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.;
- Ornithodoros coriaceus
- Ornithodoros turicata
- 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
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