Vector Borne Exotic Notifiable Infections of Ruminants Flashcards
what are notifiable diseases of ruminants (8)
- bluetongue
- rift valley fever
- lumpy skin disease
- sheep pox and goat pox
- contagious bovine pleuro-pneumonia (CBPP)
- Rinderpest
- Peste de petit ruminants (PPR)
- foot and mouth disease
what makes a disease notifiable
high mortality
high morbidity
what are epidemilogical features of notifiable diseases in endemic areas
mild or inapparent infection in indigenous stock
- innate immunity
- maternal immunity
serious disease – lack of immunity
- imported ‘exotic improver’ stock
- Imported ‘exotic improver’ stock
- Young stock
- Old, infirm, stressed animals
- Sick animals (immuno-suppressed)
what are epidemilogical features of notifiable diseases in disease free areas
sporadic epidemics
high morbidity +/- high mortality
what are the key epidemiological features of vector borne notifiable diseases
seasonal – insect vector activity
sporadic epidemics
- When vector extends its range
- Freak weather conditions
- Generally self limiting
Establishment of infection in new areas linked to:
- Change in vector habitat or husbandry
- Global warming
- New strain of virus
- Poverty
what type of virus is bluetongue
arbovirus
orbivirus or the family reoviridae
what is the vector of bluetongue
culicoides species (midges)
how is bluetongue transmitted
Requires replication in a arthropod vector
Culicoides species — midges
Not contagious — but rarely transmission via placenta and semen
what does the clinical disease of bluetongue depend on (3)
species and breed
virus type and strain
immunity
which species does bluetongue virus cause severe disease in
sheep
deer
which species are carriers of bluetongue virus
cattle and goats are reservoir hosts
how does bluetongue virus replicate in the midge
- Female midge feeds on viremic ruminant
- Ingested virus crosses gut wall
- Virus replicates in midge salivary gland (6-8d)
- Temperature dependent
- Midge becomes viremic (lifelong)
- Viremic midge takes next blood meal and injects virus into ruminant
- Virus replicates in ruminant cells
- “indirect transmission only”
what is midge activity dependent on
Temperature
Humidity
Rainfall
Soil
how does bluetongue virus replicate in the ruminant
Infected Culicoides deposits virus into skin of ruminant
Virus drains to regional lymph node
Primary virus replication
- Lymph node endothelial cells and leukocytes
Virus spreads to other lymphatic organs in a transient viremia
Secondary replication
- Endothelial cells of many organs
Generalized viremia
Virus closely associated with erythrocytes (invaginations)
Some protection against the immune response
Cullicoides spp feed on infected animals become infected
how does bluetongue cause a hemorrhagic fever
- Virus replicates in endothelial cells and cause cell lysis and cell distortion
- Blood vessels become ‘leaky’
- Serum and lymphatic fluid leaks out and cause edema and swelling
- Severely damaged blood vessels may hemorrhage and cause petechiation
- Tissue damage has pyretic effect and causes a fever
what are the sequele of hemorrhagic fever in bluetongue
The body reacts to foreign/damaged proteins with inflammation
Increases blood flow:
- Redness, heat, swelling, edema
- Conjunctivitis, hyperemia of mucosal membranes
- Coronitis
what are the severest clinical symptoms that occur in bluetongue
Fever does not subside and animal is severely depressed
Lungs severely edemic, air exchange impossible
- Respiratory distress
Disseminated intravascular coagulation
what is the incubation period of bluetongue
7-14d
what are the clinical signs of bluetongue virus
Fever, anorexia, respiratory distress
Conjunctivitis
Oculonasal discharge
Crusting nose and lips
Stomatitis
Oral ulcers
Edema of head, tongue (cyanotic) and legs
Coronitis
Lameness
Abortion
Deformed lambs
Emaciation
Death
what is the morbidity of bluetongue virus
80-100%
what is the mortality f bluetongue virus
50-70%
what are PM findings of bluetongue
oral erosions
edema of head and neck
cyanosis of mucous membranes, bluetongue
hemorrhages in bowel, heart and base of pulmonary artery
what can be done to prevent bluetongue from coming to europe
Nothing?
- Trade restrictions
- Disease and production issues
- Welfare concerns
Control midges
Vaccinate!
what diseases have similar transmisison features to bluetongue
African horse sickness
Schmallenberg virus
