EPIZOOTIC HAEMORRHAGIC DISEASE

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Context: Epizootic haemorrhagic disease (EHD) has caused more than 150 outbreaks in Spain, Portugal and southern Italy since November last year. The disease affects cows, deer and sheep and is transmitted by midges that carry the virus.

Details

• The UK's Department for Environment, Food and Rural Affairs (DEFRA) says that climate change may have led to warmer summers that favour the midges' survival and reproduction.
• It also warns that the disease is moving towards the northern regions of Spain, such as Basque, Aragon and Catalonia, where there are many cattle farms and where France is nearby.

Epizootic Hemorrhagic Disease (EHD)

About

• Epizootic Hemorrhagic Disease (EHD) was first identified in the United States in the 1950s.
• It is caused by viruses belonging to the Orbivirus genus and is primarily transmitted through the bites of infected midges (Culicoides species). These midges serve as vectors for the virus, transmitting it from one animal to another.
• Over time, EHD has spread to various parts of the world, including parts of Africa and the Middle East.
• EHD primarily affects ruminant animals, such as cattle, deer, sheep, and goats. The symptoms of EHD can vary in intensity depending on the severity of the infection.

Picture Courtesy: www.mdpi.com

Symptoms of EHD

• Fever: When cattle are infected with EHD, they often exhibit an elevated body temperature. This fever is a physiological response to the presence of the virus in their system. The rise in body temperature is one of the initial indicators of infection.
• Weakness: Affected cattle typically become noticeably weak and lethargic. This weakness can manifest as reduced physical activity, difficulty standing, and an overall lack of energy. It is a consequence of the virus's impact on the animal's overall health.
• Lack of Appetite: EHD-infected cattle frequently experience a significant loss of appetite. They may display a reluctance to eat and drink, resulting in reduced food intake. This decreased interest in food can lead to weight loss over time.
• Difficulty Swallowing: Some infected cattle may struggle with swallowing due to the presence of oral lesions caused by the disease. These lesions can make eating and drinking a painful and challenging process for the animal. This symptom can further contribute to the overall decline in their health.
• Skin Rash on Udder: EHD can cause skin lesions, including a rash, to develop on the udder and other areas of the cattle's body. These lesions may appear as raised or discoloured areas on the skin and can be visually observed. Skin abnormalities like these can serve as external markers that veterinarians use to diagnose EHD.
• In severe cases, EHD can lead to complications and even death in cattle. The progression and outcome of the disease can vary from one infected animal to another.

Impact on affected livestock populations and the agricultural industry

Morbidity and Mortality

• EHD can have a devastating effect on livestock such as cattle, sheep, deer, and other susceptible animals. Infected animals often experience a range of symptoms, and in severe cases, the disease can be fatal.
• The morbidity and mortality rates can vary depending on the virulence of the virus and the overall health of the affected animals. High mortality rates can result in substantial losses within affected herds or populations.

Trade Restrictions

• Outbreaks of EHD can lead to trade restrictions and limitations on the movement of animals, both domestically and internationally. These measures are implemented to prevent the spread of the disease to unaffected areas.
• Trade restrictions can disrupt the livestock trade, impacting farmers, ranchers, and the broader agricultural industry. Additionally, limitations on the movement of animals can complicate breeding programs and livestock management.

Economic Losses

• The economic impact of EHD on the agricultural industry can be significant. Infected animals may experience reduced productivity, such as decreased weight gain in cattle or lower milk production in dairy cows.
• In severe cases, infected animals may need to be culled or euthanized to prevent further spread of the disease, resulting in direct financial losses for farmers and ranchers. Additionally, the costs associated with veterinary care, diagnostic testing, and disease management can add to the economic burden.

Epizootic Hemorrhagic Disease (EHD) presents several challenges

Vector-Borne Transmission

• EHD is primarily transmitted by biting midges (Culicoides spp.), which are small insects. Controlling the spread of EHD can be challenging because it requires addressing the vector population. Midges are highly mobile and can travel significant distances, making it difficult to prevent their movement and the transmission of the virus from infected to susceptible animals.
• Vector control measures, such as insecticide treatments and habitat management, may be used to mitigate this challenge.

Environmental Factors

• Environmental conditions play a crucial role in the epidemiology of EHD. Factors like temperature, humidity, and the presence of suitable breeding sites for midges can influence the prevalence and activity of the vector population.
• Warmer and wetter conditions can create more favourable environments for midges to breed and transmit the virus. This makes the disease's occurrence and severity highly dependent on local environmental conditions.

Climate Change

• Climate change is a significant concern when it comes to EHD. As global temperatures rise, it can lead to the expansion of suitable habitats for midges and extend their activity periods.
• Warmer summers, in particular, can create conditions that are conducive to both midge proliferation and the spread of EHD. This means that regions that were previously unaffected by EHD may become at risk due to changing climate patterns.
• Adaptation and preparedness measures are necessary to address these changing dynamics, including monitoring and early warning systems.

Cure and Prevention

• There is no specific cure for EHD, and treatment primarily focuses on supportive care for affected animals.

Vector Control

• Insecticide Application: Applying insecticides to livestock and their surroundings can help reduce midge populations. These insecticides can target adult midges and larval stages in breeding sites.
• Environmental Management: Proper environmental management is crucial. Eliminating stagnant water sources where midges breed, such as puddles and waterlogged areas, can reduce breeding opportunities. Additionally, improving ventilation and creating barriers, like fine mesh screens, to keep midges away from livestock facilities can be effective.

Vaccination

• In some regions, vaccines against specific strains of EHD have been developed and used as part of disease prevention strategies. These vaccines are administered to susceptible animals and can help reduce the severity of the disease if they are exposed to the virus.
• The efficacy of these vaccines can vary depending on the specific strain of EHD virus in the area and other factors. Vaccination programs are typically carried out by veterinarians and are a valuable tool in areas with a history of EHD outbreaks.

Movement Restrictions

• Implementing movement restrictions on livestock from areas affected by EHD is a crucial step in preventing the spread of the disease. This involves limiting the movement of animals out of affected regions to prevent them from carrying the virus to new areas. The extent of these restrictions can vary depending on the scale of the outbreak and the risk of disease transmission.
• Government agencies and veterinary authorities typically oversee and enforce these restrictions.

Surveillance and Early Detection

• Monitoring and surveillance of livestock populations and midge populations are vital for early detection of EHD outbreaks. Veterinarians, livestock producers, and government agencies collaborate to monitor for signs of the disease in animals and to track the presence of midges.
• Early detection allows for prompt intervention and the implementation of control measures.

Education and Awareness

• Raising awareness among farmers, livestock producers, and veterinarians about the risks associated with EHD and the importance of implementing preventive measures is critical. This educational effort includes teaching individuals about the clinical signs of EHD, the necessity of reporting suspected cases, and the value of vaccination in high-risk areas.

Way Forward

• The management and control of EHD require collaborative efforts among veterinarians, farmers, and government agencies.
• Monitoring and surveillance of both the disease and the midge vectors are crucial to detect outbreaks early and implement control measures.
• Research into more effective vaccines and treatments remains important to combat the disease's impact on livestock and prevent potential economic losses.
• Climate change adaptation strategies and vector control measures will also be essential in regions where EHD is a concern due to its association with environmental conditions and vector abundance.

PRACTICE QUESTION Q. Consider the following statements in the context of the Epizootic Hemorrhagic Disease (EHD) 1. It is caused by viruses belonging to the Orbivirus genus. 2. It is primarily transmitted through the bites of infected midges (Culicoides species). 3. It primarily affects ruminant animals, including cattle, deer, sheep, and goats. 4. There is no specific cure for EHD, and treatment primarily focuses on supportive care for affected animals. How many of the above statement is/are correct? A) Only one B) Only two C) Only three D) All four Answer: D Explanation: Statements 1 and 2 are correct: EHD is caused by viruses that belong to the Orbivirus genus. These viruses are part of the Reoviridae family and are responsible for causing the disease in ruminant animals.  EHD is primarily transmitted through the bites of infected midges, specifically Culicoides species. These tiny insects serve as vectors, carrying the virus from one animal to another when they feed on blood. Statement 3 is correct: EHD primarily affects ruminant animals, which include cattle, deer, sheep, and goats. These animals are particularly susceptible to the disease, and outbreaks can result in significant morbidity and mortality in affected populations. Statement 4 is correct: There is no specific cure for EHD. When animals are infected, treatment primarily involves providing supportive care to manage their symptoms and help them recover. This may include addressing fever, dehydration, and other clinical signs to improve the animal's overall condition.

https://news.sky.com/story/epizootic-haemorrhagic-disease-uk-authorities-closely-monitoring-spread-of-fatal-cow-disease-in-europe-12960340 

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