Arboviruses (2)

ARBOVIRUSES: viruses spread by ANTHROPOD VECTORS JAMES FELIX GALES

Arbovirus • is a shortened name given to viruses that are transmitted by arthropods, or arthropod-borne viruses • Some Arboviruses are able to cause emergent disease. Arthropods are able to transmit the virus upon biting allowing the virus to enter the bloodstream which can cause viraemia.

Arthropod • is an invertebrate that has an exoskeleton (external skeleton), a segmented body, and jointed attachments called appendages. Arthropods are animals belonging to the Phylum Arthropoda (from Greek arthron, "joint", and podos "foot", which together mean "jointed feet"), and include the insects, arachnids, crustaceans, and others.

Viremia • is a medical condition where viruses enter the bloodstream and hence have access to the rest of the body. It is similar to bacteremia, a condition where bacteria enter the bloodstream

Major ARBOVIRUSES • • • •

Togavirus (Alphavirus) Flaviviruses (Flavivirus) Bunyaviruses (Bunyavirus and Phlebovirus) Reonivius (orbivirus)

Chief VECTORS • MOSQUITOS • TICKS • FLIES • GNATS

Epidemiology of Arbovirus Disease • Anthropods are found WORLDWIDE so as the ARBOVIRUSES they carry.

• The vectors and viruses tend to be cluster in trpics abd subtropics but many temperate zones report periodic edemics.

The influence of vectors •

The carriers of arbovirus are the anthropds themselves FACTORS THAT WEIGHS HEAVILY FOR RAMPANT SPREAD OF ARBOVIRUS: 1. Anthropds lifespan 2. Availablity of food and breeding sites 3. Climatic influences

• Most anthropod vectors feed on blood host • Humans can serve s the dead end and accidental hosts or they can be a maintenace reservior • Risk for arboviral infections are great in wilderness areas where encounters with anthropod vectors are frequent

General Charcteristics of ARBOVIRUS infections FEBRILE ILLNESS One ytpe of disease elicited by arboviruses is an acute, undifferentail fever, often accompanied by rush. Example: DENGUE FEVER COLORADO TICK FEVER

Prominent symptoms: • • • • • • •

Fever Prostration Headache Myalgia Orbital pain Muscle aches Joint stiffness

And later through the illness, a maculopapular r petechial rash can erupt over the trunk and limbs.

General Charcteristics of ARBOVIRUS infections ENCEPHALITIS Encephalitis is an acute inflammation of the brain. • Encephalitis with meningitis is known as meningoencephalitis.

Symptoms Patients with encephalitis suffer from fever, headache and photophobia with weakness and seizures also common. Less commonly, stiffness of the neck can occur with rare cases of patients also suffering from stiffness of the limbs, slowness in movement and clumsiness depending on which specific part of the brain is involved. The symptoms of encephalitis are caused by the brain's defense mechanisms activating to get rid of the infection. Other symptoms can include drowsiness and coughing.

Most common type American types are: • eastern equine • St. Louis • California encephalities The viruses cycle between wild animals and mosqiutoes or ticks, but humans are noot usually reservior hosts. The disease begins with a bite, which releases a virus into the tissues and nearby lymphatics.

Prolonged viremia establishes virus in the brain, where inflammation can cause swelling and damage t the brain, nerves, and meninges. Symptoms may also include: Coma Convulsions Paralysis Tremor

loss of coordination memory deficits changes in speech and personality heart disorders

COLORADO TICK FEVER also called Mountain tick fever, Mountain fever, and American mountain fever) is an acute viral infection transmitted from the bite of an infected wood tick (Dermacentor andersoni). It should not be confused with the bacterial tick-borne infection, Rocky Mountain Spotted Fever.

WESTERN EQUINE ENCEPHALITIES The Western equine encephalitis virus is the causative agent of relatively uncommon viral disease Western equine encephalitis (WEE). An Alphavirus of the family Togaviridae, the WEE virus is an arbovirus (arthropod-borne virus) transmitted by mosquitoes of the genera Culex and Culiseta. There have been under 700 confirmed cases in the U.S. since 1964.

EASTERN EQUINE ENCEPHALITIES Eastern equine encephalomyelitis virus (EEE), commonly called sleeping sickness or "Triple E", is a zoonotic alphavirus and arbovirus present in North, Central and South America and the Caribbean. EEE was first recognized in Massachusetts, USA in 1831 when 75 horses died of encephalitic illness. Epizootics in horses have continued to occur regularly in the United States. EEE is found today in the eastern part of the country and is often associated with coastal plains.

California encephalitis • California encephalitis virus causes encephalitis in humans. Mosquitos serve as its vectors. For this reason this virus is known as an arbovirus (arthropod-borne virus). • California encephalitis virus belongs to the Bunyaviridae family of viruses, and the genus Bunyavirus. La Crosse Virus is the most important California encephalitis virus in the United States. Other related viruses include California encephalitis virus and Jamestown Canyon virus.

La Crosse encephalitis Symptoms • nausea • headache • vomiting in milder cases and • seizures • coma • paralysis • permanent brain damage in severe cases

St. Louis encephalitis • St. Louis Encephalitis is a disease caused by the Culex mosquito borne St. Louis Encephalitis virus. St. Louis encephalitis virus is related to Japanese encephalitis virus and is a member of the Flaviviridae subgroup. This disease mainly affects the United States. Occasional cases have been reported from Canada and Mexico.

Viral hemorrhagic fever The viral hemorrhagic fevers (VHFs) are a diverse group of animal and human illnesses that are caused by five distinct families of RNA viruses: the Arenaviridae, Filoviridae, Bunyaviridae, Togaviridae, and Flaviviridae. All types of VHF are characterized by fever and bleeding disorders and all can progress to high fever, shock and death in extreme cases. Some of the VHF agents cause relatively mild illnesses, such as the Scandinavian nephropathia epidemica, while others, such as the African Ebola virus, can cause severe, life-threatening disease.

Signs and symptoms of VHFs • • • • • • • • • • • •

fever and bleeding diathesis flushing of the face and chest petechiae frank bleeding edema Hypotension shock Malaise headache vomiting diarrhea

Yellow fever • is an acute viral disease. The virus, a 40 to 50 nm enveloped RNA virus of the family of Flaviviridae is transmitted by the bite of mosquitoes (the yellow fever mosquito, Aedes aegypti, and other species). Yellow fever is an important cause of hemorrhagic illness in tropical and subtropical areas of African and South American despite existence of an effective vaccine. The yellow refers to the jaundice symptoms that affect some patients.

Dengue fever • dengue hemorrhagic fever (DHF) are acute febrile diseases, found in the tropics, and caused by four closely related virus serotypes of the genus Flavivirus, family Flaviviridae. • It is also known as breakbone fever.

diagnosis of dengue • The diagnosis of dengue is usually made clinically. The classic picture is high fever with no localising source of infection, a petechial rash with thrombocytopenia and relative leukopenia low platelet and white blood cell count. Care has to be taken as diagnosis of DHF can mask end stage liver disease and vice versa. • Fever, bladder problem, constant headaches, eye pain, severe dizziness and loss of appetite.

• Hemorrhagic tendency (positive tourniquet test, spontaneous bruising, bleeding from mucosa, gingiva, injection sites, etc.; vomiting blood, or bloody diarrhea) • Thrombocytopenia (<100,000 platelets per mm³ or estimated as less than 3 platelets per high power field) • Evidence of plasma leakage (hematocrit more than 20% higher than expected, or drop in haematocrit of 20% or more from baseline following IV fluid, pleural effusion, ascites, hypoproteinemia) • Encephalitic occurrences.

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