Strongyloides stercoralis in Australia

Author: Meruyert Beknazarova

Beknazarova, Meruyert, 2019 Strongyloides stercoralis in Australia, Flinders University, College of Science and Engineering

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Strongyloides stercoralis is a parasitic soil-transmitted nematode. It is estimated to infect up to 370 million people worldwide predominantly in tropical and subtropical areas. In Australia, strongyloidiasis is a major public health problem in remote Indigenous communities with up to 60% of people in some areas found to be seropositive to infection. Despite various intervention programs targeted to control strongyloidiasis in remote Australian communities, the disease has never been eradicated and remains endemic in those communities.

The overall aim of this research was to investigate the role dogs might play in transmitting strongyloidiasis, and to explore the knowledge gaps in regards to understanding the transmission, prevalence and distribution of S. stercoralis in Australia.

To do this, firstly, an extensive literature review was conducted, which demonstrated that strongyloidiasis is a disease of socioeconomic disadvantage, and improving sanitary and hygiene conditions in the communities should be the primary target in implementing disease control measures. Next, current available treatment options of strongyloidiasis were examined and found that treatment options only included administration of anthelminthic drugs. The literature review demonstrated that there are two issues associated with drug treatment, namely potential resistance development and reinfection. The research proposed a combined approach for controlling strongyloidiasis that includes targeting the parasite in the environment as well as drug treatment.

To get accurate data on the disease distribution and prevalence and to better understand the routes of transmission, there should be a surveillance system in place to record the cases across Australia. For that to happen, the disease needs to be included in the Australian National Notifiable Disease List. This research examined and assessed strongyloidiasis against 12 criteria set by the Australian Legislation and got a score fulfilling the requirements for national notification to be recommended.

Next, the research looked at the dogs’ potential to transmit strongyloidiasis to humans. Followed by the literature review, the research looked at the specific markers of S. stercoralis DNA that are used for host differentiation. So, three markers (18S rDNA SSU HVR-I and HVR-IV regions and mtDNA cox1 gene) of the DNA extracted from Australian human and dog faecal samples and one human sputum were genotyped using deep sequencing technique. The results showed that Australian dogs are infected with at least two genetically different strains of S. stercoralis, one that is zoonotic infecting dogs and humans, and the other one is dog specific. These findings confirmed that dogs present a potential reservoir for human strongyloidiasis.

And finally, throughout the research 274 dog faecal samples were collected from across 27 communities in the central and northern parts of Australia. The study looked at the zoonotic parasites in dogs, S. stercoralis and hookworm species including Ancylostoma caninum, Ancylsotoma ceylanicum, Ancylostoma braziliense and Uncinaria stenocephala. There was 21.9% (60/274) and 31.4% (86/274) prevalence of S. stercoralis and A. caninum found in dog faecal samples. The findings of this study emphasise the importance of the One Health initiative, which considers veterinary and public health interventions together. The One Health approach should be central in developing methods to eliminating S. stercoralis and hookworms in order to maintain both animal and public health.

This thesis serves to provide a better understanding of strongyloidiasis by examining the disease from an environmental health rather than clinical perspective.

Keywords: Strongyloides stercoralis, zoonotic parasites, Strongyloides stercoralis genotypes, Australia

Subject: Environmental Health thesis

Thesis type: Doctor of Philosophy
Completed: 2019
School: College of Science and Engineering
Supervisor: Kirstin Ross