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Venezuelan Equine Encephalitis

Venezuelan Equine Encephalitis (etiology)

Venezuelan equine encephalitis is caused by the Venezuelan equine encephalitis virus, an Alphavirus belonging to the Togaviridae family. It is characterized by the acute onset of a febrile illness, myalgia, nausea, vomiting and encephalitis. Although there are no recent reports of the disease, it could be a potential biological weapon as it can cause serious nervous system sequelae.


Presentation

Venezuelan equine encephalitis (VEE) has been associated with epidemics in South and Central America, especially regions of Colombia, although it has not shown a resurgence recently [1].

The symptoms and signs of the disease resemble those of several other acute, febrile, infectious illnesses like dengue fever. So the diagnosis is often missed in the initial stages of the illness, especially if there are poor awareness and unavailability of special laboratory testing facilities [2].

Humans acquire the infection following a mosquito bite. The incubation period is between 24 hours to six days after exposure to the virus [3] [4]. The common symptoms are flu-like with myalgia, fatigue, nausea, vomiting, diarrhea, headache and fever. The symptoms abate after a few days but can recur and in some cases the patients may remain symptomatic for up to 2 weeks.

Between 4 to 14% of cases can develop neurological symptoms 5 to 10 days after exposure. Young adults and children are especially prone to encephalitis due to the Venezuelan equine encephalitis virus. The symptoms include increased sleepiness, confusion, severe headaches, photophobia, neck rigidity, seizures, neurological deficits, coma, and death [5]. Death can be due to encephalitis or gastrointestinal, pulmonary or brain hemorrhage.

Pregnant women who get infected are at risk of aborting the fetus. Other complications include fetal death, stillbirth or delivering a baby with malformations [6].

Fever
  • , Ebola/immunology Hemorrhagic Fever, Ebola/prevention & control Humans Macaca fascicularis Marburg Virus Disease/immunology Marburg Virus Disease/prevention & control Marburgvirus/immunology* Mice Mice, Inbred BALB C Plasmids/immunology Rabbits Reverse[ncbi.nlm.nih.gov]
  • A mosquito-borne virus that usually causes mild and self-limiting disease in humans, characterised by symptoms that resemble influenza or dengue fever (e.g., fever, headache, malaise, nausea).[bestpractice.bmj.com]
  • A different pattern of response was seen after aerosol exposure to VEEV-IIIA:even at the highest dose tested, onset of fever was not seen until 3 days after exposure, and the fever was not biphasic (figure 1B); furthermore, the peak of the fever did not[academic.oup.com]
  • The symptoms and signs of the disease resemble those of several other acute, febrile, infectious illnesses like dengue fever.[symptoma.com]
High Fever
  • Healthy adults who become infected may experience flu-like symptoms, such as high fevers and headaches. People with weakened or compromised immune systems, the young, and the elderly can become severely ill or die from this disease.[valentbiosciences.com]
  • Signs include depression and a high fever, followed by a period when the horse appears blind, nervous and uncoordinated, which progresses to muscle tremors, yawning and eventually complete paralysis.[drsfostersmith.com]
  • Healthy adults who become infected by the virus may experience flu -like symptoms, such as high fevers and headaches. People with weakened immune systems and the young and the elderly can become severely ill or die from this disease.[en.wikipedia.org]
Veterinarian
  • Practitioners must report any suspected cases of VEE in the United States to their state veterinarians so a quarantine can be put into effect.[thehorse.com]
  • In many countries, the government may also be an employer of veterinarians. State and local governments also employ veterinarians, Veterinarians and their practices may be specialized in certain areas of veterinary medicine 4.[wikivisually.com]
  • Talk to your veterinarian for more prevention ideas and suggestions.[wagwalking.com]
  • The use of killed VEE vaccine should be performed only in high-risk areas of the US, at the discretion of the attending veterinarian, or when necessary, with input from state agriculture officials.[aaep.org]
  • The reporting of these diseases (or suspicion of such) on an international and national basis is a basic duty of all veterinarians to ensure the health and safety of horses and people.[merckvetmanual.com]
Chills
  • Venezuelan equine encephalitis (VEE) is a mosquito-borne viral disease characterized by fever and one or more of the following: severe headache, back pain, myalgias, prostration, chills, nausea, vomiting, weakness and other flu-like symptoms.[ncbi.nlm.nih.gov]
  • Shaking chills, arthralgia, photophobia, ocular pain, nausea, vomiting. The entire course of the illness lasts less than a week.[privatehealth.co.uk]
  • Other symptoms that may appear include myalgia (72%), vomiting (50%), drowsiness (40%), chills (20%), sore throat (20% ), and diarrhea (20%). Fever can come and go. Patients may be incapacitated by malaise and fatigue for 1 - 2 weeks.[daretoprepare.com]
  • Less common symptoms of Venezuelan equine encephalitis include: [8] [15] Fever Chills Headache Fatigue Muscle pain Joint pain Throat pain Dizziness Light-sensitivity Altered mental status Physical Examination Physical examination for Venezuelan equine[wikidoc.org]
  • Based on interviews and physical examinations of 23 inpatients at local hospitals on September 27-28, prominent manifestations included fever (100%); convulsions (98%); headache (56%); photophobia (56%); myalgias (56%); and chills, vomiting, and diarrhea[cdc.gov]
Rigor
  • We have overcome the intrinsic tolerance to the 'self' TAA rat neu and elicited an effective anti-tumor immune response using this alphavirus replicon vector system and a designed target antigen in a rigorous rat mammary tumor model.[ncbi.nlm.nih.gov]
Vomiting
  • The common symptoms are flu-like with myalgia, fatigue, nausea, vomiting, diarrhea, headache and fever. The symptoms abate after a few days but can recur and in some cases the patients may remain symptomatic for up to 2 weeks.[symptoma.com]
  • A 17-year-old female traveled to Belize and developed vomiting, diarrhea, fever, headaches, and myalgias. Over the next few hours, she became disoriented and had a generalized seizure.[ncbi.nlm.nih.gov]
  • Shaking chills, arthralgia, photophobia, ocular pain, nausea, vomiting. The entire course of the illness lasts less than a week.[privatehealth.co.uk]
  • […] clinics in the towns of Mayapo, Manaure, and El Pajaro in the municipality of Manaure in La Guajira state reported an increased number of patients seeking care for acute febrile illnesses characterized by intense headache, muscle pain, prostration, and vomiting[cdc.gov]
Nausea
  • The common symptoms are flu-like with myalgia, fatigue, nausea, vomiting, diarrhea, headache and fever. The symptoms abate after a few days but can recur and in some cases the patients may remain symptomatic for up to 2 weeks.[symptoma.com]
  • Venezuelan equine encephalitis (VEE) is a mosquito-borne viral disease characterized by fever and one or more of the following: severe headache, back pain, myalgias, prostration, chills, nausea, vomiting, weakness and other flu-like symptoms.[ncbi.nlm.nih.gov]
  • ., fever, headache, malaise, nausea). CNS infection can lead to long-term neurological sequelae and death, particularly in children. Occurs mainly in Central and South America, but cases have been reported in North America.[bestpractice.bmj.com]
  • Shaking chills, arthralgia, photophobia, ocular pain, nausea, vomiting. The entire course of the illness lasts less than a week.[privatehealth.co.uk]
  • Usually, flu-like symptoms such as headache, myalgia, fatigue, vomiting, nausea, diarrhoea, pharyngitis and fever appear abruptly, 2 to 5 days after exposure to the virus (3).[msdsonline.com]
Tachycardia
  • The VEE virus can also cause retro-orbital and occipital headaches as well as leucopenia and tachycardia (3).[msdsonline.com]
Hypertension
  • […] failure Stroke Ataxia, aphasia, dizziness Varies depending on classification of stroke; presents with positional vertigo, high blood pressure, extremity weakness Intracranial hemorrhage Headache, coma, dizziness Lobar hemorrhage, numbness, tingling, hypertension[wikidoc.org]
Photophobia
  • The symptoms include increased sleepiness, confusion, severe headaches, photophobia, neck rigidity, seizures, neurological deficits, coma, and death. Death can be due to encephalitis or gastrointestinal, pulmonary or brain hemorrhage.[symptoma.com]
  • Shaking chills, arthralgia, photophobia, ocular pain, nausea, vomiting. The entire course of the illness lasts less than a week.[privatehealth.co.uk]
  • […] be differentiated from other diseases that cause fever, headache, seizures, and altered mental status, such as: [8] [10] [11] [12] [13] Disease Similarities Differentials Meningitis Classic triad of fever, nuchal rigidity, and altered mental status Photophobia[wikidoc.org]
  • Symptoms of encephalitis, only appearing in a minority of cases, occur 4-10 days after exposure and include somnolence, convulsions, confusion, photophobia, and coma.[msdsonline.com]
  • Based on interviews and physical examinations of 23 inpatients at local hospitals on September 27-28, prominent manifestations included fever (100%); convulsions (98%); headache (56%); photophobia (56%); myalgias (56%); and chills, vomiting, and diarrhea[cdc.gov]
Headache
  • The common symptoms are flu-like with myalgia, fatigue, nausea, vomiting, diarrhea, headache and fever. The symptoms abate after a few days but can recur and in some cases the patients may remain symptomatic for up to 2 weeks.[symptoma.com]
  • A 17-year-old female traveled to Belize and developed vomiting, diarrhea, fever, headaches, and myalgias. Over the next few hours, she became disoriented and had a generalized seizure.[ncbi.nlm.nih.gov]
  • Venezuelan equine encephalitis virus must be differentiated from other diseases that cause fever, headache, seizures, and altered mental status.[wikidoc.org]
  • ., fever, headache, malaise, nausea). CNS infection can lead to long-term neurological sequelae and death, particularly in children. Occurs mainly in Central and South America, but cases have been reported in North America.[bestpractice.bmj.com]
Seizure
  • Over the next few hours, she became disoriented and had a generalized seizure. She was given diazepam, 50% dextrose, phenytoin, mannitol, and vitamin K. A computed tomographic scan of the head was unremarkable.[ncbi.nlm.nih.gov]
  • The symptoms include increased sleepiness, confusion, severe headaches, photophobia, neck rigidity, seizures, neurological deficits, coma, and death. Death can be due to encephalitis or gastrointestinal, pulmonary or brain hemorrhage.[symptoma.com]
  • Less than 1% of adults develop severe encephalitis (swelling of the brain) featuring meningismus, lack of muscular coordination, seizures, and coma.[daretoprepare.com]
  • Complications Neurologic symptoms are rare and these include depressed sensorium, meningismus, generalized weakness, focal and generalized seizures.[privatehealth.co.uk]
  • Venezuelan equine encephalitis virus must be differentiated from other diseases that cause fever, headache, seizures, and altered mental status.[wikidoc.org]
Rabies
  • Home Back Tests information Rabies (Laboratory authorized by the European Union; Laboratory accepted by Japan) Tests for movement of animals (South Africa, Australia, India, New Zealand) Identification of animal species in meat or fish products Marine[ivami.com]
  • Transduction of motor neurons and muscle fibers by intramuscular injection of HIV-1-based vectors pseudotyped with select rabies virus glycoproteins . J Neurosci Methods 2006; 157 : 208–217. 13.[nature.com]
  • Australia Murray Valley encephalitis virus: Australia Rabies Tick-borne encephalitis virus: central Europe through Eurasia Adenovirus Parvovirus B19 Hendra virus, Nipah virus: Australia, SE Asia Other less common viral etiologies include: Influenza Rabies[hopkinsguides.com]
  • Diagnosis An accurate diagnosis is important since other infectious agents (including rabies, equine herpesvirus-1, WNV, and equine protozoal myeloencephalitis, or EPM) could be a potential cause of symptoms.[thehorse.com]
  • […] hyperexcitability blindness lack of coordination and balance inability to move staggering or standing with an open stance seizures Infections that have similar signs You may also see similar clinical signs if your animal is infected with one of the following: rabies[gov.uk]
Confusion
  • The symptoms include increased sleepiness, confusion, severe headaches, photophobia, neck rigidity, seizures, neurological deficits, coma, and death. Death can be due to encephalitis or gastrointestinal, pulmonary or brain hemorrhage.[symptoma.com]
  • The VEE virus (VEEV) is a type of alphavirus that typically causes mild to severe influenza-like symptoms, but can progress to serious neurological complications such as insomnia, seizures, confusion, and coma.[sri.com]
  • Symptoms of encephalitis, only appearing in a minority of cases, occur 4-10 days after exposure and include somnolence, convulsions, confusion, photophobia, and coma.[msdsonline.com]
  • In about ten of a hundred of these cases, neurological symptoms develop soon afterwards, including convulsions, confusion, drowsiness, and sensitivity to light.[animalspeoplepathogens.com]
Somnolence
  • Ataxia, lethargy Multiple sclerosis : clinically, nystagmus, internuclear ophthalmoplegia, Lhermitte's sign ; on imaging, well-demarcated ovoid lesions with possible T1 hypointensities (“black holes”) Acute disseminated encephalomyelitis : clinically, somnolence[wikidoc.org]
  • Symptoms of encephalitis, only appearing in a minority of cases, occur 4-10 days after exposure and include somnolence, convulsions, confusion, photophobia, and coma.[msdsonline.com]
  • Highlands J and EEE infections can also cause depression, somnolence, decreased egg production and increased mortality in turkeys.[nj.gov]

Workup

Venezuelan equine encephalitis is clinically diagnosed in less than 5% of infected individuals. After obtaining a detailed history and physical examination of the febrile patient, routine laboratory investigations like complete blood count, serum electrolytes, liver function tests, and urinalysis are performed. Usually, the results of these tests are not indicative of any specific infection. However, in patients with encephalitis, the transaminases may be elevated. Thrombocytopenia and lymphopenia may also be present.

The VEE virus can be isolated from either blood or a throat swab obtained 1 to 3 days after symptom onset. In patients with encephalitis, lumbar puncture is performed and cerebrospinal fluid analysis shows normal glucose concentration with marked mononuclear pleocytosis. Enzyme-linked immunosorbent assay (ELISA) is useful to diagnose the causative virus [7]. Polymerase chain reaction (PCR) is another useful technique to detect the virus [7].

Radiological tests are helpful to diagnose VEE and its complications. Chest radiography typically reveals acute pneumonitis while magnetic resonance imaging (MRI) can establish encephalitis.

Histopathology of affected organs shows congestion, hemorrhage with perivascular and leptomeningeal inflammatory cellular infiltrates and focal necrosis. Basal ganglia, substantia nigra as well as the cerebral cortex and deep white matter involvement has been noted. The findings indicate that the virus targets the human reticuloendothelial and lymphoid system [6].

HLA-DR3
  • The vaccinated HLA-DR3 mice developed significant cellular immune responses to 4 of the 25 (16%) tested individual class II peptides as measured by IFN-γ ELISpot assays.[ncbi.nlm.nih.gov]

Treatment

  • Post-virus exposure treatment with (-)-carbodine was effective in significantly improving disease parameters in mice infected with TC-83 VEEV when treatment was initiated as late as 4 days post-virus installation (dpi).[ncbi.nlm.nih.gov]

Prognosis

  • Complications Complications of Venezuelan equine encephalitis include: Seizures Loss of basic motor skills Loss of coordination Meningitis Dysarthria Affective disorders Miscarriage in pregnant women Prognosis Prognosis for Venezuelan equine encephalitis[wikidoc.org]
  • PROGNOSIS : Secondary bacterial infections of the respiratory and urinary tracts are major complications of acute encephalitis.[atsu.edu]
  • Horses with intermittent or focal neuropathies have a better prognosis than those with complete flaccid paralysis or that appear comatose.[merckvetmanual.com]
  • Prognosis after West Nile virus infection. Ann Intern Med. 2008;149(4):232-41. [PMID:18711153] Comment: Longitudinal cohort of 156 pts. Most recovered both mental and physical function by 1 year after infection onset.[hopkinsguides.com]

Etiology

  • The first natural equine epizootic was recognized in Chiapas in 1993 and since then, numerous studies have characterized the etiologic strains, including reverse genetic studies that incriminated a specific mutation that enhanced infection of epizootic[ncbi.nlm.nih.gov]
  • A longitudinal study of respiratory viruses and bacteria in the etiology of acute otitis media with effusion. ‎ Page 57 - Isolation of St. Louis encephalitis viruses from mosquitoes in the Tampa Bay area of Florida during the epidemic of 1962. ‎[books.google.com]
  • Venezuelan equine encephalitis in Panama: fatal endemic disease and genetic diversity of etiologic viral strains. PLoS Negl Trop Dis. 2009;3:e472.[bestpractice.bmj.com]
  • Smith DOI: Published November 2001 Abstract The etiological role of human papillomaviruses (HPV) in cervical and other cancers suggests that therapeutic vaccines directed against requisite viral antigens may eradicate tumors or their precursors.[cancerres.aacrjournals.org]
  • . : Arboviral etiologies of acute febrile illnesses in western South America, 2000–2007. PLoS Negl. Trop. Dis. 4(8),E787 ( 2010 ).[futuremedicine.com]

Epidemiology

  • Mexico/epidemiology Middle Aged Molecular Epidemiology Molecular Sequence Data Phylogeny RNA, Viral/genetics Sequence Analysis, DNA Seroepidemiologic Studies Young Adult Substance RNA, Viral Secondary source ID GENBANK/JQ859933 GENBANK/JQ859934 GENBANK[ncbi.nlm.nih.gov]
  • It also addresses the importance of preventing and controlling infectious disease outbreaks with coverage of epidemiology, biosecurity, antimicrobial therapy, and recognizing foreign equine diseases.[books.google.com]
  • "PAHO Epidemiological Bulletin: Outbreak of Venezuelan Equine Encephalities". Retrieved 2007-03-17. "PATHINFO: Venezuelan Equine Encephalitis Virus". Archived from the original on 2006-08-28. Retrieved 2007-03-17. Esparza J, Sánchez A (1975).[en.wikipedia.org]
Sex distribution
Age distribution

Pathophysiology

  • Pathophysiology Venezuelan equine encephalitis virus is usually transmitted via mosquitos to the human host.[wikidoc.org]

Prevention

  • Fever, Ebola/prevention & control Humans Macaca fascicularis Marburg Virus Disease/immunology Marburg Virus Disease/prevention & control Marburgvirus/immunology* Mice Mice, Inbred BALB C Plasmids/immunology Rabbits Reverse Transcriptase Polymerase Chain[ncbi.nlm.nih.gov]
  • Ideal for both practitioners and students, this comprehensive resource covers the diagnosis, treatment, and prevention of infectious disease in horses.[books.google.com]

References

Article

  1. Ferro C, De Las Salas J, Gonzalez M, et al. Do some conditions contribute to the reemergence of the Venezuelan equine encephalitis virus in the Colombian Alta Guajira? Biomedica. 2015; 35(1):62-72
  2. Weaver SC, Reisen WK. Present and future arboviral threats. Antiviral Res. 2010;85(2):328-45.
  3. Krauss H, Weber A, Appel M et al. (eds.). Zoonoses Infectious Diseases Transmissible from Animals to Humans (3rd ed.). Washington: ASM press. 2003
  4. Heymann DL Control of Communicable Diseases Manual (19th ed.). Washington, D.C.: American Public Health Association. 2008
  5. Weaver SC, Ferro C, Barrera R, et al. Venezuelan equine encephalitis. Annual Review of Entomology. 2004;49:141-174.
  6. de la Monte S, Castro F, Bonilla NJ, et al. The systemic pathology of Venezuelan equine encephalitis virus infection in humans. The American Journal of Tropical Medicine and Hygiene. 1985;34(1): 194-202.
  7. Murray PR, Baron EJ, Jorgensen JH, et al. (eds.). Manual of Clinical Microbiology (9th ed.). Washington: ASM Press. 2007

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Last updated: 2019-07-11 20:12