ARBOVIRUSES

@ Arbovirus means “arthropod-borne virus

@ Transmitted by: * Arthropodes: female mosquito's and female ticks

* Mother tick transmit virus to her offspring.

* In yellow fever and dengue fever humans transmit the virus.

@ They are more than 400 arboviruses.

PROPERTIES@ Classified into four families: * Togavirus * Flavivirus * Bunyavirus * Reovirus

@ Togaviruses: Toga = cloak

* Icosahedral capsid, enveloped, single-stranded RNA virus

* Divided into two genera:1.Alphaviruses 2.Rubiviruses (Female tick)

@ Flaviviruses: Flavi = yellow

* Icosahedral capsid, enveloped, single-stranded RNA virus

@ Bunyaviruses: Bunia = town in Africa

* Helical capsid, enveloped, segmented

RNA virus

@ Arbovirus infection results only in Man.

@ It does not occur in either arthropod or other animals

Arbovirus Diseases in Sudan:

@ Yellow fever,@ Dengue fever@ Rift Valley fever

Arbovirus Diseases outside Sudan:

@ Eastern equine encephalitis@ Western equine encephalitis@ St. Louis encephalitis@ California encephalitis@ Japanese encephalitis@ Colorado tick fever

YELLOW FEVER VIRUS

Symptoms: @ Jaundice, Fever, Headache,

@ Photophobia, Sweating, haemorrhages

@ Hematemesis, Shock

Yellow fever

@ Yellow fever has two cycles: (1) Jungle yellow fever: Found in monkeys in the forest, transmitted to Man by mosquitoes (2) Urban yellow fever: infects Man , transmitted by the mosquitoes

Lab.Diagnosis of Yellow Fever:

@ Specimens: blood, throat swab, CSF

@ Inoculation of: (i) Suckling mice (ii) Cell culture (iii) Mosquito larvae.

@ Detect IgM antibody by: * ELISA * Haemagglutinatin–inhibition test.

Yellow Fever Vaccine:

@ It is a live attenuated vaccine, prepared from 17D yellow fever strain

@ Administered in one dose by a subcutaneous injection.

@ Protection lasts for 10 years.

DENGUE VIRUS

Symptoms:

@ Fever, malaise, cough, headache.

@ Pains in muscles and joints

@ Enlarged lymph nodes

@ Skin rash

@ Haemorrhage in GIT and shock

@ Lab. Diagnosis of dengue fever is similar to that of yellow fever

@ Dengue virus is transmitted by Aedes aegypti mosquito

@ It is transmitted from Man to Man . No animal is involved.

@ No vaccine is available.

@ Control is by destroying mosquitoes.

Rift Valley Fever Virus

@ It is a zoonotic disease.

@ Man is infected by contact with sheep & cattle; and by mosquito

Symptoms:

@ Fever, vomiting, haemorrhages

Lab. diagnosis of Rift Valley Fever virus:

@ Similar to that of yellow fever