Ed Metzger from Southwest Ontario Veterinary Service, ASF Transmission And Soft Sided Ticks

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With the detection of African Swine Fever Virus (ASFV) in Vietnam and Cambodia it would appear that  additional dominos  have  fallen  in  the spread  of  ASF.  Of  course,  reducing  the chances  of  ASF  making  it’s  way  to North  America is the most important step. If ASF did establish itself in NA then controlling spread would at least in part be  contingent  on  the  identification  of  arthropod vectors and vertebrate hosts that are capable of viral maintenance    and    transmission    as    well    as understanding  vector-host  associations  that  may permit transmission. US researchers aggregated data on  vector  competence,  host  competence  and  tick-host associations by systematic review of published articles  and  collection  records  to  identify  species that may support the invasion of ASFV in the U.S.

Soft Sided Ticks

Three  species  of  transmission  competent  soft  sided ticks occur in the U.S.;

  1. Ornithodoros coriaceus
  2. Ornithodoros turicata
  3. Ornithodoros puertoricensis

Risk  analysis  results  indicate  O.  coriaceus,  O. turicata,   and   O.   puertoricensis   demonstrate   the highest  relative  risk  for  contributing  to  ASFV transmission  in  the  U.S.,  however,  many  gaps  in knowledge exist preventing the full evaluation of at least  30  soft  tick  species  in  the  U.S.  There  are, however,  many  additional  soft  ticks  present  in  the US for which the vector competence is unknown. Further study is required to identify soft tick vectors that  interact  with  feral  swine  populations,  elucidate vector   competence,   and   further   understand   the biology of soft tick species

Vertebrate Hosts

Three   species   of   competent   vertebrate   hosts currently occur in the U.S.;

1) domestic pigs (Sus scrofa domesticus)

2) feral hogs (Sus scrofa)

3) common warthogs (Phacochoerus africanus).

Take Home Message

Adding   the   potential   for   soft   tick   borne transmission  of  ASF  on  top  of  the  already  high risk   of   vertebrate   host   transmission   should increase anyones resolve to keep this virus out of North America in the first place.

Although there is some evidence of feral pigs in Ontario it is the western Canadian provinces that have the biggest populations of feral pigs.

A  recent  survey  of  veterinarians  in  Canada turned  up  no  evidence  of  exposure  of  Canadian domestic pigs to soft sided ticks.

Submitted by Ed Metzger, DVM

Ref: Golnar AJ, Martin E, Wormington JD, Kading RC, Teel PD, Hamer SA, Hamer  GL.Reviewing  the  Potential  Vectors  and  Hosts  of  African  Swine Fever  Virus  Transmission  in  the  United  States.  Vector  Borne  Zoonotic  Dis. 2019 Feb 20. doi: 10.1089/vbz.2018.2387. [Epub ahead of print

 

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