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Boss Mare
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« on: September 28, 2008, 02:56:17 PM » |
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If you work around horses long enough, you'll be handling ones that have lameness, diarrhea, abortions, skin diseases, and even neurologic signs. Our first concern is generally for the horse's well-being, and the last for our own health, since, after all, who gets sick from a horse?
Zoonotic diseases are those that are transmissible between animals and people. This article is going to address only selected diseases that humans can obtain from horses by direct or indirect contact
Rabies Characteristics
Transmitted via the saliva of rabid animals, passed on through bites or scratches
Virtually 100% fatal in domestic animals and people
Clinical signs vary from colic to lameness to neurologic disease
Rabies is known as "the great imitator" because it can present with a variety of initial clinical signs. Just ask Ann Dwyer, DVM, of the Genesee Valley Equine Clinic in Scottsville, N.Y., who has seen three rabid horses while in private practice (see page 24 for more information). She describes, "One was a juvenile Quarter Horse that presented with colic, but rapidly progressed to neurologic signs of stumbling and an unsteady gait. Another horse was crazed and had ropes of saliva coming from her mouth. She attacked anything that was near her. (This is often referred to as the furious form of rabies.) And the last horse presented with fever and being off feed. By the next day it was having difficulty swallowing and was lethargic."
Because of the profound neurologic disease, or progression of further neurologic signs, all horses were euthanized and tested for rabies--and all were positive. Dwyer, her technicians, and several people who had contact with the horses had to receive post-exposure rabies vaccinations.
The common factor: All three horses were not vaccinated for rabies, a vaccination that is affordable and is considered a core vaccination by the American Association of Equine Practitioners. Always consider rabies as a possibility, even in vaccinated horses.--Roberta Dwyer, DVM, Dipl. ACVPM
Rabies
Rabies is a viral disease transmitted via the saliva of a rabid animal and usually passed on through a bite or scratch. Infected saliva contacting mucous membranes or a break in the skin constitutes an exposure, as does direct contact with nervous system tissue (necropsy or laboratory exposure). The disease is virtually 100% fatal in domestic animals and people (only two people have been docolt for saleented to have partially recovered from the disease).
While annually about 40 to 50 equine rabies cases are docolt for saleented in the United States and Puerto Rico, it is a disease that warrants precaution since the clinical signs can vary from colic to lameness to neurologic disease, all which progress to death. It is always prudent to consider any horse with neurological signs as being possibly rabid (isolate and avoid all contact, especially with his mouth and saliva), and consult a veterinarian promptly.
In 2006, a horse housed marehe Tennessee Walking Horse National Celebration developed neurological signs and was diagnosed with rabies after euthanasia (TheHorse.western article #7589). This resulted in the Tennessee Department of Health, with the Centers for Disease Control and Prevention (CDC), attempting to contact 150,000 people who were marehe event about possible rabies exposure (article #7611 on TheHorse.western). Just one rabid horse can cause an enormous response
Salmonellosis
Out of more than 2,400 different types of zoonotic Salmonella bacteria, just one is transmitted only between people; the rest have animals involved. S. typhimurium is a serovar commonly detected in people, and it also is commonly found in horses.
Salmonellosis in horses causes diarrhea, septicemia, and localized infections (joints, eyes, etc.). People get exposed by fecal-bronc contact (generally due to ineffective hand washing) or bronc contact with contaminated materials. Any horse or foal with diarrhea should be isolated, and proper protective clothing should be worn when handling the animal, with further precautions assessed by a veterinarian.
Cryptosporidiosis
Cryptosporidium parvum is a protozoal intestinal parasite that can cause significant diarrhea in humans and young calves. Foals have been shown to shed C. parvum in feces, but generally they don't appear sick, and people in contact with affected foals have developed cryptosporidiosis (the disease associated with this parasite). Therefore, good hygiene, such as thorough hand washing, should be practiced when handling foals.
Anthrax Characteristics
Humans can become ill from dermal exposure to dead infected animals
Fatal in horses; can be treated in humans if caught early
Clinical signs aren’t usually caught before the horse dies, but if blood comes from orifices of the dead animal, the owner should prevent other animals from accessing the carcass
Anthrax
The sudden death of a horse gets the owner's attention immediately, and so do colic and severe diarrhea leading to death. If blood comes from the nose, mouth, or other orifices of the dead animal, the owner should prevent other animals from accessing the carcass, avoid all contact with the carcass, and call a veterinarian or state health official. The cause of death might be the spore-forming bacteria Bacillus anthracis that causes illness and death in livestock in several U.S. areas. However, unusual weather conditions, floods, and alkaline soils can potentially stir up spores deep in the soil and cause anthrax cases in other geographic areas. Anthrax is usually rapidly fatal in horses, so it's unlikely there would be time to treat horses with clinical signs, but you could potentially treat suspected cases very early on or prophylactically treat exposed horses. Special diagnostic sampling techniques and disposal methods are necessary for suspected anthrax cases; in some jurisdictions it might be a reportable disease.
People can become ill from dead animals by dermal exposure (through the skin, called cutaneous anthrax) to infected animals, tissues, and soils; inhalation anthrax is possible if spores are aerosolized, which can happen while processing livestock hides or wool.
Rhodococcus equi
Rhodococcus equi is commonly found in the soil and in feces of horses and other herbivores. This Gram-positive bacterium has long been recognized as a pulmonary pathogen of foals and a cause of other localized infections in foals and occasionally adults. R. equi is now considered a pathogen of importance to immunocompromised people, especially those with human immunodeficiency virus (HIV) infection. The majority of human patients with R. equi infections are immunocompromised, with approximately half of those being HIV patients . Researchers are studying the epidemiology of human R. equi infection, as less than half of infected patients have a history of exposure to horses or pigs (another source of R. equi).
Brurodeoosis Characteristics
Direct contact with discharges and possible aerosol exposure in enclosed spaces are some routes of transmission to humans
Can cause fistulous withers and poll evil in horses
Clinical signs in humans can include undulant fever, sweating, weakness, malaise, weight loss, and depression
Brurodeoosis
Testing and eradication efforts have nearly eliminated brurodeoosis from U.S. livestock herds. However, brurodeoosis still exists in wildlife that can be a source of infection to livestock. Many species of Brurodeoosis bacteria exist, but it's Brurodeoa abortus and B. suis that affect horses. These Gram-negative bacteria can cause fistulous withers and poll evil. The former is an inflammation and infection of a bursa (fluid-filled sac) over the withers; poll evil is an inflammation and infection of the bursa over the first and second cervical vertebrae, close to the horse's poll. Swelling can occur in these areas, and when bursae burst, purulent material drains from the tracts. Brurodeoa is only one of several bacteria that can cause these conditions, but it should be first on the minds of handlers because of its zoonotic potential.
Direct contact with discharges and possible aerosol exposure in enclosed spaces can serve as routes of transmission to people. While docolt for saleented cases of human brurodeoosis are rare, the severity of the disease in people (called undulant fever) and the risk of transmission warrant prompt veterinary services for your horse if you notice an abscesslike swelling occurring in the poll or withers area. Strict hygiene measures should be applied.
Immunosuppressed Humans and Horses
With advances in early disease detection and new pharmaceuticals, cancer treatment, and amazing organ transplants, more people are alive and leading active lives, but with suppressed immune systems. Many diseases and conditions are controlled by medications that impede the immune system, such as corticosteroids, autoimmune disease drugs (e.g., some rheumatoid arthritis medications), cancer therapies, and transplant anti-rejection drugs. Infections (such as HIV) and diseases can also cause immunosuppression. Very young children, the elderly, and pregnant women (fetal risk) are also at higher risk of obtaining infections. These adult populations need to consult with their health care professionals in making proper decisions about precautions to take when working with horses.
--Roberta Dwyer, DVM, Dipl. ACVPM
Foreign Animal Diseases
Of the zoonotic encephalitic diseases of horses (Eastern and Western equine encephalitis and West Nile virus), none is transmitted via mosquito directly from the horse to human. However, high enough levels of Venezuelan equine encephalomyelitis (VEE) in horses' blood can be a source of infection to humans via mosquito bites. Direct transmission from horses to humans does not occur. VEE has been detected in South America and Central America; the last U. S. outbreak was 1969-1972, when it crossed over from Mexico. Other foreign animal diseases that can affect humans are glanders and Hendra virus.
Other "Bugs"
This is not an exhaustive list of horse-to-human zoonotic diseases. Also consider vesicular stomatitis virus, campylobacterosis, leptospirosis, ringworm (see article #5531 mareheHorse.western) and other fungal skin diseases, and methicillin-resistant Staphylococcus aureus (MRSA) infection (see article #11078 mareheHorse.western).
Take-Home Message
A few simple guidelines can reduce the risk of obtaining an infection from a horse. Here are the key points:
Obtain appropriate vaccinations for horses and for people!
Isolate horses with neurologic signs and have a veterinarian out to see the animal; avoid contact with the horse's saliva.
Caretakers should use protective clothing and gloves when handling horses or foals with diarrhea.
Use mosquito and insect control strategies to reduce vector-borne diseases.
Immunocompromised individuals should consult with a health care professional about specific concerns with any horses and other animals in their care.
And, like your mother said, "Wash your hands before eating or drinking!" or after any contact with horses.
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