunodeficiency virus (HIV) and infects cattle. The cells primarily infected are lymphocytes and monocytes/macrophages.
Bovine coronavirus is a coronavirus which is a member of the species Betacoronavirus 1. The infecting virus is an enveloped, positive-sense, single-stranded RNA virus which enters its host cell by binding to the N-acetyl-9-O-acetylneuraminic acid receptor. Infection causes calf enteritis and contributes to the enzootic pneumonia complex in calves. It can also cause winter dysentery in adult cattle. It can infect both domestic and wild ruminants and has a worldwide distribution. Transmission is horizontal, via oro-fecal or respiratory routes. Like other coronaviruses from genus Betacoronavirus, subgenus Embecovirus, it has a surface protein called hemagglutinin esterase (HE) in addition to the four structural proteins shared by all coronaviruses.
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