Introduction
Hendra virus (HeV; genus Henipavirus , familyParamyxoviridae ) is an emerging zoonotic virus carried by four species of Pteropus bats in Australia (Annand et al., 2022; Middleton et al., 2014). Transmission of HeV to horses is considered to be predominantly from P. alecto (Annand et al., 2022; Edson et al., 2019) and infected horses are the primary source of infection for people (Middleton et al., 2014; Yuen et al., 2021). Sixty-six spillover events between bats and horses have been recorded, resulting in 108 horse deaths and seven reported human infections including four deaths (Annand et al., 2022; Business Queensland, 2021; NSW Health, 2022). There have also been two reported cases of HeV infected dogs (Field, 2016).
The risk of HeV disease (HeVD) in horses is expanding geographically. Cases have recently been reported as far south as Scone (Business Queensland, 2021; Yuen et al., 2021) and West Wallsend, New South Wales, in 2021 (J. Taylor et al., 2022). The latter case occurred beyond the previously described P. alecto distribution of eastern coastal Queensland to northern New South Wales (Annand et al., 2022). A new strain, HeVD-g2, for which the pathogenicity and prevalence inPteropus bats in Australia is unknown, has also recently been detected in Queensland (Annand et al., 2022).
Therapeutics for the treatment of HeVD are not available; however, a vaccine for horses and post-exposure prophylaxis for humans have been developed (Annand et al., 2022; Middleton et al., 2014). Horses aged ≥4 months can be vaccinated (Zoetis Australia Pty Limited, n.d.), with two doses given 3-6 weeks apart and a third dose six months later, then an annual booster dose thereafter (Zoetis Australia Pty Limited, n.d.). Despite the availability of the vaccine since 2012, the expanding risk of HeVD, the high case fatality rate of HeVD in both horses and humans, HeV vaccine uptake is as low as 17% in Queensland and 12% in New South Wales risk regions (M. Taylor et al., 2016). As well as protecting equine welfare, HeV vaccination of horses remains a priority to protect public health (Degeling et al., 2018; Degeling & Kerridge, 2013).
The recent development of the Behavioural and Social Drivers of Vaccination (BeSD) framework has demonstrated value in understanding and promoting vaccine uptake by caregivers in the context of vaccine-preventable childhood diseases (World Health Organization, 2022a, 2022b). In this framework, there are four measurable domains of behavioural and social drivers in individuals that are potentially changeable: (1) Thinking and Feeling , relating to cognitive and emotional responses to vaccine-preventable diseases and vaccines, including disease risk perception and vaccine confidence; (2)Social Processes , defined as the social experiences related to vaccines, including gender equity, social norms about vaccination, and receiving health worker recommendations to be vaccinated; (3)Motivation , influenced by the former two domains, and including vaccination intention, willingness, and hesitancy; and (4)Practical Issues , which are people’s experiences when trying to get vaccinated, including access barriers such as availability, affordability, ease of access, quality of service, and respect from health workers (WHO, 2022b). The combination of the four domains drives or hinders uptake of recommended vaccines (WHO, 2022b). Given the potential similarities between parents making vaccination decisions for their children and horse owners deciding on vaccination for their horses, the BeSD framework may be useful in helping to understand the drivers of HeV vaccination.
The objective of this review was to collate information about evidence-based communication interventions that have been used to promote HeVD vaccine uptake by horse owners. We hypothesised that there are few interventions; therefore, a secondary objective was to appraise information in the reviewed records against the domains of the BeSD framework as a preliminary assessment of the types of information available about factors that drive or hinder HeVD vaccine uptake. This review and assessment will inform research and development of a program to promote HeVD vaccination.