Unravelling animal exposure profiles of human Q fever cases in Queensland, Australia, using natural language processing

Abstract

Q fever, caused by the zoonotic bacterium Coxiella burnetii, is a globally distributed emerging infectious disease. Livestock are the most important zoonotic transmission sources, yet infection in people without livestock exposure is common. Identifying potential exposure pathways is necessary to design effective interventions and aid outbreak prevention. We used natural language processing and graphical network methods to provide insights into how Q fever notifications are associated with variation in patient occupations or lifestyles. Using an 18‐year time‐series of Q fever notifications in Queensland, Australia, we used topic models to test whether compositions of patient answers to follow‐up exposure questionnaires varied between demographic groups or across geographical areas. To determine heterogeneity in possible zoonotic exposures, we explored patterns of livestock and game animal co‐exposures using Markov Random Fields models. Finally, to identify possible correlates of Q fever case severity, we modelled patient probabilities of being hospitalized as a function of particular exposures. Different demographic groups consistently reported distinct sets of exposure terms and were concentrated in different areas of the state, suggesting the presence of multiple transmission pathways. Macropod exposure was commonly reported among Q fever cases, even when exposure to cattle, sheep or goats was absent. Males, older patients and those that reported macropod exposure were more likely to be hospitalized due to Q fever infection. Our study indicates that follow‐up surveillance combined with text modelling is useful for unravelling exposure pathways in the battle to reduce Q fever incidence and associated morbidity.

Coxiella burnetii seroprevalence and Q fever in Australian wildlife rehabilitators

“…While this study demonstrated that C. burnetii exposure was higher in AWRs compared to the general population, and although QFD notification data suggests that macropods are potential sources of infection [ 15 , 16 , 32 ], we were unable to demonstrate a positive correlation between C. burnetii seropositivity and exposure to macropods (adults or juveniles) within this cohort based on the responses to the questionnaire. Nor were we able to identify that exposure to ruminants, other domestic animals or other wildlife, or being present at non-human births were risk factors for C. burnetii seropositivity.…”

“…Nor were we able to identify that exposure to ruminants, other domestic animals or other wildlife, or being present at non-human births were risk factors for C. burnetii seropositivity. This was surprising given that the majority of QFD notifications are ruminant associated [ 15 , 16 , 32 ], and that birth products of infected animals, particularly ruminants, can potentially contain high levels of C. burnetii [ 46 , 68 ]. In this study, seropositivity was also not associated with tick bites.…”

“…Over the past decade in Australia, there has been an increased incidence in Q fever notifications with minimal known exposure to well-documented risk factors [ [3] , [14] , [15] , [16] , 26 , 39 , 50 , 66 ], and there is a growing body of evidence suggesting macropods, in particular kangaroos, represent a potential source of C. burnetii infection for humans. Coxiella burnetii has been isolated from the ticks of infected kangaroos [ 52 ], and C. burnetii DNA has been identified in kangaroos [ 10 , 17 , 53 , 61 ] and other wildlife including bandicoots [ 12 ] and their associated ticks [ 12 , 17 ].…”

Seroprevalence of Coxiella burnetii in pig‐hunting dogs from north Queensland, Australia

“…Ruminants, such as cattle, sheep and goats, remain the primary animal reservoir for the bacterium, 3, 6–8 experiencing largely subclinical infections with occasional reproductive impairment, 9, 10 including abortion, dystocia, reduced fertility and neonatal deaths 7, 9 . Indeed, contact with aborted ruminant reproductive materials and the normal products of parturition are considered high risk exposures for Q fever in humans 6, 8, 11–16 …”

Identifying scenarios and risk factors for Q fever outbreaks using qualitative analysis of expert opinion

“…The distribution of Q fever in Australia is geographically uneven with ‘hotspots’ in central Queensland and around the New South Wales‐Queensland border (>13 cases per 100,000) (Australian Technical Advisory Group on Immunisation (ATAGI), 2018). In addition to livestock, exposures to native wildlife, particularly kangaroos and wallabies, have been associated with human infection, underscoring their role in the epidemiology of Q fever in Australia (Clark et al., 2020; Clutterbuck et al., 2018; Graves & Islam, 2016). A small but notable number of reported human cases did not have animal contact or lacked known risk factors for acquisition (Clutterbuck et al., 2018; Graves & Islam, 2016; Rahaman et al., 2020; Sloan‐Gardner et al, 2017).…”