Researchers found significant levels of psychological distress among horse owners affected by the outbreak.
The findings of the research by Melanie Taylor, Kingsley Agho, Garry Stevens and Beverley Raphael are published in the open access BMC Public Health Journal.
The researchers, from the University of Western Sydney's Science of Mental Health and Adversity Unit in the School of Medicine, collected data in a 166-question online survey which connected to affected horse owners through various industry groups.
Horse owners were not only having to contend with sick horses but also movement restrictions and the quarantining of properties. Racing came to a standstill and horse-related events across the country were cancelled. Incomes suffered or were lost.
The researchers assessed the psycho-social impacts of the disease based on the data collected from 2760 people.
"Extremely high levels of non-specific psychological distress were reported by respondents in this study, with 34% reporting high psychological distress compared to levels of around 12% in the Australian general population."
Those living in the high-risk red zones set up by authorities during the containment effort or the amber buffer zones were at much greater risk of high psychological distress than those living in uninfected (white zones), the researchers said.
"Although prevalence of high psychological distress was greater in infected EI zones and states, elevated levels of psychological distress were experienced in horse owners nationally.
"Statistical analysis indicated that certain groups were more vulnerable to high psychological distress; specifically younger people, and those with lower levels of formal educational qualifications.
"Respondents whose principal source of income was from horse-related industry were more than twice as likely to have high psychological distress than those whose primary source of income was not linked to horse-related industry."
The researchers said that although the study had its limitations, in that it was not possible to identify, bound, or sample the target population accurately, the study was the first to collect psychological distress data from an affected population during such a disease outbreak.
"[It] has potential to inform those involved in assessing the potential psychological impacts of human infectious diseases, such as pandemic influenza," they wrote.
They described the prevalence of high psychological distress among respondents as extremely high, "with just over one third (34%) reporting levels of psychological distress that might require some form of external intervention". Forty per cent of these (14% of the sample) reached levels that may be considered indicative of a "caseness" rating for a mental disorder as listed in the manual, "Diagnostic and Statistical Manual of Mental Disorders, 4th Edition", the authors found.
"The prevalence of 'very high' psychological distress in this sample was approaching five times the level reported in recent population health data for New South Wales.
"Although this prevalence is very high, and there are some methodological reasons why this may be distorted ... it is certainly true that many of those impacted by EI, or the threat of EI, were subject to a wide range of acute stressors over a prolonged period, in a country where EI and such rigorous disease containment and control measures were previously unknown.
"Those in the 16-24 year age category reported the highest levels of high psychological distress and analysis indicated that although prevalence and comparative risks of high psychological distress reduced from age 24 onwards, these reduced risks only became reliably statistically significant from age 45 onwards, and high psychological distress was certainly still a risk to those in the 35-44 year age category.
"This is interesting because in the general population psychological distress is generally found to peak around middle age (40s-50s).
"The study findings would suggest that younger people were particularly vulnerable and were coping less well with the consequences of EI.
"The reasons for this finding are not known, however, research literature suggests that younger people form stronger emotional attachments to animals, and they are also less likely to be resilient or practised, generally, when it comes to coping with adversity."
The authors said the findings generated further questions, such as what specifically caused the risk in psychological distress. Was it the risk of the disease itself, they asked, a concern for horses, or the social and emotional impacts of disease control measures and restrictions?
"More importantly, how enduring is this elevated psychological distress, and what are the longer term mental or physical health consequences for those affected?"
The study, funded by New South Wales Health, is entitled "Factors influencing psychological distress during a disease epidemic: Data from Australia's first outbreak of equine influenza".
While this paper reported data collected on non-specific psychological distress, the full study covered many other aspects, such as adherence to biosecurity requirements, effects of social isolation due to quarantine and the consequences of restricted horse movement and related activities, and sources of support and coping during the EI outbreak.