20. Bluetongue and other sheep notifiable diseases (Peste des petits ruminants, Maedi-visna, Nairobi)

bluetongue ae

ds-RNA virus

fam : reoviridae

genus : orbivirus

spp : bluetongue virus

bt general (contagious? how spread? listed? zoonosis? serotypes?)

non-contagious (doesn’t cause persistent infections)

insect-borne (Culicoides)

WOAH

not zoonotic

29 serotypes

bt epizoo

where insect

africa, asia, australia, europe, america

islands, tropic

2022 Portugal

2023 Kent, UK

maintained in areas where climate allows midges to survive over winter (global warming)

bt vector

midges (culicoides)

infected when bite vertebrate

whole life infect

bt sources of infection

vector midge

semen, blood (not signifiant)

bt pathogenesis, pathology

bite - replicate in regional LN, lymphoid tissue, - blood vessels (viraemia) - spread to endothelium of all organs and tissues - secondary viraemia (varying duration)

destroy epithelium of blood vessels - effusions of body cavities, oedematous changes (head), serosal and visceral haemorrhages

cyanosis mm and tongue

no chronic infection

peak viraemia 7-8d

bt cs

- acute: (sheep, deer) fever, hypersalivation, dyspnoea, nasal discharge, hyperemia and congestion of head (oedema → blue tongue [cyanosis]), ulceration and necrosis of mucosae of mouth, death due to heart attack

- inapparent infection: in cattle mostly

bt dg

cs, pm, season

samples : blood in heparin (alive), spleen, liver, bone marrow, ln

id : elisa, vnt, IFA

serology: CF, agar gel immunodiffusion, competitive ELISA

bt tx

none

kill affected

isolate rest

maedi - visna ae

rna virus

fam : retroviridae

genus : lentivirus

spp : visna virus

mv general (organs affected? species affected? listed? zoonosis?)

brain (v) lungs (m)

goat and sheep

WOAH

not zoonotic

mv epizoo

worldwide

inc spain, greece (Romania 2022)

free: iceland NZ australia

mv transmission

fecal-oral

inhalation

mv pathogenesis

integrated in leukocyte DNA (lung macrophages, monocytes - carry to brain, lung, udder, joints

after 2-6 years, T-cells react → type IV immune complex disease - target organs chronically inflamed

visna in host cell dna-inhibit T cell replication

visna pathology

demyelinisation

subacute meningitis around ventricles

posterior paresis

maedina patho

infiltration of alveolar septa by lymphocytes and macrophages

smooth muscle hypertrophy

enlargement and emphysema lungs

visna cs

long incubation so older than 2y when show cs

early: hindlimb weakness, lip trembling, head tilt, loss of condition

later: ataxia, muscle tremors, paresis

meadi cs

wasting dyspnoea, dry cough, death due to secondary anoxia

other cs

arthritis, lameness, chronic mastitis

mv dg

cs +2yo (respiratory and neural, mastitis)

PCR, southern blot (detection and quantification of specific DNA)

serology: ELISA, agar gel immunodiffusion

peste des petits ru (ovine rinderpest) ae

rna virus

fam: paramyxoviridae

genus : morbillivirus

spp : small ru morbillivirus

ppr general (listed? zoonotic? common name? species affected?)

WOAH

not zoonotic

goat plague

goat, sheep

ppr epizoo

africa

middle east (Türkiye 2023)

south asia

Europe (Georgia 2016)

ppr transmission

aerosol

direct or indirect contact

no carrier state

in secretions, excretions

ppr cs

ip 3-6d

fever, depression, loss of appetite, nasal discharge

nasal discharge becomes thicker, yellow

swelling eyes, ulcer oral cavity

diarrhoea - severe dehydration

pneumonia (later stages)

pregnant may abort

ppr dg

vnt

elisa

rt-pcr

ifa

culture - cell culture

other WOAH diseases sheep

- contagious agalactia

- enzootic abortion of ewes

- ovide epididymitis

- salmonellosis

- scrapie

- sheep and goat pox

nairobi ds general (transmission, classification, mortality, listed, zoonosis?)

tick borne

fam : bunyviridae

Nairovirus

90% mortal

WOAH

zoonotic

nd epizoo

east africa, asia

warm climate

nd cs

fever, depression

mucopurulent, blood stained nasal discharge

abortion

conjunctivitis

death 2-7d acute

nd pm lesions

dehydration

enlarged, oedematous LN

splenomegaly

haemorrhages in GIT RT UGT heart

nd dg

plasma from febrile animals

mesenteric ln

spleen

serum

Immunodiffusion, ELISA

nd tx ctl

none

acaricide

vaccine

bt outbreak ctl

LEGISLATION!

- vector ctl: repellent, insecticide, insect nets

- restrict movement to non-infected areas, export semen, ova, embryo (need exemption)

- vaccine

- id, tracing

- blood sample (mv) (kill+)

- quarantine, isolate, kill

bt outbreak zones

control: 20km

protection: 100km

surveillance: 150km

outbreak prevent

vaccinate bt (no mv)

dg and surveillance: serological screening (blood, vector)

insect ctl (stagnent water)

ctl imported animal

eradication prog, movement control, euthanasia (nairobi)

hygiene

bt sanitation resist

years in blood

50° 30min or 60° 15min

pH

bt disinf

- NaOH (3-5%), peracetic acid (0,5%)

B) prevent insect ctl

know life cycle: prevent reproduction, prevent access to house/feed/food

insecticides effect on repro, lc, entry, action, origin

Mosquitoes: eggs and pupa in water

key = standing water - removes breeding ground

B) Stages of preventive insect control

Preparatory work

Investigation work

Selection of insecticide and method of insect control

B) Types of insect control

Mechanical: window screens, adhesive substances, light

Physical: temperature, steam, UV, radiation, ultrasound

Biological: introduction natural enemies (parasites, pathogens)

Chemical: insecticides (classified by effect on life cycle, entry, mode of action, formulation, origin)