Zoonotic Diseases

 

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Definition/Description

A zoonotic disease is any disease or infection that is naturally transmissible from vertebrate animals to humans. 

Classes of Zoonoses

1. Viral Zoonoses

     Most Common Viral Zoonoses

     Ehrlichiosis

the general name used to describe several bacterial diseases that affect animals and humans. Human ehrlichiosis is a disease caused by at least three different ehrlichial species in the United States: Ehrlichia chaffeensis, Ehrlichia ewingii, and a third Ehrlichia species provisionally called Ehrlichia muris-like (EML). Ehrlichiae are transmitted to humans by the bite of an infected tick. Symptoms usually occur within 1-2 weeks following a tick bite and include fever, headache, fatigue, and muscle aches. Ehrlichios is is diagnosed based on symptoms, clinical presentation, and later confirmed with specialized laboratory tests. Treatment for adults and children of all ages is doxycycline.

     Rickettsia (Rocky Mountain Spotted Fever)

A disease caused by the bacterium Rickettsia rickettsii, which is carried by ticks. People usually start having fevers and feeling nauseous about a week after being bitten by a tick. A few days after the fever begins people will often have a rash, usually on the arms or ankles. They also may have pain in their joints, stomach pain, and diarrhea. People get this disease when they are bitten by a tick that is carrying the bacterium R. rickettsia. Because ticks on dogs can be infected with R. rickettsii, dogs and people can get Rocky Mountain spotted fever from the same ticks. These ticks can also bite other animals and pass Rocky Mountain spotted fever to them. When you remove ticks from any animal, the crushed tick or its parts can also pass this disease through any cuts or scrapes on your skin.

     Rabies

A viral disease associated with mammals, including dogs, cats, horses, and wildlife. Rabies can be transmitted through bites, scratches, aerosolized respiratory secretions, and saliva. It may take several weeks or even a few years for people to show symptoms after getting infected with rabies, but usually people start to show signs of the disease 1 to 3 months after the virus infects them. The early signs of rabies can be fever or headache, but this changes quickly to nervous system signs, such as confusion, sleepiness, or agitation. Once someone with rabies infection starts having these symptoms, that person usually does not survive. For this reason, all animal health care workers should be vaccinated against rabies and should have their titers checked every other year. Many kinds of animal can pass rabies to people. Wild animals are much more likely to carry rabies, especially raccoons, skunks, bats, foxes, and coyotes. However, dogs, cats, cattle, or any warm-blooded animal can pass rabies to people.

     West Nile Virus

A viral disease spread by mosquitoes which can affect birds, horses, and other mammals Mosquitoes become infected when they feed on infected birds. Infected mosquitoes can then spread WNV to humans and other animals when they bite. About one in 150 people infected with WNV will develop severe illness. The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent. Up to 20 percent of the people who become infected have symptoms such as fever, headache, and body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. Symptoms can last for as short as a few days, though even healthy people have become sick for several weeks. Approximately 80 percent of people (about 4 out of 5) who are infected with WNV will not show any symptoms at all. People typically develop symptoms between 3 and 14 days after they are bitten by the infected mosquito. There is no specific treatment for WNV infection. In cases with milder symptoms, symptoms pass on their own. In more severe cases, people usually need to go to the hospital where they can receive supportive treatment including intravenous fluids, help with breathing, and nursing care. Personal protective measures are the primary way to avoid contracting the virus.

     Equine Encephalitis

A mosquito borne infection normally maintained in nature by a cycle from an arthropod vector to a vertebrate reservoir host. Although some people experience it only as a mild illness, eastern equine encephalitis is fatal in about one-third of the cases. Symptoms of eastern equine encephalitis usually appear three to 10 days after a bite by an infected mosquito. A vaccine exists for horses but not for humans. Personal protective measures are the primary way to avoid contracting the virus.

     Diagnostic Tests/Lab Tests/Lab Values          

1. ELISA (Enzyme Lined Immuno-Sorbent Assay)- detects the actual disease. May not be sensitive enough to detect infection in the asymptomatic carrier.

2. PCR (Polymerase Chain Reaction)- amplifies minute quantites of microbial DNA or RNA allowing for recognition of latent phases of viral diseases. May yield false positive result for the disease but give a true positive for infection within the agent.

3. Serology (Indirect Fluorescent Antibody Testing)- used to detect Reckettsial organisms which cause Ehrlichiosis and Rickettsia

2. Bacterial Zoonoses

     Most Common Bacterial Zoonoses

     Brucellosis

a zoonotic infection transmitted from animals to humans by the ingestion of infected food products, direct contact with an infected animal or inhalation of aerosols. The timely and accurate diagnosis of human brucellosis continues to challenge clinicians because of its non-specific clinical features, slow growth rate in the blood culture, and the complexity of its serodiagnosis. Brucellosis in human beings is rarely fatal, but can lead to severe debilitation and disability Diagnostic methods for brucellosis are primarily based on serology, with the LPS smooth chains producing the greatest immunological responses in various hosts.

     Diagnostic Tests/Lab Tests/Lab Values

o Blood culture is the gold standard in the diagnosis of bacterial infections including brucellosis

Recent Related Research (from Pubmed)

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== Recent Related Research (from Pubmed)

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References

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