Outcomes
The research team detected viral RNA in nasal swabs 48 hrs after horses were exposed to the virus and in blood 24 hrs prior to the onset of fever. Once fever was established, oral swabs, rectal swabs, urine and faeces from the stall floor were also positive for viral RNA; the amount of viral RNA steadily increased with the onset of clinical signs.
The team identified the feasibility of case confirmation in the febrile horse prior to the onset of either localising signs or other signs of systemic disease, and prior to the likely period of greatest transmission risk. Clinically ill horses and post mortem examination of horses that have died from HeV infection pose the greatest risk of infection. Certain veterinary procedures on horses infected with the virus might pose an infection risk too.
Visionary Goal
To support guidelines provided to veterinarians and horse handlers to reduce the transmission risk of Hendra virus infection to people and other horses.
Background Statement
Since its emergence in Queensland in 1994, Hendra virus (HeV) infection in horses has recurred on a regular basis with at least two disease events recorded in four of the past five years. Humans have also become infected with the virus and of the six cases known today, three have died, the most recent of these in August 2008.
The clinical and laboratory evaluation of affected horses has been very limited due to the reluctance of attending staff to collect the necessary diagnostic information. In particular, optimal biological samples for rapid confirmation of the diagnosis in the live animal, and the relationship between the onset of clinical signs and duration of viral shedding have not been determined.
Nervous signs have been associated with previous outbreaks of HeV, however, the conventional paradigm is that HeV causes a respiratory syndrome in horses. In the recent outbreak, the major presenting signs in horses were attributed to disease of the central nervous system not to HeV, and the failure to consider HeV in the early differential diagnosis of affected cases increased the exposure risk to attending staff and to in-contact horses.
In this study we will describe the associated clinical syndrome(s) of HeV, document the optimal samples to be collected for rapid diagnosis in clinical suspects, and determine the time period over which horses may represent a transmission risk during the acute stage of infection.
Objectives & Aims of Project
1. To reduce the exposure risk for people from horses acutely infected with HeV.
2. To describe the clinical and pathological characteristics of HeV (Redland Bay 2008) and develop a revised case description if indicated.
3. To determine the natural routes of shedding of this particular HeV isolate from horses.
4. To determine the relationship between the first detection of shedding of live virus or genetic material in relationship to the onset clinical disease.
5. To determine the optimal biological specimen(s) to be collected from clinical suspects for rapid and early confirmation of the diagnosis
Deliverables
1. A contemporary case description of HeV in horses.
2. A list of the natural routes of shedding of Redlands Bay HeV from horses and a comment as to their likely relative significance.
3. An assessment of the exposure risk of horses at various stages of the acute disease process, especially with respect to onset of clinically detectable illness.
4. Recommendations for optimal biological specimen(s) to be collected from clinical suspects for rapid and early confirmation of the diagnosis. |