This document is a group assignment on veterinary systemic virology prepared by 10 students and submitted to their professor. It discusses the Reoviridae family of viruses, including their general characteristics such as being non-enveloped with segmented double-stranded RNA. It summarizes the main genera within Reoviridae - Orthoreovirus, Rotavirus, and Orbivirus. For each genus, it provides 1-2 examples of diseases they cause. The document also discusses specific viruses like Bluetongue virus and African horse sickness virus in more detail, covering their transmission, pathogenesis, clinical signs, diagnosis and control.

1. Veterinary systemic virology
Group Assignment + Presentation
Prepared by:
① Ayenew wudie___________________________________0514/13
② Badada Halake__________________________________0533/13
③ Bayu Mamo_____________________________________0557/13
④ Bodena Kumela_________________________________ 0724/13
⑤ Cherinet Fanta______________________________ ____0748/13
⑥ Delu
Ufaisa______________________________________0832/13
⑦ Derese Hailemeskel _____________________________0848/13
⑧ Derese Tekilu____________________________________0850/13
⑨ Dessalegn Ermiyas______________________________0860/13
⑩ Aychew Molla ___________________________________0511/13
Submitted to: Dr. Abdallahi A. Submission date: June 14/2023
College of veterinary medicine DVM
3rd
Year

2. REOVIRIDAE

3. 
 Respiratory enteric orphan virus( Reo)
 "Orphan virus" = without any associated disease (some)

Reoviridae
 Non-enveloped with double or triple layered capsid & icoshedral
structure 60-80 nm in diameter
 Segmented (10-12 segments) double- stranded RNA.

 Replicate in cytoplasm with intracytoplasmic inclusion bodies.

 Genetic reassortment readily takes place.
 Resistant to heat, organic solvents and non-ionic detergents.
 2 morphological forms:
General characters:
1. 'Spiked' = turret shaped projections
2. 'Smooth' = spherical

5. Rotavirus particles as they appear in an electron
micrograph and a diagrammatic representation

6. ① Orthoreovirus: cause arthritis & tenocynovitis in poultry.
②
② Rotavirus : cause enteritis in neonatal farm animals.
③
③ Orbivirus: Arthropods- borne infections (Arbo), cause:
④ African horse sickness in horses, Bluetongue disease in sheep ,
and in other domestic & wild
⑤ ruminants.
⑥ Colti virus (Colorado tick fever virus): primarily infect rodents
and human but occasionally cause clinical disease in domestic
animals
Generas of Reoviridae :

8.  Orthoreoviruses and rotaviruses are stable over a wide
range of pH values while orbiviruses lose infectivity at
low pH value
 Blue tongue virus
 African horse sickness virus
 Epizootic haemorrhagic disease virus
 Ibaraki virus
 Equine encephalosis virus
 Palyam virus
Genus: Orbivirus

9.  non-contagious viral disease of sheep and other domestic and
wild ruminants.
 transmitted principally by biting midges (Culicoides spp).
 caused by serotypes of bluetongue virus (BTV) in the genus
orbivirus of the family Reoviridae.
 Twenty four serotypes of the BTV have been described.
Blue tongue

10.  transmitted by Culicoides imicola in Africa and Asia.
 Venereal transmission through the semen of ram and bull has
been reported.
 Can also be transmitted by embryo transfer.
 Blue tongue is of great significance in sheep and deer.
 Cattle are considered to be important reservoir of the virus.
Transmission:

11.  After experimental infection, the virus replicates initially in
regional lymph nodes.
 It is then carried in blood or lymph to other lymphoid tissues,
lungs and spleen where further replication takes place.
 Virus localizes and multiplies in the endothelium of small blood
vessels producing vascular damage with stasis, exudation and
tissue hypoxia.
 The initiation and development of surface lesions in areas of
tissue hypoxia relate to minor trauma and may be complicated
by secondary bacterial infection.
 Lesions are particularly evident in the oral cavity, around the
mouth and on the coronet of the hoof.
Pathogenesis and pathology

12.  In the bloodstream, the virus is highly cell - associated,
particularly with erythrocytes.
 Infectious virus can be detected for 35 to 60 days after
infection.
Cont....

13.  are diverse and varied.
 There may be:
Clinical signs:
 fever
 depression
 vascular congestion of the lips and muzzle,
 oedema of lips, face, eyelids and ear
 erosion and ulceration of oral mucosa
 excessive salivation and
 watery nasal discharges which later becomes
mucopurulent
 swollen and cyanotic tongue,
 lameness from coronotis and
 laminitis ( inflammation of laminae)
 abortion and
 mortality of up to 30%.

15.  Clinical signs and postmortem findings are suggestive
 Laboratory confirmation requires isolation and identification
of the virus or demonstration of BTV-specific antibodies
 Samples: unclotted blood from febrile animals or fresh spleen
and lymph node collected at post mortem
 Virus isolation in embryonated egg inoculated intravenously
 Antigen detection by ELISA
 Serology: CFT, AGID, Indirect IF, and Indirect ELISA
 Neutralization test and HI test
 PCR
Diagnosis

16.  Vector control
 Live attenuated vaccine for protection against virulent virus
of homologous serotype
 Polyvalent vaccine in regions where more than one
serotype is prevalent
 Live attenuated vaccine may be teratogenic when used in
pregnant animals during the first half of gestation
 Live attenuated vaccine virus may revert to virulence
 Killed adjuvanted vaccine can induce protection but
requires booster dose. It is more expensive to produce.
Control

17.  non-contagious disease of horse, mules and donkeys.
 Aetiology: African horse sickness virus (AHSV), an orbivirus.
 The AHS subgroup is made up of nine serotypes of AHSV and
they are distinguishable by neutralization tests.
 AHS is endemic in subtropical and tropical Africa.
 Outbreak have also been reported in some parts of Asia
(Middle East, India, Pakistan)=serotype 9 and Europe (Spain
and Portugal)=serotype 4
African horse sickness

18.  transmitted by haematophagous insects.
 major vector is Culicoides imicola (a species of Afro-Asian midge).
 C.imicola once infected remains infected for life.
 warm climate of Africa supports the multiplication of the midge
and endemic disease occurs only in regions where C. imicola is
constantly present.
 Outbreaks occurs majorly during the warm humid season
(summer).
 may be isolated from clinically normal maintenance hosts such as
the zebra and African donkey.
Transmission

19.  The primary sites of viral replication are believed to be
regional LNs, spleen and lungs.
 Viraemia persists throughout the febrile period, typically 4
to 8 days.
 In zebras and donkeys, viraemia may last up to 4 weeks.
 Endothelial cells are important sites of secondary viral
replication, resulting in increased vascular permeability,
oedema, haemorrhage and intravascular coagulation.
 Post - mortem findings include diffuse pulmonary oedema,
hydrothorax, ascites and hydropericardium.
Pathogenesis and pathology

20. ① A peracute pulmonary form characterized by depression, nasal
discharge with rapid progression to severe respiratory distress.
Mortality is close to 100%
② a subacute cardiac form manifesting as conjunctivitis, abdominal
pain and progressive dyspnoea
③ subacute oedematous swelling of the head and mouth are most
obvious in the supraorbital fossae, palpebral conjuctiva and
intermandibular space.
④ Mortality rate is up to 70%.
⑤ A combination of pulmonary and cardiac features (mixed form).
⑥ a mild or subclassical form termed horse sickness fever observed
in zebra and donkeys.
Four clinical forms of AHS are recognized:
Clinical signs

21. Peracute pulmonary form Subacute cardiac form

22.  characteristic clinical signs and postmortem findings
 samples: blood, lymph nodes, spleen
 virus isolation in embryonated eggs or cell culture as well as
intracerebral inoculation of newborn mice
 identification of isolated virus by immunoflourescence and
typing by virus neutralization with monovalent antiserum or
competitive ELISA
 reverse-transcriptase (RT)- PCR can be used for detection of
viral RNA.
 serological test by CFT, AGID, ELISA and serum neutralization
tests.
Diagnosis

23.  vector control, quarantine and vaccination
 attenuated vaccines both monovalent and polyvalent
containing up to four serotypes are available, vaccines do
not prevent viraemia.
 Vaccine virus can revert to virulence and be transmitted by
vectors.
 Vaccinated animals can not be differentiated serologically
from those with foal infection.
 inactivated vaccines based on serotype 4 are effective in
preventing both clinical disease and viraemia.
 a polyvalent vaccine must be used if there is a risk of
exposure to different serotypes
Control

24.  Veterinary microbiology and microbial disease, 2nd
edition.P J Quin ,B K Markey, F C Leonard, E S Fitz
patrick, S Fanning , P J Hartigan. Ch. 69 P. (635-643)
,Reoviridae.
References

25. THANK YOU!!