Index IntroductionPrevalence of the Disease in the United States and WorldwideMechanisms of TransmissionDiagnosisSigns and SymptomsTreatment, Control, and PreventionSummary and ConclusionIntroductionThe bluetongue virus originates from the Orbivirus genus of the Reoviridae family. Bluetongue virus is a non-zoonotic disease of ruminants such as sheep, cattle and deer that is believed to have originated in South Africa as early as the 18th century. This virus was initially known as “epizootic catarrh” and was later called “sheep malarial bluetongue”. However, in 1905 it was renamed "blue tongue" due to the swollen, cyanotic tongue characteristic of infected animals. Bluetongue is a vector-borne disease that can infect most ruminants and camelids, but is most common in white-tailed deer and sheep breeds in the United States. Bluetongue virus is closely related to haemorrhagic diseases but has different characteristics than epizootic haemorrhagic disease (EHD) virus. The haemorrhagic disease is caused by two orbiviruses known as epizootic haemorrhagic disease virus and bluetongue virus. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay Prevalence of the disease in the United States and around the world The spread of the bluetongue virus around the world corresponds to the geographic and physical distribution of the vector species of midge biting Culicoides, which are the only significant natural transmitters of the virus. In the United States, prevalence is high in Southern and Western regions due to frequent or diverse exposure to the serotype. However, most infections are reported with mild or inapparent disease. The disease is most often found in sheep, sometimes in goats, and occasionally in cattle. However, bluetongue virus is commonly found in white-tailed deer in the Kentucky and Tennessee areas, with some cases reported in cattle in Texas and Ohio. In places like Africa, bluetongue viruses are broadly divided into Western and Eastern lineages based on phylogenetic analysis of nucleotide sequences. The prevalence of the bluetongue is closely related to tropical and subtropical regions where certain climatic conditions can support large quantities of midge species that largely depend on the distribution of vector-competent species and climatic conditions. Mechanisms of transmission Bluetongue virus is a non-contagious disease that is transmitted by insects called biting midges. Midges become infected with the bluetongue virus by ingesting the blood of infected ruminants. Once the midges ingest a blood meal, they pass the infection on to their next host, which is how bluetongue spreads. In the United States, midges are found in the months and temperatures of late summer and early fall. Approximately 1,400 species of these biting midges of the Culicoides genus have been identified, however only 30 have been shown to transmit the bluetongue virus. Biting midges are commonly found in mud around or near ponds, lakes and other water sources for animals. When there are severe droughts, animals don't get as much hydration as they need from the forage they graze, so they seek out water sources more often, which puts them at greater risk of infection from biting midges. Until recently, it was thought that the disease was not spread through direct contactbetween animals. However, there is a possibility that this is no longer accurate. Although the bluetongue virus is known to be transmitted exclusively by female bloodsucking midges, a strain has recently been identified that may well be transmitted by direct contact. Transplacental infection can occur and, depending on the gestation period until the fetus becomes infected, can occur can cause stillbirths and miscarriages. Bluetongue virus infects endothelial cells of blood vessel walls and mononuclear phagocytic and dendritic cells. This causes vascular thrombosis, tissue infection, necrosis and hemorrhage. Infection rates are higher than ever due to the recent increase in drought conditions which have created the perfect environment for these insects to spread the disease. Diagnosis There are many different ways to diagnose the bluetongue virus. Diagnostics rely heavily on laboratory techniques, including isolation of BTV and demonstration of antigens, viral nucleic acids and antibodies. Using blood samples or samples from the spleen, lung, or lymph node tissue is a small choice. However, bluetongue is often diagnosed based on the signs and symptoms of each species it infects. Samples such as sperm from male animals can also be used for diagnostic purposes if collected at peak viremia. Bluetongue can also be diagnosed by petechiae, ecchymoses, and hemorrhages in the wall of the base of the pulmonary artery, as well as by necrosis of the papillary muscle of the left ventricle of the heart. Pathogenesis Bluetongue virus infects monocytes both in vivo and in vitro and can interact with the target cell surface via VP2 trimers that bind to cell surface glycoproteins. Once BTV replicates in the lymph nodes where it drains the inoculation sites, it travels to secondary sites such as the lungs and spleen. Here it replicates in the endothelium and in mononuclear phagocytes. Since then, the bluetongue virus can disperse into the lymph and blood where it can be found in the intracellular vesicles of erythrocytes. At this point it does not replicate but persists in the folds of cell membranes. In sheep and cattle BTV can be detected in blood for 35-60 days and in viral structures for up to 160 days. It can be said that erythrocytes could be the critical mechanism by which cattle serve as a natural host reservoir of bluetongue virus because BTV RNA is remotely similar to the lifespan of erythrocytes in cattle. Signs and Symptoms Deer infected with the bluetongue virus are known to be depressed, feverish, emaciated, and remain near water in late summer or early fall. In many cases, the hooves of infected animals become painful, making it very difficult for the animals to move. In some cases the hooves even fall off. Bluetongue virus can also cause swelling of the head, neck, tongue and eyelids, difficulty breathing and internal bleeding. Swelling of the tongue can cause it to turn blue due to lack of blood supply. In sheep, vascular endothelial damage is often observed, causing alterations in capillary permeability and coagulation. Typical clinical signs in sheep may also include edema, congestion, inflammation, necrosis and haemorrhage. Young lambs have a higher mortality rate and may show signs of lameness and depression. Infected sheep are known to eat less and even hold food in their mouths to soften it before chewing due to oral pain. In sheep, mortality varies from 2 to 30% and occasionally can reach 70%. Clinical signs in cattle.