Viral biological control is the implementation of viruses to control or deplete pest populations. Viruses have high host specificity allowing targeted infections that are unlikely to impact other organisms. Viral biological control methods are studied and used globally, for sustainable agricultural practices, controlling invasive species, and disease management in humans and food. Viral biological control is heavily researched as alternative methods to chemical pest control methods, as viruses are made from natural genetic material and will biodegrade. Whereas researchers are using viruses as a selective control protocol when targeting invasive species. Bacteriophages are being implemented and explored to combat diseases and food borne diseases.
History Viral biological control methods may have been studied as early as 2700 BC in China for pest control management for silkworms. However, the earliest documented case of viral pest control was recorded in the late 1800s and early 1900s. The first use of viruses for insect pest management occurred in 1892 when nuclear polyhedrosis viruses were released in Germany to protect pine trees from Lymantria monacha, Black arches. Virus implementations as pesticides have been studied around the world as pests are a global issue impacting all types of terrains, climates, and organisms. In 1896, the first findings of bacteriophage, bacterial viruses, and antibacterial elements were in the Ganges and Jumna rivers in India; scientists took note of the decline in Vibrio cholerae, cholera, and later identified Utilization of bacteriophages, for combating bacterial infections of plants was documented in 1924 when scientists Mallman and Hemstreet, discovered a liquid secreted by cabbage preventing rot from Xanthomonas campretris, Black rot. The following year, scientists Kotila and Coons isolated phages directed against Pectrobactrium carotovorum, Blackleg disease, in potatoes. In the early 1960s, after beginning research in the 1950s, scientists in China utilized multiple viruses, including for Agrotis segetum and Apamea sordens, to target insect pests, to protect agriculture, pastures, and gardens. The first usage of viruses as biological pest control in the United States was in 1970 when viral-based insecticides were used to deplete the population of Helicoverpa armigera, Cotton Bollworm, a voracious moth that eats cotton and other crops.
Animals Invasive animals are a global issue causing ecological damage and filling niches of indigenous species. Utilizing viruses to control animal population reduces invasive populations and reduces animal vectors for diseases.
Insects Insects are the main vectors for spreading diseases for all organisms. Insect vectors disperse pathogens through their travel, direct contact, and interaction with organisms. In China, over 32 virus species are implemented for biological control to uphold agriculture, forestry, and domestic areas in China, and have a .2% prevalence in China’s overall insecticide protocols. These insect viruses, include Helicoverpa armigera nucleopolyhedrovirus, Mamestra brassicae nucleopolyhedrovirus, Sprodoptera litura nucleopolyhedrovirus, and Periplaneta fuliginosa densovirus, and many of these viruses were genetically altered to increase infection rate and resistant to UV-light, a main obstacle as most viruses are UV-light sensitive. Various species of Lepidoptera such as Spodoptera exempta, the African armyworm, and Lymantria dispar dispar, the gypsy moth; both have higher reproduction rates and have sporadic outbreaks causing ecological destruction. They found Spodoptera exempta are most susceptible to neuropolyhedrovirues at the larvae stage, and the virus can be transmitted both horizontally and vertically, remaining latent until sudden expression of the virus. Triggers to the expression or infection of the virus in case of vertical transmission remain unknown. Similar studies found neuropolyhedrovirues to affect Spodoptera exempta, aiding in large outbreaks, but noted high tannin levels, a chemical found in woody plants, reduced viral virulence.
Mammals
Rodents are a leading invasive species as vectors of pathogens, filling habitat niches, and overgrazing plants. Oryctolagus cuniculus, European rabbits, were introduced to Australia in 1788 as livestock and released for Europeans to hunt. Soon, the rabbits became widespread and changed Australia's ecological systems from overgrazing. In the 1950s, researchers implemented Myxoma virus (MYXV), a virus indigenous to South America that is transmitted by arthropods like mosquitoes, fleas, and ticks, to reduce rabbit populations. The virus did not transmit well and died off during this first attempt. However, scientists implemented the Myxoma virus in Europe where Oryctolagus cuniculus is also abundant and destructive, and found more promising results. Europe is more humid, thus attracting more arthropod vectors, whereas the area they dispersed in Australia is more arid, and they are released during the fall season in Australia. However, researchers continue investigating the Myxoma virus along with other viruses that will manage the Oryctolagus cuniculus populations and other hare populations globally. Other virus studies include Californian MYXV, Rabbit Fibroma Virus, Hare Fibroma Virus, Squirrel Fibroma Virus, and other species of Leporipoxvirus. Similar to the Myxoma virus, most are transmitted by arthropods like mosquitoes, mites, fleas, and ticks, but target different parts of the hare.
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