2. INTRODUCTION TO ARBOVIRUSES
Nomenclature
Common features
Classification
Arboviruses: Neglected Tropical Diseases – NTDs
Neglected tropical diseases (NTDs) are a diverse group of tropical infections which are especially common in low-
income populations in developing regions of Africa, Asia, and the Americas. They are caused by a variety of pathogens
such as viruses, bacteria, protozoa and helminths. These diseases are contrasted with the big three diseases
(HIV/AIDS, tuberculosis, and malaria), which generally receive greater treatment and research funding.
3. ARBOVIRUSES – SHARED FEATURES
‘ArBo’ virus- Arthropod Borne viruses
RNA viruses: Positive sense (except Bunyavirus)
Common features shared :
1. Geographic distribution – tropical climate with rainfall – some rare exceptions
2. Modes of Transmission – hematogenous vector borne diseases
3. Clinical presentation & management
4. Diagnosis and viral isolation techniques
5. Control measures
4. INTERESTING NOMENCLATURE
BASED ON
Place of discovery : Kyasanur forest disease
Vector responsible for spread: Colorado tick fever / Sandfly fever virus
Clinical features:
1. Yellow fever – jaundice (Flavivirus also – Flavus – Latin for Yellow
2. Chikungunya – Makonde (Tanzania) word “ Kungunyala” - bent up or folded
3. Dengue: Swalihi – Ka denga pepo – sudden seizure by a demon!
4. Japanese encephalitis – combination of place and clinical features
6. ARBOVIRAL DISEASES – ENTIRE SPECTRUM
MOSQUITO BORNE
1. Dengue
2. Chikungunya
3. Japanese encephalitis
4. Yellow fever
5. Zika
6. West Nile
7. Eastern Equine encephalitis
8. Western Equine encephalitis
9. Venezuelan Equine encephalitis
10. St. Louis encephalitis
11. Californian “serogroup” encephalitis
12. Rift valley fever
13. Murray valley encephalitis
14. Rocio viral encephalitis
15. Spondweni virus
16. O’Nyong nyong
17. Sindbis
18. Ross river
19. Mayaro
20. Oro pouche
TICK BORNE
1. Kyasanur Forest disease
2. Colorado tick fever
3. RSSE Complex
4. Louping ill
5. Powassan
6. Omsk hemorrhagic fever
7. Crimean Congo
RODENT BORNE
1. Hemorrhagic fever with renal syndrome (HFRS)
2. Lassa fever
SANDFLY BORNE
Sandfly fever
DEERMICE BORNE
Hanta virus pulmonary syndrome
FLAVIVIRUS – 14 diseases
ALPHAVIRUS – 8 diseases
BUNYAVIRUS – 3 diseases
IMPORTANT GENERA
7. APPROACH TO EACH VIRUS & DISEASE
1. Most common & relevant in India – to – rarer infections across the world
2. History & world-wide distribution
3. Vector & epidemiology
4. Virus morphology
5. Pathophysiology, clinical manifestation
6. Lab diagnosis
7. Treatment & Prevention (vaccines)
9. HISTORY
First probable case: Jin dynasty China – 265-420 AD “water poison” associated
with flying insects
Disease identified and named in 1770 followed by first recognized epidemics
simultaneously in Asia, Africa and North America
First confirmed case: 1780 Dr. Benjamin Rush – Break-bone fever –
Philadelphia epidemic *
20th century – Viral etiology and transmission by mosquitoes
Second world war – coincidental transport of the Aedes mosquito
around the world in cargo - dissemination of the virus
First DHF case in 1950s during the epidemics in Philippines & Thailand
INDIA:
First epidemic of clinical dengue-like illness: Chennai in 1780
First virologically proved epidemic of DF: Calcutta & Eastern Coast of India in
1963-1964
First major wide spread epidemics of DHF/DSS: 1996 Delhi and Lucknow then
spread all over the country
“Rush, AB. An account of the bilious
remitting fever, as it appeared in
Philadelphia in the summer and
autumn of the year 1780.
Inquiries and observations. Prichard
and Hall, Philadelphia; 1789: 104–
117”n: Medical
10. DISTRIBUTION - SHARP RISE IN CASES
Important causes of world-wide increase in incidence & transmission of dengue:
• Unplanned urban overpopulation – water, sewage & waste management
• Poor vector control secondary to above especially in high breeding seasons
• Climate change & viral evolution – linked to El Nino conditions
• Increased international travel between endemic areas
WHO - CDC figures
Worldwide
50-100 million cases every year
5,00,000 DHF cases
22,000 deaths – most in children
India
2006-2012: 6 million cases
25% public sector
75% private sector
11. VECTORS
A. aegypti - higher transmission ability
Nervous feeder – multiple bites
Higher affinity towards humans for blood meal
Located near indwelling human habitats
A. albopictus – lower transmission ability
Concordant feeder – single bite - full meal
Higher affinity to small mammals & birds than humans
Located in vegetations farther from human habitats
Better tolerance to colder climates*
Daytime feeders – females only
13. DENGUE VIRUS MORPHOLOGY
DENV is a 50-nm single stranded positive sense RNA virus enveloped with a lipid membrane
The virus has a genome of about 11000 bases that encodes a single large polyprotein that is subsequently cleaved into several
structural and non-structural mature peptides.
In addition to the E glycoprotein, only one other viral protein, NS1, has been associated with a role in protective immunity.
14. DENGUE VIRUS – SEROTYPES & GENOTYPES
4 Serotypes: DEN 1,2,3,4; 5 discovered in Thailand in 2013
Serotype 2 most commonly associated with more severe disease and epidemics
DV 1,2 & 3 More common in India although DV 4 is also seen.
DV - 1 DV - 2 DV - 3 DV - 5
SEROTYPE DV - 4
1. Asian I (AI),
2. Asian II (AII)
3. Cosmopolitan(C)
4. American (AM),
5. Asian/American (AA)
6. Sylvatic (S)
GENOTYPE
LINEAGE
1. G- I
2. G-II
3. G-III
4. G- IV
5. G –V
1. G- I
2. G-II
3. G-III
4. G- IV
1. G- I
2. G-II
3. G-III
4. G- IV
5. G –V
15. PATHOPHYSIOLOGY
Still partly understood due to lack of suitable animal model to simulate the DHF and DSS presentation
Tropism to 3 major systems – Immune system, Liver & endothelial cell linings
18. LAB DIAGNOSIS - SEROLOGY
ANTIBODY DETECTION:
• ELISA – Enzyme linked Immunosorbent assay especially MAC ELISA
• ICT – Immunochromatographic test based on lateral flow assay
Antigen detection:
• In blood: Flavivirus specific non-structural antigen -1 – ELISA & ICT
• Antigen detection in fixed tissues: Group specific antigens in peripheral blood leukocytes, liver, lung at autopsy
Markers of active infection:
• Antigen detection
• IgM detection
• Seroconversion to IgG
• Four-fold rise in titers of paired sera collected 2-3 weeks apart
Advantages:
• Low cost & simplicity
• Best tools for epidemiological surveillance
Disadvantages:
• Antibody assays non-specific: broad group reactive antigens are used
• IgG cannot differentiate from recent and remote infection unless rising titers are demonstrated
19. RAPID TESTS
Immunochromatography – lateral flow
In Vietnam the sensitivity and specificity of the test
was 69.2% (95% CI: 62.8% to 75.6%) and 96% (95%
CI: 92.2% to 99.8) respectively. In Malaysia the
performance was similar with 68.9% sensitivity
(95% CI: 61.8% to 76.1%) and 96.7% specificity (95%
CI: 82.8% to 99.9%) compared to RT-PCR.
Importantly, when the Dengue Early Rapid test was
used in combination with the IgM/IgG test the
sensitivity increased to 93.0%. ®
The sensitivity and specificity
in diagnosing acute dengue infection in the SD Duo
NS1/IgM were 88.65% and 98.75%, respectively. ®
20. ELISA
In conclusion, the current evaluation of the
SD dengue NS1 Ag ELISA shows that this assay has
a sensitivity of 76.76% (95% CI, 70.61 to 82.90)
and a specificity of 98.31% (95% CI, 94.91 to 100)
and is useful, sensitive, and specific for the
diagnosis of dengue virus infection. ®
The NIV MAC-ELISA showed a high sensitivity
(96%) as compared to PanBio Rapid (73%) and
PanBio IgM ELISA (72%).
21. MOLECULAR METHODS- PCR
POLYMERASE CHAIN REACTION
1. Reverse transcriptase PCR
2. Real time Reverse transcriptase – qRT PCR
(added advantage of quantifying viral load)
Single/Multiplex
Probe used: Taqman fluorprobe (Taq polymerase)
Advantages:
Highly sensitive, rapid and can be serotype specific
Shortcomings:
Prone to contamination
High cost
Next in line:
Iso-thermic cycling :
NASBA
RT LAMP
23. VIRUS ISOLATION & CULTIVATION
Adult or larval mosquito inoculation: most sensitive
Toxorhynchites (ideal)
Aedes aegypti
Aedes albopictus (adult male)
Mosquito cell lines: most commonly used
C6/36
AP61 cell lines
Mammalian cell lines:
Vero & LLC-MK2
Suckling mice – intracerebral inoculation
Detection of viral growth: Direct immunofluorescence using:
Group specific monoclonal antibodies
Serotype specific monoclonal antibodies
24. DENGUE VACCINE
CYD-TDV, sold under the brand name Dengvaxia and made by Sanofi Pasteur , is a live attenuated tetravalent chimeric
vaccine made using recombinant DNA technology by replacing the PrM (pre-membrane) and E (envelope) structural genes
of the yellow fever attenuated 17D strain vaccine with those from four of the five dengue serotypes.
DHF type reaction seen in recipients without history of prior infection* hence suspended
26. CHIKUNGUNYA HISTORY & DISTRIBUTION
First seen in: Tanzania 1952
Vector – Aedes aegypti
First case in India – 1963 epidemics along with dengue in Kolkata & Chennai few cases till 973 quiescent till 2006
Major outbreak in Andra Pradesh Tamil Nadu Kerala Karnataka Delhi affecting nearly a million people
Reasons for re-emergence:
Novel mutation in the virus – E1 – A226V alanine in position 226 of e1 glycoprotein replaced by valine
New vector – Aedes albopictus – mutated virus 100 times more infective to A. albopictus than A. aegpti
As of now, 62,000 cases in 2017 in India – Half of this burden in Karnataka
27. Viral particle:
Chikungunya virus is a small
60–70 nm-diameter, spherical,
enveloped, positive-strand
RNA virus.
(E1 glycoprotein gene target for PCR)
Genotypes:
1. West African
2. East/Central/South African
3. Asian
(correlate with area of distribution –
except the 2006 epidemic in India)
CHIKUNGUNYA VIRUS - MORPHOLOGY
28. High levels of specific cytokines have been linked to more severe acute disease: interleukin-6 (IL-6), IL-1β, RANTES, monocyte
chemoattractant protein 1 (MCP-1), monokines induced by gamma interferon (MIG), and interferon gamma-induced protein
10 (IP-10).
CHIKUNGUNYA PATHOPHYSIOLOGY
30. CHIKUNGUNYA - LAB DIAGNOSIS
Serological tests:
MAC ELISA for IgM is test of choice
No antigen tests available
Molecular tests:
PCR – RT PCR using Taqman probe
RT LAMP using SYBR Green stain
Virus culture & isolation
33. JAPANESE ENCEPHALITIS – HISTORY & DISTRIBUTION
First discovered in Japan –
1871 – Summer Encephalitis B
– differentiate it from
Encephalitis lethargica – von
Economo disease which was
endemic at that time.
Rapidly spread to several
other countries over the last
decades including India.
JEV is now the main cause of
viral encephalitis in many
countries of Asia with an
estimated 68 000 clinical cases
every year.
Vector:
Culex tritaeniorhynchus
Culex Vishnui – India
34. Eastern Uttar Pradesh – most endemic - Gorakhpur district BRD Hospital *
JAPANESE ENCEPHALITIS – INDIAN SCENARIO
35. JE - EPIDEMIOLOGY & TRANSMISION CYCLES
PIGS
ARDEID
BIRDS
(HERONS)
Horses – only animals to be symptomatically affected by the JE virus
Breeding seen preferentially in rice-fields*
36. Based on the envelope gene, there are five genotypes (I–V).
The Muar strain, isolated from a patient in Malaya in 1952, is the prototype strain of genotype V.
Genotype IV appears to be the ancestral strain, and the virus appears to have evolved in the
Indonesian–Malaysian region.
JE VIRUS - MORPHOLOGY
37. JE - PATHOPHYSIOLOGY
Auto-toxic loop of Microglial activation
Increased Microglial (resident immune
cell) activation in response to JE
infection
Secretion of cytokines such IL-1, TNF –α,
Prostaglandins & reactive oxygen
species
No regulatory counter mechanism in
the brain – leading to neuronal injury
particularly seen in Thalamus &
Midbrain
38. Iceberg phenomenon:
SUBCLNICAL: Most JEV infections are mild - 1 in 250
infections results in severe clinical illness.
STAGES OF SEVERITY:
Prodromal stage – febrile illness
Acute encephalitis stage: high fever, headache, neck
stiffness, disorientation, coma, seizures, spastic
paralysis and ultimately death.
The case-fatality rate as high as 30%
Late stage & sequalae: Of those who survive, 20%–30%
suffer permanent intellectual, behavioral or
neurological problems such as paralysis, recurrent
seizures or the inability to speak.
JE - CLINICAL PRESENTATION
39. JE - LAB DIAGNOSIS
Lab diagnosis of JE is accomplished by testing of serum / cerebrospinal fluid (CSF) to detect virus-specific IgM antibodies.
PCR – RT PCR done
In fatal cases, nucleic acid amplification, histopathology with immunohistochemistry, and virus culture of autopsy tissues can
also be useful.
41. JAPANESE ENCEPHALITIS – VACCINATION IN INDIA
Live Attenuated SA-14-14-2 Vaccine: First dose of the vaccine can be administered at 9 months along with measles vaccine and second at 16 to 18
months at the time of 1st booster of DTP vaccine.
JEEV E: Primary schedule of 2 doses of 0.25mL for children aged 1- 3 years and 2 doses of 0.5mL for children >3 years, adolescents and adults
administered intramuscularly on days 0 and 28
JENVAC® Two doses of the vaccine (0.5 ml each) administered intramuscularly at 4 weeks interval for the primary immunization series for office
practice starting from 1 year of age.
43. YELLOW FEVER – HISTORY & DISTRIBUTION
Origins – mostly in Africa
Philadelphia epidemic 1793:
Dr. Benjamin Rush, a doctor's apprentice during the city's 1762 yellow fever epidemic, saw the pattern; he recognized that
yellow fever had returned. Almost the entire city including George Washington were evacuated from Philadelphia.
Walter Reed & Finlay – Aedes transmission - Reed Yellow Fever eradiation project – Completion of Panama Canal
India – Yellow fever “receptive” area but the disease DOES NOT EXIST in India
Reasons:
Airport measures: 6 day quarantine for unvaccinated travelers
Breteau index for A. aegypti maintained <1 in 400mts surrounding the airport
Dengue endemicity – cross reactivity of Dengue antibodies with YF – reverse does not apply
44. YELLOW FEVER – EPIDEMIOLOGY & CYCLES
Vector: Aedes aegypti in urban cycle ; Sylvatic cycle: Haemagogus spegazzini in South America ; Aedes africanus &
A.simpsoni in Africa
48. YELLOW FEVER - VACCINE
The present YF vaccines are based on a wild-type YF virus isolated in Ghana in 1927. Numerous mutations in the viral
structural and non-structural genes have led to the attenuated variant 17D. This attenuated vaccine virus exists in 2 sub-
strains (17D-204 and 17DD) which share 99.9% sequence homology.
Yellow fever vaccine is recommended for people aged ≥9 months who are traveling to or living in areas at risk for yellow fever
virus transmission in South America and Africa.
Contraindicated in:
• Allergy to a vaccine component
• Age <6 months
• Symptomatic HIV infection or CD4+ T-lymphocytes <200/mm3 (<15% of total in children aged <6 years)
• Thymus disorder associated with abnormal immune function
• Primary immunodeficiencies
• Malignant neoplasms
• Transplantation
• Immunosuppressive and immunomodulatory therapies
Manufactured in Central research institute Kasauli – India
Vaccination valid after 10 days – for LIFE (as per revised WHO guidelines July 2016
Centers for vaccination: JJ hospital, BJ – Sasoon Pune, Airport health organization Mumbai
51. First identified in Uganda in 1947 in monkeys through a network that monitored yellow fever. It was later identified in
humans in 1952 in Uganda and the United Republic of Tanzania.
Outbreaks of Zika virus disease have been recorded in Africa, the Americas, Asia and the Pacific. From the 1960s to 1980s,
human infections were found across Africa and Asia, typically accompanied by mild illness.
The first large outbreak of disease caused by Zika infection was reported from the Island of Yap (Federated States of
Micronesia) in 2007.
In July 2015 Brazil reported an association between Zika virus infection and Guillain-Barré syndrome. In October 2015 Brazil
reported an association between Zika virus infection and microcephaly.
Vector: Aedes species
ZIKA VIRUS HISTORY & SPREAD
53. On 15 May 2017, the Ministry of Health and Family Welfare-Government of India (MoHFW) reported three laboratory-confirmed
cases of Zika virus disease in Bapunagar area, Ahmedabad District, Gujarat, State, India.
The routine laboratory surveillance detected a laboratory-confirmed case of Zika virus disease through RT-PCR test at B.J.
Medical College, Ahmedabad, Gujarat. The etiology of this case has been further confirmed through a positive RT-PCR test and
sequencing at the national reference laboratory, National Institute of Virology (NIV), Pune on 4 January 2017 (case 2, below).
Two additional cases (case 1 and case 3), have then been identified through the Acute Febrile Illness (AFI) and the Antenatal
clinic (ANC) surveillance. The cases are reported below in chronological order:
•Case 1**: A 34-year-old female, delivered a clinically well baby at BJMC in Ahmedabad on 9 November 2016. During her
hospital stay, she developed a low grade fever after delivery. No history of fever during pregnancy and no history of travel for the
past three months was reported. A sample from the patient was referred to the Viral Research & Diagnostic Laboratory (VRDL)
at the BJMC for dengue testing and thereafter found to be positive for Zika virus. She was discharged after one week (on 16
November 2016). The sample was re-confirmed as Zika virus positive by RT-PCR and sequencing at NIV, Pune.
•Case 2**: During the Antenatal clinic (ANC) surveillance between 6 and 12 January 2017, a total of 111 blood samples were
collected at BJMC. One sample from a 22-year-old pregnant female in her 37th week of pregnancy has been tested positive for
Zika virus disease.
•Case 3**: During the Acute Febrile Illness (AFI) surveillance between 10 to 16 February 2017*, a total of 93 blood samples were
collected at BJ Medical College (BJMC), Ahmedabad, Gujarat State. One sample from a 64-year-old male presenting with febrile
illness of 8 days’ duration (negative for dengue infection) was found to be positive for Zika virus at BJMC, Ahmedabad. This is
the first Zika positive case reported through AFI surveillance at BJMC, Ahmedabad, Gujarat State.
ZIKA VIRUS IN INDIA
54.
55. Zika infection in pregnancy
The constellation of neuropathologic
features ventriculomegaly, mineralized
neurons, and dystrophic calcification
with band-like subcortical distribution)
differs from features seen in other
common infections associated with
congenital abnormalities (e.g., TORCH)
Virus spread in the body
Virus was also detected in all major
organs like liver (Councilman bodies
and periportal lymphocytic infiltration),
lungs (interstitial lymphocytic
pneumonitis), and bladder
(lymphocytic cystitis)
NO specific treatment, No vaccine yet.
56. Zika virus is enveloped and icosahedral and has a non-segmented, single-stranded, 10 kilobase positive-sense RNA genome.
Size 40nm.
ZIKA VIRUS MORPHOLOGY
60. WEST NILE VIRUS – HISTORY & DISTRIBUTION
West Nile Virus was discovered in Uganda in 1937 and was first detected in North America in 1999
Area of distribution worldwide: Europe, the Middle East, Africa, India, Asia, Australia, and North America.
In India, antibodies against WNV were first detected in humans in Bombay in 1952. Virus activity has been reported in southern,
central, and western India. WNV has been isolated in India from Culex vishnui mosquitoes in Andhra Pradesh and Tamil Nadu,
from Cx. quinquefasciatus mosquitoes in Maharashtra, and from humans in Karnataka State
61. Virus family : Togaviridae
Virus genus : Alphavirus
Vector: Culex pipiens (Eastern United States, and urban and residential areas of the United States north of 36–39°N),
Culex tarsalis (Midwest and West), and Culex quinquefasciatus (Southeast) are the main vector species
WNV - EPIDEMIOLOGY & CYCLE
63. WNV - LAB DIAGNOSIS & PREVENTION
VACCINE
A vaccine for horses (ATCvet code: QI05AA10 (WHO)) based on killed viruses exists; some zoos have given this vaccine to their
birds, although its effectiveness is unknown.
65. Relatively less common overall and/or not yet seen in India
India is a potential receptor area for these virus infections to start manifesting
Most of these were listed as Weapons of Bioterrorism
Encephalitis group
Eastern, Western & Venezuelan
Equine encephalitis
St. Louis encephalitis
Californian “serogroup” encephalitis
Murray valley encephalitis
Rocio viral encephalitis
Arthralgia group
Spondweni virus
O’nyong nyong
Sindbis
Ross river
Mayaro
Oro pouche
RARER ARBOVIRUSES ACROSS THE WORLD
67. EASTERN, WESTERN & VENEZUELAN EQUINE ENCEPHALITIS
Equine : initially discovered and more commonly affects horses.
Of these WEE is a recombinant virus between two other alphaviruses, an ancestral Sindbis virus-like virus, and an
ancestral Eastern equine encephalitis virus-like virus.
Virus family : Togaviridae
Virus genus : Alphavirus
Vector:
Culex & Culista;
Bridge vectors include Aedes vexans, Coquillettidia perturbans, Ochlerotatus canadensis and Ochlerotatus sollicitans.
Changing patterns being observed based in climatic shifts and extent of rainfall
Area of distribution worldwide: Central and South Americas, Mexico, Colombia, Venezuela, and the United States.
USA average 7 EEE cases per year, lesser numbers for WEE and VEE except the outbreak of this disease which occurred on
Colombia in September 1995. This outbreak resulted in 14,156 human cases that were attributable to Venezuelan equine
encephalitis virus with 26 human deaths.
Proposed reasons: deforestation, heavy rains & change in vector to Aedes*
68. EEE, WEE & VEE – EPIDEMIOLOGY & DIAGNOSIS
Clinical features:
Mostly viral prodrome with rare encephalitis presentation – more likely & severe with EEE.
Diagnosis: CSF PCR, Serological antibodies
Vaccines : Available for horses, human vaccine still in progress – for VEE - vaccine containing the TC-83 strain is only used on
humans in military and laboratory positions that risk contracting the virus. The human vaccine can result in side effects and
does not fully immunize the patient.
70. ST. LOUIS ENCEPHALITIS VIRUS – HISTORY & DISTRIBUTION
The name of the virus goes back to 1933 when within five
weeks in autumn an encephalitis epidemic of explosive
proportions broke out in the vicinity of St. Louis, Missouri, and
the neighboring St. Louis County in USA with 1000 cases
reported.
The next & largest epidemic of SLEV neuro-invasive disease
ever recognized occurred in the United States in 1975, with
nearly 2,000 cases reported, primarily from the central states in
the Ohio-Mississippi River Basin
Area of distribution worldwide: USA, occasional cases in
Mexico & Columbia
During the last 5 decades, 10,000 cases were reported, with an
average of 102 cases reported annually (range 2-1,967)
71. Virus family : Flaviviridae
Virus genus : Flavivirus
Vector: Culex
ST. LOUIS ENCEPHALITIS VIRUS – EPIEMIOLOGY
72. SLEV - CLINICAL FEATURES & PREVENTION
Diagnosis: IgM serological tests
Vaccines :There are no vaccines or any other treatments specifically for Saint Louis encephalitis virus, although one study
showed that early use of interferon-alpha2b may decrease the severity of complications
Less than 1% of St. Louis encephalitis virus (SLEV) infections are clinically apparent and the vast majority of infections
remain undiagnosed.
The mortality rate of St. Louis encephalitis is 2-30%. This figure is higher in older patients.
Of persons who survive St. Louis encephalitis, 20% develop sequelae, including irritability, memory loss, various types of
movement disorders, or motor deficits. The medical literature also contains reports of syndrome of inappropriate
antidiuretic hormone secretion (SIADH) and hyponatremia in patients with St. Louis encephalitis.
74. CALIFORNIAN SEROGROUP ENCEPHALITIS
California encephalitis virus was discovered in Kern County, California and causes encephalitis in humans.
Only 3 cases were reported. but Since then, most cases of encephalitis have been associated with the La Crosse virus,
and California encephalitis is a rare cause of disease in the Western World.
The original California Encephalitis virus was isolated and put alongside fifteen other related viruses that are now
categorized as the "California serogroup".
La Crosse encephalitis was discovered in 1965, after the virus was isolated from stored brain and spinal tissue of a
child who died of an unknown infection in La Crosse, Wisconsin in 1960
La Crosse – most important cause of arboviral encephalitis in children in the USA
Significant viruses included in the California serogroup (CSG) (family Bunyaviridae, genus Orthobunyavirus) are the
mosquito borne pathogens Jamestown Canyon virus (JCV), snowshoe hare virus (SSHV), and La Crosse virus.
Approximately 75 cases reported per year
Area of distribution worldwide: USA and Southern Canada
75. Virus family : Bunyaviridae
Virus genus : Orthobunyavirus
Vector: Aedes triseriatus
Amplifying host: Squirrels & small mammals
Negative sense single stranded RNA virus 80nm size
Local replication at the skin site primary spread of virus
seeding of the reticuloendothelial system, mainly liver, spleen,
and lymph nodes ongoing replication of the virus
secondary spread seeding of the CNS.
The California encephalitis virus invades the CNS through either
the cerebral capillary endothelial cells or the choroid plexus.
CSG ENCEPHALITIS – EPIDEMIOLOGY & PATHOPHYSIOLOGY
76. CSG VIRUSES – CLINICAL FEATURES, DIAGNOSIS & PREVENTION
Incubation period: 3–7 days
• Early symptoms phase: 1–4 days - fever, chills, nausea, vomiting, headache, lethargy and abdominal pain
• Encephalitis phase: Fever, drowsiness, and lack of mental alertness and orientation, seizures in 50% of children
• Focal neurologic findings, like focal motor abnormalities and paralysis, irregular and abnormal reflexes in 20% of children
• Coma in10% of patients
• Recurrent unprovoked seizures - even after the illness has passed - develop in 20% of patients
• Adults: Infection is almost asymptomatic or only mild feverish illness.
• Mortality rate is less than 1% - most patients with encephalitis clinical symptoms recover completely.
• Up to 20% of patients develop behavioral problems or recurrent seizures
Diagnosis:
Serological IgM antibodies
Vaccines : still in development
78. MURRAY VALLEY ENCEPHALITIS
Murray Valley encephalitis virus (MVEV) (previously known as Australian encephalitis or Australian X disease) is the most
serious of the endemic arboviruses causing encephalitis in Australia. Six known large outbreaks of encephalitis in south-
eastern Australia in the 1900s, with the last comprising 58 cases in 1974.
In 2011, high-level MVEV activity occurred in south-eastern Australia for the first time since 1974, accompanied by unusually
heavy seasonal MVEV activity in northern Australia - resulted in 17 confirmed cases of MVEV disease across Australia.
(Record wet season rainfall was recorded in many areas of Australia in the summer and autumn of 2011 associated with significant flooding
and increased numbers of the mosquito vector and subsequent MVEV activity)
In contrast to outbreaks prior to 2000, the majority of cases were non-Aboriginal adults, and almost half (40%) of the cases
acquired MVEV outside their area of residence.
Sentinel chicken programs, where flocks of flavivirus-naïve chickens are kept specifically for regular testing for MVE infection,
are in place in most parts of Australia where MVEV activity has occurred, with the role of providing an early warning system
for MVEV activity
Virus family : Flaviviridae
Virus genus : Flavibunyavirus
Vector: Culex annulirostris.
79. Mild illness:
fever
headache
nausea
Vomiting
In about 1 in 1000 – serious encephalitis picture:
increasing confusion
headaches
drowsiness
Seizures
Diagnosis:
Serological antibodies
PCR
Vaccines : still in development
MURRAY VALLEY ENCEPHALITIS - CLINICAL FEATURES
81. ROCIO VIRAL ENCEPHALITIS
Rocio viral encephalitis was first observed in São Paulo State, Brazil, in 1975 and 1976, when the Rocio virus was responsible
for several epidemics of meningoencephalitis in coastal communities in southern São Paulo, Brazil. The outbreaks affected over
1,000 people and killed about 10% of those infected.
Virus family : Flaviviridae
Virus genus : Flavibunyavirus
Vector: Culex
Amplifying host: rufous-collared sparrow, Zonotrichia capensis
Area of distribution worldwide: Brazil
The disease progresses rapidly after onset, with patients dying within 5 days of symptoms first appearing. The disease first
presents with fever, headache, vomiting, and conjunctivitis, then progresses to neurological symptoms
(confusion, disorientation, etc.) and muscle weakness; about one-third of cases enter a coma, and a third of those patients die.
Diagnosis: Serological antibodies, PCR
Vaccines : still in development
84. SPONDWENI VIRUS
Spondweni virus (SPOV) is a part of the Spondweni serogroup which includes two species, Zika Virus (ZIKV) and the
Spondweni Virus (SPONV).
SPONV – especially the Chuku strain - is phylogenetically close to the ZIKV, it is commonly misdiagnosed as ZIKV along with
other viral illnesses
6 cases so far, rest not clear due to overlap of symptoms
Virus family : Flaviviridae
Virus genus : Flavibunyavirus
Vector: Aedes circumluteolus; Culex
Clinical features:
Mild presentation: Fever, headache, nausea, myalgia, greyish mucoid lining on the posterior pharynx, arthralgia, vertigo,
conjunctivitis, maculopapular and pruritic rash, epistaxis, photophobia, vomiting
Rare cases: disorientation
Area of distribution worldwide: Sub-Saharan Africa
Diagnosis: PCR * to avoid misdiagnosis
Vaccines : still in development
86. O’ NYONG NYONG VIRUS
The O’ Nyong’ Nyong virus (ONNV) was first isolated by researchers at the Uganda Virus Research Institute.
O’nyong-nyong virus (ONNV), derived from the description by the Acholi tribe, meaning ‘joint breaker’, was first isolated
during a 1959–1962 epidemic affecting 2 million people in Uganda, Kenya, Tanzania, Mozambique, Malawi and Senegal.
Another major outbreak involving an estimated 1 million cases occurred in 1996 in Uganda and northern Tanzania.
Attack rates are generally high and all age groups are affected during ONNV epidemics.
Virus family : Togaviridae
Virus genus : Alphaavirus
Vector: Anopheles
Area of distribution worldwide:
Uganda Kenya, Tanzania, Zaire (Democratic Republic of the Congo), Malawi and Mozambique
Common symptoms of infection with the virus are polyarthritis, rash and fever. Other symptoms include eye pain, chest
pain, lymphadenitis and lethargy. The disease is self-limiting.
Diagnosis: PCR, Serology
Vaccines : still in development
88. SINDBIS VIRUS
Sindbis virus (SINV) is a member of the Togaviridae family, in the alphavirus subfamily. The virus was first isolated in 1952
in Cairo, Egypt.
The clinical disease caused by SINV infection is known as Pogosta disease (Finland), Ockelbo disease (Sweden), and
Karelian fever (Russia).
Area of distribution worldwide: South and East Africa, Egypt, Israel, Philippines and parts of Australia.
Virus family : Togaviridae
Virus genus : Alphaavirus
Vector: Culex; Culiseta
Maculopapular and often itchy exanthema over the trunk and limbs, mild fever, and joint symptoms, particularly in wrists,
hips, knees, and ankles, are the hallmarks of acute SINV infection, sometimes accompanied by nausea, general malaise,
headache, and muscle pain
Diagnosis: Serological antibodies. No PCR yet.
Vaccines : still in development
89. Most Culiseta species are cold-adapted, and only
occur in warmer climates during the colder parts of
the year or at higher elevations where
temperatures are lower.
Species found in Southern California are larger
than most mosquitoes species, specifically
Cs. inornata, Cs. particeps and Cs. incidens.
Feed on several vertebrate species encompassing
birds, livestock, rodents, reptiles and humans.
Culiseta species are found throughout the world,
except in South America.
CULISETA SPECIES - MOSQUITO
91. ROSS RIVER VIRUS
Ross River virus (RRV) is responsible for a non-lethal but debilitating tropical disease known as Ross River fever, previously
termed "epidemic polyarthritis”. The Ross River virus is named after the Ross River in Townsville, which is the place where it
was first identified.
Ross River fever is the most common mosquito borne disease in Australia, and nearly 5000 people are reported to be
infected with the virus each year.
Virus family : Togaviridae
Virus genus : Alphaavirus
Vector: Culex, Aedes
Reservoir
Area of distribution worldwide: Australia, Papua New Guinea and other islands in the South Pacific.
Diagnosis: PCR
Vaccines : still in development
92. RRV – HOSTS, RESERVOIRS & VECTORS
Kangaroo – the National Animal – proven to the most important reservoir
Widest variety of reservoir, hosts and vector – serious epidemic potential
94. MAYARO VIRUS
MAYV, produces a dengue-like illness accompanied by long-lasting arthralgia and is only known to circulate in tropical South
America.
1. An outbreak in Chuquisaca Department, Bolivia, involving twelve persons, was reported in May 2007.
2. In January 2010, a French tourist developed high-grade fever and severe joint pain manifestations following a 15-day trip in
the Amazon basin, Brazil, and was diagnosed with MAYV infection in France.
3. Transported into the United States by two visitors infected in eastern Peru and into the Netherlands by a couple infected
while vacationing in Surinam.
4. The first outbreak of Mayaro virus disease in humans in Venezuela was reported in early June 2010, with 69 cases diagnosed
in Ospino, Portuguesa state, and an additional two in San Fernando de Apure, Apure state, on 7 June 2010, for a total of 71
reported cases as of 8 June.
5. A single case of Mayaro virus in a child in Haiti in 2015 has been confirmed.
Virus family : Togaviridae
Virus genus : Alphaavirus
Vector: Hemagoggus*, Aedes also likely
*Metallic sheen - Also can transmit yellow fever
Diagnosis: serological antibodies, PCR
Vaccines : still in development
96. ORO POUCHE VIRUS
The Oropouche virus (OROV) is one of the most common orthobunyaviruses and is considered a public health threat in
tropical and subtropical areas of Central and South America, with over half million infected people as of 2005 in Brazil.
Large epidemics are common and very swift, one of the earliest largest having occurred at the city of Belém, in the
Brazilian Amazon state of Pará, with 11,000 recorded cases.
In the Brazilian Amazon, Oropouche is the second most frequent viral disease, after dengue fever. Several epidemics have
generated more than 263,000 cases, of which 130,000 alone occurred in the period from 1978 to 1980.
Virus family : Bunyaviridae
Virus genus : Orthobunyavirus
Vector: Ochlerotatus, Aedes, Culex
Diagnosis: PCR, Serological tests
Vaccines : still in development
Likely to cause Encephalitis – cases under study
OROV has been used extensively in testing with Hela cells to study the mechanisms of apoptosis induced by the virus.
It was found that OROV causes apoptosis by DNA fragmentation.
97. VECTOR CONTROL MEASURES
Monitoring mosquito populations
Mechanical traps use a fan to blow adult mosquitoes into a collection bag that is taken back to the laboratory for analysis of
catch. The mechanical traps use visual cues (light, black/white contrasts) or chemical attractants that are normally given off by
mosquito hosts (e.g., carbon dioxide, ammonia, lactic acid, octenol) to attract adult female mosquitoes.
Source reduction : Eliminating breeding grounds – Dengue – artificial collections of water*
Biological control or "biocontrol" is the use of natural enemies to manage mosquito populations; Direct introduction of parasites,
pathogens and predators to target mosquitoes:
Predatory fish that feed on mosquito larvae such as mosquitofish (Gambusia affinis) and some cyprinids (carps and minnows)
and killifish. Tilapia also consume mosquito larvae.
Direct introduction of tilapia and mosquitofish into ecosystems around the world have had disastrous consequences.
Controlled system via aquaponics to be used
Larvicidal measures: DDT, fogging of all areas known as breeding sites and especially in peak seasons like rains.
Personal protective equipment: Repellant sprays, Mosquito nets, Long sleeved clothes
98.
99. EXTINCTION OF MOSQUITOES ?
Specicide-Proposed Extinction of mosquitoes
Biologist Olivia Judson has advocated the deliberate extinction of certain disease-carrying mosquito species. In a
September 25, 2003 New York Times article, she advocated "specicide" of thirty mosquito species by introducing a
genetic element which can insert itself into another crucial gene, to create recessive "knockout genes".
The debate continues…..
100. NEWER ADVANCES/ AREAS OF RESEARCH
Mast cell inhibitors in dengue
Ketotifen under research for treating/preventing vascular leakage.
Macrophage migration inhibitory factor
Macrophage migration inhibitory factor (MIF or MMIF), also known as glycosylation-inhibiting factor (GIF), L-
dopachrome isomerase, or phenylpyruvate tautomerase is a protein that in humans is encoded by
the MIF gene. MIF is an important regulator of innate immunity.
Syndromic Approach to Arboviral Diagnostics for Global Travelers as a Basis for
Infectious Disease Surveillance
Travel history mapped to set of diagnostic tests in suspected case of arboviral diseases
101.
102. WHO – Arboviral diseases – entire http://www.who.int/denguecontrol/arbo-viral/en/
Center for Disease Control - Division of Vector-Borne Diseases (DVBD) National Center for Emerging Zoonotic diseases
https://www.cdc.gov/ncezid/dvbd/index.html
Emerging and re-emerging arboviral diseases in Southeast Asia A.P. Dash1 , Rajesh Bhatia1 , Temmy Sunyoto1 & D.T. Mourya
Wang, Seok Mui, and Shamala Devi Sekaran. “Early Diagnosis of Dengue Infection Using a Commercial Dengue Duo Rapid Test Kit for the
Detection of NS1, IGM, and IGG.” The American Journal of Tropical Medicine and Hygiene83.3 (2010): 690–695. PMC. Web. 27 Dec. 2017.
Fry, Scott R. et al. “The Diagnostic Sensitivity of Dengue Rapid Test Assays Is Significantly Enhanced by Using a Combined Antigen and
Antibody Testing Approach.” Ed. Maria G. Guzman. PLoS Neglected Tropical Diseases 5.6 (2011): e1199. PMC. Web. 27 Dec. 2017.
Evaluation of a Commercial SD Dengue Virus NS1 Antigen Capture Enzyme-Linked Immunosorbent Assay Kit for Early Diagnosis of Dengue
Virus Infection▿ Seok Mui Wang and Shamala Devi Sekaran*
Comparison of IgM capture ELISA with a commercial rapid immunochromatographic card test & IgM microwell ELISA for the detection of
antibodies to dengue viruses.
Sathish N1, Manayani DJ, Shankar V, Abraham M, Nithyanandam G, Sridharan G.
Avirutnan P, Matangkasombut P. Unmasking the role of mast cells in dengue. eLife. 2013;2:e00767. doi:10.7554/eLife.00767.
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