What is Orf Viral Infection?
Orf viral infection, also known as contagious pustular dermatitis or ecthyma contagiosum, is a disease people can get from infected sheep and goats. It’s caused by a type of virus called parapoxvirus Orfviridae. This virus primarily affects young sheep and goats and causes blister-like, bump-like, and lump-like sores, particularly around the mouth area of the animals, which may look like mouth sores. However, in people, the sores usually appear on the back of the hands or fingers, where they have contact with the infected animals. This virus is known for being able to transfer from animals to humans after being in touch with an infected animal or things that the infected animal touched.
The disease goes through 6 stages and can usually be diagnosed based on a history of handling sheep, goats, or other related animals. Tests such as a skin biopsy or a polymerase chain reaction test (a test that can detect genetic material from specific organisms, like a virus) can help diagnose suspicious sores when there’s no clear history or when the symptoms are unclear. More tests could be needed when considering other causes of bumps on hands. Under a microscope, this virus looks similar to other viruses showing particular cell changes. Treatment may not be needed for patients with healthy immune systems, as the disease usually gets better by itself in 6 to 8 weeks. However, for patients with weakened immune systems, several treatments can be used to prevent the disease from getting worse.
What Causes Orf Viral Infection?
The orf virus is a type of virus that specifically targets skin cells and is commonly found in animals like sheep and goats. It’s picked up through a process called isothermal amplification, which essentially means it multiplies at a constant temperature. This virus belongs to the parapoxvirus family and is made up of linear, double-stranded DNA. A unique feature of this virus is that it can reinfect its hosts, particularly sheep and goats, quite frequently.
The orf virus is known to have several factors that impact its severity and ability to affect the immune system. These factors include things like a granulocyte/macrophage colony-stimulating inhibitor factor, which is a substance that can inhibit or stimulate the production of certain cells; nuclear factor-kappa beta inhibitors, which control the activity of some proteins; vascular endothelial growth factor-E, which aids in the creation of new blood vessels; a chemokine binding protein, which works in the immune response; and a viral version of interleukin-10, a protein that regulates our immune system.
Recent research findings suggest that the orf virus employs a process called macroautophagy in mammals. This is a mechanism cells use to get rid of damaged components, and it contributes to the virus infecting and causing disease in human hosts. The orf virus not only affects the immune system but also has antiviral activity. For instance, it shows activity against fibrosis (tissue thickening and scarring), as observed in liver samples from rats infected with hepatitis B and C viruses.
Risk Factors and Frequency for Orf Viral Infection
The Orf virus is commonly found in animals, especially in sheep and goats, but it can also be seen in muskoxen and camels. Various studies have been conducted to comprehend the prevalence of Orf virus in animals. In fact, one study in Nigeria found that nearly 70% of animals had the virus over a two-year period. The death rate in livestock due to the Orf virus can vary between 0% and 8%. The various types of Orf viruses in animals have also been identified using advanced scientific techniques.
Even though the Orf virus is not common all around the world, it is more likely to be found in certain populations. A study in France counted 44 infections over three years, mainly in people who have been in contact with sheep. People who have jobs that expose them to animals, such as farmers, veterinarians, slaughterhouse employees, sheepherders, and butchers, have a higher risk of getting infected by the Orf virus. However, even people who come in contact with sheep or goats during religious or other rituals, or who get minor injuries while handling these animals, could get infected with the Orf virus.
Signs and Symptoms of Orf Viral Infection
People exposed to certain occupational risks, such as sheep and goat handlers, farmers, butchers, and religious leaders handling sheep or goats, are more prone to catching the orf virus. The virus can also be contracted through animal contact while traveling. Symptoms of the orf virus include distinct, changeable, painless skin lesions, which are usually diagnosed clinically. More often, these lesions appear on the hands and fingers (>90% of cases), but they’ve also been found on the face, scalp, and even the genital areas. In individuals with weakened immune systems, the lesion can grow large(giant orf) and cause health problems.
After around a week in the body, the orf lesions go through six stages of development. Each stage lasts about a week and develops as follows:
- Maculopapular stage: Red patches and bumps appear.
- Target stage: Ring-like lumps form with a red outline and a rotting center.
- Acute stage: These lumps begin to leak fluid.
- Regenerative stage: The lump dries out.
- Papilloma stage: A dry crust forms on the lump, which becomes wart-like.
- Regression stage: The lump starts to shrink.
On occasion, these lesions can come with additional symptoms, including swollen lymph nodes, fever, discomfort, or skin conditions similar to erythema multiforme or bullous pemphigoid.
Testing for Orf Viral Infection
If your doctor suspects you might have an Orf virus infection, they’ll typically make a diagnosis based on your exposure history and symptoms. That being said, the most reliable way to diagnose this virus is with a skin biopsy, usually done by a small shave or punch technique. This procedure is considered the gold standard for confirming an Orf virus infection.
Besides, if the biopsy might not be available or the condition’s signs are unclear, doctors might use a specific lab test called a PCR assay. This test can detect the presence of Orf virus accurately and is very sensitive to this virus. It can really help if the doctor needs to make sure about the diagnosis.
Other diagnostic methods used to detect an Orf virus infection may include cell cultures, electron microscopy (a type of microscope that uses an electron beam to create an image), virus neutralization (a technique to find out if there’s a virus present), immunohistochemistry (a process to visualize proteins in cells of a tissue), immunofluorescence (a method to find specific cells or molecules), an enzyme-linked immunosorbent assay (a test to detect and measure antibodies in the blood), loop-mediated isothermal amplification, and recombinase polymerase amplification (both are rapid DNA testing methods).
Treatment Options for Orf Viral Infection
Orf viral infection is a disease that can be transmitted from animals to humans, usually resulting in a good prognosis. The symptoms, which manifest as skin lesions, tend to clear up on their own within 4 to 6 weeks for patients with a healthy immune system. For these patients, assurances and simply waiting for symptoms to improve is often all that’s required. However, in patients with a compromised immune system, such as those with certain chronic illnesses or on medications that weaken the immune system, Orf can cause larger lesions that can resemble tumors or pyogenic granulomas (non-cancerous skin growths), requiring further medical intervention. It’s advised to avoid surgical removal of the lesions, as it can delay healing.
A common treatment involves the use of a topical antiviral medication called cidofovir. This medication works by blocking a specific enzyme in the virus, helping to halt its spread. Sometimes, additional methods such as cryotherapy (the use of extreme cold to destroy abnormal or diseased tissue) or imiquimod (a cream that helps the immune system fight the virus) may be necessary.
In those with weakened immune systems, a form of treatment with a protein called interferon-alpha is sometimes used, along with other antiviral medicines that inhibit a component of the virus called nucleoside. Vaccinations have also proven effective, particularly due to the consistency of the virus structure, and are regularly given to domesticated sheep and goat populations. It’s quite rare for humans to experience a second Orf infection, but if it does occur, the symptoms are generally milder.
Researchers are continually exploring other potential treatments for the Orf virus, and other similar poxviruses. Brincidofovir, for instance, has demonstrated effectiveness against Orf and other related viruses in lab studies and animal testing. Similarly, cidofovir has shown effectiveness against various types of poxviruses and has even demonstrated its ability to lessen the growth of Orf lesions in animal models. This medicine is typically employed in more stubborn cases, especially for patients with a weakened immune system.
What else can Orf Viral Infection be?
When diagnosing certain diseases, doctors often check for conditions that might share similar symptoms or common factors such as exposure to farm animals and the appearance of skin lesions. Two important conditions to rule out are Paravaccinia, also known as Milker’s nodules, and Cutaneous anthrax.
Paravaccinia, or Milker’s nodules, is a condition caused by infection from cows, unlike orf, which is caused by goats or sheep. The symptoms of orf and Milker’s nodules look very similar and often heal on their own within six weeks.
Cutaneous anthrax is a bacterial infection caused by the bacterium ‘Bacillus anthracis’. The classic symptom is the formation of a “black scab” on the skin. Anthrax can also develop severe lung symptoms if it spreads throughout the body, which can be life-threatening. You can catch Anthrax from infected animals, their wool, and even their meat. Doctors use different tests including gram staining, culturing the bacteria, and PCR to diagnose the disease.
Doctors also consider other conditions that could be mistaken for these diseases, including:
- Deep fungal infection
- Squamous cell carcinoma (especially the keratoacanthoma type)
- Pyogenic granuloma
- Atypical mycobacterial infection
- Neutrophilic dermatoses
What to expect with Orf Viral Infection
Orf viral infection is a type of infection that is transferred to humans from animals. Typically, this infection isn’t too severe and often clears up on its own within 6 to 12 weeks. It also does not spread easily from person to person. However, in people who have a weakened immune system, especially those whose cellular defense mechanisms are compromised, the infection can become more serious and large (a condition known as “giant orf”).
While it’s possible for the infection to come back, any recurring infections tend to be milder each time.
Possible Complications When Diagnosed with Orf Viral Infection
Secondary bacterial infections may follow an Orf infection. Other associated problems can encompass lymphangitis (inflammation of the lymph vessels), lymphadenopathy (disease in the lymph nodes), and erysipelas (a skin infection).
There can be occasional immune system reactions associated with zoonotic (disease passed from animals to humans) infections, particularly from an immunomodulatory virus like Orf. Patients can potentially develop Erythema multiforme, Stevens-Johnson syndrome, and bullous pemphigoid, all of which are serious health conditions. In a study of five patients with blistering ailments, scientists found IgG1 and IgG3 autoantibodies targeting laminin-332. Laminin-332 is usually found in mucous membrane pemphigoid, a chronic blistering skin disorder. Care should be taken with patients exhibiting blistering conditions as Orf-related pemphigoid might be a unique clinical scenario.
Potential Consequences of Orf Infection:
- Secondary bacterial infections
- Lymphangitis
- Lymphadenopathy
- Erysipelas
- Erythema multiforme
- Stevens-Johnson syndrome
- Bullous pemphigoid
- Potential unique orf-related pemphigoid
Preventing Orf Viral Infection
It’s crucial to teach farmers, herders, and others who work closely with animals the right way to wear gloves and wash their hands. This can help prevent diseases from spreading. Workshops or other learning resources that help individuals spot and diagnose sick livestock are really valuable. Additionally, these resources can cover the right way to give vaccinations or introduce herd immunity, which is when enough of a population is immune to a disease to protect those who aren’t. Both of these methods are effective ways to stop the infection from spreading.
