Introduction:
Bluetongue virus, a devastating disease that affects cattle and sheep, is primarily transmitted by tiny flies known as biting midges or no-see-ums. These flies were previously believed to disappear during the winter months, but groundbreaking research has now shown that they remain active even in colder temperatures. This discovery has significant implications for understanding the persistence and transmission of the virus, which has led to trade restrictions on U.S. cattle and cattle products in some parts of the world. In this blog post, we will explore the findings of the study and discuss potential management strategies to mitigate the spread of the Bluetongue virus.
Persistence of Bluetongue Virus:
Bluetongue virus is prevalent in cattle across various regions of the United States, particularly in the southwestern states like California, where nearly 20% of some cattle herds are infected. The virus causes symptoms such as elevated body temperature, lethargy, bleeding around the mouth, and the characteristic blue discoloration of the tongue in sheep. While not all infected animals die, the disease poses a significant threat to livestock health and has severe economic consequences.
Transmission by Biting Midges:
Biting midges are responsible for transmitting the Bluetongue virus. These tiny flies, also known as no-see-ums, have a short lifespan of fewer than 30 days as adults. In previous studies, researchers found limited midge activity during winter in California, leading to two competing theories. One proposed that the virus-carrying midges die off during colder months and are reintroduced from tropical regions with warmer winters. The other theory suggested that midge activity persists throughout the winter, but current surveillance methods fail to capture their reduced activity and ongoing virus transmission.
Unveiling Year-Round Midge Activity:
To address these theories, a research team from UC Riverside and Scripps College conducted a comprehensive study, deviating from conventional entomological practices. They focused on trapping midges on the warmest days of each week during winter for three consecutive years. Surprisingly, the researchers consistently caught active midges, challenging the notion that their activity ceases in winter. Furthermore, the presence of younger adult midges indicated that they continue to develop during the winter months without any interruption in their life cycle.
Implications for Virus Transmission Management:
Although this study did not detect active virus in winter, another study conducted in California's Central Valley found virus presence during this time. Collectively, these studies indicate that the transmission of the Bluetongue virus likely persists year-round. With no specific treatment available for the disease and no identified natural enemy of the midges to control their population, managing virus transmission becomes crucial.
The Importance of Understanding Insect Behavior:
The recent research findings shed light on the behavior of Bluetongue virus-carrying midges. This knowledge is invaluable for implementing effective strategies to curb virus transmission. One potential approach is the application of insect repellants to ruminant animals during winter, when midge activity reaches its lowest point of the year. Such preventive measures can help mitigate the risk of new strains being introduced to susceptible populations, potentially causing severe reactions and significant economic impacts.
Conclusion:
Enhancing our understanding of the behavior and persistence of Bluetongue virus-carrying midges is critical for effectively managing the spread of this incurable disease. The recent study demonstrated that these midges remain active even in winter, challenging previous assumptions. This knowledge can guide the development of improved strategies to reduce virus transmission, such as the use of insect repellants during periods of reduced midge activity. By staying vigilant and implementing proactive measures, we can protect livestock and prevent potential economic losses associated with Bluetongue virus outbreaks.