Equine Viral Arteritis: Symptoms and Treatment Unveiled

Equine viral arteritis (EVA) is a significant concern for horse owners and breeders worldwide, caused by the Equine Arteritis Virus (EAV). This article delves into the intricacies of Equine viral arteritis - Symptoms and treatment, providing comprehensive information on its manifestations, diagnostic approaches, and effective management strategies to safeguard equine health.

Understanding Equine Arteritis Virus (EAV)

The Equine Arteritis Virus (EAV) is a single-stranded RNA virus belonging to the Arterivirus genus. It primarily affects the respiratory and reproductive systems of horses. EAV is highly contagious and can spread through direct contact, aerosols, and contaminated fomites. The virus can also be transmitted venereally from persistently infected stallions to mares during breeding. Understanding the transmission routes is crucial for effective prevention and control measures.

Transmission Pathways of EAV

• Respiratory Droplets: Infected horses can shed the virus in nasal secretions, which are then dispersed as aerosols during coughing and sneezing. Inhalation of these contaminated droplets is a primary mode of transmission, especially in environments where horses are housed closely together, such as stables, yards, and competition venues.
• Direct Contact: Close physical contact between horses can facilitate the spread of the virus. This includes nose-to-nose contact, mutual grooming, and sharing of feed and water troughs.
• Venereal Transmission: A significant concern for breeding operations is the venereal transmission of EAV. Stallions that are persistently infected can shed the virus in their semen. Mating with an infected stallion can lead to the infection of mares, often resulting in abortion or the birth of weakened foals. Even artificial insemination using contaminated semen can pose a risk.
• Contaminated Fomites: The virus can survive on surfaces and equipment for a period, meaning that contaminated tack, grooming tools, clothing, and even vehicle interiors can act as vectors for transmission. Rigorous biosecurity protocols are therefore essential.
• In Utero Transmission: While less common than other routes, foals can potentially be infected in utero if the mare is infected during gestation. This can lead to abortion or the birth of a weak foal that may shed the virus.

Clinical Manifestations: Equine Viral Arteritis - Symptoms

The presentation of Equine viral arteritis - Symptoms and treatment can vary significantly, ranging from asymptomatic infections to severe, life-threatening conditions. The severity of clinical signs often depends on factors such as the strain of EAV, the age and immune status of the horse, and whether it is a primary infection or a reinfection.

Acute and Subclinical Forms

• Acute Form: This is the most recognizable form of EVA. Horses exhibiting acute symptoms typically display a sudden onset of fever, often exceeding 102.2°F (39°C). This is usually followed by lethargy and a general loss of appetite. A characteristic sign is limb edema, particularly affecting the hind limbs and sometimes extending to the abdomen and scrotum in stallions. Swelling of the eyelids and nasal edema can also occur. Horses may develop a nasal discharge, which can initially be clear but may become mucopurulent. Coughing and signs of respiratory distress, such as increased respiratory rate and effort, can also be observed. The conjunctiva may appear injected and inflamed.
• Subclinical Form: A significant proportion of horses infected with EAV develop a subclinical infection, meaning they show no or very mild symptoms. These horses can still shed the virus and act as carriers, unknowingly spreading it within a population. This makes controlling outbreaks particularly challenging, as the virus can circulate silently. Subclinically infected mares can still experience reproductive losses without owners realizing the underlying cause.

Reproductive Impact

The impact of EVA on reproduction is a major concern for the equine industry.

• Abortion: Pregnant mares infected with EAV are at high risk of aborting their foals, often late in gestation. The aborted fetus may show signs of widespread vascular damage.
• Neonatal Foal Mortality: Foals born to infected mares, or those infected shortly after birth, can be weak, lethargic, and may die from severe pneumonia or other complications.
• Infertility in Stallions: Infected stallions can experience temporary infertility and may shed the virus in their semen for extended periods, posing a significant risk to mares.

Other Potential Signs

• Skin Lesions: In some cases, urticarial (hives) or petechial hemorrhages (small pinpoint hemorrhages) may be observed on the skin, particularly on the neck and flanks.
• Gastrointestinal Disturbances: While less common, some horses may exhibit colic-like signs or diarrhea.

Diagnostic Approaches for Equine Viral Arteritis

Accurate diagnosis is crucial for effective management and control of EVA outbreaks. Several diagnostic methods are available, often used in combination to confirm infection.

Serological Testing

• Virus Neutralization Test (VNT): This is considered the gold standard for detecting antibodies against EAV. It measures the ability of a horse's serum to neutralize the virus in vitro. A four-fold rise in antibody titers between paired serum samples taken a few weeks apart is indicative of a recent infection.
• Enzyme-Linked Immunosorbent Assay (ELISA): ELISA tests are widely used for screening purposes. They are faster and more cost-effective than VNT but may be less specific. Positively identified horses may require confirmation by VNT.

Viral Detection Tests

• Polymerase Chain Reaction (PCR): PCR assays can detect the presence of EAV genetic material in biological samples, such as nasal swabs, semen, and aborted fetal tissues. This test is highly sensitive and specific and is valuable for identifying actively shedding animals, especially in the early stages of infection or in asymptomatic carriers.
• Virus Isolation: This involves culturing the virus from clinical samples in a laboratory setting. While definitive, it is a more time-consuming and technically demanding method compared to PCR.

Managing Equine Viral Arteritis - Treatment and Prevention

Currently, there is no specific antiviral drug that effectively cures EVA. Therefore, Equine viral arteritis - Symptoms and treatment focuses on supportive care, prevention of spread, and biosecurity measures.

Supportive Care for Infected Horses

The primary goal of treatment is to alleviate symptoms and support the horse's immune system during the infection.

• Rest: Affected horses should be given complete rest to allow their bodies to recover.
• Fluid Therapy: Intravenous fluids may be administered to combat dehydration, especially in horses with fever and reduced appetite.
• Anti-inflammatory Medications: Non-steroidal anti-inflammatory drugs (NSAIDs) like phenylbutazone or flunixin meglumine can be used to reduce fever and inflammation, thereby improving comfort.
• Antibiotics: Secondary bacterial infections can complicate EVA. Antibiotics may be prescribed to prevent or treat these complications, particularly if pneumonia or other bacterial infections are suspected.
• Nutritional Support: Ensuring adequate hydration and providing easily digestible feed is important. In severe cases, nutritional support via nasogastric tube may be necessary.

Biosecurity and Control Measures

Preventing the introduction and spread of EAV is paramount. This involves a multi-faceted approach.

• Vaccination: An effective EAV vaccine is available and is a cornerstone of prevention. Vaccination protocols should be discussed with a veterinarian, considering the prevalence of EAV in the region and the horse's intended use. Vaccination can reduce the severity of clinical signs and decrease viral shedding, but it does not always prevent infection entirely. Importantly, vaccinated horses may still test positive for antibodies.
• Quarantine: New horses entering a facility should be quarantined for a minimum of 21 days. During quarantine, they should be tested for EAV and monitored for any clinical signs.
• Testing and Monitoring: Regular testing of breeding stock, especially stallions, is crucial. Monitoring antibody titers in breeding herds can help detect outbreaks early.
• Hygiene and Disinfection: Strict hygiene protocols are essential. This includes thorough cleaning and disinfection of stables, equipment, and vehicles. Disinfectants effective against EAV should be used.
• Movement Control: During an outbreak, restricting the movement of horses into and out of affected premises is vital to prevent further spread.
• Breeding Management:
  • Stallions should be tested regularly for EAV, especially before the breeding season.
  • Mares should ideally be vaccinated before breeding.
  • Consider the EAV status of both the stallion and the mare.
  • If a stallion is found to be shedding EAV, he should be isolated, and breeding activities halted until he is no longer shedding.
  • Artificial insemination can reduce direct contact between horses, but semen must be tested for EAV.

Managing Persistently Infected Stallions

Persistently infected stallions are a major source of EAV transmission. Identifying and managing these animals is critical.

• Testing: Regular testing of semen and blood is necessary.
• Isolation: Persistently infected stallions should be isolated from non-infected horses.
• Breeding Restrictions: Their use for breeding may need to be restricted or managed with extreme caution using artificial insemination with rigorously tested semen.

The Role of Veterinarians

Veterinarians play a critical role in diagnosing, managing, and controlling EVA. They can:

• Provide accurate diagnosis through appropriate testing.
• Develop tailored treatment plans for infected horses.
• Advise on effective biosecurity measures and vaccination strategies.
• Assist in outbreak investigation and control.
• Educate owners on the risks and management of EVA.

In summary

Equine viral arteritis is a complex and potentially devastating disease that requires a proactive and informed approach from horse owners and managers. A thorough understanding of Equine viral arteritis - Symptoms and treatment, coupled with stringent biosecurity protocols, appropriate testing, and vaccination, are the most effective tools in preventing its spread and minimizing its impact on equine populations. Early detection and prompt intervention are key to safeguarding the health and reproductive potential of horses.