Flashcards in Arthropod-bourne infectious disease 2 Deck (50)
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?
- death (24h in acute illness)
- severity variable according to previous exposure and immunity
Dingos is- bovine babesiosis
1. Blood smear (thin adn thick smear)
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
- 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?
In which cells does anaplasma phagocytophila cause intracytoplasmic inclusions?
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
- paresis leading to neuro signs
- 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
- in utero
Occurrance - EIA
- exotic to UK
- usually imported horses
- last oct 2012
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
- 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