Hendra Virus infection in horses

Hendra virus infection is an emerging viral disease of horses and humans in Australia. Although this disease is uncommon, cases have been reported periodically since it was first recognized in 1994

Hendra Virus is a zoonotic disease; that is the disease can be transmitted from horses to humans during close contact with an infected horse. Hendra virus is a zoonotic disease that can be transmitted from horses to humans.

Etiology
Hendra virus (HeV) is a member of the genus Henipavirus in the family Paramyxoviridae. This genus includes the closely related Nipah virus.


Transmission
Horses and humans seem to be spillover hosts for Hendra virus. Bats of the genus Pteropus (fruit bats/ flying foxes) appear to be the reservoir hosts.
In flying foxes, Hendra virus has been isolated from blood, fetal tissues and uterine fluids, and unpublished research also reports the virus in urine, feces and saliva

Clinical Signs
Two syndromes, one characterized primarily by respiratory disease and the other mainly by neurological signs, have been reported in horses

• Fever
  
• Lethargy
  
• Respiratory distress
  
• Frothy nasal discharge
• Increased heart rate
  
• Increased respiratory rate
  
• Jaundice

Treatment and prevention

• These is no specific antiviral drugs available
  
• Vaccination is the best defense against Hendra virus infection and horse owners should discuss their options with their veterinarian
• Horse feed and water troughs should be relocated to areas away from where bats feed or roost.
• Culling of infected animals
• Sick horses should be isolated
• Protective mask,gloves, eyewears should be worn when handling sick animals.

Eastern equine encephalitis (EEE)

The equine encephalitis viruses are mosquito transmitted diseases that can cause severe inflammation of the brain. Eastern equine encephalitis (EEE) most commonly occurs in the Eastern United States and Canada.
Equine encephalitis viruses closely related to venezulean equine encephalitis virus

Causes
The Togaviradae virus found in wild birds, transmitted to horses and humans via the bite of an infected mosquito, causes EEE and WEE

Signs

• Fever
  
• Drowsiness
  
• Muscle twitches
  
• Drooping ears
  
• Circling
  
• Paralysis of the pharynx, larynx and tongue are common
  
• Head pressing
  
• Paralysis

Prevention

• Vaccines for EEE, WEE, and VEE are available for horses.
  
• Measures to control mosquito populations and minimize mosquito exposure will decrease chances of infection
  
• Remove standing water
  
• Insect repellents can be used

Treatment

• There is no cure for EEE
  
• Corticosteroids, anticonvulsants can be given
  
• Intra venous fluid therapy can be given
  
• Antipyeretics can be given to reduce fever.
  

VESICULAR STOMATITIS

Vesicular Stomatitis (VS) is a contagious disease that afflicts horses, livestock, wildlife and even humans.

The disease is caused by a virus which although rarely life threatening, can have significant financial impact on the horse industry.

Clinical Signs & Diagnosis

Blister-like lesions develop on the tongue, mouth lining, nose and lips.

In some cases, lesions also develop on the coronary bands, or on the udder or sheath.

When VS is suspected, an exact diagnosis should be obtained by testing the blood for virus-specific antibodies.

The incubation period for vesicular stomatitis – meaning the time from exposure until the first signs appear – ranges from two to eight days.

A fever may develop initially as blisters form on the tongue, gums, or coronary bands.

One of the most obvious clinical signs is drooling or frothing at the mouth. This occurs following rupture of the blisters that create painful ulcers in the mouth. The surface of the tongue may slough.

Excessive salivation is often mistaken as a result of a dental problem just as a horse that is not eating well may be suspected as having colic.

Weight loss may be a secondary effect, as a horse with mouth ulcers finds it too painful to eat. If lesions form around the coronary band, inflammation within the foot may result in lameness or laminitis. In severe (but rare) cases, the lesions on the coronary band may cause the hoof to slough.

Treatment

While a horse is suffering from vesicular stomatitis, feeding soft feeds may reduce mouth discomfort.

Anti-inflammatory medications as supportive care help to minimize swelling and pain so a horse will continue to eat and drink.

Secondary bacterial infection of ulcerated areas is another concern.

If fever, swelling, inflammation or pus develops around the sores, treatment with antibiotics may be required.

Disease Transmission

There are still many questions regarding how vesicular stomatitis is transmitted.

The disease is distributed only in North and South America, with a greater incidence in warmer regions.

Due to the seasonal occurrence of VS during summer through early fall, it is believed that insects such as biting flies and gnats transmit the virus.

Stable and houseflies are other possible but unlikely vectors. VS also seems to be passed from horse to horse by contact with saliva or fluid from ruptured blisters.

Physical contact between animals, or contact with buckets, equipment, housing, trailers, feed, bedding or other items used by an infected horse can provide a ready means of spread.

Prevention

• Healthy horses are more disease resistant so provide good nutrition, regular exercise, deworming and routine vaccinations.

• Isolate new horses for at least 21 days before introducing them into the herd or stable.

• Observe your horse closely. Immediately isolate any horse that shows signs of infection.

• Implement an effective insect control program. Keep stabling areas clean and dry. Remove waste and eliminate potential breeding grounds (standing water, muddy areas) for insect vectors. • Use individual rather than communal feeders and equipment.

• Clean and disinfect feed bunks, waterers, horse trailers and other equipment regularly.

• Be sure that your farrier and other equine professionals who come into direct contact with your animals exercise due care so as not to spread the disease from one horse or facility to the next. • On farms where VS has been confirmed, handle healthy animals first, ill animals last. Handlers should then shower, change clothing and disinfect equipment to prevent exposing others.

Reference

http://njequine.net/brouchures/Vesicular%20Stomatitis.pdf

EQUINE HESPESVIRUS

Equine herpesvirus infections have been highlighted in many news articles since they are very common in horse populations.This results in sporadic outbreaks in equine populations. Therefore, it is good to be familiar with the types of equine herpesviruses, clinical signs associated with the disease, transmission, diagnosis, treatment and especially, ways to protect your horses from infection.

Types of Equine Herpesvirus

• Equine herpesviruses (EHV) are in the family Alphaherpesviridae and are enveloped double stranded DNA viruses.
  
• There are 5 alpha herpesviruses that infect horses (EHV-1, 2, 3, 4, and 5).For the purposes of this fact sheet, we will focus on EHV-1 and EHV-4, which are the two that result in serious clinical disease in the horse.
  
• EHV-1 and EHV-4 used to be considered subtypes of the same virus, but are now recognized as closely related but different viruses.
  
• EHV-1 is commonly found in horse populations worldwide and was previously referred to as the equine abortion virus.Although EHV-1 is well known for causing reproductive disease, it is also known to cause respiratory and neurological disease.
  
• EHV-4 is also known as equine rhinopneumonitis virus and is most common among foals and yearlings. Although EHV-4 most commonly causes respiratory disease, it can also cause abortion and neurological disease.
  

Clinical Signs Associated with Equine Herpesvirus Infection

The incubation period (period of time from exposure to development of first clinical signs) ranges from 2 to 10 days.
Respiratory signs for EHV-1 and EHV-4 include fever of 102 -107º F that lasts for 1-7 days, coughing, depression, inappetence (going off feed), and nasal discharge.Abortion usually occurs between months 7 and 11 of gestation, about 2-12 weeks after infection.
There is no evidence that the mare's reproductive tract is damaged, and it does not affect her ability to conceive in later pregnancies.
Signs of neurologic disease for EHV-1 and EHV-4 include mild incoordination, hindlimb paralysis, recumbency (lying down and being unable to get up), loss of bladder and tail function, and loss of sensation to the skin around the tail and hindlimb areas.

Transmission

Transmission occurs when infected and uninfected horses come in either direct (nose to nose contact) or indirect (through buckets, clothing, blankets that are contaminated) contact with nasal discharges of infected horses.
The virus can travel via aerosol (in the air) for short distances.The virus may also be transmitted by contact with aborted fetuses, placental fluids, or placentas from infected horses.Also, following infection, horses may become latent carriers of EHV; virus may be reactivated after stress or high doses of corticosteroids.
Upon detection of clinical signs suggestive of EHV, the veterinarian may choose to take a nasopharyngeal (nose and throat) swab of the horse, blood sample, or tissue from the aborted fetus for detection of virus in the tissues. Paired blood samples for detection of antibody titers (levels) may also be taken.Treatment involves supportive care and treatment of the symptoms. Non-steroidal anti-inflamatory drugs are commonly used to reduce fever, pain and inflammation.In uncomplicated cases, complete recovery will occur in a few weeks.Horses with neurological disease have variable recovery rates depending on severity of the clinical signs. The prognosis is poor if the horse is recumbent (unable to stand) for an extended period of time. The horse should be rested until fully recovered and gradually returned to work.

Protection

There are two types of vaccines available for use in the horse for prevention of the disease, but their use remains controversial.Vaccination may reduce the severity and duration of disease, but will not totally prevent the disease. Your equine veterinarian should be consulted regarding the most appropriate use of vaccination in your particular circumstance.Since latent infection is still a problem, vaccination must go hand-in hand with the use of best management practices.
There are both modified live virus and killed virus vaccines available.The modified live virus vaccine contains virus that has been altered to make it unlikely to cause disease but is still able to reproduce in the body cells and stimulate immunity.The killed vaccine contains virus that has been inactivated or killed using either heat or chemicals. The modified live vaccine is administered intranasally and offers quicker protection.There is no scientific basis to indicate that the modified live vaccine will cause disease. The killed vaccine is given intramuscularly. Vaccine usage in light of the recent outbreaks of neurological EHV-1 is currently being re-evaluated.Consult your veterinarian for recommendations.



In order to prevent an outbreak, horses arriving on a farm from other locations should be isolated for 3-4 weeks before being introduced into the resident horse population.Reduce management-related stressors that may increase the possibility of stress-induced reactivation of latent EHV-1 in carrier horses. Keep horses separated by physiological state or group, especially with regards to pregnant mares, who should be kept away from weanlings, yearlings, and performance horses that frequently travel.



In the case of an outbreak, infected horses should be isolated from other horses.The stable should be quarantined for at least three weeks after signs of clinical disease in the last case subside. All stable equipment should be disinfected. People handling the infected horses should be sure to wash their hands after handling each horse, dip their shoes in a disinfecting foot bath, and change clothes before working with healthy horses. Some sources suggest that bedding be removed and burned. Barn stalls, aisles and other surfaces should be cleaned and disinfected as well.Although this virus can last for several weeks in the environment, it is readily killed by most common disinfectants; phenol based disinfectants are commonly used.



Equine herpesvirus infection can become a serious problem.Being aware of the types of equine herpesvirus, clinical signs associated with the disease, transmission, diagnosis, treatment and especially, ways to protect your horses from infection, will aid you if there is an outbreak in your area. Incorporating measures to protect your horse now may prevent problems in the future.



Sources:
1.Merck & Co. Inc.Merck Veterinary Manual. 2006. www.merckvetmanual.com
2.Powell, DG. Equine rhinopneumonitis. Horse Industry Handbook, 1993, 610-1-5.
3.McClogan, Carrie.A case scenario: equine respiratory disease. Department of Pathology, University of Georgia.Available at www.vet.uga.edu/vpp/IVM/ENG/ERD/EHV-4and1.html
4. Personal communication, Dr. Sanchez, Tufts University School of Veterinary Medicine.

EQUINE INFECTIOUS ANAEMIA

Equine infectious anemia is an incurable and infectious, often fatal disease.

Horses, ponies, donkeys, asses and other equine family members are vulnerable to infection by the disease-causing virus.

Also known as EIA, other common names for the disease include swamp fever, mountain fever or malarial fever.

An estimated 30 percent to 50 percent of infected animals die within two weeks to four weeks after the onset of clinical signs of EIA.

Transmission

EIA is spread through blood-to blood contact, not close proximity.

The virus can be transmitted from an infected animal to “clean” equine by unsterilized or contaminated needles, blood transfusions, medical instruments or biting fl ies.

Studies show as few as three horsefl ies can carry enough virus between animals to cause infection.

EIA has no known cure or vaccine.

Infected horses produce antibodies, which cannot rid the body of the disease.

The virus can hide and “drift” into various forms, making complete recovery impossibleand hampering efforts to create a vaccine.

The Coggins’ and CELISA test methods detect EIA virus antibodies in the bloodstream.

Symptoms

EIA can strike in three forms, depending on an animal’s resistance, strength of the virus, and stress factors like weather or physical exertion.

Acute responses generally occur 7 days to 30 days after initial exposure. Horses may develop fever, go off feed, or die suddenly.

Eventually, the virus destroys red blood cells, causing severe anemia.

Equine in the acute stage may test negative for 16 days to 42 days after exposure, until the animal’s immune system has had time to produce detectable antibodies.

Chronic infections produce positive tests and classic symptoms: weight loss, weakness, anemia, and swelling of the lower legs, chest and abdomen.

Symptoms subside, but may reoccur. Acute episodes can emerge after stress from hard work, hot weather, pregnancy or other disease.

Identification of Positives

Owners have three options for handling positive animals:

• Permanently quarantine the animal strictly to the owner’s premises at least 200 yards from the nearest equine (including those under the same ownership).
• Euthanasia (at the owner’s expense) after notification of the State Veterinarian.
• Slaughter, after securing a special permit from the State Veterinarian. All other equine in the herd must also be tested for EIA.

Control

Many countries have control programs requiring equids to be tested for equine infectious anemia.

State regulations in the U.S. vary, but most states require one or more tests, particularly before entry of the horse into the state, participation in organized activities and/or sale of the horse.

Regular voluntary testing of the equids on a farm, as well as testing of new animals before introduction, is helpful in maintaining an EIA-free herd. No vaccine is available.

Infected equids become lifelong carriers, and must be permanently isolated from other susceptible animals or euthanized.

In the U.S., a reactor must be marked with a brand, freezemarking or a lip tattoo before it is moved between states.

Reactors can only be transported between states if they are going to their home farms, a slaughterhouse, or a diagnostic or research facility, and they must move under quarantine conditions.

Asymptomatic carriers often give birth to uninfected foals.

The risk of congenital infection is higher if the mare has clinical signs before she gives birth. Foals born to infected mares should be isolated from

References

http://www.in.gov/boah/files/EIA65.pdf

http://www.cfsph.iastate.edu/Factsheets/pdfs/equine_infectious_anemia.pdf

AFRICAN HORSE SICKNESS

AETIOLOGY

Classification of the causative agent African horse sickness (AHS) is caused by a virus of the family Reoviridae of the genus Orbivirus.

EPIDEMIOLOGY

Infectious disease is transmitted by Culicoides spp. that occurs regularly in most countries of subSaharan Africa

At least two field vectors are involved: Culicoides imicola and C. bolitinos

The disease has both a seasonal (late summer/autumn) and an epizootic cyclical incidence, with disease associated with drought followed by heavy rain

Usual hosts are equids: horses, mules, donkeys and zebra

Reservoir host are believed to be zebras

Clinical diagnosis

There are four principal manifestations of disease

In the majority of cases, the subclinical cardiac form is suddenly followed by marked dyspnoea 

Fever (40–40.5°C/104°F–105°F)

Mild form; general malaise for 1–2 days

Subacute or cardiac form

Fever (39–41°C/102–106°F)

Swelling of the supraorbital fossa, eyelids, facial tissues, neck, thorax, brisket and shoulders

Mortality usually 50% or higher; death usually within 1 week Acute respiratory or

pulmonary form

Fever (40–41°C/104–106°F)

Dyspnoea, spasmodic coughing, dilated nostrils with frothy fluid oozing out

Redness of conjunctivae

Mixed form (cardiac and pulmonary)

Occurs frequently

Pulmonary signs of a mild nature that do not progress, oedematous swellings and effusions

Mortality: about 70–80% or greater Lesions

Respiratory form: interlobular oedema of the lungs o hydropericardium, pleural effusion oedema of thoracic lymph nodes petechial haemorrhages in pericardium mucosa and serosa of small and large intestines may exhibit hyperaemia and petechial haemorrhages

Cardiac form: o subcutaneous and intramuscular gelatinous oedema epicardial and endocardial ecchymoses; myocarditis o hemorrhagic gastritis

PREVENTION AND CONTROL

• No efficient treatment available Sanitary prophylaxis Free areas, regions and countries  Identify the virus and serotype
• Establish strict quarantine zone and movement controls
• Consider euthanasia of infected and exposed equids
• Stable all equids in insect-proof housing, at a minimum from dusk to dawn when Culicoides are most active
• Establish vector control measures: destroy Culicoides breeding areas; use insect repellents, insecticides, and/or larvicides
• Monitor for fever at least twice daily: place pyrexic equids in insect-free stables or euthanize
• Consider vaccination o identify vaccinated animals o available vaccines are attenuated produce viraemia, and may theoretically reassort with the outbreak virus may be teratogenic Affected areas, regions and countries
• Annual vaccination
• Vector control

References

http://www.oie.int/fileadmin/Home/eng/Animal_Health_in_the_World/docs/pdf/Disease_cards/AFRICAN_HORSE_SICKNESS.pdf

EQUINE RABIES

Rabies is an acute viral infection of the nervous system that mainly affects carnivores and bats, although it can affect any mammal.

It is caused by the rabies virus. Once signs appear, it is fatal. 
Transmission is almost always by the bite of an infected animal, when the saliva containing the rabies virus is introduced into the body. In horses, the virus can be in the body for 2 to 9 weeks before signs develop.

The signs 

There are 2 major forms of the disease.

The furious form of rabies is the classic “mad-dog” syndrome; it is not common in horses. The animal becomes irritable and may become vicious or aggressive without provocation. The posture is alert and anxious, with pupils dilated. As the disease progresses, seizures and lack of muscle coordination are common. Death is caused by paralysis that worsens over time.

The paralytic form of rabies usually involves paralysis of the throat and jaw muscles, often with excess salivation and inability to swallow. Drooping of the lower jaw is common. People can be infected by this form when examining the horse's mouth or giving it medication with bare hands. Paralysis progresses throughout the body and death occurs within a few hours.

Diagnosis is difficult, especially in areas where rabies is not common. Early stages of rabies can be easily confused with other diseases or with normal aggressive tendencies.
A rabies diagnosis must be verified with laboratory tests. The animal must be euthanized and the remains sent for laboratory analysis. There is no effective treatment.

Guidelines for the control of rabies are updated yearly. In general, any animal that has bitten a person and has signs of rabies should be euthanized. An unvaccinated horse that has been bitten by or exposed to a rabid animal must be either euthanized or quarantined for 6 months and vaccinated for rabies 1 month before release. A vaccinated horse that is bitten by or exposed to a rabid animal should be given a rabies booster and observed for 45 days for any signs of rabies.

Several rabies vaccines are available for horses; these appear to be both safe and effective in preventing rabies. Your veterinarian can recommend an appropriate vaccine and booster schedule based on current guidelines.

Risk of Passing Rabies to People

When a person is exposed to an animal suspected of rabies, the risk of rabies transmission should be evaluated carefully. Wild carnivores and bats present a considerable risk where the disease is found, regardless of whether or not abnormal behavior has been seen.

Any healthy domestic animal, whether vaccinated or not, that bites a person or otherwise deposits saliva into a fresh wound, should be confined for 10 days for observation. If the animal develops signs within those 10 days, it should be promptly euthanized and submitted for testing.

Pre-exposure vaccination is strongly recommended for all people in high-risk groups, such as veterinary staff, animal control officers, rabies and diagnostic laboratory workers, and travelers working in countries where rabies is prevalent.

Reference

The Mercks Veterinary Manual

EQUINE INFLUENZA

Equine Influenza (EI) is a highly contagious though rarely fatal respiratory disease of horses, donkeys and mules and other equidae.
The disease has been recorded throughout history, and when horses were the main draft animals, outbreaks of EI crippled the economy.
Nowadays outbreaks still have a severe impact on the horse industry.
EI is caused by two subtypes of infl uenza A viruses: H7N7 and H3N8, of the family Orthomyxoviridae.
They are related to but distinct from the viruses that cause human and avian infl uenza. Equine Infl uenza is a disease listed in the OIE Terrestrial Animal Health Code and countries are obligated to report the occurrence of the disease according to the OIE Code.
The disease is entrenched in most of the world, with the exceptions of Australia (where an important outbreak occurred in 2007), New Zealand, and Iceland.


How is the disease transmitted and spread?

Highly contagious, EI is spread by contact with infected animals, which in coughing excrete the virus.
In fact animals can begin to excrete the virus as they develop a fever before showing clinical signs.
It can also be spread by mechanical transmission of the virus on clothing, equipment, brushes etc carried by people working with horses.
Once introduced into an area with a susceptible population, the disease, with an incubation period of only one to three days, spreads quickly and is capable of causing explosive outbreaks.
Crowding and transportation are factors that favour the spread of EI.

Clinical signs

In fully susceptible animals, clinical signs include fever and a harsh dry cough followed by a nasal discharge. Depression, loss of appetite, muscle pain and weakness are frequently observed. The clinical signs generally abate within a few days, but complications due to secondary infections are common. While most animals recover in two weeks, the cough may continue longer and it may take as much as six months for some horses to regain their full ability. If animals are not rested adequately, the clinical course is prolonged.

Prevention

Vaccination is practiced in most countries. However, due to the variability of the strains of virus in circulation, and the diffi culty in matching the vaccine strain to the strains of virus in circulation, vaccination does not always prevent infection although it can reduce the severity of the disease and speed recovery times.
 The OIE also convenes an Expert Surveillance Panel on Equine Infl uenza Vaccine that examines the strains of virus in circulation making recommendations on which strains should be included in the vaccines. 

Reference

http://www.oie.int/doc/ged/D14001.PDF