Arthropod-bourne infectious disease 2 Flashcards
What causes tick fever / red water fever?
Babesia spp - b.divergens mainly, also bigemina, bovis
Common vector - bovine babesiosis
Ixodes ricinus (rough pasture, moorland and heathland, high humidity, presence of other vertebrate host. Feeding season is March to June, peak in April to May, also some autumn feeding ticks but activity ceases in winter)
What can bovine babesiosis cause?
INTRAVASCULAR HAEMOLYSIS
- pyrexia
- anaemia
- jaundice
- haemoglobinuria
- death (24h in acute illness)
- severity variable according to previous exposure and immunity
- calves
Dingos is- bovine babesiosis
- Blood smear (thin adn thick smear)
- PCR
- Serology
What do you look for on a blood smear for bovine babesiosis?q
- sample from ear/ tail capillaries if possible
- THIN SMEAR: slides air dried, fixed in absolute methanol and stained for 20-30 mins with 10% giemsA
- THICK SMEAR: not fixed prior to staining allowing RBC lysis and concentration of parasites
- morphological variability : annular stages, pear shaped (pyriform) trophozoites either singly or in pairs and filamentous / amorphous shapes)
Outline serology in diagnosis of bovine babesiosis
- surveillance and export certification
- usually AbS detected by IFA test or ELISA
Control - bovine babesiosis
- avaricides ( can decrease incidence but only one infected tick sufficient for transmission)
- tick habitat removal
- avoid certain pastures / deliberately graze young stock on known babesia / tick pasture
- LAV available
Tx - bovine babesiosis
- anti-parasitic drug e.g. Imidiocarb
- supportive
- success depends on stage of infxn
What is the zoonotic risk of babesia?
- rare serious acute dz in splenectomised people
- also reported in immunocompetant people
What causes tick borne fever?
Anaplasma phagocytophila (also called ehrlichia phagocytophila)
Outline tick borne fever
- rickettsial parasite of leukocytes
- main European vector is Ixodes ricinus
- cattle, sheep, (goats), horses, dogs
- maintained in sylvatic cycle: tick to wildlife
- causes human granulocytic anaplasmosis
cS - tick borne fever in sheep, goats and cattle
- sheep/ goats: fever and abortions
- cattle: fever, milk drop, respiratory signs
How does tick borne fever cause immunosuppression?
LeukopEnia
Neutropenia
Reduced phagocytosis
In which cells does anaplasma phagocytophila cause intracytoplasmic inclusions?
Neutrophils
Eosinophils
Monocytes
What type of virus is looping ill?
Flavivirus endemic to UK, found in upland areas of Scotland, Wales, Nw and SW England.
Pathogens that can be transmitted by ticks and infect farm animals
- babesia spp
- anaplasma phagocytophilia
- looping ill virus
- borrelia burgdorferi
Which animals are affected by louping ill?
sheep (mostly young unvaccinated) and humans (occuational contact and tick bites)
CS - louping ill
- pyrexia
- paresis leading to neuro signs
Outline TBEV
- absent from UK
- endemic in europe and asia
- doesn’t cause dz in livestock
- 400% increase in TBE morbidity in Europe recently
- vector is Ixodes ricinus (same as louping ill)
Transmission - EIA
- horseflies and stable flies (limited range)
- salive, nasal secretions, faeces, semen, ova and embryo
- fomites
- in utero
Occurrance - EIA
- exotic to UK
- usually imported horses
- last oct 2012
- notifiable
What type of virus causes EIA?
lentivirus, can cause PI
CS - acute EIA
- incubation period 1-3 wks, (up to 3mo)
- can go un-noticed
- fever, thrombocytopaenia, lethargy, inappetance
- can be fatal
- subsequent inapparent infxn or recurrent dz episodes (usually)
CS -chronic EIA
- anaemia, thrombocytopaenia, wt loss, dependent oedema, occasionally neuro signs
- for majority of life, episodes subside and become inapparent carriers for life
Dx -EIA
- AGID + Coggins test
- since persistent virus, positive serology confirms infection (AGID + ELISA)
Outline immune response to EIA in horses
- Ab response at 10-14d, most seroconvert after 45d
- Ab+ horses are culled (statutory)
- no vaccine
What type of virus is BTV?
- non-enveloped, segmented RNA
- 25 serotypes
- VP2 is major determinant of serotype
- not zoonotic
Transmission - BTV
- Culicoides spp
- C.imicola is main vector in S Europe whereas C.absoletus/ pulicaris implicated in N Europe
What is the UK BTV situation since 1998?
7 introductions into Europe of 6 BTV strains from 5 different serotypes
Outline BTV infection
- haemorrhagic dz (direct and indirect)
- replicates in endothelial cells and mononuclear phagocytes
- prolonged cell-associated viraemia
CS -BTV in sheep
- pyrexia
- salivation
- oedema of face and lips
- cyanosis of tongue
- coronary band haemorrhages
CS - cows with BTV
- less severely affected
- may be asympatomatic
- important role in transmission
- BTV8 in N Europe unusual since CS in large no. infected catle
- oronasal crusts and erosions
Dx - BTV
- TISSUES: especially spleen adn red BM, also liver, heart blood, LNs
- blood in heparin (virus isolation/ RT-PCR)
- serum (for serology using BTV-specific competitive ELISA)
- notify AHVLA (as OIE listed dz)
Control - BTV
movement restrictions and voluntary vaccination program used to successfully control BTV8 outbreak
What can WNV infect and effects?
Virus maintained in mosquito-bird cycle but can cause incidental infcn of horses and humans: symptoms range from asympotmatic to fatal encephalitis
CS - SBV
- mild dz in adults (cattle > sheep/ goats): pyrexia, milk drop, diarrhoea
- congenital defects in CNS and MSK systems: abortions, stillbirths (sheep > calves / kids)
- infection seems to lead to subsequent immune protection
- virus neurotropism: offspring lack white matter
- stillborn lamb: arthrogryposis, torticollis (neck bent back) and brachygnathia inferior (undershot jaw)
What is the public health risk of SBV?
- initially unknown: the bunyaviridae family contains several zoonotic viruses (e.g. CCHF, RVFV, Sin Nombre)
- studies have found no evidence for zoonotic transmission using data from syndromic illness monitoring or serology
- precautionary principle
What is the SBV vaccine?
Bovilis SBV 9inactivated adjuvanted vaccine)
What is CCHF?
Crimean-Congo Haemorrhagic Fever
Outline CCHF
- bunyvarius
- endemice inmany countries in Africa, parts of Europe, middle east and asia
- wild and domestic animals (cattle, goats, sheep, hares) are amplifying hosts for the virus
- tick-transmitted (31 tick spp)
- sunclinical infection in animals
- zoonotic transmission (directly from blood/ body fluids of infected animals, tick bites)
Spp affected by louping ill
- ## sheep (mostly young unvaccinated), pyrexia, paresis –> neuro signs
Describe spp affected by tick borne encephalitis virus (TBE)
- absent from UK
- endemic in Europe and Asia
- doesn’t cause dz in livestock
- recent 400% increase in TBE morbidity in europe
- same vector as louping ill - Ixodes ricinus
Describe EIA: spp transmission type of virus occurrence
- equids only
- TRANSMISSION: horseflies and stable flies (large, limited range), saliva, nasal secretions, faeces, semen, ovva, embryos, fomites, in utero
- TYPE: lentivirus, perisistent infection when virions found in macrophages
- OCCURRENCE: exotic to UK, usually imported horses, lst Oct 2012, notifiable
Acute EIA - CS
- inbuation period 1-3 wks (up to 3mo)
- can go unnoticed
- fever, thrombocytopaenia, lethargy, inappetance
- can be fatal
- subsequent inapparent infection or recurrent dz episodes (usually)
Chronic EIA - CS
- anaemia, thrombocytopaenia, wt loss and dependent oedema, occasionally neuro signs
- for majority, episodes subside and become inapparent carriers for life
Dx - EIA
- AGID coggins test + ELISA as since persistent virus, positive serology by these methods confirms infection
Control - EIA
- Ab+ horses are culled (statutory)
- no vaccine
Describe immune response to EIA
Ab response may not develp fro 10-14d, most seroconvert after 45d
Describe what type of virus BTV is
- non-enveloped
- segmented RNA
- 25 serotypes
- VP2 major determinant of serotype
- NOT zoonotic
Transmission - BTW
- Culicoides spp
- C. imicola main vecotr in S Europe
