Emerging diseases of sheep and goat with reference to BT

1. Dept. of Veterinary Preventive Medicine
COVAS, Parbhani
Guided By:
Dr. S.U. Digraskar

2. Contents
 Emerging diseases of sheep & goat
 Economic importance
 Blue Tongue Virus
 Epidemiology
 Pathogenesis
 Clinical findings
 Diagnosis
 Treatment
 Control
 Conclusion

3. Emerging Diseases
 Blue tongue
 Peste des Petits Ruminants
 Caprine Arthritis-Encephalitis
 Malignant Catarrhal Fever
 Ehrlichiosis

4. Economic Importance
Population Sheep Goat ( Fig. in Mill)
 India 65.07 135.17
 MS 2.5 8.4
 Presence of disease can limit
 Direct loss – animal loss, abortion, treatment control
 Trade and export
 Development of intensive livestock production
 The loss due to mortality is high to an extent of 85 per
cent

5. Blue Tongue
 Syn: Sore muzzle, Pseudo FMD
 Non contagious
 Insect borne viral disease
 Primary host is sheep
 Other animals – goat, cattle, camel, deer
 OIE disease A

6. Blue Tongue Virus
 Family – Reoviridae
 Subfamily-Sedoreovirinae
 Genus – Orbivirus
 The viral genome consists of 10 DS-RNA segments
which encode for seven structural (VP1-VP7) and 4
non structural (NS1-NS3/3A) proteins
 Segments 2 and 6 encode for the protein VP2 and VP5
which represent the outer capsid
 Segments 3 and 7 encode for protein VP7 and VP3
which form the inner capsid

7. Viral Structure

8.  VP2: is different in each serotype and identifies the
BTV serotypes
 VP7: is similar to all BTV serotypes and distinguishes
BTV as a serogroup

9. Properties
 Virus particle is spherical & about 50 nm in diameter
with 32 capsomers
 The capsid is double layered
 The genome is of 10 segments ds RNA
 The capsid contains four major and three minor
polypeptides

10.  BTV is resistant :
 at pH ranging between 6 and 8
 at room temperature
 in the blood at 20C
 at –70C
 To ether & chloroform
 BTV is inactivated:
 at –20C
 at 50C for 3 hours
 at 60C for 15 min.
 by β-propiolactone
 by all most common disinfectants
 by UV and gamma rays
 Below pH-6

11.  Sensitive to
 Acid
 3% sodium hydroxide solution
 organic iodides

12. Epidemiology
 Occurance – all around the world
 Morbidity and case fatality
 Morbidity- 50- 75%; Mortality-0 to 50%

13. Method of Transmission
 Culicoids spp. (principal biological vector)
 Other vectors
 Overwintering
 Transplacental infection
 Veneral transmission
 Oral transmission

14. Culicoides spp
 Of over 1,400 species present worldwide,
 at least 39 have been reported to occur in India
 Midges
 South India
 Culiciodes brevitarsis
 Culicoides imicola
 North India
 Culicoides oxistoma
 Culicoides monocoli

15. Vector Breeding places
 Manure pits
 Biogas slurry waste
 Incessant rain in rainy season
 Wind based movement of midges

16. Risk Factors
 Pathogen - strains
 Host – immunity, animal
 Vector – climate

17. Serotypes reported in India
 Through Virus Isolation (11)
 1,2,3,4,8,9,15,16,17,18,23
 Through detection of Neutralising antibodies(11)
 5,6,7,10,11,12,13,14,15, 19,20
 RT- PCR
 BTV 1 -24

18. Why endemic in India?
 24 serotypes reported
 Clinical signs not reported in Goat, Cattle, Buffalo and
deer RESERVOIR??
 Seroprevalence in Camels, Deer and Elephant
(Prasad et.al,1992)
 Vaccines – Not very good have Poor immunogenicity

19. Periodic Hyper Endemicities are
associated with
 Monsoon
 Poor flock nutrition
 High parasitic burden
 Lack of affordable veterinary care
 Sheep rearing in poorest areas in India as major source
of income
 Poor immunogenicity of the inactivated vaccines

20. Pathogenesis
Viraemia
Local Lymph Nodes
Bite of Vector
Other LN , spleen
and bone marrow
1st Multiplication
2nd Multiplication
Endothelial cells Monocytes &
Macrophages
Tissues of fetus
• Viremia is detected by day 3

21. Clinical Findings
 Incubation period: 5-20 days
 Fever
 Depression
 Salivation
 Facial swelling
 Dyspnea
 Panting
 Nasal discharge
 Hyperemia of muzzle, lips, ears

22.  Oral erosions and ulcerations
 Tongue- Swollen, protuding
 Cyanotic = “blue-tongue”
 Coronitis- Inflammation of
coronary band
 Laminitis
 Lameness - Painful hooves
 Feet Sore hooves

23.  Facial oedema with muco-purulant nasla discharge
 Crust round the eyes and nares
 Intense congestion and swelling of lips and gums and
sloughing of the dental pad mucosa
 Wry neck
 Loss of fleece

24.  Pregnancy:
 Early – death, abortion
 Middle third – survive but may have viramia
 Later – malformation and hydroencephaly

25. Necropsy Findings
 Face and ears edematous
 Dry, crusty exudate on nostrils
 Coronary bands hyperemic
 Internal hemorrhages
 Hydronencephaly, cerebellar dysplasia
 Pathognomonic – Hemorrhage at the base of
“Pulmonary Artery”

26. Diagnosis
 Clinical signs –
 Fever
 nasal & ocular discharge
 lips & head oedema
 Hemorrhage & inflammation of coronary band

27. Virus isolation & Identification:
 Tissue culture
 Culture in embryonated chicken eggs
 The embryos die within 6 days with haemorrhages
 Infected CAM is used as a source of virus in VNT, CFT, ELISA,
etc.
 Cell lines
 Insect origin- KC cell lines (Culicoides sonorensis)
 Mammalian cell lines – BHK cells, CPAE cells, Vero cells
 Virus identification:
 Immuofluorescence
 Immuoperoxidase assays
 Require 2-4 weeks

28. Serological Test
 CFT test
 AGID test
 SN test
 VN test
 ELISA test – cELISA

29.  Competitive ELISA:
 It uses a VP7 monoclonal antibody which reacts with the
VP7 of all BTV serotypes.
 It is a very sensitive and highly specific method
(serogroup specific test).
 It is now the official test for moving animals

30.  Serum-neutralization:
 Neutralising antibodies bind the VP2 protein
 It is capable of identifying the BTV serotype (serotype
specific test)
 It is highly sensitive and specific

31. Detection of Antigen or Nucleic acid:
 Immunofluorescece
 Immunoperoxidase
 Immunoelectron microscopic technique using monoclonal
antibody
 In situ – used even after viremic phase
 Hybridization
 RT-PCR – within 24 hrs, a rapid, sensitive and reliable method for the
identification and differentiation of the twenty-six BTV serotypes
 RT-LAMP assays – eastern or western topotypes BTV strains
 Advantage
 Speed
 Differentiate wild-type isolates & vaccine strains

32. Animal inoculation
 Sheep – inoculation of blood
 Most sensitive and reliable method of BTV isolation
 Positive test – clinical signs or mounting of a BTV
specific antibody response
 intracerebral inoculation of newborn mice

33. Treatment
 No specific treatment
 Supportive therapy
 Protection from the elements
 Fluids and electrolytes
 Antibiotics for prevention of secondary infection

34. Control
 Control of vectors by insecticide
 Reduce transmission
 Protect susceptible animals
 Quarantine and movement controls
 Prevent spread of virus
 Animals confined indoors(i.e., barn)
 When vectors are active
 Disinfection
 Does not stop virus transmission
 Cleaning the premises
 Sodium hypochlorite (bleach)
 3% Sodium hydroxide (lye)
 .

35.  Vaccination
 Live egg adapted polyvalent vaccines
 Inactivated vaccines
 Notification to authorities

36. Vaccines in India
 Technology transferred from IVRI, July 2012.
 BTV serotypes are 1, 2, 10, 16 and 23
 Under All India Network Project on
 Blue Tongue, ICAR, efforts are concentrated on
developing effective vaccine

37. Conclusion
 Blue tongue is endemic in India.
 Control of BT is difficult due to so many serotypes of
virus and abundant population of vector.
 Difficult to completely eradicate

38. Reference
 Peter D. Constable, Keneth W. hinchcliff, Stanley H. Doe, Walte
Gunber. (2017) Veterinary Medicine, A Textbook of the Diseases of
Cattle, Horses, Sheep, Pigs, and Goats, 11th Edit.
 Orru G, Ferrando ML, Meloni M, Liciardi M, Savini G, et al. (2006)
Rapid detection and quantitation of Bluetongue virus (BTV) using a
Molecular Beacon fluorescent probe assay. J Virol Methods 137: 34–42.
 Mertens PPC, Attoui H (2011) The RNAs and proteins of dsRNA viruses
 Narender S. Maan1 et. al. (2012) “Identification and Differentiation of
the Twenty Six Bluetongue Virus Serotypes by RT–PCR Amplification
of the Serotype-Specific Genome Segment 2” PLoS ONE 7(2): e32601.
doi:10.1371/journal.pone.0032601