Science - animal disease

8/22/2019 Science - animal disease

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Prepared by:MONOCLONAL ANTIBODY SECTION

July 25 th

, 2013 R&D mee

ting

by Debbra Marcel



• emerging non-zoonotic, insect-borne viral disease

• affects ruminant livestock and some wild ruminants, occurs almost worldwide.

• primarily affected animals: sheep, occasionally goats and deer and, very rarely,

cattle

•

characterized by changes to the mucous linings of the mouth and nose and thecoronary band of the foot.

• the virus recognized as important agent of disease in sheep in South Africa in early

20th century, and confined to Africa.

• the first confirmed outbreak outside of Africa occurred in Cyprus in 1943

• the disease has been identified in several countries worldwide including

Malaysia since henceforth• In 2006, reported for the first time in Germany, Belgium and The Netherlands and

other parts of European countries (emerging disease)

• Listed in OIE as one of the world’s economically important disease in sheep due to

its potential for rapid spread and socio-economic impact ( Pradeep et. al, Virol. Sin. 2010)


Bluetongue disease @ catarrhal fever

http://en.wikipedia.org/wiki/Cyprus

http://en.wikipedia.org/wiki/Cyprus



• Bluetongue (BT) is caused by a type of virus called Bluetongue Virus (BTV) which

belong to the family of Reoviridae, genus of Orbivirus

• 24 serotypes of BTV have been described internationally. While the viruses

are classified antigenically and taxonomically as BTV, each serotype is unique and

may not cause BT, the disease.

• Virus particles = composed of three protein layers.

• Genomes = dsRNA distributed amongst 10 segment (facilitate virus re-assortment)

• The presence of BTV in Malaysia was first indicated serologically in 1977 and clinical

bluetongue disease was reported in imported Australian sheep (Chiang et al., 1989;

Sharifah et al., 1995). Subsequently, serotypes 1, 2, 3, 9, 16 and 23 were isolatedfrom sentinel cattle and appeared to be endemic (Sharifah et al., 1995).

• This causative agent is spread through temperate and tropical regions of the world

by biting Culicoides midges.

• The pathogenesis of bluetongue disease is similar to that of zoonotic viral hemorrhagic

fevers such as EHD(Epizootic Hemorrhagic Disease) & AHS (African Horse Sickness)

• Ref: Biosafety in Microbiological & Biomedical Laboratories, 5th Edition – CDC & NIH

Figure 1. Schematic of the mature BTV particle.

Organization of the major structural proteins VP2, VP5,

VP3 and VP7 in the architecturally complex BTV particle.

On entry into cells the outer capsid proteins VP2 and VP5

are lost, releasing a transcriptionally active core particle.


S o u r c e : m i c r o b e w i k i . k e n y o n



Prepared by:

MONOCLONAL ANTIBODY SECTION

Map courtesy of: Vet. Ital. , 40(3), 145-150

Multiple serotypes of BTV are apparently endemic in M’sia and in other countries world-wide,

located between latitudes 35◦S and 50◦N within their respective region. Recent study also shown that the

global distribution of BTV infection has recently altered, perhaps driven in part by climatic influences

on midge species resident in different regions. In short, the distribution patterns of this disease are

greatly influenced by these midges populations worldwide. Tabachnick W J ,2004, J. Med. Entomology

Figure 2: Worldwide distribution of the bluetongue viruses and the major Culicoides vectors



BTV solely relies on vector to

spread from host to host.

The midges species & populations

vary according to :-

local environmental

topographical conditions

meteorological conditions seasonal variations

- also affect the spread of BTV

• In 1983, 5 new of culicoides

species of were described in West

Malaysia (Kitaoka S, Natl Inst Anim

Health Q (Tokyo)


Figure 5: Culicoides imicola. ,the major BTV vector in tropical

regions.

Photo source: h ttp://www.nature.com/nrmicro/journal

Figure 4: BTV Transmission cycle

Photo source: http:// bluetonguevirus.org



Prepared by:

MONOCLONAL ANTIBODY SECTION

BT disease is caused by fever and vascular permeability

Characterized by changes to the mucous linings of themouth and nose and the coronary band of the foot

Ranged from mild to severe, vary by species, between

breeds and within the flock or herd.

Symptoms more severe in sheep, rarely in deer, goat &

cattle. However, relatively high number of cattle havebeen affected during the current outbreak in Northern

Europe.

The incubation period : 5 – 20 days & symptoms develop

within a month.

The clinical signs of BT : BT_clinical signs.pdf

Causing high morbidity and high mortality to susceptible

sheep (imported breed e.g Suffolk & Dorset)

Asymptomatic infected animals may spread the disease

into new areas without necessarily being noticed.

s u s c e p t i b l e a n i m a l s

deer

sheep

goat

cattle

http://localhost/var/www/apps/conversion/tmp/scratch_14/BT_clinical.pdf



































http://localhost/var/www/apps/conversion/tmp/scratch_14/BT_clinical%20signs.pdf


















Virus isolation (in ECE, cell culture or sheep)

Immunological methods (serogrouping/serotyping)

RT-PCR (viral DNA extraction)

A) Identification of BTV agent

B) Serological Tests:-

Complement fixation test (CFT)

Agar gel immunodifussion (AGID)=

Competitive ELISA (C-ELISA)

OIE

GOLD

STANDARD


OIE Terrestrial Manual 2009 Chapter 2.1.3.- Bluetongue




Control strategy

challenging/complicated due to the plurality of virus serotypes and the ubiquity and

opportunistic feeding behavior of its midge vector.

Prevention

no efficient treatment found for the disease

quarantine & vaccination are the first line of defense for every farmer as and when

vaccine becomes available in their area.

simple husbandry changes and practical midge control measures helps break the

livestock infection cycle limiting the chances of the livestock being bitten by virus-carrying midges e.g:-

a) Keping animals inside during early morning and early evening to avoid the periods

of peak midge activity

b) Keep infected stock inside to prevent them being bitten by midges and hence

passing the disease on

Surveillance

report all cases of BT infection on the premises.

livestock keepers/farmers should remain vigilant and report any clinical signs of

disease including in animals that have previously been vaccinated against BT. This will

facilitated assessment of any new midge-transmission from the continent or re-

emergence of disease

Vigilant livestock

keeper

Risk reduction

Photo source: wikimedia.com

Photo source: mstar.online




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