Chair of Medical Biology, Microbiology, Virology, and Immunology

Lecturer Prof. S.I. Klymnyuk

Arboviruses

Arthropod-Borne (Arbo) Viral Diseases

The arthropod-borne viruses, or arboviruses, are a group of infectious agents that are transmitted by blood-sucking arthropods from one vertebrate host to another. They can multiply in the tissues of the arthropod without evidence of disease or damage. The vector acquires a lifelong infection through the ingestion of blood from a viremic vertebrate. All arboviruses have an RNA genome, and most have a lipid-containing envelope and consequently are inactivated by ether or sodium deoxycholate.

Current taxonomic status of some arboviruses

Current Taxonomic Classification

Arbovirus Members

Togaviridae

Genus Alphavirus

Aura, Chikungunya, eastern equine encephalitis, Getah, Maygro, Mucambo, Ndumu, O'Nyong-nyong, Ross River, Semliki Forest, Sindbis, Venezuelan and Western equine encephalitis

Flaviviridae

Genus Flavivirus

Dengue, Israel turkey meningoencephalitis, Japanese B encephalitis, Kunjin, Kyasanur Forest disease, Murray Valley encephalitis, Ntaya. Omsk hemorrhagic fever. Powassan, St. Louis encephalitis, tick-borne encephalitis, Uganda S, Wesselsbron, West Nile fever, yellow fever,

Current taxonomic status of some arbovirusesCurrent Taxonomic

ClassificationArbovirus Members

Bunyaviridae

Genus Bunyavirus

Bunyamwera, Bwamba, C, California, Capim, Guama, Koongol, Patois, Simbu, and Tete; 7 unassigned viruses

Genus Uukuniemi Uukuniemi, Anopheles A, Anopheles B, Bakau, Crimean-Congo hemorrhagic fever, Kaisodi, Mapputta, Nairobi sheep disease, Phlebotomus fever, and Turlock; 8 unassigned viruses

Reoviridae

Genus Orbivirus

African horse sickness, bluetongue, and Colorado tick fever viruses

Rhabdoviridae Genus Vesiculovirus

Cocal, Hart Park, Kern Canyon, and vesicular stomatitis viruses

Current taxonomic status of some arboviruses

Current Taxonomic Classification

Arbovirus Members

Arenaviridae Genus Arenavirus

Junin, Lassa, Machupo, and Pichinde viruses

Nodaviridae Nodamura virus

Sindbis virus

Structures of Alphaviruses

Principal medically important alphaviruses

Virus Antigenic Clinical

Syndrome

Vector Host Distribution

Eastern equine

encephalitis

Encephalitis (EEE)

Mosquito Birds Americas

Western equine

encephalitis

Encephalitis (WEE)

Mosquito Birds North America

Venezuelan equine

encephalitis

Febrile illness,

encephalitis (VEE)

Mosquito Rodents, horses

Americas

Virus Antigenic Clinical

Syndrome

Vector Host Distribution

Chikunguny (CHIK) Africa,

Febrile illness, rash,

arthralgia

Mosquito Primates, humans

India, Southeast

Asia

O’nyong-nyong (ONN)

Febrile illness, rash,

arthralgia

Mosquito Primates Africa

Sindbisc (SIN)

Febrile illness, rash,

arthralgia

Mosquito Birds Nothern Europe,

Africa, Asia, Australia

Semliki Forest

Febrile illness, rare encephalitis

Mosquito Birds Africa

The scheme of Alphavirus replication

Pathogenesis of alphaviruses

FIGURE Alphavirus transmission. Virus abbreviations: Chik, chickungunya; RR, Ross River; May, Mayaro; ONN, O'nyong-nyong; SIN, Sindbis; EEE, eastern equine encephalitis; VEE, Venezuelan equine encephalitis.

Rubella (German measles) is a common mild disease characterized by a rash. It affects children and adolescents worldwide and can also affect young adults. When rubella virus infects susceptible women early in pregnancy, it may be transmitted to the fetus and may cause birth defects. Therefore, accurate diagnosis is critical in pregnancy. The rubella virus is a member of the genus Rubivirus in the family Togaviridae.

Rubellaviruses

Rubella virus

Rash

FIGURE. Clinical findings, virus shedding, and serologic response in postnatally acquired rubella.

Abnormalities Associated with Congenital Rubella Syndrome

Type of defects Examples

Ocular defects Cataracts

Microphthalmia

Glaucoma

Retinitis

Heart defects Patent ductus arteriosus

Atrial septal defect

Ventricular septal defect

Peripheral pulmonic artery stenosis

Hearing impairment Sensorineural deafness

Abnormalities Associated with Congenital Rubella Syndrome

Type of defects Examples

Central nervous system Mental retardation

Meningoencephalitis

Progressive rubella panencephalitis (rare)

Microcephaly

Other Growth retardation

Radiolucent borne disease

Hepatosplenomegaly

Hemathologic abnormalities:

Thrombocytopenia, purpura

Pneumonitis

Endocrine dysfunction:

Insulin dependent diabetes mellitus, thyroididtis

Cataract

Glaucoma

Structure of Flaviviruses

Flavivirus

Tick-born encephalitis virus

Tick-born encephalitis virus

Figure 5. The scheme of Flavivirus replication

Virions are formed in perinuclear regions of the cytoplasm in association with Golgi or smooth membranes (Figure 6). Virions appear within cytoplasmic vacuoles and appear to exit the cell as vacuoles fuse with the plasma membrane. Unlike alphaviruses, no evidence of budding has been seen in flavivirus-infected cells, and the mechanisms of virion assembly and release remain obscure.

FIGURE 6. Morphogenesis of flaviviruses

Virus Antigenic Clinical

Syndrome

Vector Host Distribution

Dengue (DEN)

Febrile illness, rash, hemorrhagic fever, shock syndrome

Mosquito Humans Tropics, worldwide

Yellow fever (YF)

Hemorrhagic fever,

hepatitis

Mosquito Primates, humans

Africa, South America

St. Louis encephalitis (SLE)

Encephalitis Mosquito Birds Americas

Principal medically important flaviviruses

Virus Antigenic Clinical

Syndrome

Vector Host Distribution

Japanese encephalitis

(JE)

Encephalitis Mosquito Pigs, birds India, China, Japan,

South-East Asia

West Nile Febrile illness

Mosquito Birds Africa, Middle East,

Europe

Tick-borne encephalitis (TBE)

Encephalitis Tick Rodent Europa, Asia

Principal medically important flaviviruses

Virus Antigenic Clinical

Syndrome

Vector Host Distribution

Omsk hemorrhagic

fever

Hemorrhagic fever

Tick Muskrats Siberia

Kyasanur Forest disease (KFD)

Hemorrhagic fever

Tick Rodents India primates

Principal medically important flaviviruses

Human infection with both mosquito-borne and tick-borne flaviviruses is initiated by deposition of virus through the skin via the saliva of an infected arthropod (Fig 7).

Figure 7. Pathogenesis of flaviviruses.

Tick

Yellow fever virus

Yellow fever

Dengue fever virus

Dengue fever

Bunyaviridae is a family of arthropod-borne or rodent-borne, spherical, enveloped RNA viruses. Bunyaviruses are responsible for a number of febrile diseases in humans and other vertebrates. They have either a rodent host or an arthropod vector and a vertebrate host.

Rift Valley Fever virus

Genus and Group

Virus Disease Vector Distribution

Bunyavirus

Anopheles A Tacaiuma Fever Mosquito South America

Bunyamwera Bunyamwera Fever Mosquito Africa

Germiston Fever Africa

Bwamba Bwamba Fever , Rash

Mosquito Africa

C Apeu Fever Mosquito South America

Human diseases Caused by Viruses of the Family Bunyaviridae

Human diseases Caused by Viruses of the Family Bunyaviridae

Genus and Group

Virus Disease Vector Distribution

Bunyavirus

California California encephalitis

Encepha-litis

Mosquito North America

Snowshoe hare

Encepha-litis

Mosquito North America,

Asia

Tahyna Fever Mosquito Europe

Simbu Shuni Fever Mosquito Africa, Asia

Human diseases Caused by Viruses of the Family Bunyaviridae

Genus and Group

Virus Disease Vector Distribution

Phlebovirus

Phlebovirus fever

Alenquer Fever Unknown South America

Naples Fever Sand fly Europe, Asia, Africa

Rift Valley Fever

Fever, encephalitis, hemorrhagic

fever, blindness

Mosquito Africa

Sicilian Fever Sand fly Europe, Africa, Asia

Human diseases Caused by Viruses of the Family Bunyaviridae

Genus and Group

Virus Disease Vector Distribution

Nairovirus

Crimean-Congo

Crimean-Congo

hemorrhagic fever

Hemorrhagic fever

Tick Africa, Asia

Nairobi sheep disease

Nairobi sheep disease

Fever Tick Africa, Asia

Human diseases Caused by Viruses of the Family Bunyaviridae

Genus and Group

Virus Disease Vector Distribution

Hantavirus

Hataan Hantaan HFRS Rodent Asia

Puumala HFRS Rodent Asia

Sequl HFRS Rodent Asia, Europe

Human diseases Caused by Viruses of the Family Bunyaviridae

Genus and Group

Virus Disease Vector Distribution

Genus unassigned

Bangui Fever, rash Unknown Africa

Bhanja Fever, encephalitis

Tick Africa, Europa, Asia

Issk-kul Fever Tick Asia

Kasokero Fever Unknown Africa

Nyando Fever Mosquito Africa

Tataguine Fever Mosquito Africa

Wanowrie Fever, hemorrhage

Tick Middle East, Asia

FIGURE 3. Pathogenesis of bunyavirus infections. Humans are dead-end hosts of most bunyaviruses; however, the blood of Crimean-Congo hemorrhagic fever patients may be highly infectious.

FIGURE 5. La Crosse encephalitis transmission cycle

Signs of Crimean-Congo Hemorrhagic Fever

Clinics of Hataan virus infection