October 28, 2018

The Transmission of Equine Influenza Virus to English Foxhounds

By Flickr user Thowra_uk (Flickr here) [CC BY 2.0  (https://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

Equine influenza (H3N8) is the strain of flu commonly found in horses. Thus, when two outbreaks of equine influenza occurred in dogs, one in the United Kingdom in 2002, in a group of 92 English Foxhounds. The other, in 2004 in Florida, amongst a group of greyhounds.



This study, done on the outbreak in 2002 within the group of English Foxhounds was prompted by the second outbreak in Florida. The outbreaks were categorized by coughing, tiredness and weakness, unconsciousness, and resulted in 6 deaths and 1 euthanization. While originally, the cause was unknown, postmortem analysis of the 7 dead dogs revealed they all had pneumonia, suggesting the hounds had contracted some sort of virus.


Researchers knew the dogs hadn’t contracted a common dog virus, as they had all received the traditional vaccines for respiratory and intestinal viruses. Furthermore, initial tissue readings of the deceased canines tested negative for canine pathogens. This negative result caused researchers to write the cause of this outbreak as “unknown,”  until 2005, when they received serum samples from 30 members of the infected pack, along with 30 more from 3 not infected packs.


The serum samples were tested for the presence of antibodies, specifically antibodies for human and equine (H7N7) influenza. The samples from both the control groups and the infected group tested negative for both of the human and equine influenza, however the infected group showed antibodies for another strand of equine influenza (H3N8.) It was later confirmed the antibody detected in this test matched 100% with the antibody for H3N8.


Tissue from the lungs, liver, liver, spleen, and other visceral tissues of the deceased dogs was then tested for potential damage caused by the equine influenza. All but the lungs tested negative. The lungs, however, showed pneumonic change.


Subsequently, the lungs of the foxhounds were tested to see if they were receptive to the equine influenza antigen. The test showed the receptors with the required linkage for equine influenza are available on canine respiratory cells.  


The 92 English Foxhounds who in this study were living near horses, so it is possible they contracted the virus through airborne methods. However, a week before symptoms were shown, the dogs were fed euthanized horse meat, so it can not be concluded what way the dogs contracted the virus.


This study demonstrated that the transfer of equine influenza to dogs in the United Kingdom. Additionally, this study showed dogs respiratory tissue is receptive to infection by equine influenza.



Daly, Janet M et al. “Transmission of equine influenza virus to English foxhounds” Emerging infectious diseases vol. 14,3 (2008): 461-4.


Article Reviewed By Calvin Isley | October 28 2018