Bluetongue is a non-contagious, insect-borne viral disease primarily affecting sheep, with 22 of 26 serotypes reported in India. Significant outbreaks have occurred, particularly during monsoon seasons, leading to high morbidity and mortality rates in sheep while other ruminants usually remain subclinical. Control measures include vaccination, vector management, and improved veterinary care, though challenges persist due to various environmental and economic factors.

1. Bluetongue in India
Dr. Bhoj R Singh, Principal Scientist (VM)
Head Division of Epidemiology
Indian Veterinary Research Institute,
Izatnagar-243122, Bareilly, UP, India.

2. Bluetongue Virus
 Family Reoviridae
◦ Genus Orbivirus
 26 serotypes worldwide
◦ 6 serotypes isolated in the U.S.
 Non-contagious
 Insect-borne viral disease
 Ruminants: Primary host is sheep
 Others infected: Cattle, goats, deer

3. History
 First described in South Africa in 1881 and it was
ascribed as “epizootic catarrh”
 In 1905 the disease was renamed as “Blue tongue”
(Spruell, 1905).
 The name blue tongue originated from the dutch word
“blaau tong” means mouth sickness
 The disease was first reported in Pakistan in 1959 and
in India in 1964 (Sapre S.N.,1964)
 First report of BT in Maharashtra.
 Between 1967 and 1970 disease was reported in exotic
sheep.
 In 1974 BT was reported in the Dorset breed in Andhra
Pradesh.
 In 1981 BT was widely spread in Southern India.

4. Blue Tongue - Indian Scenario
 BT is endemic in many parts of India and its outbreak in
 22 serotypes are recorded in India out of 26 serotypes of BTV.
 Morbidity and mortality – High in Sheep, low in Goats
 Cattle and Buffaloes – Seroprevalence without clinical disease (Prasad
et.al . 1992).
 In Tamil Nadu during the monsoon season of 1997–98 BTcaused the death
of 300,000 sheep and goats
 According to the all-India livestock census of 2003, West Bengal state,
situated in eastern India has a population of 1.4 million sheep, susceptible
to BT. Anti-BT antibodies have been detected in sheep, goats and cattle of
West Bengal (Chakrabarti et al,2007 & Batabyal et al, 2008).
 The seropositivity of goat for Bluetongue was found to be 27.95% in
Nagpur.
 Seroprevalence of 27.97% in Bidar district of Karnataka (Bhoyar et. al.,
2004)
 Higher prevalence of Bluetongue in goats (58.01%) has also been
reported from Goa (Barbuddhe et. al., 2005)

5. Morbidity and Mortality by BT
Sheep
Severity of disease varies
Breed
Strain of virus
Environmental stress
Morbidity: as high as 100%
Mortality: usually 0 to 30%
 Cattle, goats
◦ Morbidity: up to 5%
◦ Death is rare
 Deer, antelope
◦ Severe infection
◦ Morbidity: up to 100%
◦ Mortality: 80 to 90%

6. Temporal and Spatial
distribution
Temporal distribution
 distribution of
disease in relation to
time,
 e.g. occurrence of
disease incidents in
different seasons
Spatial distribution
 distribution of
disease in relation to
position in space,
 e.g. Incidence of
disease in specified
geographical areas
Saunders Comprehensive Veterinary Dictionary, 3 ed. © 2007

7. Transmission of BT
 A vector borne disease.
 Principal vector Culicoides insects are the major
vectors of BTV. Of over 1,400 species present
worldwide, at least 39 have been reported to
occur in India
 C. imicola
 C. oxystoma
 Mosquitoes , sheep ked and argasid tick

8. Major Vectors
Midges
South India
 Culiciodes
brevitarsis
 Culicoides imicola
(Ilango et.al 2006)
North India
 Culicoides
oxistoma
 Culicoides
monocoli
(Maheswari, 2012)

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

10. Serotypes reported in India
 Through Virus Isolation
(11)
 1,2,3,4,8,9,15,16,17,18,2
3
 Through detection of
Neutralising
antibodies(11)
 5,6,7,10,11,12,13,14,15,
19,20
State
Serotypes
Neutralizing Ab’s
Virus Isolation
J&K - 23
Himachal 4 3,4,9,16,17
Harayana 2,8,12,16 1,4
Rajastan - 1
UP 23 9,8,13
UK - 23
MP 18,23 23
Gujarat 1,2,3,5,8,9,10,11,12,
13,15,16,17,20
6
Maharashtra 2,3,4,5,5,7,8,10,12,13,
16
1,9,16,18,4,17
Andhra 4,6,12,13,14,17,18,19 2,9,15
Karnataka 1,2,4,12,16,17,20 18,23
TN 1,3,4,5,6,7,11,12,14,
15,16,17,19,20
1,2,3,16,23
Newer Concepts in Animal Diseases, 2011, IVRI

11. Clinical Signs
Sheep
•Incubation period: 5 to 10 days.
• High fever.
• Edema of the face, lips, muzzle and ears.
• Excessive salivation.
• Hyperemic oral mucosa.
• Mucopurulent nasal discharge .
•After the first few days and the tongue may become cyanotic.
•Oral lesions may progress to petechial hemorrhages, erosions,
and ulcers.
• Lameness characterized by petechial
hemorrhages at the coronary band.
•Hooves may eventually slough off.
• Fragile wool and diarrhea.
Cattle and goats
Usually subclinical.
Erosions, crusts around nose and teats
Coronitis.
Reproductive failure.
Antelope and deer
Hemorrhage, death.

12. Post Mortem Lesions
 Sheep
◦ Face and ears edematous
◦ Dry, crusty exudate on nostrils
◦ Coronary bands hyperemic
◦ Internal hemorrhaging
◦ Hydranencephaly, cerebellar dysplasia
 Cattle
◦ Skin: edematous, ulcerated, dry, thick
folds
◦ Mouth: vesicles, ulcers, necrosis

13. Diagnosis
 Clinical signs
 History
◦ Insect activity
◦ Wasting or foot rot
 Laboratory
◦ Virus isolation
◦ ELISA, IFA, VN
◦ PCR
◦ Complement fixation test

14. Differential Diagnosis
 Foot-and-mouth disease
 Vesicular stomatitis
 Peste de petits ruminants
 Malignant catarrhal fever
 Bovine virus diarrhea
 Contagious pustular
dermatitis
 Infectious bovine
rhinotracheitis
 Parainfluenza-3
infection
 Sheep pox
 Foot rot
 Actinobacillosis
 Oestrus ovis
infestation
 Plant
photosensitization

15. Sampling
Before collecting or sending any
samples, the proper authorities
should be contacted
Samples should only be sent under
secure conditions and to authorized
laboratories to prevent the spread
of the disease

16. Treatment
 No specific treatment
 Supportive therapy:
includes protection from the elements (e.g., the wind or
sun), keeping animals warm and dry, and giving fluids and
electrolyte solutions if needed.
 Mouth / foot Lesions should be washed thoroughly with 4%
solution of potassium permanganate or 2 –4 % solution of
soda bicarb and then apply boro-glycerine over the mouth
lesions.
 Otherwise turmeric powder with oil can also be applied.
 Due to lesions in mouth animals are off feed. Hence feed
such animals with palatable green fodder e.g. Lucerne,
green grass etc.
 In order to avoid secondary bacterial infection in ailing
animals, broad-spectrum antibiotics along with liver tonics
should be given
 Strict bio-security measures should also be followed

17. Bluetongue in Humans
 Not a significant threat to humans
 One human infection documented
◦ Reasonable precautions should be
taken
 Disease in humans is not fatal
 Treatment is supportive care

18. Blue Tongue Serotypes in
India
Srinivasalu ., et al 2004

19. BT Outbreaks in India
Source: IBVNet, 2005

20. BT in India, DAHF, Govt of India
8.7
3.7
8.6
10.2
8.2
7.0
6.2
5.4 5.2
3.7 3.8
4.5
5.2
4.5
3.6
5.7
7.9
3.7
4.5
4.8
5.2
5.9
6.3
5.6
11.4
10.9
0.0
2.0
4.0
6.0
8.0
10.0
12.0
Outbreaks of BT (Log2 values)
Cases per outbreak of BT (Log2 values)
Outbreak of BT in India and cases per
outbreak
13.19
7.27
14.29
18.10
11.9111.5011.04
10.55
11.11
10.00
9.36
15.89
16.13
9.36
5.52
11.30
15.97
9.09
8.42
9.43
6.29
7.09
6.07
7.18
12.62
13.11
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
Anaimal affected with BT (Log2 values)
Animals died with BT (Log2 values)
Morbidity and Mortality due to BT in India

21. Seasonality
 Cyclical occurrence
 June to September
South-western
monsoon
 October to December
North eastern Monsoon
 Monsoon leads to High
Vector population
 Overall Morbidity 9.3%
 Mortality 2.7%
 CFR 28.8%
 (Srinivasalu et.al 2004)

22. Month wise outbreak in
Karnataka
( Source: PDADMAS 2010-11)
 Higher incidence in
winter months
 November and
December
 Moist soil after flood
with ideal wind
speed- large scale
breeding of
Culicoides

23. Prevalence of BTV antibodies in Sheep and Goats
 Northern India- Harayana,
H.P, J&K, Punjab, Rajastan,
UP
 Central India– M.P
 Western India– Gujarat,
Maharashtra
 Southern India– Andhra,
Karnataka, Kerala and T.N
 North Eastern India– No
reports (Prasad et.al 2000)
(Bitew.,et.al, 2013, African J. Biotech)

24. Seroprevalence in Cattle and
Buffaloess
 First Reported in Annual Report of IVRI,1978
 3.7% Cattle positive for BTV
• Native23%
• Exotic71.9%
• Cattle70%
• Buffaloes
37.5
%
Punjab Andhra Pradesh
Srinivasalu., et.al 2004

25. Seroprevalence in Cattle and
Buffaloes
 Currently
Seroprevalence has
been (Sub clinical)
reported in North Eastern
States too.
Joardar SN, et.al Vet.World, 2013
Rev.Sci.Tech.Off.Int.Epiz:1992 Prasad et.al
58.2 %
31.79 %
70 %

26. Why endemic in India?
 22 serotypes reported
 Clinical signs not reported in Goat, Cattle, Buffalo
and deer RESERVOIR??
 Seroprevalence in Camels, Deers and Elepahant (Prasad
et.al,1992)
 Knowledge of fauna & biology of Culicoides spp. is
poorly known in India.
 Vaccines – Not very good have Poor immunogenicity
Prasad,et.al 1992

27. 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 Ilango et.al 2006

28. How BTV reached India?
1964 – BTV reported in Maharashtra ,U.P –
 Movement of
infected
animals/Vector form
Paksitan?
 It is probable
because India
shares long border
with Pakistan.
Import of cattle, Sheep
and Goat for cross
breeding?
 1973 – outbreak in
Hisar in Russian
Merino
 1975- outbreak in
CSBF, Hisar -
Corridale Sheep –
Indo Australian
project
 1974 - outbreak in
Dorset breed,
Andhra
Prasad,et.al 1992

30. Control
Quarantine
 Quarantine and movement controls. Prevent
spread of virus
 Confine animals indoors (i.e., barn when vectors
are active
Disinfection
 Does not stop virus transmission
 Cleaning the premises
◦ Sodium hypochlorite (bleach)
◦ 3% Sodium hydroxide (lye)
Insect control
◦ Pyrethroids
◦ Organophosphates

31. Prevention and Control
 Effective vaccination may reduce
incidence
 Many Countries eradicated BT and
possible in India. (UK 2008)
 Restricting animal movement
 Insecticide sprays,
 Habitat removal - Vector
 Timely announcement of satellite
based weather forecasting and
educating sheep farmers
 Community Participation
 Vaccination
Bhanuprasad., et al 2009

32. 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

33. Quiz
 Why Blue Tongue (BT) is endemic in
India?
 What are environmental factors
responsible for spread of BT?
 Is it possible to control BT in India? If yes,
how and if No, why?
 What may be the good qualities of BT
vaccine to be used nationwide?
 How to control an outbreak of BT?