Bovine respiratory disease (BRD) is the most common and costly 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. The infection is usually a sum of three codependent factors: stress, an underlying viral infection, and a new bacterial infection. [2] The diagnosis of the disease is complex since there are multiple possible causes. [3]
The disease manifests itself most often in calves within four weeks of weaning, when calves are sorted and often sold to different farms; a common nickname for BRD is "shipping fever." [4] [lower-alpha 1] 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. [7] The pathologic condition commonly arises where the causative organism becomes established by secondary infection, following a primary bacterial or viral infection, which may occur after stress, e.g. from handling or transport. [8] Usually all three of these factors must be present in order to cause BRD. [9] Viral agents are often present in the herd for an extended time, with almost no symptoms, and only cause severe complications with a bacterial infection. [7]
The bacterial agents most commonly linked with BRD are Mannheimia haemolytica , Pasteurella multocida , Histophilus somni , and Mycoplasma bovis . [7] M. haemolytica serovar A1 is known as a particularly common bacterial cause of the disease. [10] Viral agents include Bovine viral diarrhea (BVD), Infectious Bovine Rhinotracheitis (IBR), Bovine respiratory syncytial virus (BRSV), and Parainfluenza type-3 virus (PI-3). [11]
BRD often develops within 4 weeks of cattle transport. [11] The biggest sign of the pneumonia that BRD causes is depression, shown as droopy ears, dull eyes, and social isolation. Additionally, most cows will have a fever above 104 °F (40 °C). [12] Other symptoms include coughing, decreased appetite, and breathing difficulty. [9]
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. [13] 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. [14]
Vaccines are available for a number of viral/bacterial agents, including IBR, PI3, BVD, BRSV, Pasteurella, and Haemophilus somnus. [9] Many of these vaccines can be given simultaneously, because of their similar dosing schedule. For example, IBR, PI3, BVD, and BRSV vaccines are often sold in combination with each other. [15]
In the absence of vaccination (often because calves are bought unvaccinated), antibiotics can help to stop the bacterial factors of the disease. The Virginia Cooperative Extension recommends Micotil, Nuflor, and Baytril 100 as newer antibiotics that do not need daily dosing, but also notes that Naxcel, Excenel, and Adspec are effective as well. [12]
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 [16] and from the co-mingling of cattle. [9]
Weather may be another possible factor. Cases are more common in the fall (although this is the traditional time to sell cattle), and while the relationship between weather and BRD is poorly understood, [7] it is often suggested to avoid transporting cattle during extreme weather. [16]
Pasteurellosis is an infection with a species of the bacterial genus Pasteurella, which is found in humans and other animals.
Kennel cough is an upper respiratory infection affecting dogs. There are multiple causative agents, the most common being the bacterium Bordetella bronchiseptica, followed by canine parainfluenza virus, and to a lesser extent canine coronavirus. It is highly contagious; however, adult dogs may display immunity to reinfection even under constant exposure. Kennel cough is so named because the infection can spread quickly among dogs in the close quarters of a kennel or animal shelter.
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.
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.
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.
Florfenicol is a fluorinated synthetic analog of thiamphenicol, mainly used as a antibiotic in veterinary medicine.
Pasteurella multocida is a Gram-negative, nonmotile, penicillin-sensitive coccobacillus of the family Pasteurellaceae. Strains of the species are currently classified into five serogroups based on capsular composition and 16 somatic serovars (1–16). P. multocida is the cause of a range of diseases in mammals and birds, including fowl cholera in poultry, atrophic rhinitis in pigs, and bovine hemorrhagic septicemia in cattle and buffalo. It can also cause a zoonotic infection in humans, which typically is a result of bites or scratches from domestic pets. Many mammals and birds harbor it as part of their normal respiratory microbiota.
Cefquinome is a fourth-generation cephalosporin with pharmacological and antibacterial properties valuable in the treatment of coliform mastitis and other infections. It is only used in veterinary applications.
Veterinary virology is the study of viruses in non-human animals. It is an important branch of veterinary medicine.
Tulathromycin, sold under the brand name Draxxin among others, is a macrolide antibiotic used to treat bovine respiratory disease in cattle and swine respiratory disease in pigs.
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.
ATCvet code QI02Immunologicals for Bovidae is a therapeutic subgroup of the Anatomical Therapeutic Chemical Classification System for veterinary medicinal products, a system of alphanumeric codes developed by the World Health Organization (WHO) for the classification of drugs and other medical products for veterinary use. Subgroup QI02 is part of the anatomical group QI Immunologicals.
Haemorrhagic septicaemia (HS) is one of the most economically important pasteurelloses. Haemorrhagic septicaemia in cattle and buffaloes was previously known to be associated with one of two serotypes of P. multocida: Asian B:2 and African E:2 according to the Carter-Heddleston system, or 6:B and 6:E using the Namioka-Carter system.
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 recepter. 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.
Mannheimia varigena is a bacterial species, predominantly encountered in ruminants and historically classified within the former bacterial Pasteurella haemolytica complex, a group of bacteria involved in bovine respiratory disease (BRD). It is pathogenic.
Pseudocowpox is a disease caused by the Paravaccinia virus or Pseudocowpox virus, a virus of the family Poxviridae and the genus Parapoxvirus. Humans can contract the virus from contact with livestock infected with Bovine papular stomatitis and the disease is common among ranchers, milkers, and veterinarians. Infection in humans will present with fever, fatigue, and lesion on the skin.
Mycoplasma bovis is one of 126 species of genus Mycoplasma. It is the smallest living cell and anaerobic organism in nature. It does not contain any cell wall and is therefore resistant to penicillin and other beta lactam antibiotics.
Histophilus somni is a non-motile, gram-negative, rod or coccobacillus shaped, facultative anaerobe bacterial species belonging to the family Pasteurellaceae. Prior to 2003, it was thought Haemophilus somnus, Histophilus ovis, and Histophilus agni were three different species, but now are all classified as Histophilus somni. Histophilus somni is a commensal bacteria of mucous membranes of the upper respiratory tract and reproductive tract with a global prevalence and is found in cattle and other small ruminants. Histophilus somni is also a known causative agent that is a part of the Bovine Respiratory Disease (BRD) complex, which typically involves multiple pathogens residing together in biofilm environments. Histophilus somni may also cause Histophilosus symptoms and clinical presentation will depend on the tissue affected. When disease does occur, it can be difficult to catch in time and is often diagnosed on post mortem. This means that treatment often involves metaphylactic mass treatment or no treatment at all. This organism is more fastidious than others and requires knowledge for sample collection, storage and culture. Genomic studies related to this bacteria have enabled scientist to pin point antibiotic resistance genes.
Bovine respiratory syncytial virus (BRSV) is pneumovirus closely related to human respiratory syncytial virus (RSV) that is a common cause of respiratory disease in cattle, particularly calves. It is a negative-sense, single-stranded RNA virus that replicates in the cytoplasm of the cell. Similarly to other single-stranded RNA viruses, the genome of BRSV has a high mutation rate, which results in great antigenetic variation. Thus, BRSV can be split into four different subgroups based on antigen expression.